the hydrogen moderated self - regulating nuclear power module, a reactor that uses uranium hydride as a moderator and fuel, similar in chemistry and safety to the triga, also possesses these extreme safety and stability characteristics, and has attracted a good deal of interest in recent times. the liquid fluoride thermal reactor is designed to naturally have its core in a molten state, as a eutectic mix of thorium and fluorine salts. as such, a molten core is reflective of the normal and safe state of operation of this reactor type. in the event the core overheats, a metal plug will melt, and the molten salt core will drain into tanks where it will cool in a non - critical configuration. since the core is liquid, and already melted, it cannot be damaged. advanced liquid metal reactors, such as the u. s. integral fast reactor and the russian bn - 350, bn - 600, and bn - 800, all have a coolant with very high heat capacity, sodium metal. as such, they can withstand a loss of cooling without scram and a loss of heat sink without scram, qualifying them as inherently safe. soviet union - designed reactors soviet designed rbmks, found only in russia and the cis and now shut down everywhere except russia, do not have containment buildings, are naturally unstable ( tending to dangerous power fluctuations ), and also have eccs systems that are considered grossly inadequate by western safety standards. the reactor from the chernobyl disaster was a rbmk reactor. rbmk eccs systems only have one division and have less than sufficient redundancy within that division. though the large core size of the rbmk makes it less energy - dense than the western lwr core, it makes it harder to cool. the rbmk is moderated by graphite. in the presence of both steam and oxygen, at high temperatures, graphite forms synthesis gas and with the water gas shift reaction the resultant hydrogen burns explosively. if oxygen contacts hot graphite, it will burn. the rbmk tends towards dangerous power fluctuations. control rods used to be tipped with graphite, a material that slows neutrons and thus speeds up the chain reaction. water is used as a coolant, but not a moderator. if the water boils away, cooling is lost, but moderation continues. this is termed a positive void coefficient of reactivity. control rods can become stuck if the reactor suddenly heats up and they are moving. xenon - 135


moderator. if the water boils away, cooling is lost, but moderation continues. this is termed a positive void coefficient of reactivity. control rods can become stuck if the reactor suddenly heats up and they are moving. xenon - 135, a neutron absorbent fission product, has a tendency to build up in the core and burn off unpredictably in the event of low power operation. this can lead to inaccurate neutronic and thermal power ratings. the rbmk does not have any containment above the core. the only substantial solid barrier above the fuel is the upper part of the core, called the upper biological shield, which is a piece of concrete interpenetrated with control rods and with access holes for refueling while online. other parts of the rbmk were shielded better than the core itself. rapid shutdown ( scram ) takes 10 to 15 seconds. western reactors take 1 - 2. 5 seconds. western aid has been given to provide certain real - time safety monitoring capacities to the human staff. whether this extends to automatic initiation of emergency cooling is not known. training has been provided in safety assessment from western sources, and russian reactors have evolved in result to the weaknesses that were in the rbmk. however, numerous rbmks still operate. it is safe to say that it might be possible to stop a loss - of - coolant event prior to core damage occurring, but that any core damage incidents will probably assure massive release of radioactive materials. further, dangerous power fluctuations are natural to the design. lithuania joined the eu recently, and upon acceding, it has been required to shut the two rbmks that it has at ignalina npp, as such reactors are totally incompatible with the nuclear safety standards of europe. it will be replacing them with some safer form of reactor. the mker is a modern russian - engineered channel type reactor that is a distant descendant of the rbmk. it approaches the concept from a different and superior direction, optimizing the benefits, and fixing the flaws of the original rbmk design. there are several unique features of the mker ' s design that make it a credible and interesting option : one unique benefit of the mker ' s design is that in the event of a challenge to cooling within the core - a pipe break of a channel, the channel can be isolated from the plenums supplying water, decreasing the potential for common - mode failures. the lower power density of the core greatly enhances thermal regulation. graphite moderation


within the core - a pipe break of a channel, the channel can be isolated from the plenums supplying water, decreasing the potential for common - mode failures. the lower power density of the core greatly enhances thermal regulation. graphite moderation enhances neutronic characteristics beyond light water ranges. the passive emergency cooling system provides a high level of protection by using natural phenomena to cool the core rather than depending on motor - driven pumps. the containment structure is modern and designed to withstand a very high level of punishment. refueling is accomplished while online, ensuring that outages are for maintenance only and are very few and far between. 97 - 99 % uptime is a definite possibility. lower enrichment fuels can be used, and high burnup can be achieved due to the moderator design. neutronics characteristics have been revamped to optimize for purely civilian fuel fertilization and recycling. due to the enhanced quality control of parts, advanced computer controls, comprehensive passive emergency core cooling system, and very strong containment structure, along with a negative void coefficient and a fast acting rapid shutdown system, the mker ' s safety can generally be regarded as being in the range of the western generation iii reactors, and the unique benefits of the design may enhance its competitiveness in countries considering full fuel - cycle options for nuclear development. the vver is a pressurized light water reactor that is far more stable and safe than the rbmk. this is because it uses light water as a moderator ( rather than graphite ), has well understood operating characteristics, and has a negative void coefficient of reactivity. in addition, some have been built with more than marginal containments, some have quality eccs systems, and some have been upgraded to international standards of control and instrumentation. present generations of vvers ( the vver - 1000 ) are built to western - equivalent levels of instrumentation, control, and containment systems. however, even with these positive developments, certain older vver models raise a high level of concern, especially the vver - 440 v230. the vver - 440 v230 has no containment building, but only has a structure capable of confining steam surrounding the rpv. this is a volume of thin steel, perhaps an inch or two in thickness, grossly insufficient by western standards. - has no eccs. can survive at most one 4 inch pipe break ( there are many pipes greater than 4 inches within the design ). - has six steam generator loops, adding unnecessary complexity. - however, apparently steam


insufficient by western standards. - has no eccs. can survive at most one 4 inch pipe break ( there are many pipes greater than 4 inches within the design ). - has six steam generator loops, adding unnecessary complexity. - however, apparently steam generator loops can be isolated, in the event that a break occurs in one of these loops. the plant can remain operating with one isolated loop - a feature found in few western reactors. the interior of the pressure vessel is plain alloy steel, exposed to water. this can lead to rust, if the reactor is exposed to water. one point of distinction in which the vver surpasses the west is the reactor water cleanup facility - built, no doubt, to deal with the enormous volume of rust within the primary coolant loop - the product of the slow corrosion of the rpv. this model is viewed as having inadequate process control systems. bulgaria had a number of vver - 440 v230 models, but they opted to shut them down upon joining the eu rather than backfit them, and are instead building new vver - 1000 models. many non - eu states maintain v230 models, including russia and the cis. many of these states - rather than abandoning the reactors entirely - have opted to install an eccs, develop standard procedures, and install proper instrumentation and control systems. though confinements cannot be transformed into containments, the risk of a limiting fault resulting in core damage can be greatly reduced. the vver - 440 v213 model was built to the first set of soviet nuclear safety standards. it possesses a modest containment building, and the eccs systems, though not completely to western standards, are reasonably comprehensive. many vver - 440 v213 models possessed by former soviet bloc countries have been upgraded to fully automated western - style instrumentation and control systems, improving safety to western levels for accident prevention - but not for accident containment, which is of a modest level compared to western plants. these reactors are regarded as " safe enough " by western standards to continue operation without major modifications, though most owners have performed major modifications to bring them up to generally equivalent levels of nuclear safety. during the 1970s, finland built two vver - 440 v213 models to western standards with a large - volume full containment and world - class instrumentation, control standards and an eccs with multiply redundant and diversified components. in addition, passive safety features such as 900 - tonne ice condensers have been installed, making these two units safety - wise the most advanced vver


- class instrumentation, control standards and an eccs with multiply redundant and diversified components. in addition, passive safety features such as 900 - tonne ice condensers have been installed, making these two units safety - wise the most advanced vver - 440 ' s in the world. the vver - 1000 type has a definitely adequate western - style containment, the eccs is sufficient by western standards, and instrumentation and control has been markedly improved to western 1970s - era levels. chernobyl disaster in the chernobyl disaster the fuel became non - critical when it melted and flowed away from the graphite moderator - however, it took considerable time to cool. the molten core of chernobyl ( that part that did not vaporize in the fire ) flowed in a channel created by the structure of its reactor building and froze in place before a core - concrete interaction could happen. in the basement of the reactor at chernobyl, a large " elephant ' s foot " of congealed core material was found. time delay, and prevention of direct emission to the atmosphere, would have reduced the radiological release. if the basement of the reactor building had been penetrated, the groundwater would be severely contaminated, and its flow could carry the contamination far afield. the chernobyl reactor was an rbmk type. the disaster was caused by a power excursion that led to a meltdown and extensive offsite consequences. operator error and a faulty shutdown system led to a sudden, massive spike in the neutron multiplication rate, a sudden decrease in the neutron period, and a consequent increase in neutron population ; thus, core heat flux very rapidly increased to unsafe levels. this caused the water coolant to flash to steam, causing a sudden overpressure within the reactor pressure vessel ( rpv ), leading to granulation of the upper portion of the core and the ejection of the upper plenum of said pressure vessel along with core debris from the reactor building in a widely dispersed pattern. the lower portion of the reactor remained somewhat intact ; the graphite neutron moderator was exposed to oxygen containing air ; heat from the power excursion in addition to residual heat flux from the remaining fuel rods left without coolant induced oxidation in the moderator ; this in turn evolved more heat and contributed to the melting of the fuel rods and the outgassing of the fission products contained therein. the liquefied remains of the fuel rods flowed through a drainage pipe into the basement of the reactor building and solidified in a mass later dubbed co


to the melting of the fuel rods and the outgassing of the fission products contained therein. the liquefied remains of the fuel rods flowed through a drainage pipe into the basement of the reactor building and solidified in a mass later dubbed corium, though the primary threat to the public safety was the dispersed core ejecta and the gasses evolved from the oxidation of the moderator. although the chernobyl accident had dire off - site effects, much of the radioactivity remained within the building. if the building were to fail and dust was to be released into the environment then the release of a given mass of fission products which have aged for twenty years would have a smaller effect than the release of the same mass of fission products ( in the same chemical and physical form ) which had only undergone a short cooling time ( such as one hour ) after the nuclear reaction has been terminated. however, if a nuclear reaction was to occur again within the chernobyl plant ( for instance if rainwater was to collect and act as a moderator ) then the new fission products would have a higher specific activity and thus pose a greater threat if they were released. to prevent a post - accident nuclear reaction, steps have been taken, such as adding neutron poisons to key parts of the basement. the effects of a nuclear meltdown depend on the safety features designed into a reactor. a modern reactor is designed both to make a meltdown unlikely, and to contain one should it occur. in a modern reactor, a nuclear meltdown, whether partial or total, should be contained inside the reactor ' s containment structure. thus ( assuming that no other major disasters occur ) while the meltdown will severely damage the reactor itself, possibly contaminating the whole structure with highly radioactive material, a meltdown alone should not lead to significant radiation release or danger to the public. in practice, however, a nuclear meltdown is often part of a larger chain of disasters ( although there have been so few meltdowns in the history of nuclear power that there is not a large pool of statistical information from which to draw a credible conclusion as to what " often " happens in such circumstances ). for example, in the chernobyl accident, by the time the core melted, there had already been a large steam explosion and graphite fire and major release of radioactive contamination ( as with almost all soviet reactors, there was no containment structure at chernobyl ). also, before a possible meltdown occurs, pressure can already be rising in the reactor, and to prevent


and graphite fire and major release of radioactive contamination ( as with almost all soviet reactors, there was no containment structure at chernobyl ). also, before a possible meltdown occurs, pressure can already be rising in the reactor, and to prevent a meltdown by restoring the cooling of the core, operators are allowed to reduce the pressure in the reactor by releasing ( radioactive ) steam into the environment. this enables them to inject additional cooling water into the reactor again. reactor design although pressurized water reactors are more susceptible to nuclear meltdown in the absence of active safety measures, this is not a universal feature of civilian nuclear reactors. much of the research in civilian nuclear reactors is for designs with passive nuclear safety features that may be less susceptible to meltdown, even if all emergency systems failed. for example, pebble bed reactors are designed so that complete loss of coolant for an indefinite period does not result in the reactor overheating. the general electric esbwr and westinghouse ap1000 have passively activated safety systems. the candu reactor has two low - temperature and low - pressure water systems surrounding the fuel ( i. e. moderator and shield tank ) that act as back - up heat sinks and preclude meltdowns and core - breaching scenarios. fast breeder reactors are more susceptible to meltdown than other reactor types, due to the larger quantity of fissile material and the higher neutron flux inside the reactor core, which makes it more difficult to control the reaction. accidental fires are widely acknowledged to be risk factors that can contribute to a nuclear meltdown. united states there have been at least eight meltdowns in the history of the united states. all are widely called " partial meltdowns. " - borax - i was a test reactor designed to explore criticality excursions and observe if a reactor would self limit. in the final test, it was deliberately destroyed and revealed that the reactor reached much higher temperatures than were predicted at the time. - the reactor at ebr - i suffered a partial meltdown during a coolant flow test on november 29, 1955. - the sodium reactor experiment in santa susana field laboratory was an experimental nuclear reactor which operated from 1957 to 1964 and was the first commercial power plant in the world to experience a core meltdown in july 1959. - stationary low - power reactor number one ( sl - 1 ) was a united states army experimental nuclear power reactor which underwent a criticality excursion, a steam explosion, and a meltdown on january 3,


experience a core meltdown in july 1959. - stationary low - power reactor number one ( sl - 1 ) was a united states army experimental nuclear power reactor which underwent a criticality excursion, a steam explosion, and a meltdown on january 3, 1961, killing three operators. - the snap8er reactor at the santa susana field laboratory experienced damage to 80 % of its fuel in an accident in 1964. - the partial meltdown at the fermi 1 experimental fast breeder reactor, in 1966, required the reactor to be repaired, though it never achieved full operation afterward. - the snap8dr reactor at the santa susana field laboratory experienced damage to approximately a third of its fuel in an accident in 1969. - the three mile island accident, in 1979, referred to in the press as a " partial core melt, " led to the permanent shutdown of that reactor. soviet union in the most serious example, the chernobyl disaster, design flaws and operator negligence led to a power excursion that subsequently caused a meltdown. according to a report released by the chernobyl forum ( consisting of numerous united nations agencies, including the international atomic energy agency and the world health organization ; the world bank ; and the governments of ukraine, belarus, and russia ) the disaster killed twenty - eight people due to acute radiation syndrome, could possibly result in up to four thousand fatal cancers at an unknown time in the future and required the permanent evacuation of an exclusion zone around the reactor. during the fukushima i nuclear accidents, three of the power plant ' s six reactors reportedly suffered meltdowns. most of the fuel in the reactor no. 1 nuclear power plant melted. tepco believes no. 2 and no. 3 reactors were similarly affected. on may 24, 2011, tepco reported that all three reactors melted down. meltdown incidents - there was also a fatal core meltdown at sl - 1, an experimental u. s. military reactor in idaho. large - scale nuclear meltdowns at civilian nuclear power plants include : - the lucens reactor, switzerland, in 1969. - the three mile island accident in pennsylvania, u. s. a., in 1979. - the chernobyl disaster at chernobyl nuclear power plant, ukraine, ussr, in 1986. - the fukushima i nuclear accidents following the earthquake and tsunami in japan, march 2011. other core meltdowns have occurred at : - nrx ( military ), ontario, canada, in 1952 - borax - i ( experimental ),


- the fukushima i nuclear accidents following the earthquake and tsunami in japan, march 2011. other core meltdowns have occurred at : - nrx ( military ), ontario, canada, in 1952 - borax - i ( experimental ), idaho, u. s. a., in 1954 - ebr - i ( military ), idaho, u. s. a., in 1955 - windscale ( military ), sellafield, england, in 1957 ( see windscale fire ) - sodium reactor experiment, ( civilian ), california, u. s. a., in 1959 - fermi 1 ( civilian ), michigan, u. s. a., in 1966 - chapelcross nuclear power station ( civilian ), scotland, in 1967 - saint - laurent nuclear power plant ( civilian ), france, in 1969 - a1 plant, ( civilian ) at jaslovske bohunice, czechoslovakia, in 1977 - saint - laurent nuclear power plant ( civilian ), france, in 1980 china syndrome the china syndrome ( loss - of - coolant accident ) is a fictional nuclear reactor operations accident characterized by the severe meltdown of the core components of the reactor, which then burn through the containment vessel and the housing building, then notionally through the crust and body of the earth until reaching the other side, which in the united states is jokingly referred to as being china. the system design of the nuclear power plants built in the late 1960s raised questions of operational safety, and raised the concern that a severe reactor accident could release large quantities of radioactive materials into the atmosphere and environment. by 1970, there were doubts about the ability of the emergency cooling systems of a nuclear reactor to prevent a loss of coolant accident and the consequent meltdown of the fuel core ; the subject proved popular in the technical and the popular presses. in 1971, in the article thoughts on nuclear plumbing, former manhattan project ( 1942 – 1946 ) nuclear physicist ralph lapp used the term " china syndrome " to describe a possible burn - through, after a loss of coolant accident, of the nuclear fuel rods and core components melting the containment structures, and the subsequent escape of radioactive material ( s ) into the atmosphere and environment ; the hypothesis derived from a 1967 report by a group of nuclear physicists, headed by w. k. ergen. in the event, lapp ’ s hypothetical nuclear accident was cinematically adapted as the china syndrome ( 1979 ). the geographic, planet - piercing concept of the china syndrome derives from


of nuclear physicists, headed by w. k. ergen. in the event, lapp ’ s hypothetical nuclear accident was cinematically adapted as the china syndrome ( 1979 ). the geographic, planet - piercing concept of the china syndrome derives from the misperception that china is the antipode of the united states ; to many americans, it is the “ the other side of the world ”. moreover, the hypothetical transit of a meltdown product to the other side of the earth ( i. e. china ) ignores the fact that the earth ' s gravity tends to pull all masses towards its center. assuming a meltdown product could persist in a mobile molten form for long enough to reach the center of the earth ; momentum loss due to friction ( fluid viscosity ) would prevent it continuing to the other side. see also - behavior of nuclear fuel during a reactor accident - chernobyl compared to other radioactivity releases - chernobyl disaster effects - high - level radioactive waste management - international nuclear event scale - list of civilian nuclear accidents - lists of nuclear disasters and radioactive incidents - nuclear fuel response to reactor accidents - nuclear safety - nuclear power - nuclear power debate - martin fackler ( june 1, 2011 ). " report finds japan underestimated tsunami danger ". new york times. - international atomic energy agency ( iaea ) ( 2007 ). iaea safety glossary : terminology used in nuclear safety and radiation protection ( 2007edition ed. ). vienna, austria : international atomic energy agency. isbn 92 - 0 - 100707 - 8. retrieved 2009 - 08 - 17. - united states nuclear regulatory commission ( nrc ) ( 2009 - 09 - 14 ). " glossary ". website. rockville, maryland, usa : federal government of the united states. pp. see entries for letter m and entries for letter n. retrieved 2009 - 10 - 03. - reactor safety study : an assessment of accident risks in u. s. commercial nuclear power plants, volume 1 - hewitt, geoffrey frederick ; collier, john gordon ( 2000 ). " 4. 6. 1 design basis accident for the agr : depressurization fault ". introduction to nuclear power ( in technical english ). london, uk : taylor & francis. p. 133. isbn 978 - 1 - 56032 - 454 - 6. retrieved 2010 - 06 - 05. - " earthquake report no. 91 ". jaif. may 25, 2011. retrieved may 25, 2011. - kuan,


. 133. isbn 978 - 1 - 56032 - 454 - 6. retrieved 2010 - 06 - 05. - " earthquake report no. 91 ". jaif. may 25, 2011. retrieved may 25, 2011. - kuan, p. ; hanson, d. j., odar, f. ( 1991 ). managing water addition to a degraded core. retrieved 2010 - 11 - 22. - haskin, f. e. ; camp, a. l. ( 1994 ). perspectives on reactor safety ( nureg / cr - 6042 ) ( reactor safety course r - 800 ), 1st edition. beltsville, md : u. s. nuclear regulatory commission. p. 3. 1 – 5. retrieved 2010 - 11 - 23. - haskin, f. e. ; camp, a. l. ( 1994 ). perspectives on reactor safety ( nureg / cr - 6042 ) ( reactor safety course r - 800 ), 1st edition. beltsville, md : u. s. nuclear regulatory commission. pp. 3. 5 – 1 to 3. 5 – 4. retrieved 2010 - 12 - 24. - haskin, f. e. ; camp, a. l. ( 1994 ). perspectives on reactor safety ( nureg / cr - 6042 ) ( reactor safety course r - 800 ), 1st edition. beltsville, md : u. s. nuclear regulatory commission. pp. 3. 5 – 4 to 3. 5 – 5. retrieved 2010 - 12 - 24. - ans : public information : resources : special topics : history at three mile island : what happened and what didn ' t in the tmi - 2 accident - nuclear industry in russia sells safety, taught by chernobyl - ' melt - through ' at fukushima? / govt. suggests situation worse than meltdown http : / / www. yomiuri. co. jp / dy / national / t110607005367. htm - test area north - walker, j. samuel ( 2004 ). three mile island : a nuclear crisis in historical perspective ( berkeley : university of california press ), p. 11. - lapp, ralph e. " thoughts on nuclear plumbing. " the new york times, 12 december 1971, pg. e11. - " china syndrome ". merriam - webster. retrieved december 11, 2012. - presenter : martha raddatz ( 15 march 2011 ). " abc world news ". abc. - allen


, 12 december 1971, pg. e11. - " china syndrome ". merriam - webster. retrieved december 11, 2012. - presenter : martha raddatz ( 15 march 2011 ). " abc world news ". abc. - allen, p. j. ; j. q. howieson, h. s. shapiro, j. t. rogers, p. mostert and r. w. van otterloo ( april – june 1990 ). " summary of candu 6 probabilistic safety assessment study results ". nuclear safety 31 ( 2 ) : 202 – 214. - http : / / www. insc. anl. gov / neisb / neisb4 / neisb _ 1. 1. html inl vver sourcebook - partial fuel meltdown events - anl - w reactor history : borax i - wald, matthew l. ( 2011 - 03 - 11 ). " japan expands evacuation around nuclear plant ". the new york times. - the chernobyl forum : 2003 - 2005 ( 2006 - 04 ). " chernobyl ’ s legacy : health, environmental and socio - economic impacts ". international atomic energy agency. p. 14. retrieved 2011 - 01 - 26. - the chernobyl forum : 2003 - 2005 ( 2006 - 04 ). " chernobyl ’ s legacy : health, environmental and socio - economic impacts ". international atomic energy agency. p. 16. retrieved 2011 - 01 - 26. - hiroko tabuchi ( may 24, 2011 ). " company believes 3 reactors melted down in japan ". the new york times. retrieved 2011 - 05 - 25.


roman siege engines | this article is part of the series on : military of ancient rome ( portal ) 753 bc – ad erals | roman navy ( fleets, admirals ) | | lists of wars and battles | | decorations and punishments | | military engineering ( castra, siege engines, arches, roads ) | | strategy and tactics | | frontiers and fortifications ( limes, hadrian ' s wall ) | roman siege engines were, for the most part, adapted from hellenistic siege technology. relatively small efforts were made to develop the technology ; however, the romans brought an unrelentingly aggressive style to siege warfare that brought them repeated success. up to the 1st century bc the romans utilized siege weapons only as required and relied for the most part on ladders, towers and rams to assault a fortified town. ballistae were also employed, but held no permanent place within a legion ' s roster, until later in the republic, and were used sparingly. julius caesar took great interest in the integration of advanced siege engines, organizing their use for optimal battlefield efficiency. army engineering corps to facilitate this organization and the army ’ s self - sufficiency, an engineering corps was developed. an officer of engineers, or praefectus fabrum, is referenced in armies of the late republic, but this post is not verifiable in all accounts and may have simply been a military advisor on the personal staff of a commanding officer. there were legion architects ( whose rank is yet unknown ) who were responsible for the construction of war machines who would also assure that all artillery constructions in the field were level. ensuring that constructions were level was the job of the libratores, who would also launch missiles and other projectiles ( on occasion ) during battle ( le bohec 1994 : 52 ). the engineering corps was in charge of massive production, frequently prefabricating artillery and siege equipment to facilitate its transportation. roman artillery was very efficient at that time, and during a siege the romans would attack the weakest area of their enemy ’ s defenses and attempt to breach the walls at that point. to support this effort, artillery fire would commence, with three main objectives : to cause damage to defenses, casualties among the opposing army, and loss of enemy morale. it would also provide cover fire for troops building siege ramps or those in siege towers. there were machines called tormenta, which would launch ( sometimes incendiary ) projectiles such as javelins, arrows, rocks, or beams. these devices were on


would also provide cover fire for troops building siege ramps or those in siege towers. there were machines called tormenta, which would launch ( sometimes incendiary ) projectiles such as javelins, arrows, rocks, or beams. these devices were on wheeled platforms to follow the line ’ s advance. all were “ predicated on a principle of physics : a lever was inserted into a skein of twisted horsehair to increase torsion, and when the arm was released, a considerable amount of energy was thus freed ”. it was later stated that sinew, instead of twisted hair, provided a better “ spring. ” these weapons were high - maintenance devices and vulnerable to having their leather, sinew, or hemp skeins affected by wet or even damp, which would cause them to slacken and lose tension, rendering the engine useless. it is somewhat difficult to clearly define and describe roman artillery, as names are easily confused and historians still do not agree on all definitions. perhaps best known are the ballista, the onager, and the scorpio. after the absorption of the ancient greek city states into the roman republic in 146 bc, some advanced greek technology began to spread across many areas of roman influence. this included the hugely advantageous military advances the greeks had made ( most notably by dionysus of syracuse ), as well as all the scientific, mathematical, political and artistic developments. the romans ' inherited ' the torsion powered ballistae which had by now spread to several cities around the mediterranean, all of which became roman spoils of war in time, including one from pergamum, which was depicted among a pile of ' trophy ' weapons in relief on a balustrade. the torsion ballista, developed by alexander, was a far more complicated weapon than its predecessor, and the romans developed it even further. every century ( group of 60 - 100 men ) in the roman army had a ballista by the 1st century ad. it was the command of the chief of the ballista, under whom were the artillery experts, or doctores ballistarum and finally, the artillerymen, or ballistarii. ballistae were heavy missile weapons, hurling large rocks great distances to damage rampart walls. they resembled large crossbows, rather than catapults. they were powered by two horizontal like arms, which were inserted into two vertical and tightly wound " skein " springs contained in a rectangular frame structure making up the head or principal part of the weapon. the arms were drawn


than catapults. they were powered by two horizontal like arms, which were inserted into two vertical and tightly wound " skein " springs contained in a rectangular frame structure making up the head or principal part of the weapon. the arms were drawn rearward with a winch lever to further twist the skeins and thus gain the torsion power to cast a projectile. it has been said that the whirring sound of a ballista - fired stone struck fear and dread into the hearts of those inside the walls of besieged cities. the stones chosen to be used in the ballista had to be a particular sort. according to vegetius river stones were best, since they are round, smooth, and dense. ballista stones found at the site of masada were chiseled to make them as round as possible. early roman ballista the early roman ballistae were made of wood, and held together with iron plates around the frames and iron nails in the stand. the main stand had a slider on the top, into which were loaded the bolts or stone ' shot '. attached to this, at the back, was a pair of winches and a claw, used to ratchet the bowstring back to the armed firing position. a slider passed through the field frames of the weapon, in which were located the torsion springs ( rope made of animal sinew ), which were twisted around the bow arms, which in turn were attached to the bowstring. drawing the bowstring back with the winches twisted the already taut springs, storing the energy to fire the projectiles. the ballista was a highly accurate weapon ( there are many accounts right from its early history of single soldiers being picked off by the operators ), but some design aspects meant it could compromise its accuracy for range. the lightweight bolts could not gain the high momentum of the stones over the same distance as those thrown by the later onagers, trebuchets, or mangonels ; these could be as heavy as 90 - 135 kg ( 200 - 300 pounds ). the romans continued the development of the ballista, and it became a highly - prized and valued weapon in the army of the roman empire. it was used, just before the start of the empire, by julius caesar during his conquest of gaul and on both of his expeditions to britain. both attempted invasions of britain and the siege of alesia are recorded in his own commentarii ( journal ), the gallic wars ( de bello gallico


by julius caesar during his conquest of gaul and on both of his expeditions to britain. both attempted invasions of britain and the siege of alesia are recorded in his own commentarii ( journal ), the gallic wars ( de bello gallico ). it was also used in the roman siege of masada. first invasion of britain the first invasion of britain took place in 55 bc, after a rapid and successful initial conquest of gaul, in part as an exploratory expedition, and more practically to try and put an end to the re - enforcements sent by the native britons to fight the romans in gaul. a total of eighty transports, carrying two legions attempted to land on the british shore, only to be driven back by the many british warriors assembled along the shoreline. the ships had to unload their troops on the beach, as it was the only one suitable for many kilometers, yet the massed ranks of british charioteers and javeliners were making it impossible. seeing this, caesar ordered the warships – which were swifter and easier to handle than the transports, and likely to impress the natives more by their unfamiliar appearance – to be removed a short distance from the others, and then be rowed hard and run ashore on the enemy ’ s right flank, from which position the slings, bows and artillery could be used by men on deck to drive them back. this manoeuvre was highly successful. scared by the strange shape of the warships, the motion of the oars, and the unfamiliar machines, the natives halted and then retreated a little. ( caesar, the conquest of gaul, p. 99 ) siege of alesia in gaul, the stronghold of alesia was under a roman siege in 52 bc, and surrounded by roman fortifications. as was standard siege technique at the time, ballistae were placed up in the towers with other soldiers armed with either bows or slings. the onager the onager was a post - classical roman siege engine, which derived its name from the kicking action of the machine, similar to that of an onager ( wild ass ). it is a type of catapult that uses torsional pressure, generally from twisted rope, to store energy for the shot. the onager consisted of a frame placed on the ground to whose front end a vertical frame of solid timber was rigidly fixed ; through the vertical frame ran an axle, which had a single stout spoke. on the extremity of the spoke was a sling used to launch a projectile. in


the ground to whose front end a vertical frame of solid timber was rigidly fixed ; through the vertical frame ran an axle, which had a single stout spoke. on the extremity of the spoke was a sling used to launch a projectile. in action the spoke was forced down, against the tension of twisted ropes or other springs, by a windlass, and then suddenly released. the spoke thus kicked the crosspiece of the vertical frame, and the projectile at its extreme end was shot forward. the onagers of the roman empire were mainly used for besieging forts or settlements. they would often be loaded with large stones or rocks that could be covered with a flammable substance and set alight. in the middle ages ( recorded from around 1200 c. e. ) a less powerful version of the onager was used that employed a fixed bowl rather than a sling, so that many small projectiles could be thrown, as opposed to a single large one. this engine was sometimes called the mangonel, although the same name may have been used for a variety of siege engines. the scorpio was a crossbow - like device that fired smaller arrows with deadly accuracy used both in the field and in sieges. they were so - named for their deadly, armor - piercing sting and could be operated by just one or two men. scorpions were meant to kill and injure enemy troops, rather than break down enemy fortifications. thanks to their smaller size, they could be mounted on or in siege towers. during the siege of amida, a scorpion - fired arrow killed the son of grumbate, king of the chionitae, when he was approaching the city to surrender. there has been some research done into the existence of the self - loading, serial - fire scorpio or polybolos. legionaries either side would continuously keep turning cranks which turned a chain, which operated the various mechanisms to load and fire the catapult. all that was needed was for another soldier to keep feeding in more arrows. breaking the walls battering rams roman battering rams, or aries, were an effective weapon for breaking down an enemy ’ s walls, as well as their morale. under roman law, any defenders who failed to surrender before the first ram touched their wall were denied any rights. the moment they heard the ram hit the wall, those inside the city knew that the siege proper had begun and there was no turning back. it is an immense beam, similar to a ship ’ s mast, with


their wall were denied any rights. the moment they heard the ram hit the wall, those inside the city knew that the siege proper had begun and there was no turning back. it is an immense beam, similar to a ship ’ s mast, with one end covered with iron shaped into a ram ’ s head ; hence its name. it is suspended from another beam like a balance arm by cables around its middle, and this in turn is supported at both ends by posts fixed in the ground. it is drawn back by a huge number of men who then push it forward in unison with all their might so that it hits the wall with its iron head. there is no tower strong enough nor any wall thick enough to withstand repeated blows of this kind, and many cannot resist the first shock. for protection, a battering ram was suspended in a mobile shelter called a tortoise, or testudo. according to vegetius, it was given this name because the ram would swing out of the shelter much like a tortoise ’ s head comes out of its shell. such shelters would provide the men within protection against missiles and incendiary devices. they were constructed from a framework of strong timbers with planks and wicker hurdles on the sides. the entire shelter would then be covered with a fireproof material such as uncured hides. according to apollodorus of damascus, the shelter should be fixed to the ground while the ram was being used to both prevent skidding and strain on the axles from the weight of the moving apparatus. this would also increase the strength of the impact on the walls. siege towers according to josephus, the roman siege towers at jotapata were 50 feet high and iron - plated to protect them from fire ; those at masada were reported to be 75 feet high. it was possible to have many different devices on siege towers, such as artillery, draw bridges and rams. those at the top of the tower were to keep defenders off the walls while those below them attempted to breach the wall using ramps. following a basic design, details of tower construction varied from siege to siege and there is no known treatise which specifies at which level siege equipment should be placed. vegetius noted that, “ besiegers sometimes built a tower with another turret inside it that could suddenly be raised by ropes and pulleys to over - top the wall ”. mines could be dug under city walls as a means of entering a city secretly and capturing it but were more frequently constructed to weaken city walls.


turret inside it that could suddenly be raised by ropes and pulleys to over - top the wall ”. mines could be dug under city walls as a means of entering a city secretly and capturing it but were more frequently constructed to weaken city walls. once dug, sappers would underpin the walls with wood and cause the walls to collapse by firing the supports with resin, sulfur and other incendiary materials. - goldsworthy 2000 : 144 - keppie 1984 : 99 - le bohec 1994 : 138 - catapulta at legionxxiv - le bohec 1994 : p. 138 - le bohec 1994 : p. 49 - garrison 1997. - goldsworthy 2000 : 191 - siege weapons at roman - empire. net - goldsworthy 2000 : p. 145 - gilliver 1999 : p. 140 - le bohec 1994 : p. 139 - gilliver 1999 : pp. 134 - 135 - gilliver 1999 : p. 138 - gilliver 1999 : pp. 136 - 137. - gilliver 1999 : 138 - gilliver 1999 : 140 - james v. garrison ( 1997 ). " casting stones : ballista, stones as weapons, and death by stoning ". brigham young university studies 36 ( 3 ) : 351 – 352. - gilliver, c. m. ( 1999 ). the roman art of war. charleston, sc : tempus. isbn 0 - 7524 - 1939 - 0. - goldsworthy, adrian ( 2000 ). roman warfare. london : cassell. isbn 0 - 304 - 35265 - 9. - keppie, lawrence ( 1984 ). the making of the roman army from empire to republic. totowa, nj : barnes & noble books. isbn 0 - 389 - 20447 - 1. - le bohec, yann ( 1994 ). the imperial roman army. london : b. t. batsford ltd. isbn 0 - 7134 - 7166 - 2. see also


signal - to - noise ratio ( often abbreviated snr or s / n ) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. it is defined as the ratio of signal power to the noise power. a ratio higher than 1 : 1 indicates more signal than noise. while snr is commonly quoted for electrical signals, it can be applied to any form of signal ( such as isotope levels in an ice core or biochemical signaling between cells ). signal - to - noise ratio is sometimes used informally to refer to the ratio of useful information to false or irrelevant data in a conversation or exchange. for example, in online discussion forums and other online communities, off - topic posts and spam are regarded as " noise " that interferes with the " signal " of appropriate discussion. where p is average power. both signal and noise power must be measured at the same or equivalent points in a system, and within the same system bandwidth. if the signal and the noise are measured across the same impedance, then the snr can be obtained by calculating the square of the amplitude ratio : where a is root mean square ( rms ) amplitude ( for example, rms voltage ). because many signals have a very wide dynamic range, snrs are often expressed using the logarithmic decibel scale. in decibels, the snr is defined as which may equivalently be written using amplitude ratios as the concepts of signal - to - noise ratio and dynamic range are closely related. dynamic range measures the ratio between the strongest un - distorted signal on a channel and the minimum discernable signal, which for most purposes is the noise level. snr measures the ratio between an arbitrary signal level ( not necessarily the most powerful signal possible ) and noise. measuring signal - to - noise ratios requires the selection of a representative or reference signal. in audio engineering, the reference signal is usually a sine wave at a standardized nominal or alignment level, such as 1 khz at + 4 dbu ( 1. 228 vrms ). snr is usually taken to indicate an average signal - to - noise ratio, as it is possible that ( near ) instantaneous signal - to - noise ratios will be considerably different. the concept can be understood as normalizing the noise level to 1 ( 0 db ) and measuring how far the signal ' stands out '. difference from conventional power in physics power ( physics ) of an ac signal is defined as but in signal processing and communication we usually assume that


as normalizing the noise level to 1 ( 0 db ) and measuring how far the signal ' stands out '. difference from conventional power in physics power ( physics ) of an ac signal is defined as but in signal processing and communication we usually assume that so that usually we don ' t include that resistance term while measuring power or energy of a signal. this usually causes some confusions among readers but the resistance term is not significant for operations performed in signal processing. most of cases the power of a signal would be where ' a ' is the amplitude of the ac signal. in some places people just use as the constant term doesn ' t affect much during the calculations. alternative definition where is the signal mean or expected value and is the standard deviation of the noise, or an estimate thereof. [ note 2 ] notice that such an alternative definition is only useful for variables that are always non - negative ( such as photon counts and luminance ). thus it is commonly used in image processing, where the snr of an image is usually calculated as the ratio of the mean pixel value to the standard deviation of the pixel values over a given neighborhood. sometimes snr is defined as the square of the alternative definition above. the rose criterion ( named after albert rose ) states that an snr of at least 5 is needed to be able to distinguish image features at 100 % certainty. an snr less than 5 means less than 100 % certainty in identifying image details. snr for various modulation systems amplitude modulation channel signal - to - noise ratio is given by where w is the bandwidth and ka is modulation index output signal - to - noise ratio ( of am receiver ) is given by frequency modulation channel signal - to - noise ratio is given by output signal - to - noise ratio is given by improving snr in practice all real measurements are disturbed by noise. this includes electronic noise, but can also include external events that affect the measured phenomenon — wind, vibrations, gravitational attraction of the moon, variations of temperature, variations of humidity, etc., depending on what is measured and of the sensitivity of the device. it is often possible to reduce the noise by controlling the environment. otherwise, when the characteristics of the noise are known and are different from the signals, it is possible to filter it or to process the signal. for example, it is sometimes possible to use a lock - in amplifier to modulate and confine the signal within a very narrow bandwidth and then filter the detected signal to the narrow band where it resides, thereby eliminating most of the broadband noise.


. for example, it is sometimes possible to use a lock - in amplifier to modulate and confine the signal within a very narrow bandwidth and then filter the detected signal to the narrow band where it resides, thereby eliminating most of the broadband noise. when the signal is constant or periodic and the noise is random, it is possible to enhance the snr by averaging the measurement. in this case the noise goes down as the square root of the number of averaged samples. digital signals when a measurement is digitised, the number of bits used to represent the measurement determines the maximum possible signal - to - noise ratio. this is because the minimum possible noise level is the error caused by the quantization of the signal, sometimes called quantization noise. this noise level is non - linear and signal - dependent ; different calculations exist for different signal models. quantization noise is modeled as an analog error signal summed with the signal before quantization ( " additive noise " ). this theoretical maximum snr assumes a perfect input signal. if the input signal is already noisy ( as is usually the case ), the signal ' s noise may be larger than the quantization noise. real analog - to - digital converters also have other sources of noise that further decrease the snr compared to the theoretical maximum from the idealized quantization noise, including the intentional addition of dither. although noise levels in a digital system can be expressed using snr, it is more common to use eb / no, the energy per bit per noise power spectral density. the modulation error ratio ( mer ) is a measure of the snr in a digitally modulated signal. fixed point assuming a uniform distribution of input signal values, the quantization noise is a uniformly distributed random signal with a peak - to - peak amplitude of one quantization level, making the amplitude ratio 2n / 1. the formula is then : this relationship is the origin of statements like " 16 - bit audio has a dynamic range of 96 db ". each extra quantization bit increases the dynamic range by roughly 6 db. assuming a full - scale sine wave signal ( that is, the quantizer is designed such that it has the same minimum and maximum values as the input signal ), the quantization noise approximates a sawtooth wave with peak - to - peak amplitude of one quantization level and uniform distribution. in this case, the snr is approximately floating point note that the dynamic range is much larger than fixed - point,


then can be calculated from data where the signal is zero or relatively constant. - often special filters are used to weight the noise : din - a, din - b, din - c, din - d, ccir - 601 ; for video, special filters such as comb filters may be used. - maximum possible full scale signal can be charged as peak - to - peak or as rms. audio uses rms, video p - p, which gave + 9 db more snr for video. - michael a. choma, marinko v. sarunic, changhuei yang, joseph a. izatt. sensitivity advantage of swept source and fourier domain optical coherence tomography. optics express, 11 ( 18 ). sept 2003. - d. j. schroeder ( 1999 ). astronomical optics ( 2nd ed. ). academic press. p. 433. isbn 978 - 0 - 12 - 629810 - 9. - bushberg, j. t., et al., the essential physics of medical imaging, ( 2e ). philadelphia : lippincott williams & wilkins, 2006, p. 280. - rafael c. gonzalez, richard eugene woods ( 2008 ). digital image processing. prentice hall. p. 354. isbn 0 - 13 - 168728 - x. - tania stathaki ( 2008 ). image fusion : algorithms and applications. academic press. p. 471. isbn 0 - 12 - 372529 - 1. - jitendra r. raol ( 2009 ). multi - sensor data fusion : theory and practice. crc press. isbn 1 - 4398 - 0003 - 0. - john c. russ ( 2007 ). the image processing handbook. crc press. isbn 0 - 8493 - 7254 - 2. - defining and testing dynamic parameters in high - speed adcs — maxim integrated products application note 728 - fixed - point vs. floating - point dsp for superior audio — rane corporation technical library - taking the mystery out of the infamous formula, " snr = 6. 02n + 1. 76db, " and why you should care. analog devices - adc and dac glossary – maxim integrated products - understand sinad, enob, snr, thd, thd + n, and sfdr so you don ' t get lost in the noise floor – analog devices - the relationship of dynamic range to data word size in digital audio processing - calculation


july 24, 2011 the photo above shows a lovely group of mushrooms nestled against the trunk of a eucalyptus tree. the association between the fungi and the tree however is no accident. this is a mutualistic relationship, where the two species assist each other, and in fact probably would be poorer without each other. mutualism is any relationship between two species of organisms that benefits both species. up to a quarter of the mushrooms you see while walking through the woods actually make their living through a mutualistic relationship with the trees in the forest. remember of course that the mushroom is just the reproductive structure of a far more extensive organism consisting of a highly intertwined mass of fine white threads called a mycelium. the word mycorrhiza is derived from the classical greek words for " mushroom " and " root. " in a mycorrhizal association, the fungal hyphae of an underground mycelium are in contact with plant roots but without the fungus parasitizing the plant. while it ' s clear that the majority of plants form mycorrhizas, the exact percentage is uncertain, but it ' s likely to lie somewhere between 80 and 90 percent. when the fungus ’ mycelium envelopes the roots of the tree the effect is to greatly increase the soil area covered by the tree ’ s root system. this essentially extends the plant ’ s reach to water and nutrients, allowing it to utilize more of the soil ’ s resources. this mutualistic association provides the fungus with a relatively constant and direct access to carbohydrates, such as glucose and sucrose, supplied by the plant. in return the plant gains the benefits of the mycelium ' s higher absorptive capacity for water and mineral nutrients ( due to comparatively large surface area of mycelium - to - root ratio ), thus improving the plant ' s mineral absorption capabilities. photo taken on may 7, 2011. photo details : camera maker : canon ; camera model : canon eos 50d ; focal length : 70. 0mm ; aperture : f / 10. 0 ; exposure time : 0. 013 s ( 1 / 80 ) ; iso equiv : 1250 ; exposure bias : - 1. 00 ev ; metering mode : matrix ; exposure : aperture priority ( semi - auto ) ; white balance : auto ; flash fired : no ( enforced ) ; orientation : normal ; color space : srgb.


part 2 : prefurbia incorporates flow - by rick harrison - oct 01, 2010 for the past four decades, the automotive industry has invested billions in fuel efficiency and reducing drag and, at the same time, significantly added to the average engine horsepower. while government has focused on the vehicle, no steps have been taken to make neighborhood streets more efficient. the management of a new era of design dedicated to reducing time and energy while transiting through a neighborhood is called " flow. " in prefurbia, flow is essential to neighborhood sustainability. getting a vehicle in motion ( phase 1 ), cruising ( phase 2 ) and stopping or slowing ( phase 3 ) are the three phases of a “ segment cycle. ” a segment begins upon entry to a street and ends when a driver stops or slows down to turn or enter another street. phase 1 involves the time and energy needed to get a one - to two - ton ( or more ) vehicle moving from a stop to a target residential speed. in some areas, this could be from 20 miles per hour to 30 mph. phase 1 consumes the most energy and typically the most time. phase 2 uses the least time and less energy than phase 1. phase 3 consumes almost as much time as phase 1, but with new braking technology, this phase can actually generate energy. reducing the number of phase 1 segments lowers the amount of energy consumed. similarly, reducing the number of phase 1 and 3 segments also shortens the time needed to travel. at 30 mph, the distance needed to accelerate and then stop comfortably is about 400 feet. in traditional planning processes, designers give little ( if any ) attention to the flow of traffic. very few homes are located on an entry street, requiring 90 percent of the residents to travel a minimum of two segment cycles. about half the residents have to use three segment cycles to reach their homes. in prefurbia, most residents can get home with just one segment cycle, and only a few others have two segment cycles. the length of phase 2 is critical. in the conventional subdivision, for the most part, the distance along each segment cycle is quite short with some so small that phase 2 is never reached. this design may be so inconvenient from a flow standpoint that the driver is " encouraged " to accelerate to make up for the time. segment cycles within the prefurbia neighborhood are long, enabling a driver more time in phase 2. note the cul - de - sac on the right in figure 3. why didn ' t the designer


to accelerate to make up for the time. segment cycles within the prefurbia neighborhood are long, enabling a driver more time in phase 2. note the cul - de - sac on the right in figure 3. why didn ' t the designer reverse the street to loop the cul - de - sac the other way, reducing the segment length from the entry to the end of the cul - de - sac? prefurbia is a balance of economics, environment, and existence so the designer must weigh each benefit and derive a design that serves each of the three “ es ” well. in this case, the geometry of the area better achieves efficiency with the current configuration. also, having an intersection serving 30 homes as soon as a driver enters the neighborhood is not the best for safety. on the other side of the site, there is such an intersection but it serves fewer lots. finally, the cul - de - sac provides a nice entrance void of street intersections. the homes pulled away from the street give the impression of low density. if a street was placed at this point, entering the neighborhood would not have this welcome feel. in prefurbia, designers use [ www. performanceplanningsystem. com / trafficdiffuers ] traffic diffusers, which maintain flow on the primary traffic street while providing the functionality of a roundabout. from a pollution standpoint – addressing the auto industry without addressing planning is like requiring frosting to have no calories yet use the frosting on a high fat, sugar laden cake reducing environmental impacts prefurbia reduces waste and employs more efficient forms of design. the method represents a reversal of how technology in land development is used, replacing lots per minute ( lpm ) automation with the art of neighborhood design. it ’ s time for technology to be used to construct great neighborhoods for families to thrive. by exceeding the minimums, designers can deliver economic and environmental advantages. there are only a few situations in which a tight grid pattern designed to minimums is the optimum solution from a geometric perspective. such a site must closely conform to the dimensions needed to stack lots, with a fairly flat topography and long blocks that have few cross streets. here are a few examples that demonstrate better efficiency gains through design. figure 1 shows two cul - de - sac ’ s side by side. both use the following minimums : - 25 - foot front yard setback, - 5 - foot side yard setback, - 80 - foot lot width at the setback, and - 60


reduce environmental impacts. when the island is used to filter stormwater, there would be no mountable curbs to pay for, reducing costs even more. a wide walk extends through the neighborhood. the driveways become longer, but they are tapered and use the prefurbia method of sculpting with organic lanes, so they consume similar surface area to a standard driveway, even though they are longer. density is a function of how many lots a designer can fit along the front setback line. in order to stretch the front setback length to gain density ( when the minimum setback guarantees the front of the home is exactly parallel to the curb ), the designer also must stretch the street. to gain density, the designer consumes the site with street, which is a poor choice for the environment and economics. the cul - de - sac example increases the setback depth, which is still somewhat concentric to the traffic circle. with prefurbia, designers can totally separate the relationship between front setback and street where road paving, walks, and homes all form their own organized sculpted shapes. coving is the first organized planning method that separates the rigid parallel relationship between the front of the home and curb of the street. efficiency varies, but a 25 percent gain in efficiency compared to conventional design is about the average. imagine a world with 25 percent less construction costs and environmental impacts. an organic free - form design will almost always conform to the natural surface area much easier than a rigid pattern. with the gain in efficiency, monotony is a thing of the past, each lot takes on a unique shape making it virtually impossible to utilize a lpm technology.


peel - and - stick solar cells available in near future the nrel and stanford are teaming up to develop peel - and - stick solar cells, which could become devices to charge battery operated products, such as cell phones, in the future. peel - and - stick, or water - assisted transfer printing ( wtp ), technologies were developed by the stanford group and have been used before for nanowire based electronics, but the stanford - nrel ( u. s. department of energy ’ s national renewable energy laboratory ) partnership has conducted the first successful demonstration using actual thin film solar cells. the university and nrel showed that thin - film solar cells less than one - micron thick can be removed from a silicon substrate used for fabrication by dipping them in water at room temperature. then, after exposure to heat of about 90°c for a few seconds, they can attach to almost any surface. nrel ’ s cells could be made easily on stanford ’ s peel off substrate. nrel ’ s amorphous silicon cells were fabricated on nickel - coated si / sio2 wafers. a thermal release tape attached to the top of the solar cell serves as a temporary transfer holder. an optional transparent protection layer is spin - casted in between the thermal tape and the solar cell to prevent contamination when the device is dipped in water. the result is a thin strip much like a bumper sticker : the user can peel off the handler and apply the solar cell directly to a surface. the cells ’ ability to adhere to a universal substrate is unusual ; most thin - film cells must be affixed to a special substrate. the peel - and - stick approach allows the use of flexible polymer substrates and high processing temperatures. the resulting flexible, lightweight, and transparent devices then can be integrated onto curved surfaces such as military helmets and portable electronics, transistors and sensors.


united arab emirates morris, mervyn j. ( 2009 ) united arab emirates. in dana, leo - paul, han, mary, ratten, vanessa, & welpe, isabell ( eds. ) handbook of research on asian entrepreneurship. edward elgar publishing, cheltenham, pp. 361 - 367. | sample ( pdf 1788kb ) | administrators only | request a copy from author the united arab emirates ( uae ) is part of the geographic region known as the middle east. with a land mass of 82, 000 square kilometres, predominantly desert and mountains it is bordered by oman, saudi arabia and the arabian gulf. the uae is strategically located due to its proximity to other oil rich middle eastern countries such as kuwait, iraq, iran, and saudi arabia. the uae was formed from a federation of seven emirates ( abu dhabi, dubai, sharjah, ras al khaimah, ajman, fujuriah, and um al quain ) in december 1971 ( ras al khaimah did not join the federation until 1972 ) ( heard - bey, 2004, 370 ). abu dhabi is the political capital, and the richest emirate ; while dubai is the commercial centre. the majority of the population of the various emirates live along the coast line as sources of fresh water often heavily influenced the site of different settlements. unlike some near neighbours ( iran and iraq ) the uae has not undergone any significant political instability since it was formed in 1971. due to this early british influences the uae has had very strong political and economic ties with first britain, and, more recently, the united states of america ( rugh, 2007 ). until the economic production of oil in the early 1960 ’ s the different emirates had survived on a mixture of primary industry ( dates ), farming ( goats and camels ), pearling and subsidies from britain ( davidson 2005, 3 ; hvit, 2007, 565 ) along with near neighbours kuwait, bahrain, oman, qatar and saudi arabia, the uae is part of the gulf cooperation council ( gcc ), a trading bloc. ( hellyer, 2001, 166 - 168 ). citation countsare sourced monthly fromand citation databases. these databases contain citations from different subsets of available publications and different time periods and thus the citation count from each is usually different. some works are not in either database and no count is displayed. scopus includes citations from articles published in 1996 onwards, and web of science generally from 1980 onwards. citations counts from theindexing service can


, on a low plateau draining into the basins of the bristol channel, the english channel, and the eastward - flowing thames. oh, and home. it is surrounded by the counties of gloucestershire trowbridge is the administrative centre of wiltshire for reasons that seem to escape pretty much all of the local inabitants. trowbridge is, after all, a nasty little hole full of 1970s council buildings and a sausage factory. surely salisbury or even swindon would have been a much better choice? the administrative, geographic, and historic counties occupy slightly different areas. the administrative county of wiltshire comprises four districts — salisbury ( in the south ), west wiltshire, kennet in the east, named for the river kennet and north wiltshire. the geographic county encompasses the entire administrative county together with the unitary authority of swindon. the historic county of wiltshire is nearly the same as the geographic county but also includes a small area north of sherston in the cotswolds, and thus administratively controlled by gloucestershire, but we ' ll get it back, damn their eyes. much of wiltshire is made up of chalk hills. salisbury plain occupies central wiltshire but not many people go near there since most of it is crown land and reserved for the armed forces to play soldiers on. north of the river kennet are the marlborough downs, which make up one side of the vale of the white horse. along the county ' s western border rise parts of the cotswolds, a range of limestone hills. between these two upland areas lie the clay valleys of wardour and pewsey. south of trowbridge the valleys are fairly heavily forested in contrast to the open, rolling countryside of the uplands. savernake forest was the last known refuge of the english black bear for a very long time. parts of the marlborough downs, the cotswolds, and the vale of pewsey have been designated areas of outstanding natural beauty. of course, in real terms all that this actually means is that building a bloody great housing estate there is more expensive than elsewhere, requiring one to own many more politicians and local councillors than one would need to in, for example, melksham. in prehistoric times the chalk uplands were the most heavily populated parts of england, and wiltshire has many prehistoric monuments. stonehenge, about 8 miles north of salisbury, dates from the neolithic period and its use by prehistoric peoples has been a topic of much debate. the predominant local theory is that either it ' s a huge bong that no - one ' s found the mouthpiece


about 8 miles north of salisbury, dates from the neolithic period and its use by prehistoric peoples has been a topic of much debate. the predominant local theory is that either it ' s a huge bong that no - one ' s found the mouthpiece from yet or that it was constructed on perfectly good arable land by neolithic wiltshiremen in a ( very successful ) effort to irritate their decendants. there are plenty of other important neolithic monuments nearby, including those at avebury and windmill hill. the latter is believed by those credulous fools from universities to have been a centre of ritual and of seasonal tribal fasting in the 4th millennium bc but these are the kind of people who say crop circles were made by aliens, so what can you expect? the former is a big stone circle with a pub in the middle and is therefore of at least some value. long neolithic burial mounds, or barrows, are all over the place as are round burial mounds from the bronze age. the ancient practise of building large mounds of earth over dead people is suspected locally to be a means of making certain that the buggers don ' t get out. durrington walls, a large ditch - enclosed ceremonial earthwork, dates from the late 3rd millennium bc, apparently. these days it hosts the occassional rave. plus ca change, plus c ' est la meme chose. during the iron age, hill forts were constructed, such as those at yarnbury castle, near berwick st. james, and at old sarum, outside salisbury. the county has played a role in national affairs in as much as any county can be said to have done so. there are roman remains all over the place, and in the middle ages, sheep farming by cistercian monks was probably the most important activity. oliver cromwell won a decisive battle against the royalists just outside devizes and king alfred the great soundly kicked the danes ' collective arse just outside of chippenham. salisbury has long been the ecclesiastical centre of the county and is renowned for its 13th - century cathedral which apparently still has the tallest church spire in britain. salisbury is unusual in that the building of elegant crescents in the georgian period never really caught on there, so the city is still faithfully tudor in design. in the northwest of the county there a couple of places that visitors call " quaint " and think are authentic. well, there ' s one born every minute, after all. the first is lacock, an entire village owned by the


design. in the northwest of the county there a couple of places that visitors call " quaint " and think are authentic. well, there ' s one born every minute, after all. the first is lacock, an entire village owned by the national trust. lacock is steadfastly 16th century apart from the volvos and is regularly annexed by the bbc so they can do yet another interminable jane austen costume drama. it has three really good pubs, an abbey that was unabbeyfied during the reformation and later served as home to the father of modern photography, william henry fox talbot and tourists are available for shooting all year round. another is castle combe, a wool - village with a working mill and a manor house that stems from the same period but is even more picturesque. i know people who think heaven will look castle combe. it is noticeable for, among other things, the largest number of antique shops per capita of anywhere in the world. the last that i shall mention is the village my family are from. it ' s a hamlet called sandy lane where all the houses are quaintly thatched and there ' s even a thatched, wooden church dating from the norman conquest - the only one of its kind remaining in the uk. finally, the one thing that may surprise you, is that wiltshire is big. it comprises of just over 1, 255 square miles. not exactly texan but for the south of england, that ' s pretty huge. in this size, there ' s room for a lot of cool stuff. ignore my sarcasm, wiltshire is well worth a visit.


should wellheads be above or below the ground surface? posted : june 2, 2010 many private well owners in pennsylvania have wellheads that are buried below the surface of the ground. this may be appealing to homeowners that don ’ t like looking at a pipe sticking up in the middle of their yard, but research studies have demonstrated a clear benefit to having an extended wellhead. what problems can a buried well cause? wells that are buried below the ground can have numerous disadvantages to wells that are extended above the ground surface. the most obvious disadvantage is that the well is not easily accessible by the well driller in the event that it needs to be serviced. often the homeowner is unaware of the wells exact location underground, which can lead to added expense if the driller needs to do some investigating. wells buried below the ground surface are also more susceptible to bacterial contamination. research studies conducted at penn state university have found that wells buried in pits are more likely to have the presence of coliform bacteria than wells that are extended above the earth ’ s surface. what can you do to fix your buried well? fortunately, it is not usually difficult to extend a wellhead above the ground. a qualified water well driller should be able to weld or thread extra casing to your existing well and raise it above the ground. if the well was buried in a pit, it should be filled in with bentonite grout to the land surface. a sanitary or vermin - proof well cap should also be installed on the newly extended casing to ensure that surface contamination can not enter the well. as an added protection, the ground should be sloped away from your wellhead in all directions to prevent any surface water from ponding around the well. after having the well extended, it would be a wise to take a sample of your drinking water to a state certified water testing lab for analysis. if the water tests positive for coliform bacteria then steps should be taken to disinfect the well. information on coliform bacteria can be found at the link below. how high should the well casing be extended above the ground? any distance is better than having it buried below ground, but it is ideal to extend the well casing at least 12 inches above the ground surface.


there was a great piece in the new york times last week on vegetable consumption in the u. s. the article was prompted by a recent cdc study, which found that only 26 % of americans eat three or more servings of vegetables per day ; disappointing news but hardly a surprise. most of those interviewed in the article take a pessimistic tone when responding to the study ’ s findings. here are a couple illustrative quotes : “ eating vegetables is a lot less fun than eating flavor - blasted doritos, ” said marcia mogelonsly, a senior analyst for mintel, a global marketing firm. “ you will always have to fight that. ” “ there is nothing you can say that will get people to eat more veggies, ” said harry balzer, the chief industry analyst for the npd group, a market research company. … “ before we want health, we want taste, we want convenience and we want low cost. ” despite the article ’ s generally dour tone, it did provide strong academic support for a key component of a better food system – edible gardens that are integrated into school curriculum : researchers at the university of california, berkeley, spent three years examining the difference between children who participated in the berkeley unified school district ’ s “ edible schoolyard ” program, in which gardening and cooking are woven into the school day, and children who didn ’ t. the students who gardened ate one and half servings more of fruits and vegetables a day than those who weren ’ t in the program. what better way to make vegetables exciting than to establish a personal connection with the growing process. plus, i ’ m going to wager that the fresh tomatoes from those edible schoolyards taste a whole lot better than the canned alternatives. produce photo from flickr user mckaysavage, accessed 10 / 4 / 10. creative commons.


you are currently browsing the tag archive for the ‘ chalchiuhtotolin ’ tag. in our ongoing exploration of underworld gods, we have come across all sorts of animal divinities. the ultra - modern japanese still venerate namazu a vast chthonic catfish god. contemporary inuits worship sedna, walrus / cetacean goddess of the cold depths. the rational greeks imagined a great three - headed dog guarding tartarus. there are so many giant serpents from different cultures that they create an entire subset of underworld gods : some of these snake beings are bigger than the world and longer than the oceans. they range from kind creators like nuwa to monsters like the midgard serpent to indescribable cosmic forces like the rainbow serpent. there are dark swans and mystery animals, but where in this worldwide pantheon / bestiary are my favorite birds? where are the turkey gods? well, turkeys are from the americas, they were sacred to the original inhabitants ( and have been discovered buried alongside humans with ceremonial pomp – or even by themselves on altars ). however the americas were swept by a great wave of diseases which was followed by waves of european colonizers. when the native americans were killed by plague or assimilated by europeans, many of their deities vanished. the spaniards were delighted to find domesticated turkeys in the ruins of the aztec empire and they shipped them off to spain as farm animals ( whereas it seems they may have been originally domesticated for their feathers ). however even now we know a little bit about important aztec turkey deities. chalchiuhtotolin, “ precious night turkey ” was a god of plague who ruled thirteen days of the aztec calendar from 1 water to 13 crocodile ( the thirteen preceding days were in fact ruled by xolotl, hapless god of misfortune, who was instrumental in the creation of humankind ). little is known concerning chalchiuhtotolin, except that he was magnificent and terrible to behold. as a plague god he holds a somewhat ironic place in aztec cosmology ( since the aztecs were defeated and destroyed more directly by smallpox then by cortes ). it is theorized that chalchiuhtotolin was an animal aspect of tezcatlipoca, one of the central gods of aztec mythology ( who was more famous in his ferocious manifestation as a jaguar ). tezcatlipoca was one of the four cardinal gods of direction, ruling the north ( which was a realm of


just recently it was reported that biologists from the university of nevada at reno have been routinely observing unusually large goldfish in the pristine waters of lake tahoe in northern california. this phenomenon has caught the attention of the california state fish and game department who have instituted routine patrols to seek out what they consider to be a dangerous invasive species. the scientists speculate that the giant goldfish were introduced in the lake tahoe by so - called “ aquarium dumpers, ” well - meaning people who when they were no longer able to care for their pet fish, decided to abandon them in lake tahoe where they believed they would live out their lives in a safe and pleasant environment in the company of many other species of fish and crustaceans. some experts questioned whether a goldfish could survive the frigid winters that characterize this deep, high - mountain lake. however, reality proved to be stranger than fiction when the goldfish not only survived, but thrived in the harsh alpine climate. thanks to the nutrient - rich effluent making its way into lake tahoe, the goldfish not only thrived but were also genetically transformed as a consequence of the metabolites of psychotropic pharmaceuticals that were present in the sewage emanating from affluent neighborhoods along the lakeshore. they adapted splendidly and in no time at all they quickly blended into the local culture and adopted the habits and customs of the local residents. now the goldfish are regularly seen enjoying the recreational facilities throughout the area, although they curiously prefer to avoid being seen at restaurants and tackle shops. this is not by any means the first time giant goldfish have been seen in freshwater lakes. this trophy giant goldfish was caught by raphael biagini, a legendary french “ carpiste, ” who reeled in the monster “ poisson rouge ” from the waters of lac de st. cassien, a man - made reservoir in southern france. this is the same lake where a 75 - pound world record carp was caught some 25 years ago. it is not clear how a tiny fish that normally graces home aquariums grew to such gargantuan size. some locals familiar with the story attribute the fish ’ s extraordinary size with an incident that occurred a few years back when a barge laden with camembert cheese capsized during a squall and sank with its cargo into the depths of lake st. cassien. the nutrient - rich cheese provided a source of food for several stray goldfish that, like nemo, had been flushed down the toilet and


fills the space between two objects, generally to prevent leakage between the two objects while under compression. gasket material saves money by allowing less precise mating surfaces on machine parts which can use gasket fill irregularities. gaskets are commonly produced by cutting from sheet gasket materials, such as gasket paper ( beater addition ), non - asbestos, rubber, epdm, nitrile, buna, neoprene, flexible graphite, grafoil, aflas, kalrez, viton, silicone, metal, mica, felt or a plastic polymer such as ptfe, peek, urethane, or ethylene propylene ( ep ). in the past, the gasket material selected for specific applications may contain have contained today ' s sealing products manufacturer ' s in the united states no longer produce or offer any asbestos containing products. gasket materials containing asbestos have been claimed to have caused asbestosis. of course it would take the grinding of gasket material to release the fibers and then the breathing in of those fibers.... possible but in the real world this would be rare. wetting or oiling a gasket before grinding for removal greatly reduces any risk ( not grinding is even better ). asbestos gasket material is still used in most of the rest of the world and is a very effective low cost material. it is usually desirable that the gasket be made from a material that is compressible such that it tightly fills the space it is designed for, including any slight irregularities. the most common misconception when selecting a gasket materials thickness is to choose a gasket material that is too thick. the thicker the material the more likely the material being contained can weep through the pores of the gasket material itself. this is a greater issue with some materials than others. a rule of thumb is to have the material thick enough to compensate for any surface face irregularities and to permit some compression. the required compression for your gasket material will depend many 2 ) pressure being sealed 3 ) size of bolts ( assuming bolts are being used ) 4 ) number of bolts 5 ) condition of the bolts 6 ) lubrication on the bolts all must be considered when determining torque. torque data must be determined using all of the above and should be provided by an engineer. in most cases unless your gasket is a standard ansi or api flange using ring or full face gaskets torque data will


when determining torque. torque data must be determined using all of the above and should be provided by an engineer. in most cases unless your gasket is a standard ansi or api flange using ring or full face gaskets torque data will be difficult to come by ( due to staffing and the fear of law suits ). in most cases the old tighten it tight enough to stop any leaks but not too tight as to completely crush the gasket is generally accepted. over compression removes the ability to recover. this is also true of expanded ptfe ( teflon ® ), once over compressed it will have no recovery and therefore will not longer adapt to maintain a seal. the common strategy of " the more compressive load exerted on the gasket, the longer it will last " is generally true of elastomeric materials since elastomers ( rubbers ) are not compressible but deflect compression. many materials such as non - asbestos compressed gasket materials and beater addition ( ie ; armstrong ) materials contain elastomers in the mix of material they are produced from, making them difficult to over compress. one of the more desirable properties of an effective gasket industrial applications is the ability to withstand high compressive loads. most industrial gasket applications involve bolts exerting compression well into the 14 mpa ( 2000 psi ) range or higher. this is why non - asbestos gasket materials are so widely used in industrial gasket material applications. call american seal & packing for your gasket material requirements. teflon® is a registered trademark of e. i. du pont de nemours and company or its affiliates and is used in relation to products manufactured with dupont ’ s fluoropolymer resins.


what is an advance directive? none of us, but especially seniors, is immune to serious illness or injury. when these conditions are so severe that death is imminent, it is important that doctors, family, and friends know your wishes in those situations. one way to share your wishes is through an advance directive. advance directives are a legally binding document that expresses your wishes in the event of serious illness or injury. these documents can be quite detailed or quite general. one detail is what you want done in each specific medical possibility. for example : - what do you want done if you stop breathing? - what do you want done if you develop inoperable cancer? what about tumors? - do you want breathing machines or feeding tubes used? these documents empower someone to make decisions about your medical care if you are unable to make these decisions yourself. it makes sense to speak with the people you appoint. let them know your wishes. only appoint people who are willing to accept the responsibility of making medical decisions for you when are no longer able to make them for yourself. also be sure and discuss your wishes with those close to you such as your family or friends. such documents must follow the laws in your state in order to be legally binding. it is best to have one or two people witness and sign the document. in order for these documents to be effective, your doctor and hospital must have copies. do i need one? it is important for senior citizens to prepare these documents. however, any of us at any age may encounter a life threatening illness or injury. if you have strong feelings about what you want done in these situations, you need to have these wishes written down in a legally binding document. what is a living will? a living will is a type of advance directive. it is a document outlining explicit instructions regarding medical treatment and life - sustaining procedures if you are permanently unconscious or terminally ill. usually, a doctor ( or even two ) will have to certify that you are in either of these states before the living will comes into effect. since modern medicine now has the ability to prolong life indefinitely, it is necessary to prepare a living will when you are still healthy in body and mind. what is a durable power of attorney for health care? a durable power of attorney for health care names someone to manage your health care and make all medical treatment decisions for you when you are not able to. this person is usually called a “ healthcare proxy ” or a healthcare agent. ” your chosen representative can make decisions such as


attorney for health care names someone to manage your health care and make all medical treatment decisions for you when you are not able to. this person is usually called a “ healthcare proxy ” or a healthcare agent. ” your chosen representative can make decisions such as consenting or refusing treatment, choosing doctors, selecting medical care facilities, and accessing medical records. this durable power of attorney usually does not give explicit instructions to the healthcare agent. this is another reason why it ’ s important to have an advance directive that provides this person with your wishes. what is a do not resuscitate order? do not resuscitate orders or dnrs tell doctors and hospitals what you want done should your breathing or heart stop functioning. examples of treatment that you can decline include cpr, artificial respiration, medicine to keep your heart functioning, artificial nutrition, or specific surgeries. if you fill out a dnr, your doctor should put the order in your medical records. without a dnr order, hospitals will typically do what they can to resuscitate someone whose heart has stopped. dnr orders are especially important for seniors with a heart condition. resources for preparing an advance directive sometimes your medical facility will have these forms on hand for you to express your wishes. you will sign the document and have it witnessed right there in the hospital, long term care facility, or doctor ’ s office. the doctors and nurses caring for you want to make sure that your decisions are honored. another option is to contact your state bar association or state government office for the proper forms. you can also hire an attorney who is knowledgeable in health care directives. working with an attorney helps ensure that your directive meets the state legal requirements. it does no good to prepare a health care directive if it is not legally recognized. another option for obtaining a health care directive is purchasing software that allows you to fill in your information and print the document. by searching online you can find online services that will guide you through preparing the directive. it may be unpleasant to think of serious illness and death. detailing your wishes in advance will relieve some stress from you and your family in these situations. what ’ s a caregiver? a caregiver or home health aide is an individual that gives personal care to patients in a large variety of settings, although their role may vary greatly from one setting to another. caregiving often takes place in the patient ’ s home, but may also be available in nursing homes, assisted living facilities and even hospitals. often the patient is elderly


large variety of settings, although their role may vary greatly from one setting to another. caregiving often takes place in the patient ’ s home, but may also be available in nursing homes, assisted living facilities and even hospitals. often the patient is elderly, but sometimes an illness necessitates the need for a paid companion in the home to assist an adult or care for a child. what does a caregiver do in the home? essentially, the main purpose of a home care helper is the responsibility they shoulder for assisting their patients with their physical and cognitive health. the variety of duties performed by the caregiver depends on the needs of the patient. some of the more common duties in the home environment include : - grooming assistance for brushing teeth, bathing, shaving, nail care and toileting as required. - monitoring medications and reminding patients to take medications. - assisting the patient with exercise, which may include simply providing help with walking around the house or moving in place. - helping the patient maintain their memory. - deciding the number of meals that are required to meet the patient ’ s nutritional needs. - preparing meals, then, cleaning up the items related to the meals. - performing necessary grocery shopping or errands with or without the patient. - check foods in the patient ’ s pantry for expiration dates. - providing conversation and companionship. - light housekeeping duties, such as dusting and vacuuming, making beds, doing laundry, and maintaining sanitation. - accompanying the patient to doctor appointments as necessary. - notifying doctors of any significant change in the patient ’ s condition. more serious home situations may be supervised by a senior helper rn, who should complete a customized plan of care and supervise the home health aide. approximately 90 percent of dependent patients use the services of a home health care service or a family member to keep the patient at home, rather than in a nursing home. patients who have mild to moderate cognitive impairment still want to be involved in decisions concerning their care and their life. a physician will often set the boundaries to ensure the responsibility for medical decisions do not fall on the shoulders of the home companion. when is caregiving needed? there are some simple ways to assess when a loved one might need to have in - home care. does the person : - have trouble with their normal movement around the house such as getting from the bedroom to bathroom? - need medical assistance such as cleaning wounds or administering insulin? - need help with normal daily activities such as bathing and getting dressed? obviously,


the person : - have trouble with their normal movement around the house such as getting from the bedroom to bathroom? - need medical assistance such as cleaning wounds or administering insulin? - need help with normal daily activities such as bathing and getting dressed? obviously, a person affected by dementia or alzheimer ’ s disease needs help in the home. changes in eating habits, personal hygiene, social habits and any safety issues that might occur in the home all need to be evaluated. hiring a personal companion for your loved one can also help relieve the stress on family members, and it assures the family members that their loved one is receiving proper care. this help can be critical if the family member doesn ’ t live near the loved one. is caregiving available outside the home? most seniors would like to have caregiving take place in their own home. there are situations, however, when the person who is ill will receive more appropriate care in an institution. caregivers working in an assisted living facility or nursing home, like home caregivers, assist patients with their activities of daily living. the health aide can also play an important role in helping patients experience meaningful leisure activities, which helps keep the patient ’ s mind active. demonstrating compassion for those suffering from alzheimer ’ s disease or dementia is essential. often the companion works with pets, particularly dogs, cats or birds, as these pets can provide a great deal of pleasure for the patient. sometimes caregiver working hours in these facilities can be irregular and include weekends or holidays. caregiving can be difficult work, whether the patient is a senior citizen, a parent, a spouse or a child with special needs. family members are often caregivers, which can be quite stressful as they are on - call 24 hours a day, seven days a week. in these cases good caregiver resources may involve support groups, which can be quite helpful. caregiver resources should include information on the role of medicare for patients. specific classes that can provide useful training are often available to empower the companion or home care helper. resources are available at the following sites : http : / / caregiver. org / caregiver / jsp / home. jsp family caregiver alliance home page http : / / www. caregiving. com / a community of family caregivers sharing stories, support and solutions http : / / www. caregiverresource. net / caregiver resources. http : / / www. caregiverslibrary. org / home


a java runtime environment ( jre ), version greater than 1. 6, is required to run jython and geoscript. chances are your system already has a jre installed on it. a quick way to test is to execute the following from the command line : % java - version java version " 1. 6. 0 _ 26 " java ( tm ) se runtime environment ( build 1. 6. 0 _ 26 - b03 - 384 - 10m3425 ) java hotspot ( tm ) 64 - bit server vm ( build 20. 1 - b02 - 384, mixed mode ) if the command is not found or the java version is less than 1. 6 you must install a new jre. otherwise you can continue to the next step. a jre can be downloaded from sun microsystems. it is possible to run geoscript with a different non sun jre. however the sun jre is recommended as it has been thoroughly tested. jython version greater than 2. 5. 1 is required for geoscript. the current version can be downloaded from http : / / www. jython. org /. after install ensure that the jython bin directory is on the path : where < jython _ dir > is the root jython installation directory. run ez _ setup. py with jython : some newer features are only avaialble in the latest 1. 3 build, which is still considered experimental. unpack the geoscript archive : change directory into the root of the unpacked archive and execute setup. py : cd geoscript - 1. 2 jython setup. py install depending on your setup the install may require root privileges. that ’ s it. geoscript should now be installed on the system. to verify the install execute the geoscript command : % geoscript jython 2. 5. 1 ( release _ 2 _ 5 _ 1 : 6813, sep 26 2009, 13 : 47 : 54 ) [ java hotspot ( tm ) client vm ( apple inc. ) ] on java1. 5. 0 _ 20 type " help ", " copyright ", " credits " or " license " for more information. > > > import geoscript > > > if you do not get an import error congratulations! geoscript is installed on the system.