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1,171 results on '"CHANG, C. W."'

326. Metronomic gemcitabine suppresses tumour growth, improves perfusion, and reduces hypoxia in human pancreatic ductal adenocarcinoma

Author

Cham, K K Y, primary, Baker, J H E, additional, Takhar, K S, additional, Flexman, J A, additional, Wong, M Q, additional, Owen, D A, additional, Yung, A, additional, Kozlowski, P, additional, Reinsberg, S A, additional, Chu, E M, additional, Chang, C-W A, additional, Buczkowski, A K, additional, Chung, S W, additional, Scudamore, C H, additional, Minchinton, A I, additional, Yapp, D T T, additional, and Ng, S S W, additional

Published
2010
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344. The Development of Advanced Materials - High Performance Properties of Composite for Automotive and Aerospace Applications

Author

Idris, Jamaliah, Tan, J. C., Chang, C. W., Idris, Jamaliah, Tan, J. C., and Chang, C. W.

Abstract

Magnesium metal matrix composite (MMC) is an excellent candidate for moving engine components and airframes due to its low density. Magnesium's lightweight and natural affinity for wetting to ceramic particle reinforcements such as silicon carbide (SiC) make it one of the best choices as a matrix metal. However, magnesium alone without reinforcement is not suitable for mechanical applications due to its low wear resistance performance. The magnesium matrix composites used in this study were produced by powder metallurgy technique. The wear resistance of SiC/AZ91 composite reinforced with 0, 5, 10, 15 and 20 wt.% SiC were studied. Pin-<>n-disk dry sliding wear tests were carried out to study the volumetric wear, wear rate and wear mechanisms. The magnesium matrix composites were used as pins while the counter face consisted of mild steel disks. Worn surfaces of pins and the wear debris were investigated by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX). The wear resistance performance of magnesium matrix composites was found to improve with increasing volume fraction of SiC. Volumetric wear was found to increase with sliding distance and the wear rate was greatly reduced after the wear-in phenomenon. For AZ91 Mg-SiCp/ steel dry sliding wear system, 2D-wt.% SiC/AZ91 magnesium composite was found to have the best wear resistant performance. During the wear-in period, abrasion was predominant during the wear-in stage. In the corrosion study, corrosion behavior of Mgbased metal matrix composites SiC particulate reinforced AZ91 (SiC/AZ91) with reinforcement weight fraction of 5, 10, 15 and 20 wt.% as well as the monolithic AZ91 alloy was studied. The galvanic effect of SiC reinforcement on the matrix alloy was also investigated. The studies were carried out under temperature of 30° ± 1°C and pH 7 in aerated 0.1 M NaCI solution. The materials were studied by using electrochemical corrosion test, weight-loss measurement of corrosion rate

Published
2001

345. On trajectory generation for flexible space crane: Inverse dynamics analysis by LATDYN

Author

Chen, G.-S, Housner, J. M, Wu, S.-C, and Chang, C.-W

Subjects
Mechanical Engineering
Abstract

For future in-space construction facility, one or more space cranes capable of manipulating and positioning large and massive spacecraft components will be needed. Inverse dynamics was extensively studied as a basis for trajectory generation and control of robot manipulators. The focus here is on trajectory generation in the gross-motion phase of space crane operation. Inverse dynamics of the flexible crane body is much more complex and intricate as compared with rigid robot link. To model and solve the space crane's inverse dynamics problem, LATDYN program which employs a three-dimensional finite element formulation for the multibody truss-type structures will be used. The formulation is oriented toward a joint dominated structure which is suitable for the proposed space crane concept. To track a planned trajectory, procedures will be developed to obtain the actuation profile and dynamics envelope which are pertinent to the design and performance requirements of the space crane concept.

Published
1989

346. Controlled multibody dynamics simulation for large space structures

Author

Housner, J. M, Wu, S. C, and Chang, C. W

Subjects
Spacecraft Design, Testing And Performance
Abstract

Multibody dynamics discipline, and dynamic simulation in control structure interaction (CSI) design are discussed. The use, capabilities, and architecture of the Large Angle Transient Dynamics (LATDYN) code as a simulation tool are explained. A generic joint body with various types of hinge connections; finite element and element coordinate systems; results of a flexible beam spin-up on a plane; mini-mast deployment; space crane and robotic slewing manipulations; a potential CSI test article; and multibody benchmark experiments are also described.

Published
1989

347. Connection forces in deformable multibody dynamics

Author

Shabana, A. A and Chang, C. W

Subjects
Structural Mechanics
Abstract

In the dynamic formulation of holonomic and nonholonomic systems based on D'Alembert-Lagrange equation, the forces of constraints are maintained in the dynamic equations by introducing auxiliary variables, called Lagrange multipliers. This approach introduces a set of generalized reaction forces associated with the system generalized coordinates. Different sets of variables can be used as generalized coordinates and accordingly, the generalized reactions associated with these generalized coordinates may not be the actual reaction forces at the joints. In rigid body dynamics, the generalized reaction forces and the actual reaction forces at the joints represent equipollent systems of forces since they produce the same total forces and moments at and about any point on the rigid body. This is not, however, the case in deformable body analyses wherein the generalized reaction forces depend on the system generalized reference and elastic coordinates. In this paper, a method for determining the actual reaction forces at the joints from the generalized reaction forces in deformable multibody systems is presented.

Published
1989
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348. A finite element method for time varying geometry in multibody structures

Author

Housner, J. M, Wu, S. C, and Chang, C. W

Subjects
Cybernetics
Abstract

A three-dimensional finite element formulation using convected coordinates is presented for the multibody dynamics of truss-like configurations. Unlike existing formulations, the present one does not superimpose nonlinear rigid body kinematics with linear structural mode shapes, an approach that has recently been shown to be grossly inaccurate under certain conditions. Instead, the finite element method is extended to treat large motions/deformations. The formulation is oriented toward joint dominated structures and places the generalized coordinates at the joints. For the planar spin-up of a flexible beam, results are compared with those derived from a commercially available computer program. The two programs predict nearly identical results.

Published
1988

349. Producing Low-Oxygen Samarium/Cobalt Magnet Alloy

Author

Das, Dilip K, Kumar, Kaplesh, Frost, Robert T, and Chang, C. W

Subjects
Materials
Abstract

Experiments aimed at producing SmCo5 alloy with low oxygen contamination described in report. Two methods of alloying by melting without contact with crucible walls tested. Lowest oxygen contamination, 70 parts per million achieved by dc arc melting on water-cooled, tantalum-clad copper hearth in purified quiescent argon atmosphere. Report includes photographs of equipment, photomicrographs of alloy samples, detailed descriptions of procedures tried, and tables of oxygen contamination and intrinsic coercivities of samples produced.

Published
1987

350. Ultimate intrinsic coercivity samarian-cobalt magnet. An Earth based feasibility study for Space Shuttle missions

Author

Das, D, Kumar, K, Frost, R. T, and Chang, C. W

Subjects
Metallic Materials
Abstract

Techniques for the electromagnetic containerless reaction of samarium with cobalt for the formation of samarium-cobalt alloys are summarized. The effort expended to reduce and instrument the oxygen partial pressure in the reaction chamber and coolant gas system are described as well as the experiments in which these improvements were shown to be partially effective. A stainless steel glove box capable of being evacuated to low 10 to the -6th torr pressure and refilled with ultra-pure argon was built and installed. Necessary accessories to perform SmCo5 powder preparation, compaction and subsequent encapsulation of the powder inside a hot isostatic pressing cannister were designed, built, and incorporated into the chamber. All accessories were tested for proper functioning inside the chamber. Using the facility, the first batch of densified SmCo5 powder was fabricated to near total density. Analysis of the densified compacts shows that oxygen contamination during fabrication was near zero.

Published
1982

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