A Finite-Element-Based Solder-Joint Fatigue-Life Prediction Methodology for Sn–Ag–Cu Ball-Grid-Array Packages

A finite-element-based modeling methodology for predicting the part-on-board fatigue life of lead-free solder balls is presented. The computationally efficient methodology is calibrated with a wide assortment of published test data.      

TCAD Methodology for ESD Robustness Prediction of Smart Power ESD Devices

This paper presents a new method to predict the electrostatic-discharge (ESD) protection robustness of a device with technology-in-computer-aided-design (TCAD) simulations. Tested on different devices and two Smart Power technologies, the results are validated through electrical measurement and failure analysis. Failure current is always predicted with a good accuracy compared to technology spreading. In addition, the methodology provides a significant simulation time speedup compared to classical methods based on a temperature criterion     

A Stability Assessment Methodology

Weak transmission boundaries are shown to cause steady state and transient stability problems. The weak boundaries are defined by a loss of controllability property of the transient stability model. The loss of synchronism for fault contingencies can occur across these weak boundaries [7] if this boundary is weak compared to the other cutsets that encircle but are closer to the fault location. A loss of transient or steady state stability due to loss of generation contingencies will also occur across the elements in these weak boundaries. The inadvertant flows for inertial and governor response to loss of generation contingencies focus back to the region experiencing the loss of generation. These inadvertant flows cross the weak transmission boundaries and are shown to cause loss of generation and the formation of islands across the cutset of transmission elements that constitute the weak transmission boundaries. A method for determining and ranking the weak transmission boundaries of the transient stability model is developed. A method of determining and ranking the vulnerability of transmission elements is also determined. The measures used to determine the weak boundaries and vulnerable transmission elements for loss of generation or fault contingencies can be determined by summing the angle changes for all inertial load flow simulated loss of generation contingencies. The measures and the method for determining the weak transmission boundaries can be proven to detect the loss of controllability property of the transient stability model that define the weak boundaries.     

SCR脱硝催化剂宏观性能评估和寿命预测方法研究

针对实际烟气流场和飞灰沉积对选择性催化还原(SCR)脱硝催化剂寿命预测有较大影响的问题,在对大量现场和实验室测试数据进行研究基础上,提出了用SCR脱硝反应器潜能来表征和衡量实际烟气条件下的催化剂整体宏观性能。结合催化剂活性表征方法,构建了SCR脱硝催化剂宏观性能评估和寿命预测方法,用反应器潜能劣化函数宏观预测催化剂剩余寿命,再通过每层催化剂活性劣化函数,可得到具体的催化剂增加、更换或再生方案。以某1 000 MW机组为例,对NOx超低排放改造方案进行了比选,结果表明：低氮燃烧改造和旧催化剂再生均是提高脱硝装置性能的经济有效方法,二者相结合,效果最佳。     

国家标准委举行世界标准日纪念活动

10月14日世界标准日,国家标准委在浙江、北京两地分别举办了2009年长江三角洲世界标准日论坛和国务院有关部门、行业协会等参加的世界标准日座谈会。两地活动紧紧围绕“标准应对全球气候变化”的主题,大力宣传标准化工作在推动节能减排、保护生态环境、应对气候变化、服务科学发展中的重要作用,增强标准化工怍者的荣誉感和责任感,增强全民标准化意识。     

Efficient Low-Temperature Data Retention Lifetime Prediction for Split-Gate Flash Memories Using a Voltage Acceleration Methodology

In developing a fast statistical testing methodology to predict the postcycling low-temperature data-retention lifetime of split-gate Flash memories, word-line stress is used to accelerate the charge-gain effect responsible for bit-cell-current reduction among the tail-bits. To find out the voltage dependence on data-retention lifetime, various word-line stress voltages are performed to enhance the charge-gain effect of the erase-state cells. At an accelerated state, word-line stress lifetime tests can be completed within a much shorter test period and still provide accurate lifetime prediction for embedded Flash-memory products     

A Constructivist Simulation-Based Methodology for Teaching Mobile Communications

A constructivist simulation-based methodology for teaching mobile communication systems in the electrical engineering curriculum is reported. In this methodology, senior undergraduate students develop simulators under the guidance of an advisor, and the simulators are later used by other students to learn these particular technologies. Evaluations based on students' results and opinions demonstrate the effectiveness of the methodology for improving the teaching-learning process.      

电力市场日生产模拟新算法

在电力市场环境中,电力供需双方是根据电价高低改变供需数量,追求自身利益最大化,传统的电力系统日生产模拟算法是在确定的负荷预测基础上仅对发电侧进行优化管理。     

A Design Methodology for a Self-Oscillating Electronic Ballast

This paper presents a design methodology and analysis of electronic ballast employing the self-oscillating-command circuit. The self-oscillating electronic ballast is represented as a relay control system in order to determine its parameters using the describing-function method and an extended Nyquist stability criterion. Simulation and experimental results of the electronic ballast supplying a 40-W fluorescent lamp are presented in order to confirm the feasibility of the performed design methodology.     

一种T-S模糊控制器的设计方法

文章提出了一种比较系统化的T—S模糊控制器的设计方法，根据时间最优的原则确定误差最大、最小和居中时的模糊规则，然后根据模糊规则的前件，等比例地确定模糊规则的后件参数。用这种方法设计了交流调速系统的速度控制器，给出了仿真结果。     

一种电力有源滤波器及非线性控制方法

在对电力系统有源无功与谐波补偿的原理进行理论分析的基础上,运用其有关分析结果讨论一种电力有源滤波器主电路及带有变结构非线性电流控制的双闭环控制系统的结构和工作原理,通过Pspice软件进行了仿真研究,仿真结果证实了该系统及控制方法的正确性与可行性。     

A Digital Signal Processing Teaching Methodology Using Concept-Mapping Techniques

The main goal of this study is to develop a scientific method for designing a teaching methodology used in a basic digital signal processing (DSP) course. The proposed method is based on concept-mapping techniques, which applies multivariate statistic analysis to summarize the experience and knowledge of teachers involved in basic DSP teaching. As a result, a set of teaching methodologies is obtained. This result, as well as other information obtained related to the relative importance of the concepts to be covered, has been used to program the course. Moreover, different teaching tools have been developed to implement the proposed teaching methodology. Finally, the reliability of the method has been compared with similar studies to validate the proposed methodology.     

电力系统稳定控制方式探讨

电力系统安全性与经济性之间的矛盾随着电力系统的发展不断加剧,系统互联一定程度上缓和了这一矛盾,但大电网由于故障引起连锁反应而导致大面积停电的可能性也大大增加了。介绍了稳定控制装置的控制原理、结构组成和可采取的控制模式,提出了“集中管理、分区控制”的控制模式。     

以预测区间边界为约束的风电功率场景预测方法

针对现有不确定性预测方法存在保守性大而造成对系统调节能力要求较高的问题,提出一种区间估计和场景分析相结合的风电功率预测方法,首先通过区间估计得到以给定置信度包含未来风电功率真实值的短时波动区间,然后筛选出历史日中各时段落在区间包络线内的风电场景样本,再对筛选出的样本基于均值聚类算法进行缩减从而得到各时段的预测场景。最后通过风电预测算例和风火联合优化算例,证明了方法的可行性和有效性。     

循环流化床锅炉输入热量计算方法的探讨

综合考虑脱硫效率、钙硫摩尔比、脱硫剂成分等因素对输入热量的影响,建立了循环流化床锅炉输入热量的数学模型。适用于各型循环流化床锅炉及不同煤种和脱硫剂,较以往各种方法更全面、准确。     

Interventional: Methodology

Magnetic Resonance Materials in Physics, Biology and Medicine -     

基于改进SAC的倒立摆控制算法研究

针对倒立摆系统控制过程中易受外界干扰和自然不稳定的特点,以及深度强化学习SAC算法采样数据利用率较低和随机离线策略网络收敛较慢的问题,提出了一种结合近端经验采样和优化策略网络结构的改进算法PRER＿SAC。构建神经网络拟合函数,策略网络使用性能更优的Mish函数作为激活函数,设置自调节温度系数以增强智能体的探索能力;设计远、近两个经验池,及一种改变数据存放频率的训练策略,提高数据样本的利用率。通过仿真实验对比,所提方法在同等训练次数下所得回报值和算法收敛速度优于DDPG和SAC算法,同传统控制方法PID和LQR相比,有更好的控制效果。最后,对训练好的智能体加入角度扰动,可在2 s内被消除抑制,证明提出的算法具有较强的适用性。     

基于能量结构的电力系统振荡分析方法

传统的电力系统振荡分析方法具有模型参数依赖程度高、计算复杂、只适用于离线分析等不足。从Dirac结构出发,研究基于量测信号的电力系统振荡在线分析方法,尝试为此方法建立理论基础。首先介绍了能量结构的基本概念及其Dirac描述形式,给出了一般电力系统的能量结构;然后介绍如何基于能量结构分析特定端口外的未建模动态对系统振荡的影响;最后将提出的方法运用于不同精细程度的电力系统振荡源定位问题,以此验证所提出的方法的正确性、可行性和通用性。由于能量结构的概念适用于电力系统中的各种设备,因此文中提出的振荡分析方法具有一般性,并且该方法完全基于量测信号进行分析,所以计算快捷、可行性高,可应用于振荡源定位、振荡类型在线辨识和分散协调的振荡控制中。     

电网导线舞动研究方法的探讨

重点对电网导线舞动研究方法进行了分析,指出在导线舞动研究中的一些误区,对防止导线舞动措施的研究提供研究方向和思考方法,并对弹性间隔棒的使用和设计进行介绍。