利用有源低通滤波器电路探讨抽样定理与信号恢复

以有源低通滤波器为例,探讨抽样定理与信号恢复原理,深入了解高职高专《信号与系统》的实验教学内容,使学生能够形象直观地观察离散信号频谱,了解其频谱特点。文章通过设计模拟信号源及时针信号源模块、模拟滤波器及抽样定理模块,引导学生全面具体分析抽样定理与信号恢复原理。     

我国企业物流金融发展抽样调查及对策探讨

随着物流业和金融业的融合,物流金融业务在中国如火如荼地开展起来,从简单的代收垫资,向物流授信方向发展。在企业发展急需资金支持的情况下,物流商业业务的开展,对供应链企业、物流企业、金融机构三方共赢有利。通过对我国主要地区物流企业物流金融发展情况进行抽样调查,对一些有代表性的问题进行分析,找出解决方案和发展对策。相信物流金融业务给我国企业带来融资效益的同时,必然朝着健康稳健的方向发展。     

浅析变频柜在注水泵上的应用

本文主要介绍了在油田注水过程中,面临注水压力高、水量大、电机功率大的情况,采用的变频调速装置--变频柜,对油田注水泵电机进行变转速调节,来改变用电设备的供电频率,进而达到控制设备输出功率的目的,实现注水泵对油田注水的有效、节能控制。     

NON-WELFARIST OPTIMAL TAXATION AND BEHAVIOURAL PUBLIC ECONOMICS

Abstract.  Research in behavioural economics has uncovered the widespread phenomenon of people making decisions against their own good intentions. In these situations, the government might want to intervene, indeed individuals might want the government to intervene, to induce behaviour that is closer to what individuals wish they were doing. The analysis of such corrective interventions, through taxes and subsidies, might be called 'behavioural public economics'. However, such analysis, where the government has an objective function that is different from that of individuals, is not new in public economics. In these cases the government is said to be 'non-welfarist' in its objectives, and there is a long tradition of non-welfarist welfare economics, especially the analysis of optimal taxation and subsidy policy where the outcomes of individual behaviour are evaluated using a preference function different from the one that generated the outcomes. First of all the object of this paper is to present a unified view of the non-welfarist optimal taxation literature and, second, to present behavioural public economics as a natural special case of this general framework.     

Evolution of International Statistical Standards via Life Cycle of Products and Services

This paper describes international statistical standards in the context of the product life cycle. To set the stage, the historical evolution of standardization is traced from the Xia Dynasty of China to the present. The transition from local standards geared for manufacturing to national and then international standards is highlighted with acceptance sampling standards. International statistical standards now cover a broad range of topics beyond acceptance sampling, so a scheme is needed to organize them into a coherent structure. The product Life cycle provides just such a framework. The product Life cycle (which is subsumed to include service, as well) is partitioned into four main "megaphases", namely: conception, development, delivery and maturity and death. Each megaphase is linked to relevant statistical methods in general and statistical standards in particular. A gap analysis identifies potential future directions of statistical standards developments and the attendant role that statisticians can continue to play in this arena.     

Supermarkets and Consumers in Africa

Abstract

Supermarkets in urban Kenya have risen from a tiny niche a half decade ago to a fifth of food retail, spreading well beyond the richer consumers to derive more than a third of their sales and half of their customers from low income and poor consumers. This paper explores the patterns and determinants of purchases of the overall food category versus fresh fruits and vegetables, over Nairobi consumer income strata, for purchases from supermarkets versus traditional retailers. Implications are drawn for development programs to help farmers be strategically positioned for change in the food markets facing them.     

A score test under logistic regression models based on case–control data

We propose a score statistic to test the vector of odds ratio parameters under the logistic regression model based on case–control data. The proposed score test is based on the semiparametric profile loglikelihood function under a two-sample semiparametric model, which is equivalent to the assumed logistic regression model. The proposed score statistic has an asymptotic chi-squared distribution under the null hypothesis and an asymptotic noncentral chi-squared distribution under local alternatives to the null hypothesis. Moreover, we show that the proposed score test is asymptotically equivalent to the Wald test under the logistic regression model based on case–control data. In addition, we demonstrate that the proposed score statistic and its asymptotic distribution may be obtained by fitting the prospective logistic regression model to case–control data. We present some results on simulation and on the analysis of two real datasets.     

The probability approach to general equilibrium with production

We develop an alternative approach to the general equilibrium analysis of a stochastic production economy when firms’ choices of investment influence the probability distributions of their output. Using a normative approach we derive the criterion that a firm should maximize to obtain a Pareto optimal equilibrium: the criterion expresses the firm’s contribution to the expected social utility of output, and is not the linear criterion of market value. If firms do not know agents utility functions, and are restricted to using the information conveyed by prices then they can construct an approximate criterion which leads to a second-best choice of investment which, in examples, is found to be close to the first best. We are grateful to participants in the 2006 Public Economic Theory Conference, Hanoi, the 2007 CARESS/COWLES workshop on General Equilibrium at Yale University, the 2007 SAET Conference at Kos, Greece, the NSF/NBER 2007 Conference on General Equilibrium at Northwestern University, and seminars at Rice University, the University of Southern California, Indiana University, and U.C. Davis for helpful comments. We particularly thank Jacques Drèze and David Cass for stimulating discussions, and a referee for helpful suggestions for improving the paper.     

Traditional versus non-traditional reinsurance in a dynamic setting

We consider a stochastic risk reserve process whose risk exposure can be controlled dynamically by applying proportional reinsurance and by issuing CAT Bonds. The CAT Bond payments are only partly correlated with the insurers losses. The aim is to minimize the probability of ruin. Using a two-dimensional diffusion approximation we obtain a controlled diffusion problem which can be solved explicitly with the help of the HJB equation. We present some numerical results and discuss to which extend the proportional reinsurance can be replaced by issuing CAT Bonds.     

Information criteria for GARCH model selection

In this paper, a set of appropriately modified information criteria for selection of models from the AR-GARCH class is derived. It is argued that unmodified or naively modified traditional information criteria cannot be used for order determination in the context of conditionally heteroscedastic models. The models selected using the modified criteria are then used to forecast both the conditional mean and the conditional variance of two high frequency exchange rate series. The analysis indicates that although the use of such model selection methods does lead to significantly improved forecasting accuracies for the conditional variance in some instances, these improvements are by no means universal. The use of these criteria to jointly select conditional mean and conditional variance model orders leads to performance degradation for the conditional mean forecasts compared to models which do not allow for the heteroscedasticity.