电源模块的电磁干扰设计

电源设计中即使是普通的直流到直流开关转换器的设计都会出现一系列问题,尤其在高功率电源设计中更是如此。除功能性考虑以外,工程师必须保证设计的鲁棒性,以符合成本目标要求以及热性能和空间限制,当然同时还要保证设计的进度。     

Canada's reaction to climate change : Worrying about the US

In Canada, the federal government faces a difficult road ahead as it tries to come to terms with the country's commitment to Kyoto. Some say the accord should be ratified before the June meeting of the G-8 countries. Others contend that ratification at Rio+10 in South Africa in August is more reasonable. And now a third group wonders whether Canada should ratify it at all. There are clearly storm clouds on the horizon and the ambivalent approach to Kyoto in Canada drew a great deal of attention at the Globe 2002 Conference, which was held in Vancouver in March. Don Smith reports on the difficult issues that Canada faces as it confronts the Kyoto Protocol.     

Differential perceptions of counselor behavior: Replication and extension.

Conducted 2 studies with 141 undergraduates in an attempt to replicate and extend the 1976 findings of M. B. LaCrosse and A. Barak (1976). In both studies the Counselor Rating Form was shown to be sensitive to perceived differences among and within counselors of moderate and minimal levels of training/experience. In both studies a significant positive relationship was noted between perceived counselor expertness, attractiveness, and trustworthiness and willingness to refer oneself to the observed counselor for a variety of counseling problems. The provision of a common baseline for S judgment (Study 2) resulted in expertness ratings more consistent with actual counselor training/experience than those of Study 1. The implications of this latter finding for methodological improvements in counseling analog studies are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

让LED灯符合EMC及电能质量标准要求

引言 作为白炽灯的替换品,LED灯近年来才开始推出市场,但却面临着诸多难题.由于将LED功率驱动电路装入标准灯壳具有难度,因此早期的一些LED灯并没有内部滤波器,也就谈不上符合EMC标准.     

Myopic Social Prediction and the Solo Comparison Effect.

Four experiments explored the psychological processes by which people make comparative social judgments. Each participant chose how much money to wager on beating an opponent on either a difficult or a simple trivia quiz. Quiz difficulty did not influence the average person's probability of winning, yet participants bet more on a simple quiz than on a difficult quiz in the first 3 experiments. The results suggest that this effect results from a tendency to attend more closely to a focal actor than to others. Experiment 4 directly manipulated focusing; when participants were led to focus on the opponent instead of themselves, the effect was reversed. The discussion relates the results to other literatures including overly optimistic self-evaluation, false consensus, overconfidence, and social comparison. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification of steroid hormones in pomegranate (Punica granatum) using HPLC and GC–mass spectrometry

Although it has been known that pomegranate (Punica granatum L.) contains several steroid hormones, concrete experimental proofs about that have not been published until now. In order to identify and evaluate the contents of steroid hormones including estrone in pomegranate, we analyzed pomegranate seed, fruit juice and commercial preparations. We developed a reproducible and sensitive method for separation and identification of steroid hormones in pomegranate samples using both high performance liquid chromatography (HPLC)–PDA and gas chromatography (GC)–MS. In case of HPLC, an isocratic elution method using 35% aqueous acetonitrile solution at 1.0 ml/min with photodiode-array (PDA) detection at 225 nm and 254 nm was found to optimally separate and identify the steroid hormones from the pomegranate samples with a run time of less than 30 min. The pomegranate samples were comparatively analyzed to the HPLC results by GC/FID or GC/MS detection on a HP-1 (30 m length, 0.32 mm I.D.) with helium as carrier gas under the oven temperature control as follows: start 220 °C for 5 min, raising 5 °C per min, final 280 °C for 10 min. The HPLC and GC methods were successfully applied to the identification of steroid hormones in pomegranate samples. Our results suggested that there were no steroid estrogens including estrone, estradiol and testosterone in pomegranate seed, fruit juice and preparations. Consequently, we assumed that the previously reported analysts of pomegranate were misunderstood their analytical results according to either the estrogen-like effects or similarity of peak retention time and Rf values in experiments.     

Three-Dimensional Biomechanical Static Strength Prediction Model Sensitivity to Postural and Anthropometric Inaccuracies

This paper describes a detailed empirical comparison of a 3-D Static Strength Prediction Model with a set of strength performance data. The data were acquired from 29 male volunteers who performed four different static exertions (e.g., lift, push-down, pull-in, and push-out), with one hand and both hands using a force cell located at six different positions around the body. It is shown that the biomechanical static strength prediction logic is extremely sensitive to errors in postures and somewhat sensitive to errors in anthropometry used as inputs to the model. It does appear that with good postural data the model is capable of predicting a population's mean static strengths reasonably well.     

Blends and alloys of vinyl—technology and applications

The use of multiphase polymers is of growing importance because of their inherent economical and technological benefits. The basic characteristics of multiphase polymer blends and alloys are covered. The advantages of vinyl as a component are discussed in light of its ease of processing, inherent compatibility, fire resistance, weatherability, and a wide range of properties achievable. Blend morphology is reviewed and related to the mechanical properties. Typical examples of commercial materials and their application are reviewed.