地理距离、方言文化与劳动力空间流动

本文基于百度迁徙大数据研究中国劳动力的空间流动，系统考察地理和文化对劳动力流动的影响。通过构造流动机会比率，基于引力模型和普通最小二乘法的研究表明地理距离和方言距离阻碍劳动力流动。在空间距离上，劳动力偏好邻近城市，地理距离每增加1%，劳动力的流动机会比率降低约0.6%。在空间位置上，劳动力倾向于在方言文化相近地域范围流动，方言距离每增加1%，劳动力的流动机会比率下降2%左右。通过构造两地年均降水量差距和小麦种植适宜度差距作为方言距离的工具变量，以两阶段最小二乘法估计缓解内生性问题，估计显示结论稳健。考虑普通话因素后方言距离的抑制影响依然稳健，但目的地的高普通话普及率显著发挥促进劳动力流动的引力作用。最后，本文得出持续推广普通话、加强交通建设和深化中等教育的政策建议。     

计算最大Lyapunov指数的推广小数据量法

在分析常用的计算最大Lyapunov指数小数据量法的基础上,研究了混沌吸引子时间轨道的不可逆特性,提出基于后向搜索和双向搜索计算最大Lyapunov指数的推广小数据量法通用经验公式。数值仿真表明,新方法比原来仅做前向搜索的小数据量法在计算准确度和抗噪声性能上更加优越。     

中国碳交易政策扩散的影响因素、路径差异与减碳效果研究——基于省域数据的实证分析

碳交易市场的建设有助于实现全球碳平衡,而碳交易政策扩散对于促进中国碳交易市场的持续健康发展有着重要的现实意义。在我国碳交易市场建设不断深化的情境下,有必要识别省域碳交易政策扩散的多维影响要素,检验不同扩散路径下的政策效果差异,总结政策扩散经验。文章基于省域面板数据,首先运用事件史分析法,通过Cox比例风险模型发现,能源政策的落实、地方政府的综合服务能力和社会创新能力是碳交易政策扩散的关键驱动要素;其次,利用合成控制法进一步检验,发现主动扩散地区的减排效果弱于试点扩散地区,试点扩散地区对主动扩散地区的激励和带动作用有限,试点成果尚未得到有效学习和复制。为此,在我国统一碳交易市场的建设过程中,应强化中央统筹协调与地方相关举措之间的协同配合,依托有力的政策驱动激发我国碳交易制度活力,提升碳减排效果,形成路径清晰、梯度有序的政策扩散机制,以稳步实现2030“碳达峰”、2060“碳中和”的目标。     

90年代以来中国夫妇年龄差变动趋势及其原因分析

夫妇年龄差的研究是人口学研究的一个重要领域。但目前的研究由于数据来源多样化,得出的结论不尽一致,关于年龄差的变化方向也没有形成定论。为此,本文利用我国三期妇女地位调查数据,对年龄差变动趋势进行分析。结果发现：我国同龄婚配的特点非常稳定,其比例维持在16％～17％之间。中国夫妇年龄差模式自90年代以来,发生了较大的变化,2010年中国传统的＂男高女低＂的婚配模式有所改变,这种＂男高女低＂婚姻明显下降,而＂女高男低＂婚姻明显升高,扣除同龄婚后二者平分秋色。其原因可能与我国出生性别比持续偏高和婚姻观念的转变等因素有关。     

以道独尊、兼收并蓄的可能性——黄老之学在大一统国家统治思想确立过程中的理论尝试

在汉初确立大一统国家统治思想形态问题上,黄老之学主张兼收并蓄,而其所以可能需要有道和道家的独尊。“小察”与“大理”之分是以道独尊的天道依据,人欲可因论则是道家独尊的人道依据。然而理论和现实的制约使得道家的虚体式的独尊不可能成为理想的统治思想模式。     

Estimating the number of clusters

Hartigan (1975) defines the number q of clusters in a d ‐variate statistical population as the number of connected components of the set {f > c}, where f denotes the underlying density function on R^d and c is a given constant. Some usual cluster algorithms treat q as an input which must be given in advance. The authors propose a method for estimating this parameter which is based on the computation of the number of connected components of an estimate of {f > c}. This set estimator is constructed as a union of balls with centres at an appropriate subsample which is selected via a nonparametric density estimator of f. The asymptotic behaviour of the proposed method is analyzed. A simulation study and an example with real data are also included.     

Tractable Consideration Set Structures for Assortment Optimization and Network Revenue Management

Discrete‐choice models are widely used to model consumer purchase behavior in assortment optimization and revenue management. In many applications, each customer segment is associated with a consideration set that represents the set of products that customers in this segment consider for purchase. The firm has to make a decision on what assortment to offer at each point in time without the ability to identify the customer's segment. A linear program called the Choice‐based Deterministic Linear Program (CDLP) has been proposed to determine these offer sets. Unfortunately, its size grows exponentially in the number of products and it is NP‐hard to solve when the consideration sets of the segments overlap. The Segment‐based Deterministic Concave Program with some additional consistency equalities (SDCP+) is an approximation of CDLP that provides an upper bound on CDLP's optimal objective value. SDCP+ can be solved in a fraction of the time required to solve CDLP and often achieves the same optimal objective value. This raises the question under what conditions can one guarantee equivalence of CDLP and SDCP+. In this study, we obtain a structural result to this end, namely that if the segment consideration sets overlap with a certain tree structure or if they are fully nested, CDLP can be equivalently replaced with SDCP+. We give a number of examples from the literature where this tree structure arises naturally in modeling customer behavior.     

选择千兆位以太网还是ATM

作为一种新技术 ,千兆位以太网技术在具有强大生命力的同时 ,也有着其不成熟的一面 ,在今后的高速联网技术市场上它与ATM(AsynchronusTransferMode)哪种技术将独执牛耳 ,目前还很难断言 本文从几个方面来比较一下千兆位以太网技术和ATM技术的各自特点