Physicochemical properties of lithium iron phosphate‐carbon as lithium polymer battery cathodes

Lithium iron phosphate‐carbon (LiFePO₄/multiwalled carbon nanotubes (MWCNTs)) composite cathode materials were prepared by a hydrothermal method. In this study, we used MWCNTs as conductive additive. Poly (vinylidene fluoride‐co‐hexafluoropropylene)‐based solid polymer electrolyte (SPE) was applied. The structural and morphological performance of LiFePO₄/MWCNTs cathode materials was investigated by X‐ray diffraction and scanning electron microscopy/mapping. The electrochemical properties of Li/SPE/LiFePO₄‐MWCNTs coin‐type polymer batteries were analyzed by cyclic voltammetry, ac impedance and galvanostatic charge/discharge tests. Li/SPE/LiFePO₄‐MWCNTs polymer battery with 5 wt % MWCNTs demonstrates the highest discharge capacity and stable cyclability at room temperature. It is indicated that LiFePO₄‐MWCNTs can be used as the cathode materials for lithium polymer batteries. Copyright © 2011 John Wiley & Sons, Ltd.     

When retarded nonlinear time-delay systems admit an input–output representation of neutral type

The paper shows that nonlinear retarded time-delay systems can admit an input–output representation of neutral type. This behaviour represents a strictly nonlinear phenomenon, for it cannot happen in the linear time-delay case where retarded systems always admit an input–output representation of retarded type. A necessary and sufficient condition for a nonlinear system to exhibit this behaviour is given, and a strategy for finding an input–output representation of retarded type is outlined. Some open problems that arise consequently are discussed as well. All the systems considered in this work are time-invariant and have commensurable delays.     

Solar enhanced natural draft dry cooling tower for geothermal power applications

This paper presents a new concept of hybrid cooling, named solar enhanced natural draft dry cooling tower (SENDDCT), in which solar collectors are added to traditional natural draft dry cooling towers to increase their performance. The purpose of using solar energy in this new cooling system is to increase the suction through the tower so that more air flow is achieved through the compact heat exchangers that cool condensers of a geothermal power plant. For the same size of the cooling tower, more air flow across the heat exchangers means more heat can be rejected by the system. The governing equations for the SENDDCT are similar to those of a conventional natural draft dry cooling tower except that solar heating is added after the heat exchanger bundles. Performance comparisons show that SENDDCT has substantial advantages over conventional natural draft dry cooling towers for geothermal power plants as well as standalone solar chimney power plants.     

Accurate heat capacity data at phase transitions from relaxation calorimetry

Extracting accurate heat capacities by conventional relaxation calorimetry at first-order or very sharp second-order phase transitions is extremely difficult. The so-called “scanning method” provides a key to overcome this challenge. Here, we introduce new corrections in the data analysis of this method. Critical examinations of the improvements are made experimentally by investigating the well-studied first-order ferroelectric phase transitions of KH₂PO₄ and BaTiO₃ using a commercial relaxation calorimeter Physical Property Measurement System (PPMS) supplied by Quantum Design. The results for KH₂PO₄ are shown to be excellent; a very sharp peak in heat capacity is obtained and the absolute values are shown to agree well with the previous results obtained by adiabatic calorimetry on much larger samples. The critical behavior of the heat capacity in the vicinity of the transition temperature, as well as the thermodynamic quantities such as the transition enthalpy and entropy, also agrees very well with the previous results. For BaTiO₃, clear hysteretic behavior of the transition is observed for heating and cooling curves.     

概率在组合类等式中的一些应用

组合类等式的证明或计算一般采用代数的方法。本文采用概率的方法证明或计算一些组合类等式。使过程更为直观。     

推动设备设计创新：低成本电容式触摸屏一马当先

产品差异化和新设计是设备设计工程师一直面临的挑战,必须认真地考虑和实现产品的用户界面和可操作性,创新性设计必须使用方便、耐用,而且具有成本效益,并能获得广泛的认同.电容式感应技术因为在厨房的恶劣环境下具有的耐用特性,很快成为触摸控制的首选技术,他具有易于低成本实现的特点,以及由于其可扩展性,可以提供其他技术所不能实现的用户功能.     

Search-based structured prediction

We present Searn, an algorithm for integrating search and learning to solve complex structured prediction problems such as those that occur in natural language, speech, computational biology, and vision. Searn is a meta-algorithm that transforms these complex problems into simple classification problems to which any binary classifier may be applied. Unlike current algorithms for structured learning that require decomposition of both the loss function and the feature functions over the predicted structure, Searn is able to learn prediction functions for any loss function and any class of features. Moreover, Searn comes with a strong, natural theoretical guarantee: good performance on the derived classification problems implies good performance on the structured prediction problem.