Simulation and crystal growth of CdTe by axial vibration control technique in Bridgman configuration

Abstract This paper presents a numerical study in which active and hybrid vibration confinement is compared with a conventional active vibration control method. Vibration confinement is a vibration control technique that is based on reshaping structural modes to produce “quiet areas” in a structure as opposed to adding damping as in conventional active or passive methods. In this paper, active and hybrid confinement is achieved in a flexible beam with two pairs of piezoelectric actuators and sensors and with two vibration absorbers. For comparison purposes, active damping is achieved also with two pairs of piezoelectric actuators and sensors using direct velocity feedback. The results show that both approaches are effective in controlling vibrations in the targeted area of the beam, with direct velocity feedback being slightly more cost effective in terms of required power. When combined with passive confinement, however, each method is improved with a significant reduction in required power.

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Active vibration control of a rotor-bearing-actuator system using robust eigenvalue placement method

Measurement and Control ◽

10.1177/0020294019836125 ◽

2020 ◽

Vol 53 (3-4) ◽

pp. 531-540

Author(s):

Tao Lai ◽

Junfeng Liu

Keyword(s):

Vibration Control ◽

Condition Number ◽

Active Vibration Control ◽

State Equation ◽

Control Technique ◽

Precise Position ◽

Placement Method ◽

Rotor Bearing ◽

Actuator System ◽

Active Vibration

In order to improve the vibration responses of rotor system, this paper presents an active vibration control technique for a rotor-bearing-actuator system with the use of robust eigenvalue placement method. By analyzing the characteristics of the piezoelectric stack actuator, bearing and rotor, a rotor-bearing-actuator system is modeled. Based on this dynamical model, a reduced-order technique is used to establish the state equation in the modal space. A robust eigenvalue placement method, which can enhance the robustness of system to model error and uncertain factors by optimizing the close-loop eigenmatrix with a small condition number, is proposed to carry out the active vibration control for system. The good results indicate that the eigenvalue can be placed to precise position, and the displacement responses get effectively suppressed with the proposed method. Meanwhile, the optimized close-loop eigenmatrix can possess a small condition number, which means the system has achieved excellent robustness.

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Effect of Marangoni Convection on InSb Single Crystal Growth by Horizontal Bridgman Method

MRS Proceedings ◽

10.1557/proc-692-h8.6.1 ◽

2001 ◽

Vol 692 ◽

Author(s):

K. Kodera ◽

A. Kinoshita ◽

K. Arafune ◽

Y. Nakae ◽

A. Hirata

Keyword(s):

Crystal Growth ◽

Binary System ◽

Temperature Gradient ◽

Single Crystal ◽

Grown Crystal ◽

Marangoni Convection ◽

Single Crystal Growth ◽

Control Technique ◽

Growth System

AbstractIt is necessary to clarify the effect of Marangoni convection on single crystal growth from a melt in order to improve the quality of the grown crystal. Particularly, the deviation of crystalmelt (C-M) interface from a planar shape is a major problem because it may deteriorate the quality of the grown crystal. In this paper, we investigated the effect of thermal and solutal Marangoni convection on C-M interface shape in an In-Sb binary system by the horizontal Bridgman (HB) method. The C-M interface concavity strongly depends on the cooling rate and the temperature gradient under uniform concentration distribution conditions in the melt. A large concavity was observed at low cooling rates and high temperature gradient conditions. The concavity was found to be caused by thermal Marangoni convection, by taking Péclet number into account. Then, we varied the composition of the In-Sb binary system to induce solutal Marangoni convection intentionally. The C-M interface was kept planar in case solutal Marangoni convection occurred in the direction opposite to the thermal one. Therefore, we believe that the utilization of solutal Marangoni convection will be a new control technique to make the C-M interface planar for the HB system. From these results, it was clarified that Marangoni convection plays a significant role in the HB crystal growth system.

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Characteristics and Elimination of Vibration Transfer on Small- and Medium-Sized Turbo Generators

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.318.120 ◽

2013 ◽

Vol 318 ◽

pp. 120-124

Author(s):

Rong Pei Zhang ◽

Sheng Yang Lu

Keyword(s):

Vibration Control ◽

Stable Operation ◽

Axial Vibration ◽

Large Capacity ◽

Horizontal Vibration ◽

Vibration Transmission ◽

Diagnostic Practices ◽

Transfer Characteristics ◽

Rotating Machineries

Vibration control is important for the safe and stable operation of generator units. The vibration transfer characteristics of small- and medium-sized turbo generators are different from those of large capacity units due to differences in mechanical structures. We point out that the vibration on small- and medium-sized turbo generators propagates through their foundation from one bearing to another, rather than through the shafting. In particular, transmission of horizontal vibration measured on bearings is found to be more significant compared with vertical and axial vibration due to the height of the bearing pedestal. We demonstrate through three successful diagnostic practices the process of vibration transmission on small and medium-sized turbo generators. The present work can serve as a reference for the same type of unit as well as other similarly structured rotating machineries.

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