API Spec 5L(44版)关于材料及试验的变化

针对API Spec 5L(44版)标准,简要分析了API 5L(44版)标准对于材料与理化试验方面与前一版本的变化。新版API 5L标准相比以前版本更加精简,实际使用更方便,在理化试验方面细节上变化较大,在焊管的实际生产应用中应予以注意。     

基于事件调度法的保障器材库存仿真控制系统设计

库存管理是供应链管理中的重要环节,起到缓冲、调节和平衡的作用。作者以库存控制基本理论及仿真基本理论为基础,结合保障器材库存控制的特点,研究设计基于事件调度算法的库存控制仿真系统,为提高保障器材库存管理水平提供有力的工具。     

由“国美事件”对中国家族式企业管理文化的反思

国美事件是中国家族式企业发展中的一个具有典型意义的事件。国美事件的发生反映了传统家族企业管理文化与现代企业管理文化的矛盾和冲突,揭示了我国传统家族企业管理文化的特征及其存在的种种弊端。家族企业健康、可持续发展必须重构企业文化,实现管理文化创新。     

价补分离政策下农户的玉米种植行为研究——基于吉林省宏观与微观数据分析

[目的]通过对价补分离政策实施前后吉林省玉米种植相关数据的分析,初步了解政策对农户种植行为产生的影响,进而探索吉林省农户在价补分离政策实施的第3年其玉米种植行为所受的主要影响因素。[方法]文章以吉林省玉米种植农户为研究对象,基于宏观与微观数据,采用多元Logistic模型分析农户玉米种植行为与政策之间的关系。[结果]价补分离政策改变吉林省农户的玉米种植行为。因价补分离政策实施导致的玉米价格下跌造成单位面积收益降低时,农户会寻求其他单位面积收益更高的作物,进而调整种植行为。[结论]玉米生产者补贴的发放对农户玉米种植行为调整具有引导作用。玉米优势产区与非优势产区的农户对价补分离政策不同的种植行为响应验证价补分离政策在保障粮食安全的同时调减玉米非优势产区玉米种植的作用。同时政策在实施过程中存在农户理解不到位及滞后性问题,因此从完善价补分离政策并提高农户对政策的认知程度等方面提出建议以更好地实现在调整玉米种植结构的同时稳定农户收入的政策目标。     

Random walk and efficiency tests in the Asia-Pacific foreign exchange markets: Evidence from the post-Asian currency crisis data

This paper empirically tests the random walk and efficiency hypothesis for 12 Asia-Pacific foreign exchange markets. The hypothesis is tested using individual as well as panel unit root tests and two variance-ratio tests. The study covers the high (daily) and medium (weekly) frequency post-Asian crisis spot exchange rate data from January 1998 to July 2007. The inferential outcomes do not differ substantially between the unit root tests and the variance-ratio tests when using daily data but differ significantly when using weekly data. With the daily data, both types of unit root tests identify unit root components for all the series and two variance-ratio tests provide the evidence of martingale behavior for majority of the exchange rates tested. With the weekly data, panel unit root tests identify unit root component for the exchange rates and, the unit root tests on a single series basis identify unit root component for 10 foreign exchange markets. However, the variance-ratio tests reject the martingale null for the majority of the exchange rates when using weekly data.     

基于BP神经网络的中、美贸易预测研究

根据中、美贸易的经济研究背景,分析中、美贸易重要影响指标,对其进行线性回归分析,发现中、美贸易额与各指标之间不是简单的线性相关,且各指标之间存在相互关系,所以不能用单一的线性回归模型进行预测。而BP神经网络具有非线性映射、自适应学习和良好的泛化能力等特征,运用BP神经网络模型对中、美贸易进行实证预测,大大提高了预测精度,取得了较好的效果。     

Stochastic Conditional Intensity Processes

In this article, we introduce the so-called stochastic conditionalintensity (SCI) model by extending Russell’s (1999) autoregressiveconditional intensity (ACI) model by a latent common dynamicfactor that jointly drives the individual intensity components.We show by simulations that the proposed model allows for awide range of (cross-)autocorrelation structures in multivariatepoint processes. The model is estimated by simulated maximumlikelihood (SML) using the efficient importance sampling (EIS)technique. By modeling price intensities based on NYSE trading,we provide significant evidence for a joint latent factor andshow that its inclusion allows for an improved and more parsimoniousspecification of the multivariate intensity process.     

Locally Most Powerful and Other Rank Tests for Independence – with a Contaminated Weighted Alternative

Several authors in the literature have attempted the quantification of the concept of stochastic dependence for bivariate distribution. Two weighted rank tests for testing independence against a weighted contamination alternative is proposed and their distributional properties are studied. We also derived a locally most powerful rank test for the alternative setting. The rank tests proposed are shown to be asymptotic locally most powerful for specific distributions.     

Underpricing,Share Overhang,and Insider Selling in Follow‐on Offerings

Prospect and information‐momentum theories predict that insiders can offer fewer shares in an initial public offering (IPO) to create informational momentum and obtain higher prices in follow‐on offerings. I find that dilution and insider participation in the IPO are negatively related to the number and size of follow‐on offerings, consistent with the prediction. However, insider selling in follow‐on offerings is positively related to IPO selling, contrary to the theories. Returns around follow‐on offering announcements are more negative for newly public firms than older firms, but for newly public firms do not differ by whether the announcement comes before or after the lockup expiration date.     

A multivariate Poisson mixture model for marketing applications

This paper describes a multivariate Poisson mixture model for clustering supermarket shoppers based on their purchase frequency in a set of product categories. The multivariate nature of the model accounts for cross-selling effects between the purchases made in different product categories. However, for computational reasons, most multivariate approaches limit the covariance structure by including just one common interaction term, or by not including any covariance at all. Although this reduces the number of parameters significantly, it is often too simplistic as typically multiple interactions exist on different levels. This paper proposes a theoretically more complete variance/covariance structure of the multivariate Poisson model, based on domain knowledge or preliminary statistical analysis of significant purchase interaction effects in the data. Consequently, the model does not contain more parameters than necessary, whilst still accounting for the existing covariance in the data. Practically, retail category managers can use the model to devise customized merchandising strategies.