Does economic policy uncertainty affect cryptocurrency markets? Evidence from Twitter-based uncertainty measures

Using daily data from August 9, 2015, to July 7, 2020, this study examines the effects of economic policy uncertainty (EPU) on the returns of four cryptocurrencies: Bitcoin, Ethereum, Litecoin, and Ripple. To this end, two new measures of EPU (Twitter-based economic uncertainty and Twitter-based market uncertainty) are considered. A Granger causality test using the recursive evolving window approach shows a significant causality between the Twitter-based EPU measures and the BTC/USD exchange rate from October 2016 to July 2017. Moreover, a significant causality was noted from the EPU measures to the ETH/USD exchange rate from June 2019 to February 2020 and from the EPU measures to the XRP/USD exchange rate from January 2020 to February 2020. The Twitter-based EPU measures primarily positively affect the returns of the related cryptocurrencies during these periods. These results are robust to different measures of Twitter-based EPU and different econometric techniques. Potential implications, including the COVID-19 era, are also discussed.     

Evaluation of the green technology innovation efficiency of China's manufacturing industries: DEA window analysis with ideal window width

Data Envelopment Analysis (DEA) window analysis with ideal window width is applied to evaluate the green technology innovation efficiency of 28 manufacturing industries in China during 2006–2014. The obtained results are compared with those calculated using the traditional DEA model, and convergence analysis of the efficiency is conducted. Five years is the obtained ideal window width and DEA window analysis with ideal window produces results closer to reality for China's manufacturing industry. The overall efficiency of the green technology innovation in the manufacturing sector is low following a wave-shaped curve – first decreasing, then increasing and decreasing again, with large inter-industrial differences. There are 8 high-, 14 medium- and 6 low-efficiency industries. A convergence trend in the green technology innovation efficiency within the 28 manufacturing industries exists, implying a catch-up effect between them.     

一种带辅助译码比特的Polar码译码方法

在传统的Polar码译码的基础上，引入辅助译码比特，构造了一个辅助的Polar码字以提高译码性能。辅助比特由信道选择辅助窗口内的信息位决定。接收端如译码失败，将进行二次译码尝试。译码方案分两阶段进行：基于相同结构的扩展生成矩阵，将辅助译码比特译出；结合译出的辅助比特，对原码字进行译码，提高译码成功率。仿真结果显示，使用所提方法进行译码，其译码性能明显优于普通串行抵消译码方法；与两种传统的自动重传请求方案相比，能分别获得1 dB和1.9 dB的性能增益。     

基于GIS和CFD的城市街道通风廊道研究——以武汉为例

改善通风的城市形态因素可以分为建筑和道路2个方面。建筑形态的通风评价主要采取综合迎风面积密度方法,将城市建筑环境转化为具有数值属性的栅格,从而提取城市建成区的通风廊道,但是该方法忽略了城市重要的通风路径——城市街道。以街道的朝向为主要评价对象,挖掘线状要素城市道路的通风廊道,作为建筑形态通风廊道划分方法的补充。根据通风潜力随夹角的变化规律,利用地理信息系统(GIS)的空间分析技术进行街道的通风潜力评价,在综合迎风面积密度密集的区域,存在通风潜力较高的城市街道     

基于双层规划模型的冷链物流网络多目标优化

针对冷链物流时效性强这一特性,应用软时间窗反映客户满意度,并结合T.T.T理论换算货损成本。在考虑满足客户时间窗的条件下,寻找配送中心建设及操作成本、车辆成本、惩罚成本及货损成本所构成的总成本最小时的最优配送方案,建立冷链物流配送选址及路径优化的双层规划模型,并将改进的遗传算法运用到该模型中,借助Matlab软件对具体实例进行求解,得到最优结果,为冷链物流网络多目标优化问题提供理论依据。     

Does international capital flow lead to a housing boom? A time-varying evidence from China

This paper examines the causal relationship between the housing prices (HP) and the international capital flows (ICF) in China. With structural changes existing, we find that long-run relationship using full-sample data is unstable, suggesting that traditional Granger causality test is not reliable. However, we further find an unstable short-run relationship between ICF and HP when assessing the stability of the parameters and there are bidirectional causal relationships between ICF and HP for several sub-periods. Additionally, our findings indicate both positive and negative bidirectional causal relations between the series. Based on the arbitrage of ICF, the results suggest that the rise of Chinese HP is the underlying force for the inflows of international capital. Meanwhile, a surge in capital inflows may be accompanied by a rise in the price of housing. This confirms the theoretical analysis that there is an interconnected transmission mechanism between the ICF and the HP, which is diverse and depends both on the flow of ICF and on other factors.     

长距离隧道的通风选型问题浅析

笔者以新建兰渝铁路六标段花石隧道为例,对该隧道的应有的通风设计,结合现有通风方式的弊端和改进,进行浅要的比较分析,在此基础上对同类型隧道的通风选型进行总结。     

单车场无时间窗甩挂运输车辆调度的启发式算法

考虑了牵引车空驶、带空挂车行驶和带重挂车行驶所引起的成本差异，定义了牵引车运行成本的概念，将总运行成本最小作为调度方案优劣的判别指标，并同时考虑牵引车数量最少。将牵引任务分为四种类型，定义了任务链、虚拟任务、链内交叉和链间交叉的概念，提出了一种求解该类单车场甩挂运输车辆调度无时间窗约束的启发式算法，包括初始调运方案、链内优化、空车调运交叉、牵引车数量优化和链间交叉。最后给出了仿真算例，算法优化后的最终方案与初始方案相比，牵引车数量减少，总运行成本降低，验证了算法的有效性和可行性。     

The trade-off between fixed vehicle costs and time-dependent arrival penalties in a routing problem

This paper introduces the vehicle routing problem with soft time windows (VRPSTW) in which problem definition differs from ones previously defined in literature. Branch-and-price approach is employed, resulting in a set partitioning master problem and its new subproblem. Novel techniques are consequently developed to solve this new subproblem. Experimental results report the comparisons of these solution techniques under the branch-and-price framework. The VRPSTW solutions have further been compared to the state-of-the-art literature, signifying the superiority of the VRPSTW on this issue.     

武汉老橱窗特征解析

武汉老橱窗是当时社会生活的缩影：老橱窗是经济大潮起落的风向标,是政治风云变幻的晴雨表,是都市生活的流行时尚眼,是商店卖场的无声宣传员,是艺术空间的多彩百花园。