一种动态加权的LDPC译码方法

为了加快低密度奇偶校验（LDPC）码的译码速度，有效改善LDPC码的译码性能，针对校验节点更新过程中的对数似然比（LLR）值的大小，设计了一种LDPC码的动态加权译码方法。以IEEE 802.16e标准的奇偶校验矩阵为例，根据LLR值的变化规律，利用增长因子和抑制因子对和积译码算法和最小和译码算法进行动态加权。仿真结果显示，基于动态加权的译码方法相对于传统译码方法误码率都有明显改进，译码复杂度也有所降低。     

Do Cryptocurrencies Increase the Systemic Risk of the Global Financial Market?

The advance of cryptocurrencies has sparked wide concern over their interplay with the existing global financial market. This paper analyzes the risk spillover relation between cryptocurrencies and major financial assets, and unravels how cryptocurrencies could influence global financial systemic risk. We find that cryptocurrencies function as a separate risk source from traditional assets. Major legislative, financial and technological events in the cryptocurrency market may affect risk spillover dynamics. Although the overall penetration of cryptocurrencies is not yet deep, introducing cryptocurrency can significantly increase the systemic risk to traditional markets during low risk level episodes.     

Size of nested cities

Models of cities based on conventional spatial market theory are unable to replicate a realistic size distribution. The stochastic process approach to size distribution, which assumes proportionate growth, does not provide an economic foundation for spatial trades. There is an apparent irreconcilability. We propose that since there is a continuum of equilibria in models of spatial markets with endogenous location, proportionate growth can work as equilibrium selection. We present computations for an urban configuration that has not been presented in the literature before. A small city locates inside a larger city's agricultural supply zone. This generates a larger variation in city size that may include a realistic size distribution.     

战术面向服务架构概念及相关技术

战术面向服务架构（TSOA）是实现战术云平台服务基础设施的重要支撑概念。由于战术环境的复杂性，目前对TSOA实施过程中面临问题和相关实现技术的总结还较少。为此，开展了针对TSOA的概念以及相关技术的研究。首先，从战术环境下的TSOA架构需求背景出发，介绍了TSOA架构的组成以及适应性特征；然后，通过分析战术环境下设备和网络等多方面存在的限制性因素，明确实施TSOA架构所面临的挑战以及需要解决的关键问题，并对实现过程中涉及的服务发现、消息传输机制、网络状态自适应等相关技术进行归纳；最后，对国内外的相关研究工作进行总结，期望对推动TSOA架构的具体实施提供一定参考。     

长三角港口腹地动态演变及耦合协调度研究

明确港口腹地演变趋势、分析港腹耦合协调度,对长三角地区港腹联动发展具有重要意义。量化港口系统—腹地系统综合指标评价体系,运用高斯烟羽模型在2006、2011、2016年3个时间节点上测算长三角地区主要港口影响强度,并对腹地范围进行划分,利用耦合协调模型定量分析港口系统和直接腹地经济系统耦合协调度。研究结果表明:长三角地区港口呈现"一超多强"的格局,以上海港为中心,各港口多极发展;港口腹地范围整体稳定,局部波动,上海港的边缘腹地不断缩减;港口与腹地的耦合协调度处于上升态势,宁波—舟山港腹耦合协调度最高。     

空间目标的联合矩阵束极点估计

极点作为谐振区雷达目标的最主要电磁特性，具有很大的空间目标识别前景。但是在使用频域观测数据提取目标极点时，存在虚假极点和估计精度问题。针对上述问题，首先通过加窗和截断改进了后时响应信号的获取流程，抑制了虚假极点影响；然后采用最小描述长度法（MDL）估计极点个数，避免了定阶错误引起的虚假极点；最后采用联合矩阵束法估计极点，有效减少了单角度数据估计极点时存在的遗漏极点和虚假极点问题。FEKO软件验证表明，所提算法具有更高的精度和抗噪能力。     

Size and information revelation in securities trading

We examine differences in information content between order submission sizes and trade sizes by U.S. equity traders. Increasing (decreasing) order submission (trade) size is reflective of information. The result suggests that better-informed traders want to trade in a large size, but that they engage in stealth trading practices or break larger orders into smaller sizes in order to conceal information. While prior studies tend to narrowly focus on trade executions at the market-centre level, our findings indicate that order submission size varies significantly from trade size and that both sizes are informative about future prices, albeit in an inverse manner.     

Does economic policy uncertainty raise corporate precautionary cash holdings? Evidence from China

Using China as the research setting, this paper investigates the relationship between economic policy uncertainty and corporate precautionary cash holdings. Empirical results show a U-shaped relation between economic policy uncertainty and corporate precautionary cash holdings. Empirical analysis, in terms of ownership structure, firm size, corporate competitiveness and geographical location, further shows that (i) the effects for economic policy uncertainty in both state-owned and non-state-owned enterprises are significant, but the effect is stronger for state-owned enterprises; (ii) such significant effect is also found more strongly in small and medium-sized enterprises and highly competitive enterprises; and (iii) the effects for eastern, central and western China are all statistically significant, but the effect is strongest for eastern China.     

协调发展战略下地方政府合作的动力机制探析--以深汕特别合作区为例

党的十九大报告首次提出区域协调发展战略,要求各地充分发挥比较优势,加强政府间合作,着力解决区域发展不平衡不充分的问题。深汕合作区正是实施这一战略的典型代表。其中,政府的战略政策导向、经济全球化、区域一体化和非政府组织的发展是合作区得以形成的主要外部动力;区域协调发展、产业结构调整、官员升迁诉求是内部动力。但是,在合作区发展的过程中也存在一定的阻力。如地方保护主义的抬头、利益博弈、市场运作的行政化。因此,为促进地方政府间良性合作,应不断强化合作的正向激励,降低合作的阻力,保证区域府际合作的长久性。     

Does rice farming shape audit quality: Evidence from signing auditors level analysis

This study examines whether signing auditors from rice planting regions affect audit quality. Using a sample of 12,223 firm-year observations from the Chinese stock market over the period of 2004–2015, our findings reveal that signing auditors from rice regions are significantly negatively associated with the likelihood of unclean audit opinions, suggesting that signing auditors with rice culture are more likely to succumb to the managers and hamper independence, and thus are more inclined to issue favorable audit opinions, and eventually impair audit quality. Furthermore, audit firm size and industry expertise attenuate the negative relation between signing auditors with rice culture and audit quality. In addition, above findings are robust to a variety of sensitivity tests using different measures of audit quality and signing auditors from rice cultivating areas and our conclusions still stand after using the Heckman two-step approach, placebo test and differences-in-differences method to address the potential endogeneity problem.