星载T/R组件的可靠性评估

星载SAR中T/R组件使用数量多,地面累计试验时间长,本文提出了综合运用Bayes方法和CMSR方法评估T/R组件可靠性。该方法先评估T/R组件各组成部分的可靠性,再评估整个T/R组件的可靠性,不需要单独做可靠性验证试验。经应用,该方法取得了良好的效果。     

“R部寻根”调查报告诞生记

10月21日晚,北京林业大学的学生环保社团山诺会举办报告会,向社会各界公布其暑期社会调查“R部寻根”的调查结果。所谓“R部寻根”指的是对北京部分地区的小商贩回收上来的可循环利用的垃圾走向进行调查。“R部寻根”暑期调查队队长张薇薇撰文讲述了“R部寻根”行动的始末。     

新型制冷剂R290热物性分析及试验研究

分析当前CFCs和HCFCs类替代制冷剂在性能上的优劣,认为天然制冷剂是今后发展的方向。通过对比认为目前R290与R22的各种热力学性质比较接近,分析了用R290替代R22的可行性,在简单改造原系统后可以用R290替代R22,并且达到环保和节能的效果,COP系数可提高12%左右。R290的可燃性在实际中是完全可以控制其安全性。R290价格低廉,具有良好的经济性。     

基于DEA的我国能源R＆D经费配置评价研究

在对我国能源R＆D强度分析的基础上，运用DEA理论的C^2R模型对我国能源产业及其5个行业2001--2010年的R＆D经费投入、产出状况进行了实证分析。研究中用R＆D经费存量值来代替当年的R＆D经费值，得到各年的R＆D经费配置的相对效率和规模收益情况，找出R＆D经费配置配置存在的问题，有利于对我国能源R＆D经费的投人产出结构进行分析，提出优化国家能源R＆D经费配置的对策和建议。     

制冷剂R134a生产技术

由西安金珠近代化工有限责任公司开发、陕西省环保局推荐的制冷剂R134a生产技术适用于汽车空调、家用电冰箱和商业制冷工质;PU及PS塑料发泡剂及医药、化妆品气溶胶喷剂等.     

浅析循环经济中的公众参与行为——从循环经济3R原则的视角切入分析

从分析3R原则的内涵入手,概括不同社会主体在循环经济发展中的参与行为,结合目前这些社会主体的环境意识现状,提出了促进参与行为实施的一些措施,以期这些社会主体都能积极的参与到循环经济的建设中来。     

安徽砀山水果产区近十年气候变化的R/S分析

基于1996—2005年的地面气象资料,应用R/S方法对砀山近十年平气温、降水和日照量等气候要素进行了分析。结果表明,砀山年平均气温、极端最高气温和极端最低气温均呈下降趋势,年降水量呈上升趋势,年日照量变化和缓,且具有较强的持续性。气候要素年际季节变化趋势表现为:冬、夏季平均温差减小,气温年较差有减小的趋势;降水夏季增加,其他各季节平均降水变率减小,各季节平均日照量变率减小。     

KLB型制冷剂

由上海申豹绿色制冷剂有限公司开发的KLB型制冷剂替代R12、R22、R502、R134a,适用于大小中央空调、汽车空调、冰箱、冷柜、饮水机等。主要技术内容一、基本原理以R32为基本组成,通过其他辅助原料,组成三元近共沸混合制冷剂。二、技术关键为了解决多元混合制冷剂泄露不均     

Remedia(R)滤袋——一种去除二(噁)英的新技术

随着垃圾焚烧发电工程的兴起,对尾气中二(噁)英的控制处理提出了严格的要求.基于"表面过滤"及"催化过滤"相关理论成功开发出的Remedia(R)覆膜催化滤袋产品,为最严格的粉尘排放及二(噁)英的控制提供了新技术.     

铬菁R——溴化十六烷基三甲铵分光光度法测定环境水中的微量铍

胶束增溶分光光度法测定微量铍是较之铬菁R(ECR),铬天菁S(CAS)、铍试剂Ⅲ更灵敏的方法。本文在此基础上研究了在溴化十六烷基三甲铵(CTMAB)存在下,用ECR分光光度法溯定微量铍的适宜条件。提出了一个重现性好,灵敏度高的分析测定环境水中微量铍的新方     

ANN OUTPUT UPDATING OF LUMPED CONCEPTUAL RAINFALL/RUNOFF FORECASTING MODELS1

ABSTRACT: Artificial neural networks (ANNs) are tested for the output updating of one‐day‐ahead and three‐day‐ahead streamflow forecasts derived from three lumped conceptual rainfall/runoff (R‐R) models: the GR4J, the IHAC, and the TOPMO. ANN output updating proved superior to a parameter updating scheme and to the ‘simple’ output updating scheme, which always replicates the last observed forecast error. In fact, ANN output updating was able to compensate for large differences in the initial performance of the three tested lumped conceptual R‐R models, which the other tested updating approaches were not able to achieve. This is done mainly by incorporating input vectors usually exploited for ANN R‐R modeling such as previous rainfall and streamflow observations, in addition to the previous observed error. For one‐day‐ahead forecasts, the performance of all three lumped conceptual R‐R models, used in conjunction with ANN output updating, was equivalent to that of the ANN R‐R model. For three‐day‐ahead forecasts, the performance of the ANN‐output‐updated conceptual models was even superior to that of the ANN R‐R model, revealing that the conceptual models are probably performing some tasks that the ANN R‐R model cannot map. However, further testing is needed to substantiate the last statement.     

An investigation of a heat pump system using CO2/propane mixture as a working fluid

In order to decrease the heat rejection pressure of heat pump using pure working fluid, CO₂ or R744, other natural component including hydrocarbons (R290, R600a, R600, R1270, R170, R601) and dimethyl ether (RE170) is added to CO₂, respectively, and then six binary mixtures are achieved. By environmental and thermodynamic comparisons, R290 is selected to be the most appropriate component candidate to mix with CO₂, and meanwhile to weaken the flammability and explosivity for pure R290. Then, the system performances of heat pump using mixture of CO₂ and R290 were experimentally studied when R290 is added to CO₂ with a small fraction, and compared with that of the pure CO₂. The experimental test rig is designed and set up for the transcritical heat pump system. When the refrigerant charge is variable, the heating coefficient performance, optimum heat rejection pressure, compressor power, mass flow rate of refrigerant, and total heat coefficient of gas cooler were researched. The variation ratios of heating coefficient performance and heating capacity with deviation from the optimum refrigerant charge were also investigated. The optimum refrigerant charge of CO₂/R290 is obtained and the research results show that the addition of R290 to CO₂ can efficiently reduce the heat rejection pressure and improve the system performance. The results in the present work could provide useful guidelines for the design and operation of heat pump system using CO₂-based mixture.     

Hyperspectral reflectance response of freshwater macrophytes to salinity in a brackish subtropical marsh

Coastal freshwater wetlands are threatened by increased salinity due to relative sea level rise and reduced freshwater inputs. Remote radiometric measurement of freshwater marsh canopies to detect small shifts in water column salinity would be useful for assessing salinity encroachment. We measured leaf hyperspectral (300-1100 nm) reflectance of freshwater macrophytes (cattail, Typha latifolia and sea oxeye, Borrichia frutescens) in a field study in a subtropical brackish (2.5-4.5 parts per thousand salinity, per thousand) marsh to determine salinity effects on visible and near-infrared spectral band reflectance and to identify reflectance indices sensitive to small (1 per thousand) changes in wetland salinity. For sea oxeye, floating-position water band index [fWBI = R(900)/minimum(R(930) - R(980)), where R(lambda) = reflectance at band lambda], normalized difference vegetation index [NDVI = (R(774) - R(681))/(R(774) + R(681))], and a proposed wetland salinity reflectance ratio (WSRR = R(990)/R(933)) were sensitive to salinity with R2 of 40, 35, and 65%, respectively (p < 0.01). For cattail, NDVI and photochemical reflectance index [PRI = (R(531) - R(570))/(R(570) + R(531))] were sensitive to salinity with R2 of 29 and 33%, respectively (p 相似文献   

Narrow-waveband reflectance ratios for remote estimation of nitrogen status in cotton

Tailoring nitrogen (N) fertilizer applications to cotton (Gossypium hirsutum L.) in response to leaf N status may optimize N use efficiency and reduce off-site effects of excessive fertilizer use. This study compared leaf and canopy reflectance within the 350 to 950 nm range in order to identify reflectance ratios sensitive to leaf chlorophyll (Chl), and hence N status, in cotton. Plants were grown outdoors in large pots using half-strength Hoagland's (control) solution until some three-row plots received a restricted supply of N. Treatments comprised control, 20% of control N at first flower bud (square) onward; 0 and 20% of control N at first flower onward; and 0% of control N at fruit-filling onward. Despite leaf N values ranging from 51 to 19 g kg-1 across treatments and sampling dates, a weak correlation was obtained between Chl and N (r2 = 0.32, df = 70). In general, N stress led to increased reflectance at 695 +/- 2.5 nm (R695) and decreased reflectance at R410, and changes in leaf N were best correlated with either R695 or R755 in leaves and either R410 or R700 in canopies. The strongest associations between leaf constituent and canopy reflectance ratio were Chl vs. R415/R695 (r2 = 0.72), carotenoids vs. R415/R685 (r2 = 0.79), and N vs. R415/R710 (r2 = 0.70). The R415 measure appears to be a more stable spectral feature under N stress, as compared with more pronounced changes along the reflectance red edge (690-730 nm). Multiple regression identified a three-waveband canopy reflectance model that explained 80% of the variability in leaf N. Results indicate that remote sensing of N status in cotton is feasible using narrow-waveband reflectance ratios that involve the violet or blue region of the spectrum (400 to 450 nm) and the more commonly featured red-edge region.     

研发能力与研发效率的比较研究——以河南省大中型工业企业为例

通过构建大中型工业企业研发能力与效率的评价指标体系，运用因子定权法，对河南省18个地市的大中型工业企业研发能力与效率区域差异进行了测度和分析。研究发现，河南省大中型工业企业研发能力与效率整体协调性差，部分地区研发能力的获取是以牺牲研发效率为代价的；自主创新支撑能力、资本投入、环境约束是影响河南省大中型工业企业研发能力与效率的关键因素，而人力资本投入权重相对较小，说明河南省大中型工业企业的研发软实力有待提高。     

Vegetative Ecological Characteristics of Restored Reed (Phragmites australis) Wetlands in the Yellow River Delta, China

In this study, we compared ecological characteristics of wetland vegetation in a series of restoration projects that were carried out in the wetlands of Yellow River Delta. The investigated characteristics include plant composition structure, species diversity and community similarity in three kinds of Phragmites australis wetlands, i.e. restored P. australis wetlands (R1, R2, R3 and R4: restored in 2002, 2005, 2007 and 2009, respectively), natural P. australis wetland (N) and degraded P. australis wetland (D) to assess the process of wetlands restoration. The coverage of the R1 was 99%, which was similar to natural wetland. Among all studied wetlands, the highest and lowest stem density was observed in R1 and R2, respectively, Plant height and stem diameter show the same trend as N > R2 > R1 > R3 > D > R4. Species diversity of restored P. australis wetlands became closed to natural wetland. Both species richness and Shannon–Wiener index had similar tendency: increased first and then decreased with restored time. The highest species richness and species diversity were observed in R2, while the lowest values of those parameters were found in natural P. australis wetland. Similarity indexes between restored wetlands and natural wetland increased with the restoration time, but they were still less than 50%. The results indicate that the vegetation of P. australis wetlands has experienced a great improvement after several years’ restoration, and it is feasible to restored degraded P. australis wetlands by pouring fresh water into those wetlands in the Yellow River Delta. However, it is notable that costal degraded P. australis wetland in this region may take years to decades to reach the status of natural wetland.     

Water treatment by aquatic ecosystem: Nutrient removal by reservoirs and flooded fields

Potential use of reservoirs and flooded fields stocked with aquatic plants for reduction of the nutrient levels of organic soil drainage water was evaluated. The treatment systems include 1) a large single reservoir (R1) stocked with waterhyacinth (Eichhornia crassipes), elodea (Egeria densa), and cattails (Typha sp.) in series; 2) three small reservoirs in series with waterhyacinth (R2), elodea (R3), and cattails (R4), grown in independent reservoirs; 3) a control reservoir (R5) with no cultivated plants; 4) a large single flooded field planted to cattails; 5) three small flooded fields in a series planted to cattails; and 6) a flooded field with no cultivated plants. Drainage water was pumped daily (6 hours a day, and 6 days a week) into these systems for a period of 27 months at predetermined constant flow rates. Water samples were collected at the inlet and outlet of each treatment system and analyzed for N and P forms.The series of reservoirs stocked with aquatic plants functioned effectively in the removal of N and P from agricultural drainage water, compared to a single large reservoir. Allowing the water to flow through the reservoir stocked with waterhyacinth plants with a residence time of 3.6 days was adequate to remove about 50% of the incoming inorganic N. Allowing the water to flow through a series of two small reservoirs, R2 and R3, with a residence time of 7.3 days was necessary to remove about 60% of the incoming ortho-P. Flooded fields were effective in the removal of inorganic N, but showed poor efficiency in the removal of ortho-P.Florida Agricultural Experiment Stations Journal Series No. 2320.     

Controlling Rhododendron ponticum in the British Isles: an economic analysis

What resources should be committed to the control of invasive species? This study is based on a survey of nature conservation and forestry authorities, wildlife trusts and private landowners which investigated the extent of the ecological and economic impacts of the invasive non-native plant Rhododendron ponticum in the British Isles. There are data on 52,000 ha of land affected by R. ponticum, more than 30,000 ha of it in nature reserves. For nearly all nature reserves, displacement of native species and habitat changes were both reported. In 2001, respondents controlled 1275 ha of R. ponticum at a cost of pound 670,924. To test the optimality of this, we apply a model of social expenditure. The external costs of R. ponticum control are estimated from the probability that it will spread to contiguous sites and the damage done on invaded sites. These are then used to calculate the socially optimal level of expenditure on R. ponticum control, and the funding gap it identified by comparing the result with current levels of expenditure. The results suggest that a socially optimal level of control effort requires a significant increase in social funding for R. ponticum control, although the size of the increase varies between landholders.     

BOOK REVIEWS

Book reviewed in this article:
MANAGING THE WATER ENVIRONMENT, Edited by Neil A. Swainson.
Carbonate Chemistry of Aquatic Systems, Theory and Applications, by R. E. Loewenthal and G. v. R. Marais.
An Introduction to Hydrodynamics and Water Waves, by Bernard LeMehaute.
Systematic Hydrology, by J. C. Rodda, R. A. Downing, and Frank M. Law.
Cost Benefit Analysis and Water Pollution Policy, by Henry M. Peskin and Eugene P. Seskin.