Small signal modeling of GaAs PIN diodes aided by electromagnetic analysis

A systematic procedure is described for determination of GaAs PIN diode equivalent circuit models from measured S‐parameter data combined with an electromagnetic analysis of the feed structure. A new parasitic and intrinsic model topology is proposed, and found to be better suited than prior models for the particular GaAs PIN structures considered in this work. Models were developed for forward bias currents ranging from 0.01 to 100 mA, and example measured and modeled results are included to validate the approach. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 61–68, 2001.     

不含BPA的塑料更安全吗？

这篇短文是对另一篇文章的评论,关注的是化学材料安全性问题。发难者认为监管机构对新材料的审批过于简单,无法足以让公众感到这些材料更为安全。作者对此表明了自己的观点：鉴于围绕化学安全性的争论经过多年仍未有定论,我不认为业界及评论人士会就怎样的测试程度才算足够、以及如何为＂安全＂一词赋予确切的定义上达成一致。     

Bush u-turn on renewables?

Despite early indications from the Bush Administration that renewable energy was neither a top priority nor to be funded at levels seen in the Clinton Administration, there appears to be a slow back peddling on this issue. President George W. Bush's proposed energy programme has been encountering mounting hostility on Capitol Hill in Washington as well as significantly growing opposition among many Americans. Don Smith, US correspondent for Refocus magazine reports.     

Risk taking by adolescents with maladaptive behavior histories.

"High-risk" adolescents with maladaptive behavior histories and control adolescents (15–17 years of age) participated in a laboratory experiment that measured aspects of risk-taking behavior. High-risk adolescents had behavioral profiles entailing combinations of past substance use disorder, early onset substance use, conduct disorder, criminal history, and dropping out of school. A risk-taking task presented participants with "risky" and nonrisky response options. The risky response option offered a low probability of a large monetary reward or a high probability of a smaller monetary loss and resulted in a net loss of monetary earnings. The nonrisky option protected current earnings. High-risk adolescents chose the risky option more often, had lower overall earnings, and were more likely to persist in making (losing) risky responses following a single gain on the risky option. The data replicate previous findings with high-risk adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Novel last passage time based jitter model with application to low slew rate/high noise ring oscillator

In a ring oscillator, the behaviour in which the output voltage ramp (up/down) of its individual delay cell crosses the threshold, which triggers the next stage delay cell, is crucial in determining the timing jitter, and hence phase noise. Specifically, as the slew rate of the ramp decreases and/or the amount of noise contribution from the transistors in the delay cell increases, the voltage ramp (up or down) has a higher probability of crossing the threshold multiple times, before finally passing it at a time denoted as last passage time, which is more accurate than the conventional first passage time model. This multiple crossing results in a higher jitter. In the past, investigation in last passage time jitter model results in jitter expression that can only be calculated numerically and thus no design guidelines/insights are apparent. In this paper, a novel model is presented with a simple closed form formula, which shows the extra jitter, due to multiple crossing, adds a term that increases as a function of the fourth power of the noise strength/slew rate ratio. The formula is applied to a real life practical low slow rate/high noise ring oscillator which finds application, for example, in random number generator implementation. Corresponding transistor level simulation results agree reasonably well with the model. Furthermore, it is shown that, on example designs, the last passage time approach in this paper can lead to time jitter that is 100 % larger than that due to conventional first passage time model.     

Automated self-service modeling: predictive analytics as a service

Research into service provision and innovation is becoming progressively more important as automated service-provision via the web matures as a technology. We describe a web-based targeting platform that uses advanced dynamic model building techniques to conduct intelligent reporting and modeling. The impact of the automated targeting services is realized through a knowledge base that drives the development of predictive model(s). The knowledge base is comprised of a rules engine that guides and evaluates the development of an automated model-building process. The template defines the model classifier (e.g., logistic regression, multinomial logit, ordinary least squares, etc.) in concert with rules for data filling and transformations. Additionally, the template also defines which variables to test (“include” rules) and which variables to retain (“keep” rules). The “final” model emerges from the iterative steps undertaken by the rules engine, and is utilized to target, or rank, the best prospects. This automated modeling approach is designed to cost-effectively assist businesses in their targeting activities—independent of the firm’s size and targeting needs. We describe how the service has been utilized to provide “targeting services” for a small to medium business direct marketing campaign, and for direct sales-force targeting in a larger firm. Empirical results suggest that the automated modeling approach provides superior “service” in terms of cost and timing compared to more traditional manual service provision.     

聚丙烯固相法接枝改性

聚丙烯固相法接枝不饱和单体是一种简便易行的本体法技术。与其它接枝方法相比，具有成本低、接枝率高、时间短、无溶剂回收、不妨害接枝物的进一步应用等优点。本文介绍了聚丙烯固相法接枝不饱和单体的进展，并较详细地讨论了影响接枝反应的各种因素。     

Thermal alteration of a cyclic fatty acid produced by a flaxseed extract

Methyl 8-[2-(cis-pent-2′-enyl)-3-oxo-cis-cyclopent-4-enyl] octanoate (I) is the methyl ester of a cyclic fatty acid synthesized enzymically from an incubation of linolenic acid with an extract of flaxseed (Linum usitatissimum L.). A proposed trivial name for I is methyl 12-oxo-cis-10, 15-phytodienoate (12-oxo-PDA). The evidence presented indicated that compound I has thecis configuration of the carbon chains with respect to the cyclopentenone ring. Treatment with acid, base, or heat isomerized I to a second product (II) that has thetrans configuration of the carbon chains. Prolonged heat treatment of II yielded a third cyclic product, methyl 12-oxo-9(13),cis-15-phytodienoate (III).