我国B2C电子商务支付方式及信用风险分析

个人支付是开展B2C电子商务的必备条件，是制约中国B2C电子商务发展的瓶颈之一。本文介绍了目前国内的支付体系和B2C电子商务支付方式，从交易的信用风险角度分析了我国B2C电子商务支付现状的成因，并提出了初步对策。     

Carbon tax simulations using a household demand model

The main objective of this paper is to analyse consumer response and welfare effects due to changes in energy or environmental policy. To achieve this objective we formulate and estimate an econometric model for non-durable consumer demand in Sweden that utilises micro- and macro-data. In the simulations, we consider two revenue neutral scenarios that both imply a doubling of the CO₂ tax; one that returns the revenues in the form of a lower VAT and one that subsidise public transport. One conclusion from the simulations is that the CO₂ tax has regional distribution effects, in the sense that household living in sparsely populated areas carry a larger share of the tax burden.     

葡萄球菌肠毒素B抗肿瘤作用的实验研究

探讨了葡萄球菌肠毒素B(SEB)对动物移植性肿瘤的抑制作用。以小鼠移植性肿瘤肝癌(Heps)、L2网织细胞瘤和肉瘤180(S180)为模型,环磷酰胺为阳性对照组,生理盐水为阴性对照组,观察不同剂量(5、10和20ng·Kg-1·d-1)SEB的抗肿瘤作用。不同剂量的SEB对小鼠肝癌(Heps)有明显抑制作用,抑瘤率分别为44.6%、46.7%和51.8%(P值均<0.05),对小鼠L2网织细胞瘤也有一定的抑制作用,抑瘤率分别为17.4%、44.7%(P<0.05)和44.1%(P<0.05)。SEB对小鼠S180的抑制作用不显著。结论是葡萄球菌肠毒素B(SEB)具有抗肿瘤效应,可作为一种有前途的抗肿瘤制剂进行研究。     

Market microstructure in a global B2B network

On‐line marketplaces raise several interesting issues, among them the relevance of location when content is digitized, and the assessment of a supplier's capabilities when buyers worldwide only have electronic contact with sellers. In global B2B on‐line marketplaces, market microstructures, i.e. which firms compete for the same customers, are thus likely to be influenced by how customers value location and firm capabilities in their decisions to do business with different suppliers on‐line. We suggest that both these sets of attributes will continue to matter on‐line—firms possessing similar capabilities, as well as firms that are similar in location by country, time zones or clusters, will compete for business from the same customers. We model the similarity in competitive positions between pairs of firms based on the overlap in their customer networks, using data on actual interactions between supplier and customer banks on an electronic trading system. Using QAP network regression techniques on the 100 largest banks in this industry, we find that similarity in capabilities influences who competes with whom, and that location still matters in a global B2B exchange. Interestingly, location influences who a firm's competitors are, but not where its customers are from. Copyright © 2001 John Wiley & Sons, Ltd.     

美国深空网的同波束干涉测量技术

讨论了美国NASA深空网(DSN)对深空飞船所采用的同波束干涉(SBI)技术概念和测量原理，并介绍了这一技术的应用和发展情况。     

Unit roots and infrequent large shocks: new international evidence on output

The nature and magnitude of the economic shocks that have affected the per capita GDP of 16 OECD countries are analyzed over a long period using the outlier method. Strong proof of infrequent large permanent and transitory shocks were found, essentially resulting from the two major wars in the twentieth century, the recession in the 1920s, the Great Depression, among others. We also examine the nature of the output trend by combining different tests of non-stationarity on different GDP series corrected by the outliers detected. It is shown that the per capita GDP series cannot reject the unit root hypothesis in 13 of the 16 countries examined. No conclusion could be drawn for the other countries because the test results were contradictory.     

Separating microstructure noise from volatility

There are two variance components embedded in the returns constructed using high frequency asset prices: the time-varying variance of the unobservable efficient returns that would prevail in a frictionless economy and the variance of the equally unobservable microstructure noise. Using sample moments of high frequency return data recorded at different frequencies, we provide a simple and robust technique to identify both variance components.     

Further Evidence on PPP Adjustment Speeds: the Case of Effective Real Exchange Rates and the EMS*

Two different approaches intend to resolve the ‘puzzling’ slow convergence to purchasing power parity (PPP) reported in the literature [see Rogoff (1996) , Journal of Economic Literature, Vol. 34.] On the one hand, there are models that consider a non‐linear adjustment of real exchange rate to PPP induced by transaction costs. Such costs imply the presence of a certain transaction band where adjustment is too costly to be undertaken. On the other hand, there are models that relax the ‘classical’ PPP assumption of constant equilibrium real exchange rates. A prominent theory put together by Balassa (1964, Journal of Political Economy, Vol. 72) and Samuelson (1964 Review of Economics and Statistics, Vol. 46) , the BS effect, suggests that a non‐constant real exchange rate equilibrium is induced by different productivity growth rates between countries. This paper reconciles those two approaches by considering an exponential smooth transition‐in‐deviation non‐linear adjustment mechanism towards non‐constant equilibrium real exchange rates within the EMS (European Monetary System) and effective rates. The equilibrium is proxied, in a theoretically appealing manner, using deterministic trends and the relative price of non‐tradables to proxy for BS effects. The empirical results provide further support for the hypothesis that real exchange rates are well described by symmetric, nonlinear processes. Furthermore, the half‐life of shocks in such models is found to be dramatically shorter than that obtained in linear models.     

Time Series Concepts for Conditional Distributions*

The paper asks the question – as time series analysis moves from consideration of conditional mean values and variances to unconditional distributions, do some of the familiar concepts devised for the first two moments continue to be helpful in the more general area? Most seem to generalize fairly easy, such as the concepts of breaks, seasonality, trends and regime switching. Forecasting is more difficult, as forecasts become distributions, as do forecast errors. Persistence can be defined and also common factors by using the idea of a copula. Aggregation is more difficult but causality and controllability can be defined. The study of the time series of quantiles becomes more relevant.     

Non‐linear Predictability of UK Stock Market Returns*

Linear predictability of stock market returns has been widely reported. However, recently developed theoretical research has suggested that due to the interaction of noise and arbitrage traders, stock returns are inherently non‐linear, whereby market dynamics differ between small and large returns. This paper examines whether an exponential smooth transition threshold model, which is capable of capturing this non‐linear behaviour, can provide a better characterization of UK stock market returns than either a linear model or an alternate non‐linear model. The results of both in‐sample and out‐of‐sample specification tests support the exponential smooth transition threshold model and hence the belief that investor behaviour does differ between large and small returns.