The M4 Competition: 100,000 time series and 61 forecasting methods

The M4 Competition follows on from the three previous M competitions, the purpose of which was to learn from empirical evidence both how to improve the forecasting accuracy and how such learning could be used to advance the theory and practice of forecasting. The aim of M4 was to replicate and extend the three previous competitions by: (a) significantly increasing the number of series, (b) expanding the number of forecasting methods, and (c) including prediction intervals in the evaluation process as well as point forecasts. This paper covers all aspects of M4 in detail, including its organization and running, the presentation of its results, the top-performing methods overall and by categories, its major findings and their implications, and the computational requirements of the various methods. Finally, it summarizes its main conclusions and states the expectation that its series will become a testing ground for the evaluation of new methods and the improvement of the practice of forecasting, while also suggesting some ways forward for the field.     

国际化经验、东道国环境与企业海外投资区位选择

基于中国上市公司1891项投资项目数据,本文研究了国际化经验、东道国环境与企业海外投资区位选择三者之间的关系,研究发现:在企业海外投资区位选择决策中,国际化经验与东道国环境条件之间是互补和替代关系,国际化经验实际上是淡化了区位决策中东道国禀赋因素的正向效应,同时淡化了东道国成本因素的负向效应,弱化了所有东道国条件在区位决策中的价值,使跨国企业可以更多的根据内部资源来进行决策,这使得一些原先不具有吸引力的东道国也可能成为投资的目的地,这一发现有别于前人的认知。     

A healthcare facility location problem for a multi-disease,multi-service environment under risk aversion

This paper presents a stochastic optimisation model for locating walk-in clinics for mobile populations in a network. The walk-in clinics ensure a continuum of care for the mobile population across the network by offering a perpetuation of services along the transportation lines, and also establishing referral systems to local healthcare facilities. The continuum of care requirements for different diseases is modelled using coverage definitions that are designed specifically to reflect the adherence protocols for services for different diseases. The risk of not providing the required care under different realisations of health service demand is considered. In this paper, for a multi-disease, multi-service environment, we propose a model to determine the location of roadside walk-in clinics and their assigned services. The objective is to maximise the total expected weighted coverage of the network subject to a Conditional-Value-at-Risk (CVaR) measure. This paper presents developed coverage definitions, the optimisation model and the computational study carried out on a real-life case in Africa.     

A hierarchical location model for determining capacities of neonatal intensive care units in Korea

Reforming the healthcare delivery system to provide optimum care to sick newborn infants is a critical task in Korea. Motivated by the efforts of the Korean government, we study a capacity allocation model to design an optimal capacity allocation plan for neonatal intensive care units (NICUs). Our model considers the following properties: 1) the hierarchical feature of neonatal care services and 2) the congestion effect in NICU operations. We develop a mathematical model that combines a hierarchical location model with queuing theory. We subsequently apply the proposed model to the problem of allocating capacities to NICUs in Korea. We provide information that can help policymakers draw an initial plan by evaluating various capacity allocation scenarios. We further examine two policy alternatives for improving accessibility to neonatal care. One involves increasing service capacity by adaptively adding resources to NICUs, and the other includes expanding physical service coverage by introducing helicopter transport. The results show that each alternative can contribute toward improving accessibility, and we believe that these findings will have practical implications for developing a better neonatal care system.     

一种提高二次雷达测距精度的方法

测距精度决定了二次雷达系统的目标分辨能力。针对现有二次雷达测距算法测距精度低的问题，分析了二次雷达的测距原理和引入的误差，提出了改进的自适应测距方法。在不更改二次雷达信号格式和硬件设计的前提下，采用分布式处理方式，使询问机和应答机能自动周期性测试本机内部延时，并在询问应答过程中自动分别扣除本设备的内部延时，从而提高二次雷达系统的测距精度。     

Natural resources,economic growth and geography

Worldwide materials extraction increased by a factor of 8.4 over the course of the 20th century. In the meantime, global GDP and population increased by factors of about 22 and 4, respectively. This reveals that one of the key factors driving the increase in the exploitation of the resources was the growth in world population, although mitigated by the reduction in the intensity in the use of the resources in production. In this paper, we present a model that combines the theory of endogenous growth and the economy of natural resources, but taking into account the geographical distribution of economic activity. Indeed, the New Economic Geography provides insights about two elements that, although speeding up GDP growth, can curb the pressure on natural resources, namely the reduction in transports costs and a boost to pace of innovation.     

一种Farrow结构数字延时滤波器的设计

普通数字延时滤波器虽然结构简单，但系数计算过程复杂，在延时参数快速变化时，系数更新速度无法满足实时性要求，在工程应用上受限制。采用Farrow结构数字延时滤波器能够更加灵活高效地进行分数延时滤波，延时参数改变时，无需重新计算滤波器系数，更容易在现场可编程门阵列(FPGA)上实现。介绍了一种Farrow结构数字延时滤波器，提出采用基于对称结构的滤波器系数求解方法，并经过加权优化，获得最终Farrow滤波器的系数。系数计算过程中，通过对设计所得Farrow滤波器延时精度和误差的分析，调整加权因子的取值和滤波器阶数，进而提高延时精度。计算机仿真结果证明了加权对称系数求解Farrow滤波器系数方法的有效性和实用性。     

独立董事网络位置、税收规避与企业价值

独立董事的治理效果影响着上市公司的治理状况,本文从独立董事网络的声誉机制和信息传递机制出发,选取2008?2017年沪深A股上市公司作为研究样本,实证检验独立董事网络位置与企业税收规避的关系。研究发现:独立董事网络位置对企业税收规避有负向影响;与所处地区市场化程度较高的公司相比,所处地区市场化程度较低的上市公司独立董事网络中心度对公司税收规避程度的影响更强;管理层权力削弱了独立董事网络中心度对企业税收规避程度的抑制作用。进一步引入企业价值后发现,独立董事网络中心度可以抑制税收规避对企业价值的减损。本文的研究结果完善了税收规避行为价值的研究体系,也为研究独立董事是否有效发挥治理作用提供了新思路。     

重庆市雷电灾害区划

［目的］进行雷电灾害区划，对加强雷电灾害管理、确保打赢防范化解重大风险攻坚战有重要意义。［方法］综合利用闪电定位仪数据、灾情资料、地理信息资料、社会经济数据，运用层次分析法构建指标体系，计算雷电灾害风险指数，进行重庆市雷电灾害风险等级划分。［结果］（1）重庆市雷电活动具有明显的空间分布特征，地闪密度大的区域主要集中在大娄山以北，大巴山以南，密度在2次/（km2·年）以上，局部密度大于4次/（km2·年）； （2）地闪强度大的区域主要位于重庆西部、中部以及西南部的綦江、南川等地。（3）极高风险区面积132万km2，占总面积的16%、高风险区面积478万km2，占总面积的58%、一般风险区面积214万km2，占总面积的26%； （4）大娄山以北，大巴山以南的地区以高风险和极高风险等级为主，其中主城、荣昌、永川、綦江、涪陵、垫江、梁平、万州等地大部地区风险等级达极高，大娄山区及渝东南地区以高风险等级为主，渝东北的城口、巫山、巫溪等县大部地区以一般风险等级为主。［结论］通过科学地划分雷电灾害风险等级，能为重庆市的雷电监测预警及风险管理提供理论支持。