Magneto - Transport of electron symmetric and antisymmrtric states in highly doped InGaAs/InAlAs single quantum well

Beating patterns in longitudinal resistance caused by the symmetric and antisymmetric states were observed in a heavily doped InGaAs/InAlAs quantum well by using variable temperature Hall measurement. The energy gap of symmetric and antisymmetric states is estimated to be 4meV from the analysis of beating node positions. In addition, the temperature dependences of the subband electron mobility and concentration were also studied from the mobility spectrum and multicarrier fitting procedure.

Lamella reorientation in thin films of a symmetric poly(L-lactic acid)-block-polystyrene upon crystallization at different temperatures

The thin films of a symmetric crystalline-coil diblock copolymer of poly(L-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (T-g(PLLA)), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (T-c), the glass transition temperature of PS (T-g(PS)), the peak melting point of PLLA crystals (T-m(PLLA)), and the end melting point of PLLA crystals (T-m,end(PLLA)). When annealed at (T-c =) 80 degrees C (T-c < T-g(PS) < T-ODT, order-disorder transition temperature), 123 degrees C (T-g(PS) < T-c < T-m(PLLA) < T-ODT). 165 degrees C (T-g(PS) < T-m(PLLA) < T-c < T-m,end(PLLA) < T-ODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced.

Steady Patterns of Microparticles Formed by Optical Tweezers

In this paper, we propose a method for forming steady patterns of microparticles in a dispersion using optical tweezers. We demonstrate how to control the congregation of particles in a dispersion and to manually fabricate a pattern, The steady pattern (nay be useful for in-depth research, and the method will have applications in biology and nanotechnology.

Abel Inversion of Axially-Symmetric Shock Wave Flows

Finite-fringe interferograms produced for axisymmetric shock wave flows are analyzed by Fourier transform fringe analysis and an Abel inversion method to produce density field data for the validation of numerical models. For the Abel inversion process, we use basis functions to model phase data from axially-symmetric shock wave structure. Steady and unsteady flow problems are studied, and compared with numerical simulations. Good agreement between theoretical and experimental results is obtained when one set of basis functions is used during the inversion process, but the shock front is smeared when another is used. This is because each function in the second set of basis functions is infinitely differentiable, making them poorly-suited to the modelling of a step function as is required in the representation of a shock wave.

Study on Flow Patterns of Oscillatory Thermocapillary Convection In Floating Half Zone by PIV

The velocity fields of oscillatory convection have been measured using the techniques of Particle Image Velocimetry (PIV) in a liquid bridge of half floating zone with small typical scales of a few millimeters for emphasizing the thermocapillary effect in comparison with the effect of buoyancy. The flow patterns of the oscillatory flow have been studied experimentally in a liquid bridge. The flow patterns in the liquid bridge are classified with mode numbers according to oscillatory flow characteristics. Results of the experiment show that the mode depends on the aspect ratio as well as the volume ratio of the liquid bridge. The experimental results are helpful for studying the structure of flow at the onset of oscillatory thermocapillary convection in a liquid bridge.

Experimental study on two-phase gas-liquid flow patterns at normal and reduced gravity conditions

Experimental studies have been performed for horizontal two-phase air-water flows at normal and reduced gravity conditions in a square cross-section channel. The experiments at reduced gravity are conducted on board the Russian IL-76 reduced gravity airplane. Four flow patterns, namely bubble, slug, slug-annular transition and annular flows, are observed depending on the liquid and gas superficial velocities at both conditions. Semi-theoretical Weber number model is developed to include the shape influence on the slug-annular transition. It is shown that its prediction is in reasonable agreement with the experimental slug-annular transition under both conditions. For the case of two-phase gas-liquid flow with large value of the Froude number, the drift-flux model can predict well the observed boundary between bubble and slug flows.

Microgravity experiments of two-phase flow patterns aboard Mir Space Station

A first experimental study on two-phase how patterns at a long-term, steady microgravity condition was conducted on board the Russian Space Station "MIR" in August 1999. Carbogal and air are used as the liquid and the gas phase, respectively. Bubble, slug, slug-annular transitional, and annular hows are observed. A new region of annular how with lower liquid superficial velocity is discovered, and the region of the slug-annular transitional flow is wider than that observed by experiments on board the parabolic aircraft. The main patterns are bubble, slug-annular transitional and annular flows based on the experiments on board MIR space station. Some influences on the two-phase how patterns in the present experiments are discussed.

Two-phase flow patterns in a 90 degrees bend at microgravity

Bends are widely used in pipelines carrying single- and two-phase fluids in both ground and space applications. In particular, they play more important role in space applications due to the extreme spatial constraints. In the present study, a set of experimental data of two-phase flow patterns and their transitions in a 90degrees bend with inner diameter of 12.7 mm. and curvature radius of 76.5 mm at microgravity conditions are reported. Gas and liquid superficial velocities are found to range from (1.0 similar to 23.6) m/s for gas and (0.09 similar to 0.5) m/s for liquid, respectively. Three major flow patterns, namely slug, slug-annular transitional, and annular flows, are observed in this study. Focusing on the differences between flow patterns in bends and their counterparts in straight pipes, detailed analyses of their characteristics are made. The transitions between adjoining flow patterns are found to be more or less the same as those in straight pipes, and can be predicted using Weber number models satisfactorily. The reasons for such agreement are carefully examined.

Wavelike patterns in one-dimensional coupled map lattices

We investigate the existence of wavelike solution for the logistic coupled map lattices for which the spatiotemporal periodic patterns can be predicted by a simple two-dimensional mapping. The existence of such wavelike solutions is proved by the implicit function theorem with constraints. We also examine the stabilities of these wave solutions under perturbations of uniform small deformation type. We show that in some specific cases these perturbations are completely general. The technique used in this paper is also applicable to investigate other space-time regular patterns.

Numerical investigation on a simulation model of floating zone convection

A simulation model with adiabatic condition at the upper rod and constant temperature at the lower rod is studied numerically in this paper. The temperature distribution in a simulation model is closer to the one in the half part of a floating full zone in comparison with the one in a usual floating half zone model with constant temperature at both rods, because the temperature distribution of a floating full zone is symmetric for the middle plane in a microgravity environment. The results of the simulation model show that the temperature profiles and the how patterns are different from those of the usual floating half zone model. Another type of half zone model, with a special non-uniform temperature distribution at the upper rod and constant temperature at the lower rod, has been suggested by recent experiments. The temperature boundary condition of the upper rod has a maximum value in the center and a lower value near the free surface. This modified simulation model is also simulated numerically in the present paper. Copyright (C)1996 Elsevier Science Ltd.

Measurements of Flow Patterns and Velocities of Gas -Water Two -Phase Flows Using Electrical Resistance Imaging

This paper presents a measurement of flow patterns and flow velocities of gas-water two-phase flows based on the technique of electrical resistance tomography (ERT) in a 40m horizontal flow loop. A single-plane and dual-plane ERT sensor on conductive ring technique were used to gather sufficient information for the implementation of flow characteristics particularly flow pattern recognition and air cavity velocity measurement. A fast data collection strategy was applied to the dual-plane ERT sensor and an iterative algorithm was used for image reconstruction. Results, in respect to flow patterns and velocity maps, are reported.

Physical Modeling And Parametric Study On Two-Degree-Of-Freedom Viv Of A Cylinder Near Rigid Wall

Unlike most previous studies on the transverse vortex-induced vibration(VIV) of a cylinder mainly under the wallfree condition (Williamson & Govardhan,2004),this paper experimentally investigates the vortex-induced vibration of a cylinder with two degrees of freedom near a rigid wall exposed to steady flow.The amplitude and frequency responses of the cylinder are discussed.The lee wake flow patterns of the cylinder undergoing VIV were visualized by employing the hydrogen bubble technique.The effects of the gap-to-diameter ratio (e0/D) and the mass ratio on the vibration amplitude and frequency are analyzed.Comparisons of VIV response of the cylinder are made between one degree (only transverse) and two degrees of freedom (streamwise and transverse) and those between the present study and previous ones.The experimental observation indicates that there are two types of streamwise vibration,i.e.the first streamwise vibration (FSV) with small amplitude and the second streamwise vibration (SSV) which coexists with transverse vibration.The vortex shedding pattem for the FSV is approximately symmetric and that for the SSV is alternate.The first streamwise vibration tends to disappear with the decrease of e0/D.For the case of large gap-to-diameter ratios (e.g.e0/D = 0.54～1.58),the maximum amplitudes of the second streamwise vibration and transverse one increase with the increasing gapto-diameter ratio.But for the case of small gap-to-diameter ratios (e.g.e0/D = 0.16,0.23),the vibration amplitude of the cylinder increases slowly at the initial stage (i.e.at small reduced velocity V,),and across the maximum amplitude it decreases quickly at the last stage (i.e.at large Vr).Within the range ofthe examined small mass ratio (m＜4),both streamwise and transverse vibration amplitude of the cylinder decrease with the increase of mass ratio for the fixed value of V,.The vibration range (in terms of Vr ) tends to widen with the decrease of the mass ratio.In the second streamwise vibration region,the vibration frequency of the cylinder with a small mass ratio (e.g.mx = 1.44) undergoes a jump at a certain Vr,.The maximum amplitudes of the transverse vibration for two-degree-of-freedom case is larger than that for one-degree-of-freedom case,but the transverse vibration frequency of the cylinder with two degrees of freedom is lower than that with one degree of freedom (transverse).

Conical Emission Patterns by Femtosecond Pulses with Different Spectral Bandwidths

Different conical emission (CE) patterns are obtained experimentally at various incident powers and beam sizes of pump laser pulses with pulse durations of 7 fs, 44 fs and 100 fs. The results show that it is the incident power but not the incident power density that determines a certain CE pattern. In addition, the critical powers for similar CE patterns are nearly the same for the laser pulses with the same spectral bandwidth. Furthermore, as far as a certain CE pattern is concerned, the wider the spectral bandwidth of pump laser pulse is, the higher the critical power is. This will hopefully provide new insights for the generation of CE pattern in optical medium.

Measurement of two-photon excitation cross-section of a new symmetric-type fluorene derivative

A new dye, 2,7-bis(4-methoxystyryl)-9,9-bis(2-ethylhexyl)-9H-fluorene, has been synthesized, which is a D-pi-D symmetrical-type fluorene derivative. The two-photon absorption (TPA) of this new dye has been experimentally studied by comparable two-photon-induced fluorescence method. This new dye has a TPA cross-section of 84 x 10(-50) cm(4) s/photon at 790 nm/13 fs. (c) 2004 Elsevier GmbH. All rights reserved.