Characterization of Glucokinase Catalysis from a Pseudo-Dimeric View

Applied Biochemistry and Biotechnology - Glucose phosphorylation by glucokinase exhibits a sigmoidal dependency on substrate concentration regardless of its simple structure. Dimorph mechanism...     

Experimental investigation of the flow around a radially vibrating circular cylinder

This work aims to develop a process for controlling a cylinder wake, especially the von Karman vortex street, in such way so as to drastically reduce the drag coefficient. A new technique for influencing the cylinder wake is proposed in the present experimental study. The flow around a circular cylinder is perturbed by temporarily changing the cylinder diameter. Experiments have been performed for Reynolds numbers in the range Re=9,500 to Re=31,500. Three values of the controlling frequencies are considered: fs₁=0.41, fs₂=0.54 and fs₃=0.73, in addition to the stationary case corresponding to a non-deformable cylinder, fs₀=0. The visualisation flow shows that the pulsing motion of the cylinder walls greatly influences both the near and far wake dynamics. A decrease of the drag is expected.

Combined effects of crucible geometry and Marangoni convection on silicon Czochralski crystal growth

In order to understand the influence of crucible geometry combined with natural convection and Marangoni convection on melt flow pattern, temperature and pressure fields in silicon Czochralski crystal growth process, a set of numerical simulations was conducted. We carry out calculation enable us to determine temperature, pressure and velocity fields in function of Grashof and Marangoni numbers. The essential results show that the hemispherical geometry of crucible seems to be adapted for the growth of a good quality crystal and the pressure field is strongly affected by natural and Marangoni convection and it is more sensitive than temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental investigation of a circular radially deforming cylinder near wake using an infrared technique

The present experimental study aims at developing a method to control the circular cylinder near wake by radial deformation and understand the underlying physics. Using an infra-red camera, we examine the temperature distribution of the near wake center line of a sinusoidal law radially deforming circular cylinder. From these measurements, the near wake is characterized by the length of the recirculation zone, the vortex formation zone length, the temperature fluctuation maximum intensity and the vortex street shedding frequency. For several deformations frequencies, we study the radial deformation influence on the near wake characteristics. It is noted that the wake structure is strongly affected by the deformation frequency. Among other things, we note the recirculation zone length reduction and the vortex formation zone length reduction when the radial vibrations are close to the “Lock-in” fundamental range. It is also noted that the variations of the vortex shedding frequency depend on the deformation frequency.     

Interaction between the near wake and the cross-section variation of a circular cylinder in uniform flow

The flow around a circular cylinder with a cross-section variation is experimentally investigated. Particle Image Velocimetry (PIV) is used to scrutinize the interaction of the cylinder’s wall with its near wake. The Reynolds number based on the cylinder’s diameter and freestream velocity is 80 × 10³, corresponding to the upper subcritical flow regime. At a forcing Strouhal number of St _f = 0.02, the maximum vorticity level around the cylinder is reduced by more than 50% as compared to its uncontrolled value. The topology of the bulk flow confined between the primary vortical structure and the cylinder surface is modified resulting in substantial drag reduction.     

纯弯曲矩形截面梁Ⅰ型单边裂纹端部的应力应变场及裂纹失稳扩展临界应力的计算

本文应用文[1]的分析方法,研究了纯弯曲矩形载面梁Ⅰ型单边裂纹端部的应力应变场,给出了裂纹尖端的应力应变分量和计算裂纹端部弹性变形区和变形强化区宽度的公式以及计算裂纹失稳扩展临界应力的方程组。最后用计算实例对裂纹失稳扩展临界应力方程组进行了验证,最大误差不超过0.18%.     

Point-to-point trajectory planning of wheeled mobile manipulators with stability constraint. Extension of the random-profile approach

We propose a flexible stochastic scheme for point-to-point trajectory planning of nonholonomic wheeled mobile manipulators subjected to move in a structured workspace. The problem is known to be complex, particularly if obstacles are present and if dynamic stability constraint is considered. The proposed method consists of extending to wheeled mobile manipulators the random-profile approach recently applied to wheeled platforms. This versatile method handles constraints on: (i) geometry (obstacle avoidance, bounded joint positions and path curvature); (ii) kinematics (bounded velocities and accelerations); (iii) dynamics (bounded torques, stability condition). It may be applied using various forms of cost functions involving travel time, efforts and power. Solutions are presented for planar and spatial nonholonomic wheeled mobile manipulators undertaking, in a constrained workspace, a point-to-point task defined either in generalized or operational coordinates.     

Stress-strain field near crack tip and calculation of critical stress of crack propagation in a pure bending beam of rectangular section with one-sided mode i crack

This paper studies the stress-strain field near crack tip in a pure bending beam of rectangular section with one-sided mode I crack by the analytic method of Ref. [1], then it gives the stress and strain components at the crack tip when the crack propagates and further it obtains the formulas of calculating the elastic deformed area width, the deformed intensity area width and the equation groups of calculating the critical stress of crack propagation, last the equation group of calculating critical stress of crack propagation is verified by calculating instance. The maximum error is 0.18%. First Received May 7, 1994.     

Numerical simulation and experimental visualization of the influence of the deformation frequency of a radially deforming circular cylinder impulsively started on cylinder wake

A periodic superimposed motion may notably influence the flow structure and the development of the convective heat transfer relative to non‐deformable case. In particular, a radial deformation of a circular cylinder, may cause a possible synchronization with the cylinder wake, which is itself periodic when Vortex Street takes place. This synchronization phenomenon, often called ‘lock‐in’, may cause undesirable effects, but may also constitute a way of controlling the wake development. Body deformability may be used as wake control device that would favourably affect the interplay of primary and secondary vorticities, thus reducing the drag coefficient. These numerical and experimental studies are done herein for a Reynolds number equal to 23500. The problem is resolved by using the Navier–Stokes equations in the vorticity‐stream function form. The vorticity transport equation is solved by a second‐order finite difference method in both directions of the domains. The Poisson equation for the stream‐function is solved by a SOR method. The advance in time is achieved by a second‐order Adams–Bashforth scheme. The effect of turbulence is represented by eddy viscosity ν_t, which is determined by a sub‐grid‐scale model. In the present study, we use a Smagorinsky model. Copyright © 2003 John Wiley & Sons, Ltd.     

Efficiency of an auto-propelled flapping airfoil

The present study deals with an investigation of the flow aerodynamic characteristics and the propulsive velocity of a system equipped with a nature inspired propulsion system. In particular, the study is aimed at studying the effect of the flapping frequency on the flow behavior. We consider a NACA0014 airfoil undergoing a vertical sinusoidal flapping motion. In contrast to nearly all previous studies in the literature, the present work does not impose any velocity on the inlet flow. During each iteration the outer flow velocity is computed after having determined the forces exerted on the airfoil. Forward motion may only be produced by flapping motion of the airfoil. This is more consistent with the physical phenomenon. The non-stationary viscous flow around the flapping airfoil is simulated using Ansys-Fluent 12.0.7. The airfoil movement is achieved using the deformable mesh technique and an in-house developed User Define Function (UDF). Our results show the influence of flapping frequency and amplitude on both the airfoil velocity and the propulsive efficiency. The resulting motion is contrasts to the applied forces. In the present study, the frequency ranges from 0.1 to 20 Hz while the airfoil amplitude values considered are: 10%, 17.5%, 25% and 40%.