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91.
Papa Cisse 《International Journal of Green Energy》2013,10(1):91-100
Many fuel installations and industrial operations often are associated with the release, whether deliberately or inadvertently, of fuel vapors into the surrounding atmosphere. Most of these releases may be considered to be relatively small on a thermal basis, but they do represent collectively a serious source of unburned hydrocarbon emissions into the atmosphere. Moreover, the emissions of methane from various sources of natural gas contribute significantly to green house gas emissions. The paper presents computed results of the transient dissipation of a fixed mass of methane when released within vertical cylindrical vessels containing air, which are open to the outside atmosphere under ambient conditions. Particular attention is given to the rates of emission of gas into the outside atmosphere and how it is affected by the composition and mass of the fuel released and the size and configuration of the fuel retaining cylindrical tank. The corresponding transient formation, growth and subsidence of flammable zones within such a vessel are also described. Some guidelines for reducing the hazards associated with such releases are presented. 相似文献
92.
Brant A. Peppley 《International Journal of Green Energy》2013,10(2):201-218
Fuel cells can be highly efficient energy conversion devices. However, the environmental benefit of utilising fuel cells for energy conversion is completely dependent on the source of the fuel. Hydrogen is the ideal fuel for fuel cells but the current most economical methods of producing hydrogen also result in the production of significant amounts of carbon dioxide. Utilising biomass to produce the fuel for fuel cell systems offers an option that is technically feasible, potentially economically attractive and greenhouse gas neutral. High-temperature fuel cells that are able to operate with carbon monoxide in the feed are well suited to these applications. Furthermore, because they do not require noble metal catalysts, the cost of high-temperature fuel cells has the greatest potential to become competitive in the near future compared to other types of fuel cells. It is, however, extremely difficult to assess the economic feasibility of biomass-fuelled fuel cell systems because of a lack of published cost information and uncertainty in the predicted cost per kW of the various types of fuel cells for large volume production methods. From the scant information available it appears that the current cost for fuel-cell systems operating on anaerobic digester gas is about US$2,500 per kW compared to a target price of US$1,200 required to compete with conventional technologies. 相似文献
93.
Several recent papers have documented an effect of fuel prices on new vehicle fuel economy in the United States. This paper estimates the effect of fuel prices on average new vehicle fuel economy for the eight largest European markets. The analysis spans the years 2002–2007 and uses detailed vehicle registration and specification data to control for policies, consumer preferences, and other potentially confounding factors. We find fuel prices to have a statistically significant effect on average new vehicle fuel economy in Europe. The effect estimated for Europe is much smaller than comparable estimates for the United States. 相似文献
94.
Fuel consumption and collection costs of solid waste were evaluated by the aid of a simulation model for a given collection area of a medium-sized Italian city. Using the model it is possible to calculate time, collected waste and fuel consumption for a given waste collection route. Starting from the data for the current waste collection scenario with a Source Segregated (SS) intensity of 25%, all the main model error evaluated was ?1.2. SS intensity scenarios of 25%, 30%, 35% and 52% were simulated. Results showed an increase in the average fuel consumed by the collection vehicles that went from about 3.3 L/tonne for 25% SS intensity to about 3.8 L/tonne for a SS intensity of 52%. Direct collection costs, including crews and vehicle purchase, ranged from about 40 €/tonne to about 70 €/tonne, respectively, for 25% and 52% SS intensity. The increase in fuel consumption and collection costs depends on the density of the waste collected, on the collection vehicle compaction ratio and on the waste collection vehicle utilization factor (WCVUF). In particular a reduction of about 50% of the WCVUF can lead to an average increase of about 80% in fuel consumption and 100% in collection costs. 相似文献
95.
The large number of radio frequency (RF) transmitters employed in modern marine platforms requires that they operate in mutual
coexistence while posing no danger to operators and equipment despite the limited available physical space. A key to the successful
system integration is the control of the electromagnetic environment on the ships’ topsides, which might pose radiation hazards
(RADHAZ) to personnel (HERP). HERP are caused by transmitter antenna installations that generate intentional EM radiation
in excess of the safe levels in zones of personnel activity. Radiation safety to personnel is achieved when the average radiation
power density is below the permissible exposure limits (PEL) for HERP at locations of personnel activity and medical equipment
operation. This paper describes the analysis tools and techniques for the evaluation of HERP on marine platforms. The same
approaches could be employed in the analysis of land site antenna deployment scenarios. 相似文献
96.
Should I stay or should I go? Testing optimality models of stopover decisions in migrating birds 总被引:1,自引:0,他引:1
Thomas P. Weber Thord Fransson Alasdair I. Houston 《Behavioral ecology and sociobiology》1999,46(4):280-286
Time-minimizing migrants should leave a stopover site if the instantaneous speed of migration drops to the average speed
of migration in the environment. This argument has been used in two different ways: either there is local variation in the
fuel deposition rate and a fixed expected speed or there is global variation in the fuel deposition rate, i.e. locally experienced
variation represents global variation along the route. The first case leads to a far steeper relationship between departure
load and fuel deposition rate than the second case. So far, data on departure loads have mainly been analysed within the concept
of local variation of the fuel deposition rate and the result that the observed slopes are much lower than predicted has been
explained by changes in the expected speed along the route or by individual differences in the expected speed. We show here
that the observed relationships generally fall close to the predictions for global variation. We propose that migrants use
a behavioural rule which projects the current experience into the future and therefore interprets local variation as global
variation.
Received: 3 April 1999 / Received in revised form: 22 April 1999 / Accepted: 26 April 1999 相似文献
97.
Posttreatment Tree Mortality After Forest Ecological Restoration,Arizona, United States 总被引:1,自引:0,他引:1
Pine–oak forests are of high ecological importance worldwide, but many are threatened by uncharacteristically severe wildfire.
Forest restoration treatments, including the reintroduction of a surface fire regime, are intended to decrease fire hazard
and emulate historic ecosystem structure and function. Restoration has recently received much management attention and short-term
study, but little is known about longer-term ecosystem responses. We remeasured a replicated experimental restoration site
in the southwestern United States 5 years after treatments. Basal area, tree density, and canopy cover decreased in the treated
units at a faster rate than in controls. Delayed mortality, not evident right after treatment, decreased density modestly
(13% in treated units and 10% in controls) but disproportionately affected large trees (“large” ponderosa pines were those
with diameter at breast height [dbh] ≥37.5 cm; other species dbh ≥20 cm). In treated units, 10.9 large trees ha–1 died, whereas 6.2 trees ha–1 died in control units. Compared with reference conditions, the experimental blocks remained higher in pine density and, in
three of the four blocks, in basal area. Pine trees grew significantly faster in treated units than in controls, enough to
reach the reference level of basal area in 6 years. Although mortality of large trees is a concern, the treated units have
vigorous growth and low density, indicating that they will be relatively resistant to future drought and fire events. Similar
treatments may be beneficial in many areas of the United States and in related pine-oak ecosystems elsewhere. 相似文献
98.
FAE威力评价方法与目标防护分析 总被引:5,自引:0,他引:5
对燃料空气炸药(FAE)爆炸场特性进行了分析;从冲击波超压- 冲量毁伤准则出发,提出一种以靶板毁伤效应为评价依据的FAE威力评价方法,并结合易损性等效原理,对不同毁伤等级下目标防护问题进行了分析 相似文献
99.
100.
油母页岩干馏煤气脱硫工艺的选择 总被引:1,自引:0,他引:1
何红梅 《辽宁城乡环境科技》2006,26(2):33-34,42
针对页岩炼油厂生产工艺和二氧化硫的产生量,提出了煤气干法和湿法脱硫工艺,并对这两种工艺在原理和适用性方面进行了对比,认为湿法脱硫更适合于该厂的实际情况,经对湿法脱硫的投资费用进行的估算结果显示,该厂采用湿法脱硫技术将会带来明显的环境效益和社会效益。 相似文献