API Spec 15HP-1995《高压玻璃纤维管线管规范》的分析与介绍

本文介绍了高压玻璃纤维管线管规范的制定技术背景和主要特点,分析了前后两版的修订内容及原因.     

Symbolic regression for better specification

This note introduces the concept of symbolic regression (SR) to tourism and hospitality research. SR uses genetic programming to find the model that best fits the data without a need to pre-specify a functional form or to impose a certain model as a starting point. In other words, SR helps to uncover the intrinsic characteristics of the data at hand. Our view is that SR can serve as an improved method of testing for misspecification. In this note, we propose to derive the true functional form of the residual using SR. We then use this information to improve the forecasts of the linear regression model and, to perform hypothesis tests if needed.     

公共信息图形标志标准化的实践与探索

本文阐述了公共信息图形标志推广的意义，分析了上海公共信息图形标志的现状，介绍了上海绿化和市容行业与上海市质量技术监督局合作推动本市公园绿地公共信息图形标志设置规范的概况，论述了此项工作对上海构建闰际化现代城市的意义和思考。     

贵阳地区高校简化太极拳教学探讨

在贵阳地区高校体育教学中很多学校都把简化太极拳作为体育教学中的一项重要内容，但在教学中不同的学校对同一动作的教学规格不同，即使同一所学校，也存在不同的教师所做的动作有明显差异的情况，由于简化太极拳是规定动作，出现这种情况是不合理的。因此针对产生这种情况的原因进行分析并提出建议，为贵阳地区高校简化太极拳的教学和推广提供参考。     

Diagnostics cannot have much power against general alternatives

Model diagnostics are shown to have little power unless alternative hypotheses can be narrowly defined. For example, the independence of observations cannot be tested against general forms of dependence. Thus, the basic assumptions in regression models cannot be inferred from the data. Equally, the proportionality assumption in proportional-hazards models is not testable. Specification error is a primary source of uncertainty in forecasting, and this uncertainty will be difficult to resolve without external calibration. Model-based causal inference is even more problematic.     

Nonlinear analysis for forecasting currencies: are they useful to the portfolio manager?

The importance of a time-varying specification for both the return and the risk of financial assets is well known. The purpose of this study is to investigate if some of the most recently developed econometric models, combined with technical indicators often used by practitioners, can significantly predict future returns. While most studies have focused on either univariate series or in-sample analyses of a given econometric specification, this study considers a multivariate framework where a US based investor daily reallocates a portfolio of three currencies (Deutschmark, Swiss Franc and Japanese Yen). Series of three years out-of-sample forecasts are analysed in terms of risk and return and it is shown that some of the tested speciications can indeed signiicantly predict future daily returns and correlations over this three-year period.     

Evaluating asset pricing models using the second Hansen-Jagannathan distance

We develop a specification test and a sequence of model selection procedures for non-nested, overlapping, and nested models based on the second Hansen-Jagannathan distance, which requires a good asset pricing model to not only have small pricing errors but also be arbitrage free. Our methods have reasonably good finite sample performances and are more powerful than existing ones in detecting misspecified models with small pricing errors but are not arbitrage-free and in differentiating models that have similar pricing errors of a given set of test assets. Using the Fama and French size and book-to-market portfolios, we reach dramatically different conclusions on model performances based on our approach and existing methods.     

影响中美贸易的诸因素分析

本文采用2001年1月～2008年12月样本,在双边贸易引力模型的框架下,采用协整分析、向量误差修正模型等计量方法,在汇率和中美两国GDP等影响因素基础上,分析中国垂直专业化对于中国对美出口、中国自美进口和中美贸易差额的影响。研究结果表明,中国垂直专业化程度不断加深促进了中国对美出口、抑制了中国对美进口,加剧了双边贸易的不平衡。     

A specification test for the propensity score using its distribution conditional on participation

Propensity score matching has become a popular method for the estimation of average treatment effects. In empirical applications, researchers almost always impose a parametric model for the propensity score. This practice raises the possibility that the model for the propensity score is misspecified and therefore the propensity score matching estimator of the average treatment effect may be inconsistent. We show that the common practice of calculating estimates of the densities of the propensity score conditional on the participation decision provides a means for examining whether the propensity score is misspecified. In particular, we derive a restriction between the density of the propensity score among participants and the density among nonparticipants. We show that this restriction between the two conditional densities is equivalent to a particular orthogonality restriction and derive a formal test based upon it. The resulting test is shown via a simulation study to have dramatically greater power than competing tests for many alternatives. The principal disadvantage of this approach is loss of power against some alternatives.     

我国证券市场的规范与发展问题浅析

我国证券市场发展至今虽已取得不菲的成绩,但仍存在诸多问题。本文试图立足于我国证券市场现阶段发展的客观情况,对其所展现出的突出问题进行分析,并给出相应的建议,以期促进证券市场的健康快速发展。