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991.
全钒液流电池隔膜在钒溶液中的性能   总被引:6,自引:2,他引:6  
谭宁  黄可龙  刘素琴 《电源技术》2004,28(12):775-778,802
考察了Nafion、日-160、日-80、FYM(日本产Nafion膜)和均相膜5种离子交换膜的两个关键性能(渗透性和面电阻)及其影响因素,对均相膜的化学稳定性进行了初步研究,并对两种膜进行了改性。实验发现:均相膜的钒扩散系数最小,但面电阻较大,化学稳定性不好;用二乙烯苯(DVB)对均相膜改性,综合性能较好;减小电场可降低钒离子扩散,提高钒溶液中氢离子浓度可减小面电阻。  相似文献   
992.
粮食平房仓基础设计的偏心问题分析   总被引:2,自引:0,他引:2  
给出两组计算平房仓基础底面积的计算公式,分析按老规范进行偏心基础设计中因偏心距取值不当而出现的问题,同时根据新规范,以基础底面积最小为优化目标,针对影响基础偏心距的一些因素,分析在不同条件下基础偏心距对基础可靠度和经济性的影响,从而确定基础偏心距的合理取值.  相似文献   
993.
莱钢烧结成品整粒系统的三次筛分和四次筛分,一直用直线振动筛。随着烧结矿产量的增加,原直线振动筛因其处理能力低、筛分效率低、运行成本高等已不能满足生产要求。悬臂筛网振动筛具有动态筛孔,且可使物料充分接触筛面,体积小、耗能低、筛粉效率高,经现场适应性改造代替了原直线振动筛。应用表明,筛分指数由8%降低到了6%,满足了生产工艺要求,年效益为1394万元。  相似文献   
994.
通过对住区绿化环境存在的误区进行分析,提出规划设计时应予重视妁原则理念,以期能营造出良好的居住环境。  相似文献   
995.
分析了氧化铝熟料窑内衬的损毁原因,按照提高耐火材料性能,划分区域分类使用,满足工矿条件的宗旨,从使用、砌筑、操作三方面采取改进措施,使熟料窑内衬的平均使用寿命提高了1.5~1.8倍,取得了显著的经济效益。  相似文献   
996.
Four years of longitudinal data from 373 families participating in a randomized intervention-control clinical trial were used to examine whether intervention effects on adolescent alcohol and tobacco use trajectories were moderated by family risk, as defined by parental social emotional maladjustment. Consistent with earlier outcome evaluations based on analyses of covariance, analyses confirmed that both the Preparing for the Drug Free Years program and the Iowa Strengthening Families Program favorably influenced alcohol use index trajectories across the time frame of the study; only the latter program, however, evidenced positive effects on a tobacco use index. Concerning the primary research question, analyses provided no support for family risk moderation of any intervention effect. Findings indicate the feasibility of developing universal preventive interventions that offer comparable benefits to all families. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
997.
分析了电荷耦合器件(CCD)在空间和彩色(或灰度)的离散特性对面积测量的影响。通过统计特定区域的边界点和分析图像分割的效果,提出了一种评价CCD相关误差的方法。举例说明了图像分割方法对面积测量的影响很大,为此,讨论了正确使用CCD和提高面积测量精度的相应措施。  相似文献   
998.
A comparison of the performance of three feature extraction methods was made for mapping forest crown closure (CC) and leaf area index (LAI) with EO-1 Hyperion data. The methods are band selection (SB), principal component analysis (PCA) and wavelet transform (WT). Hyperion data were acquired on October 9, 2001. A total of 38 field measurements of CC and LAI were collected on August 10-11, 2001, at Blodgett Forest Research Station, University of California at Berkeley, USA. The analysis method consists of (1) conducting atmospheric correction with High Accuracy Atmospheric Correction for Hyperspectral Data (HATCH) to retrieve surface reflectance, (2) extracting features with the three methods: SB, PCA and WT, (3) establishing multivariate regression prediction models, (4) predicting and mapping pixel-based CC and LAI values, and (5) validating the CC and LAI mapped results with photo-interpreted CC and LAI values. The experimental results indicate that the energy features extracted by the WT method are the most effective for mapping forest CC and LAI (mapped accuracy (MA) for CC=84.90%, LAI MA=75.39%), followed by the PCA method (CC MA=77.42%, LAI MA=52.36%). The SB method performed the worst (CC MA=57.77%, LAI MA=50.87%).  相似文献   
999.
Wildland fires burn large areas of the earth's land surface annually, causing significant environmental damage and danger to human health. In order to mitigate the effects, and to better manage the incidence of such fires, fire behaviour models are used to predict, among other things, the likelihood of ignition, the rate of spread, and the intensity and duration of burning. A key input parameter to these models is the amount of water in the vegetation, described as the fuel moisture content (FMC). A number of studies have shown that vegetation indices (VI) calculated from red and NIR reflectances may be used to map spatial and temporal variation in FMC in a range of fire-prone environments, with varying degrees of success. Strong empirical relationships may be established between VI and FMC over grasslands, yet over shrublands and forests, the relationships are weaker. If FMC is to be estimated with greater accuracy and consistency than is currently achieved, it is necessary to fully understand the relative contribution that spatial and temporal variation in the various biophysical and geometrical variables make to reflectance variability at the leaf and canopy level.This paper uses a modelling approach to investigate the sensitivity of reflectance data at leaf and canopy level to variation in the biophysical variables that are used to compute FMC. At the leaf level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content, used to compute FMC, is greatest in the SWIR and NIR, respectively. Variation in FMC has no effect in the visible wavelengths. At the canopy level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content is heavily dependent upon the type of model used and the range of variation over which the variables are tested. In the longer wavelengths of the SWIR, the competing influence of variable leaf area index, fractional vegetation cover, and solar zenith angle is shown to be greater than that at the shorter wavelengths of the SWIR and NIR. Empirical relationships between the normalised difference water index (NDWI) and FMC are shown to be weaker than that with canopy water content. However, when the range of the variables under study is more limited, useful empirical relationships between FMC and remotely sensed VI may be established.  相似文献   
1000.
通过排水采集器模拟试验,研究了太湖地区不同施肥水平下,麦作期间农田氮素淋洗特点。结果表明,麦季氮素渗漏损失以NO3--N为主,占总氮量的36.2%~99.1%,平均高达82.9%,NO3--N淋洗量随施肥量的增加而增加。不同施肥水平及肥料种类,对于NO3--N淋洗有着不同的影响,在试验的施肥水平下,麦作期间氮素淋失对地下水存在潜在污染。  相似文献   
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