On the limitations of comparing mean square forecast errors

Linear models are invariant under non-singular, scale-preserving linear transformations, whereas mean square forecast errors (MSFEs) are not. Different rankings may result across models or methods from choosing alternative yet isomorphic representations of a process. One approach can dominate others for comparisons in levels, yet lose to another for differences, to a second for cointegrating vectors and to a third for combinations of variables. The potential for switches in ranking is related to criticisms of the inadequacy of MSFE against encompassing criteria, which are invariant under linear transforms and entail MSFE dominance. An invariant evaluation criterion which avoids misleading outcomes is examined in a Monte Carlo study of forecasting methods.     

Clustering the rows and columns of a contingency table

A number of ways of investigating heterogeneity in a two-way contingency table are reviewed. In particular, we consider chi-square decompositions of the Pearson chi-square statistic with respect to the nodes of a hierarchical clustering of the rows and/or the columns of the table. A cut-off point which indicates significant clustering may be defined on the binary trees associated with the respective row and column cluster analyses. This approach provides a simple graphical procedure which is useful in interpreting a significant chi-square statistic of a contingency table.The author gratefully acknowledges the constructive comments of the referees and the editor.     

Microstructure and functional morphology of the Early Cambrian problematical fossil Rhombocorniculum

Rhombocorniculum cancellatum from the Lower Cambrian of southern Shaanxi Province (South China) is represented by the dextral and sinistral tooth-like sclerites (both in nearly equal numbers), indicating that the body plan of the organism with these sclerites probably was bilaterian. The main feature of the microstructure of the sclerites is the presence of longitudinally arranged, mutually contiguous hollow tubules, the shared walls consisting of microcrystalline apatite. In transverse cross sections, the sclerite wall mainly exhibits a spongy structure, with pore size decreasing adapically. Functional morphological analysis indicates that the sclerites serve as a defensive rather than a grasping function.     

细菌与细菌之间的信息交流--革兰氏阴性细菌的Quorum-Sensing系统

人们长期以来一直认为细菌是以单个细胞的方式生存于自然界的.但是,自从10年前研究人员发现细菌与细菌之间存在着相互间的信息交流后,人们改变了对细菌的生存方式和其生理习性的认识.细菌其实是具有协同作战能力的多细胞习性微生物,而这种能力的形成需要依赖细胞与细胞之间的信息交流.细菌之间的信息交流涉及到细菌的多种生理功能、细菌致病能力以及细菌对抗菌素的耐药等方面.因此,了解和研究细菌的这一机制,阻断其信息交流,也许能达到削减细菌毒力的目的.文中将借助国外的最新报道,结合作者的研究成果,介绍细菌与细菌之间信息系统的由来,该系统的调节机制,研究该系统的手段、意义以及前景展望等.     

Equilibrium Copper Strip Points as a Function of Temperature and Other Operating Parameters： Implications for Commercial Copper Solvent Extraction Plants

Introduction Copper solvent extraction (SX) is a well known proc-ess for copper recovery from a wide variety of leach solutions. Until recently, typical leach solutions con-tained 0.5 to 8 g/L Cu at 15 to 25℃ . In the past 5 years there has been signific…     

Early Cambrian protoconodonts and conodont-like fossils from China: Taxonomic revisions and stratigraphic implications

Tooth likephosphaticprotoconodontsand“con odont likefossils”arecharacteristiccomponentsoftheEarlyCambriansmallshellyfossils (SSF )withaworldwidedistribution .Theyarerepresentedexclu sivelybyisolatedscleritesandareoften presentinaceticacid etchedresiduesfromLowerCambriancar bonates .SincethefirstreportofProtohertzinaMis sarzhevsky 1973fromthebasalCambrianoftheYangtzePlatformin 1977[1] ,andalongwithenthusi asticresearchactivitiesonthesmallshellyfossilsandcandidatesectionsforaglobalPrecamb…     

基于多源浮动车数据融合的道路交通运行评估

针对当前出租车浮动车数据覆盖范围和数据质量不足的问题,在现有数据特征分析的基础上引入百度手机导航和公交车浮动车导航数据,面向道路运行评估和拥堵管理提出了基于出行时间的交通运行指数算法和一种基于出租车、百度、公交车多源浮动车数据融合的道路交通运行评估方法,构建了多源数据融合规则和融合算法.以深圳为例进行了融合效果分析,结果表明所提出的多源数据融合方法效果显著,很大程度上提高了融合结果精度、数据覆盖率、数据可靠性和数据样本量,最后提出了主要应用方向和初步应用效果,能够为国内外城市开展交通运行评估工作提供借鉴.     

Some Open Problems in Parameterized Complexity Related to the Work of Jianer Chen

This short paper highlights some open problems related to the work of Jianer Chen in the area of parameterized/multivariate algorithmics.