[서평]「The Unified Modeling Language User Guide」

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

Aim: This executive summary of the valvular heart disease guideline provides recommendations for clinicians to diagnose and manage valvular heart disease as well as supporting documentation to enco...

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: Executive Summary

In this paper an ordered multi-material SIMP (solid isotropic material with penalization) interpolation is proposed to solve multi-material topology optimization problems without introducing any new variables. Power functions with scaling and translation coefficients are introduced to interpolate the elastic modulus and the cost properties for multiple materials with respect to the normalized density variables. Besides a mass constraint, a cost constraint is also considered in compliance minimization problems. A heuristic updating scheme of the design variables is derived from the Kuhn-Tucker optimality condition (OC). Since the proposed method does not rely on additional variables to represent material selection, the computational cost is independent of the number of materials considered. The iteration scheme is designed to jump across the discontinuous point of interpolation derivatives to make stable transition from one material phase to another. Numerical examples are included to demonstrate the proposed method. Because of its conceptual simplicity, the proposed ordered multi-material SIMP interpolation can be easily embedded into any existing single material SIMP topology optimization codes.

Multi-material topology optimization using ordered SIMP interpolation

This paper is concerned with a delayed predator–prey system with diffusion effect. First, the stability of the positive equilibrium and the existence of spatially homogeneous and spatially inhomogeneous periodic solutions are investigated by analyzing the distribution of the eigenvalues. Next the direction and the stability of Hopf bifurcation are determined by the normal form theory and the center manifold reduction for partial functional differential equations. Finally, some numerical simulations are carried out for illustrating the theoretical results.

Stability and Hopf bifurcation in a diffusive predator–prey system with delay effect

Structural optimization with frequency constraints is highly nonlinear dynamic optimization problems. Genetic algorithm (GA) has greater advantage in global optimization for nonlinear problem than optimality criteria and mathematical programming methods, but it needs more computational time and numerous eigenvalue reanalysis. To speed up the design process, an adaptive eigenvalue reanalysis method for GA-based structural optimization is presented. This reanalysis technique is derived primarily on the Kirsch's combined approximations method, which is also highly accurate for case of repeated eigenvalues problem. The required number of basis vectors at every generation is adaptively determined and the rules for selecting initial number of basis vectors are given. Numerical examples of truss design are presented to validate the reanalysis-based frequency optimization. The results demonstrate that the adaptive eigenvalue reanalysis affects very slightly the accuracy of the optimal solutions and significantly reduces the computational time involved in the design process of large-scale structures.

Fast structural optimization with frequency constraints by genetic algorithm using adaptive eigenvalue reanalysis methods

Hollow structures are widely used in industry because of the high stiffness-to-mass ratio and mature joining technology. However, in topology optimization (TO), the TO results are almost solid structures because the geometries of hollow structures cannot be represented in an explicit way. Therefore, this paper innovatively presents an explicit three-dimensional TO method to obtain the hollow structures using moving morphable components (MMCs), which is achieved by combining two topology description functions, namely, internal and external topology description functions. Especially, the combining topology description functions of the hollow component are derived for the first time. Compared to the solid TO results, the structural stiffness of the hollow TO results can be further improved. Finally, the TO problems of the three-dimensional square Mindlin cantilever plate, cantilever beam and miniature bending beam demonstrate the effectiveness of the proposed method.

Hollow structural design in topology optimization via moving morphable component method

The crashworthiness design of automotive structure is crucial to ensure the safety of passengers. Lumped parameter models, multi-body models, plastic frame models and detailed shell element models were all introduced to simulate the collision process of automotive structure. However, plastic frame models were only confined to use box beams. Therefore, this paper presents a comprehensive crashworthiness design of plastic frame model, which can innovatively create complex thin-walled beams with arbitrary cross-sectional shapes, such as open, single-cell, double-cell, three-cell and four-cell sections. Numerical example verified that the proposed model can effectively replace detailed shell element model to accelerate the crashworthiness analysis of automotive structure, especially for the conceptual design.

Wenjie Zuo

Papers

Multi-material topology optimization using ordered SIMP interpolation

Stability and Hopf bifurcation in a diffusive predator–prey system with delay effect

Fast structural optimization with frequency constraints by genetic algorithm using adaptive eigenvalue reanalysis methods

Hollow structural design in topology optimization via moving morphable component method

Simplified crashworthiness method of automotive frame for conceptual design