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71.
在ATAD(Autothermal Thermophilic Aerobic Digestion,自升温高温好氧消化)工艺污泥稳定评价中引入TFS．提出“TVS/ TFS去除率”的概念,得出“TVS/TFS去除率”可以代替“VS(g)去除率”而成为一种新的污泥稳定指标的结论;采用数学微分的方法分析了“TVS/TFS去除率”和“VS(g)去除率”的数据误差问题,进泥TS为60g/L,TVS/TS为56％的运行条件下,前者的最大数据误差仅为3．16％,远小于后者的误差最大值15．45％,即引入TFS解决了“VS(g)去除率”数据波动大的问题;TFS的引入还节约了污泥稳定研究所需的时间和工作量。 相似文献
72.
This paper describes a method that minimizes the mean squared error (MSE) in estimating the spherical harmonic components of the surface air temperature field. The ratio of the MSE to the variance of the spherical harmonic component is expressed in terms of the length scale λ0, and the positions and weights of the measurement stations. The weights are optimized by the condition of minimizing the sampling error. To present an analytical example, we assume the homogeneous statistics of the temperature anomaly field, and take the low frequency approximation (i.e. ignoring the time dependence). The spectra of the temperature anomaly are the coefficients of a Fourier–Legendre series of the covariance function, and they are analytically derived from a linear noise forced energy balance climate model. Consequently, the MSE, the percentage sampling error, and the signal–noise ratio are computed for a given network of stations. Our results show that: (i) the sampling errors computed from both optimal weights and uniform weights increase with respect to the order of the spherical harmonic component; (ii) the sampling errors computed from optimal weights are significantly smaller than those from uniform weights for sufficiently dense networks. With about 60 reasonably positioned stations for sampling the spherical harmonic components 00 T10 and T11, one can get the sampling error below 10 per cent when the optimal weights are applied. An experiment with 210 stations produces the sampling errors of less than 10 per cent for the spherical harmonic components from T00 up to T54 相似文献
73.
质量保证与质量拉制是水质自动监测中十分重要的技术工作和管理工作，包括人员素质、运行与管理机制、试剂与标准溶液的配制及文件记录等。在实际工作中，监测人员可根据仪器的运行状况，定期对仪器进行校准、标准溶液的棱查、比对实验验证及试剂有效性检查，用以检查仪器的基线飘移情况。如果分析中出现一个异常值，它的前后均为正常值，这种数值大多是由仪器的进样、仪器内部试剂传输等原因所致，如果发生原因不明的数据异常，就要及时检查系统的各个环节并采集实际水样进行人工分析，直至查清原因，剔除异常值，并在周报中加以说明，以确保上报数据的准确性、精密性和可比性。 相似文献
74.
A modification of ranked set sampling (RSS) called moving extremes ranked set sampling (MERSS) is considered parametrically, for the location parameter of symmetric distributions. A maximum likelihood estimator (MLE) and a modified MLE are considered and their properties are studied. Their efficiency with respect to the corresponding estimators based on simple random sampling (SRS) are compared for the case of normal distribution. The method is studied under both perfect and imperfect ranking (with error in ranking). It appears that these estimators can be real competitors to the MLE using (SRS). The procedure is illustrated using tree data. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
75.
We simulated the sampling of 137Cs inventory (pCi/cm2) in Lower Watts Bar Reservoir to evaluate the effects of different sampling designs on the estimation of the magnitude of 137Cs contamination in the reservoir and to determine if the spatial pattern of contamination affected the performance of alternative sampling designs. Sampling designs evaluated were random, stratified random, systematic, and transect. These sampling designs were evaluated by creating multiple realizations of each design and sample size, and comparing the bias, variance, mean squared error (MSE), and per cent error in estimates of mean 137Cs inventory, 95th percentile of 137Cs inventory, and percentage of bottom sediments having 137Cs level > 400 pCi/cm2. Two alternative spatial maps of 137Cs inventory were used because the spatial distribution of 137Cs is uncertain. Increasing sample size beyond 250 for random and systematic designs resulted in little further reduction in MSE, variance, or bias of estimates of the three parameters. Variance generally contributed to MSE more than bias for random and systematic designs, whereas bias was important with transect sampling. The performance of random and systematic sampling varied minimally between the two maps. Transect sampling yielded inconsistent results due to bias not decreasing with increasing sample size. Stratification did not result in substantial reductions in MSE compared to simple random or systematic sampling. The per cent error of estimates of the percentage > 400 pCi/cm2 were larger than estimates of the mean or 95th percentile of 137Cs inventory. A staged sampling approach is recommended, with the first stage being determination of the spatial heterogeneity of the parameter of interest. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
76.
Particulate matter (PM), a component of ambient air pollution, has been the subject of United States Environmental Protection Agency regulation in part due to many epidemiological studies examining its connection with health. Better understanding the PM measurement process and its dependence on location, time, and other factors is important for both modifying regulations and better understanding its effects on health. In light of this, in this paper, we will explore sources of variability in measuring PM including spatial, temporal and meteorological effects. In addition, we will assess the degree to which there is heterogeneity in the variability of the micro‐scale processes, which may suggest important unmeasured processes, and the degree to which there is unexplained heterogeneity in space and time. We use Bayesian hierarchical models and restrict attention to the greater Pittsburgh (USA) area in 1996. The analyses indicated no spatial dependence after accounting for other sources of variability and also indicated heterogeneity in the variability of the micro‐scale processes over time and space. Weather and temporal effects were very important and there was substantial heterogeneity in these effects across sites. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
77.
光谱纯度是积分路径差分吸收激光雷达最重要的系统参数之一,光谱纯度直接影响CO2数据的探测精度.在模式研究中要求输入观测的CO2数据误差小于1×10-6,对激光器光谱纯度参数设计提出很高要求.本文采用有效吸收截面分析探测反演误差的方法,研究了由光谱纯度带来的CO2柱浓度探测误差,并基于窄带滤波器对光谱不纯能量的抑制作用,对不同带宽的窄带滤波器进行选择和分析,从而达到降低对光谱纯度的要求,提升探测精度的目的,最后讨论了由于窄带滤波器造成的能量衰减所对随机误差的影响.结果表明：当光谱纯度为99.9%,窄带滤波器带宽1GHz,透射率为0.86,脉冲能量为100mJ时CO2探测的系统误差小于0.084×10-6,随机误差小于0.02×10-6,满足探测精度要求. 相似文献
78.
航空维修人为差错影响因素分析中的模糊层次分析法 总被引：4，自引：2，他引：4
航空维修中的人为差错影响因素分析对于预防事故发生至关重要,如何定量分析及辨识出主要影响因素是亟待解决的问题.为此,结合航空维修实际,提出运用群组模糊层次分析法对人为差错影响因素进行量化排序和分类,归纳细化了影响因素层次体系,并给出了分析计算流程.以一起由维修人为差错所引发的航空事故为例进行了实证分析,结果表明:该方法能够辨识出航空维修中人为差错产生的主要影响因素,进而对制订最优事故预防方案,控制和减少该类事故的发生有积极意义.同时该方法对其他行业中的人为差错主要影响因素辨识有着一定的参考价值. 相似文献
79.
Ensembles of forecasts are typically employed to account for the forecast uncertainties inherent in predictions of future weather states. However, biases and dispersion errors often present in forecast ensembles require statistical post‐processing. Univariate post‐processing models such as Bayesian model averaging (BMA) have been successfully applied for various weather quantities. Nonetheless, BMA and many other standard post‐processing procedures are designed for a single weather variable, thus ignoring possible dependencies among weather quantities. In line with recently upcoming research to develop multivariate post‐processing procedures, for example, BMA for bivariate wind vectors, or flexible procedures applicable for multiple weather quantities of different types, a bivariate BMA model for joint calibration of wind speed and temperature forecasts is proposed on the basis of the bivariate truncated normal distribution. It extends the univariate truncated normal BMA model designed for post‐processing ensemble forecast of wind speed by adding a normally distributed temperature component with a covariance structure representing the dependency among the two weather quantities. The method is applied to wind speed and temperature forecasts of the eight‐member University of Washington mesoscale ensemble and of the 11‐member Aire Limitée Adaptation dynamique Développement International‐Hungary Ensemble Prediction System (ALADIN‐HUNEPS) ensemble of the Hungarian Meteorological Service, and its predictive performance is compared to that of the independent BMA calibration of these weather quantities and the general Gaussian copula method. The results indicate improved calibration of probability and accuracy of point forecasts in comparison to the raw ensemble and the independent BMA approach, and the overall performance of this bivariate model is able to keep up with that of the Gaussian copula method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
80.
上海市能耗与GDP大气污染的协整关系研究 总被引：1，自引：1，他引：1
采用计量经济学中的协整理论考察上海市能源消费量与经济增长、废气排放量、二氧化硫排放量之间的关系。结果显示,上海市能源消费只与经济增长、废气排放量之间存在长期协整关系,并建立了相应的长期均衡方程及误差修正模型。另外,对1978～2003年的能源消费与经济增长之间进行Granger因果关系检验,提出实现上海市经济-能源-环境和谐发展的措施。 相似文献