Realizing both High Energy and High Power Densities by Twisting Three Carbon‐Nanotube‐Based Hybrid Fibers

Energy storage devices, such as lithium‐ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities in supercapacitors have limited their applications. How to simultaneously realize high energy and power densities in one device remains a challenge. Herein a fiber‐shaped hybrid energy‐storage device (FESD) formed by twisting three carbon nanotube hybrid fibers demonstrates both high energy and power densities. For the FESD, the energy density (50 mWh cm^?3 or 90 Wh kg^?1) many times higher than for other forms of supercapacitors and approximately 3 times that of thin‐film batteries; the power density (1 W cm^?3 or 5970 W kg^?1) is approximately 140 times of thin‐film lithium‐ion battery. The FESD is flexible, weaveable and wearable, which offers promising advantages in the modern electronics.     

弹性介质中圆柱壳动力响应研究的现状和展望

一、引言在地震动情况下,地下结构与地面结构相比较其动力响应是十分不同的。以桥梁和水堤为例,对这类结构的设计,水平惯性力是一个极为重要的因素。可是,对于地下结构,以埋管为例,惯性荷载主要由其周围的土介质所承受。地下管道系统的地震破坏,     

The Influence of Moduli Slope of a Linearly Graded Matrix on the Bulk Moduli of Some Particle- and Fiber-Reinforced Composites

The stored energy functional of a homogeneous isotropic elastic body is invariant with respect to translation and rotation of a reference configuration. One can use Noether's Theorem to derive the conservation laws corresponding to these invariant transformations. These conservation laws provide an alternative way of formulating the system of equations governing equilibrium of a homogeneous isotropic body. The resulting system is mathematically identical to the system of equilibrium equations and constitutive relations, generally, of another material. This implies that each solution of the system of equilibrium equations gives rise to another solution, which describes the reciprocal deformation and solves the system of equilibrium equations of another material. In this paper we derive conservation laws and prove the theorem on conjugate solutions for two models of elastic homogeneous isotropic bodies – the model of a simple material and the model of a material with couple stress (Cosserat continuum). This revised version was published online in August 2006 with corrections to the Cover Date.     

Parametric response of a metallic column at elevated temperature

The parametric response of a metallic column at elevated temperature is investigated, taking into account its non-linear viscous characteristics. An asymptotic method for the determination of the region of self-excitation and the amplitudes and phase angles for both stationary and non-stationary responses is outlined briefly. This method is applied to predict the parametric response of a 2618-T61 Al alloy column at 200°C. It is shown that the region of selfexcitation shifts away from the elastic frequency axis, that the amplitude of the stationary response increases sharply as the excitation parameters move from the stability region into the selfexcitation region and that the amplitude of the non-stationary response can be approximated by the stationary response solution for slow varying excitation frequency.     

高质量高取向(100)面金刚石膜的可控性生长

应用微波等离子体化学气相沉积技术, 在低气压下对(100)晶面金刚石膜的表面形貌、质量、取向和生长率进行了可控性生长研究. 结果表明: 基片温度与甲烷浓度对(100)晶面金刚石膜的生长存在耦合规律. 为了获得表面形貌相似的(100)晶面金刚石膜, 在沉积过程中, 增加碳源浓度的同时需要同时升高基片温度; 当甲烷浓度为3.0%, 基片温度从740 ℃上升至1100 ℃ 的过程中, 金刚石膜的晶面取向变化可分为五个阶段, 其中当基片温度在860 ℃至930 ℃时, 很适合高取向(100)晶面金刚石膜生长; 另外, 金刚石膜的质量和生长速率分别与基片温度和甲烷浓度成正比. 为了获得高质量高取向(100)晶面金刚石膜, 应当选择合适的基片温度和甲烷浓度.     

Hubbard模型中的相位弦效应与交互Chern-Simons理论

费米子符号在费米液体理论中至关重要. 然而, 在Mott绝缘体中, 很强的电子Coulomb相互作用抑制了体系的电荷涨落并消除了电子交换带来的费米子符号问题. 本文首先回顾二分晶格上Hubbard模型的相位弦理论, 从弱关联的费米液体到强关联的反铁磁Mott绝缘体的转变可以由此得到统一理解. 在任意Coulomb作用强度U下, 我们首先导出Hubbard模型的严格的符号结构. 在小U极限下, 它回到通常的费米子符号; 在大U极限下, 它给出了t-J模型的相位弦符号. 在半满情形下, 我们构造了一种电子分数化的表象, 其中, 电荷子与自旋子通过演生的交互Chern-Simons规范场相互耦合. 由此导出的基态波函数拟设与低能有效理论可以定性刻画Hubbard模型的基态相图. 在弱关联区域, 费米液体的准粒子由电荷子与自旋子的束缚态构成, 其长程相位相干性取决于背景自旋的关联性质. 体系的Mott转变可以通过电荷子打开能隙或是通过自旋子玻色凝聚来实现.     

基于空间模型测量点的照度比值的CIE标准一般天空类型选择

为了计算自然光照度,需要从CIE定义的15种天空类型中正确选择一种对应当前实际天空。首先根据朝向太阳与背向太阳的垂直天空照度的比值将15种天空类型划分为6组,然后根据天空光透过窗口在空间模型两个不同测量点形成的照度的比值对6组天空类型做进一步划分,最终实现对CIE定义的15种天空类型的选择。将天空类型的选择结果与实际天空类型相比较,结果表明,这种天空类型选择方法所得结果可以准确地对应当前实际天空类型。     

HT-7U超导托卡马克装置极向场线圈的等效弹性常数及其残余刚度

HT－7装置的超导极向场线圈由导管，超导材料和绝缘体组合而成，具有复杂的正交各向异性的性质。本文从微观力学的观点出发，将极向场线圈整体作为一种复合材料来考虑，采用微观力学的复合律和损伤力学的细观损伤模型，求出了极向场线圈的等效弹性常数和残余刚度；并且，残余刚度的计算结果已得到了实验验证。这些材料特性已被用于有限元分析的输入数据。     

物理气相沉积减摩与耐磨薄膜

在摩擦学研究的基础上，综合评述与探讨了物理气相沉积薄膜摩擦和磨损的机械－化学作用机理；根据这种机理分析讨论了对物理气相沉积润滑和耐磨薄膜的基本要求，提出了实现这些要求的物理气相沉积的技术基础。     

90°弯管内流动的理论模型及流动特性的数值研究

从三维不可压缩雷诺时均Navier-Stokes方程出发,对90°弯曲管道内湍流流动进行数值模拟。网格划分采用六面体网格,湍流模型为RNGk-ε模型,在近壁区采用两层壁面模型进行修正,流场的计算结果与实验数据吻合较好。在此基础上,本文数值研究了来流方向对流场结构和流动特性的影响。得出在弯管流场中发生了分离现象,且随着来流侧滑角的增大,分离区范围增大。此外,随着来流从同一侧滑角变换至同一攻角时,横截面的二次流图像中也从具有两个对称主涡变成只具有一个主涡的现象。