A column system for modeling bentonite slurry infiltration in sands

Pressurized bentonite slurry is applied on a tunnel face to form a filter cake to stabilize the tunnel face when the slurry shield excavates through the sandy soil. Failure of the tunnel face may be caused by a high permeable filter cake, which commonly has a long penetration distance of slurry in sands. A column system with a height of 680 mm and a diameter of 300 mm was developed to model pressurized slurry infiltration in sands. Pressure transducers were installed to estimate the hydraulic conductivity of the filter cake during slurry infiltration. The electrical conductivity of the leachate of collected samples was measured. Results show that the majority of fine particles in slurry are within the range 100–300 mm into the sand specimen. The time for forming an impermeable filter cake is about 300 s, which indicates the impermeable filter cake is hard to form during the excavation.     

非线性偏最小二乘法在催化剂建模中的应用

神经网络偏最小二乘法(NNPLS)被应用于一种甲烷氧化偶联多组分催化剂的鲁棒反应模型的建立. 重点研究了内层神经网络学习算法、激活函数、网络结构(包括隐含节点数、隐含层)、网络权值初始化及主元的选取原则等. 研究表明, 内层神经网络分别采用1-10-5-1,1-8-4-1,1-8-5-1, 1-7-4-1, 1-8-4-1, 1-8-6-1的拓扑结构是合适的; Levenberg-Marquardt方法被用于网络的学习算法可以加快学习速度; 同时采用了sigmoid函数为激活函数. 计算结果显示, 四主元可以满足建模的需要. 与单纯的神经网络催化剂模型相比, NNPLS方法压缩分解了变量, 减少了计算量, 同时使模型的推广能力得到提高, 有效地改善了直接神经网络建模过程中催化剂模型泛化能力较差的缺点.     

The power of statistical tests in science teachnig research

A calculation of the probability of rejecting H₀ when it should be rejected (power) was completed on each of the 66 applicable articles in Volumes 6 and 7 (1969, 1970) of the Journal of Research in Science Teaching. These power calculations utilized the effect size definitions and tables developed by Cohen (1969). The mean power of each article to detect small, medium, and large effect sizes was determined from its major statistical tests. These mean powers were then compiled and analyzed. The powers calculated for the different effect sizes were disturbingly low (small, 0.22; medium, 0.71; large, 0.87) but not generally as low as Cohen (1962) found in an analysis of another behavioral journal. Recommendations for improving confidence in research in science teaching is provided and centers on significant increases in sample sizes and an understanding of power and its relation to a, effect size and sample size.     

电力电子实验室资产定量化建模及管理措施

该文提出一种新的电力电子实验室资产定量化建模方法。该方法根据电力电子实验室资产的特点进行了定量化建模,能较好地评估电力电子实验设备的借用和运行情况,并形成相应的管理措施。实际应用表明,提出的管理措施能较好地对电力电子实验室进行资产管理,并在平衡设备损耗、优化设备使用效率上取得了良好的效果。     

基于向量式混合质点单元薄壳非线性分析方法的膜材褶皱形变模拟研究

研究目的：建立一种适用于理想膜结构可进行高精度褶皱形变模拟的稳定可靠的数值分析技术及方法。创新要点：根据薄壳理论,在向量式混合质点单元方法（VFPEM）薄膜计算理论的基础上,引入弯曲内力分析模型并与其进行组合,发展了一种能够描述膜材面外变形的新型非线性薄壳计算理论,同时给出了将其应用于褶皱形变模拟的关键求解技术。研究方法：1．针对薄壳计算模型中的弯曲内力,利用移动基础架构和逆向刚体运动的概念扣除刚体转动,在只含有节点独立转动自由度的单元变形坐标系下根据虚功原理和平衡条件进行计算;2．借助于薄壳非线性屈曲模拟方法,引入合理的初始扰动作为诱发理想平面膜材中形成褶皱的有效机制;3．采用拟动力显式数值积分技术求解质点运动方程,通过追踪质点平衡位置来获得稳态的褶皱构形。重要结论：采用本文模型和方法可以模拟薄膜结构在面内荷载作用下褶皱的分布模式、具体构形信息及应力状态,计算过程不存在收敛性困难,结果准确。     

Effect of modeling range on structural analysis for powerhouse of hydroelectric power plant by FEM

In this paper, three different modeling ranges were selected in the structural analysis for a hydropower house. The analysis was carried out using ABAQUS 6.6. The modeling range has a remarkable effect on finite element method (FEM) calculation result at the middle position of typical cross-sections where the concrete is relatively thin, and at the region close to turbine floor. If the ventilation barrel, floor slabs and columns above turbine floor are excluded from FEM model, the maximum rise difference of pedestal structure increases by about 24% compared with that of the whole model. It is indicated that different modeling ranges indeed affect FEM calculation result, and the structure above turbine floor in the FEM model should be included.     

多功能水泵控制阀的水锤防护特性及其应用

通过分析多功能水泵控制阀的水锤防护特性,并结合东风汽车公司水厂的泵房管道上的JD745X型多功能水泵控制阀的应用验证,指出此水泵控制阀是一种兼水泵控制、止回、消除水锤三种功能于一体的控制阀门,具有较广的应用前景。     

Study on a calibration equation for soil water content in field tests using time domain reflectometry

The crucial point in calibrating soil water content using the technology of time domain reflectometry (TDR) is to establish the relationship between the apparent dielectric constant and the water content. Based on a database, which included 45 kinds of soil samples and 418 data points from our own test data and relevant literature, an empirical calibration equation is proposed. Additionally, the influence of soil type, dry density of soil, compaction energy, pore fluid conductivity, and temperature on the calculated result for water content was also analyzed. Results show that the equation can offer an error of ±0.05 g/g for most soils encountered in geotechnical engineering. However, the estimation error given by the empirical equation becomes significant for soils with dry density less than 1.3 g/cm³, so the equation was modified to consider the influence of dry density. Both of the empirical equations can be used to test gravimetric water content using the TDR method conveniently and efficiently without calibration.     

Co-benefit of hazardous trace elements capture in dust removal devices of ultra-low emission coal-fired power plants

The co-benefit of hazardous trace elements such as mercury (Hg), arsenic (As), and selenium (Se) capture in dust removal devices of ultra-low emission coal-fired power plants was investigated. Feed fuel and ash samples collected from 15 different coal-fired power units equipped with ultra-low emission systems were characterized to determine the concentrations and distribution characteristics of trace elements. It was found that the low-low temperature electrostatic precipitator (LLT-ESP) and the electrostatic fabric filter (EFF) had greater abatement capacity for Hg than normal cold-side ESP (CS-ESP). Only 0.8%–36.1% of Hg escaped from LLT-ESP and EFF, whereas 42.1%–90.6% of Hg escaped from CS-ESP. With the employment of EFF and ESP (inlet temperature<125 °C), 72.3%–99.1% of As and 70.7%–100% of Se could be captured before the wet flue gas desulfurization (WFGD) system. The significance level of the effects on the abatement capacity for Hg, As, and Se in ESP were analyzed by the Pearson correlation analysis and grey relational analysis. The results indicated that the low inlet temperature of LLT-ESP had significant promotional effect on the simultaneous removal of Hg, As, and Se. The smaller particle size of fly ash can be conducive to the adsorption of hazardous trace elements. The inhibitory effect of sulfur content in coal was significant for the enrichment of Hg and Se in fly ash.     

Earth surface modeling for education: How effective is it? Four semesters of classroom tests with WILSIM-GC

This paper presents results from a randomized experimental design replicated over four semesters that compared students’ performance in understanding landform evolution processes as measured by the pretest to posttest score growth between two treatment methods: an online interactive simulation tool and a paper-based exercise. While both methods were shown to be effective at enhancing students’ learning of the landform concepts and processes, there was no statistically significant difference in score growth between the two instructional methods. However, the attitudinal survey indicated that students consistently favored the simulation approach over the paper-based exercise. With the simulation method, female students showed greater score growth than males, especially for test items requiring higher level thinking. This indicates that the visually rich interactive simulation tool may be integrated to better support female students’ learning in geoscience. Science major students generally outperformed non-science major students in terms of score growth, which suggests that background knowledge played an important role in realizing the potential of computer modeling in enhancing students’ learning. Sufficient scaffolding is necessary to maximize the effect of interactive earth surface modeling in geoscience education.     

基于IEC标准的电力数据仓库数据建模研究

传统的电力企业数据仓库的数据建模技术因没有统一的标准，造戍数据仓库中信息不一致，也影响了其信息的完备性，使数据仓库无法充分利用正在运行的计算机信息系统中的数据进行灵活、及时的数据分析。文章主要研究基于IEC-61970标；隹电力企业数据仓库数据建模技术，并使用这些技术解决电力企业数据仓库建设中数据集成的标准化问题，使电力企业数据仓库中的信息更加完备。     

A follow-up power analysis of the statistical tests used in the Journal of Research in Science Teaching

It has been two decades since the first power analysis of a psychological journal and 10 years since the Journal of Research in Science Teaching made its contribution to this debate. One purpose of this article is to investigate what power-related changes, if any, have occurred in science education research over the past decade as a result of the earlier survey. In addition, previous recommendations are expanded and expounded upon within the context of more recent work in this area. The absence of any consistent mode of presenting statistical results, as well as little change with regard to power-related issues are reported. Guidelines for reporting the minimal amount of information demanded for clear and independent evaluation of research results by readers are also proposed.     

世界淡水资源开发管理策略的数学建模与分析

根据水资源在全世界范围内的预计储量、探明储量、年度消耗量和价格等数据,建立了基于不可再生淡水资源消耗情况预测的灰色系统预测模型以及对水资源的合理规划与管理问题的非线性回归模型,检验了其精度,证明了模型的合理性,为有效利用和开放淡水资源提供了理论依据.     

Application of nonlinear fatigue damage models in power electronic module wirebond structure under various amplitude loadings

This paper presents mean fatigue lifetime predic- tion of a wire-bond structure model in power electronic module using a failure physics approach that integrates high fidelity modelling and reduced order modelling. Loading current with variable amplitudes is applied to a finite element model of simplified wirebond structures. The resulting accumulated fatigue damage due to random loads is predicted by using reduced order modelling based on failure physics, a cycle counting algorithm, and various nonlinear fatigue damage models widely used in the literature. The reduced order mod- elling approach based on failure physics uses prediction data for the electro-thermo-mechanical behaviour of the wire-bond design of a power module obtained through non-linear transient finite element simulations, in particular for the fatigue life-time of the aluminium wire attached to the silicon chip of the wire in the module. The reduced order models that capture the black box function of the accumulated plastic strain are used in pre- dicting the mean fatigue life time of the wire bond structure under random loads. One of the widely used cycle counting algorithms, rainflow counting algorithm, is used to count cycles of the temperature profile at the specific point of the wire bond structure in a power electronic module. The cycle data from the rainflow algorithm mean life time of the wire bond structure are predicted with various cumulative fatigue models. Non-linear cumulative fatigue models such as damage curve approach （DCA）, double linear damage rule （DLDR）, and double dam- age curve approach （DDCA）, and linear cumulative fatigue damage model such as Palmgren-Miner rule are used to predict the mean fatigue life of the wire bond structure, and the results are compared.     

Excel在萃取塔传质单元数数据处理中的应用

Excel作为功能极强的电子表格软件,可应用于某些工程分析与计算.以化工实验中的萃取塔传质单元数为例,选择不同的等份数n,实现了图解积分法的Excel计算,允许精度范围内得到了计算量最小的n值及相应的萃取塔传质单元数.     

我国近几年缺电原因分析和对策

分析了我国近几年来缺电的原因,提出了缓解目前缺电的可行性措施,对未来我国电力发展提了建设性意见。     

A method for assessing the treatment validity of tests in special education

Several tests in special education are used as a basis for describing education treatment. When tests are used in this fashion, it is necessary to assess their treatment validity, i.e., to assess the degree to which they enable educators to accurately prescribe an effective treatment. This article outlines a procedure for estimating the treatment validity of a test and uses two tests as examples.     

2001—2013年中国矿井水害事故相关性因素特征分析

为了进一步认清中国矿井水害事故现状及其相关因素特征,通过统计国家煤矿安全监察局煤矿事故查询系统公布的数据(资料日期:2001年1月1日—2013年12月31日),对2001—2013年我国发生的矿井水害事故的相关信息分层次、分类别统计,对以往公布的陈旧、错误数据进行了修正更新;总结了我国煤矿水害事故的类型;阐明了水害事故发生区域、发生时间、煤矿企业特征以及国家制定的法规政策等相关因素与煤矿水害事故之间的密切关系。根据不同类型水害事故的特点提出有效的技术防治路线,并对目前制约煤矿水害防治技术的关键问题进行了探讨。