电子控制器整机产品热带海洋环境影响效应分析

为了研究电子控制器的热带海洋大气环境效应,选取西沙试验站对电子控制器整机产品开展棚下自然环境试验,试验过程中每天对电子控制器通电2个小时,通电过程中利用上位机实时监测电子控制器的功能性能,并采集控制器运行参数和控制器机箱内大气环境数据,定期对其宏观形貌进行检查并拍照记录。经过2年试验后,电子控制器外壳涂层出现脱落和起泡,机箱盖板屏蔽条出现多处断裂失效,机箱内电路板未出现腐蚀现象,电子控制器通电测试功能性能正常,现有防护措施可有效保护内部印制电路板与电子元器件,表现出良好的海洋环境适应性。     

土工离心机及振动台发展综述

土工离心机是土力学研究与岩土离心模型试验的重要设备.本文概述了土工离心机工作原理和国内外应用现状,并对离心振动台进行了介绍,最后对土工离心机的发展趋势作了展望.     

功率三级管热带海洋-寒冷环境时序影响效应分析

为了研究功率三极管在热带海洋-寒冷环境时序影响效应,采用热带海洋环境和寒冷环境时序试验的方法,将试验件放置于棚下机箱内模拟其使用环境,开展自然环境试验工作。试验过程中,定期对样品分析其外观及功能性能变化情况,样品在完成5个月寒冷大气和5个月热带海洋环境试验后,出现致使ICBO和ICEO参数超差现象,通过失效分析发现,导致功率三级管失效的原因为CI离子引起管壳局部腐蚀,生成氧化产物,导致引脚间漏电,上述试验结果可为其热带海洋-寒冷环境适应性设计改进提供技术支撑。     

用离心机校准加速度计

本文介绍了校准加速度计的几种静态方法.说明了离心机法的基本原理、误差分析、其注意事项以及可达到的精度.     

以离心机为主体的冲击试验方法

文章简要介绍用离心机进行冲击试验的试验方法，以及所遇到的问题。     

离心机试验机不平衡问题的模式识别方法研究

为解决离心机不平衡的判断问题,结合实际产品的理论分析,本文提出一种基于振动信号的模式识别方法。本文方法在离心机不平衡问题的理论分析基础上,首先根据分析得出的比例系数采集对应振动信号,其次将该振动信号作为实验数据与实际运行数据进行特征值分析、分类器辨识过程,得出实际的比例系数,随后计算出当前离心机运转过程中所存在的离心力,最终依据离心力大小判断离心机设备的不平衡程度。     

机载电子设备三防设计应用研究

对电子设备的三防设计进行系统性阐述,从原材料的选型控制、机箱结构设计、密封设计、异种金属搭接设计和表面涂镀层设计等方面进行分类讨论,以提高电子设备整体的耐三防性能,并对电子设备三防试验注意事项进行了初步总结,相关经验可供同类设备的三防设计及环境试验验证借鉴和参考。     

以离心机为主体的静态复合环境试验方法

文章介绍了利用离心机为主体进行的温度—线加速度和气动加载—线加速度静态复合环境因素试验技术,着重说明在这二项复合试验中遇到的主要问题。     

高加速寿命可靠性试验HALT技术研究

从研究开发HALT试验的背景出发,介绍了进行HALT试验的基本原理及其意义,并说明了该试验设备的各组成部分。同时指出了HALT试验可分为四个分段试验过程,对其分别进行了阐述,最后对HALT试验的实施步骤进行了分析,认为该试验是一个重复试验－失效－失效分析－改进并维修－再试验的过程。开展HALT试验技术及其应用的研究与工程实践,可在产品设计阶段快速消除设计缺陷,缩短研发时间和成本,迅速提供产品的质量和固有可靠性。     

基于线性规划模型的环境与可靠性试验室人力资源分配的算法

在环境与可靠性试验室日常测试试验过程中,如何合理地分配人力资源,以最优化的人力成本完成试验任务,是环境与可靠性人力资源管理研究的重要任务。借助于国内外人力资源分配经验并基于线性规划模型对其进行管理分析,提出合理的轮班制度方案。运用此方案可对控制人力成本、保障试验任务提供科学的依据。     

CENTRIFUGE MODELING OF ONE-DIMENSIONAL SUBSURFACE CONTAMINATION1

ABSTRACT: One-dimensional contaminant transport through a saturated soil is modeled using a 1.2-m radius geotechnical centrifuge. Small-scale physical modeling in the centrifuge is achieved in relatively short time, at stress distributions that are similar to those experienced in the prototype (actual site). A 0.05 mol/l of sodium chloride solution is used as a contaminant and conductivity cells measure the concentration of the contaminant throughout the porous medium. Scaling analysis for centrifuge modeling and 1-g modeling are briefly discussed and it is concluded that centrifuge modeling simulates the effect of molecular diffusion; however, scaling of the effect of mechanical dispersion may be violated in the centrifuge if the interstitial fluid velocity is high. Centrifuge test results show good agreement with the predicted relationship between the coefficient of hydrodynamic dispersion and the Peclet number using column tests. Centrifuge modeling can be used as a complement of numerical modeling although the effect of mechanical dispersion may be overestimated in the former.     

A novel wind speed forecasting model for wind farms of Northwest China

Wind resources are becoming increasingly significant due to their clean and renewable characteristics, and the integration of wind power into existing electricity systems is imminent. To maintain a stable power supply system that takes into account the stochastic nature of wind speed, accurate wind speed forecasting is pivotal. However, no single model can be applied to all cases. Recent studies show that wind speed forecasting errors are approximately 25% to 40% in Chinese wind farms. Presently, hybrid wind speed forecasting models are widely used and have been verified to perform better than conventional single forecasting models, not only in short-term wind speed forecasting but also in long-term forecasting. In this paper, a hybrid forecasting model is developed, the Similar Coefficient Sum (SCS) and Hermite Interpolation are exploited to process the original wind speed data, and the SVM model whose parameters are tuned by an artificial intelligence model is built to make forecast. The results of case studies show that the MAPE value of the hybrid model varies from 22.96% to 28.87 %, and the MAE value varies from 0.47 m/s to 1.30 m/s. Generally, Sign test, Wilcoxon’s Signed-Rank test, and Morgan--Granger--Newbold test tell us that the proposed model is different from the compared models.     

A stochastic approach for the operation of a wind and pumped storage plant under a deregulated environment

To improve the competiveness in the energy market, it is necessary that the wind power plants provide guaranteed power generation, although, it is not possible to forecast power availability from wind power plant accurately. This paper presents a stochastic model and solution technique for the combined operation of wind and pumped storage power plants to improve the power availability and increasing the profit considering uncertainties of wind power generation. In this model, uncertainties in wind data have been forecasted for grid connected day-ahead market using Weibull distribution model. The imbalances in the forecasted wind data and the market demand have been reduced by operating the pumped storage power plant. In this stochastic mixed integer problem, pumped storage plant can take the supply either from the grid or from the wind power plant for the pumping operation to store the energy in order to utilize this energy during peak hours for increasing the overall revenue. The reliability of the pumped storage is improved by replacing the conventional unit with the adjustable speed type pumped storage unit. In order to prove the optimality of the solution, two case studies were considered. In case study–I, scheduling is provided by operating the conventional pumped storage unit, whereas in case study–II, adjustable speed pumped storage unit has been used. It has been found that the adjustable speed pumped storage unit has further reduced the imbalance between generated power and demand. The complete approach has been formulated and implemented using AMPL software.     

Short-term wind speed forecasting based on random forest model combining ensemble empirical mode decomposition and improved harmony search algorithm

ABSTRACT

Wind speed forecasting plays an important role in power grid dispatching management. This article proposes a short-term wind speed forecasting method based on random forest model combining ensemble empirical modal decomposition and improved harmony search algorithm. First, the initial wind speed data set is decomposed into several ensemble empirical mode functions by EEMD, then feature extraction of each sub-modal IMF is performed using fast Fourier transform to solve the cycle of each sub-modal IMF. Next, combining the high-performance parameter optimization ability of the improved harmony search algorithm, two optimal parameters of random forest model, number of decision trees, and number of split features are determined. Finally, the random forest model is used to forecast the processing results of each submodal IMF. The proposed model is applied to the simulation analysis of historical wind data of Chaoyang District, Liaoning Province from April 27, 2015 to May 22, 2015. To illustrate the suitability and superiority of the EEMD-RF-IHS model, three types of models are used for comparison: single models including ANN, SVM, RF; EMD combination models including EMD-ANN, EMD-SVM, EMD-RF; EEMD combination models including EEMD-ANN, EEMD-SVM, EEMD-RF. The analysis results of evaluation indicators show that the proposed model can effectively forecast short-term wind data with high stability and precision, providing a reference for forecasting application in other industry fields.     

Discourses of on-farm wind energy generation in the UK farming press

As the owners of the majority of land in the U.K., farmers are well placed to contribute to renewable energy targets. Media coverage can both drive and reflect farmers’ views about renewable energy but has been largely unexplored to date. This article uses discourse analysis to examine the evolution of coverage of one form of renewable energy – on-farm wind – in the U.K. farming press from 1980 to 2013. We identified a diverse debate with five major discourses. On-farm wind turbines are alternatively represented as: profitable farm diversification opportunities; producers of clean energy; important for rural development and sources of conflict. Although press coverage predominantly encourages wind energy production, a further discourse advises farmers to ‘Proceed with Caution’. While emphasising images and values which have widespread affinity among U.K. farmers, the press have increasingly employed an economic frame, constructing wind energy generation as a farm diversification strategy. The most recent farming press coverage predominantly encourages an instrumental approach to wind energy, crowding out other (non-economic) rationales and marginalising local community concerns. This appears to reflect the financial orientation of recent policy support (particularly Feed-in Tariffs), and may have long-term costs in enabling sustainable energy production systems.     

温度试验方案设计及试验开展常被忽略的两个要素

温度试验是可靠性试验里面最重要的试验。通常认为,影响温度试验效果的要素有温度、停留时间、温变率等。而实际上,在试验方案设计和试验开展中,还有两个方面常常被忽略,即温度箱风速、样品的摆放。不考虑这两个要素,容易造成欠试验或过试验,达不到规定的激发和验证要求。本文通过试验分析了温度箱风速、样品的摆放对产品的影响,并分别给出相应规避策略。     

Location wise comparison of mixture distributions for assessment of wind power potential: A parametric study

Scientific literature discussed various types of mixture models and models derived from maximum entropy principle using short-term wind speed data for their relative assessment. The literature on suitability of these mixture models for long-term data is rarely available. However, for correct assessment of wind power potential both wind speed and wind direction are equally important. Therefore, in this paper, both wind speed and wind direction are simultaneously analyzed using several types of mixture distribution and compared the same with conventional Weibull distribution. For wind speed and wind power density assessment, the mixture distributions such as Weibull--Weibull distribution, Gamma--Weibull distribution, Truncated Normal--Weibull distribution, Truncated Normal--Normal distribution, proposed Truncated Normal--Gamma distribution and Gamma--Gamma distribution along with MEP-distribution are compared with conventional 2-parameter Weibull distribution. Similarly, for wind direction analysis, the finite mixtures of von-Mises distribution are compared with conventional von-Mises distribution. Judgment criteria include R², RMSE, Kolmogorov--Smirnov test and relative percentage error in wind power density. The sites selected are the three onshore locations of India, viz., Calcutta, Trivandrum, and Ahmedabad. The results show that for wind speed assessment, mixture distribution performs better than the conventional Weibull distribution for analyzing wind power density. However, location wise comparison of all mixture distribution is of prime importance. For wind direction analysis, finite mixture of two von-Mises distributions proved to be a suitable candidate for Indian climatology.     

Review of airborne emissions from agricultural fumigants: design and uncertainty considerations for the use of the integrated horizontal flux method

Ground-level area sources, such as those associated with the use of agricultural fumigants, waste disposal sites, wastewater lagoons, and other applications, present a challenge in terms of characterizing atmospheric flux as a function of time. Studies are costly in terms of field activities and laboratory analysis. The optimization of field study design, therefore, is essential to conduct cost-effective research. The collection of on-field profile data for airborne concentration, wind speed, and wind direction can be used in conjunction with the integrated horizontal flux (IHF) method to empirically compute complex source terms as a function of time. This paper focuses on complicating factors and field study design issues for the use of the IHF method. Insights and examples are drawn from five field research studies. The methods and results of characterizing the uncertainty and method precision in the emission fitting for the IHF method also are presented.     

SDJ/W25高低温恒湿环境试验箱

在科技高速发展的今天,越来越多的精密仪器需要进行高低温及湿热试验,以便对试品在给定环境条件下的行为能力作出评价。精密仪器往往要求低风速,低震动和高精度温场。本文介绍环境试验设备如何实现低风速、低震动下,温场高精度。