严寒地区高速铁路混凝土基床聚氨酯保温特性试验研究

基于严寒区京沈客专朝阳试验段路基基床的温度监测资料分析,研究不同厚度聚氨酯保温板对高速铁路路基混凝土基床温度变化特性影响.测试结果表明:①铺设聚氨酯保温板能够有效阻断严寒区环境与路基基床间的热量传递,保温效果与板厚相关;②地温大多数时间呈阳高阴低现象,同时阴、阳坡路基温差波动幅度随埋深逐渐减小;③基床表层阴、阳面各测点的温度变化起始时间一致,而阴面的冻结时间比阳面晚一个月.由此表明,保温板能够有效降低环境与混凝土道床之间的热交换,但是对路基阴、阳坡的影响存在差异.建议在严寒地区高速铁路路基阳、阴坡可以采取不同厚度的聚氨酯保温板,减小阴阳坡地温差异,保持季冻土路基温度变化稳定.     

Bouncing Back from Extreme Weather Events: Some Preliminary Findings on Resilience Barriers Facing Small and Medium‐Sized Enterprises

Extreme weather events (EWEs) pose unprecedented threats to modern societies and represent a much‐debated issue strongly interlinked with current development policies. Small and medium‐sized enterprises (SMEs), which constitute a driving force of economic growth, employment and total value added, remain highly vulnerable to and ill prepared for such environmental perturbations. This study investigates barriers to SMEs’ resilience to EWEs in an attempt to shed light on enabling factors that can define effective organizational responses to non‐linear environmental stimuli. Relying on structural equation modeling and data gathered from 109 SMEs that recently experienced EWE impacts, we link the general concept of SMEs’ resilience barriers to EWEs with a series of elements to determine specific internal and external factors that contribute the most to EWE resilience. In particular, external barriers of institutional conditions and mechanisms of support and guidance as well as internal barriers of resources and managerial perceptions are found to be the most critical ones in determining resilience. The assessment offers essential research evidence for practitioners on SME management and sets forth linkages with current mechanisms for policy interventions towards an appropriate resilience agenda for SMEs. Copyright © 2018 John Wiley & Sons, Ltd and ERP Environment     

全低变工艺开发应用中的问题与对策

讨论了全低变工艺开发过程中遇到的一些问题和对策,对中、小氮肥企业进行技术改造具有一定的参考意义。     

Are gold,USD, and Bitcoin hedge or safe haven against stock? The implication for risk management

This study investigates whether gold, USD, and Bitcoin are hedge and safe haven assets against stock and if they are useful in diversifying downside risk for international stock markets. We propose a combined GO-GARCH-EVT-copula approach to examine the hedge and safe haven properties of gold, USD, and Bitcoin. We then examine the attractiveness of these assets in reducing stock portfolio risk by using downside risk measures estimated by the proposed approach and other competing models. We also evaluate the relative performance of the proposed model in reducing downside risk with the competing models. The findings of the study indicate that the USD is the most valuable hedge and safe haven asset closely followed by gold, while Bitcoin is the least valuable. It is also observed that the proposed combined approach performs best in reducing the portfolio downside risk. The findings of this study are of significance for portfolio managers and individual investors who wish to protect the portfolio value during market turmoil.     

软件限时开发方法的研究与应用

限时开发是快速应用开发的最佳实践之一。文章介绍了限时开发的基本概念和优点以及适用的项目范围,通过一个进销存软件的开发实例说明如何成功地应用限时开发方法。     

利用GARCH-M类模型和极值理论对上证综指的研究

金融时间序列具有分布的厚尾性、波动的集聚性等特征,传统的方法难以准确的度量其风险。文中运用一种新的估计VaR和ES的方法,即采取两阶段法。首先用GARCH-M类模型(GARCH-M、EGARCH-M和TGARCH-M)拟和原始收益率数据,得到残差序列;第二步用极值分析的方法分析的尾部,最后得到收益率序列的动态VaR和ES。最后对三个模型的计算结果进行比较。     

轮胎温度场有限元分析系统的设计

文章针对轮胎在行驶过程中各部位胶料受热情况不一致这一特点,深入地研究了轮胎滚动过程中的稳态热平衡状态。并通过经验数据的积累,从轮胎结构的参数化设计、断面网格划分与有限元分析、温度场计算及结果输出5个角度,设计出轮胎温度场有限元分析系统,证明了输出的温度场云图与现实中稳态轮胎温度场的温度分布情况一致。     

电子商务环境下的冷链物流研究

当今信息时代，人们将先进的信息和网络技术应用到物流管理中，极大地促进物流事业的发展，第三方物流事业也应运而生且发展前景广阔。它的优势就在于降低了生产成本。提高了经营效率，加强了竞争力，提升了企业彤象。作为现代物流的一个组成部分，冷链物流也伴随着社会的进步．技术的更新和管理思想的发展而不断地发展。在电子商务环境下如何实施冷链物流是冷链行业面临的重要课题。本文通过对一个成功的第三方冷链物流案例的分析，结合我国国情，提出相应实施策略。     

浅谈铁路桥墩的大体积混凝土施工的温控技术

在大型桥梁施工中,大体积混凝土容易产生裂缝,将对工程质量产生重大安全隐患。论文全面总结了太阳冲大桥大体积混凝土施工中的温控计算、冷却水管布置和温度监控措施,对类似工程施工有一定的参考作用。     

基于MATLAB提高Pt100测温系统响应速度的研究

通过对外加保护铜套的Pt100测温系统的实验研究,利用MATLAB建立了该系统对温度输入响应的数学模型,并通过合理增设串联相位超前校正网络提高了Pt100测温系统的响应速度。对于不同组成的Pt100测温系统,可选择不同的串联相位超前校正装置参数实现响应速度的提高。