Stress relief patterns of Co films deposited on circular silicone oil substrates

By using the expansive and mobile properties of silicone oil, circular liquid substrates with varied thicknesses naturally form on clean glass surfaces during deposition. Continuous cobalt (Co) films have been prepared on the circular liquid substrates by a direct current magnetron sputtering method, and the stress relief patterns of the Co films are investigated. The experiment shows that the Co film is susceptible to generating cracks due to thermal expansion of the silicone oil substrate during deposition. After deposition, subsequent cooling of the system creates a high compressive stress in the film, which is relieved by formation of various wrinkling morphologies. Based on the special growth mechanism and mechanical properties of the metal film deposited on a liquid substrate, the structural characteristics of the stress relief patterns and the underlying physical mechanisms are discussed in detail.     

Preparation of CNT-hybridized carbon fiber by aerosol-assisted chemical vapor deposition

The purpose of this article is to find a way to prepare multiscale material, namely, carbon nanotube-hybridized carbon fiber (CNT/CF) with a low degradation of mechanical properties. Using a facile aerosol-assisted chemical vapor deposition method, a novel route was described to fabricate CNT/CF. The essential of this technique was in situ formation of catalyst (Fe) nanoparticles via pyrolysis of ferrocene–acetone aerosol right before CNTs growth. Through optimizing aerosol supply and process parameters, a uniform coverage of CNTs was successfully grafted onto the carbon fiber surface to obtain a multiscale (hierarchical) structure. The strong anchorage between the as-synthesized CNTs and carbon fiber substrate was confirmed by ultrasonic bath treatment. Compared with the as-received carbon fibers, single fiber tensile testing results demonstrated that the tensile strengths of CNT-hybridized carbon fiber slightly degraded within 10% at all the correspondingly given gauge lengths.     

市场不确定下存货质押融资后企业利润的定量分析

针对市场波动、存在诸多不确定性因素的情况下,资金需求企业难以对采用存货质押融资业务后的利润进行评估的问题,建立了存货质押融资后的企业利润模型,采用证据理论分别对2种类型的专家信息进行融合,据此构造不确定参数的概率分布。在此基础上,运用Monte Carlo抽样得出采用存货质押业务后企业利润的概率分布。数值算例表明,该方法简单有效,比区间分析法得到的结果更具实际指导意义,可为风险厌恶、风险偏好等各类决策者提供融资后利润的定量分析结果。     

Photothermal self-oscillation and laser cooling of graphene optomechanical systems

By virtue of their low mass and stiffness, atomically thin mechanical resonators are attractive candidates for use in optomechanics. Here, we demonstrate photothermal back-action in a graphene mechanical resonator comprising one end of a Fabry-Perot cavity. As a demonstration of the utility of this effect, we show that a continuous wave laser can be used to cool a graphene vibrational mode or to power a graphene-based tunable frequency oscillator. Owing to graphene's high thermal conductivity and optical absorption, photothermal optomechanics is efficient in graphene and could ultimately enable laser cooling to the quantum ground state or applications such as photonic signal processing.     

Single photon counting from individual nanocrystals in the infrared

Experimental restrictions imposed on the collection and detection of shortwave-infrared photons (SWIR) have impeded single molecule work on a large class of materials whose optical activity lies in the SWIR. Here we report the successful observation of room-temperature single nanocrystal photoluminescence at SWIR wavelengths using a highly efficient multielement superconducting nanowire single photon detector. We confirm that the photoluminescence from single lead sulfide nanocrystals is strongly antibunched, demonstrating the feasibility of performing sophisticated photon correlation experiments on individual weak SWIR emitters, and, more broadly, paving the way for sensitive measurements of spectral observables on infrared quantum systems that are incompatible with current detection techniques.     

Exciton scattering mechanism in a single semiconducting MgZnO nanorod

Excitonic phenomena, such as excitonic absorption and emission, have been used in many photonic and optoelectronic semiconductor device applications. As the sizes of these nanoscale materials have approached to exciton diffusion lengths in semiconductors, a fundamental understanding of exciton transport in semiconductors has become imperative. We present exciton transport in a single MgZnO nanorod in the spatiotemporal regime with several nanometer-scale spatial resolution and several tens of picosecond temporal resolution. This study was performed using temperature-dependent cathodoluminescence and time-resolved photoluminescence spectroscopies. The exciton diffusion length in the MgZnO nanorod decreased from 100 to 70 nm with increasing temperature in the range of 5 and 80 K. The results obtained for the temperature dependence of exciton diffusion length and luminescence lifetime revealed that the dominant exciton scattering mechanism in MgZnO nanorod is exciton-phonon assisted piezoelectric field scattering.     

一维EEP自适应技术新进展:从线性到非线性

有限元后处理中超收敛计算的EEP(单元能量投影)法以及基于该法的自适应分析方法对线性ODE(常微分方程)问题的求解已经获得了全面成功,也推动了非线性ODE问题自适应求解的研究。经过研究,已经实现了一维有限元自适应分析技术从线性到非线性的跨越,该文意在对这方面的进展作一简要综述与报道。该文提出一种基于EEP法的一维非线性有限元自适应求解方法,其基本思想是通过线性化,将现有的线性问题自适应求解方法直接引入非线性问题求解,而无需单独建立非线性问题的超收敛计算公式和自适应算法,从而构成一个统一的、通用的非线性问题自适应求解算法。该文给出的数值算例表明所提出的算法高效、稳定、通用、可靠,解答可逐点按最大模度量满足用户给定的误差限,可作为先进高效的非线性ODE求解器的核心理论和算法。     

溶剂对偶氮苯酚羟基反应选择性的影响

分别通过选择二氯甲烷和四氢呋喃为溶剂,使在含有两个活性羟基的4-硝基-2′,4′-二羟基偶氮苯(镁试剂)与对氯甲基苯甲酰氯的酯化反应中,镁试剂发生选择性的对位羟基取代,得到4-硝基-2′-羟基-4′-对氯甲基苯甲酰氧基偶氮苯。用1H-NMR证实了产物结构。结果表明,在含有分子内氢键的镁试剂参与的选择性酯化反应中,二氯甲烷比四氢呋喃更适合作反应溶剂,产率从15%提高到40%。     

Structure and magnetostriction of Tb0.4Nd0.6(Fe0.8Co0.2)1.90 alloy prepared by solid-state synthesis

Mechanical alloying (MA) and subsequent solid sintering process was used to prepare the Nd-containing magnetostrictive Tb0.4Nd0.6(Fe0.8Co0.2)1.90 alloy. The structure, thermal stability and phase transformation were investigated as functions of composition, milling process and annealing temperature. An amorphous phase was formed by high-energy ball milling for 5 h with the ball-to-powder weight ratio of 20:1, which crystallized into MgCu2-type and PuNi3-type crystalline structure with different annealing temperatures. The magnetoelastic properties were investigated by means of a standard strain technique. The high Nd-content (Tb,Nd)(Fe,Co)2 Laves phase for the composition Tb0.4Nd0.6(Fe0.8Co0.2)1.90 was synthesized by MA process plus annealing at 500 ℃ for 30 min.     

SG186系统台区售电量计算的缺陷及处理方法

针对"SG186湖北营销业务应用系统"中台区售电量统计差异影响台区线损率统计问题,从数据结构出发,基于数据库设计的E-R简图,对比新旧系统在低压线损计算中的数据映射关系,分析了计算方法差异及线损统计中可能出现的差错,并提出了解决方案,规范了用户抄表段调整操作步骤,规避了低压台区线损率计算的差错.