A quantitative comparison of load balancing approaches in distributed object computing systems

Several load balancing schemes are recently proposed for distributed object computing systems, which are widely envisioned to be the desired distributed software development paradigm due to the higher modularity and the capability of handling machine and operating system heterogeneity. However, while the rationales and mechanisms employed are dramatically different, the relative strengths and weaknesses of these approaches are unknown, making it difficult for a practitioner to choose an appropriate approach for the problem at hand. In this paper, we describe in detail three representative approaches, which are all practicable, and present a quantitative comparison using our experimental distributed object computing platform. Among these three approaches, namely, JavaSpaces based, request redirection based, and fuzzy decision based, we find that the fuzzy decision based algorithm outperforms the other two considerably.published_or_final_versio

Elasto-plastic analysis of reinforced concrete slit shear walls

This paper deals with the elasto-plastic behaviour of reinforced concrete slit shear walls, a new type of earthquake-resistant wall structure. The softened truss model was used to analyse the inelastic behaviour of the connecting beams, which are the key vibration-control devices of the structure. Based on the non-linear load-deflection curves of the connecting beams obtained using the softened truss model, the elasto-plastic behaviour of the slit shear wall structure as a whole was evaluated using a non-linear finite-element method. A parametric study was then carried out to investigate the effects of different connecting-beam designs on the performance of slit shear walls. The results reveal that the depth and reinforcement of the connecting beams directly affect the failure mode and ductility of the slit shear wall structure. It is concluded that, with appropriate design, the conversion of a solid shear wall into a slit shear wall can substantially increase the ductility of the wall structure, but there will be a slight reduction in lateral strength. | This paper deals with the elasto-plastic behaviour of reinforced concrete slit shear walls, a new type of earthquake-resistant wall structure. The softened truss model was used to analyze the inelastic behaviour of the connecting beams, which are the key vibration-control devices of the structure. Based on the non-linear load-deflection curves of the connecting beams obtained using the softened truss model, the elasto-plastic behaviour of the slit shear wall structure as a whole was evaluated using a non-linear finite-element method. A parametric study was then carded out to investigate the effects of different connecting-beam designs on the performance of slit shear walls. The results reveal that the depth and reinforcement of the connecting beams directly affect the failure mode and ductility of the slit shear wall structure. It is concluded that, with appropriate design, the conversion of a solid shear wall into a slit shear wall can substantially increase the ductility of the wall structure, but there will be a slight reduction in lateral strength.published_or_final_versio

Finite element model with continuous transverse shear stress for composite laminates in cylindrical bending

In the double superposition hypothesis, the global inplane displacement, which applies to the whole laminate, is enriched by local displacements which are restricted to each individual ply. To avoid the number of d.o.f.s growing with the number of plies, the transverse shear stress continuity is enforced as usual whereas the inplane displacement continuity is "doubly" constrained for two different groups of the local displacement. Based on the hypothesis, a two-node beam element is attempted. The element has the deflection and its derivative as its nodal d.o.f.s. Despite the fact that interpolated deflection is a cubic function of the longitudinal coordinate, the element yields poor accuracy. The cause is sorted out to be an algebraic constraint in the transverse shear. To overcome the constraint, a heterosis node is added. Remarkable improvement of the element accuracy is noted. © 1998 Elsevier Science B.V. All rights reserved.postprin

Cyclic behaviour of connecting beams in reinforced concrete slit shear walls

The connecting beams in slit shear walls are generally much shorter than those in ordinary coupled shear walls and may therefore behave quite differently. In order to investigate the shear behaviour of such short connecting beams, two series of shear tests, one on monotonic behaviour and the other on cyclic behaviour, were carried out. Altogether, 24 specimens were tested. The results of the monotonic shear tests have been reported in an earlier paper. This Paper presents some additional information on the ductility of the beams as revealed by the monotonic shear tests, and the results of the cyclic shear tests. From the cyclic shear tests, the cracking and failure characteristics, reinforcement stress distribution, stiffness and strength degradations, ductility and damping capacity, etc., of the connecting beams are studied. The results are useful for evaluating the seismic performance of reinforced concrete slit shear walls.published_or_final_versio

Elasto-plastic analysis of reinforced concrete slit shear walls

This paper deals with the elasto-plastic behaviour of reinforced concrete slit shear walls, a new type of earthquake-resistant wall structure. The softened truss model was used to analyse the inelastic behaviour of the connecting beams, which are the key vibration-control devices of the structure. Based on the non-linear load-deflection curves of the connecting beams obtained using the softened truss model, the elasto-plastic behaviour of the slit shear wall structure as a whole was evaluated using a non-linear finite-element method. A parametric study was then carried out to investigate the effects of different connecting-beam designs on the performance of slit shear walls. The results reveal that the depth and reinforcement of the connecting beams directly affect the failure mode and ductility of the slit shear wall structure. It is concluded that, with appropriate design, the conversion of a solid shear wall into a slit shear wall can substantially increase the ductility of the wall structure, but there will be a slight reduction in lateral strength. | This paper deals with the elasto-plastic behaviour of reinforced concrete slit shear walls, a new type of earthquake-resistant wall structure. The softened truss model was used to analyze the inelastic behaviour of the connecting beams, which are the key vibration-control devices of the structure. Based on the non-linear load-deflection curves of the connecting beams obtained using the softened truss model, the elasto-plastic behaviour of the slit shear wall structure as a whole was evaluated using a non-linear finite-element method. A parametric study was then carded out to investigate the effects of different connecting-beam designs on the performance of slit shear walls. The results reveal that the depth and reinforcement of the connecting beams directly affect the failure mode and ductility of the slit shear wall structure. It is concluded that, with appropriate design, the conversion of a solid shear wall into a slit shear wall can substantially increase the ductility of the wall structure, but there will be a slight reduction in lateral strength.published_or_final_versio

Service load analysis of unbonded partially prestressed concrete members

In the design of unbonded partially prestressed concrete (UPPC) members, it is necessary to estimate the stresses in steel and concrete in order to satisfy the requirements of the serviceability limit state. A numerical method has been developed to predict the response of UPPC beams under service load, and the results agree well with experimental results reported in the technical literature. A parametric study has been undertaken to evaluate the variation of stress in prestressed steel under service load as well as the ratio of length of equivalent deformation region to the neutral axis depth at critical section. Results show that this ratio is not sensitive to the variation of the combined reinforcement index. From the moment of application of load to the cracking of the beam, and until the yielding of non-prestressed steel, this ratio is fairly stable and it can be taken as a constant. With the determination of this ratio, an approximate cubic equation similar to that used for cracked section analysis of bonded partially prestressed members is established. Predictions of stresses under service load are in good agreement with available test data. © 2005 Thomas Telford Ltd.published_or_final_versio

Predictor-corrector procedures for analysis of laminated plates using standard Mindlin finite element models

This paper introduces predictor-corrector methods for finite element analysis of laminated composite plates. The predictor stress, strain and deflection are directly computed from Mindlin finite element models without using shear correction factors. The corrector transverse shear stress is determined from the homogeneous stress equilibrium condition and the predictor in-plane stress by least-square fit. Shear correction factor for each element is estimated as the ratio of the transverse shear energies computed by the predictor transverse shear strain and the corrector transverse shear stress. The corrector deflection is calculated by incorporating the shear correction factor. First-, second- and third-order Mindlin nine-node plate elements are employed for testing the proposed procedure. Its accuracy is demonstrated by a large number of examples. © 2000 Elsevier Science Ltd.postprin

New medium teaching method for power electronics

Author name used in this publication: K. W. E. ChengRefereed conference paper2004-2005 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Three-dimensional vibration analysis of prisms with isosceles triangular cross-section

This paper studies the three-dimensional (3-D) free vibration of uniform prisms with isosceles triangular cross-section, based on the exact, linear and small strain elasticity theory. The actual triangular prismatic domain is first mapped onto a basic cubic domain. Then the Ritz method is applied to derive the eigenfrequency equation from the energy functional of the prism. A set of triplicate Chebyshev polynomial series, multiplied by a boundary function chosen to, a priori, satisfy the geometric boundary conditions of the prism is developed as the admissible functions of each displacement component. The convergence and comparison study demonstrates the high accuracy and numerical robustness of the present method. The effect of length-thickness ratio and apex angle on eigenfrequencies of the prisms is studied in detail and the results are compared with those obtained from the classical one-dimensional theory and the 3-D finite element method. Sets of valuable data known for the first time are reported, which can serve as benchmark values in applying various approximate beam and rod theories. © 2009 Springer-Verlag.published_or_final_versionSpringer Open Choice, 01 Dec 201

Three-dimensional vibration analysis of a torus with circular cross section

The free vibration characteristics of a torus with a circular cross section are studied by using the three-dimensional, small-strain, elasticity theory. A set of three-dimensional orthogonal coordinates system, comprising the polar coordinate (r, θ) at each circular cross section and the circumferential coordinate φ around the ring, is developed. Each of the displacement components ur, vτ, and wφ in the r, θ, and φ directions, respectively, is taken as a product of the Chebyshev polynomials in the r direction and the trigonometric functions in the θ and φ directions. Eigenfrequencies and vibration mode shapes have been obtained via a three-dimensional displacement-based extremum energy principle. Upper bound convergence of the first seven eigenfrequencies accurate to at least six significant figures is obtained by using only a few terms of the admissible functions. The eigenfrequency responses due to variation of the ratio of the radius of the ring centroidal axis to the cross-sectional radius are investigated in detail. Very accurate eigenfrequencies and deformed mode shapes of the three-dimensional vibration are presented. All major modes such as flexural thickness-shear modes, in-plane stretching modes, and torsional modes are included in the analysis. The results may serve as a benchmark reference for validating other computational techniques for the problem. © 2002 Acoustical Society of America.published_or_final_versio