Preliminary Investigation of Impurity and Radiation Behaviors in the Startup Phase of HL-2A Tokamak

As the startup phase of HL-2A operation and the first divertor tokamak device in China, it is important to identify the species of impurity, estimate the concentration of impurities and compare the different behaviors of radiation in limiter and divertor configurationt. In startup phase of HL-2A, glowing discharge cleaning （GDC） is used as a conventional wall conditioning technology and titanium gettering is used occasionally in closed divertor chamber during SN configuration discharges phase.     

Ultrasonic flow measurement and wall acoustic impedance effects

An examination of the influence of wall acoustic impedance effects on sound propagation in flowing liquids confined by cylindrical walls is presented. Special focus is given to the importance of the wall acoustic impedance value for ultrasonic flow meter performance. The mathematical model presented allows any radially-dependent axial flow profile to be examined in the linear flow acoustics regime where fluid flow speed is much smaller than the fluid sound speed everywhere in the fluid medium.     

Settling motion of interacting solid particles in the vicinity of a plane solid boundary

The sedimentation of $N?1$ small arbitrarily-shaped solid bodies near a solid plane is addressed by discarding inertial effects and using 6N boundary-integral equations. Numerical results for 2 or 3 identical spheres reveal that combined wall–particle and particle–particle interactions deeply depend on the cluster's geometry and distance to the wall and may even cancel for a sphere which then moves as it were isolated. To cite this article: A. Sellier, C. R. Mecanique 333 (2005).     

Gyrotron travelling wave amplifier: II. Effects of velocity spread and wall resistivity

The small signal gain and bandwidth of the gyrotron travelling-wave amplifier (gyro-TWA) operating at the fundamental cyclotron harmonic are examined. The analytical and numerical studies focus on the effects of velocity spread in the electron beam and of a distributed wall resistivity in the waveguide. It is found that wall resistivity reduces the forward gain of the amplifier only by an amount approximately equal to 1/3 of the corresponding cold tube loss. Significant increase in bandwidth may result, under certain conditions, from the presence of wall resistivity. A moderate amount (5–10%) of velocity spread does not reduce the peak gain significantly in general, but may reduce the bandwidth by an amount depending on the applied magnetic field. Based on considerations of such factors as power, stability, gain, bandwidth, and efficiency, operating parameters for the gyro-TWA are suggested.     

高分子混合物溶液在极稀浓度区的粘度异常行为

上世纪50年代初人们就发现,高分子溶液的粘度在极稀浓度区往往表现出异常行为,即当浓度低于某一特定值后,比浓增比粘度-浓度图偏离预计的线性关系,出现上弯或下弯的曲线.     

离分子混合物溶液在极稀浓度区的粘度异常行为

上世纪50年代初人们就发现,高分子溶液的粘度在极稀浓度区往往表现出异常行为,即当浓度低于某一特定值后,比浓增比粘度浓度图偏离预计的线性关系,出现上弯或下弯的曲线.几十年来人们对此现象展开了大量研究,提出了一些互不协同的解释[1,2].最近,程时等[3,4]对该问题作了系统深入的研究,指出这种粘度异常是源于粘度测量中高分子溶液与毛细管内壁间的界面作用,并给出了消除界面作用干扰的理论改正公式.至此,单一高分子溶液粘度的异常问题得到了明确的解释.但是,关于高分子混合物在极稀浓度区的粘度行为的研究就比较稀少.80年代Ｄｏｎｄｏｓ…     

Switching of transmission resonances in a two-channels coupler: A Boundary Wall Method scattering study

In this work, we study the transmission characteristics of a two-channels coupler model system using the Boundary Wall Method (BWM) to determine the solution of the corresponding scattering problem of an incident plane wave. We show that the BWM provides detailed information regarding the transmission resonances. In particular, we focus on the case of single channel input aiming to explore the energy switching performance of the coupler. We show that the coupler geometry can be tailored to allow for the first transmission resonances to be predominantly transmitted on specific output channels, an important characteristic for the realization of logical operations.     

Thermocapillary motion of a two-bubble cluster near a plane solid wall

The thermocapillary motion of two bubbles near a plane solid wall at uniform temperature is investigated by solving five boundary integral-equations. Preliminary computations show that wall–bubble interactions dictate the migration of equal bubbles with line of centers parallel to the wall. To cite this article: A. Sellier, C. R. Mecanique 333 (2005).     

Motion of a porous sphere in a spherical container

The creeping motion of a porous sphere at the instant it passes the center of a spherical container has been investigated. The Brinkman's model for the flow inside the porous sphere and the Stokes equation for the flow in the spherical container were used to study the motion. The stream function (and thus the velocity) and pressure (both for the flow inside the porous sphere and inside the spherical container) are calculated. The drag force experienced by the porous spherical particle and wall correction factor is determined. To cite this article: D. Srinivasacharya, C. R. Mecanique 333 (2005).     

Flow structure and wall layer control in a lower half heated upper half cooled enclosure with superimposed temperature deviations

This paper presents an investigation on the effects of superimposed temperature deviations as a control technique for the flows and mixing in lower half heated upper half cooled enclosures. Results show that the strength of the wall layer depends on the difference between the wall surface temperature and the fluid core temperature. The location of the head-on collision between a pair of upward/downward wall layers, which controls the mixing and fluid exchange between the two halves, is determined by the wall layer flow momentum strengths. Elevating/reducing the wall temperature by a superimposed temperature deviation is an effective control for the flow and mixing in such enclosures. Heat transfer analysis shows that the superimposed temperature deviations have minor effects on the total heat flow rate from the lower walls. Thus, this technique can be applied onto reactor vessels without modifying the reactor vessel configuration.