能源化工产业高级化与经济增长——兼论能源化工产业最优匹配

能源化工产业是重要的基础性产业，现阶段对能源化工产业高级化及其对经济增长影响研究的成果还较少。文章首先将能源化工产业分为能源开采业、能源加工业和化工产业三大产业，测算能源化工产业高级化水平，结果表明能源资源禀赋导致了能源化工高级化水平的“低端锁定”，能源富集区能源产业高级化水平远远低于非能源富集省份，能源化工产业空间错配现象突出。其次，实证检验能源化工产业高级化对经济增长的影响，结果表明提高能源化工高级化水平能够显著促进经济增长，且不同产业规模的能源化工产业高级化对经济增长的影响存在差异性。再次，采用滚动回归方法检验随着能源化工产业高级化水平和产业结构变动，能源化工产业高级化水平对经济增长影响的变动状况，探讨能源化工产业内部最优匹配问题，结果表明能源化工产业高级化水平在1.05-1.15之间、能源开采业占能源化工产业比重在0.20-0.40之间，能源化工产业高级化对经济增长的促进效应最大。最后提出优化能源富集区能源化工产业匹配度、促进化工产业富集区新产品和新技术研发以及缓解能源化工产业空间错配等方面的政策建议。     

微机选配机床挂轮

利用微机选配挂轮,可以快速、准确地选配出在机床备用挂轮限制下的传动比精度最高的挂轮组合,并进行齿轮啮合性校核,实现机床挂轮的优化组合。     

Asymptotics of cross-validated risk estimation in estimator selection and performance assessment

Risk estimation is an important statistical question for the purposes of selecting a good estimator (i.e., model selection) and assessing its performance (i.e., estimating generalization error). This article introduces a general framework for cross-validation and derives distributional properties of cross-validated risk estimators in the context of estimator selection and performance assessment. Arbitrary classes of estimators are considered, including density estimators and predictors for both continuous and polychotomous outcomes. Results are provided for general full data loss functions (e.g., absolute and squared error, indicator, negative log density). A broad definition of cross-validation is used in order to cover leave-one-out cross-validation, V-fold cross-validation, Monte Carlo cross-validation, and bootstrap procedures. For estimator selection, finite sample risk bounds are derived and applied to establish the asymptotic optimality of cross-validation, in the sense that a selector based on a cross-validated risk estimator performs asymptotically as well as an optimal oracle selector based on the risk under the true, unknown data generating distribution. The asymptotic results are derived under the assumption that the size of the validation sets converges to infinity and hence do not cover leave-one-out cross-validation. For performance assessment, cross-validated risk estimators are shown to be consistent and asymptotically linear for the risk under the true data generating distribution and confidence intervals are derived for this unknown risk. Unlike previously published results, the theorems derived in this and our related articles apply to general data generating distributions, loss functions (i.e., parameters), estimators, and cross-validation procedures.     

Finding the best treatment under heavy censoring and hidden bias

Summary.  We analyse male survival duration after hospitalization following an acute myocardial infarction with a large ( N =11024) Finnish data set to find the best performing hospital district (and to disseminate its treatment protocol). This is a multiple-treatment problem with 21 treatments (i.e. 21 hospital districts). The task of choosing the best treatment is difficult owing to heavy right censoring (73%), which makes the usual location measures (the mean and median) unidentified; instead, only lower quantiles are identified. There is also a sample selection issue that only those who made it to a hospital alive are observed (54%); this becomes a problem if we wish to know their potential survival duration after hospitalization, if they had survived to a hospital contrary to the fact. The data set is limited in its covariates—only age is available—but includes the distance to the hospital, which plays an interesting role. Given that only age and distance are observed, it is likely that there are unobserved confounders. To account for them, a sensitivity analysis is conducted following pair matching. All estimators employed point to a clear winner and the sensitivity analysis indicates that the finding is fairly robust.     

新经济时代企业采购战略研究

21世纪是新经济时代,新经济与传统经济不同,以经济全球化、竞争链条化和技术网络化为特征。新经济导致企业的竞争环境发生了变化,由过去企业间的竞争转变为供应链间的竞争,企业生存环境越加复杂和多变。为此,企业已不能单纯依靠降低内部运营成本来获取更大的利润。企业如何与供应商合作,如何选择正确的采购战略尤为重要。新经济时代的采购战略主要有：供应商整合战略、供应商的全面质量管理战略、全球采购战略、供应商的长期合作关系战略、供应商提早参与战略、供应商发展战略、在线逆向拍卖战略、集中采购战略、联合采购战略和电子采购战略。企业应根据自身的发展目标和资源以及本企业总的发展战略合理选择适宜的采购战略,这样才能有效地提高自身的竞争力,实现可持续发展。     

Large Matching Markets as Two‐Sided Demand Systems

This paper studies two‐sided matching markets with non‐transferable utility when the number of market participants grows large. We consider a model in which each agent has a random preference ordering over individual potential matching partners, and agents' types are only partially observed by the econometrician. We show that in a large market, the inclusive value is a sufficient statistic for an agent's endogenous choice set with respect to the probability of being matched to a spouse of a given observable type. Furthermore, while the number of pairwise stable matchings for a typical realization of random utilities grows at a fast rate as the number of market participants increases, the inclusive values resulting from any stable matching converge to a unique deterministic limit. We can therefore characterize the limiting distribution of the matching market as the unique solution to a fixed‐point condition on the inclusive values. Finally we analyze identification and estimation of payoff parameters from the asymptotic distribution of observable characteristics at the level of pairs resulting from a stable matching.     

企业家社会资本与企业成长阶段的匹配性研究

企业家社会资本是企业获得持续成长所需的不可或缺的资源。企业家社会资本可以从微观、中观和宏观进行层次界定,企业家社会资本与企业成长各阶段具有非常高的匹配关系,企业成长的不同阶段通过构建相应类型的社会关系网络,获取相应类型的社会关系网络关键资源,保证了企业的持续经营和健康发展。     

A matching prior for the product of normal means based on the modified profile likelihood

In this paper, we develop a matching prior for the product of means in several normal distributions with unrestricted means and unknown variances. For this problem, properly assigning priors for the product of normal means has been issued because of the presence of nuisance parameters. Matching priors, which are priors matching the posterior probabilities of certain regions with their frequentist coverage probabilities, are commonly used but difficult to derive in this problem. We developed the first order probability matching priors for this problem; however, the developed matching priors are unproper. Thus, we apply an alternative method and derive a matching prior based on a modification of the profile likelihood. Simulation studies show that the derived matching prior performs better than the uniform prior and Jeffreys’ prior in meeting the target coverage probabilities, and meets well the target coverage probabilities even for the small sample sizes. In addition, to evaluate the validity of the proposed matching prior, Bayesian credible interval for the product of normal means using the matching prior is compared to Bayesian credible intervals using the uniform prior and Jeffrey’s prior, and the confidence interval using the method of Yfantis and Flatman.     

A consistency result in general censoring models

In this paper we prove a consistency result for sieved maximum likelihood estimators of the density in general random censoring models with covariates. The proof is based on the method of functional estimation. The estimation error is decomposed in a deterministic approximation error and the stochastic estimation error. The main part of the proof is to establish a uniform law of large numbers for the conditional log-likelihood functional, by using results and techniques from empirical process theory.     

Do active labor market policies for welfare recipients in Germany raise their regional outflow into work?

While many studies estimate the effects of active labor market programs (ALMPs) on the participants’ labor market outcomes, far fewer studies are concerned with the effects of these policies on the regional job-matching process. We analyze which ALMPs are particularly effective at the regional level, as well as the role local labor market conditions play for their effectiveness. We find positive effects for a number of ALMPs, but for some of these the effects differ considerably between regions with high and low unemployment. This has important policy implications.