Copper-cobalt-nickel oxide nanowire arrays on copper foams as self-standing anode materials for lithium ion batteries

Numerous scientists are in the pursuit of energy storage materials with high energy and high power density by assembly of electrochemically active materials into conductive scaffolds, owing to the emerging need for next-generation energy storage devices. In this architectures, the active materials bonded to the conductive scaffold can provide a robust and free-standing structure, which is crucial to the fabrication of materials with high gravimetric capacity. Thus, hierarchical copper-cobalt-nickel ternary oxide (CuCoNi-oxide) nanowire arrays grown from copper foam were successfully fabricated as free-standing anode materials for lithium ion batteries (LIBs). CuCoNi-oxide nanowire arrays could provide more active sites owing to the hyperbranched structure, leading to a better specific capacity of 1191 mAh/g, cycle performance of 73% retention in comparison to CuO nanowire structure, which exhibited a specific capacity of 1029 mAh/g and capacity retention of 43%, respectively.     

车辆高海拔环境起步性能试验研究

对于全域机动车辆而言,高海拔环境起步性能是评价其高原环境适应性和机动性的重要指标。针对多个型号车辆存在的高海拔环境起步困难问题,在系统开展车辆起步过程动力学分析的基础上,从车辆本身所具有的动力和所受外界阻力两个方面对高海拔环境车辆起步性能影响因素进行了深入分析,通过对某军用履带车辆高海拔起步性能的实车试验验证,确定了发动机低速扭矩特性、传动油温、行驶坡度、使用工况是高海拔环境影响车辆起步性能的关键因素,为车辆论证、研制、试验和使用工作的改进和发展提供了依据。     

Efficiency assessment of primary care providers: A conditional nonparametric approach

This paper uses a fully nonparametric approach to estimate efficiency measures for primary care units incorporating the effect of (exogenous) environmental factors. This methodology allows us to account for different types of variables (continuous and discrete) describing the main characteristics of patients served by those providers. In addition, we use an extension of this nonparametric approach to deal with the presence of undesirable outputs in data, represented by the rates of hospitalization for ambulatory care sensitive condition (ACSC). The empirical results show that all the exogenous variables considered have a significant and negative effect on efficiency estimates.     

1‐Factor and Cycle Covers of Cubic Graphs

Let G be a bridgeless cubic graph. Consider a list of k 1‐factors of G. Let be the set of edges contained in precisely i members of the k 1‐factors. Let be the smallest over all lists of k 1‐factors of G. Any list of three 1‐factors induces a core of a cubic graph. We use results on the structure of cores to prove sufficient conditions for Berge‐covers and for the existence of three 1‐factors with empty intersection. Furthermore, if , then is an upper bound for the girth of G. We also prove some new upper bounds for the length of shortest cycle covers of bridgeless cubic graphs. Cubic graphs with have a 4‐cycle cover of length and a 5‐cycle double cover. These graphs also satisfy two conjectures of Zhang 18 . We also give a negative answer to a problem stated in 18 .     

Nonvertex‐Balanced Factors in Random Graphs

We prove part of a conjecture by Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28.) regarding threshold functions for the existence of an H‐factor in a random graph . We prove that the conjectured threshold function is correct for any graph H which is not covered by its densest subgraphs. We also demonstrate that the main result of Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28) generalizes to multigraphs, digraphs, and a multipartite model.     

Synthesis and properties of LiMIIPO4 (MII = Mg,Mn0.5Mg0.5, Co0.5Mg0.5) affected by isodivalent doping and Li-sources

NH₄M^IIPO₄·H₂O (M^II = Mg, Mn_0.5Mg_0.5, Co_0.5Mg_0.5) were synthesized by direct-precipitating method. The olivine-like LiM^IIPO₄ were successfully generated through the solid state reaction between the synthesized NH₄M^IIPO₄·H₂O precursors and two different Li-sources (Li₂CO₃ or LiOH·H₂O). The NH₄M^IIPO₄·H₂O and LiM^IIPO₄ compounds were confirmed by TG/DTG/DTA, AAS/AES, FTIR and XRD methods. The structural and morphological properties of LiM^IIPO₄ compounds were studied by XRD and SEM, respectively. The XRD reflection shifts of olivine-like LiM^IIPO₄ from the Li-source of Li₂CO₃ revealed changing toward higher diffraction angles than that of LiM^IIPO₄ from the Li-source of LiOH·H₂O. The XRD shifts of LiM_0.5Mg_0.5PO₄ (M = Mn or Co) compounds confirmed the formation of the single phase of isodivalent doping of Mn²⁺ and Co²⁺ ions according to the change in the lattice parameters and cell volumes. The morphological investigations of the LiM^IIPO₄ obtained from Li₂CO₃ system illustrated the grain-like shape particles having smaller size of about 150–400 nm on account of the sequential transformations of types: deammoniation, dehydration, polycondensation and decarbonization. Conversely, the larger size particles (300–700 nm) of the LiM^IIPO₄ obtained from LiOH·H₂O were observed due to the shorter transformation path through the reactions of types: deammoniation and dehydration without polycondensation and decarbonization.     

Improvement of permanent memory effect in PDLC films using TX-100 as an additive

A number of polymer dispersed liquid crystal (PDLC) films based on dimethacrylate monomers were synthesised by polymer-induced phase separation (PIPS) using polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (TX-100) as an additive up to total solution weight of 10% aiming to modify the initial anchorage force of the liquid crystal (LC) molecules to the polymeric matrix. The effects of the addition of this additive to the PDLC films were studied resorting to electro-optical studies. Using a fitting model, several parameters were correlated such as the permanent memory effect (PME), the voltage required to achieve 90% of maximum transmittance (E90), the average elastic constant (K) and the rotational viscosity of the director (γ). The use of TX-100 results on an increase on the PME and γ, and decrease on the E90 and K.     

基于解释结构模型的大学生就业影响因素分析

针对大学生就业率低的问题,构建大学生就业评价指标体系,利用解释结构模型的实用化方法对大学生就业影响因素进行了分析,并构建大学生就业影响因素的解释结构模型.根据解释结构模型层次化处理结果,分析各个因素之间的联系,将大学生就业影响因素分为四个层次,明确大学生就业影响因素的层次结构关系,找出导致大学生就业率低的最直接因素和最根本因素.     

北京市固体废弃物产生的需求驱动因素研究——基于投入产出模型

基于引入废弃物产生的投入产出模型,从最终需求视角对2007、2010和2012年北京市典型固体废弃物产生的驱动因素进行实证分析.结果表明:秸秆产生的驱动因素由市内消费转变为调出,调出驱动产生的秸秆由2007年的20%增加到2012年的70%;一般工业固体废弃物产生的驱动因素主要是调出,产生的废弃物由2007年的36%增加到2012年的81%;建筑垃圾产生的驱动因素主要是投资,产生的建筑垃圾居高不下,2007年和2012年均达总量的91%;生活垃圾产生的驱动因素主要是调出和消费,其中调出驱动产生的生活垃圾由2007年的38%增加到2012年的49%,市内消费驱动产生的生活垃圾稳定在30%左右.     

Research on the defect structure and g factors for the tetragonal (CrO4)3− impurity center in ZrSiO4: Cr5+ crystal

ABSTRACT

The EPR g factors g// and g⊥ for the tetragonal (CrO₄)^3? impurity center in ZrSiO4: Cr⁵⁺ crystal are studied from the high-order perturbation formulas based on the two-mechanism (the crystal field and charge-transfer mechanisms) model. The studies indicate that differing from the tetragonally-elongated host (SiO4)^4- tetrahedron, the dominant defect structure of the substitutional (CrO₄)^3? tetrahedron is tetragonally- compressed with the ground state |d_z² due to the Jahn-Teller distortion. Furthermore, the agreement of g factors between calculation and experiment requires a small admixture of the first excited state |d_x²_?y² to the ground state |d_z² due to the vibrational motion of ligands, which leads a compressed (CrO₄)^3? tetrahedron to become a twinkling elongated one, These results are discussed.