串联稳压器基准误差放大电路的设计

针对串联型稳压器,设计了一种应用于串联型稳压器具有自建基准的新型误差放大电路。该电路具有构思巧妙,结构优化,易于集成及较高的开环增益,共模抑制比及交流特性的优点。通过验证,实测数据与仿真结果基本一致。     

反相集成电光调制器中共面波导的偏移效应

在实验室条件下，以ＬｉＮｂＯ３晶体为衬底，加工制作了各种不同程度的偏移性电极（共面波导），模拟光调制的反相结构。通过在微波频段下的实验研究．结果表明反相调制器共面波导偏移引起的微波传输损失是完全可以忽略的。     

Zero-inflated models for adjusting varying exposures: a cautionary note on the pitfalls of using offset

Zero-inflated count data are frequently encountered in public health and epidemiology research. Two-parts model is often used to model the excessive zeros, which are a mixture of two components: a point mass at zero and a count distribution, such as a Poisson distribution. When the rate of events per unit exposure is of interest, offset is commonly used to account for the varying extent of exposure, which is essentially a predictor whose regression coefficient is fixed at one. Such an assumption of exposure effect is, however, quite restrictive for many practical problems. Further, for zero-inflated models, offset is often only included in the count component of the model. However, the probability of excessive zero component could also be affected by the amount of ‘exposure’. We, therefore, proposed incorporating the varying exposure as a covariate rather than an offset term in both the probability of excessive zeros and conditional counts components of the zero-inflated model. A real example is used to illustrate the usage of the proposed methods, and simulation studies are conducted to assess the performance of the proposed methods for a broad variety of situations.     

RDS编码器的实现技术

介绍了广播数据系统（ＲａｄｉｏｎＤａｔａＳｙｓｔｅｍ，简称ＲＳＤ）利用现有调频立体声电台，在其基带频谱的上边界外（５７ｋＨｚ±２ｋＨｚ处）附加一块用ＤＰＳＫ方式调制的数据信息的频谱（一般称其为附加信近）多工地传送广播信息的基本原理，讨论了发端编码器的结构、实现方案以及波形成形截短的影响，并给出了一个实际模型。     

工序能力评价方法的探讨

本文介绍了工序能力的思想和工序能力指数的计算方法，并对现有的工序能力指数在计算中可能出现的问题进行了分析。分析了出现问题的原因并给出了调整工序能力指数的方法和解释。     

清除计算机病毒对.EXE文件的入侵

分析了计算机中文件型病毒对可执行文件的攻击方式 ,给出了清除方法 ,详细说明了清除步骤     

频偏条件下基于循环平稳的定时估计算法

研究了利用信号的循环平稳统计特性提取定时误差的估计算法,由于性能的优良是建立在大量统计信息的基础上,因而所需的观测时间长度较大,同时算法受频偏的影响也随观测时间长度的增大而增大。针对该特点,研究了频偏对算法性能的影响及存在频偏环境下算法中参数的选择。仿真结果表明,频偏对该类算法的影响不可忽略,尤其是在观测时间长度较大的情况下。实用中应结合具体频偏大小,合理选择参数取值。     

Public perceptions of risk to forest biodiversity.

This study examines the perceived risks to forest biodiversity and perceived effectiveness of biodiversity conservation strategies among the general public. It tests the hypotheses that perceived risk to forest biodiversity is influenced by cognitive factors (value orientation and knowledge) and social-cultural factors (such as gender and environmental membership) and that risk perceptions influence other cognitive constructs such as support for natural resource policy and management. Data were collected from a sample of the general public (n= 596) in British Columbia, Canada by mail survey in 2001. Results show that insects and disease were perceived as the greatest risk. Educating the public and industry about biodiversity issues was perceived as a more effective conservation strategy than restricting human uses of the forest. Value orientation was a better predictor of perceptions of risk and perceived effectiveness of conservation strategies than knowledge indicators or social-cultural variables. Examining the indirect effects of social-cultural variables, however, revealed that value orientation may amplify the effect of these variables and suggests that alternative paths of influence should be included. Perceived risk showed an inconsistent association with perceived effectiveness of conservation strategies.     

Effects of urbanization on species richness: A review of plants and animals

Many studies have described the effects of urbanization on species richness. These studies indicate that urbanization can increase or decrease species richness, depending on several variables. Some of these variables include: taxonomic group, spatial scale of analysis, and intensity of urbanization. Recent reviews of birds (the most-studied group) indicate that species richness decreases with increasing urbanization in most cases but produces no change or even increases richness in some studies. Here I expand beyond the bird studies by reviewing 105 studies on the effects of urbanization on the species richness of non-avian species: mammals, reptiles, amphibians, invertebrates and plants. For all groups, species richness tends to be reduced in areas with extreme urbanization (i.e., central urban core areas). However, the effects of moderate levels of urbanization (i.e., suburban areas) vary significantly among groups. Most of the plant studies (about 65%) indicate increasing species richness with moderate urbanization whereas only a minority of invertebrate studies (about 30%) and a very small minority of non-avian vertebrate studies (about 12%) show increasing species richness. Possible explanations for these results are discussed, including the importance of nonnative species importation, spatial heterogeneity, intermediate disturbance and scale as major factors influencing species richness.     

Urban soil ecology as a focal point for environmental education

Direct contact with the natural world is an essential element of environmental education and a key to developing environmental literacy and a stewardship ethic. But providing this experience can be challenging in urban environments where many people believe nature only occurs “outside” the city, and urban biota are often unwelcome and perceived in negative terms. Since 80% of the United States’ population lives in or near urban areas, conservation educators and practitioners need to find ways to make nature accessible to this audience, thereby creating a public who can make informed decisions about environmental issues. Soil systems are an important, under-utilized resource for urban environmental education. Soils are ubiquitous and thus easily accessible and their communities can be effective focal points for introducing all levels of ecology, from populations to ecosystems. Soil and litter taxa are also intrinsically interesting, with discoveries of new species still being made in urban areas. By studying urban soil systems, students can develop an enhanced sense of place and an appreciation of the natural world and their connection to it thereby strengthening environmental stewardship. An important role exists for urban ecologists to work with educators to impart enthusiasm for and to augment educators’ understanding of soil systems.