Numerical investigation of a double-junction a:SiGe thin-film solar cell including the multi-trench region

We present a new approach based on the multi-trench technique to improve the electrical performances, which are the fill factor and the electrical efficiency. The key idea behind this approach is to introduce a new multi-trench region in the intrinsic layer, in order to modulate the total resistance of the solar cell. Based on 2-D numerical investigation and optimization of amorphous SiGe double-junction (a-Si:H/a-SiGe:H) thin film solar cells, in the present paper numerical models of electrical and optical parameters are developed to explain the impact of the multi-trench technique on the improvement of the double-junction solar cell electrical behavior for high performance photovoltaic applications. In this context, electrical characteristics of the proposed design are analyzed and compared with conventional amorphous silicon double-junction thin-film solar cells.     

Concerning the maximum frequency limits of Gunn operators

The length of the transit region of a Gunn diode determines the natural frequency at which it operates in fundamental mode－the shorter the device, the higher the frequency of operation. The long-held view on Gunn diode design is that for a functioning device the minimum length of the transit region is about 1.5 μm, limiting the devices to fundamental mode operation at frequencies of roughly 60 GHz. The authors posit that this theoretical restriction is a consequence of limits of the hydrodynamic models by which it was determined. Study of these devices by more advanced Monte Carlo techniques, which simulate the ballistic transport and electron-phonon interactions that govern device behaviour, offers a new lower bound of 0.5 μm, which is already being approached by the experimental evidence shown in planar and vertical devices exhibiting Gunn operation at 0.6 μm and 0.7 μm. It is shown that the limits for Gunn domain operation are determined by the device length required for the transferred electron effect to occur(approximately 0.15 μm, which as demonstrated is largely field independent) and the fundamental size of the domain(approximately 0.3 μm). At this new length, operation in fundamental mode at much higher frequencies becomes possible－the Monte Carlo model used predicts power output at frequencies over 300 GHz.     

剪切载荷条件下镍基单晶合金裂纹扩展与微观结构演化行为研究（英文）

利用分子动力学方法研究了镍基单晶合金在剪切载荷下的裂纹扩展和微观结构演化,分析了应力-应变、势能和裂纹生长速率的变化。同时,揭示了温度和剪切应变率对裂纹扩展和微观结构演化的影响。结果表明,临界分切应力随温度的降低和应变速率的增大而增大;随着温度的升高以及剪切载荷下发生剧烈的热运动,裂缝表现为加速扩展的趋势;而在较高的应变率影响下,会形成位错塞积和孪晶,出现加工硬化现象。     

剪切载荷条件下镍基单晶合金裂纹扩展与微观结构演化行为研究

目前拉伸载荷下的镍基单晶合金的力学性能研究较为广泛,而剪切载荷对镍基单晶合金的力学性能也十分重要但缺乏研究。本文利用分子动力学方法研究了镍基单晶合金在剪切载荷下的裂纹扩展和微观结构演化,分析了应力-应变、势能和裂纹生长速率的变化。同时,揭示了温度和剪切应变率对裂纹扩展和微观结构演化的影响。结果表明,临界分切应力随温度的降低和应变速率的增大而增大;随着温度的升高以及剪切载荷下发生剧烈的热运动,裂缝表现为加速扩展的趋势;而在较高的应变率影响下,会形成位错塞积和孪晶,出现加工硬化现象。     

Mixed convection in the heated semi-circular lid-driven cavity for nonNewtonian power-law fluids: Effect of presence and shape of the block

The present work delineates the hydrodynamics and thermal characteristics due to mixed convection in the liddriven semi-circular cavity affected by the presence of the adiabatic block at its geometric center for twodimensional, steady-state, laminar and for non-Newtonian power-law fluids. The semi-circular cavity has a diameter of D. The horizontal wall/lid is sliding with a uniform horizontal velocity(u = U) and is subjugated to the ambient thermal condition; while the curved surface is subjugated to a higher isothermal temperature.The convective characteristics inside the system is explored for the broad range of Richardson number(0.1 ≤Ri ≤ 10), Prandtl number(1 ≤ Pr ≤ 100) and non-Newtonian power-law index(0.5 ≤ n ≤ 1.5) at a constant Grashof number of 10~4. Apart from this, the effect of shape(cross-section) of the inserted block, i.e., circular, square and triangular on heat transfer characteristics has also been explored. It is observed that the shear thickening fluids display better cooling characteristics. Besides, the cavity with immersed triangular block shows better heat transfer results than the circular and square blocks. The deviations observed in the flow and heat transfer characteristics in the cavity by inserting an adiabatic block as compared with cavity without block have been ascertained by calculating normalized Nusselt number(Nu~N). The presence of the block was found to have a diminishing effect on the heat transfer due to convection in the cavity. In the end, the results of the study are summarized in the form of a predictive correlation exhibiting the functional dependence of average Nusselt number with Prandtl number, power-law index, and Richardson number.     

表面粗糙和带槽的湿式离合器接合的有限元模型

已经开发了一个有限元模型,研究表面粗糙和带槽纸质可渗透的湿式离合器的接合特性。采用有限元方法(Galerkin)离散修正雷诺和力平衡方程式,采用等参量方程式解所描述的有关内何学。通过Patir和Cheng(1978)的通用流量模型模拟表面粗糙度的影响。在表面粗糙状况下,采用Greenwond和William son(1966)方法计算负荷分配,采用开发的有限元模型研究所加负荷的影响,以及湿式离合器摩擦材料的渗透率和槽出入口尺寸的接合特性(即转矩、油压、接合时间和油膜厚度)。研究结果表明,所加负荷、摩擦材料渗透率和槽宽度对接合特性的影响显著。高的配合面压力增大了峰值和减少了接合时间但显著增大了峰值转矩,宽油槽减少峰值转矩和增加了接合时间。对于本模型油槽深度对接合特性的影响不太明显。     

朴素的诗意

正最近热映的纪录片《四个春天》,导演记录了四年间自己一家人春节前后的日常生活情景。剧中最让人倾羡是爸爸和妈妈的感情以及他们朴素又充满乐趣的生活。生活在贵州一个小城的爸爸妈妈,虽已年迈,但依然会自己动手熏腊肠、上山采蕨菜、相互理发,二人相互陪伴,互相依偎;同时爸爸妈妈的身上还有着浓浓的艺术气息,爸爸会演奏多种乐器,妈妈也会随时高歌一曲、扭动华尔兹舞步,他们的生活平实质朴,却充满着欢乐。整部影片以爸爸妈妈为主角展现了一     

Querying dynamic communities in online social networks简

Online social networks （OSNs） offer people the opportunity to join communities where they share a common interest or objective. This kind of community is useful for studying the human behavior, diffusion of information, and dynamics of groups. As the members of a community are always changing, an efficient solution is needed to query information in real time. This paper introduces the Follow Model to present the basic relationship between users in OSNs, and combines it with the MapReduce solution to develop new algorithms with parallel paradigms for querying. Two models for reverse relation and high-order relation of the users were implemented in the Hadoop system. Based on 75 GB message data and 26 GB relation network data from Twitter, a case study was realized using two dynamic discussion communities：#musicmonday and #beatcancer. The querying performance demonstrates that the new solution with the implementation in Hadoop significantly improves the ability to find useful information from OSNs.     

Facile synthesis of SrCO3nanostructures in methanol/water solution without additives

ABSTRACT: Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N2 adsorption-desorption. The results showed that the reaction temperature and the ethanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m2g1 and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented.     

1200mm直径条筒的优点

正条筒直径在过去20多年内明显增加,且已建立了采用直径为1 000mm条筒时的技术方法。2015年,在意大利米兰举办的国际纺织机械展览会(ITMA)上,德国Trutzschler公司展出了直径为1 200mm的条筒,它是由喂入速度比旋转式条筒更快的T型筒改进形成的(图1)。亚琛工业大学纺织技术研究所(ITA)调查了这项革新的投入和产出,研究在Trutzschler公司投资的两条样品生产线的纺纱厂内进行。