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The electrical conductivity of mantle and transition zone minerals is known with reasonable precision and can be used to model the deep Earth. In olivine, small polarons (Fe3+ on an Mg-site) and magnesium vacancies govern the conductivity at oxygen fugacities of the mantle. Their relative importance varies with temperature; small polarons dominate at lower temperatures with magnesium vacancies playing a greater role at higher temperatures. The dominant conducting species at low oxygen fugacity are less well constrained. Multiple-anvil high-pressure electrical conductivity measurements of mantle and transition zone minerals (olivine, pyroxene, wadsleyite, ringwoodite, ilmenite, and perovskite) indicate that polarons also govern conductivity in these materials. Hydrogen in these minerals greatly enhances electrical conductivity but the conduction occurs by a mechanism different than that of hydrogen diffusion. Mineral physics-based mantle conductivity models constructed to fit resistivity and phase results of magnetotelluric studies offer the potential for mapping hydrogen in the mantle and other phases or species that cause high conductivity.
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DNA biosensors have gained increased attention over traditional diagnostic methods due to their fast and responsive operation and cost-effective design. The specificity of DNA biosensors relies on single-stranded oligonucleotide probes immobilized to a transduction platform. Here, we report the development of biosensors to detect the hippuricase gene (hipO) from Campylobacter jejuni using direct covalent coupling of thiol- and biotin-labeled single-stranded DNA (ssDNA) on both surface plasmon resonance (SPR) and diffraction optics technology (DOT, dotLab) transduction platforms. This is the first known report of the dotLab to detect targeted DNA. Application of 6-mercapto-1-hexanol as a spacer thiol for SPR gold surface created a self-assembled monolayer that removed unbound ssDNA and minimized non-specific detection. The detection limit of SPR sensors was shown to be 2.5nM DNA while dotLab sensors demonstrated a slightly decreased detection limit of 5.0nM (0.005μM). It was possible to reuse the SPR sensor due to the negligible changes in sensor sensitivity (∼9.7×10−7 ΔRU) and minimal damage to immobilized probes following use, whereas dotLab sensors could not be reused. Results indicated feasibility of optical biosensors for rapid and sensitive detection of the hipO gene of Campylobacter jejuni using specific ssDNA as a probe.
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We report an efficient sample preparation method (freezing) for onsite fat and meat analysis via a specially designed thermoelectric cooling and temperature-controlling system. This investigation also focused on the effect of phase change on the sensitivity and reproducibility of LIBS emission signals and plasma parameters. The plasma emissions of animal fats (lard) were recorded when the sample was frozen (−2 °C), fluid (15 °C), and in a liquid state (37 °C) with a thermoelectric cooling system. At each temperature, the plasma emissions were acquired at laser pulse energy from 50 to 300 mJ and detector gate delay (DGD) from 0.5 to 5 μs. With increasing sample temperature, the DGD, where the optical emission intensity reached a maximum, decreased. At a laser pulse energy of 200 mJ and a sample temperature of −2 °C, the emission signals increased fourfold, the signal-to-noise ratio (SNR) improved tenfold, and the self-absorption in the emission lines decreased significantly. The repeatability of the emission signals and plasma parameters of frozen and liquid fat samples was determined using the relative standard deviation (RSD) of Se I (473.08 nm) and K I (766.48 nm) emission lines. The RSDs of the emission signals improved from 40 to 18 % and 37 to 16 %, whereas the shot-to-shot RSDs of the electron temperature and electron number density get improved from 11 to 6 % and 12 to 6.8 %, respectively.
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Since, the majority of the Algerian desert area enjoys plenty of sun and abundance of huge underground water sources, the stand alone photovoltaic pumping system (PVPS) is an appropriate solution to supply water for domestic, livestock and irrigation in remote locations. In this view, a comparison study has been carried out upon experimental results of two submersible DC pumps, namely: Water Max A64 (300W) and Shurflo (130W). The purpose is to select an optimum direct coupling Photovoltaic Pumping System (PVPS) configuration suitable to provide the maximum daily average quantity of water to satisfy the need of a remote farms consumption, situated in Hassi-Gara region, about 110km south of Ghardaia, where the borehole and well heads vary from 10 m until 40 m. Photovoltaic (PV) powered by different selected PV arrays, based on PV Isofoton (110/24) modules, the two mentioned DC pumps were put into tests for different heads, at our PV pumping test facility, under winter outdoor conditions of Ghardaia site. Through the study and the interpretation of the obtained performances data, including the daily cumulative water and the overall efficiency of each selected (PVPS) configuration, two different direct coupling (PVPS) configurations have been selected to be eventually installed: The first (PVPS) configuration consists of the Water Max A64 (300W) submersible DC pump, PV powered by the PV array which consists of (2 X 2) Isofoton PV modules, is suitable to meet the need of an average daily water volume ranges from 6 m3 until 8 m3, however the second (PVPS) configuration which comprises the Shurflo (130W) submersible DC pump, PV powered by the (2 x 1) Isofoton (110/24) PV modules can meet the need of the medium average daily water discharge less than 4 m3. The daily pumped volume of water is selected for a period of 8hours of pumping and can be extended by extending the daily pumping hour's period during the long daylight hours; moreover, the large tanks are necessaries to preserve enough water to be used during cloudy days.
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Indium-free and acid-resistant anatase Nb-doped TiO2 (NTO) electrodes are promising as economical substitutes for high-cost Sn-doped In2O3 (ITO) films used in organic photovoltaics. By rapid-thermal annealing under an ambient vacuum, an insulating amorphous NTO film of low transparency was changed dramatically into a transparent and conductive anatase NTO electrode. Metallic conductivity of the annealed NTO electrode could be attributed to formation of the anatase phase and activation of the Nb dopant. Based on synchrotron X-ray scattering and high-resolution transmission electron microscopy, the electrical properties of the NTO electrode could be correlated with the microstructure of the NTO film. The acid-stability of NTO film also supports its use as a substitute for ITO electrode. Unlike Ga:ZnO and Al:ZnO films, which were easily etched by acidic PEDOT:PSS solution, the NTO film was stable against this reagent. Importantly, the annealing temperature influenced the performance of the organic solar cell fabricated with the NTO electrode. This indicates that activation of Nb dopants and formation of the anatase phase play an important role in the extraction of carrier from the organic layer to the anode electrode.
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The capability to functionalize the interior channels and/or high internal surface areas of mesostructured inorganic–organic or porous inorganic solids with specific organic or inorganic moieties has dramatically expanded the potential applications for these versatile materials in catalysis, separations, optical and opto-electronic devices, drug delivery, sensors, and energy conversion. Key to the widespread application of these materials are the various synthetic schemes that have been developed to provide control over the types of species incorporated and, more importantly, their distributions within the mesostructured hosts. Furthermore, multiple active species can often be independently incorporated and collectively optimized to yield multifunctional properties that widen application prospects. Several recent developments and examples in this rapidly growing field of materials chemistry and engineering are highlighted and discussed.
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Resistance to antimicrobial therapies poses a serious threat to health and socioeconomic development. To counter this, various strategies are often explored, including multiple barrier protection, such as high hygiene standards and a number of control measures. Currently, a lot of attention is being focused on developing smart materials and coatings. This include the delivery of antimicrobial agents in an intelligent way, i.e., only when bacteria are present. In this regard, new technologies are used to combine antimicrobials with lipids or polymers (synthetic and/or natural). Biopolymers are ideal materials for making smart surfaces due to their abundance, renewability, cost-effectiveness, biocompatibility, and biodegradability. With the advancement in the field of nanotechnology, various smart bioactive nanomaterials are being fabricated with high microbicidal potential and have emerged as promising strategies to prevent and treat microbial activity. In this chapter, we present a description of various nanomaterials that exhibit antimicrobial activities. These smart polymeric films may act as surfaces that not only kill bacteria but also limit their adhesion and interaction with surfaces. Further, we discuss applications and future directions of antimicrobial innovative films. This chapter provides an elaborate account of the recent advances and updated accomplishments of nanoparticle-impregnated biopolymeric films to combat microbial infection thus inspiring innovations for cutting-edge research and development in this area.
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The low potentials generated by individual thermoelectric and thermogalvanic ‘heat to electricity’ elements necessitate that numerous cells be placed electrically in series to generate useful voltages. The thermoelectrochemistry of two redox couples with opposite signs for their Seebeck coefficients have therefore been evaluated and combined, in order to generate the first thermoelectrochemical (or thermocell) assembly that is electrically in series without a hot-to-cold thermal short-circuit. This was achieved using potassium ferrocyanide(II)/ferricyanide(III) and iron(II)/iron(III) sulphate (plus sulphuric acid) thermocells. Quantitative evaluation of thermocells electrically parallel and/or in series demonstrated relatively simple additive behaviour for current and potential (and thus power density) over a very wide range of concentrations of the redox species.
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In order to characterize the electron and thermal transport properties in splat-cooled U-T alloys (T is transition metal), we measured the thermopower S and thermal conductivity κ of selected splat-cooled U-Mo alloys with 0, 11, 12.5, 15 and 17at % Mo concentrations, as a function of temperature. Additionally, we compare our data with the results of S(T) and κ (T) for pure α -U bulk material. Moreover, what particularly motivated us for undertaking above mentioned investigation was the opportunity for prove the functionality of the TTO (Thermal Transport Option) insert of PPMS apparatus for such form of samples. Working with rapidly solidified materials in the form of splats, i.e. foils of typical thickness ∼ 0.2mm, or even less, we need to test first whether the TTO output can be taken as reliable for the sample geometry, being far from typical bulk bar-shaped samples.
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Stand-alone hybrid renewable energy systems usually incur lower costs and demonstrate higher reliability than photovoltaic (PV) or wind systems. The most usual systems are PV–Wind–Battery and PV–Diesel–Battery. Energy storage is usually in batteries (normally of the lead-acid type). Another possible storage alternative, such as hydrogen, is not currently economically viable, given the high cost of the electrolyzers and fuel cells and the low efficiency in the electricity–hydrogen–electricity conversion. When the design of these systems is carried out, it is usually done resolve an optimization problem in which the Net Present Cost (NPC) is minimized or, in some cases, in relation to the Levelized Cost of Energy (LCE). The correct resolution of this optimization problem is a complex task because of the high number of variables and the non-linearity in the performance of some of the system components. This paper revises the simulation and optimization techniques, as well as the tools existing that are needed to simulate and design stand-alone hybrid systems for the generation of electricity.
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Novel hyperbranched polythiophenes containing unsymmetrically substituted thiophene units have been synthesized. These materials are designed to have conjugation gradient in their structure and be capable of light harvesting. Study of their optical properties shows a broad-band absorption, strong fluorescence, and an effective intramolecular energy transfer. They are potentially useful for the preparation of efficient photovoltaic as well as light-emitting devices.
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The present work reports the facile and cost-effective synthesis of rod like structured nickel doped bismuth sulphide (Ni-Bi2S3) via the ultrasonication process. The sonochemical synthesis technique is rapid, simple, non-explosive, and harmless than other conventional synthesis technique. After the synthesis, the resultant material was characterized through the various spectrophotometric techniques including FESEM, EDX, XRD, XPS and EIS. After the structural evaluation, as-synthesized Ni-Bi2S3 was applied for the electrocatalytic detection of promethazine hydrochloride (PMTZ) using CV and amperometry (i-t) techniques. Captivatingly, excellent electrocatalytic performance with the wider linear range from 1 nM to 163.17 µM was obtained for the electrochemical determination of PMTZ. The limit of detection (LOD) and sensitivity calculated around 0.4 nM and 2.904 μA µM−1 cm−2, respectively. Besides, an excellent selectivity, satisfactory reproducibility and good stability of the Ni-Bi2S3 modified electrode were checked towards the electrochemical determination of PMTZ. Furthermore, the real time application of PMTZ sensor was established in human serum and urine samples.
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Using bulk crystals of CuInSe2 (CIS) grown in an evacuated sealed quartz ampoule, diffusion of zinc in the temperature range (550–700°C) was investigated. The computation of the parameters showed a coefficient of diffusion D Zn varying from 10−11 to 10−10 cm2 s−1 and an energy of activation of 0.41eV. The results of optical analysis made on doped CuInSe2 showed that Zn can act as a donor and the energy E A of the acceptor level was found 23meV.
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A kinetic analysis has been made of the interaction of α-Hb chains with a mutant α-hemoglobin stabilizing protein, AHSPV56G, which is the first case of an AHSP mutation associated with clinical symptoms of mild thalassemia syndrome. The chaperone AHSP is thought to protect nascent α chains until final binding to the partner β-Hb. Rather than protecting α chains, the mutant chaperone is partially unfolded but recovers its secondary structure via interaction with α-Hb. For both AHSPWT and AHSPV56G, the binding to α-Hb is quite rapid relative to the α-β reaction, as expected because the chaperone binding must be quite competitive to complete the α chain folding process before α-Hb binds irreversibly to β-Hb. The main kinetic difference is a dissociation rate of AHSPV56G·α-Hb some four times faster relative to AHSP·α-Hb. Considering a role of protein folding, the AHSPV56G apparently does not bind long enough (0.5 s versus 2 s for the WT) to complete the structural modifications. The overall replacement reaction (AHSP·α-Hb + β-Hb → AHSP + αβ) can be quite long, especially if there is an excess of AHSP relative to β-Hb monomers.
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Benefiting from molten salts as reaction media, molten salt synthesis (MSS) offers advantages such as control of local reaction conditions to tailor material characteristics, the production of uniform and homogeneous crystallites, as well as reduced energy consumption and emissions. In this study, we successfully synthesized regular polyhedral La-substituted CaTiO3 with an orthorhombic perovskite structure under molten salt conditions, utilizing a NaCl–KCl eutectic mixture at 1073 K for 6 h. The phase compositions of the prepared samples were determined through powder X-ray diffraction (XRD), and their morphologies were characterized via scanning electron microscopy (SEM). Our investigation of the thermoelectric properties reveals that the substitution of La3+ ions significantly enhances electrical conductivity and simultaneously introducing defects that substantially reduce lattice thermal conductivity. We achieved a maximum thermoelectric figure of merit (ZT) of approximately 0.27 at about 1200 K for the sample with a nominal composition of Ca0.8La0.2TiO3. This study is intended as a reference to experimentalists working in MSS for synthesizing CaTiO3-based ceramics and discloses the transport properties of La-doped CaTiO3-based ceramics.
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Photovoltaic (PV) has recently undergone impressive growth and substantial cost decreases. A single-crystal silicon (mono-Si) or polycrystalline (poly-Si) have been dominant for solar rooftop and in commercial buildings installation in the past years. However until recently thin-film PV modules both amorphous silicon (a-Si) and other non-silicon thin films technology have been advance efficiency developments with low cost. The competition of crystalline and thin film solar panel technologies drives the cost significantly decreased and helps the solar investors for a good financial profit return for a shorter time. This study by satellite-derived data, Solar GIS pvPlanner software shows that the highest output is in a-Si, CdTe and followed by CIS, and c-Si PV modules for the locations considered in this study. The average energy output of amorphous panels in residential solar rooftop installed in Bangkok has the highest values of 1,503 kWh/kWp. The average energy output of amorphous panels in commercial building installed in Chonburi province has the highest values of 1,601 kWh/kWp. The optimal inclination angle is 15° south direction in both areas. Finally, the economic assessment of solar panels is also investigated for the feasibility investment by RETscreen model.
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Germanium antimony tellurium (GeSbTe) thin film has been deposited by the RF magnetron sputtering from the initial material target of the 1:1:1 atomic ratio. The GeSbTe thin film was annealed by furnace at 473K, 523K, 573K and 623K samples for 1h under ultra-high vacuum. The samples were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to study their structure and chemical composition. The carrier concentration, charge mobility, electrical, Seebeck coefficient and power factor are reported. The as-deposited thin film showed amorphous and consequently cubic structure (c-GeSbTe) after annealing treatments. In addition, the film thickness was rapidly decreased with increasing annealing temperature. The as-deposited thin film had the atomic ratio of 1:0.6:0.7, and after annealing treatments became 1:0.9:0.9. The c-GeSbTe thin film annealed at 523K showed the highest mobility, lowest electrical resistivity, and the highest power factor of 8.31cm2 V−1 s−1, 3.25×10−5 Ωm, and 0.81×10−4 Wm−1 K−2, respectively.
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We investigated an inverted organic photovoltaic device structure in which a densely packed ~100nm thin TiO2 layer on fluorine doped conducting glass serves as anode and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/Au layer on top of the active layer serves as cathode. The active layer is comprised of a blend of poly(3-hexylthiopene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The rectification behavior of such a device is improved significantly and injection losses are minimized compared to devices without any compact TiO2 layer. Moreover, nanostructured P3HT active layer was achieved in-situ by spin coating concentrated pure P3HT and P3HT:PCBM blend and solar cell performances on thickness of the active layer were also investigated. For the inverted solar cells constructed with different concentrations of P3HT and PCBM keeping the P3HT:PCBM ratio 1:0.8 (wt.%), the highest short circuit current and efficiency was observed when the P3HT and PCBM concentration was equal to 1.5 (wt.%) and 1.2 (wt.%) respectively. This leads to highly stable and reproducible power conversion efficiency above 3.7% at 100mW/cm2 light intensity under AM 1.5 conditions.
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As part of the Pacific '93 Oxidant Study that took place in the summer in the Lower Fraser Valley of British Columbia, we conducted measurements of isoprene, and its oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) at a surface site about 40 km east of the city of Vancouver. Hourly measurements were conducted between 16 July and 10 August 1993. The data indicated evidence for substantial contributions of isoprene chemistry to the production of ozone during oxidant episodes in this region. Maximum concentrations of isoprene, MVK, and MACR were 5.3, 2.0, and 1.0 ppb, resp., for 4 August. Analysis of the relationship between MVK and 03 during the oxidant episode period l–6 August led to an estimated contribution of isoprene chemistry of ozone production of ⩾ 13%. The average measured ratio of MVK/MACR was about 1.9–2.0 in the daytime, compared to the published relative yield of 1.4. Comparison of the MVK and MACR measurements to those of organic nitrates led to the conclusion that there is a significant non-photochemical source of MVK and MACR in this urban area.
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Electronic, thermodynamic, transport, and thermoelectric properties of pristine graphene (C8) and graphene doped with dual nitrogen (N) atoms in three different configurations were theoretically studied. All three configurations display a direct band gap and are n-type semiconductors. Notably, at room temperature, N3-doped graphene has a greater Seebeck coefficient (S) than C8, although N1 and N2 have lower S values. Furthermore, the power factor (PF) for all three structures rapidly increases, especially at high temperatures, with C8's PF decreasing at 300 K. For N1, N2, and N3, the electronic thermal conductivity ( κ e ) follows the Wiedemann-Franz rule, increasing with increasing temperature. Due to N defect-induced heat transfer scattering, lattice thermal conductivity ( κ L ) diminishes exponentially with temperature. The figure of merit (ZT) for N3 doping peaks at 550 K, outperforming N1 and N2 by a large margin (103-106 times) and then drops at higher temperatures due to electronic thermal conductivity impacts.
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Photovoltaic (PV) applications, gaining worldwide interest during the last years, comprise a promising renewable energy based solution, able to considerably contribute to the constantly increasing energy demand of our planet. Currently, residential applications possess a considerable share of the global PV market since fiscal and practical incentives have reinforced their promotion. On the other hand, high population concentration, rapid industrialisation and economic development of urban areas all over the world have caused significant degradation of the urban air quality. In this context, the actual performance of five identical pairs of roof-top PV-panels, operating in the aggravated urban environment of Athens (from the atmospheric air pollution point of view), is currently evaluated. For this purpose, a series of systematic experimental measurements is conducted within a certain time period and the influence of different dust deposition densities on the energy yield and the economic performance of the small power station is estimated. According to the results obtained, the presence of dust considerably affects the PV-panels’ performance since even a relatively small dust deposition density (≈1g/m2) may result in remarkable energy losses corresponding almost to 40 €/kWp on an annual basis.
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We have detected voltages between ohmic electrodes on Si wafers when a cleavage occurs at one of the contacts. Samples were measured at room temperature (RT) in air and under liquid nitrogen. The detected signals are positive for p-type and negative for n-type samples, show a temporal decay profile consistent with cooling, and are consistent with cleavage heat generation causing a thermoelectric effect. The signals peak after the system response time of 0.1 ms, are of average magnitude 59 μV at RT, and at 78 K are 103 μV, consistent with the increased thermopower at low temperatures. The data, considering the large cooling by the bulk and metallic contact, indicate that significant elevated temperatures occur at the cleavage surface. This can affect surface structures and properties.
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Polycrystalline silicon (poly-Si) thin-films have the potential to overcome the limits of today's silicon thin-film solar cell technology because of the chance to grow high-quality material by low-cost deposition techniques. As poly-Si thin-film fabrication is independent of rather slow and costly PECVD processes, it is possible to switch to physical high-rate deposition methods such as electron-beam (e-beam) evaporation exhibiting a strong cost-saving potential. In this contribution, the challenges and opportunities of two different poly-Si solar cell preparation techniques using e-beam evaporated silicon are investigated: Thermal solid phase crystallization (SPC) of initially amorphous silicon layers, and direct growth of poly-Si films at elevated temperatures >500°C. For both approaches, attention is given to the interplay between substrate texture, structure of the grown silicon and the final solar cell performance. Poly-Si thin film solar cells with 7.8% conversion efficiency were prepared on a smooth substrate in cooperation with CSG solar, demonstrating the equality of e-beam evaporation as deposition technique compared to PECVD. However since e-beam evaporation leads to a non-conformal deposition of rough surfaces, the implementation of a textured substrate for light trapping is highly desired but still challenging. A different behavior is observed for poly-Si thin films directly grown at higher temperatures. For the best photovoltaic performance, a certain substrate microstructure is even necessary and can be optimized by the use of glass coated by differently textured ZnO films as substrate.
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The sports facilities are characterized by special energy needs different from any other user and they are characterized by high heat and electricity loads. For this reason, the aim of this work has been to propose a tool to provide a preliminary estimation of the power and energy required by the sports centres. In addition, the possibility to make the building self-energy sufficient has been considered, thanks to the exploitation of renewable energy sources (RES). The overall work has been performed following three steps: energy needs analysis; local RES availability analysis; energy balance of Sport Centres. Considering that each sport facility is characterized by different energy needs depending on the sport typology itself, the analysis started from the features established by the CONI (National Italian Olympic Committee) standardization. For calculations a program in LabVIEW has been developed to evaluate the energy requirements of the sports centre considering as inputs the sport halls, the playgrounds and the supporting rooms, the level of the sport activity (e.g. agonistic) and the climatic conditions of the area where the facilities are located. The locally available RES are evaluated in order to decide which one can be exploited to feed the Sport Centre. The proposed solution for the energy production refers to a combination of different and innovative technologies which involve, in particular, hydrogen technologies. The energy and costs analysis has been finally carried out for an application case in Dubai.
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Three conjugated copolymers containing thiadiazolo[3,4-c]pyridine as electron- withdrawing unit were synthesized. The introduction of thiadiazolo[3,4-c]pyridine led to enhanced π–π stacking of the polymer in film and an unexpected non-ohmic contact on the interface of the polymer and hole extraction layer. PBDTT-T-DTPyT exhibited a high hole mobility of 1.2×10−2 cm2 V−1 S−1.
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We have fabricated polymer solar cell devices based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and incorporating one-dimensional nanostructured acid-doped polyaniline nanotubes (a-PANINs) as an interfacial layer. The power conversion efficiency of an annealed device incorporating the a-PANIN layer reached 4.26% under AM 1.5G (100mW/cm2) illumination, an increase of ca. 26% relative to that of the annealed device lacking an a-PANIN interfacial layer. The incorporation of the a-PANINs in the solution-processed polymer solar cells was reproducible; the high conductivity, controlled tubular nanoscale morphologies, and mobility of the annealed a-PANIN layer led to efficient extraction of photogenerated holes to the buffer layer and suppression of exciton recombination, thereby improving the photovoltaic performance.
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Thin film coating technology has leveraged different characteristics of an element deposited on a substrate by altering or improving its performance. The improvements in transparency, scratch-resistant, conductivity of electricity, transmission of signals, durability, which are typical in applications such as optoelectronics. Cadmium telluride is the most common photovoltaic material used in the market. Considering improved efficiency, Cadmium Zinc Telluride (CdZnTe) thin films are the materials of choice for several critical applications including radiation detector, solar cell, electro-optic modulators, etc., CdZnTe is a ternary alloy semiconductor solid solution of the II-IV compounds that has attracted researchers due to the wide tunability of its characteristics that include direct optimal band gap, high electro-optic coefficient and transparency in mid-infrared region. Depending on the applications, in recent times, CdZnTe films are obtained by evaporation, deposition, chemical synthesis, etc., for properties including, high resistivity, current-voltage characteristics, good mobility, long term sustainability, homogeneity and crystalline perfection. These are heavily dependent upon the crystal growth, synthesis methods, fabrication steps and purity of source raw material. This review presents a summary of CdZnTe thin films deposited by two-source thermal evaporation technique and subsequently the characteristics exhibited by such films.
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The integration between biofuels and chemicals production from biomass stimulates the transition to the inevitable bioeconomy era; this era can be achieved by implementing new technologies in existing industrial units where waste streams and by-products can be used as a renewable source of raw materials for the production of commodities and other value-added chemicals. This synergistic approach requires less capital investment, creates new business and job opportunities, expands the market and reduces the environmental impact caused by the operation of industrial plants. This chapter depicts the current situation of the two main biofuels in Brazil, ethanol and biodiesel, and introduces the discussion of opportunities and bottlenecks in the exploitation of lignocellulosic and oleaginous materials, focusing on the important role of enzymatic and microbial processes to support a sustainable industry.
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Thermodynamic quantities (including Debye temperature and frequency, atomic mean-square displacement, specific heats at constant volume and constant pressure, linear thermal expansion coefficient, and total entropy) of face-centered cubic ytterbium metal have been studied by means of the statistical moment method in statistical mechanics. This theoretical approach allows us to calculate these thermodynamic quantities taking into account the anharmonicity of lattice vibrations. Numerical calculations for ytterbium have been conducted in temperature range from 0 K to 1100 K using Lennard-Jones potential to describe the interaction between ytterbium atoms. Our derived results are compared with those of mean-field potential approach as well as previous experimental data showing the good agreement. We have shown that the atomic mean-square displacement contains the zero-point vibration (quantum effect) at low temperature. At high temperature it changes linearly with respect to temperature. Furthermore, our theoretical calculations have also pointed out the anharmonic contribution to specific heat at constant volume of ytterbium metal is negative with temperature. This research presents an effective statistical approach to study temperature effects on thermodynamic quantities of materials.
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This paper studies the impact of large-scale photovoltaic (PV) generation, up to 50% penetration level, on distribution system voltage regulation and voltage stability. The system voltage profiles are computed using power-flow calculations with load variation of a 24-h time scale. The steady-state voltage stability is examined at different times of the day using a developed continuation power-flow method with demand as continuation parameter and up to the maximum loading conditions. The load-flow analysis, implemented for both voltage regulation and voltage stability analysis, is performed by using the forward/backward sweep method. The secant predictor technique is developed for predicting the node voltages which are then corrected using the load flow solver. Three models of the PV interface inverter are implemented in this study with full set of data representing environmental conditions. The voltage profiles are regulated using the PV interface inverters, where the available inverter capacity is utilized for regulating the system node voltages. The most possible scenarios of system voltage collapse are investigated at different times of the study period. The developed methods and models are used to assess the performance of a 33-bus radial distribution feeder which operates with a high level of PV penetration. The results show that the PV interface inverters operate for reactive power support in distribution system resulting in improved voltage profile, secure power systems operation, and increasing the lifetime of the online tap changing transformers due to minimizing the total number of switching operations.
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A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO2 and H2 at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H2, CO2 and Ar and minimum adsorption of gases such as N2, O2, CO and H2O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO2 and H2 were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2mL H2 containing 10μL of each Ar or CO2 was 2.5% for Ar, 2.8% for CO2 and 3.6% for H2. The interfering effects of CO, and O2 were investigated. Working ranges were evaluated as 40–600ppm for Ar, 30–850ppm for CO2 and 10–1200ppm for H2. Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO2 in air sample.
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The flash evaporation method was used to fabricate high-performance p- and n-type Bi2Te3-based thermoelectric (TE) thin films. Optimized technological conditions of film preparation, as well as subsequent annealing, give the possibility to achieve a significant improvement in the TE properties of the designed TE films, which are state-of-the-art compared with bulk materials. Furthermore, a brand-new sandwich-layered design of the flexible film thermoelectric microconverter (FTEM) is offered here through the use of perforation cuts between p- and n-legs and a flexible polyimide substrate. Such a unique design makes it possible to avoid a rise in electrical resistance due to an increase in the number of elements in the microconverter. The dimensionless effective figure of merit ZT ≈0.6 (including losses due to parasite heat flux along with the substrate, radiation, and conversion) and TE efficiency ηmax ≈3.4% were achieved for the FTEM prototype at the temperature difference ΔT of 100 K (T c = 300 K). Therefore, the use of flash evaporation technology offers the possibility to produce large-scale film TE devices with high efficiency. Moreover, the applicability of the developed FTEM is demonstrated for a thermal detector with a high output voltage, which is used to determine a weak heat flux up to ~10−7 W.
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In this paper, a novel phase change material (PCM) based Thermoelectric (TE) food storage refrigerator incorporating an integrated solar-powered energy source is introduced. The novelty aspects of this research lie in the unique combination of PCM with solar energy, not only to maintain temperatures below 5 °C, vital for reducing food spoilage, but also in designing extra experiments using water as a cooling method to enhance system performance. Designed to preserve a diverse range of fruits and vegetables with different moisture content below 5 °C, the system innovatively employs PCM to extend cooling time, reduce energy load, and avoid conventional refrigerants, contributing to environmental sustainability. Experimentally, the average time for PCM solidification was around 3.5 h, with a corresponding latent heat release time, maintaining a temperature range of 0 to 5 °C. The system effectively accommodated various food items with water content levels from 50 % to 99 %, achieving the target temperature within around 2 to 4 h and demonstrating a promising coefficient of performance (COP) of 0.69. A standout innovation included the utilization of water flow through copper piping to accelerate heat removal from TEC, enhancing the performance of the system and reducing the solidification time of PCM by approximately an hour. This research represents a significant advancement in refrigeration technology, highlighting the feasibility and optimization potential of integrating solar energy and PCM, and introduces a new direction for enhancing efficiency through water-cooled heat sinks.
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The maximum temperature difference, which is corresponding to the optimal current, is important for evaluating the performance of thermoelectric coolers (TECs). As a representative of the thermoelectric leg with non-constant cross-section, the pyramidal thermoelectric leg has more advantages than the traditional cuboidal thermoelectric leg due to the large temperature gradient. However, the fabrication is much complex. In this work, a new shaped thermoelectric leg for TECs with almost the same property with the pyramidal legs is proposed and a simple practical approach for fabrication by taking one-side cut from the cuboidal leg is presented. Optimal current improvement is demonstrated by the theoretical calculation and the finite element simulation as well as the test results.
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In this paper, two control strategies involving “continuous” and “ON/OFF” operation of the diesel generator in the solar photovoltaic–diesel–battery hybrid systems are modeled. The main purpose of these developed models is to minimize the hybrid system's operation cost while finding the optimal power flow considering the intermittent solar resource, the battery state of charge and the fluctuating load demand. The non-linearity of the load demand, the non-linearity of the diesel generator fuel consumption curve as well as the battery operation limits have been considered in the development of the models. The simulations have been performed using “fmincon” for the continuous operation and “intlinprog” for the ON/OFF operation strategy implemented in Matlab. These models have been applied to two test examples; the simulation results are analyzed and compared to the case where the diesel generator is used alone to supply the given load demand. The results show that using the developed photovoltaic–diesel–battery optimal operation control models, significant fuel saving can be achieved compared to the case where the diesel is used alone to supply the same load requirements.
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The literature on vibrational thermodynamics of materials is reviewed. The emphasis is on metals and alloys, especially on the progress over the last decade in understanding differences in the vibrational entropy of different alloy phases and phase transformations. Some results on carbides, nitrides, oxides, hydrides and lithium-storage materials are also covered. Principles of harmonic phonons in alloys are organized into thermodynamic models for unmixing and ordering transformations on an Ising lattice, and extended for non-harmonic potentials. Owing to the high accuracy required for the phonon frequencies, quantitative predictions of vibrational entropy with analytical models prove elusive. Accurate tools for such calculations or measurements were challenging for many years, but are more accessible today. Ab initio methods for calculating phonons in solids are summarized. The experimental techniques of calorimetry, inelastic neutron scattering, and inelastic X-ray scattering are explained with enough detail to show the issues of using these methods for investigations of vibrational thermodynamics. The explanations extend to methods of data analysis that affect the accuracy of thermodynamic information. It is sometimes possible to identify the structural and chemical origins of the differences in vibrational entropy of materials, and the number of these assessments is growing. There has been considerable progress in our understanding of the vibrational entropy of mixing in solid solutions, compound formation from pure elements, chemical unmixing of alloys, order–disorder transformations, and martensitic transformations. Systematic trends are available for some of these phase transformations, although more examples are needed, and many results are less reliable at high temperatures. Nanostructures in materials can alter sufficiently the vibrational dynamics to affect thermodynamic stability. Internal stresses in polycrystals of anisotropic materials also contribute to the heat capacity. Lanthanides and actinides show a complex interplay of vibrational, electronic, and magnetic entropy, even at low temperatures. A “quasiharmonic model” is often used to extend the systematics of harmonic phonons to high temperatures by accounting for the effects of thermal expansion against a bulk modulus. Non-harmonic effects beyond the quasiharmonic approximation originate from the interactions of thermally-excited phonons with other phonons, or with the interactions of phonons with electronic excitations. In the classical high temperature limit, the adiabatic electron–phonon coupling can have a surprisingly large effect in metals when temperature causes significant changes in the electron density near the Fermi level. There are useful similarities in how temperature, pressure, and composition alter the conduction electron screening and the interatomic force constants. Phonon–phonon “anharmonic” interactions arise from those non-harmonic parts of the interatomic potential that cannot be accounted for by the quasiharmonic model. Anharmonic shifts in phonon frequency with temperature can be substantial, but trends are not well understood. Anharmonic phonon damping does show systematic trends, however, at least for fcc metals. Trends of vibrational entropy are often justified with atomic properties such as atomic size, electronegativity, electron-to-atom ratio, and mass. Since vibrational entropy originates at the level of electrons in solids, such rules of thumb prove no better than similar rules devised for trends in bonding and structure, and tend to be worse. Fortunately, the required tools for accurate experimental investigations of vibrational entropy have improved dramatically over the past few years, and the required ab initio methods have become more accessible. Steady progress is expected for understanding the phenomena reviewed here, as investigations are performed with the new tools of experiment and theory, sometimes in integrated ways.
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Successful development of renewable energy technologies like solar photovoltaic energy (SPV) critically relies on its understanding and acceptance by consumers and institutional customers. Even in contexts of favorable support at the general level like in Brazil, their implementation faces multiple challenges, including low awareness, misperceptions, insufficient communication, and eco-labels' mixed record as information enhancing tools. This paper discusses how market research has been instrumental in developing the first SPV venture in Brazil, by identifying public's beliefs and level of support for alternative energies, and by testing reactions to a solar energy eco-label scheme proposed as key communication tool. The study indicates that expectations for return on investment are affected by a sustainability penalty, as well as by price and adaptation barriers. It also reveals an assessment gap between the concept and design of eco-label, which led to a new eco-label design capable of better addressing unfavorable beliefs, integrating expectations, and improving overall acceptance.
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We report on the electrical and optical characteristics of a-Si:H/c-Si heterojunction solar cells with point-contact junction via patterned SiO2 layer at the interface. The new structure showed improved electrical properties, having a smaller leakage current and a larger shunt resistance. The electrical conduction of the point-contacted samples followed the diffusion dominant process with bulk recombination, but the control samples without SiO2 showed the space-charge region recombination dominant process. The point-contacted samples showed increased internal quantum efficiency in the bulk region, but decreased internal quantum efficiency in the surface region. As the distance between the holes decreased, the point-contacted solar cells showed an improved efficiency with a larger fill-factor but smaller open-circuit voltage and short-circuit current.
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Cu2SnSe3 nanocrystals was successfully synthesized by a “hot-injection” protocol in the presence of oleylamine (OLA). The as-synthesized nanocrystals were single phase crystalline, cubic crystal structure, and high monodispersity with an average diameter of 5nm. The thermoelectric properties of these dense materials compacted from nanocrystals with the temperature range from 300K to 598K exhibit a high figure-of-merit ZT at 598K.
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New dithienogermole-based conjugated polymers were synthesized by the Stille coupling reactions of distannyldithienogermole and dibromoarene, and their photovoltaic properties were studied. These polymers possess low band gaps with broad absorptions covering the 400–800 nm range, and exhibit good film forming properties. Bulk hetero-junction solar cells prepared from blends of these polymers with PC70BM exhibit high power conversion efficiency up to 2.38%.
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To address the challenge of the growing global energy crisis and the greenhouse effect, employing the thermoradiative effect of photodiodes to harvest radiative energy from colder outer space is considered a promising approach for direct nighttime renewable energy generation. By considering the coupled effect of the atmosphere, ambient, and non-radiative losses, a thermodynamic model of nighttime thermoradiative diodes (NTRDs) is developed. The fundamental performance limit for the achievable electric power density and device optimal designs of NTRDs are theoretically investigated based on Shockley-Queisser analysis. The modeling predicts that an ideal (nonideal) optimized NTRD can generate a maximum power density of 1.5 (0.12) mW/cm2 when operated at room temperature with an external luminescent efficiency of 100% (10%). The calculated results indicate that the maximal electric power generation of NTRDs is strongly influenced by the semiconductor bandgap and the external luminescent efficiency of the diode, as well as the ambient temperature and humidity. This work offers insights for optimal device designs of NTRDs, thus paving the way toward designing high-performance nighttime thermoradiative power generation systems.
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We present a short summary of experimental and theoretical studies on the isostructural intermetallics Ce5CuM3 (M=Sn, Pb and Bi), crystallizing in the hexagonal Hf5CuSn3-type structure (space group P63/mcm). The investigated compounds are found to undergo multiple magnetic phase transitions at low temperatures. We discuss the role of f-spd hybridization on the evolution of heavy-fermion state across the series of the studied compounds. The band structure calculations not only support magnetic ground state of the studied compounds but also suggest an inequivalent contribution of Ce atoms at different positions to the density of states.
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A new class of organometallic/inorganic hybrid Langmuir–Blodgett (LB) films, consisting of rigid-rod alkynylplatinum(II)–zinc(II) porphyrinate complex (OMA) as the π-conjugated donor–acceptor-type molecule and tungsto(molybdo)phosphoric heteropolyacids (HPA) (HPA = H3PMo12O40 and H3PW12O40, abbreviated as HPMo12 and HPW12, respectively) of the Keggin structure as the inorganic component, were prepared and characterized by π–A isotherms, UV–vis absorption and luminescence spectra, low-angle X-ray diffraction, scanning tunneling microscopy and surface photovoltage spectroscopy. Our experimental results indicate that stable, well-defined and well-organized Langmuir and LB films have been formed in pure water and heteropolyacid subphase. They typically have a highly organized lamellar structure in which a monolayer of HPA is most likely embedded inside the OMA molecular space formed by long chains of PBu3. Luminescence spectra of these hybrid LB films show that HPMo12 and HPW12 can enhance the emission of OMA to some extent. These LB composites show good photovoltage responses and a photovoltage of 79 μV can be obtained for the OMA/HPMo12 system when it is excited by light. The monolayer LB films on ITO wafer can also display interesting electrical conductivity.
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This paper describes a low-speed wind energy harvesting system that transfers aerodynamically induced flutter energy into electrical energy. A random airflow generates mechanical vibrations due to the fluid–structure interaction between a flexible belt and the airflow. An electromagnetic resonator with copper coils and a permanent magnet is designed to efficiently harvest electrical energy from the induced mechanical vibrations. Different groups of springs are compared at various wind conditions to maximize the power output. Typically ∼7mW of electrical energy can be obtained at ∼3m/s wind speed with a 1m long belt. A power conditioning circuit with a charge pump and a DC–DC converter is used to convert the generated voltage into a stable 3.3V DC for consumption. It is demonstrated that this generator can be used to drive a commercial wireless temperature sensor.
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This article reports on the use of ZnO films in silicon thin film p–i–n solar cells and modules. It summarizes the status in the final phase of a joint research project aiming at the development of high-quality ZnO/glass substrates feasible for an industrial solar module production. The samples were prepared by reactive mid-frequency (mf) sputtering on large area (60×100 cm2) glass sheets using low-cost metallic Zn:Al targets. These ZnO films exhibit resistivities down to 2.6×10−4 Ω cm and high optical transmittance. Variation of the sputter pressure leads to films with significantly differing etching behavior in diluted acids. ZnO layers prepared in the high pressure regime develop strongly textured light scattering surfaces after etching, which is necessary to obtain highly efficient solar cells. Initial efficiencies of small area amorphous silicon (a-Si:H) cells on texture-etched ZnO-films prepared by mf-sputtering on 60×100 cm2 soda-lime glass (3 mm thick) range from 8 to 9% (highest efficiency 9.2%, i-layer thickness 350 nm). First 0.6 m2 modules on ZnO prove the principal applicability of the films for an industrial manufacturing process.
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The design of supercapacitor materials with both high areal capacity (C) and high mass loading is vitally important for enhancing energy density (E). Herein, we prepared a NiCoOH/NiCoOOH composite film consisting of NiCoOH/NiCoOOH nanosheets on an expanded graphite paper (EGP) by using a facial anodization method. The as-prepared NiCoOH/NiCoOOH film exhibits ultra-high C of 11 mA·h·cm−2 at a mass loading of 165 mg·cm−2, high rate capability of 71% and excellent cycling stability of 95% after 12 000 cycles. The outstanding performance is ascribed to the low-crystalline feature of the NiCoOH/NiCoOOH nanosheets, and the synergistic effect of the NiCoOH and NiCoOOH phases and high conductive porous EGP. An aqueous asymmetric supercapacitor, assembled with the NiCoOH/NiCoOOH on EGP and Fe2O3 on EGP as positive- and negative-electrode, respectively, shows a highest E of 3.8 mW·h·cm−2 at a power density (P) of 4 mW·cm−2 and a maximum P of 107 mW·cm−2 at an E of 2.7 mW·h·cm−2.
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Measurements of particle size distribution was made in one location of an urban area in the period January–September/2015 in order to understand the sources and mechanisms influencing ultrafine particle (UFP) number concentrations (PNC2.5-250) using a Scanning Mobility Particle Sizer Spectrometer (SMPS). k-means cluster analysis was applied to interpret the sources, temporal and spatial trends of UFP. Eight clusters were obtained. Main PSD patterns of each cluster, mean concentration of other air pollutants tracing specific sources and processes, and that of meteorological variables, as well as the hourly and seasonal frequencies of occurrence were used to support the interpretation of their origin. Thus, clusters were attributed to traffic rush hours, midday summer new particle formation, diurnal new particle formation and growth, growth of nucleated and other urban particles, urban background, regional and urban background and regional and urban background on cold nights. Many PSDs of the clusters were dominated by nucleation mode particles: midday nucleated fresh particles, photochemically induced (NPF); diurnal nucleation episodes (NPF2); growth of nucleated particles in nocturnal aging (GNPF). Origins of the clusters were related to local/regional sources (mostly traffic and biomass burning), atmospheric processes (photochemical formation and growth) and urban/regional background. Results clearly shows that traffic is a major UFP source in nucleation mode and occurred in higher concentrations in winter (08:00 to 12:00 h) during traffic rush hours, and at night. Photochemical nucleation occurred with a relatively low frequency but yielding very high PNC.
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A new instrument for production and analysis of samples created by mass-selected ion beam deposition is described. The deposition beamline makes use of a novel phase-space compressor that improves the focusability of the beam at low energies, allowing use with low current cluster ion sources. To illustrate the method, our initial results are presented for deposition of Cu+ and Cu2 + on molybdenum over the energy range from 6 to 220 eV. It is found that deposition of Cu+ at low impact energies results in Cu depositing on the surface with sticking probability of ∼0.6. As the energy is increased above ∼100 eV, an increasing fraction of subsurface copper is observed. In the Cu/Mo system, diffusion of subplanted Cu to the surface is thermodynamically favored, and this probably accounts for the observation of no subplanted Cu at impact energies up to 100 eV. For Cu2 +, the results are quite different. The apparent deposition efficiency is similar to that observed for Cu+, however, a significant fraction of sub-surface copper is observed at energies down to ∼40 eV (20 eV/atom). This greater tendency for production of subplanted copper is tentatively rationalized as resulting from a greater propensity for dimer impact to produce complex defects that stabilize subplanted copper. Possible production mechanisms for such defects are discussed.
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Self-consistent scalar relativistic band structure calculations for AMO (A=Li, Na, K and Rb; M=Ag and Cu) compounds have been performed using the tight-binding linear muffin-tin orbital (TB-LMTO) method within the local density approximation (LDA). At ambient conditions, these compounds are found to crystallize in tetragonal KAgO-type structure with two different space group I-4m2 and I4/mmm. Nowadays, hypothetical structures are being considered to look for new functional materials. AMO compounds have stoichiometry similar to eight-electron half-Heusler materials of type I–I–VI which crystallizes in cubic (C1b) MgAgAs-type structure with space group F-43m. For all these compounds, by interchanging the positions of atoms in the hypothetical cubic structure, three phases (α, β and γ) are formed. The energy–volume relation for these compounds in tetragonal KAgO-type structure and cubic α, β and γ phases of related structure have been obtained. Under ambient conditions these compounds are more stable in tetragonal KAgO-type (I4/mmm) structure. The total energies calculated within the atomic sphere approximation (ASA) were used to determine the ground state properties such as equilibrium lattice parameters, c/a ratio, bulk modulus, cohesive energy and are compared with the available experimental results. The results of the electronic band structure calculations at ambient condition show that LiCuO and NaMO are indirect band gap semiconductors whereas KMO and RbMO are direct band gap semiconductors. At high pressure the band gap decreases and the phenomenon of band overlap metallization occur. Also these compounds undergo structural phase transition from tetragonal I-4m2 phase to cubic α-phase and transition pressures were calculated.
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This chapter focuses on number of major trends underlying the continuing effort to realize practical optoelectronic, electronic, and information-processing devices based on ensembles of quantum dots assembled in a variety of matrix materials. The great diversity of such structures has opened the possibility of numerous device applications and stimulated research underlying photoluminescent devices, light-emitting diodes, displays, photodetectors, photovoltaic devices, solar cells, and novel spin-based information-processing devices. It is expected that research underlying these applications will continue to thrive due to the enormous number of possible device embodiments possible with colloidal quantum dots and available matrix materials. The chapter reviews the applications of ensembles of colloidal quantum dots. Although colloidal quantum dots are studied since the pioneering work of Michael Faraday, it is quantum dots self-assembled during growth on a two-dimensional semiconductor surface that were initially studied over the last two decades by the international semiconductor device community.
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Polyethylene glycol (PEG) and trimethylolpropane triacrylate (TMPTA) were used as photo-crosslinkable polymer electrolytes for dye-sensitized solar cells (DSSCs). PEG and trifunctional TMPTA formed a crosslinked structure upon light illumination, as confirmed by the solubility test and FTIR spectroscopy. In order to make close contact with the TiO2 porous film, the polymeric electrolyte was prepared by photo-polymerization after injecting the monomer electrolyte solution into the porous film. The cross-sectional FE-SEM images showed the penetration of the electrolyte into the porous TiO2 layer. Under AM 1.5 (100mW/cm2) light irradiation for up to 30min, a maximum 21% increase in the photo-conversion efficiency (η%) was observed. The electrolyte containing PEG and 20wt% TMPTA showed a maximum increase in the photo-conversion efficiency from 2.75% to 3.35% with 30min of light illumination. Also, the DSSCs with the novel crosslinkable PEG/TMPTA based polymer electrolyte showed improved long-term stability in comparison to those with electrolytes containing only PEG.
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Passive personal thermal management based on radiative cooling textiles is emerging as a facile, cost-effective, and energy-efficient way for outdoor human body thermal comfort. Existing passive radiative cooling textiles are mainly built from synthetic polymers that are usually nonrenewable and non-degradable, and lack sweat management function. Herein, we report the fabrication of a biopolymer-based, nanofibrous textile that integrates passive radiative cooling and sweat transportation functions via a scalable electrospinning technique. The optimized control over the nanofibers’ diameter enables the 200 µm thick film with high reflectance in both the ultraviolet (UV) range (92%) and the entire solar spectrum (95%), and the abundant chemical bonds of silk fibroin allow a high emissivity of 95% in the atmospheric window. Consequently, the nanostructured textile can achieve a temperature of ∼3.8 °C below the ambient temperature during the daytime and ∼6.4 °C at night. More importantly, the use of hygroscopic silk fibroin offers additional functions of sweat absorption and evaporation. Outdoor sweat evaporation experiment demonstrates a temperature reduction of ∼5.5 °C for nanofibrous silk fibroin textile, compared with the traditional nonhygroscopic textile. Owing to its excellent combination of biodegradability, superior cooling ability, and high sweat transportation capacity, the scalable silk nanofabric would be an effective textile for passive personal thermal management.
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In distribution system planning with photovoltaic generations (PVGs), if load is not properly modeled in the simulation, the accuracy of results will be affected. A large number of studies show that load characteristics play a impotrant role in the system analysis. This paper presented the resultant load model, and on this basis, studied the impacts of the constant power load model and constant impedance load model on PV generation planning. Simulation results show that the selection of load models has an important impact on PV generation planning.
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This work investigates the electrodeposition of CdSe photonic nanostructures into two dimensional (2D) resist templates generated by X-ray lithography. This templated electrolytic infiltration process is particularly interesting for photonic and photovoltaic applications. Both current and voltage controlled electrochemical depositions have been performed to infiltrate CdSe onto the 2D templates. Followed by the removal of the template, triangular arrays of CdSe pillars or networks with more than 1 μm in height were obtained. The detailed studies of deposition parameters such as applied voltage, current density, deposition time, concentrations of electrolytes and temperatures were carried out to determine the optimum conditions to obtain high quality 2D CdSe photonic crystals (PhCs). The full optical and structural characterization of the CdSe nanostructures showed that the CdSe films prepared have a cubic structure with nanometer grain size. Optical absorption studies reveal a bandgap of 2.1 eV for the thin film grown CdSe, blue-shifted from the characteristic 1.7 eV of bulk CdSe, resulting from size quantization effect. Preliminary optical characterization by a micro-reflectance technique is performed in order to assess the performance of the fabricated samples as 2D PhCs.
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The use of industrial solid wastes with a high content of SiO 2 and Al 2 O 3 , called “precursors”, is often studied in the construction industry when combined with NaOH as “activator”. The precursor and activator system is generally proposed as a binder material with similar characteristics to Portland cement. In this work, we technically and environmentally evaluated such a system elaborated with an industrial waste: coal ash with caustic soda in solid state. This product, mixed with the soil, acts as a stabilizer to increase the capacity of load support, allowing the improvement of the conditions of performance in low volume traffic roads. An experimental design applied to the stabilizing product showed the incidence of different factors on the load carrying capacity response: packaging material, type of seal, baling moisture and storage humidity. The application of the stabilizer product was found to increase the resistance of the ground over a 500%. Finally, the environmental aspects were evaluated through a simplified Life Cycle Assessment methodology (LCA), the scope of the study was restricted to cradle to gate, collecting data up to the packaged stabilizing product. The results showed that the highest impacts were caused, for most impact categories, by NaOH production, and transport was relevant as well.
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We present a novel method to remove the unwanted covellite (CuS) in Cu-rich prepared CuInS2–CdS–ZnO photovoltaic cells by a combined chemical/electrochemical procedure. Our treatment results in a solid state transformation by electrochemical reduction in an alkaline electrolyte with subsequent chemical dissolution. The reduction is carried out in the potential range between −1.1 and −0.85 V vs. a saturated calomel electrode (SCE). In situ atomic force microscopy (AFM) confirms a distinct change in morphology. The chemical and electrochemical reactions leading to the dissolution are discussed. After completion of the treatment a pronounced photoeffect is observed. X-Ray diffraction (XRD) shows the complete removal of CuS.
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The objective of this paper is to compare the economics of using solar energy to operate small, multiple-effect seawater distillation systems in remote areas with the conventional method of using fossil fuels. The particular multiple-effect system used is an advanced horizontal-tube, falling-film system called “multiple-effect stack” (MES) in which the pumping energy requirement is relatively low compared with the horizontal in-line system. Three system configurations were investigated: (1) a conventional system using a steam generator to provide steam for the MES evaporator and a diesel generator to provide pumping power, (2) a solar-assisted system which uses solar thermal collectors to provide hot water (instead of steam) for the evaporator and a diesel generator for pumping power, and (3) a solar stand-alone system which uses solar thermal collectors for the evaporator heat requirement and a solar PV array to provide electrical energy for pumping. At the present time, solar energy cannot compete favorably with fossil energy, particularly under the present international market prices of crude oil. However, in many remote sunny areas of the world where the real cost of fossil energy can be very high, the use of solar energy can be an attractive alternative. Two important cost parameters affect the relative economics of solar energy vis-à-vis conventional (fossil) energy: the collector cost in dollars per square meter and the cost of diesel oil in dollars per giga Joule. Solar energy becomes more competitive as the local cost of procuring conventional fuel increases and as the collector cost decreases. The water cost from a solar thermal-diesel-MES system (configuration #2) can be seen to approach the water cost from a steam generator-diesel-MES system (configuration #1) when the collector cost drops to $200/m2 and diesel oil cost at the remote site reaches $50/GJ. Using a 100% solar system (configuration #3) with solar thermal and solar PV collectors, the economics was seen to improve in favor of the solar system. Even when diesel fuel can be procured at $10/GJ at the remote site, the cost of water from the solar system can be seen to approach that from a conventional plant when thermal collectors costing $200/m2 are used. The cost of water from the solar system was shown to be always less than that from a conventional system which uses diesel oil procured at the high price of $50/GJ, but always higher than water produced from a conventional system using diesel oil at the low price of $10/GJ.
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Highlights • UV-excited (325 nm) Raman spectra reveal leucoemeraldine form of polyaniline. • Blue line (442 nm) excited spectra are in resonance with intermediate redox form. • Green line (532 nm) excited spectra reveal all redox forms and their interconversion.
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The capacitive mixing procedure for energy extraction based on double layer expansion (CDLE) belongs to the group of so-called capmix techniques. CDLE takes advantage of the voltage rise that occurs when seawater is exchanged for river water by simply using a pair of porous electrodes that jointly behave as an electrical double layer supercapacitor. Despite being an approach that is easy to implement, there are still some experimental aspects that appear essential for optimizing the extracted energy that have not yet been analyzed in sufficient detail, for example, the value of the optimum working potential, the influence of the temperature and salinity of the solutions in the cycle performance, the porosity or hydrophilicity of the carbon, and the possibility of stacking individual cells in order to increase the amount of energy. In this chapter, we deal with all these experimental aspects in order to achieve a fruitful implementation that will help in succeeding in a future CDLE device.
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Highlights ► The modeling method for PV dc building module based BIPV system is presented. ► The coordinate control strategy for PV-DCBM based BIPV system is presented. ► The accurate small-signal model of the PV-DCBM based BIPV system is built.
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Ternary bi-metallic borides have been prepared by administrating two different solvent media utilized through co-precipitation process with particles dimension ranging from 3 to 5 nm. The X-ray photoelectron spectroscopy suggests the presence of redox states in the cobalt-nickel based bi-metallic borides that promotes excess electroactive sites. The outstanding stability of bimetallic borides has been estimated by measuring relaxation time (T2 ) in solvent medium. The surface area has been evaluated about 151.302 m2 g−1with associated pore diameter of 6.57 nm. Moreover, the ternary bi-metallic electrode exhibited excellent pseudocapacitance with exceptional specific capacitance (SC) of 4835 Fg−1 (606 mAh g−1) at 5 Ag−1 by upholding cycling retention of ∼94.2% over 15,000 cycles. Also, different concentrations of sodium hydroxide (NaOH) electrolyte (0.5, 1.0 & 1.5 M) are employed for comparative study to achieve optimal electrochemical performance. Simultaneously, an electrode configuration is designed with cobalt-nickel-boron (Co-Ni-B) 1:1:0.15 as positive and carbon black as negative electrodes to fabricate asymmetric device. The device illuminates a commercial light emitted diode (LED, ∼1.8 V) to justify the electrode performance and their full-scale deployment with a device efficiency ∼363 Fg−1 (358 mAh g−1) and an energy density of 114 Wh kg−1.
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Research highlights ▸ Verifying correct operation-energy yield and safety- of PV plants: crucial issue. ▸ We propose a checking procedure that completes the existing IEC 62446 standard. ▸ PV generator peak power, inverter response and earth electrode are also measured. ▸ This procedure was carried out in six PV plants sited in Spain. ▸ PV plants pass the safety tests but some show a noticeable drop in their peak power
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Employment of renewable energy instead of fossil fuels in the textile factory reduces the problems caused by fossil fuels. This paper conducts detailed modeling of a novel integrated textile factory and power system using geothermal energy. Energy and exergy analysis are done, and the effects of changes in critical parameters on the energy and exergy performance of the proposed system have been evaluated. In addition to find the best performance condition of the suggested system, a multi-criteria optimization is done. A creative waste heat recovery system (WHRS) is designed to recover the waste heat of the proposed cycle. Results obtained from the thermodynamic modeling are analyzed to find effects on energetic and exergetic performances of the proposed combined system with varying time. The results show that the drop in temperature of the water entering the reinjection well occurred when hot water was in demand for the textile factory. The temperature range of 90 °C –96 °C are selected as temperature intervals for using WHRS. The maximum energy efficiency is about 6.2%, which is related to the time intervals when there is no demand for hot water in the textile factory. In the first three-time intervals that the WHRS is active, the energy efficiency increases from 3.38% to 4.6% and the exergy efficiency increases from 17.59% to 21.06%. According to the multi-objective optimization of Kalina cycle in the selected optimum condition the system energy efficiency and exergy destruction rate are 9.39% and 152.36 kW.
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This chapter presents a theoretical thermal analysis performed for a photovoltaic (PV) module cooled by circulating water on the back side of a serpentine tube. The simulation was developed using the software Malhematica 3.0, able to interact by symbolic and numerical calculation. The hybrid collector increases solar energy utilization, once a great part of it is usually converted into thermal energy and not used in the usual PV system. The total area necessary to convert solar energy into electricity and heat water is also smaller than using the two different collectors separately (PV + thermal collector). Although, thermal efficiency is higher than electric one, the second kind is of great interest for man. Electricity is easily transported, sold, and converted into work, light, or even heat. The goal of hybrid option is probably the electric efficiency increasing, expected due to the reductions of cell temperature values and unhomogeneous distribution.
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Understanding how to influence ice adhesion to structures and prevent icing catastrophes is a paramount research question. Conventional industrial anti-icing methods are active, requiring an energy source. However, active strategies are energy intensive. Passive anti-icing surfaces have thus become an area of engineering interest. Such strategies, like low surface energy chemical coatings, produce highly anti-icing surfaces on a lab-scale but they have not succeeded in industrial applications. They lack efficacy over repeated icing/de-icing cycles and their materials are unsuited for harsh environments. The body feather of the sub-Antarctic Gento penguin Pygoscelis papua, which ornithologists note is perpetually free of ice despite its freezing environment, serves as a compelling source of passive anti-icing biomimetic inspiration which may overcome these aforementioned deficiencies. Through studying these feathers, it has become clear that two aspects of anti-icing (water-shedding and ice-shedding) are addressed in distinct ways by the Gentoo penguin. The water-shedding functionality of the feathers is derived from an air cushion created by the wire-like microstructure of the feather and is augmented by nano-scale grooves in the feather coated in preen oil. The preen oil is necessary to maintain water-shedding functionality, however once removed the ice-shedding functionality of the feathers is maintained. The ice-shedding functionality appears to be derived from wire-like morphology of the penguin body feather barbs and barbules which induce cracks that are easily opened at the ice-feather interface. Such a design strategy shows promise in addressing the common failings of passive systems. These anti-icing strategies were then tested on metallic biomimetic substrates. The barb structure of the penguin body feather was mimicked using ultra-fine woven stainless-steel wire cloth. Some stainless-steel wire cloths were laser machined to mimic the texturing and surface chemistry of the feathers. These cloths were indeed hydrophobic like the feathers. Both stainless-steel wire cloths had significantly reduced ice adhesion strengths compared to those of the flat monolithic stainless-steel sample. The laser-machined wire cloth had an ice adhesion strength of 63 ± 10 kPa compared to 603 ± 236 kPa for the flat sample. This both indicates that the ice-shedding capabilities of the sample are imparted by the structure and further strengthens the argument that water-shedding and ice-shedding are distinct phenomena that need to be addressed with two separate design strategies.
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The semiconductor band gap of the Cu(In,Ga)Se2 (CIGSe) compound can be varied by the In to Ga ratio. This composition variation determines the photovoltaic properties of CIGSe thin films. Their composition depth profile has to be optimized in order to obtain maximum efficiencies in solar cell applications. Synchrotron-radiation-based X-ray fluorescence (XRF) analysis under grazing incidence conditions provides non-destructive access to the compositional depth profile of the CIGSe thin films and, hence, represents a new non-destructive method, which does not require well-characterized standards for calibration purposes. Based on an analytical description of the physical processes, fluorescence line intensities of the specimen can be calculated by using fundamental atomic parameters. The general suitability of the method for determining depth gradients in CIGSe thin films is first shown by calculations. Reference-free XRF test measurements were carried out at the FCM beamline in the PTB laboratory at BESSY II. X-ray fluorescence was induced by photon excitation at energies of 4.0keV and 10.5keV, respectively, using various shallow incident angles. The calculations and the experimental measurements show that even small differences in the Ga/In profile may be distinguished, indicating that grazing incidence XRF is a promising tool for a non-destructive characterization of compositional depth profiles. Further refinement of the operational parameters may contribute to the sensitivity of the method.
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We investigated Si core approximants completely terminated with hydroxyl (OH) groups for emulating a SiO2 environment by Density Functional–Hartree–Fock (DF–HF) calculations. As approximants we chose Si10(OH)16, Si35(OH)36 and Si84(OH)64, having quantum dot (QD) diameters of d QD7.3, 11 and 14.8Å, respectively. The impact on the electronic structure was considered by exchanging two OH groups for one double-bonded oxygen (O) or one Si atom for one bridge-bonded oxygen (>O). We find that the influence of >O and O on the electronic structure of otherwise completely OH-terminated Si core approximants only alters the ground state HOMO-LUMO gap for the smallest Si cores. The impact of >O and O on the electronic structure and the optical absorption edge of Si QDs embedded in SiO2 is small and should not alter the ground state electronic behaviour of Si QDs embedded in a SiO2 matrix.
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Excess molar enthalpies, H m E , of binary mixtures containing ethylene glycols and poly(glycols)+ethyl alcohol were measured by a flow microcalorimeter at 308.15K and at atmospheric pressure over the whole composition range. Binary mixtures contain ethyl alcohol+ethylene glycol, +di(ethylene glycol), +tri(ethylene glycol), +tetra(ethylene glycol), +poly(ethylene glycol)-200, +poly(ethylene glycol)-300, +poly(ethylene glycol)-400, +poly(ethylene glycol)-600. Effects of the molecular weight distribution (MWD), of the polymer were investigated too, by preparing three additional samples of poly(ethylene glycol) with the same number average molecular weight (M n ≈300), but different MWD. For all mixtures, results were fitted to the Redlich–Kister polynomial. H m E curves are asymmetrical, showing positive values which vary from 280Jmol−1 (diethylene glycol+ethyl alcohol) to 1034Jmol−1 (mixture containing PEGs (200+400)+ethyl alcohol). Effects of changes in the glycols chain length and in MWD on the molecular interactions among the mixture components are discussed.
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Recently a novel concept of water-sorbing heat exchanger has been proposed, which can independently handle latent and sensible loads at the same time and provide a very promising high-efficient solution for temperature and humidity control. Obviously, moisture uptake behavior has great influence on heat exchanger's performance. Here, a series of experiments have been made to clarify whether the linear driving force (LDF) model could be used to describe this behavior and to investigate the water uptake mode at different times. Results show that the LDF model is valid for water-sorbing heat exchanger and the moisture uptake experiences four different modes in general, including non-isothermal adsorption, near-isothermal adsorption, capillary condensation and cooling-based condensation. This study also confirms that salts in porous matrix can accelerate moisture uptake and promote capillary condensation. These results in a great improvement of dehumidification capacity. Besides, an empirical and a semi-empirical framework were developed to evaluate the constant parameters in the LDF model. Meanwhile, a figure of merit of the desiccant, Z, was defined for engineering application, to simplify the LDF model in further.
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The mechanical, electrical and thermal properties as well as thermal expansion of Al/SiC/RHA (rice husk ash) monolayer and bilayer composite have been studied using the Taguchi method and analysis of variance (ANOVA). The parameter that most significantly affects the modulus of elasticity of Al/SiC/RHA bilayer composites is processing time, with contribution percentages of 68 and 27% calculated from stress-strain graphs and ultrasonic method, respectively. However, the factor which mostly affects bending strength, CTE value and electrical resistivity of composites is process temperature with contribution percentages of 32, 28, and 22%, respectively. The projected values for modulus of elasticity (170 GPa), bending strength (369 MPa), CTE (8.9 × 10−6/°C) and electrical resistivity (0.0019 Ω m) of Al/SiC/RHA composites are in excellent agreement with those obtained in the verification tests under the optimal conditions according to ANOVA.
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The performance of an alkali metal thermoelectric converter (AMTEC) is restricted by the generation of surplus waste heat, so utilizing waste heat is a potential way to enhance the energy exchange efficiency of AMTEC. In this work, a novel coupling system comprised of an AMTEC, thermally regenerative electrochemical cycles (TRECs) and an absorption refrigerator (AR) is proposed, in which the waste heat is spilt into two parts to drive TRECs and AR to content with the actual demand for power and cooling. Taking into account the external heat leakage as well as the principal irreversible losses in the system, the equivalent power output and efficiency of the system are expressed mathematically. Furthermore, the generic performance features are demonstrated as well as optimum operation regions of the coupling system are obtained. After optimizing the proportional coefficient of heat flow distribution and the current density of the AMTEC, the maximum power output (MPO) and maximum efficiency (ME) could reach 29.49 W and 0.35, respectively. Meanwhile, the MPO and ME of the coupling system are 45 % and 28 % larger than the separate AMTEC system, and are also significantly higher than AMTEC/TRECs and AMTEC/AR. Finally, the impacts of the critical parameters on the systemic performance are evaluated, including the temperature-independent exchange current coefficient, the internal resistance, the regenerative efficiency and the heat-transfer coefficients. The present study may provide a new route for AMTEC to improve the conversion efficiency.
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The resistivities for carbon nanotube networks and highly conducting polymers show similar behaviour, which we ascribe to metallic conduction interrupted by barriers, but the thermopower of the two types of material is very different. The almost linear temperature dependence of the thermopower of highly conducting polymers indicates that the electron–phonon interaction is too small to produce significant superconductivity. For carbon nanotubes, we identify systematic nonlinearities in the thermopower data and compare them with calculations of thermopower due to sharp peaks in the density of states and to low-temperature enhancement effects.
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Cu1.8Se1−x S x (0 ≤ x ≤ 1) thermoelectric alloys were prepared by mechanical alloying (MA) combined with spark plasma sintering (SPS) technology. The phase structure and morphologies of all the samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The electrical conductivity, Seebeck coefficient, thermal conductivity were investigated for all the Cu1.8Se1−x S x alloys with a special emphasis on the influence of the S doping. With the increasing of S contents, a phase transition of Cu1.8Se1−x S x was occurred from cubic to hexagonal. The electrical and thermal transport properties of the samples changed accordingly. The Cu1.8Se0.7S0.3 alloy achieves the highest ZT of 0.78 at 773 K due to both optimized electrical transport properties and thermal transport properties, which is 44% higher than that of pristine Cu1.8S (0.54 at 773 K) and 95% higher than that of pristine Cu1.8Se (0.4 at 773 K).
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We report the photovoltaic properties of an n-ZnSe/p-GaAs heterostructure. The n-type ZnSe films were grown by molecular beam epitaxy using Zn and Se effusion cells and ZnCl2 as an n-type dopant source. Dark and illuminated I–V characteristics, as well as the spectral response are presented. Two transport mechanisms (recombination and tunneling) were observed in the dark I–V curves as a function of temperature. The photovoltaic parameters of the heterojunction were an open-circuit voltage of 500mV, a short-circuit current density of 15mA/cm2, and a fill factor FF=0.53, resulting in an efficiency close to 4%. The spectral response of the structure extends from the band gap of GaAs to energies higher than that of the band gap of ZnSe, in this high photon energy region being larger than that of a commercial p–i–n Si photodiode.
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Maximum power point tracking (MPPT) must usually be integrated with photovoltaic (PV) power systems so that the photovoltaic arrays are able to deliver the maximum power available. The present paper proposes a maximum power point tracker (MPPT) method, based on fuzzy logic controller (FLC), applied to a stand-alone photovoltaic system under variable temperature and irradiance conditions. The objective of this controller is to extract the maximum power of photovoltaic modules. The main objective o f this work is the development of this control and its implementation on a “FPGA Xilinx Virtex-II” circuit using “Memec Design Virtex-II V2MB1000” Development Board. Thus, we can show the advantages of using the FPGA circuits, which are their short development time, their low cost and their flexibility of operation.
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The development of photovoltaic technology has brought in clean energy production. However, silicon is the most commonly used semiconductor in photovoltaics with power conversion efficiency (PCE) of about 18% to 22% under standard conditions. Recently, the chalcopyrite structure of I-III-VI2 constitutes ternary chalcogenides and the subsequent thin films are being used in second generation thin film solar cells (TFSC). Copper-based (Cu-III-VI2) and silver-based (Ag-III-VI2) chalcogenides are emerged as alternatives for toxic elements & lowcost in optoelectronics. In particular, Copper Indium Diselenide (with the optical band gap of 1.04 eV) cells have up to 14% efficiency with similar durability as silicon solar cells. Similarly, the optical band gap of Cu2SnS3 (CTS) thin films is 1.23 eV and the absorption coefficient is > 105 cm−1 and hence act as potential photoabsorber in TFSC. AgGaSe2 and AgGaTe2 have a direct band gap of 1.42 eV and 0.75 eV, respectively, and strong clarity in the 500–1200 nm wavelength range. Also, the optical properties of Ag-based chalcogenides (AgAlS2) are equivalent to those of Cu-based chalcogenides (CuAlS2). Similarly, a number of ternary semiconductors, including CuInS2, CuSnSe2, CuSbS2, AgInSe2, AgGaS2 and AgBiS2 with a bandgap in visible regions are created with rich crystal structures and high absorption coefficients using various deposition techniques, making them well suited for photoabsorbers. Herein, the latest progress of ternary chalcogenides is reviewed from the aspects of synthesis, characterization, and properties. In addition, their potential in optoelectronic devices is also discussed.
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Poly(p-phenylene vinylene) (PPV) belongs to the class of electroluminescent conjugated polymers. They emit light when electric current is passed through them. Monomers for PPV are 1, 4-Bis-(dichloromethyl)-benzene; α, α-Dibromo-p-xylene; and chlorinated cyclophanes. Polymer cannot be processed without precursor polymer. Precursor polymer can be synthesized by sulfonium precursor (Wessling route), ring opening metathesis polymerization, chemical vapor deposition, electropolymerization, dehydrohalogenation condensation polymerization (Gilch Reaction), dehydrohalogenation phase transfer catalysis, and anionic polymerization. PPV exhibits a higher thermal stability than other related polymers. Ideally, PPV should exhibit a thoroughly π-conjugated structure for electronic applications. But, this structure cannot be achieved because of structural and chemical defects. PPV is a bright yellow fluorescent polymer. The emission maxima are in the yellow–green region of the visible spectrum at 551 nm and 520 nm. Doping creates structural and electronic modifications in the polymer backbone and enhances the electrical conductivity. PPVs are important π-conjugated polymers for electronic and luminescent devices.
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The widespread use of PbTe nanocomposites requires knowledge regarding the composition of their grain boundaries. Cathodoluminescence (CL), TOF-SIMS and Rutherford backscattering spectroscopy (RBS) were used to explore the composition of surface layers formed via thermal, electrochemical, and wet chemical oxidation of lead telluride. Surface layers obtained by these methods contained components with different degrees of oxidation. RBS and CL results show that thermal and anodic oxidation produced ternary PbTeO3 and Pb2TeO4 oxides, respectively. For the chemical oxide we observed a substantially lower concentration of oxygen described by PbO1−x TeO2−x , a significant amount of non-oxidized PbTe ions detected by SIMS, and low CL stability under electron beam radiation. Thus, the chemical oxide is likely a mixture of binary suboxides.
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We have succeeded in growing semiconductor (BaSi2)/metal (CoSi2) hybrid structures epitaxially on Si(111) by molecular beam epitaxy for the first time. When the thickness of CoSi2 was approximately 55nm, the interface between the CoSi2 and BaSi2 layers was found to be rough from transmission electron microscopy observation. The interface became sharp and the BaSi2/CoSi2 hybrid structures were epitaxially grown when the thickness of CoSi2 was decreased down to approximately 27nm, and the growth temperature was properly chosen.
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Man's use of pigments goes back to cave-dwellings, and it is only in the last century or so that colour has become one of the foundation stones of the modern chemicals industry. The development of the plastics industry, however, brought colour to levels, which could never have been attempted before. It has also raised fundamental questions about colour and how it is produced that have preempted an explosion in development.
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Highlights • YBa2Cu3O7 ceramics with c-axis preferred orientation have been prepared by sol–gel method. • c-axis preferred orientation ceramic were obtained only when calcined at 930°C and sintered at 950°C. • X-ray diffraction patterns show that the relative intensity of c-axis (00 l) is much stronger than the standard pattern. • The surface morphologies has an obvious layer-structure and the grains are platelike distributed.
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Spark plasma sintering (SPS) is an emerging powder consolidating technique which promises high potential capabilities to process refractory ceramics with properties previously unattainable. As the first step in studying the applicability of this technique to the processing of tailored ceramic structures, the validity of SPS to consolidate refractory carbides with controllable porosity is investigated. Vanadium carbide (V8C7) is chosen as a studied material. The structure, thermal and mechanical properties of the V8C7 powder pellets produced by SPS are analyzed and discussed in the paper. The attained properties of the processed ceramic material are in particular suitable for applications where high electrical conductivity and strength at high melting temperatures, low thermal conductivity and low thermal expansion coefficient are needed.
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This study presents and demonstrates a methodology for calculating the economic potential of photovoltaic installations in urban areas including the previously often disregarded potential on building façades. The analysis of a 2km2 urban area has shown that building façades there provide almost triple the area of building roofs. However due to non-optimal inclination and orientation, they receive only 41% of the total irradiation. From this, the economic potential under present market conditions was calculated, resulting in 17% of all analyzed building surfaces, i.e. 0.3km2 of roof surfaces being economically exploitable for photovoltaic installations already now which corresponds to an installed capacity of 47MWp. Considering further a material substitution from the building integration of the photovoltaic installations, an economic potential of up to 56MWp or 0.4km2 results, of which up to 6MWp or 0.04km2 are economically installable on building façades. Façade-mounted installations would then account for 13% of the economic potential. The calculation of an economic potential and additionally considering the material substitution from building integration both constitute an extension to many existing renewable energy potential studies just focusing on the technical potential. However, only the economic potential allows forecasts of the future diffusion of this technology.
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This chapter presents the current state of knowledge on tribological phenomena in cutting. The focus is on the presentation of design solutions of tribometers reflecting the frictional conditions during cutting proposed by various scientists. The analysis of the scope of research carried out by various groups of scientists was carried out mainly in the context of tribological research carried out on hard-to-cut materials. An original solution of a pin-on-disc testing device is presented. Its special design and equipment used allow performing tribological tests in a wide range of sliding velocity with control and monitoring of normal force and friction force with high sampling frequency. The paper presents technical solutions and computational algorithms used to analyze and evaluate the measurement signals for a number of tested quantities such as friction coefficient, temperature at the contact point of tribological pair, tribological pair material consumption. The methods of evaluation of dynamic phenomena recorded during frictional tests based on vibration sensors are discussed. The subject of problems of frictional testing was approached in a complex way, combining a number of obtained results into coherent information about the process and tribological conditions in the evaluated tribological pairs.
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PbTe–InSe multilayer nanocomposite structures were prepared by thermal evaporation method using layer by layer assembly with different PbTe nanocrystal (NCs) layer thicknesses ranges from 5 to 20 nm. Cross sectional transmission electron microscopy images divulge the formation of PbTe NCs embedded within InSe matrix as an ordered PbTe–InSe multilayer structure. X-ray and electron beam diffractions from the multilayer structure exhibit eminent peak at (2 0 0) plane analogous to face-centred cubic PbTe. The absorption onset significantly blue shifted as long as 3 nm PbTe NCs were embedded in InSe matrix. The observed band gap is correlated with theoretically predicted effective band gap of three dimensionally confined PbTe NCs which confirm size dependent quantum confinement effect. PL spectra show dominant single emission at 1.6 eV corresponding to the band edge emission of PbTe NCs. The prospects to use this structure in p-i-n junction quantum dot solar cells are discussed.
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90Sr and 137Cs activity concentrations in surface waters of the Sea of Japan (SOJ) decreased during the period of 1993–2010 with effective half-lives of 18 and 15 y, respectively. The longer effective half-life of 90Sr in the SOJ may suggest a surplus of 90Sr to SOJ surface waters, however, no clear evidence of possible 90Sr source has been found. After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, temporal variations of 137Cs in the surface water of the SOJ have changed, while 90Sr variations followed the pre-accident trends. The 90Sr/137Cs ratios reveal that increases of 137Cs due to the FDNPP accident continued in surface waters of the SOJ until 2016.
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With depleting natural resources and the effects of conventional energy sources like coal and petroleum on the environment, clean energy sources have been gaining prominence in recent times. Renewable sources are abundant and improving the efficiency of renewable technologies will provide a viable solution to meet the ever-increasing energy demands of the modern-day world. One of the most effective and practical ways for improving the efficiency of renewable power plants and other possible energy sources is by recovering waste heat (vs. improving the power plant component efficiencies using new designs and materials). However, in many of the existing designs, the waste heat is merely rejected or not effectively utilized. Through a combination of sustainable and hybrid solutions and reusable waste heat methods, a sustainable future for power and advanced technology can be made a reality. Many independent review articles exist in the areas of solar power plants, geothermal power plants, and combined heat and power (CHP) plants. In this article, power generation using solar and geothermal sources when simultaneously operated as CHP plants for waste heat recovery (WHR) is reviewed with the focus on the current state of the art applications for this waste heat. Also, the thermodynamic performance and economics of these power plants when combined with the heat recovery applications are discussed. Finally, the future research direction for the field is suggested based on the current status and findings to pave the way for a more effective waste heat utilization from renewable thermal sources.
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Cu(In,Al)Se2 thin films are investigated for their application as absorber layer material for solar cells. Films are elaborated by selenisation of multilayer metallic precursors deposited by thermal evaporation. In order to minimize the oxidation of the aluminium during the precursor deposition, an alternative deposition method using a Cu–Al eutectic is used. Films are characterized by X-ray diffraction, electron probe microanalysis, scanning electron microscopy, and optical measurements. These measurements show that most of the films are crystallized in the chalcopyrite structure and have the expected optical properties and composition. In some cases, the aluminium segregates and the films behave like CuInSe2. In all cases, the films are not oxidized (less than 1 at.% of O2).
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A quasi-solid-state dye-sensitized solar cells (DSSCs) employing a commercial glue (“SuperGlue®”) as electrolyte matrix was fabricated. The cyano groups of the cyanoacrylate can form a supramolecular complex with tetrapropylammonium cations. This immobilizes the cations and therefore might lead to a favored anionic charge transport necessary for a good performance of the iodide/triiodide electrolytic conductor. Obtaining energy conversion efficiencies of more than 4% under 100mW/cm2 of simulated A.M. 1.5 illumination, the cyanoacrylate quasi-solid-state electrolyte is an ordinary and low-cost compound which has fast drying property and offers significant advantages in the fabrication of solar cells and modules as it is in itself is a very good laminating agent. The influences of different porous layer thicknesses of titanium oxide and various kinds of cations on DSSC performance and long-term stability are presented.
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The composite diamond/titanium electrode which has been investigated here is characterized by a multilayer structure. Termination of the diamond surface in aqueous electrolytes by CH2 and CO is supported by electrochemical measurements. A TiC-layer is formed at the phase boundary between the diamond and the titanium. The electrode shows high overvoltages in aqueous electrolytes (η between 1 and 2 V) for cathodic H2 and anodic O2 and Cl2 evolution. This corresponds to the large band gap of diamond, ΔE=5.45 eV. Redox reactions and electrosynthesis at these novel electrodes are briefly reviewed.
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With the increasing use of photovoltaic (PV) systems, the research studies to improve the efficiency of PV systems have gained greater interest in recent years, especially under non-uniform operating conditions and failed operation. The aim of this paper is the study, the optimization and the analysis of behavior of a photovoltaic system in normal and failed operation for one or more of any defects and any configuration of the PV system (module, string or field) trying to get close to the actual operation of photovoltaic systems.
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We demonstrate efficient noncollinear low-threshold optical parametric oscillation in periodically poled KTP crystal pumped by the second harmonic of the Q-switched Nd:YAG laser. The noncollinear geometry provides an angular frequency tuning at fixed temperature.
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A laboratory-based closure study was completed to compare measured and modeled optical properties and their dependence on controlled relative humidity (RH) for inorganic salts, dicarboxylic acids, and their mixtures. The closure between measured and modeled values of the light scattering coefficients were evaluated by calculating the average relative difference (ARD) values, which revealed agreement within 8.0% for the total scattering (σ sp ) and 14.8% for the back scattering (σ bsp ) values at dry RH conditions for all test aerosols. These ARD values were less than the total relative uncertainty based on the measurement and modeling approaches, indicating the achievement of closure for σ sp and σ bsp . Optical properties derived from σ sp including: (1) the hygroscopic growth factor, f σ s p , (2) the backscatter ratio, b, and (3) the Ångström exponent, å, were also compared with measured values. The ARD values between corresponding measured and modeled results for these derived optical parameters ranged from 0.1% to 30.8%. The impact of particulate organic matter (POM) on optical and hygroscopic properties of the aerosols tested here was also compared to the aerosol optical and composition measurements that occurred during the New England Air Quality Study-Intercontinental Transport and Chemical Transformation field campaign. Such comparison confirmed that a larger POM mass fraction resulted in less hygroscopicity for both the ambient and the laboratory aerosols. This study evaluated closure between laboratory measurements and model calculations and validated the reliability of the measured and modeled results with the closure analysis. Therefore, Mie-Lorentz model can be used to calculate the optical properties and their dependence on RH for other aerosols with more confidence.
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Highlights • PEDOT/rGO nanocomposite bulk is prepared by in situ micro-emulsion polymerization followed by cold-pressing and annealing. • Thermal treatment and rGO doping lead to enhanced electrical conductivity and thermoelectric power factor. • The enhanced electrical properties are mainly due to the optimized microstructure and rGO serving as conducting channels.
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