Hydromagnetic Carreau Nanoliquid in Frames of Dissipation and Activation Energy

The novel characteristics of magnetic field and entropy generation in mixed convective flow of Carreau fluid towards a stretched surface are investigated.Buongiornio nanoliquid model consists of thermophoresis and Brownian movement aspects is opted for analysis.Energy expression is modeled subject to thermal radiation and viscous dissipation phenomenon.Concentration by zero mass flux condition is implemented.Consideration of chemical reaction and activation energy characterizes the mass transfer mechanism.Total entropy generation rate and Bejan number is formulated.The utilization of transformation variables reduces the PDEs into non-linear ODEs.The obtained nonlinear complex problems are computed numerically through Shooting scheme.The impact of involved variables like local Weissenberg number,magnetic parameter,thermal radiation parameter,Brownian motion parameter,thermophoresis parameter,buoyancy ratio parameter,mixed convection parameter,Prandtl parameter,Eckert number,Schmidt number,non-dimensional activation energy parameter,chemical reaction parameter,Brinkman number,dimensionless concentration ratio variable,diffusive variable and dimensionless temperature ratio variable on velocity,temperature,nanoparticles concentration,entropy generation,Bejan number,surface drag force and heat transfer rate are examined through graphs and tables.     

非水平直圆管中黏性流体层流流量公式的推导及实验验证

通过牛顿粘滞定律和修正后的伯努利方程对非水平直圆管中黏性流体作层流运动时的流量公式进行了推导。指出将泊肃叶公式中的压强视作广义压强,则文中的推导公式与泊肃叶公式完全一致。说明泊肃叶公式可以用来求解非水平直圆管中黏性流体作层流运动时的流量。本文通过实验验证了推导公式。     

黏性耗散对离心压缩机气动性能的影响

针对小流量系数离心压缩机,考察了流体的黏性耗散效应对流动损失的影响程度.通过压缩机模型级的实验测量和数值模拟,分别分析了压缩机级和叶轮在有、无黏性耗散影响下的流动性能.结果表明:当不考虑黏性耗散损失时,压缩机模型级具有较高效率;在黏性耗散效应的影响下,流动的多变效率约降低8个百分点.另外,不同的机壳间隙对多变效率也存在...     

Analysis of Melting Heat Transport in a Cross Flow Direction: A Comparative Study

An incompressible three-dimensional laminar flow in a cross flow direction is described in this work. The term of melting and viscous dissipation is incorporated in the mathematical modeling of present flow problem. The flow expressions are converted into dimensionless equations, which are solved with help of Runge-Kutta scheme. Impact of the emerging parameters on the non-dimensional velocities and temperature and friction-factors and local Nusselt number are examined. The convergence analysis is found for ∈ < 0 and 0 < ∈ ≤ 2. Comparative analysis is made between the obtained results and published data for limiting case. It is explored at the surface that the melting parameter retards the liquid temperature while it enhances the fluid velocity.     

Activation Energy for the Glass Transition of a Confined Elastomer in HDPE/PP Blends

Blends of two highly crystalline polymers containing an elastomer were prepared to study the glass transition of the confined elastomer. The polymers chosen were high density poly ethylene (HDPE), polypropylene (PP), and two elastomers of a different nature: natural number (NR) and EPDM. The dynamic mechanical analyzer (DMA) technique was used to analyze the storage modulus of blends with elastomer content from 0% to 30% by weight, with the remainder made up of equal amounts of HDPE and PP, and blends with 10% of the elastomer, but varied ratios of polyolefins. We used the differentiation modification of the Arrhenius method in the kinetic analysis assuming an n‐order relaxation mechanism, which allowed detecting the percolation threshold of NR. Results indicate that both temperature and activation energy for glass transition (T _g ) are dependent on the types of polymers in the blend and blend composition. The T _g and E values of the unblended elastomers are higher than those in blends; this behavior is associated with the elastomer confinement and blend morphology.     

Activation of silicon quantum dots for emission

The emission of silicon quantum dots is weak when their surface is passivated well. Oxygen or nitrogen on the surface of silicon quantum dots can break the passivation to form localized electronic states in the band gap to generate active centers where stronger emission occurs. From this point of view, we can build up radiative matter for emission. Emissions of various wavelengths can be obtained by controlling the surface bonds of silicon quantum dots. Our experimental results demonstrate that annealing is important in the treatment of the activation, and stimulated emissions at about 600 and 700 nm take place on active silicon quantum dots.     

质子椭圆流与对称能的密度依赖性

基于同位旋和动量依赖的强子输运IBUU04模型, 研究了¹³²Sn+¹²⁴Sn碰撞系统中的质子椭圆流对对称能的敏感关系. 研究发现入射能量从每核子400MeV到800MeV时质子椭圆流在低横动量端对对称能的敏感性高于高横动量端, 同时发现随着入射能量的增大, 质子椭圆流对对称能的敏感性在降低. 在研究入射能量范围内, 当入射能量为每核子400MeV左右时质子椭圆流对对称能最为敏感.     

绝对式高能量激光能量计温度特性研究

对绝对式量热法高能量激光能量计吸收腔的内、外壁温度差特性进行了详细的理论研究和实验验证。用第二非齐次边界条件和第二齐次边界条件的热传导方程分别建立了吸收腔在激光加热过程中和激光加热结束后的温度分布，利用模拟实验对激光照射吸收腔的过程进行模拟，得到内、外壁温度差的实验数据。利用数值模拟法，对理论分析结果作数值分析，理论分析结果与实验数据非常接近，从而证明了在激光加热过程中，虽然吸收腔内外壁存在固定的温度差，但当激光结束后，该温度差将迅速减小，吸收腔达到热平衡。     

兰州CSR能区238U238U碰撞椭圆流模拟研究

用相对论输运模型模拟了束流动能为520MeV/u的²³⁸U＋²³⁸U碰撞实验. 研究了在两种极端对撞方位的UU碰撞中, 末态核子和π介子椭圆流v₂与碰撞参数、快度以及横动量的依赖关系. 研究表明, 由于挤压(squeeze-out)效应, 末态核子和π具有负的椭圆流; 体-体UU中心碰撞事件具有最大初始坐标空间形变, 因而具有最大的负的椭圆流, 约12%; 在最小无偏事件样本下, 体-体和头-头碰撞, 中央快度平台上的核子椭圆流大小相当, 而前者π椭圆流略大于后者; 在中央快度平台, 低横动量核子和π主要由反应后期Δ衰变得到, 而高横动量主要是参与核子再散射生成, 因而在低横动量区它们具有相似的流, 而在较高横动量区(>0.3GeV/c)由于旁观核子的再散射和吸收效应, 它们的椭圆流有明显压低.     

Temperature dependence of photoluminescence from self-organized Ge quantum dots with large size and low density

Photoluminescence(PL) from self-organized Ge quantum dots(QDs) with large size and low density has been investigated over a temperature range from 10 to 300 K using continuous-wave(CW) optical excitation.The integrated PL intensity of QDs observed is negligible at about 10 K and rapidly increases with raising temperature up to 100 K.Through analyzing the PL experimental data of the QDs and wetting layer(WL),we provide direct evidence that there exists a potential barrier,arising from the greater compressive...     

Calculation of the Viscosity of Polymer Melts Based on Measurements of the Recovered Rubber-Like Deformation

On the basis of a model of polymer flow, considering the forces of entropic elasticity of extended macromolecules within the Eyring's concept, the relationships between the shear rate, shear stress, viscosity, and recovered rubber-like deformation were derived. The reduction of activation energy of the flow, by an amount proportional to the recovered rubber-like deformation, leads to an exponential decrease of viscosity with increasing shear rates; this nonlinear dependence of viscosity on shear rate (and shear stress) is defined as the viscosity anomaly of polymers. The measurement of deformation recovery after the cessation of polymer flow in the mode of constant shear rate or shear stress on a rotational viscometer confirmed the validity of the theoretical dependences.     

Energy and angular distributions of backscattered electrons from collisions of 5 keV electrons with thick Al,Ti, Ag,W and Pt targets

The energy and angular distributions of backscattered electrons produced under the impact of 5 keV electrons with thick Al, Ti, Ag, W and Pt targets are measured. The energy range of backscattered electrons is considered between E _B = 50 eV and 5000 eV. The angle of incidence α and take-off angle θ are chosen to have values α = 0 and 10 and θ = 100, 110 and 120 respectively. The measured energy spectra are compared with the available theoretical models for α = 0 and 10. The elastic peak intensity of backscattered electrons is found to be a function of angle of incidence, take-off angle and atomic number of the target material. The considered theories are reasonably in good agreement with experiment for the energy spectra of the backscattered electrons having their reduced energies ∈ (= E _B/E ₀) in the range of 0.20 to 1.00.      

CSR能区UU碰撞侧向流蒙特卡罗模拟与研究

应用ART模型研究了E_b=520MeV/u的UU碰撞. 探讨了在两种极端方位UU碰撞下, 核子和π在反应平面内的横向流的时间演化以及对碰撞中心度的依赖关系. 研究表明, 流在高密区域发展并且在膨胀相稳定, 因而它是高密区域反应动力学的一个敏感探针. 对头头和体体UU碰撞, 末态π相对于核子的横向流分别在大约b=9fm和b=2fm处存在明显的正向到负向的改变. π的这种行为是重子共振态和旁观者的遮蔽效应(再散射和再吸收)共同作用的结果.     

The effects of temperature on nanocrystalline diamond films deposited on WC-13 wt.% Co substrate with W-C gradient layer

A tungsten-carbide gradient coating (WCGC) was prepared by reactive sputtering as an intermediate layer on the cemented carbide, WC-13 wt.% Co, substrate to improve the nucleation, smoothness and adhesion of diamond film. The diamond film was deposited by hot filament chemical vapor deposition (HFCVD). The effects of the substrate temperature on the WCGC and the diamond film were investigated. The characterization of the WCGC and the diamond films was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), micro-Raman spectroscopy and Rockwell hardness indentation. It is found that the WCGC plays an important role in improving the nucleation, smoothness and adhesion of diamond film; and the diamond films exhibit better quality and adhesion as substrate temperature increases during the CVD processes.     

Mechanism of nucleophilic substitutions at phenacyl bromides with pyridines. A computational study of intermediate and transition state

DFT computations have been performed on nucleophilic substitutions of phenacyl bromides with pyridines to investigate the mechanism of the reaction. In contrast with earlier suppositions, tetrahedral intermediate is not formed by the addition of pyridine on the C?O group of phenacyl bromide, because the total energy of the reacting species increases continuously, when the distance between the N and C(?O) atoms of reactants is shorter than 2.7 Å. At a greater distance, however, a bridged complex of the reactants is observed, in which the N atom of pyridine is slightly closer to the C atom of the C?O, than to the C atom of the CH₂Br group of phenacyl bromide, the distances are 2.87 and 3.05 Å, respectively. The attractive forces between the oppositely polarized N and C(?O) atoms in the complex decrease the free energy of activation of the S_N2 attack of pyridine at the CH₂Br group. The calculated structural parameters of the S_N2 transition states (TS) indicate, that earlier TSs are formed when the pyridine nucleophile bears electron‐donating (e‐d) groups, while electron‐withdrawing (e‐w) groups on phenacyl bromide substrate increase the tightness of the TS. Free energies of activation computed for the S_N2 substitution agree well with the data calculated from the results of kinetic experiments and correlate with the σ_Py substituent constants, derived for pyridines, and with the Hammett σ constants, when the substituents (4‐MeO‐4‐NO₂) are varied on the pyridine or on the phenacyl bromide reactants. Copyright © 2008 John Wiley & Sons, Ltd.     

The Impact of Information Flow by Co-Shareholder Relationships on the Stock Returns: A Network Feature Perspective

One shareholder may invest in different listed energy companies, so the information held by common shareholders can be transmitted among companies. Based on the two-mode complex network method, we construct an information flow shareholder-based network and employ different network indicators representing features of information flow as variables to construct panel regression models to analyze the impact of information flow among listed energy companies on the stock returns. The results indicate that the information flow of listed energy companies are increasingly important and play a significant role over a period. The efficiency of information flow among listed energy companies is increasingly high and the network information is concentrated among a few of these companies. The efficiency of information flow and the independence of listed energy companies are significantly positively related to stock returns, while the listed energy companies’ ability to control information is not significantly related to stock returns. We employ a new perspective to analyze the information flow on how to influence stock returns, and offer some related suggestions for investors and policy makers in the future.     

The MACQM Calculation for the BInding Energy of the Equilateral Triangle Structure of H3^— Cluster

Considering that the equilateral triangle structure of H3^- cluster can be formed from the interaction of H^- with two hydrogen atoms,a modified arrangement channel quantum mechanics method has been used to calculate the total energy curve for this structure,The result shows that the cureve has a minimal energy-1.6672 a.u.at an internuclear distance of 1.77a0,so its dissociation energy(binding energy)is D(H^- H H)=0.1395,a.u.This means that the cluster H3^- may be formed in an equilateral triangle structure with a bond length of 1.77α0.     

高温超导电缆终端的研究与开发

简单介绍了高温超导电缆的终端的基本结构特点与作用等 ;并主要介绍了工业化国家中美国、日本、丹麦等所研制的 HTS电缆终端以及目前我们所研制的终端情况。     

CuⅠ-AsⅤ离子3d104s-3d94s4p跃迁组态的能级和振子强度

利用组态相互作用理论和参数拟合内插的方法计算了类铜ＣｕⅠ－ＡｓⅤ离子３ｄ１０４ｓ－３ｄ９４ｓ４ｐ跃迁组态的能级、谱线波长和电偶极跃迁的振子强度。３ｄ９４ｓ４ｐ组态能级的所有计算结果与现有实验数据符合得很好。而ＺｎⅡ和ＧａⅢ离子的大部分能级纯属预测计算结果。给出了３ｄ１０４ｓ－３ｄ９４ｓ４ｐ能级跃迁的谱线波长和振子强度。