Minimum cost linear trend-free 12-run fractional factorial designs

Time trend resistant fractional factorial experiments have often been based on regular fractionated designs where several algorithms exist for sequencing their runs in minimum number of factor-level changes (i.e. minimum cost) such that main effects and/or two-factor interactions are orthogonal to and free from aliasing with the time trend, which may be present in the sequentially generated responses. On the other hand, only one algorithm exists for sequencing runs of the more economical non-regular fractional factorial experiments, namely Angelopoulos et al. [1 P. Angelopoulos, H. Evangelaras, and C. Koukouvinos, Run orders for efficient two-level experimental plans with minimum factor level changes robust to time trends, J. Statist. Plann. Inference 139 (2009), pp. 3718–3724. doi: 10.1016/j.jspi.2009.05.002[Crossref], [Web of Science ®] , [Google Scholar]]. This research studies sequential factorial experimentation under non-regular fractionated designs and constructs a catalog of 8 minimum cost linear trend-free 12-run designs (of resolution III) in 4 up to 11 two-level factors by applying the interactions-main effects assignment technique of Cheng and Jacroux [3 C.S. Cheng and M. Jacroux, The construction of trend-free run orders of two-level factorial designs, J. Amer. Statist. Assoc. 83 (1988), pp. 1152–1158. doi: 10.1080/01621459.1988.10478713[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]] on the standard 12-run Plackett–Burman design, where factor-level changes between runs are minimal and where main effects are orthogonal to the linear time trend. These eight 12-run designs are non-orthogonal but are more economical than the linear trend-free designs of Angelopoulos et al. [1 P. Angelopoulos, H. Evangelaras, and C. Koukouvinos, Run orders for efficient two-level experimental plans with minimum factor level changes robust to time trends, J. Statist. Plann. Inference 139 (2009), pp. 3718–3724. doi: 10.1016/j.jspi.2009.05.002[Crossref], [Web of Science ®] , [Google Scholar]], where they can accommodate larger number of two-level factors in smaller number of experimental runs. These non-regular designs are also more economical than many regular trend-free designs. The following will be provided for each proposed systematic design:

• (1) The run order in minimum number of factor-level changes.

• (2) The total number of factor-level changes between the 12 runs (i.e. the cost).

• (3) The closed-form least-squares contrast estimates for all main effects as well as their closed-form variance–covariance structure.

In addition, combined designs of each of these 8 designs that can be generated by either complete or partial foldover allow for the estimation of two-factor interactions involving one of the factors (i.e. the most influential).     

A Note on the Frequency Polygon Based on the Weighted Sums of Binned Data

We revisit the generalized midpoint frequency polygons of Scott (1985), and the edge frequency polygons of Jones et al. (1998 Jones, M.C., Samiuddin, M., Al-Harbey, A.H., Maatouk, T. A.H. (1998). The edge frequency polygon. Biometrika 85:235–239.[Crossref], [Web of Science ®] , [Google Scholar]) and Dong and Zheng (2001 Dong, J.P., Zheng, C. (2001). Generalized edge frequency polygon for density estimation. Statist. Probab. Lett. 55:137–145.[Crossref], [Web of Science ®] , [Google Scholar]). Their estimators are linear interpolants of the appropriate values above the bin centers or edges, those values being weighted averages of the heights of r, r ∈ N, neighboring histogram bins. We propose a simple kernel evaluation method to generate weights for binned values. The proposed kernel method can provide near-optimal weights in the sense of minimizing asymptotic mean integrated square error. In addition, we prove that the discrete uniform weights minimize the variance of the generalized frequency polygon under some mild conditions. Analogous results are obtained for the generalized frequency polygon based on linearly prebinned data. Finally, we use two examples and a simulation study to compare the generalized midpoint and edge frequency polygons.     

The Minimum Density Power Divergence Estimation for the Lognormal Density

In this article, we implement the minimum density power divergence estimation for estimating the parameters of the lognormal density. We compare the minimum density power divergence estimator (MDPDE) and the maximum likelihood estimator (MLE) in terms of robustness and asymptotic distribution. The simulations and an example indicate that the MDPDE is less biased than MLE and is as good as MLE in terms of the mean square error under various distributional situations.     

非等间隔动态面板数据模型：基于半差分的估计方法和应用

本文提出了非等间隔动态面板数据模型的估计方法,包括非线性最小二乘和最短距离估计法以及这两种估计方法的一步估计量,并且证明了这几个估计量的一致性和渐进正态性。我们使用数值模拟的方法验证了这些估计在有限样本中的估计精度,并且将这四种估计方法应用于实际的问题当中,最终得到了与以往的文献基本一致的估计结果。     

供应链库存商业信用协调的研究

本文研究由一个供应商和多个客户构成的以供应商主导的两级供应链,建立了以平均库存成本为目标函数的供应链供需同步库存模型。为了保证合理的收益分配,促进各成员加入供需合作的积极性,在模型中引入了商业信用机制,由供应商给予客户商业信用期而产生的机会成本(或利益)来平衡各成员间的利益。理论分析显示该模型存在最佳订货次数和最佳生产时间间隔,使供应链的总平均库存成本最小。最后利用算例分析和敏感性分析验证了商业信用的有效性。     

Discourse change and policy development in social assistance in China

Zhang H. Discourse change and policy development in social assistance in China Since the introduction of a new social assistance programme in urban China, the state was eventually able to expand the programme to rural areas as a further step towards integrating the development of social assistance in urban and rural areas. This article argues that the development of social assistance in China can be explained by the change of discourse among the officials and the elites in central government. The discourse on social assistance can be conceptualised in three periods: the urban‐first discourse (1999–2003); the discourse debate (2003–2007); and the urban–rural integration discourse (2007–present). Through scrutinising specific discourses and the policy development of social assistance in these three periods, it appears that in company with the change in the discourse process, rural social assistance was developed rapidly in order to construct an integrated social assistance system. The article concludes that discourse plays a significant role in Chinese social assistance policy development.     

武汉市农村最低生活保障制度的问题与建议——基于武汉市青山区的个案分析

在我国,最低生活保障制度为社会成员提供基本生活保障,是社会救助的基础和核心.文章基于对武汉市青山区农村低保个案的调查分析,了解武汉市农村最低生活保障制度的施行状况,发现在运行中存在保障能力不足、保障资金缺乏等几个方面问题.文章结合生态系统理论与社会支持网络理论提出相应的政策建议.     

融资结构与企业投资：理论分析及经验证据

本文首先从理论上剖析了负债的代理成本和相机治理机制.然后,以我国上市公司数据为样本,分别利用OLS的混合数据回归、GLS的随机效应和固定效应模型检验了融资结构与企业投资规模之间的关系.实证结果支持了负债代理成本假说,却未发现负债治理机制有效的证据.     

成本管理的新领域--浅析我国企业环境成本控制

本文针对我国面临的经济增长与环境问题日益突出的矛盾,从企业环境成本控制的角度,论述了环境会计逐步成为企业会计核算的重要组成部分,分析了环境成本控制的作用和方法,并对加强企业环境成本控制提出了相关建议。     

森林碳汇服务市场交易成本问题研究

清洁发展机制下造林再造林碳汇交易是森林碳汇服务市场的重要部分。然而,已有研究表明,由于森林碳汇服务市场交易的特殊性,其交易成本可能非常巨大而使交易难以进行。该文在对森林碳汇服务市场交易成本的构成、特征和大小进行探讨的基础上,分析了交易成本对市场规模的影响。最后,文章提出了降低森林碳汇服务市场交易成本的有效途径。