农民工影像塑造与文化身份

20世纪90年代末以来,＂三农＂问题成为日益突出的社会问题。在经济理性与城市文明追求中,农民工＂向城求生＂成为了时代主题,但在农民工影像塑造与＂后现代＂称谓的背后,农民工被＂看＂与被＂说＂的权力眼睛与权力话语无处不在。在中国城乡二元格局结构中,农民工文化身份得以揭示的同时,也造成了对农民工文化身份的遮蔽。     

中国经济到了刘易斯转折点了吗?——-来自贫困地区的证据

在过去的几年中,劳动力短缺已经成为日益关注的问题,尤其是在沿海地区。然而,关于中国是否到达刘易斯转折点而进入劳动力短缺时代依然存在很大的争论。大多数这方面的实证研究都建立在对总体劳动力供给和需求的估计上。由于劳动力统计数据的质量参差不齐,这些争论很难调和。工资数据比就业数据更为准确。基于对甘肃省农忙和农闲时期工资的发展演化模式的长期调研发现,无论其他影响因素是否被控制,实际工资水平总是不断地向上攀升。贫困地区实际工资在加速上涨,甚至农闲时期也是如此,表明剩余劳动力的时代已经结束。该发现对中国未来的发展模式具有重要的政策意义。     

二元劳动力市场供给的拐折模型分析

在二元分割的劳动力市场结构中,基于主次两类市场劳动力的质异性和市场选择,使得劳动力的供给呈弯曲向上的拐折曲线。一方面,在拐点以下的次要劳动力市场主体就业要优势于在主要劳动力市场就业;另一方面表明“刘易斯拐点”并没有提前出现,“民工荒”只不过是农村劳动力供给在该拐折曲线上的正常波动。     

社会认知的双重机制：来自神经科学的证据

随着对社会认知的脑与神经机制研究的不断深入,尤其是伴随具身认知科学的兴起,社会脑概念的提出与镜像神经元的发现都使得社会认知研究取得了长足进步,但同时也引发了新的争论。在神经科学领域内有关社会认知的主要发现与新近理论假设的基础上,社会认知双重机制假说得以产生。该假说认为,大脑中至少存在两套机制来完成对于他人心理状态与行为的理解。第一套机制是基于大脑镜像匹配系统的研究提出的——具身模仿（embodied simulation）;第二套机制即传统心理理论研究中所涉及的“心智化能力”（mentalizing）。该机制存在的证据除了传统心理理论领域中行为研究论据之外,更多的来自于与具身模仿系统相悖的实验研究。社会认知双重机制假说对于社会认知的研究有着重要的推动作用,但仍面临诸多问题需加以完善。     

蒙古族村落社会变迁与民族“双重边缘”阶层的出现——以部分蒙古族村落社会分层现状为例

在社会分层理论和＂代际公平＂理论视野下,以蒙古族村落社会结构变动现状为研究视点,对蒙古族＂双重边缘＂阶层出现的路径进行实证化分析的基础上,为其配备了这种＂资格＂的充足理由;进而对＂代际传递＂不能正常运行的诸多原因为张扬点,强调＂代际公平＂合理传递的无比重要性;最后以＂社会关爱＂理念出发,对他们刻不容缓地进行政府和社会援助视之为本研究的着力点。     

Density Estimation by Total Variation Penalized Likelihood Driven by the Sparsity ℓ1 Information Criterion

Abstract. We propose a non‐linear density estimator, which is locally adaptive, like wavelet estimators, and positive everywhere, without a log‐ or root‐transform. This estimator is based on maximizing a non‐parametric log‐likelihood function regularized by a total variation penalty. The smoothness is driven by a single penalty parameter, and to avoid cross‐validation, we derive an information criterion based on the idea of universal penalty. The penalized log‐likelihood maximization is reformulated as an ?₁‐penalized strictly convex programme whose unique solution is the density estimate. A Newton‐type method cannot be applied to calculate the estimate because the ?₁‐penalty is non‐differentiable. Instead, we use a dual block coordinate relaxation method that exploits the problem structure. By comparing with kernel, spline and taut string estimators on a Monte Carlo simulation, and by investigating the sensitivity to ties on two real data sets, we observe that the new estimator achieves good L ₁ and L ₂ risk for densities with sharp features, and behaves well with ties.     

Flexible Backup Supply and the Management of Lead‐Time Uncertainty

We consider replenishment decisions for a constant rate demand environment from a supplier with uncertain lead times. We study the potential use of a flexible backup supplier as an emergency response to accurate lead‐time information arriving at (or close after) the beginning of the demand interval and well after an original order with the stochastic lead‐time supplier has been placed. The emergency response decisions involve whether to order and how much from the flexible backup supplier, with the objective of minimizing the cost of meeting demand. We derive the optimal emergency‐response policy and clearly outline its implications on the optimized safety lead time of the original order placement and on the cost of meeting demand. We examine the impact on the use of the flexible backup supplier of factors like the arrival time of accurate lead‐time information and the response lead time of the backup supplier. We further study the potential benefits of the use of the flexible backup supplier in a dual role: as one of the two suppliers in a redundant supply system assigned to originally meet the demand and as an emergency response to later‐arriving lead‐time information. Our numerical studies illustrate the benefits from the use of the flexible backup supplier as an emergency response, but for reasonable purchase premiums and short lead times of flexible backup supply options, their use in a dual (regular and emergency response) role often leads to improved performance over safety lead‐time single and uncertain lead‐time supplier‐replenishment strategies. The benefits of the backup supply options are accentuated the higher the lead‐time uncertainty of the stochastic lead‐time supplier is.     

国债市场利率期限结构波动的对偶变换建模

本文针对传统利率期限结构拟合曲线存在过度波动问题,构建定价误差绝对距离和波动曲率双重最优化模型,借助对偶几何程序转换为在线性约束区域内的绝对距离最小化问题,并运用负指数平滑立方L1样条和计算几何逼近算法求解模型参数,通过负指数立方L1样条、NSS模型和B样条进行样本内拟合与样本外预测能力的比较,证实负指数立方L1平滑样条对利率期限结构波动的定价精确度、结构性拟合和样本外预测能力均有明显的优势,丰富了国债市场利率期限结构波动与定价的理论基础和研究方法。     

Strategic Sourcing in the Presence of Uncertain Supply and Retail Competition

This study develops an analytical model to evaluate competing retail firms' sourcing strategies in the presence of supply uncertainty. We consider a common supplier that sells its uncertain supply to two downstream retail firms engaging in price competition in a horizontally differentiated product market. The focal firm has a dual‐sourcing option, while the rival firm can only source from the common supplier. We assess the system‐wide effects of supply uncertainty on the focal firm's incentive to pursue the dual‐sourcing strategy. We find that the focal firm's dual‐sourcing strategy can create a win–win situation that leads to increased retail prices and expected profits for both firms. Furthermore, under certain conditions, we show that it is beneficial for the focal firm to strategically source from the common supplier, even if its alternative supplier offers a lower wholesale price. Overall, we identify two types of incentives for adopting the dual‐sourcing strategy: the incentive of mitigating supply risk through supplier diversification and the incentive of strategic sourcing for more effective retail competition.