Geoadditive expectile regression

Quantile regression has emerged as one of the standard tools for regression analysis that enables a proper assessment of the complete conditional distribution of responses even in the presence of heteroscedastic errors. Quantile regression estimates are obtained by minimising an asymmetrically weighted sum of absolute deviations from the regression line, a decision theoretic formulation of the estimation problem that avoids a full specification of the error term distribution. Recent advances in mean regression have concentrated on making the regression structure more flexible by including nonlinear effects of continuous covariates, random effects or spatial effects. These extensions often rely on penalised least squares or penalised likelihood estimation with quadratic penalties and may therefore be difficult to combine with the linear programming approaches often considered in quantile regression. As a consequence, geoadditive expectile regression based on minimising an asymmetrically weighted sum of squared residuals is introduced. Different estimation procedures are presented including least asymmetrically weighted squares, boosting and restricted expectile regression. The properties of these procedures are investigated in a simulation study and an analysis on rental fees in Munich is provided where the geoadditive specification allows for an analysis of nonlinear effects of the size of flats or the year of construction and the spatial distribution of rents simultaneously.     

ERPN32-200离心泵机械密封失效原因分析

通过对ERPN32-200离心泵机械密封失效原因的分析,发现机械密封的实际密封效果不仅与机械密封自身的性能有关,而且与相关零部件的加工尺寸的精度等级以及维修时的装配质量有着重要的关系,同时针对不同的问题提出了相应的措施,延长了机械密封的使用寿命。     

基于物联网与3G整合的电子商务应用资金流探析

文章在简要介绍物联网与3G网络的基础上,阐述了物联网与3G整合背景下电子商务资金流所具备的特点,进而论述了此背景下资金流的优化和作用,最后重点分析了整合背景下电子商务资金流的两个应用案例。     

Electro-oxidation of dimethyl ether on Pt/C and PtMe/C catalysts in sulfuric acid

The electro-oxidation of dimethyl ether (DME) on PtMe/Cs (Me = Ru, Sn, Mo, Cr, Ni, Co, and W) and Pt/C electro-catalysts were investigated in an aqueous half-cell, and compared to the methanol oxidation. The addition of a second metal enhanced the tolerance of Pt to the poisonous species during the DME oxidation reaction (DOR). The PtRu/C electro-catalyst showed the best electro-catalytic activity and the highest tolerance to the poisonous species in the low over-potential range (<0.55 V, 50 °C) among the binary electro-catalysts and the Pt/C, but at the higher potential (>ca. 0.55 V, 50 °C), the Pt/C behaved better than PtRu/C. The apparent activation energy for the DOR decreased in the order: PtRu/C (57 kJ mol⁻¹) > Pt₃Sn/C (48 kJ mol⁻¹) ≈ Pt/C (46 kJ mol⁻¹). On the other hand, the activation energy for the MOR showed a different turn, decreased in the following order: Pt/C (43 kJ mol⁻¹) > Pt₃Sn/C (35 kJ mol⁻¹) ≈ PtRu/C (34 kJ mol⁻¹). The temperature dependence of the DOR was greater than that of the oxidation of methanol (MOR) on the PtRu/C.     

Helium gas permeability of montmorillonite/epoxy nanocomposites

Helium gas permeability of silicate clay (montmorillonite) particles/epoxy nanocomposites was examined. The incorporation of increasing amounts of montmorillonite particles reduced the helium gas permeability. Based on Fick’s law, gas permeation behavior of the nanocomposite was evaluated. With the increase of montmorillonite loading, gas diffusivity decreased, while gas solubility increased. Helium diffusion behavior is in agreement to the numerical results based on the Hatta–Taya–Eshelby theory. It has been revealed that dispersion of nanoscale platelets in polymer is effective in improving gas barrier property.     

基于C8051f020的标准电源控制单元的设计及实现

介绍了基于C8051f020的程控标准电源的控制部分。该控制单元以C8051f020为核心实现了PID控制器及人机交互的设计,并给出了具体实现方法,同时在实际电路的调试中收到了良好的效果。     

基于ARM的广播发射机微控制器硬件系统设计

应用Samsung公司的S3C44B0X嵌入式芯片构建硬件平台,设计广播发射机微控制器。按照其在广播发射机监测控制系统中的控制特点,介绍和论述该微控制器的硬件结构。与传统的基于8/16位单片机构建的系统相比,由于S3C44B0X芯片内置多种实用外设可大大简化电路,从而提高了系统的可靠性,增强了系统抗干扰能力。     

对20Ni9Co5Mo2Cr2V生产过程中问题的分析

分析了20Ni9Co5Mo2Cr2V钢历次冶炼的配料、真空感应熔炼及电渣重熔过程，找到了钢中C过度烧损、浇注的底垫鼓起及电渣重熔过程出现气孔的原因，为冶炼生产提出了建议。     

C/Cu(Fe)复合材料制备工艺及性能研究

利用三步电沉积法制备C／Cu（Fe）复合材料预制丝，将预制丝缠绕成毛坯，采用真空热压法制备C／Cu（Fe）复合材料．研究表明，真空热压工艺对复合材料力学性能有很大影响，通过力学性能试验和对拉伸断口形貌的分析，得出了制备C／Cu（Fe）复合材料的最佳工艺．     

G.729A+B语音编解码在新一代定点DSPs上的实现

文章介绍了ITU-TG．729A算法与ITU-TG．729B算法配合使用的语音编解码方案，并讨论了其在TI公司最新一代定点数字信号处理器(DSPs)TMS320C6416上实现的关键技术。G．729A是G.729编码器的简化版本，G．729B是带VAD(活动话音检测)的静音压缩算法。两者结合可以有效地降低码率，同时保持很好的合成语音质量。