Mo掺杂调控电子结构增强NiS电催化固氮性能

以泡沫镍为骨架,通过水热法制备了Mo掺杂的NiS多级纳米花状结构(Mo-NiS).在偏压为-0.7 V(vs RHE)下,2 h内,0.83 Mo-NiS(制备时钼、镍物质的量之比为0.83)的电催化固氮速率平均可达4.21μg·cm-2·h-1,法拉第效率平均为18％.XPS测试和DFT计算表明,Mo掺杂增加了Ni活...     

基于证据推理的电化学综合实验探究

盐桥的作用众所周知,如果“将铜锌双液原电池的盐桥换成铜片后,电路中还有电流吗?两液中的铜片到底发生了什么反应?”,基于这些问题,开发了一系列实验,利用观察到的各种证据,如:生成的沉淀、溶液颜色的变化、电极质量的改变、溶液pH和电流计指针偏转方向等,引导学生对各个电极变化的反应进行假设,并设计新颖实验逐步探究证实,依据宏...     

利用海洋环境噪声互相关实现阵形校准

阵列信号处理需要准确的阵形,然而海底水平阵的阵形很难精确测量。利用海洋环境噪声可以提取两点间的格林函数,这为无源校准阵形提供了新的可能。通过海洋环境噪声互相关叠加可以获取两个阵元之间的距离信息,一种方法是可以通过该距离与位置之间的关系构建非线性方程组并利用最小二乘法(LS)求解阵形。本文利用多维尺度变换法(MDS)求解,通过对度量矩阵的特征值分解获得阵形。数值仿真和实验数据证明了该方法的可行性,并且MDS相比于LS有更稳健的性能。     

用于矢量水听器的低频高灵敏度层合梁加速度传感器

压电加速度传感器是同振型矢量水听器的核心部件。为了满足低频高灵敏度矢量水听器的应用需求,提出并研究一种具有层合梁结构的低频高灵敏度加速度传感器。结合弹性力学和压电方程推导层合梁加速度传感器的加速度灵敏度解析解表达式,通过有限元仿真对层合梁加速度传感器尺寸进行优化,给出优化后的尺寸范围。从优化的尺寸范围中选取两种不同尺寸进行加速度传感器振动特性的仿真分析及实物制作(其中压电材料为PZT-5)与性能测试。仿真与测试结果均表明,相比已有的同尺寸金属梁加速度传感器,层合梁加速度传感器可以有效降低谐振频率并提升加速度灵敏度。当压电层厚度为0.5 mm时,加速度灵敏度最大提升3.9 dB,谐振频率下降23%。测试结果与理论分析相符。     

一种油田原油含水率的近红外光谱检测与分析方法

石油作为重要战略资源,对其组分进行实时分析检测在石油化工领域有着重要意义.随着石油资源的不断开发,在已长时间开采油井的生产过程中以及新油井开采前,需要对井下原油组分进行分析检测,以判定开采的必要性.原油组分实时检测,在原油开采、生产、储运以及销售过程中都起着关键的作用,针对传统检测方法存在精度低、效率低等问题,近年来在...     

光谱技术分析尿素对BSA糖基化反应的影响

以牛血清白蛋白(BSA)和葡萄糖为原料,采用光谱技术从分子水平上研究不同浓度尿素(0～7 mol·L-1)对BSA糖基化反应的影响.结果表明:BSA经过尿素处理后,其糖基化产物的自由氨基含量和内源荧光强度均显著下降;同步荧光光谱表明BSA与尿素的结合点更接近于色氨酸(Trp)残基;紫外光谱分析表明经尿素处理后BSA的糖...     

0Interacting model of new agegraphic dark energy:observational constraints and age problem

Many dark energy models fail to pass the cosmic age test because of the old quasar APM 08279+5255 at redshift z=3.91,the ΛCDMmodel and holographic dark energy models being no exception.Inthis paper,we focus onthe topic of the age problem inthe new agegraphic dark energy(NADE)model.We determine the age of the universe in the NADE model by fitting the observational data,including type Ia supernovae(SNIa),baryon acoustic oscillations(BAO)and the cosmic microwave background(CMB).We find that the NADE model also...     

哈佛大学有效提升物理教学质量的举措分析

深入探讨了哈佛大学提升物理课程教学质量的举措,诸如卓越的教学方法、全面的教师培养、科学的教学指导、高效的教学评价等.哈佛大学的这些全面、细致、具体、实用的举措对我国大学物理教学质量的提升具有一定的借鉴意义.     

Phase-field modeling of void evolution and swelling in materials under irradiation

Void swelling is an important phenomenon observed in both nuclear fuels and cladding materials in operating nuclear reactors. In this work we develop a phase-field model to simulate void evolution and void volume change in irradiated materials. Important material processes, including the generation of defects such as vacancies and self-interstitials, their diffusion and annihilation, and void nucleation and evolution, have been taken into account in this model. The thermodynamic and kinetic properties, such...     

Two-dimensional coupled vibration and equivalent circuit of longitudinal-longitudinal orthogonal composite vibration direction converter

With the advantages of transmitting energy from multiple directions to one direction and transforming vibration from one source to multiple directions, the two-dimensional vibra?tion direction converter has important applications in power ultrasonic technology. However, for the complexity of using the wave equation to design and analysis the two-dimensional vibration direction converter, a concise equivalent circuit for the converter is investigated. By introducing the two-dimensional mechanical coupling coefficient and the longitudinal force transform coef?ficient, and using the electromechanical analogy principle, the equivalent circuit and resonance frequency equation of the two-dimensional vibration direction converter vibrating in anti-phase and in-phase two-dimensional coupled vibration are deduced. The resonance frequencies of the vibration direction converters of two different materials are calculated by using the proposed frequency equation, which are in agreement with the results from the finite element method and the experimental test. It provides a concise method for the design and applications of such ultrasonic vibration system.