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851.
依据避暑旅居的内涵与特点,从环境质量、服务需求、旅游资源和市场潜力4个维度构建了我国避暑旅居指标体系,并运用多维度综合评价法对我国25个主要城市的避暑旅居潜力进行了研究。结果发现:不同城市的避暑旅居潜力差异较大,生态环境质量、旅游资源丰富性、地区经济水平、交通区位条件、服务接待能力和游客感知水平等是避暑旅居潜力大小的主要影响因素。通过对分类评价潜力模型的分析,提出各自的发展方向与建议。 相似文献
852.
摘要近30年来,商层建筑发展十分迅速,高层建筑火灾也随之开始频繁发生,在扑救火灾过程中,消防队员常常伤亡,就高层建筑灭火过程中的潜在危险进行分析并提出相应的预防措施。 相似文献
853.
采用微生物电合成系统(MES)还原CO2合成有机物,从微生物菌群、有机物积累量、库伦效率、电化学分析等多个角度研究了阴极电势对MES还原CO2合成有机物性能的影响。实验结果表明:阴极电势为-0.70 V时,甲酸和乙酸的积累量均最大(分别为1.554 mmol/L和2.754 mmol/L),系统的总库伦效率最大(为81.42%);在MES中,醋杆菌(Acetobacterium sp.)、假丝酵母菌(Candida sp. S)、地杆菌(Geobacter sp.)为优势菌种。 相似文献
854.
Using six different doses of peptone (0.25, 0.50, 0.75, 1.0, 1.25 and 1.50 gl-1) and nine different periods of inclubation (1, 2, 3, 4, 6, 8, 10, 12 and 14 days), the rates of ammonification potential (AP) were monitored in three tropical ponds of differetn ecological status, during winter and summer periods. During the winter, the AP (ammonifying bacteria) exhibited peaks on day 4 of incubation in all the test doses of peptone in all the three ponds, except in the lowest dose in eutrophic and chemically polluted pond where the peaks preceded by a day. the responses of AP to the lowest doses of substrate did not differ between summer and winter, while the AP-peaks at higher doses were delayed by 2 days in summer. the concentrations of nitrate in vitro were the inverse and direct functions of the AP and dissolved oxygen of water. at moderate dose (0.75 gl-1) of peptone, both AP and dissolved oxygen at higher doses, and by AP at the lowest dose of peptone. 相似文献
855.
Pamela MacQuarrie Lawrence C. Nkemdirim 《Journal of the American Water Resources Association》1991,27(1):73-82
ABSTRACT: This paper examines the relationship between both potential (E*) and nonpotential evapotranspiration and equilibrium evapotranspiration (EQ) in an irrigated wheat field in southcentral Alberta, Canada. The control exercised by surface wetness and root reservoir moisture content in determining the value of the Priestley-Taylor constant a is explored. Also investigated is the relationship between a and the vapor flux fraction ET/(R-G) where ET is the actual evapotranspiration, R the net radiation, and G the soil heat flux. It is shown that evapotranspiration occurred at the potential rate (E*) when the available soil moisture (ASM) within the root zone was ≥3 percent. a varied from 0.84 for a dry soil to 1.49 for a saturated soil. The mean a for E* was 1.24. Surface wetness sustained evapotranspiration at the potential rate when such wetting exceeded 2mm d?1 following a period of prolonged drawdown of soil moisture, α and ET/(R-G) were positively correlated and this correlation strengthened with increasing soil moisture for constant values of the energy partitioning factor s+γ/s where s is the slope of the saturation humidity-temperature curve and γ is the psychrometric constant. ET=EQ when ETI(R-G) lay within the range of 0.59 to 0.82 corresponding to Bowen ratio (β) values of 0.22 and 0.69, respectively. 相似文献
856.
论重大危险源监控与重大事故隐患治理 总被引:19,自引:12,他引:19
吴宗之 《中国安全科学学报》2003,13(9):20-23
重大危险源是指工业活动中危险物质或能量超过临界量的设备、设施或场所。工业活动中重大火灾、爆炸、毒物泄漏事故 ,尽管其起因和影响不尽相同 ,但都有一个共同的特征 :其根源是存在大量的易燃、易爆、有毒物质或具有引发灾难事故的能量。重大危险源同重大事故隐患是两个既有联系又有区别的概念 ,前者强调设备、设施、场所中存在或固有的危险物质 (能量 )的多少 ,后者则可以认为是出现明显缺陷 (人的不安全行为 ,物的不安全状态或管理上的缺陷 )的重大危险源。从重大事故隐患治理到重大危险源普查 (申报 )、监控是预防重大事故理论与技术的进步 ,是从源头抓预防 ,是落实预防为主 ,关口前移的具体体现 ,也是国家安全生产法律、法规的强制要求。笔者论述了重大危险源监控、重大事故隐患治理与重大事故预防之间的区别与联系 ,用事故是能量意外释放的观点 ,论述了安全是相对的、危险是永存的、事故是可以预防的 ;分析了建立重大危险源监控体系与重大事故预防控制体系的几大要素 ,即危险源辨识、评价、分级管理与监控 ,应急救援等。 相似文献
857.
从熵增加的观点描述了事故的本质,剖析了人机系统的实质与特性,提出了风险熵与事故势的概念,给出了计算机风险熵与事故势的方法。结果表明,系统具有二重性。在系统运行期间,系统具有封闭体系的特性;在休整期间,系统具有开放体系的特性。事故是运行系统的必然发展趋势,是运行系统的固有属性,是一种自发过程。由于在系统熵增加的过程中信息及能量的交换,可以把事故定义为系统熵增加的结果。避免事故发生的原理是不断地向系统输入信息或负熵以抵消系统内部的熵增加。 相似文献
858.
Martha W. Gilliland Wanada Baxter-Potter 《Journal of the American Water Resources Association》1987,23(2):281-291
ABSTRACT: Bacterial densities (total coliform, fecal coliform, and fecal streptococci) and suspended solids in runoff from a feedlot, pasture, and corn field were measured. Densities of fecal coliform were highest from the feedlot but were 1000 to 10,000 times greater than the water quality standard for swimmable waters from all three land uses. Densities of fecal streptococci were highest from the corn field, which suggests that wildlife are the source of bacteria. Fecal coliform/fecal streptococci ratios distinguished cattle from wildlife as the source of bacterial pollution both among land uses and among seasons of the year. Suspended solids concentrations in runoff ranged from 423 to 925 mg/l and were highest from the corn field. A Geographic Information System (GIS), which utilizes a raster or grid-cell format, was developed to include algorithms associated with non-point source pollution. The system accepts digitally mapped information on soil type, topography, and land use. It calculates characteristics such as slope and slope length, and relates these characteristics to soils and land use parameters in order to produce three dimensional maps of runoff potential, sediment pollution potential, and bacterial pollution potential. It offers the advantages of retaining the geographic character of pollution potential information and of conveying in three-dimensional graphical terms the effects of topography, soil type, land use, and land management practices. 相似文献
859.
Dennis Nullet 《Journal of the American Water Resources Association》1987,23(6):1125-1132
ABSTRACT: This study presents an estimate of water balance components for Pacific atolls under average dimatological conditions. Figures show annual potential evapotranspiration, annual recharge for rain-fed and aquifer-fed vegetated areas, and the number of months that potential evapotranspiration exceeds actual evapotranspiration (indicating water stress) under average conditions. The method relies on the assumption that small islands have minimal influence on cloudiness and precipitation. The potential evapotranspiration is computed using the equilibrium evaporation concept, and estimates of monthly soil water storage and recharge follow Thornthwaite's bookkeeping method. Gradients in potential evapotranspiration run primarily north-south, though for the equatorial zone potential evapotranspiration declines from east to west, opposing the trend in rainfall. Recharge estimates range from 250 mm in the central Tuamotu Archipelago and zero in eastern Kiribati to over 2000 mm per year in the southern Caroline Islands (U.S. Trust Territory) and Solomon Islands. The sensitivity of the model to intra-month rainfall variability and a range of available soil moisture values is discussed. 相似文献
860.
关于安全科学基本概念及相互关系的研究 总被引:6,自引:3,他引:6
安全、危险、风险、事故、隐患等是安全科学和安全管理的基本概念。对于这些概念,至今仍有不同认识。本文从国内外研究现状出发,对上述基本概念及相互关系进行了分析探讨。Prof. 相似文献