不同密度流体中颗粒物质的隆起运动实验

1　引　言颗粒物质普遍存在于自然界之中 ,它与工业、农业、医学以及环境科学密切相关 ,还与沙丘形成、陆地侵蚀和滑坡等环境科学有直接的关系。它具有既不同于流体物质也不同于固体物质的独特物理性质。但是长久以来 ,人们对于颗粒物质的了解并不多 ,直到 80年代末期才引起人们的高度重视。尽管如此 ,由于对颗粒物质的研究起步较晚 ,加上其独特性 ,目前描述解释颗粒物质行为的成熟的系统理论还没有完全形成 ,也就是说 ,对颗粒物质 ,人们还不能像对流体 ,气体一样 ,用十分完备的流体动力学 ,能量方程等比较深入的加以描述解释。为了尽可能精…     

从冷冻干燥前驱体合成纳米铁粉

冷冻干燥技术是制备纳米铁粉的一项非常重要的技术。超细铁粉（60～1180）在空气中很稳定并具有显著的磁性能，它是由超细赤铁矿粉（30～50）在200℃还原制成的，而这种超细赤铁矿粉又是由冷冻干燥氮化铁前驱体分解制备的。冷冻干燥工艺显然是生产和开发低成本的磁性记录和“抛弃”铁催化剂等颗粒媒质的先进方法。从冷冻干燥前驱体合成纳米铁粉@E.Bermejo     

浅谈现代室内设计中对光的运用

在现代社会中,随着飞速发展的信息时代的到来。室内设计无论是空间概念,思维方式还是表现手段都随着时间发生了很大的改变。人们对室内空间的物质功能和精神功能都有着更多层面的要求。在现代室内设计中光的语言作为室内设计中的重要语言,已被越来越多的人在设计中作为非常重要的表现形式来运用。光的作用越加从附体转化为主体,从功能转化为精神,逐渐形成了以它为中心系统的理论。     

噪声控制问答四则

1.问:厨房里炉灶上通常有一个抽气罩把油气排放到室外而使室内空气清洁,那么车间内的噪声能否也用一个类似的吸声器来吸掉呢?答:不能.因为噪声不是一种物质,而是由物质振动所产生的一种现象.空气和空气中的物质可以用抽气办法来排掉,而空气中各质点的振动是层层向外传播的,并且以相当快的速度—340米/秒传播.你把这部份空气抽掉,周围的空气马上补充到这区域内,因此车间内总是充满着空气,对噪声的传播也就几乎没有什么变化.除非你把车间抽成真空,使声波赖以传播的媒质——空气不存在时,噪声才无从传播.当然这种设想在这里是不现实的.     

有单面粘弹负载层时各向同性薄板中的SH波传播

1.引言 随着现代工业的发展,SH波传感检测成为在线检测板状构件的有力手段,人们在理论和实验上都对SH波的传播做了很广泛的研究.粘弹材料的应用也越来越广泛,现实生活中的很多材料都具有粘弹特性,由于媒质衰减的存在,使得我们不能将这些材料近似作为弹性材料考虑.这使我们有必要讨论和研究粘弹材料中的声传播特性和它的传感特性[3].     

绣花艺术在织锦画中的运用

传统刺绣在我国盛传已久,有着十分娴熟的制造工艺,传统刺绣工艺虽然受到了广泛认可,然而这种织造工艺既费时又费力,同时还存在图案花色少及不精确的弊端,在织锦画中应用手工绣花艺术,可以使两者的优势相得益彰,具有非常高的艺术品价值.     

影响磁性纳米颗粒膜吸波性能的主要因素

基于Landau-Lifshitz-Gilbert方程、Bruggeman有效媒质理论及纳米颗粒膜的电输运和介电理论,通过计算磁性纳米颗粒膜的有效磁导率、有效介电常数、计算分析饱和磁化强度、各向异性场、电导率和阻尼系数对纳米颗粒膜吸波性能的影响.结果表明,饱和磁化强度、各向异性场、电导率和阻尼系数均对纳米颗粒膜的微波吸收特性产生显著影响,通过调控纳米颗粒膜的电磁特性可以有效提高其吸波性能,可以应用于薄层吸波材料的设计中.     

《微纳米颗粒复合与功能化设计》内容提要

<正>将某种物质的微纳米尺度的颗粒包覆于另一种较大尺度的颗粒表面或弥散分布于其中,就可以获得具有良好的分散性、流动性、表面化学活性和特定的电、磁、热、光学等性能的复合颗粒,这种复合颗粒就是合成、制造新型材料的基本原料。从颗粒复合的工艺入手,还可以实现对材料的结构及功能的设计     

颗粒流动模型研究进展

颗粒流动在自然界中和各种工业过程中广泛存在,但人们对于其机理认识的还不深入。描述颗粒运动的模型有很多,连续介质模型应用简单但准确性比较低,离散微粒学模型是近来人们研究的一个热点,以每个颗粒为考察对象,能够更准确地反应颗粒系统的性质。本文介绍了描述颗粒流动的模型,概述了各模型的理论和应用,通过对多种模型的比较可以看到,每个模型都有一定的使用范围,要更准确、更方便地描述颗粒系统的运动,还要进行深入地研究。     

黑臭水体处理中微生物的应用

微生物具有繁衍速度快、培养周期短的特点,转化效率、适应能力非常强,很多城市都用微生物来对城市黑臭河道进行治理,并且微生物这种生物生态治理技术还有着可重复利用、成本非常低、自身的生态效益非常好的特点,在城市的发展过程中黑臭水体已经成为阻碍城市发展的一个重型污染源,为了城市的进一步发展,我们必须要对城市的黑臭水体进行污染治理。本文就黑臭水体处理中微生物的应用进行分析,希望能够有效地改善城市的水体污染现状,使人们生活环境和质量得到改善。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.