Atmospheric extinction properties in Shenyang,China

Atmospheric visibility impairment due to human activities is becoming increasingly significant in metropolitan Shenyang, China. In this study, hourly data of relevant factors throughout the year 2010 in Shenyang were used to evaluate the local atmospheric extinction properties. The results show that the average coefficient of total extinction and aerosol single-scattering albedo in 2010 were 622.72 Mm⁻¹ and 0.87, respectively, values that are characteristic of the “municipal pollution type”. Visibility is most impaired during winter and especially in January. The coefficient of total extinction exhibits a single daily cycle with a maximum at 5–6 am and a minimum at 3 pm. The mean extinction contributions of the constituents, from high to low, were particle scattering (87.49%), particle absorption, gas absorption, and gas scattering. The extinction contribution of gas molecules was little more than 4.5%, far smaller than that of particles. Scattering by particles was the main contributor to extinction, especially in the morning and around midnight.     

一种爆炸二极管机理研究及熄爆通道尺寸对其性能的影响

依据爆炸逻辑元件的工作原理设计了一种爆炸二极管。实验研究了元件内部结构,确定了关键参数为熄爆通道的长度、隔爆序列。隔爆序列内采用激发装置、一次PETN装药、两次PETN装药不同密度分层装药序列。在A、B端连接导爆索,改变熄爆通道尺寸, 确定分层装药参数,进行传爆可靠性、隔爆安全性实验。结果表明:爆轰信号由A端正向输入时,可以顺利通过10~35 mm的熄爆通道并且可靠引爆B端导爆索,满足可靠性功能;爆轰信号由B端反向输入,在熄爆通道长度为15~35 mm时,爆轰信号在通过隔爆序列、熄爆通道时被可靠阻断无法引爆A端导爆索,满足隔爆安全性功能。最终元件选取长度为15~35 mm的熄爆通道, 确定不同密度分层装药参数作为设计标准。应用于爆破网络设计中,使爆轰波信号在网络中单向传播,增加了网络的安全性。     

Impacts of aerosol chemical compositions on optical properties in urban Beijing,China

The optical properties of aerosols and their chemical composition,including water-soluble ions,organic carbon（OC）,and elemental carbon（EC） in PM_2.5 and PM₁₀,were measured from 26 May to 30 June of 2012 at an urban site in Beijing.The daily average concentrations of PM_2.5 and PM₁₀ were 103.2 and 159.6 μg/m³,respectively.On average,the OC and EC contributed 20.1% and 4.3% ,respectively,to PM_2.5 and 16.3% and3.9% ,respectively,to PM₁₀.Secondary ions(SO₄^2-,NO₃^-,and NH₄⁺) dominated the water-soluble ions and accounted for 57.9% and 62.6% of PM_2.5 and PM₁₀,respectively.The wind dependence of PM_2.5,OC,SO₄^2-,and NO₃^- implied that the pollution sources mainly came from south and southeast of Beijing during the summer.The monthly mean values of the scattering coefficient(σ_sc) and absorption coefficient(σ_ab) at525 nm were 312.9 and 28.7 Mm^-1,respectively,and the mean single-scattering albedo（ω） was 0.85.The wind dependence of σ_sc revealed that this value was mainly influenced by regional transport during the summer,and the relationship between σ_ab and wind indicated that a high σ_ab resulted from the joint effects of local emissions and regional transport.The reconstructed σ_sc that was derived from the revised IMPROVE equation agreed well with the observations.The contribution of different chemical species toσ_sc was investigated under different pollution levels,and it was found that secondary inorganic aerosols accounted for a large part of σ_sc during pollution episodes（35.7% ）,while organic matter was the main contributor to σ_sc under clean conditions（33.6% ）.     

Atmospheric boundary layer simulation in a wind tunnel, using air injection

The inner part of a neutral atmospheric boundary layer has been simulated in a wind tunnel, using air injection through the wind tunnel floor to thicken the boundary layer. The flow over both a rural area and an urban area has been simulated by adapting the roughness of the wind tunnel floor. Due to the thickening of the boundary layer the scaling factor of atmospheric boundary layer simulation with air injection is considerably smaller than that without air injection. This reduction of the scaling factor is very important for the simulation of atmospheric dispersion problems in a wind tunnel.The time-mean velocity distribution, turbulence intensity, Reynolds stress and turbulence spectra have been measured in the inner part of the wind tunnel boundary layer. The results are in rather good agreement with atmospheric measurements.Nomenclature d Zero plane displacement, m - h Height of roughness elements, m - k Von Kármán's constant - n Frequency of turbulence velocity component, s^–1 - S _u(n) Energy spectrum for longitudinal turbulence velocity component, m² s^–1 - S _v(n) Energy spectrum for lateral turbulence velocity component, m² s^–1 - S _w(n) Energy spectrum for vertical turbulence velocity component, m² s^–1 - U _o Free stream velocity outside the boundary layer, m s^–1 - Time-mean velocity inside the boundary layer, m s^–1 - u* Wall-friction velocity, m s^–1 - u Longitudinal turbulence intensity, m s^–1 - v Lateral turbulence intensity, m s^–1 - w Vertical turbulence intensity, m s^–1 - Reynolds stress, m² s^–2 - z Height above earth's surface or wind tunnel floor, m - z _o Roughness length, m - Thickness of inner part of boundary layer, m - Thickness of boundary layer, m - Kinematic viscosity, m² s^–1     

Stratified Turbulence in the Atmospheric Mesoscales

The first author proposed earlier that the atmospheric energy spectrum in the mesoscale range is controlled by upscale energy transport in stratified and geostrophic turbulence, with the source of the energy probably convective clouds and storms. This hypothesis is reviewed in the light of a variety of theoretical and mechanistic tests, mostly involving numerical simulation. Some conflicting results are noted, with fluid dynamics simulations mostly negative and meteorological simulations positive, including one new set presented here. The rapid increase in larger-scale energy shown in our simulations should, however, be ascribed in part to a different mechanism, involving the rapid growth of the unconstrained outflow and its further spreading by mean shear. Received 23 May 1997 and accepted 21 February 1998     

Light extinction technique for void fraction measurements in bubbly flow

 The analysis of the scattering induced by a dispersion of gas bubbles in a liquid medium on a collimated, monochromatic light beam, traversing the two-phase flow, allows for the direct measurement of the 2-D distribution of the line-average of the interfacial area density. The 2-D distribution of the line-average of the void fraction is deduced from that of the interfacial area density through an image processing algorithm. To demonstrate the technique, experiments are performed in a pool of water injected with air and illuminated with a CW argon ion laser. Since the bubble diameters range from a fraction of a millimeter to a few millimeters, the scattering processes are entirely in the Mie range. The limits of applicability of the technique and the measurement uncertainty are discussed. The results compare favorably with level-swell based measurements used as a reference. Received: 14 February 1997/Accepted: 4 February 1998     

Numerical investigation of flame propagation and extinction in a vertical channel

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 4, pp. 18–26, July–August, 1992.     

Ground-based measurements of aerosol optical properties and radiative forcing in North China

In order to gain an insight into the aerosol properties and their climatic effect over the continental source regions of China, it is of significance to carry out long-term ground-based measurements of aerosol optical properties and radiative forcing. A couple of temporary and permanent Aerosol Robotic Network （AERONET） sites and three comprehensive radiative sites were established in China as a result of international cooperation in recent years. Heavy aerosol loading and significant temporal and spatial variation over North China are revealed by the AERONET data. Aerosol-induced reductions in surface radiation budget are examined on the basis of collocated observations by sun photometers and pyranometers. 2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.     

Atmospheric pressure waves in the field of volcanology

Atmospheric pressure waves are a notable phenomenon associated with explosive volcanic eruptions. They can provide us with information about eruption processes that are useful both scientifically and practically. In this paper, we give a brief review of studies that have been carried out on this phenomenon in the field of volcanology. Then, we introduce a prototype tool called ‘MOVE’ (Mobile Observatory for Volcanic Explosions). It is a remote-controlled vehicle carrying various instruments to observe pressure waves and the eruption processes. PACS 91.40.Dr · 91.40.Ft · 93.65.+e · 93.85.+qThis paper was based on work presented at the 2nd International Symposium on Interdisciplinary Shock Wave Research, Sendai, Japan on March 1–3, 2005.     

Dynamics of a discrete population model for extinction and sustainability in ancient civilizations

We analyze a discrete version of a recently developed ratio dependent population-resource model. This model has been used to study the decline of the human and resource populations on Easter Island and the chaotic dynamics of moose and wolf populations in Canada. The dynamical system exhibits a rich behavior of fractal basins of attraction and a Neimark-Sacker bifurcation route to chaos. The model consists of a coupled pair of logistic equations, with the carrying capacity for the predators proportional to the number of prey.     

Optimization of regularization parameter of inversion in particle sizing using light extinction method

In particle sizing by light extinction method, the regularization parameter plays an important role in applying regularization to find the solution to ill-posed inverse problems. We combine the generalized cross-validation （GCV） and L-curve criteria with the Twomey-NNLS algorithm in parameter optimization. Numerical simulation and experimental validation show that the resistance of the newly developed algorithms to measurement errors can be improved leading to stable inversion results for unimodal particle size distribution.     

Study of the extinction of gunpowder in the combustion model with a variable surface temperature

The results of a calculation of the rate of transient combustion of gunpowder during a fall in pressure are presented; these are obtained by the numerical integration of the equations of transient-combustion theory, allowing for the variable surface temperature of the k phase. For rapid and severe pressure drops extinction always occurs, no introduction of special extinction conditions being required. The change in the rate of burning during the extinction process is of a smooth nature.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 92–100, May–June, 1973.     

在1.4米航空风洞中模拟大气边界层

在风洞中正确模拟大气边界层的流动特性是风工程风洞试验结果可信的必要条件,本次试验研究的目的是在短试验段的航空风洞中建立大比例的大气边界层模拟流场。通过适当的方式延长1.4m×1.4m航空风洞的试验段长度,并利用尖塔、粗糙元等边界层发生装置,在该风洞中建立了边界层流场,测量了流场的平均风速剖面、湍流强度剖面、脉动风速的自相关系数、风谱等参数,讨论了湍流积分尺度的处理和大气边界层几何模拟比例的确定,用谱拟合法和自相关系数积分法求出了湍流积分尺度。结果分析表明:试验所得流场是合理的大气边界层模拟流场,其平均风速剖面幂指数α=0.3,大气边界层模拟比例为1∶500,为后续的建筑物模型动态风荷载试验提供了前提条件。     

Variational formulations,convergence and stability properties in nonlocal elastoplasticity

A thermodynamically consistent formulation of nonlocal plasticity in the framework of the internal variable theories of inelastic behaviors of associative type is presented. A family of mixed variational formulations, with different combinations of state variables, is provided starting from the finite-step nonlocal elastoplastic structural problem. It is shown that a suitable minimum principles provides a rational basis to exploit the iterative elastic predictor-plastic corrector algorithm in terms of the dissipation functional. A sufficient condition is proved for the convergence of the iterative elastic predictor-plastic corrector algorithm based on a suitable choice of the elastic operator in the prediction phase and a necessary and sufficient condition for the existence of a unique solution (if any) of the nonlocal problem at hand is then provided. The nonlinear stability analysis of the nonlocal problem is carried out following the concept of nonexpansivity proposed in local plasticity.     

Numerical evaluation of extinction angle and birefringence in various directions as a function of velocity gradient

Despite the limitations of the theory of Peterlin and Stuart it still seems to be the best theory for interpreting quantitative flow birefringence measurements performed on solutions of rigid spheroidal particles. First, we repeat the numerical evaluation of the extinction angleX and the orientation factorf _z corresponding to conventional observations realized in a Couette cell, but the values are now given with a higher degree of accuracy and the range of variation of the parameters has been extended. Furthermore, using the same theory, we extend our calculations to other directions of observation. This should contribute towards avoiding false interpretations of birefringence measurements in these directions (as has sometimes occurred). Finally, we present measurements taken along the lines of flow and along the direction of the velocity gradient, thus including the principal situations met in the various cells used in flow birefringence measurements.     

Variation of PM2.5 concentration in Hangzhou,China

This observational study investigates the variation of PM_2.5 concentration and its ratio against PM₁₀ concentration under different weather systems and pollution types. The study was conducted in Hangzhou on east China's Yangtze River Delta using data collected at seven ambient air quality monitoring stations around the metropolitan area between 2006 and 2008 and using weather information in the same period. Nine predominant weather systems affecting the city were classified through careful analysis of the 11-year surface and upper air weather charts from 1996 to 2006. Each observational day was then assigned to one of the nine weather systems. It was found that the PM_2.5 concentration varied greatly for different weather systems, with the highest PM_2.5 concentration associated with the post-cold-frontal system at 0.091 mg/m³ and the lowest PM_2.5 concentration with the easterlies system at 0.038 mg/m³, although the PM_2.5/PM₁₀ ratio remained consistently above 0.5 for all systems. The post-cold-frontal system typically occurs in autumn and winter while the easterlies system is more a summer phenomenon. Among all types of pollution, the highest PM_2.5 concentration of 0.117 mg/m³ coincided with the large-scale continuous pollution events, suggesting that this type of pollution was more conducive to the formation of secondary particulate matters. The ratio of PM_2.5/PM₁₀ was above 0.5 in non-pollution days and all pollution types but one under the influence of dust storms when the ratio decreased to 0.3 or less. The outcomes of this study could be used to develop a rudimental predictive model of PM_2.5 concentration based on weather system and pollution type.     

斗拱的力学性能及其蕴含在中国馆中的民族象征

通过对斗拱的历史演变、力学性能的描述, 概括出斗拱不仅有着与建筑如影随形的兴衰史,而且含蕴着中国精神生活的一个侧面. 时至今日, 斗拱的力学功能虽然有所衰弱, 但上海世博会上的中国馆, 这个外形巨大的红色斗拱以它的标志性、力学美感向世界展示了中国建筑悠久的历史沉积、丰富的文化内涵, 更重要的是向世界展示了中国人民的自信心和民族自豪感. 从而揭示出斗拱蕴含在中国馆中的民族性和审美趣味.     

Determination of microcapsule physicochemical,structural, and mechanical properties

Research into the fundamental properties of microcapsules and use of the results to develop a wide variety of products in industries such as printing, fast-moving consumer goods, construction, pharmaceuticals, and agrochemicals is a dynamic and ever-progressing field of study. For microcapsules to be effective in providing protection from harsh environments or delivering large payloads, it is essential to have a good understanding of their properties to enable quality control during formulation, storage, and applications. This review aims to outline the commonly used techniques for determining the physicochemical, structural, and mechanical properties of microcapsules, and highlights the interlinked nature of these three areas with respect to the end-use industrial application. This review provides information on techniques that are well supported in the literature, and also examines microcapsule analytical techniques that will become more prevalent as a result of new technological developments or extensions from other areas of study.     

Elastic silicon-film-based nanoshells: Formation, properties, and applications

Controllable formation and properties of solid single-crystal micro-and nanoshells of various shapes (tubes and spirals, vertically positioned rings and cylinders, and bent and trough-shaped cantilevers) are briefly reviewed, and new results are given. The shells and complicated structures of prescribed size and shape are formed with the use of elastic energy of initial strained SiGe/Si films of nanometer thickness and methods of highly selective and directed detachment of the films from the silicon substrates. It is experimentally demonstrated that the diameters of the fabricated SiGe/Si nanotubes are several times smaller than the values predicted by the continuum elasticity theory. The properties of the shells made of semiconductor and hybrid (metal-semiconductor and metal-dielectric-semiconductor) films and their applications in micro-and nanoscale electrical engineering are discussed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 114–128, November–December, 2006.