Studies on Design Optimization of Coronary Stents

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
K. Srinivas ◽  
T. Nakayama ◽  
M. Ohta ◽  
S. Obayashi ◽  
T. Yamaguchi
Keyword(s):  
Design Optimization ◽  
Cross Sections ◽  
Latin Hypercube Sampling ◽  
Coronary Stents ◽  
Point Of View ◽  
Two Dimensional ◽  
Reattachment Length ◽  
Design Variables ◽  
Two Dimensional Flow ◽  
The Relationship

The stent design itself seems to be one of the factors responsible for restenosis. As a remedy, the present work attempts to perform a design optimization of coronary stents from a hemodynamic point of view. For the purpose, we have applied the principles of modern exploration of design space restricting ourselves to two-dimensional considerations. Width, thickness, and spacing of the struts of the stent formed the design variables. The objectives chosen for optimization were the vorticity generated, length of recirculation zone, and the reattachment distance in between the struts. Both semicircular and rectangular cross sections of stents were included. Starting with the range of design variables, sample stent cases were generated using Latin hypercube sampling. Objective functions were calculated for each of these by computing the two-dimensional flow using software FLUENT under the assumption of a steady, Newtonian flow considering a model stent with three struts. This was followed by Kriging to construct a response surface, which gives the relationship between the objectives and the design variables. The procedure gave nondominated fronts, which consist of optimized designs. Stents with minimum vorticity, with minimum recirculation distance, and the ones with maximum reattachment length in between struts were generated. The procedure is capable of producing the optimum set of design variables to achieve the prescribed objectives.

scholarly journals Influence of measuring force on CMM accuracy

2018 ◽  
Vol 208 ◽  
pp. 03004
Author(s):  
Bin Wang
Keyword(s):  
Cross Sections ◽  
Measurement Accuracy ◽  
Coordinate Measuring Machine ◽  
Point Of View ◽  
Signal Acquisition ◽  
Force Model ◽  
Thin Part ◽  
Measuring Machine ◽  
The Relationship ◽  
Measuring Force

The measuring accuracy of CMM (Coordinate Measuring Machine) is influenced by many factors, such as temperature, humidity, measuring force and method of signal acquisition. For thin parts, the influence of measuring force is especially obvious. In this paper, the relationship between measuring force and measurement accuracy is studied for a thin part with a U-shaped cross-section. By analyzing the structure of the probe and establishing the force model, the influencing factors of the accuracy of CMM are obtained, and the influence of the contact deformation and the bending deformation on the measurement accuracy is analyzed from the point of view of material mechanics. At the same time, the measurement accuracy of different measuring cross-sections is analyzed. Through the research of this paper, the relationship between measuring force and CMM is established, and an effective method to improve the accuracy of CMM is also found.

An Approach to Identify Six Sigma Robust Solutions of Multi/Many-Objective Engineering Design Optimization Problems

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Tapabrata Ray ◽  
Md Asafuddoula ◽  
Hemant Kumar Singh ◽  
Khairul Alam
Keyword(s):  
Design Optimization ◽  
Engineering Design ◽  
Optimization Problems ◽  
Product Family ◽  
Latin Hypercube Sampling ◽  
General Aviation ◽  
Design Variables ◽  
Engineering Design Optimization ◽  
The Face ◽  
And Performance

In order to be practical, solutions of engineering design optimization problems must be robust, i.e., competent and reliable in the face of uncertainties. While such uncertainties can emerge from a number of sources (imprecise variable values, errors in performance estimates, varying environmental conditions, etc.), this study focuses on problems where uncertainties emanate from the design variables. While approaches to identify robust optimal solutions of single and multi-objective optimization problems have been proposed in the past, we introduce a practical approach that is capable of solving robust optimization problems involving many objectives building on authors’ previous work. Two formulations of robustness have been considered in this paper, (a) feasibility robustness (FR), i.e., robustness against design failure and (b) feasibility and performance robustness (FPR), i.e., robustness against design failure and variation in performance. In order to solve such formulations, a decomposition based evolutionary algorithm (DBEA) relying on a generational model is proposed in this study. The algorithm is capable of identifying a set of uniformly distributed nondominated solutions with different sigma levels (feasibility and performance) simultaneously in a single run. Computational benefits offered by using polynomial chaos (PC) in conjunction with Latin hypercube sampling (LHS) for estimating expected mean and variance of the objective/constraint functions has also been studied in this paper. Last, the idea of redesign for robustness has been explored, wherein selective component(s) of an existing design are altered to improve its robustness. The performance of the strategies have been illustrated using two practical design optimization problems, namely, vehicle crash-worthiness optimization problem (VCOP) and a general aviation aircraft (GAA) product family design problem.

scholarly journals A Study of Glacier Flow for an Open-Pit Mine: An Exercise in Applied Glaciology

1974 ◽  
Vol 13 (69) ◽  
pp. 401-414 ◽  
Author(s):  
S. C. Colbeck
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Greenland Ice Sheet ◽  
Field Work ◽  
Open Pit Mine ◽  
Open Pit ◽  
Two Dimensional ◽  
Ice Flow ◽  
Two Dimensional Flow ◽  
Glacier Flow

As part of the feasibility study for the development of an open-pit mine at the edge of the Greenland ice sheet, a study is made of the ice flow toward the proposed pit. The flow is analyzed by considering the two-dimensional flow along seven cross-sections. The most favorable profile is determined for each cross-section and its flow calculated. The excavation necessary to expose the ore is 106 × 106 m3 of ice. 66 × 106 m3 of ice will have to be removed in order to establish favorable profiles and an additional 7.9 × 106 m3 of ice will have to be removed each year in order to prevent the glacier from thickening and advancing into the mine. Many other glaciological problems must be considered, and field work continues in order to provide more information about the area.

scholarly journals A Study of Glacier Flow for an Open-Pit Mine: An Exercise in Applied Glaciology

1974 ◽  
Vol 13 (69) ◽  
pp. 401-414 ◽  
Author(s):  
S. C. Colbeck
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Greenland Ice Sheet ◽  
Field Work ◽  
Open Pit Mine ◽  
Open Pit ◽  
Two Dimensional ◽  
Ice Flow ◽  
Two Dimensional Flow ◽  
Glacier Flow

As part of the feasibility study for the development of an open-pit mine at the edge of the Greenland ice sheet, a study is made of the ice flow toward the proposed pit. The flow is analyzed by considering the two-dimensional flow along seven cross-sections. The most favorable profile is determined for each cross-section and its flow calculated. The excavation necessary to expose the ore is 106 × 106m3of ice. 66 × 106m3of ice will have to be removed in order to establish favorable profiles and an additional 7.9 × 106m3of ice will have to be removed each year in order to prevent the glacier from thickening and advancing into the mine. Many other glaciological problems must be considered, and field work continues in order to provide more information about the area.

Two-Dimensional Numerical Simulation of Flow Around Rectangular Structures With Different Aspect Ratios

2011 ◽  
Author(s):  
Xinliang Tian ◽  
Muk Chen Ong ◽  
Jianmin Yang ◽  
Dag Myrhaug
Keyword(s):  
Cross Sections ◽  
Rectangular Cross Section ◽  
Offshore Structures ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Two Dimensional ◽  
Structural Components ◽  
Aspect Ratios ◽  
Two Dimensional Flow ◽  
Truss Spar

Many marine and offshore structures have structural components with square or rectangular cross-sections, e.g., columns of semi-submersibles and tension-leg platforms, heave damping plates of truss spar platforms as well as ship stabilizers. Two-dimensional flow normal to the longer edge of rectangles with different aspect ratios, i.e. from a square to a thin plate, is investigated numerically in the paper. The simulations are carried out at Re = 21400 (based on the free stream velocity and the height of the rectangular cross-section) by solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with the k-ω SST (Shear Stress Transport) turbulence model by using OpenFOAM. The hydrodynamic results are compared with published experimental data and numerical results. The paper also includes further investigations on the effect of different aspect ratios.

scholarly journals I. The flow of air and of an inviscid fluid around an elliptic cylinder and an aerofoil of infinite span, especially in the region of the forward stagnation point

1928 ◽  
Vol 227 (647-658) ◽  
pp. 1-19 ◽  
Keyword(s):  
Wind Tunnel ◽  
Flow Pattern ◽  
Stagnation Point ◽  
Elliptic Cylinder ◽  
Inviscid Flow ◽  
The Body ◽  
Inviscid Fluid ◽  
Two Dimensional ◽  
Two Dimensional Flow ◽  
The Relationship

(1) A study of some of the characteristics of the two-dimensional flow around an aerofoil mounted in a wind tunnel has been made by L. W. Bryant and D. H. Williams. This work included measurements of velocity in the neighbourhood of the aerofoil, and showed that under certain conditions the theoretical law of Kutta and Joukowski can be applied in practice to an aerofoil. The flow pattern measured in the wind tunnel was also compared with that for an inviscid flow having an equal circulation. The purpose of the present paper is to examine, in detail, the relationship between the inviscid and the wind-tunnel flows at the nose of an elliptic cylinder and also of an aerofoil of infinite span. Throughout the paper the term circulation is used in the usual hydrodynamic sense, it being understood that for a wind-tunnel flow the contour is not taken too close to the boundary of the body. Attention has been focussed on the forward stagnation point, because it is a well-defined point on the surface where the pressure is a maximum.

Superluminal coordinate transformations: the two-dimensional case

1983 ◽  
Vol 61 (2) ◽  
pp. 256-263 ◽  
Author(s):  
Louis Marchildon ◽  
Adel F. Antippa ◽  
Allen E. Everett
Keyword(s):  
Time Reversal ◽  
Discrete Symmetries ◽  
Two Dimensions ◽  
Point Of View ◽  
Dimensional Case ◽  
Two Dimensional ◽  
Coordinate Transformations ◽  
The Relationship

This is the first part of a two-paper series, in which we critically examine the various proposals that have been made for superluminal coordinate transformations. Here we consider the two-dimensional case. Starting from rather general assumptions, we show that the superluminal coordinate transformations in two dimensions are essentially uniquely determined. Different proposals for such transformations are then analyzed from the point of view of those assumptions. The relationship between the superluminal transformations and the discrete symmetries P (parity), T (time reversal), and PT is also discussed.

Multi-Objective Shape Optimization on the Inlet Pipe of a Vertical Inline Pump

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Ji Pei ◽  
Xingcheng Gan ◽  
Wenjie Wang ◽  
Shouqi Yuan ◽  
Yajing Tang
Keyword(s):  
Genetic Algorithm ◽  
Cross Sections ◽  
Great Influence ◽  
Latin Hypercube Sampling ◽  
Installation Space ◽  
Objective Functions ◽  
Inlet Pipe ◽  
Maximum Increase ◽  
Multi Objective ◽  
Design Variables

Vertical inline pump is a single-stage single-suction centrifugal pump with a bent pipe before the impeller, which is usually used where installation space is a constraint. In this paper, with three objective functions of efficiencies at 0.5 Qd, 1.0 Qd, and 1.5 Qd, a multi-objective optimization on the inlet pipe of a vertical inline pump was proposed based on genetic algorithm with artificial neural network (ANN). In order to describe the shape of inlet pipe, the fifth-order and third-order Bezier curves were adopted to fit the mid curve and the trend of parameters of cross sections, respectively. Considering the real installation and computation complexity, 11 variables were finally used in this optimization. Latin hypercube sampling (LHS) was adopted to generate 149 sample cases, which were solved by CFD code ANSYS cfx 18.0. The calculation results and design variables were utilized to train ANNs, and these surrogate models were solved for the optimum design using multi-objective genetic algorithm (MOGA). The results showed the following: (1) There was a great agreement between numerical results and experimental results; (2) The ANNs could accurately fit the objective functions and variables. The maximum deviations of efficiencies at 0.5 Qd, 1.0 Qd, and 1.5 Qd, between predicted values and computational values, were 1.94%, 2.35%, and 0.40%; (3) The shape of inlet pipe has great influence on the efficiency at part-load and design conditions while the influence is slight at overload condition; (4) Three optimized cases were selected and the maximum increase of the efficiency at 0.5 Qd, 1.0 Qd, and 1.5 Qd was 4.96%, 2.45, and 0.79%, respectively; and (5) The velocity distributions of outflow in the inlet pipe of the three optimized cases were more uniform than the original one.

scholarly journals ULRICH IDEALS AND MODULES OVER TWO-DIMENSIONAL RATIONAL SINGULARITIES

2016 ◽  
Vol 221 (1) ◽  
pp. 69-110 ◽  
Author(s):  
SHIRO GOTO ◽  
KAZUHO OZEKI ◽  
RYO TAKAHASHI ◽  
KEI-ICHI WATANABE ◽  
KEN-ICHI YOSHIDA
Keyword(s):  
Point Of View ◽  
Two Dimensional ◽  
Double Points ◽  
Rational Singularities ◽  
Geometric Point ◽  
The Relationship

The main aim of this paper is to classify Ulrich ideals and Ulrich modules over two-dimensional Gorenstein rational singularities (rational double points) from a geometric point of view. To achieve this purpose, we introduce the notion of (weakly) special Cohen–Macaulay modules with respect to ideals, and study the relationship between those modules and Ulrich modules with respect to good ideals.

Sign in / Sign up

Export Citation Format

Share Document