POCSAG码的接收与软件译码方法

本文及时追踪世界物流产业发展中出现的第四方物流现象,论述了加入WTO后中国物流产业所面临的严峻形势——跨国公司意图垄断中国的第四方物流市场,而后提出了应对策略。     

OPTIMAL CONTINUOUS-TIME HEDGING WITH LEPTOKURTIC RETURNS

We examine the behavior of optimal mean–variance hedging strategies at high rebalancing frequencies in a model where stock prices follow a discretely sampled exponential Lévy process and one hedges a European call option to maturity. Using elementary methods we show that all the attributes of a discretely rebalanced optimal hedge, i.e., the mean value, the hedge ratio, and the expected squared hedging error, converge pointwise in the state space as the rebalancing interval goes to zero. The limiting formulae represent 1-D and 2-D generalized Fourier transforms, which can be evaluated much faster than backward recursion schemes, with the same degree of accuracy. In the special case of a compound Poisson process we demonstrate that the convergence results hold true if instead of using an infinitely divisible distribution from the outset one models log returns by multinomial approximations thereof. This result represents an important extension of Cox, Ross, and Rubinstein to markets with leptokurtic returns.     

Distributional effects of environmental taxes on transportation: evidence from Engel curves in the United States

Indirect taxes on transportation activities that pollute can correct externalities and close the gaps between private and social costs. However, policy makers often find such Pigou taxes difficult to implement because of political resistance due to possibly adverse affects on equity. For this reason it is important to assess the distributional aspects of environmental levies. This article estimates properties of the demand for transportation in parametric and non-parametric analyses of Consumer Expenditure Surveys for the United States and finds patterns in the resulting set of Engel curves. Private transportation using air flights and new cars has Engel elasticity above unity while public transportation via mass transit has Engel elasticity below unity. The findings can be interpreted in an important way since they show that a differentiated scheme of environmental taxes on transportation may function progressively. A Pigou scheme with larger taxes on modes of transportation that pollute more appears to coincide with larger levies on luxury modes preferred by richer households.     

Spurious welfare reversals in international business cycle models

Several papers have documented spurious welfare reversals: incomplete-markets economy produces a higher level of welfare than the complete-markets economy. This paper first demonstrates how conventional linearization can generate approximation errors that can result in welfare reversals. Using a two-country production economy, we argue that spurious welfare reversals are not only possible but also plausible under reasonable values for model parameters. This paper then proposes an approximation method that modifies the conventional linearization by a bias correction. This method can be easily implemented and approximates welfare as accurately as a second-order perturbation method.     

浙江省区域物流增量与GDP增量关系的计量分析

本文首先使用Granger因果关系检验法检验浙江省1958—2004年间的物流增量和GDP增量的因果性,结果发现本省GDP增量的变化是引起物流增量变化的原因。通过协整和误差修正模型对两者的长期和短期关系进行了研究。研究发现,浙江省区域物流增量与GDP增量间存在着可靠的协整关系。这说明随着浙江经济的快速持续发展,保持两者的均衡发展具有重要的意义。最后提出基本结论以及相关政策建议。     

信道估计偏差对空时编码的OFDM系统性能的影响

本文研究了采用空时编码的OFDM系统的性能，通过Monte Carlo仿真分析了系统性能和信道估计偏差对系统的影响。     

LZW压缩数据的不均一两分段误码保护编码

由T.A.Welch提出的LZW数据压缩方法已经被广泛地应用于文字压缩。然而，因为误码对压缩数据的危害很大，所以对压缩数据的纠错编码是十分重要且必不可少的。本文分析了误码对LZW压缩数据的影响，指出同样的误码对用于重建辞书的前一部分压缩数据的危害比对后面的其它数据的危害要严重得多，提出用一种不均一两分段误码保护编码方法，对用于重建辞书的前一部分压缩数据进行更好地保护。计算机模拟显示，该方法比传统的误码保护方法更有效。     

Illusory Price Increases after the Euro Changeover in Germany: An Expectancy-Consistent Bias

The aim of the present report is to review research demonstrating the role played by expectations for observed illusory price increases after the euro introduction in Germany. In laboratory experiments when participants are asked to estimate price changes in a restaurant following the euro introduction, the price estimates are found to be biased in the direction of the expectation of rising prices. The research also examines the extent to which a similar judgment bias is evident in other areas and how interventions counteract the bias. A further focus of the research is on the underlying process. In this respect the results show that the bias is based on a selective outcome correction process not previously described. Theoretical implications and practical implications for consumer policy issues are highlighted.

前馈技术在改善功率放大器线性中的应用

推导并分析了存在增益和相位跟踪等误差情况下,功率放大器前馈技术对三阶线性失真的改善情况,并从原理上论述了前馈技术的工作原理.前馈技术一般可将三阶互调降低10～30 dB,在新一代的抗干扰跳/扩频电台中有广泛应用.     

对外贸易与经济增长关系的实证分析--以山东省为例

对外贸易对经济增长的促进作用因不同的经济条件而有所不同。运用协整理论和误差修正模型，对山东省经济增长与对外贸易的相关性和因果关系进行实证检验的结果表明，山东省经济增长与出口和进口之间存在着长期的稳定关系，无论在短期内还是长期内，三个变量两两之间都具有显著的双向格兰杰因果关系，因此应继续坚定出口导向型的外向发展战略。