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most of the existing object detection works are based on the bounding box annotation : each object has a precise annotated box. however, for rib fractures, the bounding box annotation is very labor - intensive and time - consuming because radiologists need to investigate and annotate the rib fractures on a slice - by - slice basis. although a few studies have proposed weakly - supervised methods or semi - supervised methods, they could not handle different forms of supervision simultaneously. in this paper, we proposed a novel omni - supervised object detection network, which can exploit multiple different forms of annotated data to further improve the detection performance. specifically, the proposed network contains an omni - supervised detection head, in which each form of annotation data corresponds to a unique classification branch. furthermore, we proposed a dynamic label assignment strategy for different annotated forms of data to facilitate better learning for each branch. moreover, we also design a confidence - aware classification loss to emphasize the samples with high confidence and further improve the model ' s performance. extensive experiments conducted on the testing dataset show our proposed method outperforms other state - of - the - art approaches consistently, demonstrating the efficacy of deep omni - supervised learning on improving rib fracture detection performance. | arxiv:2207.01842 |
there is currently a lot of activity in r \ & d for future collider experiments. multiple detector prototypes are being tested, each one with slightly different requirements regarding the format of the data to be analysed. this has generated a variety of ad - hoc solutions for data acquisition and online data monitoring. we present a generic c + + 11 online monitoring framework called dqm4hep, which is designed for use as a generic online monitor for particle physics experiments, ranging from small tabletop experiments to large multi - detector testbeams, such as those currently ongoing / planned at the desy ii or cern sps beamlines. we present results obtained using dqm4hep at several testbeams where the calice ahcal, sdhcal and siwecal detector prototypes have been tested. during these testbeams, online analysis using dqm4hep \ ' s framework has been developed and used. we also present the currently ongoing work to integrate dqm4hep within the eudaq tool. eudaq is a tool for common and generic data acquisition within the aida - 2020 collaboration. this will allow these two frameworks to work together as a generic and complete daq and monitoring system for any type of detector prototype tested on beam tests, which is one of the goals of the aida - 2020 project. | arxiv:1801.10414 |
the projector - augmented wave ( paw ) method is one of the approaches that are widely used to approximately treat core electrons and thus to speed - up plane - wave basis set electronic structure calculations. however, paw involves approximations and it is thus important to understand how they affect the results. tests of precision of paw data sets often use properties of isolated atoms or of atomic solids. while this is sufficient to identify problematic paw data sets, little information has been gained to understand the origins of the errors and suggest ways to correct them. here we show that interaction energies of molecular dimers are very useful not only to identify problematic paw data sets but also to uncover the origin of the errors. using dimers from the s22 and s66 test sets and other dimers we find that the error in the interaction energy is composed of a short range component with an exponential decay and a long range electrostatic part caused by error in the total charge density. we propose and evaluate a simple improvable scheme to correct the long range error and find that even in its simple and readily usable form, it is able to reduce the interaction energy errors to less than one half on average for hydrogen bonded dimers. | arxiv:2308.12087 |
affordances are central to robotic manipulation, where most tasks can be simplified to interactions with task - specific regions on objects. by focusing on these key regions, we can abstract away task - irrelevant information, simplifying the learning process, and enhancing generalisation. in this paper, we propose an affordance - centric policy - learning approach that centres and appropriately \ textit { orients } a \ textit { task frame } on these affordance regions allowing us to achieve both \ textbf { intra - category invariance } - - where policies can generalise across different instances within the same object category - - and \ textbf { spatial invariance } - - which enables consistent performance regardless of object placement in the environment. we propose a method to leverage existing generalist large vision models to extract and track these affordance frames, and demonstrate that our approach can learn manipulation tasks using behaviour cloning from as little as 10 demonstrations, with equivalent generalisation to an image - based policy trained on 305 demonstrations. we provide video demonstrations on our project site : https : / / affordance - policy. github. io. | arxiv:2410.12124 |
robust online estimation of oscillation frequency belongs to classical problems of system identification and adaptive control. the given harmonic signal can be noisy and with varying amplitude at the same time, as in the case of damped vibrations. a novel robust frequency - estimation algorithm is proposed here, motivated by the existing globally convergent frequency estimator. the advantage of the proposed estimator is in requiring one design parameter only and being robust against measurement noise and initial conditions. the proven global convergence also allows for slowly varying amplitudes, which is useful for applications with damped oscillations or additionally shaped harmonic signals. the proposed analysis is simple and relies on an averaging theory of the periodic signals. our results show an exponential convergence rate, which depends, analytically, on the sought frequency, adaptation gain and oscillation amplitude. numerical and experimental examples demonstrate the robustness and efficiency of the proposed estimator for signals with slowly varying amplitude and noise. | arxiv:2101.12497 |
determinant quantum monte carlo ( dqmc ) is used to determine the pairing and magnetic response for a hubbard model built up from four - site clusters - a two - dimensional square lattice consisting of elemental 2x2 plaquettes with hopping $ t $ and on - site repulsion $ u $ coupled by an inter - plaquette hopping $ t ' \ leq t $. superconductivity in this geometry has previously been studied by a variety of analytic and numeric methods, with differing conclusions concerning whether the pairing correlations and transition temperature are raised near half - filling by the inhomogeneous hopping or not. for $ u / t = 4 $, dqmc indicates an optimal $ t ' / t \ approx 0. 4 $ at which the pairing vertex is most attractive. the optimal $ t ' / t $ increases with $ u / t $. we then contrast our results for this plaquette model with a hamiltonian which instead involves a regular pattern of site energies whose large site energy limit is the three band cuo $ _ 2 $ model ; we show that there the inhomogeneity rapidly, and monotonically, suppresses pairing. | arxiv:1401.7226 |
we address the question of detecting minimal virtual diagrams with respect to the number of virtual crossings. this problem is closely connected to the problem of detecting the minimal number of additional intersection points for a generic immersion of a singular link in $ r ^ { 2 } $. we tackle this problem by the so - called $ \ xi $ - polynomial whose leading ( lowest ) degree naturally estimates the virtual crossing number. several sufficient conditions for minimality together with infinite series of new examples are given. we also state several open questions about $ m $ - diagrams, which are minimal according to our sufficient conditions. | arxiv:0811.0712 |
gas masses tightly correlate with the virial masses of galaxy clusters, allowing for a precise determination of cosmological parameters by means of large - scale x - ray surveys. however, according to recent suzaku x - ray measurements, gas mass fractions, f _ gas, appear to be considerably larger than the cosmic mean at the virial radius, r _ 200, questioning the accuracy of the cosmological parameter estimations. here, we use a large suite of cosmological hydrodynamical simulations to study measurement biases of f _ gas. we employ different variants of simulated physics, including radiative gas physics, star formation, and thermal feedback by active galactic nuclei. computing the mass profiles in 48 angular cones, whose footprints partition the sphere, we find anisotropic gas and total mass distributions that imply an angular variance of f _ gas at the level of 30 %. this anisotropic distribution originates from the recent formation epoch of clusters and from the strong internal baryon - to - dark - matter density bias. in the most extreme cones, f _ gas can be biased high by a factor of two at r _ 200 in massive clusters, thereby providing a potential explanation for high f _ gas measurements by suzaku. while projection lowers this factor, there are other measurement biases that may ( partially ) compensate. we find that at r _ 200, f _ gas is biased high by 20 % when assuming hydrostatic equilibrium masses, i. e., neglecting the kinetic pressure, and by another ~ 10 - 20 % due to the presence of density clumping. at larger radii, both measurement biases increase dramatically. while the cluster sample variance of the true f _ gas decreases to a level of 5 % at r _ 200, the sample variance that includes both measurement biases remains fairly constant at the level of 10 - 20 %. the constant redshift evolution of f _ gas within r _ 500 for massive clusters is encouraging for using gas masses to derive cosmological parameters. | arxiv:1209.4082 |
a consistent theoretical description of physics at high energies requires an assessment of vacuum stability in either the standard model or any extension of it. especially supersymmetric extensions allow for several vacua and the choice of the desired electroweak one gives strong constraints on the parameter space. as the general parameter space in the minimal supersymmetric standard model is huge, any severe constraint on it unrelated to direct phenomenological observations enhances the predictability of the model. we perform an updated analysis of possible charge and color breaking minima without relying on fixed directions in field space that minimize certain terms in the potential ( known as " d - flat " directions ). concerning the cosmological stability of false vacua, we argue that there are always directions in configuration space which lead to very short - lived vacua and therefore such exclusions are strict. in addition to existing strong constraints on the parameter space, we find even stronger constraints extending the field space compared to previous analyses and combine those constraints with predictions for the light cp - even higgs mass in the minimal supersymmetric standard model. low masses for supersymmetric partners are excluded from vacuum stability in combination with the 125 gev higgs and the allowed parameter space opens at a few tev. | arxiv:1606.08356 |
we review our recent results on the on - shell description of sine - gordon model with integrable boundary conditions. we determined the spectrum of boundary states by closing the boundary bootstrap and gave a derivation of al. b. zamolodchikov ' s ( unpublished ) formulae for the boundary energy and the relation between the lagrangian ( ultraviolet ) and bootstrap ( infrared ) parameters. these results have been checked against numerical finite volume spectra coming from the truncated conformal space approach. we find an entirely consistent picture and strong evidence for the validity of the conjectured spectrum and scattering amplitudes, which together give a complete description of the boundary sine - gordon theory on mass shell. | arxiv:hep-th/0108211 |
let $ m $ be a compact manifold equipped with a pair of complementary foliations, say horizontal $ \ mathcal { h } $ and vertical $ \ mathcal { v } $. in melo, morgado and ruffino ( disc cont dyn syst b, 2016, 21 ( 9 ) ) it is proved that if a semimartingale $ x _ t $ has a finite number of jumps in compact intervals then, up to a stopping time $ \ tau $, a stochastic flow of local diffeomorphisms in $ m $ driven by $ x _ t $ can be decomposed into a process in the lie group of diffeomorphisms which fix the leaves of $ \ mathcal { h } $ composed with a process in the lie group of diffeomorphisms which fix the leaves of $ \ mathcal { v } $. dynamics at the discontinuities of $ x _ t $ here are interpreted in the marcus sense as in kurtz, pardoux and protter \ cite { kpp }. here we enlarge the scope of this geometric decomposition and consider flows driven by arbitrary semimartingales with jumps and show explicit equations for each component. our technique is based in an extension of the it \ ^ o - ventzel - kunita formula for stochastic flows with jumps. geometrical and others topological obstructions for the decomposition are also considered : e. g. an index of attainability is introduced to measure the complexity of the dynamics with respect to the pair of foliations. | arxiv:2501.01750 |
this study introduces a novel approach to industrial asset management ( iam ) by incorporating conditional - based management ( cbm ) principles with the latest advancements in large language models ( llms ). our research introduces an automated model - building process, traditionally reliant on intensive collaboration between data scientists and domain experts. we present two primary innovations : a taxonomy - guided prompting generation that facilitates the automatic creation of ai solution recipes and a set of llm pipelines designed to produce a solution recipe containing a set of artifacts composed of documents, sample data, and models for iam. these pipelines, guided by standardized principles, enable the generation of initial solution templates for heterogeneous asset classes without direct human input, reducing reliance on extensive domain knowledge and enhancing automation. we evaluate our methodology by assessing asset health and sustainability across a spectrum of ten asset classes. our findings illustrate the potential of llms and taxonomy - based llm prompting pipelines in transforming asset management, offering a blueprint for subsequent research and development initiatives to be integrated into a rapid client solution. | arxiv:2407.18992 |
we classify the standard model fermions, which originate from bulk fields of the $ \ bf { 27 } $ or $ \ bar { \ bf { 27 } } $ representation after orbifold breaking, in $ e _ 6 $ grand unified theories on 5 or 6 - dimensional space - time, under the condition that $ q $, $ e ^ c $ and $ u ^ c $ survive as zero modes. | arxiv:1301.7469 |
in the present work, flat frw model of the universe is considered to be an isolated open thermodynamical system where non - equilibrium prescription has been studied using the mechanism of particle creation. in the perspective of recent observational evidences, the matter distribution in the universe is assumed to be dominated by dark matter and dark energy. the dark matter is chosen as dust while for dark energy, the following choices are considered : ( i ) perfect fluid with constant equation of state and ( ii ) holographic dark energy. in both the cases, the validity of generalized second law of thermodynamics ( gslt ) which states that the total entropy of the fluid as well as that of the horizon should not decrease with the evolution of the universe, has been examined graphically for universe bounded by the event horizon. it is found that gslt holds in both the cases with some restrictions on the interacting coupling parameter. | arxiv:1507.08224 |
recently tang and boozer [ { \ textbf { phys. plasmas ( 2000 ) } } ], have investigated the anisotropies in magnetic field dynamo evolution, from local lyapunov exponents, giving rise to a metric tensor, in the alfven twist in magnetic flux tubes ( mfts ). thiffeault and boozer [ \ textbf { chaos } ( 2001 ) ] have investigated the how the vanishing of riemann curvature constrained the lyapunov exponential stretching of chaotic flows. in this paper, tang - boozer - thiffeault differential geometric framework is used to investigate effects of twisted magnetic flux tube filled with helical chaotic flows on the riemann curvature tensor. when frenet torsion is positive, the riemann curvature is unstable, while the negative torsion induces an stability when time $ t \ to { \ infty } $. this enhances the dynamo action inside the mfts. the riemann metric, depends on the radial random flows along the poloidal and toroidal directions. the anosov flows has been applied by arnold, zeldovich, ruzmaikin and sokoloff [ \ textbf { jetp ( 1982 ) } ] to build a uniformly stretched dynamo flow solution, based on arnold ' s cat map. it is easy to show that when the random radial flow vanishes, the magnetic field vanishes, since the exponential lyapunov stretches vanishes. this is an example of the application of the vishik ' s anti - fast dynamo theorem in the magnetic flux tubes. geodesic flows of both arnold and twisted mft dynamos are investigated. it is shown that a constant random radial flow can be obtained from the geodesic equation. throughout the paper one assumes, the reasonable plasma astrophysical hypothesis of the weak torsion. pseudo - anosov dynamo flows and maps have also been addressed by gilbert [ \ textbf { proc roy soc a london ( 1993 ) } | arxiv:0811.3630 |
in this paper we investigate a quantity called conditional entropy of ordinal patterns, akin to the permutation entropy. the conditional entropy of ordinal patterns describes the average diversity of the ordinal patterns succeeding a given ordinal pattern. we observe that this quantity provides a good estimation of the kolmogorov - sinai entropy in many cases. in particular, the conditional entropy of ordinal patterns of a finite order coincides with the kolmogorov - sinai entropy for periodic dynamics and for markov shifts over a binary alphabet. finally, the conditional entropy of ordinal patterns is computationally simple and thus can be well applied to real - world data. | arxiv:1407.5390 |
a short review of the properties of the spin light of neutrino ( $ sl \ nu $ ) in matter, supplied with some historical notes on the discussed subject, is given. it is shown that consideration of the $ sl \ nu $ in matter in hep - ph / 0605114 is based on erroneous calculations which ignore the fact that the energy - momentum conservation law can not be violated for this process. an attempt to rename the $ sl \ nu $ in matter, undertaken in hep - ph / 0606262, is groundless. | arxiv:hep-ph/0610294 |
near infrared spectra of 133 red giant stars from ten galactic open clusters and two galactic globular clusters spanning 2. 2 dex in metallicity and 11 gyr in age are presented. we combine this sample with ten clusters from cole and collaborators to investigate the ca ii triplet line strengths and their relation to cluster metallicity and position along the red giant branch. we show that characterizing the stellar surface gravity using ks band photometry ( relative to the horizontal branch ) taken from the two micron all - sky survey allows for metallicity measurements at least as precise as those derived using v or i band data. this has the great advantage that uniform photometry and reliable astrometry is available for a large number of clusters. using ks band photometry also reduces the effect of differential reddening within a given cluster. we find no significant evidence for age or metallicity effects to the linear ca ii triplet - metallicity relationship over the small range in magnitudes studied when homogeneous reference metallicities are used. we derive the first spectroscopic metallicity and new radial velocity estimates for five open clusters : berkeley 81, berkeley 99, ic 1311, king 2, and ngc 7044. king 2 has an anomalous radial velocity compared with the local disk population. we discuss the possibility that it is part of the monoceros tidal stream. | arxiv:0811.2925 |
data distortion is commonly applied in vision models during both training ( e. g methods like mixup and cutmix ) and evaluation ( e. g. shape - texture bias and robustness ). this data modification can introduce artificial information. it is often assumed that the resulting artefacts are detrimental to training, whilst being negligible when analysing models. we investigate these assumptions and conclude that in some cases they are unfounded and lead to incorrect results. specifically, we show current shape bias identification methods and occlusion robustness measures are biased and propose a fairer alternative for the latter. subsequently, through a series of experiments we seek to correct and strengthen the community ' s perception of how augmenting affects learning of vision models. based on our empirical results we argue that the impact of the artefacts must be understood and exploited rather than eliminated. | arxiv:2110.13968 |
the paper develops high - order accurate physical - constraints - preserving finite difference weno schemes for special relativistic hydrodynamical ( rhd ) equations, built on the local lax - friedrich splitting, the weno reconstruction, the physical - constraints - preserving flux limiter, and the high - order strong stability preserving time discretization. they are extensions of the positivity - preserving finite difference weno schemes for the non - relativistic euler equations. however, developing physical - constraints - preserving methods for the rhd system becomes much more difficult than the non - relativistic case because of the strongly coupling between the rhd equations, no explicit expressions of the primitive variables and the flux vectors, in terms of the conservative vector, and one more physical constraint for the fluid velocity in addition to the positivity of the rest - mass density and the pressure. the key is to prove the convexity and other properties of the admissible state set and discover a concave function with respect to the conservative vector replacing the pressure which is an important ingredient to enforce the positivity - preserving property for the non - relativistic case. several one - and two - dimensional numerical examples are used to demonstrate accuracy, robustness, and effectiveness of the proposed physical - constraints - preserving schemes in solving rhd problems with large lorentz factor, or strong discontinuities, or low rest - mass density or pressure etc. | arxiv:1504.07707 |
given $ ( m, g ) $, a compact connected riemannian manifold of dimension $ d \ geq 2 $, with boundary $ \ partial m $, we consider an initial boundary value problem for a fractional diffusion equation on $ ( 0, t ) \ times m $, $ t > 0 $, with time - fractional caputo derivative of order $ \ alpha \ in ( 0, 1 ) \ cup ( 1, 2 ) $. we prove uniqueness in the inverse problem of determining the smooth manifold $ ( m, g ) $ ( up to an isometry ), and various time - independent smooth coefficients appearing in this equation, from measurements of the solution on a subset of $ \ partial m $ at fixed time. in the " flat " case where $ m $ is a compact subset of $ \ mathbb r ^ d $, two out the three coefficients $ \ rho $ ( weight ), $ a $ ( conductivity ) and $ q $ ( potential ) appearing in the equation $ \ rho \ partial _ t ^ \ alpha u - \ textrm { div } ( a \ nabla u ) + q u = 0 $ on $ ( 0, t ) \ times \ omega $ are recovered simultaneously. | arxiv:1601.00810 |
we examine linear dust acoustic waves ( daws ) in a dusty plasma with strongly correlated dust grains, and discuss possibility of a twisted da vortex beam carrying orbital angular momentum ( oam ). for our purposes, we use the boltzmann distributed electron and ion density perturbations, the dust continuity and generalized viscoelastic dust momentum equations, and poisson ' s equation to obtain a dispersion relation for the modified daws. the effects of the polarization force, strong dust couplings, and dust charge fluctuations on the daw spectrum are examined. furthermore, we demonstrate that the daw can propagate as a twisted vortex beam carrying oam. a twisted da vortex structure can trap and transport dust particles in dusty plasmas. | arxiv:1208.0994 |
we present a preliminary study of schur norms $ \ | m \ | _ { s } = \ max \ { \ | m \ circ c \ | : \ | c \ | = 1 \ } $, where m is a matrix whose entries are $ \ pm1 $, and $ \ circ $ denotes the entrywise ( i. e., schur or hadamard ) product of the matrices. we show that, if such a matrix m is n - by - n, then its schur norm is bounded by $ \ sqrt { n } $, and equality holds if and only if it is a hadamard matrix. we develop a numerically efficient method of computing schur norms, and as an application of our results we present several almost hadamard matrices that are better than were previously known. | arxiv:2206.02863 |
mass loss rates for the tenuous, hot winds of cool stars are extremely difficult to measure, yet they are a crucial ingredient in the stars ' rotational evolution. we present a new method for measuring these mass loss rates in young, rapidly - rotating stars. these stars are known to support systems of " slingshot prominences " fed by hot wind material flowing up from the stellar surface into the summits of closed magnetic loop structures. the material gathers and cools near the co - rotation radius until its density becomes large enough that it is visible as a transient absorption feature in the hydrogen balmer lines and strong resonance lines such as ca ii h \ & \ k. here we present the key insight that the sonic point usually lies well below the condensation region. the flow at the wind base is therefore unaffected by the presence of an overlying prominence, so we can use the observed masses and recurrence times of the condensations to estimate the mass flux in the wind. these measurements extend the relationship between mass loss rate per unit surface area and x - ray flux to span 5 orders of magnitude. they demonstrate no evidence of the suspected weakening of stellar mass loss rates at high x - ray flux levels. | arxiv:1810.09319 |
determining the heating mechanism ( or mechanisms ) that causes the outer atmosphere of the sun, and many other stars, to reach temperatures orders of magnitude higher than their surface temperatures has long been a key problem. for decades the problem has been known as the coronal heating problem, but it is now clear that ` coronal heating ' cannot be treated or explained in isolation and that the heating of the whole solar atmosphere must be studied as a highly coupled system. the magnetic field of the star is known to play a key role, but, despite significant advancements in solar telescopes, computing power and much greater understanding of theoretical mechanisms, the question of which mechanism or mechanisms are the dominant supplier of energy to the chromosphere and corona is still open. following substantial recent progress, we consider the most likely contenders and discuss the key factors that have made, and still make, determining the actual ( coronal ) heating mechanism ( or mechanisms ) so difficult. | arxiv:1206.6097 |
models of generalized parton distributions at zero skewness are used to relate the behavior of deep inelastic scattering quark distributions, evaluated at high x, to the transverse charge density evaluated at small distances. we obtain an interpretation of the recently obtained negative central charge density of the neutron. the d quarks dominate the neutron structure function for large values of bjorken x, where the large momentum of the struck quark has a significant impact on determining the center of momentum, and thus the ` ` center ' ' of the nucleon in the transverse position plane. | arxiv:0806.3977 |
mechanical systems exhibit complex dynamical behavior from harmonic oscillations to chaotic motion. the dynamics undergo qualitative changes due to changes to internal system parameters like stiffness and changes to external forcing. mapping out complete bifurcation diagrams numerically or experimentally is resource - consuming, or even infeasible. this study uses a data - driven approach to investigate how bifurcations can be learned from a few system response measurements. particularly, the concept of reservoir computing ( rc ) is employed. as proof of concept, a minimal training dataset under the resource constraint problem of a duffing oscillator with harmonic external forcing is provided as training data. our results indicate that the rc not only learns to represent the system dynamics for the external forcing seen during training, but it also provides qualitatively accurate and robust system response predictions for completely unknown multi - parameter regimes outside the training data. particularly, while being trained solely on regular period - 2 cycle dynamics, the proposed framework correctly predicts higher - order periodic and even chaotic dynamics for out - of - distribution forcing signals. | arxiv:2408.14987 |
the factors that influence the symmetry of an imploding detonation are investigated experimentally and theoretically. detonations in sub - atmospheric acetylene - oxygen were initiated and made to converge in an apparatus that followed that of lee and lee ( phys fluids 8 : 2148 - 2152, 1965 ). the width of the test section was controlled with a wave - shaping insert, which formed the test section against the viewing window, creating an effectively two - dimensional problem with a channel width comparable to the detonation cell size. the convergence of the detonation was observed via self - luminous open - shutter photography and high - speed videography. the resulting videos were analyzed to quantify the wave speed, degree of asymmetry, and direction and magnitude of the offset in the center of convergence. to determine the experimental parameters that influence the symmetry of the imploding wave, the wave - shaping insert was intentionally canted by 0. 3 { \ deg } - 0. 6 { \ deg }, accentuating the asymmetry of the imploding detonation. the experiment was modeled using a huygens construction wherein the detonation is treated as a collection of wavelets, each assumed to propagate locally at a velocity determined by the channel width. the results of the model reproduced the observed offsets in detonation convergence from the center of the apparatus, confirming that velocity deficits resulting from the narrow channel width control the observed asymmetry. | arxiv:2408.04153 |
deep neural networks have demonstrated remarkable success in various domains but remain susceptible to adversarial examples, which are slightly altered inputs designed to induce misclassification. while adversarial attacks typically optimize under lp norm constraints, attacks based on the l0 norm, prioritising input sparsity, are less studied due to their complex and non convex nature. these sparse adversarial examples challenge existing defenses by altering a minimal subset of features, potentially uncovering more subtle dnn weaknesses. however, the current l0 norm attack methodologies face a trade off between accuracy and efficiency either precise but computationally intense or expedient but imprecise. this paper proposes a novel, scalable, and effective approach to generate adversarial examples based on the l0 norm, aimed at refining the robustness evaluation of dnns against such perturbations. | arxiv:2408.15702 |
we investigate the effects of top quark compositeness on various physical parameters, and obtain lower limits on the compositeness scale from electroweak precision data. we consider corrections to top quark decay rates and other physical processes. our results depend sensitively on whether the left - handed top is composite. a considerable enhancement of $ t \ bar t $ production is possible if only the right - handed top is composite. | arxiv:hep-ph/9410307 |
this paper considers a joint transmission scheme ( jt ) developed for cloud radio access networks ( c - rans ). this proposed scheme features cooperative sets of remote radio heads ( rrh ) defined in a disk around each user location. the nodes belonging to each of these sets perform a weighted maximum ratio transmission to jointly serve the user. the powers allocated to the beamformers are computed at the network baseband unit, taking into account channel gains, as well an equity criterion between the users. in comparison with the existing literature, our model includes a saturation assumption, with all transmissions taking place over the same resource block. a rrh belonging to multiple sets can hence transmit to several users simultaneously. the distributions of the network coverage and spectral efficiency are calculated by means of stochastic geometry ( sg ), and compared with monte carlo simulations. the derived expressions take into account the power allocation, the user and rrh densities, as well as the statistical correlation resulting from the set overlaps. | arxiv:2104.06807 |
most of the matter in the universe is in the form of dark matter. however, dark matter has never been observed to interact with normal matter in laboratory experiments. alps - - ultralight axionlike particles - - are a class of dark matter models that are consistent with astrophysical constraints, and produce measurable signatures in the form of oscillating violations of discrete symmetries in nuclei. we report the first results from a search for oscillating parity - odd time - reversal - odd nuclear moments of $ ^ { 153 } $ eu ions in a crystal, which leads to an experimental constraint on the alp - gluon coupling strength across a wide band of alp masses. | arxiv:2410.02218 |
large language models ( llms ) have achieved great success, but their occasional content fabrication, or hallucination, limits their practical application. hallucination arises because llms struggle to admit ignorance due to inadequate training on knowledge boundaries. we call it a limitation of llms that they can not accurately express their knowledge boundary, answering questions they know while admitting ignorance to questions they do not know. in this paper, we aim to teach llms to recognize and express their knowledge boundary, so they can reduce hallucinations caused by fabricating when they do not know. we propose coke, which first probes llms ' knowledge boundary via internal confidence given a set of questions, and then leverages the probing results to elicit the expression of the knowledge boundary. extensive experiments show coke helps llms express knowledge boundaries, answering known questions while declining unknown ones, significantly improving in - domain and out - of - domain performance. | arxiv:2406.10881 |
the polymer model framework is a classical tool from statistical mechanics that has recently been used to obtain approximation algorithms for spin systems on classes of bounded - degree graphs ; examples include the ferromagnetic potts model on expanders and on the grid. one of the key ingredients in the analysis of polymer models is controlling the growth rate of the number of polymers, which has been typically achieved so far by invoking the bounded - degree assumption. nevertheless, this assumption is often restrictive and obstructs the applicability of the method to more general graphs. for example, sparse random graphs typically have bounded average degree and good expansion properties, but they include vertices with unbounded degree, and therefore are excluded from the current polymer - model framework. we develop a less restrictive framework for polymer models that relaxes the standard bounded - degree assumption, by reworking the relevant polymer models from the edge perspective. the edge perspective allows us to bound the growth rate of the number of polymers in terms of the total degree of polymers, which in turn can be related more easily to the expansion properties of the underlying graph. to apply our methods, we consider random graphs with unbounded degrees from a fixed degree sequence ( with minimum degree at least 3 ) and obtain approximation algorithms for the ferromagnetic potts model, which is a standard benchmark for polymer models. our techniques also extend to more general spin systems. | arxiv:2105.00524 |
we have observed an interesting, yet unexplained, phenomenon : semidefinite programming ( sdp ) based relaxations of maximum likelihood estimators ( mle ) tend to be tight in recovery problems with noisy data, even when mle cannot exactly recover the ground truth. several results establish tightness of sdp based relaxations in the regime where exact recovery from mle is possible. however, to the best of our knowledge, their tightness is not understood beyond this regime. as an illustrative example, we focus on the generalized procrustes problem. | arxiv:1404.2655 |
exit paths in buildings are designed to minimise evacuation time when the building is at full capacity. we present an evacuation support system which does this regardless of the number of evacuees. the core concept is to even - out congestion in the building by diverting evacuees to less - congested paths in order to make maximal usage of all accessible routes throughout the entire evacuation process. the system issues a set of flow - optimal routes using a capacity - constrained routing algorithm which anticipates evolutions in path metrics using the concept of " future capacity reservation ". in order to direct evacuees in an intuitive manner whilst implementing the routing algorithm ' s scheme, we use dynamic exit signs, i. e. whose pointing direction can be controlled. to make this system practical and minimise reliance on sensors during the evacuation, we use an evacuee mobility model and make several assumptions on the characteristics of the evacuee flow. we validate this concept using simulations, and show how the underpinning assumptions may limit the system ' s performance, especially in low - headcount evacuations. | arxiv:1312.0489 |
0 ^ { \ circ } $ toward the anticentre. | arxiv:0909.4753 |
this work presents an empirical study of the evolution of the consumer expenditure distribution in india during 1982 - 2007. we have used the national sample survey organization data and analysed the expenditure distribution for the urban and rural sectors. it is found that this distribution is a mixture of two distributions, more particularly, it follows a lognormal in the lower tail and a pareto distribution in the higher end. the pareto tail consists of a remarkable 30 - 40 % of the population in the upper end and the lower end is suitably modeled by the lognormal one. the goodness - of - fit tests endorse the proposed distribution. moreover, the pareto tail is widening over time for the rural sector. the gini coefficient, a prominent measure for inequality, for the expenditure distribution is found to be stable for the entire time span. | arxiv:0912.5420 |
atomically flat surfaces of van der waals ( vdw ) materials pave an avenue for addressing a long - standing fundamental issue of how a perfectly compensated antiferromagnet ( afm ) surface frustrates a ferromagnetic ( fm ) overlayer in fm / afm heterostructures. by revealing the afm and fm spin structures separately in vdw fe5gete2 / nips3 heterostructures, we find that c - type in - plane afm nips3 develops three equivalent afm domains which are robust against external magnetic field and magnetic coupling with fe5gete2. consequently, spin frustration at the fe5gete2 / nips3 interface was shown to develop a perpendicular fe5gete2 magnetization in the interfacial region that switches separately from the bulk of the fe5gete2 magnetizations. in particular, we discover an unconventional spin twisting state that the fe5gete2 spins twist from perpendicular direction near the interface to in - plane direction away from the interface in fe5gete2 / nips3. our finding of the twisting spin texture is a unique property of spin frustration in van der waals magnetic heterostructures. | arxiv:2501.16702 |
momentum distributions of particles from fast three - body halo fragmentation reactions with polarized beams and outgoing fragments are analyzed by use of the sudden approximation. the final state interaction between the two non - disturbed particles is considered. we first give a general and detailed description of the method. we introduce observable quantities that emphasize the two - body correlations in the initial three - body structure as well as in the final two - body system. using neutron removal from 11li as an example we investigate the dependence of the polarization observables on the properties of the low - lying resonances and virtual states of the 10li subsystem. these observables are very sensitive to the l > 0 - waves in the wave functions, and they provide detailed information on the resonance structure of the neutron - core subsystem. | arxiv:nucl-th/9608030 |
newtonian adiabatics is the consistent truncation of the adiabatic approximation to second order in small velocities. to be complete it must unify two hitherto disjoint intellectual streams in the study of adiabatic motion. the newer stream focuses on berry ' s induced vector potential, or geometric magnetism, and provost and vallee ' s induced scalar potential, reflecting geometry in hilbert space. the older stream focuses on inglis ' induced inertia, influencing the geometry of adiabatic - parameter space. starting with the hamiltonian of the newer stream, unification is simple : a naive or primitive inertia, whose inverse appears in two terms of that hamiltonian, is replaced by the convention - independent sum of primitive and induced inertia tensors. | arxiv:quant-ph/0502132 |
in this work, the crack nucleation under fretting loading is investigated experimentally with a damage tolerant 2024 aluminium alloy. a new method is introduced to determine its condition with respect to all loading parameters including the number of fretting cycles. further work deals with the prediction of this threshold using the smith - watson - topper criterion. new developments are presented, in particular a process volume of variable size is introduced in the computations of the fretting crack initiation. | arxiv:0810.4096 |
we derive and investigate an expression for the dynamically modified decay of states coupled to an arbitrary continuum. this expression is universally valid for weak temporal perturbations. the resulting insights can serve as useful recipes for optimized control of decay and decoherence. | arxiv:quant-ph/0107076 |
texts convey sophisticated knowledge. however, texts also convey sensitive information. despite the success of general - purpose language models and domain - specific mechanisms with differential privacy ( dp ), existing text sanitization mechanisms still provide low utility, as cursed by the high - dimensional text representation. the companion issue of utilizing sanitized texts for downstream analytics is also under - explored. this paper takes a direct approach to text sanitization. our insight is to consider both sensitivity and similarity via our new local dp notion. the sanitized texts also contribute to our sanitization - aware pretraining and fine - tuning, enabling privacy - preserving natural language processing over the bert language model with promising utility. surprisingly, the high utility does not boost up the success rate of inference attacks. | arxiv:2106.01221 |
program obfuscation is a widely employed approach for software intellectual property protection. however, general obfuscation methods ( e. g., lexical obfuscation, control obfuscation ) implemented in mainstream obfuscation tools are heuristic and have little security guarantee. recently in 2013, garg et al. have achieved a breakthrough in secure program obfuscation with a graded encoding mechanism and they have shown that it can fulfill a compelling security property, i. e., indistinguishability. nevertheless, the mechanism incurs too much overhead for practical usage. besides, it focuses on obfuscating computation models ( e. g., circuits ) rather than real codes. in this paper, we aim to explore secure and usable obfuscation approaches from the literature. our main finding is that currently we still have no such approaches made secure and usable. the main reason is we do not have adequate evaluation metrics concerning both security and performance. on one hand, existing code - oriented obfuscation approaches generally evaluate the increased obscurity rather than security guarantee. on the other hand, the performance requirement for model - oriented obfuscation approaches is too weak to develop practical program obfuscation solutions. | arxiv:1710.01139 |
model - free deep reinforcement learning ( rl ) algorithms have been demonstrated on a range of challenging decision making and control tasks. however, these methods typically suffer from two major challenges : very high sample complexity and brittle convergence properties, which necessitate meticulous hyperparameter tuning. both of these challenges severely limit the applicability of such methods to complex, real - world domains. in this paper, we propose soft actor - critic, an off - policy actor - critic deep rl algorithm based on the maximum entropy reinforcement learning framework. in this framework, the actor aims to maximize expected reward while also maximizing entropy. that is, to succeed at the task while acting as randomly as possible. prior deep rl methods based on this framework have been formulated as q - learning methods. by combining off - policy updates with a stable stochastic actor - critic formulation, our method achieves state - of - the - art performance on a range of continuous control benchmark tasks, outperforming prior on - policy and off - policy methods. furthermore, we demonstrate that, in contrast to other off - policy algorithms, our approach is very stable, achieving very similar performance across different random seeds. | arxiv:1801.01290 |
a new phase field crystal ( pfc ) type theory is presented, which accounts for the full spectrum of solid - liquid - vapor phase transitions within the framework of a single density order parameter. its equilibrium properties show the most quantitative features to date in pfc modelling of pure substances, and full consistency with thermodynamics in pressure - volume - temperature space is demonstrated. a method to control either the volume or the pressure of the system is also introduced. non - equilibrium simulations show that 2 and 3 - phase growth of solid, vapor and liquid can be achieved, while our formalism also allows for a full range of pressure - induced transformations. this model opens up a new window for the study of pressure driven interactions of condensed phases with vapor, an experimentally relevant paradigm previously missing from phase field crystal theories. | arxiv:1412.7192 |
unsupervised domain adaptation ( uda ) aims to solve the problem of knowledge transfer from labeled source domain to unlabeled target domain. recently, many domain adaptation ( da ) methods use centroid to align the local distribution of different domains, that is, to align different classes. this improves the effect of domain adaptation, but domain differences exist not only between classes, but also between samples. this work rethinks what is the alignment between different domains, and studies how to achieve the real alignment between different domains. previous da methods only considered one distribution feature of aligned samples, such as full distribution or local distribution. in addition to aligning the global distribution, the real domain adaptation should also align the meso distribution and the micro distribution. therefore, this study propose a double classifier method based on high confidence label ( dcp ). by aligning the centroid and the distribution between centroid and sample of different classifiers, the meso and micro distribution alignment of different domains is realized. in addition, in order to reduce the chain error caused by error marking, this study propose a high confidence marking method to reduce the marking error. to verify its versatility, this study evaluates dcp on digital recognition and target recognition data sets. the results show that our method achieves state - of - the - art results on most of the current domain adaptation benchmark datasets. | arxiv:2105.04729 |
we provide perturbative estimates for the one - phase stefan free boundary problem and obtain the regularity of flat free boundaries via a linearization technique in the spirit of the elliptic counterpart established by the first author. | arxiv:2007.08611 |
we investigate manipulation with andreev bound states in josephson quantum point contacts with magnetic scattering. rabi oscillations in the two - level andreev subsystems are excited by resonant driving the direction of magnetic moment of the scatterer, and by modulating the superconducting phase difference across the contact. the andreev level dynamics is manifested by temporal oscillation of the josephson current, accompanied, in the case of magnetic manipulation, also by oscillation of the andreev states spin polarization. the interlevel transitions obey a selection rule that forbids manipulations in a certain region of external parameters, and results from specific properties of andreev bound states in magnetic contacts : 4 $ \ pi $ - periodicity with respect to the superconducting phase, and strong spontaneous spin polarization. | arxiv:0710.0320 |
or right translation by a { \ displaystyle a }. = = = equivalent definition with relaxed axioms = = = the group axioms for identity and inverses may be " weakened " to assert only the existence of a left identity and left inverses. from these one - sided axioms, one can prove that the left identity is also a right identity and a left inverse is also a right inverse for the same element. since they define exactly the same structures as groups, collectively the axioms are not weaker. in particular, assuming associativity and the existence of a left identity e { \ displaystyle e } ( that is, e ⋅ f = f { \ displaystyle e \ cdot f = f } ) and a left inverse f − 1 { \ displaystyle f ^ { - 1 } } for each element f { \ displaystyle f } ( that is, f − 1 ⋅ f = e { \ displaystyle f ^ { - 1 } \ cdot f = e } ), it follows that every left inverse is also a right inverse of the same element as follows. indeed, one has f ⋅ f − 1 = e ⋅ ( f ⋅ f − 1 ) ( left identity ) = ( ( f − 1 ) − 1 ⋅ f − 1 ) ⋅ ( f ⋅ f − 1 ) ( left inverse ) = ( f − 1 ) − 1 ⋅ ( ( f − 1 ⋅ f ) ⋅ f − 1 ) ( associativity ) = ( f − 1 ) − 1 ⋅ ( e ⋅ f − 1 ) ( left inverse ) = ( f − 1 ) − 1 ⋅ f − 1 ( left identity ) = e ( left inverse ) { \ displaystyle { \ begin { aligned } f \ cdot f ^ { - 1 } & = e \ cdot ( f \ cdot f ^ { - 1 } ) & & { \ text { ( left identity ) } } \ \ & = ( ( f ^ { - 1 } ) ^ { - 1 } \ cdot f ^ { - 1 } ) \ cdot ( f \ cdot f ^ { - 1 } ) & & { \ text { ( left inverse ) } } \ \ & = ( f ^ { - 1 } ) ^ { - 1 } \ cdot ( ( f ^ { - 1 } \ cdot f ) \ cdot f ^ { - 1 } ) & & { \ text { ( associativity ) } } \ \ & = | https://en.wikipedia.org/wiki/Group_(mathematics) |
the motion of two contiguous incompressible and viscous fluids is described within the diffuse interface theory by the so - called model h. the system consists of the navier - stokes equations, which are coupled with the cahn - hilliard equation associated to the ginzburg - landau free energy with physically relevant logarithmic potential. this model is studied in bounded smooth domain in r ^ d, d = 2 and d = 3, and is supplemented with a no - slip condition for the velocity, homogeneous neumann boundary conditions for the order parameter and the chemical potential, and suitable initial conditions. we study uniqueness and regularity of weak and strong solutions. in a two - dimensional domain, we show the uniqueness of weak solutions and the existence and uniqueness of global strong solutions originating from an initial velocity u _ 0 in v, namely u _ 0 in h _ 0 ^ 1 such that div u _ 0 = 0. in addition, we prove further regularity properties and the validity of the instantaneous separation property. in a three - dimensional domain, we show the existence and uniqueness of local strong solutions with initial velocity u _ 0 in v. | arxiv:1810.11554 |
we apply the two - scale formulation approach to propose uniformly accurate ( ua ) schemes for solving the nonlinear dirac equation in the nonrelativistic limit regime. the nonlinear dirac equation involves two small scales $ \ varepsilon $ and $ \ varepsilon ^ 2 $ with $ \ varepsilon \ to0 $ in the nonrelativistic limit regime. the small parameter causes high oscillations in time which brings severe numerical burden for classical numerical methods. we transform our original problem as a two - scale formulation and present a general strategy to tackle a class of highly oscillatory problems involving the two small scales $ \ varepsilon $ and $ \ varepsilon ^ 2 $. suitable initial data for the two - scale formulation is derived to bound the time derivatives of the augmented solution. numerical schemes with uniform ( with respect to $ \ varepsilon \ in ( 0, 1 ] $ ) spectral accuracy in space and uniform first order or second order accuracy in time are proposed. numerical experiments are done to confirm the ua property. | arxiv:1605.02475 |
we report observations of the optical counterpart of the long gamma - ray burst ( lgrb ) grb 230812b, and its associated supernova ( sn ) sn 2023pel. the proximity ( $ z = 0. 36 $ ) and high energy ( $ e _ { \ gamma, \ rm { iso } } \ sim 10 ^ { 53 } $ erg ) make it an important event to study as a probe of the connection between massive star core - collapse and relativistic jet formation. with a phenomenological power - law model for the optical afterglow, we find a late - time flattening consistent with the presence of an associated sn. sn 2023pel has an absolute peak $ r $ - band magnitude of $ m _ r = - 19. 46 \ pm 0. 18 $ mag ( about as bright as sn 1998bw ) and evolves on quicker timescales. using a radioactive heating model, we derive a nickel mass powering the sn of $ m _ { \ rm { ni } } = 0. 38 \ pm 0. 01 $ $ \ rm { m _ \ odot } $, and a peak bolometric luminosity of $ l _ { \ rm { bol } } \ sim 1. 3 \ times 10 ^ { 43 } $ $ \ rm { erg } $ $ \ rm { s ^ { - 1 } } $. we confirm sn 2023pel ' s classification as a broad - lined type ic sn with a spectrum taken 15. 5 days after its peak in $ r $ band, and derive a photospheric expansion velocity of $ v _ { \ rm { ph } } = 11, 300 \ pm 1, 600 $ $ \ rm { km } $ $ \ rm { s ^ { - 1 } } $ at that phase. extrapolating this velocity to the time of maximum light, we derive the ejecta mass $ m _ { \ rm { ej } } = 1. 0 \ pm 0. 6 $ $ \ rm { m _ \ odot } $ and kinetic energy $ e _ { \ rm { ke } } = 1. 3 ^ { + 3. 3 } _ { - 1. 2 } \ times10 ^ { 51 } $ $ \ rm { erg } $. we find that grb 230812b / sn 2023pel has sn properties that are mostly consistent with the | arxiv:2310.14397 |
using the black string between two branes as a model of a brane - world black hole, we compute the gravity wave perturbations and identify the features arising from the additional polarizations of the graviton. the standard four - dimensional gravitational wave signal acquires late - time oscillations due to massive modes of the graviton. the fourier transform of these oscillations shows a series of spikes associated with the masses of the kaluza - klein modes, providing in principle a spectroscopic signature of extra dimensions. | arxiv:gr-qc/0408032 |
colossal magnetoresistance and field - induced ferromagnetism are well documented in manganite compounds. since domain wall resistance contributes to magnetoresistance, data on the temperature and magnetic field dependence of the ferromagnetic domain structure are required for a full understanding of the magnetoresistive effect. here we show, using cryogenic magnetic force microscopy, domain structures for the layered manganite la $ _ { 1. 2 } $ sr $ _ { 1. 8 } $ mn $ _ 2 $ o $ _ 7 $ as a function of temperature and magnetic field. domain walls are suppressed close to the curie temperature t $ _ c $, and appear either via the application of a c - axis magnetic field, or by decreasing the temperature further. at temperatures well below t $ _ c $, new domain walls, stable at zero field, can be formed by the application of a c - axis field. magnetic structures are seen also at temperatures above t $ _ c $ : these features are attributed to inclusions of additional ruddleston - popper manganite phases. low - temperature domain walls are nucleated by these ferromagnetic inclusions. | arxiv:1310.0258 |
this article present a concise estimate of upper and lower bound on the cardinality containing shortest vector in a lattice reduced by block korkin - zolotarev method ( bkz ) for different value of the block size. paper show how density affect to this cardinality, in form of the ratio of shortest vector size and sucessive minimal. moreover we give upper estimate of cardinality for critical and goldstein - mayer lattices. | arxiv:1302.4062 |
a comparative study between pbtio $ _ 3 $, pbzro $ _ 3 $, and the solid solution pbzr $ _ { 0. 5 } $ ti $ _ { 0. 5 } $ o $ _ 3 $ is performed on the soft mode lattice dynamics within the first brillouin zone. we consider the six unique b - site orderings for pbzr $ _ { 0. 5 } $ ti $ _ { 0. 5 } $ o $ _ 3 $ representable within the 2 $ \ times $ 2 $ \ times $ 2 primitive perovskite supercell as well as the virtual crystal approximation ( vca ) to extract the phonon dispersion relations of a high - symmetry cubic - constrained form using density functional perturbation theory. we find that the most unstable modes in the rock - salt ordered structure and the vca, like pure pbzro $ _ 3 $, are antiferrodistortive ( afd ) whilst lower symmetry arrangements are dominated by $ \ gamma $ - point ferroelectric ( fe ) instabilities like pure pbtio $ _ 3 $. despite similarities in the phonon dispersion relations between the rock - salt ordered supercell and the vca, the character of modes at high symmetry points are found to be different. in particular, the a $ ^ { 0 } $ a $ ^ { 0 } $ c $ ^ { - } $ & a $ ^ { 0 } $ a $ ^ { 0 } $ c $ ^ { + } $ afd instabilities of the rock - salt ordering are replaced with a $ ^ { - } $ b $ ^ { - } $ c $ ^ { - } $ & a $ ^ { + } $ b $ ^ { + } $ c $ ^ { + } $ instabilities within the vca. such a rotation pattern is not seen in any of the supercell - based calculations thus serving as a quantitative example of the inability of the method to represent accurately local structural distortions. single modes are found exhibiting dual order parameters. at the zone centre, some arrangements show mixed fe & antipolar soft modes ( due to pb motion tansverse to the polar axis ) and at long wavelengths all arrangements have soft modes of a mixed antipolar & afd character. these are described with direct analysis of the eigendisplacements. | arxiv:1910.01685 |
regional network for education and training in nuclear technology ( star - net ) https : / / www. iaea. org / services / networks / star - net world nuclear association world nuclear transport institute = = see also = = = = references = = = = further reading = = ash, milton, " nuclear reactor kinetics ", mcgraw - hill, ( 1965 ) cravens, gwyneth. power to save the world ( 2007 ) gowing, margaret. britain and atomic energy, 1939 – 1945 ( 1964 ). gowing, margaret, and lorna arnold. independence and deterrence : britain and atomic energy, vol. i : policy making, 1945 – 52 ; vol. ii : policy execution, 1945 – 52 ( london, 1974 ) johnston, sean f. " creating a canadian profession : the nuclear engineer, 1940 – 68, " canadian journal of history, winter 2009, vol. 44 issue 3, pp 435 – 466 johnston, sean f. " implanting a discipline : the academic trajectory of nuclear engineering in the usa and uk, " minerva, 47 ( 2009 ), pp. 51 – 73 = = external links = = electric generation from commercial nuclear power hacettepe university department of nuclear engineering nuclear engineering international magazine nuclear safety info resources nuclear science and engineering technical journal science and technology of nuclear installation open - access journal | https://en.wikipedia.org/wiki/Nuclear_engineering |
this paper focuses on the stability of solutions for a velocity - tracking problem associated with the two - dimensional navier - stokes equations. the considered optimal control problem does not possess any regularizer in the cost, and hence bang - bang solutions can be expected. we investigate perturbations that account for uncertainty in the tracking data and the initial condition of the state, and analyze the convergence rate of solutions when the original problem is regularized by the tikhonov term. the stability analysis relies on the h \ " older subregularity of the optimality mapping, which stems from the necessary conditions of the problem. | arxiv:2307.07283 |
we describe a method for recovering the irradiance underlying a collection of images corrupted by atmospheric turbulence. since supervised data is often technically impossible to obtain, assumptions and biases have to be imposed to solve this inverse problem, and we choose to model them explicitly. rather than initializing a latent irradiance ( " template " ) by heuristics to estimate deformation, we select one of the images as a reference, and model the deformation in this image by the aggregation of the optical flow from it to other images, exploiting a prior imposed by central limit theorem. then with a novel flow inversion module, the model registers each image to the template but without the template, avoiding artifacts related to poor template initialization. to illustrate the robustness of the method, we simply ( i ) select the first frame as the reference and ( ii ) use the simplest optical flow to estimate the warpings, yet the improvement in registration is decisive in the final reconstruction, as we achieve state - of - the - art performance despite its simplicity. the method establishes a strong baseline that can be further improved by integrating it seamlessly into more sophisticated pipelines, or with domain - specific methods if so desired. | arxiv:2405.03662 |
a consistent description of charged many - tachyon fermi system is developed. tachyons and antitachyons have the same chemical potential \ mu + = \ mu - because the axial coupling constant g + = g - is invariant under the charge conjugation, in contrast to reversion of the electric charge e + = - e -. the axial density n5 = < \ psi ^ \ gamma 5 \ psi > is incorporated in the thermodynamical functions instead of < \ psi ^ \ psi > which is not associated with any conserved quantity. the number of tachyons and antitachyons are undefined but it is possible to estimate their difference and establish a link between the total electric charge density $ en $ and $ n5 $. | arxiv:1204.1370 |
we report a new algorithm to generate laplacian growth patterns using iterated conformal maps. the difficulty of growing a complete layer with local width proportional to the gradient of the laplacian field is overcome. the resulting growth patterns are compared to those obtained by the best algorithms of direct numerical solutions. the fractal dimension of the patterns is discussed. | arxiv:cond-mat/0305521 |
quasiparticle interference imaging ( qpi ) offers insight into the band structure of quantum materials from the fourier transform of local density of states ( ldos ) maps. their acquisition with a scanning tunneling microscope is traditionally tedious due to the large number of required measurements that may take several days to complete. the recent demonstration of sparse sampling for qpi imaging showed how the effective measurement time could be fundamentally reduced by only sampling a small and random subset of the total ldos. however, the amount of required sub - sampling to faithfully recover the qpi image remained a recurring question. here we introduce an adaptive sparse sampling ( ass ) approach in which we gradually accumulate sparsely sampled ldos measurements until a desired quality level is achieved via compressive sensing recovery. the iteratively measured random subset of the ldos can be interleaved with regular topographic images that are used for image registry and drift correction. these reference topographies also allow to resume interrupted measurements to further improve the qpi quality. our ass approach is a convenient extension to quasiparticle interference imaging that should remove further hesitation in the implementation of sparse sampling mapping schemes. | arxiv:2204.04475 |
the spherical model for spins describes ferromagnetic phase transitions well, but it fails at low temperatures. a quantum version of the spherical model is proposed. it does not induce qualitative changes near the phase transition. however, it produces a physical low temperature behavior. the entropy is non - negative. model parameters can be adapted to the description of real quantum spins. several applications are discussed. zero - temperature quantum phase transitions are analyzed for a ferromagnet and a spin glass in a transversal field. their crossover exponents are presented. | arxiv:cond-mat/9408055 |
we show that short - range interactions between the fundamental particles in the universe can drive a period of accelerated expansion. this description fits the early universe. in the present day universe, if one postulates short - range interactions or a sort of " shielded gravity ", the picture may repeat. | arxiv:gr-qc/0505105 |
integral simplicial volume is a homotopy invariant of oriented closed connected manifolds, defined as the minimal weighted number of singular simplices needed to represent the fundamental class with integral coefficients. we show that odd - dimensional spheres are the only manifolds with integral simplicial volume equal to 1. consequently, we obtain an elementary proof that, in general, the integral simplicial volume of ( triangulated ) manifolds is not computable. | arxiv:1509.00204 |
aims. we demonstrate the high multiplex advantage of crowded field 3d spectroscopy using the new integral field spectrograph muse by means of a spectroscopic analysis of more than 12, 000 individual stars in the globular cluster ngc 6397. methods. the stars are deblended with a psf fitting technique, using a photometric reference catalogue from hst as prior, including relative positions and brightnesses. this catalogue is also used for a first analysis of the extracted spectra, followed by an automatic in - depth analysis using a full - spectrum fitting method based on a large grid of phoenix spectra. results. with 18, 932 spectra from 12, 307 stars in ngc 6397 we have analysed the largest sample so far available for a single globular cluster. we derived a mean radial velocity of vrad = 17. 84 + - 0. 07 km / s and a mean metallicity of [ fe / h ] = - 2. 120 + - 0. 002, with the latter seemingly varying with temperature for stars on the rgb. we determine t _ eff and [ fe / h ] from the spectra, and log g from hst photometry. this is the first very comprehensive hrd for a globular cluster based on the analysis of several thousands of stellar spectra, ranging from the main sequence to the tip of the rgb. furthermore, two interesting objects were identified with one being a post - agb star and the other a possible millisecond - pulsar companion. | arxiv:1602.01649 |
observation shows that nebular emission, molecular gas, and young stars in giant galaxies are associated with rising x - ray bubbles inflated by radio jets launched from nuclear black holes. we propose a model where molecular clouds condense from low entropy gas caught in the updraft of rising x - ray bubbles. the low entropy gas becomes thermally unstable when it is lifted to an altitude where its cooling time is shorter than the time required to fall to its equilibrium location in the galaxy i. e., t _ c / t _ i < 1. the infall speed of a cloud is bounded by the lesser of its free - fall and terminal speeds, so that the infall time here can exceed the the free - fall time by a significant factor. this mechanism is motivated by alma observations revealing molecular clouds lying in the wakes of rising x - ray bubbles with velocities well below their free - fall speeds. our mechanism would provide cold gas needed to fuel a feedback loop while stabilizing the atmosphere on larger scales. the observed cooling time threshold of ~ 5x 10 ^ 8 yr - - - the clear - cut signature of thermal instability and the onset of nebular emission and star formation - - - may result from the limited ability of radio bubbles to lift low entropy gas to altitudes where thermal instabilities can ensue. outflowing molecular clouds are unlikely to escape, but instead return to the central galaxy in a circulating flow. we contrast our mechanism to precipitation models where the minimum value of t _ c / t _ ff < 10 triggers thermal instability, which we find to be inconsistent with observation. | arxiv:1604.04629 |
we address the problem of two pairs of fermions living on an arbitrary number of single particle levels of a potential well ( mean field ) and interacting through a pairing force. the associated solutions of the richardson ' s equations are classified in terms of a number $ v _ l $, which reduces to the seniority $ v $ in the limit of large values of the pairing strength $ g $ and yields the number of pairs not developing a collective behaviour, their energy remaining finite in the $ g \ to \ infty $ limit. we express analytically, through the moments of the single particle levels distribution, the collective mode energy and the two critical values $ g _ { \ rm cr } ^ { + } $ and $ g _ { \ rm cr } ^ { - } $ of the coupling which can exist on a single particle level with no pair degeneracy. notably $ g _ { \ rm cr } ^ { + } $ and $ g _ { \ rm cr } ^ { - } $ merge when the number of single particle levels goes to infinity, where they coincide with the $ g _ { \ rm cr } $ ( when it exists ) of a one pair system, not envisioned by the richardson theory. in correspondence of $ g _ { \ rm cr } $ the system undergoes a transition from a mean field to a pairing dominated regime. we finally explore the behaviour of the excitation energies, wave functions and pair transfer amplitudes finding out that the former, for $ g > g _ { \ rm cr } ^ { - } $, come close to the bcs predictions, whereas the latter display a divergence at $ g _ { \ rm cr } $, signaling the onset of a long range off - diagonal order in the system. | arxiv:nucl-th/0306062 |
we report in situ neutron background measurements at the kuo - sheng reactor neutrino laboratory ( ksnl ) by a hybrid neutron detector ( hnd ) with a data size of 33. 8 days under identical shielding configurations as during the neutrino physics data taking. the hnd consists of bc - 501a liquid and bc - 702 phosphor powder scintillation neutron detectors, which is sensitive to both fast and thermal neutrons, respectively. neutron - induced events for the two channels are identified and differentiated by pulse shape analysis, such that background of both are simultaneously measured. the fast neutron fluxes are derived by an iterative unfolding algorithm. neutron induced background in the germanium detector under the same fluxes, both due to cosmic - rays and ambient radioactivity, are derived and compared with the measurements. the results are valuable to background understanding of the neutrino data at the ksnl. in particular, neutron - induced background events due to ambient radioactivity as well as from reactor operation are negligible compared to intrinsic cosmogenic activity and ambient $ \ gamma $ - activity. the detector concept and analysis procedures are applicable to neutron background characterization in similar rare - event experiments. | arxiv:1803.09929 |
spatial orientation is essential for people to effectively navigate and interact with the environment in everyday life. with age - related cognitive decline, providing vr locomotion techniques with better spatial orientation performance for older adults becomes important. such advancements not only make vr more accessible to older adults but also enable them to reap the potential health benefits of vr technology. natural motion - based locomotion has been shown to be effective in enhancing younger users ' performance in vr navigation tasks that require spatial orientation. however, there is a lack of understanding regarding the impact of natural motion - based locomotion on spatial orientation for older adults in vr. to address this gap, we selected the silvercycling system, a vr bike - based locomotion technique that we developed, as a representative of natural motion - based locomotion, guided by findings from our pilot study. we conducted a user study with 16 older adults to compare silvercycling with the joystick - based controller. the findings suggest silvercycling ' s potential to significantly enhance spatial orientation in the open - road urban environment for older adults, offering a better user experience. based on our findings, we identify key factors influencing spatial orientation and propose design recommendations to make vr locomotion more accessible and user - friendly for older adults. | arxiv:2407.06846 |
we compare higgs inflation in the metric and palatini formulations of general relativity, with loop corrections are treated in a simple approximation. we consider higgs inflation on the plateau, at a critical point, at a hilltop and in a false vacuum. in the last case there are only minor differences. otherwise we find that in the palatini formulation the tensor - to - scalar ratio is consistently suppressed, spanning the range $ 1 \ times10 ^ { - 13 } < r < 7 \ times10 ^ { - 5 } $, compared to the metric case result $ 2 \ times10 ^ { - 5 } < r < 0. 2 $. even when the values of $ n _ s $ and $ r $ overlap, the running and running of the running are different in the two formulations. therefore, if higgs is the inflaton, inflationary observables can be used to distinguish between different gravitational degrees of freedom, in this case to determine whether the connection is an independent variable. non - detection of $ r $ in foreseeable future observations would not rule out higgs inflation, only its metric variant. we conclude that in order to fix the theory of higgs inflation, not only the particle physics uv completion but also the gravitational degrees of freedom have to be explicated. | arxiv:1709.07853 |
in a previous work lazarian and pogosyan suggested a technique to extract velocity and density statistics, of interstellar turbulence, by means of analysing statistics of spectral line data cubes. in this paper we test that technique, by studying the effect of correlation between velocity and density fields, providing a systematic analysis of the uncertainties arising from the numerics, and exploring the effect of a linear shear. we make use of both compressible mhd simulations and synthetic data to emulate spectroscopic observations and test the technique. with the same synthetic spectroscopic data, we also studied anisotropies of the two point statistics and related those anisotropies with the magnetic field direction. this presents a new technique for magnetic field studies. the results show that the velocity and density spectral indices measured are consistent with the analytical predictions. we identified the dominant source of error with the limited number of data points along a given line of sight. we decrease this type of noise by increasing the number of points and by introducing gaussian smoothing. we argue that in real observations the number of emitting elements is essentially infinite and that source of noise vanishes. | arxiv:astro-ph/0210159 |
the quark - gluon plasma ( qgp ) is an exotic phase of matter, composed of deconfined quarks and gluons and is briefly created in heavy - ion collisions ( hic ) at the lhc and at the rhic. high - energy, self - collimated structures of final - state particles also created in hic, called jets, probe the qgp, piercing through it on their way to the particle detector. quantum field theory at finite temperature or thermal field theory, is then an extremely powerful tool, capable of analytically quantifying how such a high - energy object interacts with a weakly coupled thermal bath. in this thesis, we work towards the computation of corrections to two quantities, which dictate how jets are quenched by the qgp. the first being the transverse momentum broadening coefficient, which describes how the jet diffuses in transverse momentum space through its interaction with the medium. we focus on the computation of logarithmically enhanced corrections, carefully showing how the thermal scale affects the logarithmic phase space. the second is the asymptotic mass, which can be thought of as a shift in the jet dispersion relation as it undergoes forward scattering with the medium. we complete a matching calculation, which rids the mass ' classical corrections of any unphysical divergences, while also beginning the completion of its full two - loop, quantum corrections. | arxiv:2311.04988 |
system services and resources in android are accessed through ipc based mechanisms. previous research has demonstrated that they are vulnerable to the denial - of - service attack ( dos attack ). for instance, the jni global reference ( jgr ), which is widely used by system services, can be exhausted to cause the system reboot ( hence the name jgre attack ). even though the android team tries to fix the problem by enforcing security checks, we find that it is still possible to construct a jgr exhaustion dos attack in the latest android system. in this paper, we propose a new jgr exhaustion dos attack, which is effective in different android versions, including the latest one ( i. e., android 10 ). specifically, we developed jgreanalyzer, a tool that can systematically detect jgr vulnerable services apis via a call graph analysis and a forwarding reachability analysis. we applied this tool to different android versions and found multiple vulnerabilities. in particular, among 148 system services in android 10, 12 of them have 21 vulnerabilities. among them, 9 can be successfully exploited without any permissions. we further analyze the root cause of the vulnerabilities and propose a new defense to mitigate the jgre attack by restricting resource consumption via global reference counting. | arxiv:2405.00526 |
basic synchronous flooding proceeds in rounds. given a finite undirected ( network ) graph $ g $, a set of sources $ i \ subseteq g $ initiate flooding in the first round by every node in $ i $ sending the same message to all of its neighbours. in each subsequent round, nodes send the message to all of their neighbours from which they did not receive the message in the previous round. flooding terminates when no node in $ g $ sends a message in a round. the question of termination has not been settled - rather, non - termination is implicitly assumed to be possible. we show that flooding terminates on every finite graph. in the case of a single source $ g _ 0 $, flooding terminates in $ e $ rounds if $ g $ is bipartite and $ j $ rounds with $ e < j \ leq e + d + 1 $ otherwise, where $ e $ and $ d $ are the eccentricity of $ g _ 0 $ and diameter of $ g $ respectively. for communication / broadcast to all nodes, this is asymptotically time optimal and obviates the need for construction and maintenance of spanning structures. we extend to dynamic flooding initiated in multiple rounds with possibly multiple messages. the cases where a node only sends a message to neighbours from which it did not receive { \ it any } message in the previous round, and where a node sends some highest ranked message to all neighbours from which it did not receive { \ it that } message in the previous round, both terminate. all these cases also hold if the network graph loses edges over time. non - terminating cases include asynchronous flooding, flooding where messages have fixed delays at edges, cases of multiple - message flooding and cases where the network graph acquires edges over time. | arxiv:2009.05776 |
we examine the dynamic and geometric phases of the electron in quantum mechanics using hestenes ' spacetime algebra formalism. first the standard dynamic phase formula is translated into the spacetime algebra. we then define new formulas for the dynamic and geometric phases that can be used in hestenes ' formalism. | arxiv:quant-ph/0111101 |
we propose and implement a microwave photonic multi - mode injection - locked frequency divider ( ilfd ) with a wide frequency operational range based on an optoelectronic oscillator ( oeo ). in the oeo, a mach - zehnder modulator ( mzm ) and a photodetector ( pd ) are employed to construct a frequency multiplier to achieve an n - 1 times frequency multiplication, which is then mixed with an external injection signal at an electrical mixer in the oeo loop. by adjusting the round - trip gain and time delay of the oeo loop, a radio frequency ( rf ) signal with a frequency that is 1 / n that of the injection signal is generated, thus n times frequency division is achieved. theoretical analysis and experimental verification are conducted to evaluate the effectiveness of the proposed ilfd. the results demonstrate that the system can divide a rf signal from 2. 6 to 20. 8 ghz to 1. 3 to 1. 95 ghz with different frequency division factors ranging from 2 to 13. a significant improvement in phase noise of 35. 11 db is also obtained at a frequency offset of 100 khz when the frequency division factor is 13. | arxiv:2409.01158 |
the discovery of causal relationships from observed data has attracted significant interest from disciplines such as economics, social sciences, epidemiology, and biology. in practical applications, considerable knowledge of the underlying systems is often unavailable, and real data are often associated with nonlinear causal structures, which make the direct use of most conventional causality analysis methods difficult. this study proposes a novel quantum peter - clark ( qpc ) algorithm for causal discovery that does not assume any underlying model structures. based on the independence conditional tests in a class of reproducing kernel hilbert spaces characterized by quantum circuits, the proposed qpc algorithm can explore causal relationships from the observed data drawn from arbitrary distributions. we conducted systematic experiments on fundamental graph parts of causal structures, demonstrating that the qpc algorithm exhibits a significantly better performance, particularly with smaller sample sizes compared to its classical counterpart. furthermore, we proposed a novel optimization approach based on kernel target alignment ( kta ) for determining hyperparameters of quantum kernels. this method effectively reduced the risk of false positives in causal discovery, enabling more reliable inference. our theoretical and experimental results demonstrate that the proposed quantum algorithm can empower classical algorithms for robust and accurate inference in causal discovery, supporting them in regimes where classical algorithms typically fail. additionally, the effectiveness of this method was validated using the boston housing dataset as a real - world application. these findings demonstrate the new potential of quantum circuit - based causal discovery methods in addressing practical challenges, particularly in small - sample scenarios where traditional approaches have shown limitations. | arxiv:2501.05007 |
a criterion for elements of free zinbiel algebras to be lie or jordan is established. this criterion is used in studying speciality problems of tortkara algebras. we construct a base of free special tortkara algebras. furthermore, we prove analogues of classical cohn ' s and shirshov ' s theorems for tortkara algebras. | arxiv:1809.10550 |
graphics processing units ( gpus ) are high performance co - processors originally intended to improve the use and quality of computer graphics applications. once, researchers and practitioners noticed the potential of using gpu for general purposes, gpus applications have been extended from graphics applications to other fields. the main objective of this paper is to evaluate the impact of using gpu in solution of the transient diffusion type equation by parallel and stable group explicit finite difference method and encourage the researchers in this field to immigrate from implementing their algorithms in cpu to the gpu emerging world. for comparing them, we implemented the method in both gpu and cpu ( multi - core ) programming context. moreover, we proposed an optimal synchronization arrangement for the implementation pseudo - code. also, the interrelation of gpu parallel programming and initializing the algorithm variables were discussed, taking advantage of numerical experiences. the gpu - approach results are faster than those obtained from a much expensive parallel 8 - thread cpu - based programming. the gpu used in this paper, is an ordinary old laptop gpu ( gt 335m, launched at 2010 ) and is accessible for everyone and the newer generations of gpu ( as discussed in paper ) have even more performance priority over the similar - price gpus. then, the results are expected to encourage the entire research society to take advantage of gpus and improve the time efficiency of their studies. | arxiv:1310.3422 |
a bachelor of engineering ( be or beng ) or a bachelor of science in engineering ( bsc ( eng ) or bse ) is an undergraduate academic degree awarded to a college graduate majoring in an engineering discipline at a higher education institution. in the united kingdom, a bachelor of engineering degree program is accredited by one of the engineering council ' s professional engineering institutions as suitable for registration as an incorporated engineer or chartered engineer with further study to masters level. in canada, a degree from a canadian university can be accredited by the canadian engineering accreditation board ( ceab ). alternatively, it might be accredited directly by another professional engineering institution, such as the us - based institute of electrical and electronics engineers ( ieee ). the bachelor of engineering contributes to the route to chartered engineer ( uk ), registered engineer or licensed professional engineer and has been approved by representatives of the profession. similarly bachelor of engineering ( be ) and bachelor of technology ( b. tech ) in india is accredited by all india council for technical education. most universities in the united states and europe award bachelor ' s degrees in engineering through various names. a less common and possibly the oldest variety of the degree in the english - speaking world is baccalaureus in arte ingeniaria ( b. a. i. ), a latin name meaning bachelor in the art of engineering. here baccalaureus in arte ingeniaria implies excellence in carrying out the ' art ' or ' function ' of an engineer. some south african universities refer to their engineering degrees as b. ing. ( baccalaureus ingenieurswese, in afrikaans ). = = engineering fields = = a bachelor of engineering degree will usually be undertaken in one field of engineering, which is sometimes noted in the degree postnominals, as in b. e., b. ae. ( aero ), or b. eng ( elec ). common fields for the bachelor of engineering degree include the following fields : aerospace engineering agricultural engineering architectural engineering automotive engineering biological engineering — including biochemical, biomedical, biosystems and biomolecular chemical engineering — deals with the process of converting raw materials or chemicals into more useful or valuable forms clean technology — use energy, water and raw materials and other inputs more efficiently and productively. create less waste or toxicity and deliver equal or superior performance. computer engineering computer science and engineering civil engineering — a wide - ranging field, including building engineering, civil engineering, construction engineering, industrial, manufacturing, mechanical, materials and control engineering electrical and computer engineering / electronic engineering — very diverse | https://en.wikipedia.org/wiki/Bachelor_of_Engineering |
the dissolution time ( t _ dis ) of clusters in a tidal field does not scale with the ` ` classical ' ' expression for the relaxation time. first, the scaling with n, and hence cluster mass, is shallower due to the finite escape time of stars. secondly, the cluster half - mass radius is of little importance. this is due to a balance between the relative tidal field strength and internal relaxation, which have an opposite effect on t _ dis, but of similar magnitude. when external perturbations, such as encounters with giant molecular clouds ( gmc ) are important, t _ dis for an individual cluster depends strongly on radius. the mean dissolution time for a population of clusters, however, scales in the same way with mass as for the tidal field, due to the weak dependence of radius on mass. the environmental parameters that determine t _ dis are the tidal field strength and the density of molecular gas. we compare the empirically derived t _ dis of clusters in six galaxies to theoretical predictions and argue that encounters with gmcs are the dominant destruction mechanism. finally, we discuss a number of pitfalls in the derivations of t _ dis from observations, such as incompleteness, with the cluster system of the smc as particular example. | arxiv:0710.2374 |
recent advances in image - based human pose estimation make it possible to capture 3d human motion from a single rgb video. however, the inherent depth ambiguity and self - occlusion in a single view prohibit the recovery of as high - quality motion as multi - view reconstruction. while multi - view videos are not common, the videos of a celebrity performing a specific action are usually abundant on the internet. even if these videos were recorded at different time instances, they would encode the same motion characteristics of the person. therefore, we propose to capture human motion by jointly analyzing these internet videos instead of using single videos separately. however, this new task poses many new challenges that cannot be addressed by existing methods, as the videos are unsynchronized, the camera viewpoints are unknown, the background scenes are different, and the human motions are not exactly the same among videos. to address these challenges, we propose a novel optimization - based framework and experimentally demonstrate its ability to recover much more precise and detailed motion from multiple videos, compared against monocular motion capture methods. | arxiv:2008.07931 |
kinetic monte carlo ( kmc ) is an efficient method for studying diffusion. a limiting factor to the accuracy of kmc is the number of different migration events allowed in the simulation. each event requires its own migration energy barrier. the calculation of these barriers may be unfeasibly expensive. in this article we present a data set of migration barriers on for nearest - neighbour jumps on the cu surfaces, calculated with the nudged elastic band ( neb ) method and the tethering force approach. we used the data to train artifcial neural networks ( ann ) in order to predict the migration barriers for arbitrary nearest - neighbour cu jumps. the trained anns are also included in the article. the data is hosted by the csc ida storage service. | arxiv:1806.03062 |
based on the solution formula method, a series of one - step fully - discrete schemes, such as fweno / full - weno has been proposed. storing the by - products conservative variables at the half points ( grid center ) and using them as interpolation information to construct high - order schemes, we obtain a new class of one - step compact fully - discrete schemes. the new scheme can be associate with various non - oscillatory strategies. this paper takes state - of - the - art weno - js method as an example and proposes a family of compact fully - discrete weno scheme. detailed analysis is conducted on accuracy, errors, computational cost, efficiency and their connection with hermite interpolation. meanwhile, we design a new entropy flux linearization strategy for euler equations to enhance its robustness, and also develop a multi - dimensional method for this compact fully - discrete framework. due to the new scheme is one - step and utilizes stored by - products information for interpolation, it has a significant advantage in efficiency. for one - dimensional euler equations, compared to the original fweno, the computational cost only increases by 20 - 40 %, while is approximately one - third of weno + rk3. for two - dimensional case, a new special dimension - by - dimension strategy is applied. although there is an additional computing cost, numerical experiments show that the new scheme only needs about 1 / 10 to 1 / 13 cost of that for weno + rk3 when obtaining similar or even better resolution results, indicating that the new scheme is more efficient than semi - discrete schemes based on rk methods. | arxiv:2408.10223 |
we propose how to generate genuine multipartite entanglement of electron spin qubits in a chain of quantum dots using the naturally available single - qubit rotations and two - qubit heisenberg exchange interaction in the system. we show that the minimum number of required operations to generate entangled states of the ghz -, cluster and w - type scales linearly with the number of qubits and estimate the fidelities of the generated entangled cluster states. as the required single and two - qubit operations have recently been realized, our proposed scheme opens the way for experimental investigation of multipartite entanglement with electron spin qubits. | arxiv:0707.1267 |
given a presentation for a rack $ \ mathcal r $, we define a process which systematically enumerates the elements of $ \ mathcal r $. the process is modeled on the systematic enumeration of cosets first given by todd and coxeter. this generalizes and improves the diagramming method for $ n $ - quandles introduced by winker. we provide pseudocode that is similar to that given by holt for the todd - coxeter process. we prove that the process terminates if and only if $ \ mathcal r $ is finite, in which case, the procedure outputs an operation table for the finite rack. we conclude with an application to knot theory. | arxiv:1707.01519 |
the computer revolution has been driven by a sustained increase of computational speed of approximately one order of magnitude ( a factor of ten ) every five years since about 1950. in natural sciences this has led to a continuous increase of the importance of computer simulations. major enabling techniques are markov chain monte carlo ( mcmc ) and molecular dynamics ( md ) simulations. this article deals with the mcmc approach. first basic simulation techniques, as well as methods for their statistical analysis are reviewed. afterwards the focus is on generalized ensembles and biased updating, two advanced techniques, which are of relevance for simulations of biomolecules, or are expected to become relevant with that respect. in particular we consider the multicanonical ensemble and the replica exchange method ( also known as parallel tempering or method of multiple markov chains ). | arxiv:0709.0538 |
we propose a simple discrete stochastic model for calcium dynamics in living cells. specifically, the calcium concentration distribution is assumed to give rise to a set of probabilities for the opening / closing of channels which release calcium thereby changing those probabilities. we study this model in one dimension, analytically in the mean - field limit of large number of channels per site n, and numerically for small n. as the number of channels per site is increased, the transition from a non - propagating region of activity to a propagating one changes in nature from one described by directed percolation to that of deterministic depinning in a spatially discrete system. also, for a small number of channels a propagating calcium wave can leave behind a novel fluctuation - driven state, in a parameter range where the limiting deterministic model exhibits only single pulse propagation. | arxiv:patt-sol/9910001 |
while the dynamics of dimers and polymer chains in a viscous solvent is well understood within the celebrated rouse model, the effect of an external magnetic field on the dynamics of a charged chain is much less understood. here we generalize the rouse model for a charged dimer to include the effect of an external magnetic field. our analytically solvable model allows a fundamental insight into the magneto - generated dynamics of the dimer in the overdamped limit as induced by the lorentz - force. surprisingly, for a dimer of oppositely charged particles, we find an enormous enhancement of the dynamics of the dimer center which exhibits even a transient superballistic behavior. this is highly unusual in an overdamped system for there is neither inertia nor any internal or external driving. we attribute this to a significant translation and rotation coupling due to the lorentz force. we also find that magnetic field reduces the mobility of a dimer along its orientation and its effective rotational diffusion coefficient. in principle, our predictions can be tested by experiments with colloidal particles and complex plasmas. | arxiv:2206.14883 |
by means of monte carlo simulations on a kinetic model, we demonstrate that the efficiency of a photoinduced phase change can in general be enhanced drastically by using a superstructure of an appropriate combination of two components. this is due to the accelerated nucleation of converted domains in the structural blocks relatively close to local instability. the present mechanism provides a general guideline on the design of photocontrollable materials with potential applications for memory and storage devices. | arxiv:cond-mat/0202224 |
the aim of this paper is to describe the origin, first solutions, further progress, the state of art, and a new ansatz in the treatment of a problem dating back to the 1920 ' s, which still has not found a satisfactory solution and deserves to be better known. | arxiv:1102.3383 |
the mechanical performance of metallic metamaterials with 3 - dimensional solid frames is typically a combination of the geometrical effect ( " architecture " ) and the characteristic size effects of the base material ( " microstructure " ). in this study, for the first time, the temperature - and rate - dependent mechanical response of copper microlattices has been investigated. the microlattices were fabricated via a localized electrodeposition in liquid ( lel ) process which enables high - precision additive manufacturing of metal at the micro - scale. the metal microlattices possess a unique microstructure with micron sized grains that are rich with randomly oriented growth twins and near - ideal nodal connectivity. importantly, copper microlattices exhibited unique temperature ( - 150 and 25 degree c ) and strain rate ( 0. 001 ~ 100 s - 1 ) dependent deformation behavior during in situ micromechanical testing. systematic compression tests of fully dense copper micropillars, equivalent in diameter and length to the struts of the microlattice at comparable extreme loading conditions, allow us to investigate the intrinsic deformation mechanism of copper. combined with the post - mortem microstructural analysis, substantial shifts in deformation mechanisms depending on the temperature and strain rate were revealed. on the one hand, at room temperature ( 25 degree c ), dislocation slip based plastic deformation occurs and leads to a localized deformation of the micropillars. on the other hand, at cryogenic temperature ( - 150 degree c ), mechanical twinning occurs and leads to relatively homogeneous deformation of the micropillars. based on the intrinsic deformation mechanisms of copper, the temperature and strain rate dependent deformation behavior of microlattices could be explained. | arxiv:2311.14018 |
studies on emotion recognition ( er ) show that combining lexical and acoustic information results in more robust and accurate models. the majority of the studies focus on settings where both modalities are available in training and evaluation. however, in practice, this is not always the case ; getting asr output may represent a bottleneck in a deployment pipeline due to computational complexity or privacy - related constraints. to address this challenge, we study the problem of efficiently combining acoustic and lexical modalities during training while still providing a deployable acoustic model that does not require lexical inputs. we first experiment with multimodal models and two attention mechanisms to assess the extent of the benefits that lexical information can provide. then, we frame the task as a multi - view learning problem to induce semantic information from a multimodal model into our acoustic - only network using a contrastive loss function. our multimodal model outperforms the previous state of the art on the usc - iemocap dataset reported on lexical and acoustic information. additionally, our multi - view - trained acoustic network significantly surpasses models that have been exclusively trained with acoustic features. | arxiv:1906.10198 |
bohmian mechanics is a nonlocal hidden - variable interpretation of quantum theory which predicts that particles follow deterministic trajectories in spacetime. historically, the study of bohmian trajectories has mainly been restricted to nonrelativistic regimes due to the widely held belief that the theory is incompatible with special relativity. here we derive expressions for the relativistic velocity and spacetime trajectories of photons in a michelson - sagnac - type interferometer. the trajectories satisfy quantum - mechanical continuity and the relativistic velocity addition rule. our new velocity equation is operationally defined in terms of weak measurements of momentum and energy. we finally propose a modified alcubierre metric which could give rise to these trajectories within the paradigm of general relativity. | arxiv:2108.05169 |
we show that the automorphism group of the complex of pants decompositions for a surface is isomorphic to the mapping class group for that surface. | arxiv:math/0201319 |
we consider the strong solution of the 2d navier - stokes equations in a torus subject to an additive noise. we implement a fully implicit time numerical scheme and a finite element method in space. we prove that the rate of convergence of the schemes is $ \ eta \ in [ 0, 1 / 2 ) $ in time and 1 in space. let us mention that the coefficient $ \ eta $ is equal to the time regularity of the solution with values in $ \ ll ^ 2 $. our method relies on the existence of finite exponential moments for both the solution and its time approximation. our main idea is to use a discrete gronwall lemma for the error estimate without any localization. | arxiv:2102.01162 |
this work presents proofs for hurewicz ' s and pawlikowski ' s theorems about topological games in the context of lattices, in which one cannot argue with points. | arxiv:2102.12901 |
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