欧美农产品价格支持政策的演变与启示

欧美农产品最低价格和目标价格在农产品市场供求关系、进出口政策和政府财政能力等约束之下,长期密切配合,共同促进了欧美农产品产量和农民收入的稳定增长。保护性收购方式下的最低价格干扰了市场价格的形成,非保护性收购方式下的最低价格对市场价格的形成没有影响,目标价格有效维护了供求关系决定价格的市场机制。最低价格和目标价格的使用与农产品供求状况没有必然联系,而最低价格的执行方式由农业资源禀赋和农产品供求关系决定。我国农产品的最低收购价抬高了市场价格,但其“拖市”功能有利于稳定农产品生产,而目标价格的反周期功能可稳定农民收入。因此,为保障国家粮食安全,我国不能以农产品目标价格取代最低价格,而应分品种施策不同的农产品价格支持政策。     

民航地空通信自适应抗干扰系统设计与性能分析

在复杂电磁环境下,由于民航地空通信大频偏的要求,滤波器无法滤除波道内的干扰。针对此问题,提出了一种自适应抗干扰系统设计方法。对于落在波道内且与地空通信信号有效频带不重叠的干扰,首先对通信信号进行载波频率估计,然后使用自适应滤波方法进行干扰抑制;对于落在波道内且与地空通信信号有效频带重叠的恒包络干扰,首先重构载波信号,消除对恒包络信号估计的影响,然后根据恒包络信号的特性重构干扰信号并进行干扰分离。实验结果表明,该系统设计方法在不改变民航地空通信架构的前提下,抗有效频带外干扰的能力最大可以提升23.8 dB,抗恒包络干扰的能力最大可以提升39.4 dB,从而可以大幅提高航空飞行安全水平。     

论转型期我国煤炭企业产业链的整合与分化

煤炭企业的发展不仅受其本身的资源与能力的影响,还与其所在产业链的上下游企业的协作有关。煤炭企业应利用战略转型的时机,合理规划产业链的整合与分化,以谋求基于产业链效率的竞争优势。     

膜分离技术及其在废水处理中的应用

基于膜分离技术是一种新型高效的分离技术,且其过程无相变、能耗低、适应范围广,愈来愈为人们所重视,并在多个领域发挥着巨大的效能。介绍了膜分离技术的发展过程与现状,着重综述了近年来膜分离技术在废水处理中的应用,分析了存在的一些问题并对其发展趋势作了展望。     

转炉钢渣的弱磁选研究

研究了宝钢滚筒渣的矿物形貌、组成与结构特点，实验分析了试验用磁铁的磁场强度分布并研究了在不同磁场条件下滚筒渣的磁选效果。由结果可知,在低梯度弱磁场条件下，可对滚筒渣中铁粒、FeO、CaO进行有效分选；Fe2O3、CxAF、MgO和P、Mn、Al等弱磁性组元矿物解离度偏小，或与强磁性矿物连生，难以分选；钢渣矿物相组成中,纯铁相、RO相、铁方镁石相磁性较高，而铁酸钙相、方镁石相和硅酸二钙相为弱磁性。     

选煤厂破碎及破碎机械的性能分析

本文主要阐述了选煤厂物料进行破碎的作用、破碎的基本形式、破碎效果及破碎机的类型。分析了齿辊式破碎机、额式破碎机、冲击式破碎机和滚筒式破碎机的性能状况。     

传媒企业市场化改革探析——基于厦门广播电视集团制播分离的实践

从“网台分营”到“多元化、社会化”,中国广电人对“制播分离”进行了多方面的理论研究和实践探索。笔者以厦门广播电视集团节目中心制播分离的实践为基础,总结经验,在对制播分离的实质进行探索的同时,结合“中心制”管理的特点,概括制播分离过程中可能遇到的问题,并设计相应的解决方案。     

Common method bias in hospitality research: A critical review of literature and an empirical study

Common method variance has received much attention in the behavioral sciences. Nonetheless, scant scholarly effort has been invested in handling common method variance in hospitality research. This study investigates the current status of controlling for common method variance in hospitality research and assists researchers in taking appropriate actions. Study 1 shows hospitality researchers’ endeavors to control for common method bias through a critical review of literature published in four leading hospitality journals in the ten years from 2006 to 2015: International Journal of Hospitality Management, Journal of Hospitality & Tourism Research, Cornell Hospitality Quarterly and International Journal of Contemporary Hospitality Management. In Study 2, empirical investigations examine the effectiveness of a procedural remedy (temporal separation) and a statistical control (an unmeasured method factor approach) with two independent samples. The results of Study 1 reveal that most survey-related publications in the four journals fail to address or acknowledge common method variance. Moreover, only a limited number of techniques is found to be used to control for method variance. The findings of Study 2 suggest that temporal separation with a time lag of one day leads to a weak control for method variance; however, the use of an unmeasured method factor significantly helps control for method variance in the model.     

二氯苯生产技术进展与发展趋势

介绍了二氯苯生产方法、用途、市场需求及发展趋势,重点介绍了二氯苯异构体分离技术。针对国内对、邻二氯苯生产现状,提出一些发展建议。     

STATIC FUND SEPARATION OF LONG‐TERM INVESTMENTS

This paper proves a class of static fund separation theorems, valid for investors with a long horizon and constant relative risk aversion, and with stochastic investment opportunities. An optimal portfolio decomposes as a constant mix of a few preference‐free funds, which are common to all investors. The weight in each fund is a constant that may depend on an investor's risk aversion, but not on the state variable, which changes over time. Vice versa, the composition of each fund may depend on the state, but not on the risk aversion, since a fund appears in the portfolios of different investors. We prove these results for two classes of models with a single state variable, and several assets with constant correlations with the state. In the linear class, the state is an Ornstein–Uhlenbeck process, risk premia are affine in the state, while volatilities and the interest rate are constant. In the square root class, the state follows a square root diffusion, expected returns and the interest rate are affine in the state, while volatilities are linear in the square root of the state.