Effect of a Magnetic Field on a Micropolar Fluid Flow in the Vicinity of an Axisymmetric Stagnation Point on a Circular Cylinder

The effect of a magnetic field on a micropolar fluid flow in the vicinity of an axisymmetric stagnation point on a circular cylinder is studied numerically. The governing conservation equations of continuity, momentum and angular momentum are partial differential equations which are transformed into a system of ordinary differential equations by using the usual similarity transformations. The resulting system of coupled non‐linear ordinary differential equations is solved numerically by using the shooting method. The numerical results indicate the velocity, angular velocity and pressure distributions for different parameters of the problem including Reynolds number, magnetic parameter and dimensionless material properties, etc. In addition, the effect of the pertinent parameters on the local skin friction coefficient and the couple stress are discussed numerically and illustrated graphically.     

Charged polaron-enhanced circular dichroism of optically nonlinear 3-nitroaniline crystal

The circular dichroism (CD) spectra in visible range of the 3-nitroaniline (m-NA) single crystal, of its solution in chloroform, and in the KBr pellet were recorded. Neither the molecular (m or C_s) nor the crystal (mm2 or C_2v) point groups belong to the chiral groups. The DFT calculation of CD spectrum of the m-NA isolated neutral molecule confirmed its chirality. The red shifted bands in the calculated CD spectrum of m-NA radical anion (charged polaron), as compared with the neutral molecule, resemble better the spectra of solids than that of the solution. It seems that these facts corroborate qualitatively the “hop and turn” model explaining the m-NA optical nonlinearity and electric conductivity proposed in Szostak et al. [M.M. Szostak, H. Chojnacki, E. Staryga, M. D?u?niewski, G. B?k, Chem. Phys. 365 (2009) 44-52].     

A load–deformation formulation with fracture representation based on the J–R curve for tubular joints

This study presents a new fracture formulation to describe the ductile tearing and unstable fracture failure for circular hollow section (CHS) joints under monotonically increasing brace tension. The initiation of the ductile tearing occurs when the crack driving force in an assumed initial shallow crack reaches the material fracture toughness determined from a standard fracture toughness test. The joint behavior prior to the ductile crack initiation follows a previously proposed nonlinear formulation based on the latest strength equations recommended by the International Institute of Welding. The load–deformation characteristics beyond the crack initiation assume that the energy release rate and the amount of crack extension adhere to the experimentally measured J–R curve, prior to the unstable fracture failure. Unstable fracture, which leads to the total loss of the joint capacity, occurs when the crack driving force reaches the maximum fracture resistance determined from the J–R curve test. The proposed load–deformation representation for tubular joints, when implemented in the large-scale K-frame pushover analysis with a material fracture toughness test, predicts successfully the global frame response governed by the joint fracture failure, as observed in the frame test.     

国内外圆管带式输送机的新发展

简述了圆管带式输送机的原理、托辊结构、胶带合缝万法和其结构形式，并指出了其优缺点。同时还介绍了我国在克服日本国管带式输送机缺点的基础上而研制成功的新机型，最后列举了有关应用实例。     

提高刮板输送机圆环链与中部槽耐磨性的研究

通过试验室对不同热处理状态和硬度的摩擦副的筛选试验,找出了煤粉磨料条件下的刮板输送机中部槽摩擦副磨损与硬度的关系。提出了提高刮板输送机圆环链与中部槽耐磨性的途径     

A model based method for centering double ball bar test results preventing fictitious ovalization effects

The telescoping magnetic double ball bar (DBB) is widely used to assess the motion and link errors of machine tools through circular tests. Despite a careful setup, some slight eccentricity of the balls relative to the circular trajectory often remains. Removing the eccentricity from the DBB results is essential due to its effects on the estimated trajectory. However, if the centering is not performed with great care, a fictitious ovalization effect may appear in the processed data. The source of the fictitious ovalization is discussed in this paper and a method is proposed to quantify the eccentricity and adequately process the data so that the fictitious ovalization is avoided. The results obtained by applying the proposed method both in simulation and in practice demonstrate its effectiveness.     

Free convection performance of circular cavities having two active curved vertical sides and two inactive curved horizontal sides

A detailed review of the archival reveals that the heat transfer and fluid flow characteristics of circular cavities have not been investigated so far and of course their physical features are not understood. A prominent application of these cavities arises in the miniaturized packaging of electronic components that are subject to strict constraints. This paper addresses primarily steady-state laminar natural convection of air in a circular cavity of diameter H inscribed in a square cavity of side H where the corresponding sides are in contact at four points. A third cavity, an arc–square cavity whose shape lies between the square and circular cavity shapes is included in the analysis. The finite volume method is used to perform the numerical simulations. The methodology takes into account the second-order-accurate QUICK scheme for the discretization of the convective term, whereas the pressure–velocity coupling is handled with the SIMPLE scheme. Since the air is not assumed a Boussinesq gas, it was decided to take all thermophysical properties as temperature-dependent. In the end, it has been demonstrated that the circular cavity possesses a superior balance between heat transfer enhancement and size in cross-section area in comparison with the standard square cavity. The side of the square cavity is similar to the diameter of the circular cavity.     

静磁场下超导圆极化微带天线辐射性能研究

在液氦温度下，研究了工作频率为６．２６ＧＨｚ的Ｙ系超导圆极化微带天线的传输系数Ｓ２１及圆极化轴比随外加工磁场的变化，实验结果表明：在４．２Ｋ温度，外加磁场Ｂ≤１Ｔ时，其Ｓ２１及圆极化轴比基本不随外加磁场的变化而改变。     

FFT在TMS320C54x定点DSP中的高效实现方法

介绍了实FFT的快速高效的原理及实现方法，适用于所有基于TMS320C54 x定点DSP的实FFT的运算。     

圆形隧洞导流无压流时水力计算底坡快速判别方式的探讨

介绍了圆形隧洞导流时无压流的情况下水力计算底坡的快速判别方式.