Fast and accurate yearly time series forecasting with forecast combinations

It has long been known that combination forecasting strategies produce superior out-of-sample forecasting performances. In the M4 forecasting competition, a very simple forecast combination strategy achieved third place on yearly time series. An analysis of the ensemble model and its component models suggests that the competitive accuracy comes from avoiding poor forecasts, rather than from beating the best individual models. Moreover, the simple ensemble model can be fitted very quickly, can easily scale horizontally with additional CPU cores or a cluster of computers, and can be implemented by users very quickly and easily. This approach might be of particular interest to users who need accurate yearly forecasts without being able to spend significant time, resources, or expertise on tuning models. Users of the R statistical programming language can access this modeling approach using the “forecastHybrid” package.     

Implementing product platforms in the global enterprise: Lessons from an LED industry leader

Product platforming—using technology subsystems or components that are shared within and across product lines—is a proven way to increase the effectiveness of innovation processes in established companies and startups alike. Yet, embracing the product platforming strategy turns out to be difficult in practice, particularly within the context of global, diversified companies. In this article, we examine the strategies and challenges of implementing product platforms across multiple business segments and multiple geographies. Using the experience of global LED industry leader Signify, we explore the challenges of global platforming and the technological, organizational, management process transformations needed for success. We also examine how platforming strategies change as manufacturers enter the world of connected things.     

草原荒漠区红砂和珍珠猪毛菜群落分布特征分析

为探究影响红砂和珍珠猪毛菜群落空间分布的主要环境因子,采用点格局分析方法和冗余分析(RDA),分析了植物种的空间分布格局及其与环境因子之间的关系。研究结果显示：多年平均降水量的减少地点,红砂种群、珍珠猪毛菜种群的空间聚集程度减弱,向随机分布趋势转化,表现出种内促进关系逐渐减弱的适应策略;种间关联性也表现出随降水的减少物种之间的促进关系逐渐减弱。消除生境异质性后,红砂种群、珍珠猪毛菜种群均在>30 m尺度下随机分布,种群内部表现为相互独立;空间关联性整体均呈现为负相关,种间关系表现为相互竞争,降水减少的地点存在向无相关性转变的趋势。利用冗余分析识别出导致群落植被特征产生差异的主要因素是气候、土壤、海拔,因此在制定更为有效的荒漠灌木多样性保育措施时不仅要考虑植被本身的特性,也要加强对荒漠土壤环境的保护。     

养猪废水处理系统微生物群落结构变化及影响因素研究

利用Illumina高通量测序技术对某养猪场不同处理单元细菌和真菌群落变化特征进行分析,并采用冗余性分析方法考察其受水质参数的影响。结果表明:活性污泥各阶段主要细菌类群为变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria);生物处理后,变形菌门(Proteobacteria)的相对丰度降低近15%,厚壁菌门(Firmicutes)的相对丰度从进水到出水降低了近6%,同时放线菌门(Actinobacteria)的相对丰度增加近7%;主要真菌类群为子囊菌门(Ascomycoka)、担子菌门(Basidiomycota)和少量壶菌门(Chytridiomycota)。值得注意的是处理后出水中仍含有丰度较高的曲霉菌属(Aspergillus)、毛孢子菌属(Trichosporon)、念珠菌属(Cladosporium)等真菌致病菌,对后续环境和公共健康造成潜在威胁。养猪废水处理系统众多细菌和真菌群落的变化受水质参数(主要是COD和氮)的影响明显。     

丹江口库湾浮游植物群落与环境因子关系研究

为掌握丹江口库湾富营养化状况,确保南水北调中线水源安全,于2017年分季节对丹江口库湾浮游植物群落结构和14项水文水环境因子进行了4次监测,并运用相关分析、冗余分析(RDA)等多元统计方法定量分析了浮游植物群落结构与环境因子的关系。监测发现,丹江口水库共鉴定出浮游植物7门57属,年均藻类密度4.89×10~6 cells/L,变幅2.73×10~6～6.87×10~6 cells/L。丹江口水库群落组成以硅藻、蓝藻和绿藻为主;结构变化规律为由春季的硅藻、蓝藻向夏季的绿藻、蓝藻和隐藻,以及秋、冬季的硅藻、隐藻和蓝藻转变。蓝藻门的束丝藻和隐藻门的隐藻为库湾四季的优势种。通过Shannon-Wiener指数、Margalef指数和Pielou指数分析认为,夏季藻类多样性高,绿藻优势度高,冬季藻类多样性相对较低,种群数量差异不显著。根据综合营养状态指数评价的结果可知,库湾富营养化程度处于中营养和富营养化水平,其中总氮贡献较大,总氮浓度范围在1.08～1.88 mg/L之间,均值为1.47 mg/L,磷为库湾富营养化的限制因子。RDA分析结果表明,除氮、磷营养盐外,温度、二氧化硅和电导率等也是影响库湾浮游植物群落分布的重要环境因子。     

涡河中下游浮游植物时空分布及成因

为探明涡河中下游水质状况,基于2016年12月至2017年9月涡河中下游4次监测的浮游植物和水质数据,利用物种优势度和多样性指数对浮游植物的时空分布特征进行定量分析。结果表明:涡河中下游的浮游植物主要表现出种类分布不均匀、不同河段差异性大等特点;涡河中下游共发现浮游植物7门89属种,以绿藻门和硅藻门为主;浮游植物的优势类群随季节变化较大,4次采样共发现16个优势物种,4个季节中绿藻门的优势种类均为最多;浮游植物Shannon-Wiener多样性指数水质评价等级显示涡河中下游整体污染程度呈转好趋势;冗余度分析表明环境因子对浮游植物时空分布总体变异的解释度为60.02%;温度、电导率和总磷是影响涡河中下游浮游植物时空分布的主要环境因子。     

Extending multi-tenant architectures: a database model for a multi-target support in SaaS applications

Multi-tenant architectures (MTAs) are considered a cornerstone in the success of Software as a Service as a new application distribution formula. Multi-tenancy allows multiple customers (i.e. tenants) to be consolidated into the same operational system. This way, tenants run and share the same application instance as well as costs, which are significantly reduced. Functional needs vary from one tenant to another; either companies from different sectors run different types of applications or, although deploying the same functionality, they do differ in the extent of their complexity. In any case, MTA leaves one major concern regarding the companies’ data, their privacy and security, which requires special attention to the data layer. In this article, we propose an extended data model that enhances traditional MTAs in respect of this concern. This extension – called multi-target – allows MT applications to host, manage and serve multiple functionalities within the same multi-tenant (MT) environment. The practical deployment of this approach will allow SaaS vendors to target multiple markets or address different levels of functional complexity and yet commercialise just one single MT application. The applicability of the approach is demonstrated via a case study of a real multi-tenancy multi-target (MT²) implementation, called Globalgest.     

UNIFY数据服务器（ELS）2000年挑战解决方案

本文从各个方面讨论了ＵＮＩＦＹ关系数据库２０００年问题,比较和分析了２０００年解决方案的利弊,为ＵＮＩＦＹ用户和工程人员提供了一种较好的解决方案。     

基于软件无线电的中频数字化直扩系统的设计与实现

本文根据直接序列扩频原理,给出了一种基于软件无线电思想的中频数字化直扩系统的设计方案,并采用可编程数字器件实现。实验结果表明该方法达到了设计要求,并具有良好的通用性和灵活性。     

国际软件外包发包商绩效的实证研究

软件外包在过去二十年的发展引起了国内外学者的广泛关注。本文用定量研究的方法,对国际软件外包中接包商外包绩效的影响因素做实证研究。研究结果表明,在软件外包中,交流成本与接包商的外包绩效负相关,而接包商的规模、声誉、价格优势以及专业能力都与接包商的外包绩效正相关。研究的结果有助于我们认识中国和印度软件外包发展的差距,同时从理论和管理实践上为中国的软件外包发展提出建设性意见。