埋地热油管道埋深对土壤温度场的影响

长输管道沿线地质、水文等条件不同,管道埋深差别较大。相应埋深处的自然地温及管道周围的温度场也不同。若只考虑平均或当量深度来进行管道计算,会产生很大误差。使用数值方法将所考虑的数值模型更接近于实际冻土地质条件和非线性特性就显得格外重要。采用有限单元法,对不同埋深条件下的管道周围土壤温度场进行三维数值计算,结果表明,管道温度变化在一定程度上受埋深影响,尤其在冻土地区,地埋温差与管道周围土壤温差较大。     

Mass balance soil ingestion estimating methods and their application to inhabitants of rural and wilderness areas: A critical review

Quantitative soil ingestion studies employing a mass balance tracer approach have been used to provide a defensible means to estimate soil ingestion for human health risk assessments. Past studies have focused on soil ingestion in populations living in urban/suburban environments. There is a paucity of reliable quantitative soil ingestion data to support human health risk assessments of other lifestyles that may be predisposed to ingesting soil, such as agricultural workers or indigenous populations following traditional lifestyles. The results of a preliminary analysis of sampling and analytical variability that would result from assessing activities typical of populations in rural or wilderness areas and conducted over wide areas show that approximately 225 subject days would be required to detect a difference of 20 mg/d in soil ingestion. Given the typically small populations in these areas, future soil ingestion studies should be focused on specific activities with a high potential for soil ingestion.     

Error Characteristics of Microwave Soil Moisture Products based on Triple Collocation and Its Spatial-temporal Pattern

Soil moisture is an important state variable connecting the land surface-atmosphere system, and its information can be efficiently acquired by the new technique of microwave remote sensing. Accurate interpretation of the microwave soil moisture products qualities and in-depth understanding of their temporal and spatial distributions are important prerequisites for their successful application in earth science through data assimilation. In this study, three microwave soil moisture products, FengYun-3C(FY-3C), Soil Moisture Active Passive (SMAP) and Advanced Scatterometer(ASCAT), were evaluated over China based on the triple collocation (TC) method. The abilities of three products to obtain temporal and spatial variations of soil moisture were illustrated by Hovm?ller diagram. The results show that: (1) SMAP generally outperforms ASCAT and FY-3C, with highest TC-based signal-to-noise ratio(SNR) under different land use types. The TC-based SNRs are 1.668dB, -0.316dB and -2.182dB for SMAP, ASCAT and FY-3C respectively; and their correlation coefficients with ground observations are 0.514, 0.501 and 0.209, respectively. (2) The accuracies of FY-3C and ASCAT in Northwest China are overall higher than those in the southern China. All three products can capture the latitudinal and longitudinal gradients of soil moisture, whereas their seasonal fluctuations are higher than those of in-situ measurements. Among three products, FY-3C shows highest spatial gradient and strongest seasonal fluctuations. (3) FY-3C product performance is more susceptible to vegetation coverage than ASCAT and SMAP, but it outperforms ASCAT in barren areas. The results of our study could provide useful insights for assimilating microwave soil moisture products into land surface models to improve hydrological prediction.     

一种基于粒子群优化算法的组合预测模型

本文首先分析了若干传统的预测方法,提出了一种组合预测模型,在该模型中利用加权系数对各种预测方法进行组合,集成不同来源的预测结果,从不同的侧面反映整个预测过程,力图使预测结果更加精确。在各种预测方法加权系数的确定上,利用PSO快速全局优化的特点,可以减少试算的盲目性,提高模型预测的准确性。     

交流异步电动机槽配合的重要性

提高电机效率有不同的方式,从分析槽配合出发,叙述了其对效率的影响.     

实时交易模式下的日前电力市场出清

针对日前电力市场出清的制订过程是一个比较复杂的优化问题,提出了一种基于改进遗传算法的市场清算算法,在对水电机组进行合理处理后,通过二进制编码对机组开停机约束条件进行适当处理,使整个交易算法过程简化,最后用算例验证了该方法的可行性。     

结合灵敏度分析的变电站电压无功控制策略

提出一种二级协调的区域电压无功控制,并考虑全局的电压无功控制策略,对主站区域全网电压无功控制引进灵敏度来指导调整策略。在灵敏度分析的基础上,通过系统有功损耗对节点无功注入的灵敏度进行排序,选择灵敏度较大的数个变电站作为无功补偿节点。利用灵敏度分析选取优先补偿的变电站,实现了无功功率的就地补偿,减少了网络的无功功率流动;对于全网的变电站,根据设定的最优限值曲线,按照九区图判断各变电站的无功调压设备的工作点区域及启动区的上下限,仅对有越限的变电站按照五区图进行VQC装置的调控,既可减少控制变量的频繁操作,又可保证全网电压的质量和全网潮流的最优分布。     

NAO-1: Lunar Highland Soil Simulant Developed in China

A new lunar highland soil simulant, NAO-1, has been created in National Astronomical Observatories (NAO), Chinese Academy of Sciences. This simulant was produced by gabbro, which includes large quantity of feldspar (An>90). The simulant’s chemical composition, mineralogy, particle-size distribution, density, angle of internal friction, and cohesion have been analyzed and results demonstrated that most characteristics of NAO-1 are similar with lunar highland soil samples. NAO-1 will benefit the scientific and engineering research of lunar soil.     

基于循环神经网络的汉语语言模型建模方法

语言模型是语音识别系统的重要组成部分,目前的主流是n-gram模型。然而n-gram模型存在一些不足,对语句中长距信息描述差、数据稀疏是影响模型性能的两个重要因素。针对不足,研究者提出循环神经网络(Recurrent Neural Network,RNN)建模技术,在英语语言模型建模上取得了较好的效果。根据汉语特点将RNN建模方法应用于汉语语言建模,并结合两种模型的优点,提出了模型融合构建方法。实验结果表明:相比传统的n-gram语言模型,采用RNN训练的汉语语言模型困惑度(Per PLexity,PPL)有了下降,在对汉语电话信道的语音识别上,系统错误率也有下降,将两种语言模型融合后,系统识别错误率更低。