• Tribology and Lubricants
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• 제8권2호
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• pp.26-34
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• 1992

This paper suggests a method to predict the flying state of the head slider in a hard disk drive (HDD) by using an optimization technique. The modified Reynolds equation for the hydrodynamic lubrication theory under the slip flow condition is used to describe the air-bearing system and a Finite Volume Method (FVM) is applied to solve the equation. Especially, Augmented Lagrange Multiplier (ALM) method is employed to find the minimum flying height, the pitch angle and the roll angle of the slider, which is shown to be faster and more general than the conventional update schemes. By using the proposed method, the variations of the flying state are analyzed as a function of the slider position in the direction of the disk radius for various disk velocities and skew angles.

• 한국정밀공학회지
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• 제15권6호
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• pp.145-152
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• 1998

This paper presents an optimum design of a rotor-bearing spindle system for a ultra centrifuge (80,000 RPM) supported by ball bearings with nonlinear stiffness characteristics. To obtain the nonlinear bearing stiffnesses, a ball bearing is modeled in five degrees of freedom and is analyzed quasi-statically. The dynamic behaviors of the nonlinear rotor-bearing system are analyzed by using a transfer-matrix method iteratively. For optimization. we use the cost function that simultaneously minimizes the weight of a rotor and maximizes the separation margins to yield the critical speeds as far from the operating speed as possible. Augmented Lagrange Multiplier (ALM) method is employed for the nonlinear optimization problem. The result shows that the rotor-bearing spindle system is optimized to obtain 9.5％ weight reduction and 21％ separation margin.

• Communications for Statistical Applications and Methods
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• 제4권3호
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• pp.663-676
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• 1997

We obtain the simultaneous unit roots test statistics for both regular and seasonal unit roots in a time series with possible seasonal deterministic trends. The limiting distributions of the proposed test statistics are derived and empirical percentiles of the test statistics are tabulated for some seasonal periods. The power and size of the test statistics are examined for finite samples through a Monte Carlo simulation and Compared with those of the Lagrange multiplier test.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.159-165
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• 2002

Numerical analysis of dynamic contact and stress developing in the high-speed driven valve of an internal combustion engine is presented. The valve is modeled by finite element techniques, and the dynamic contact between the valve and the valve seat is analyzed by the solution strategies of differential algebraic equations. Also an iterative scheme similar to the augmented Lagrange multiplier method is employed to enforce the contact constraints. It is shown that the contact and separation between the valve and the valve seat can be computed by the finite element techniques without assuming the artificial springs, and the efficiency and accuracy of the solution are demonstrated by the numerical examples.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.154-161
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• 1997

This paper presents the method to eliminate the constraint reaction in the Lagrange multiplier form equation of motion by using a generalized coordinate driveder from the velocity constraint equation. This method introduces a matrix method by considering the m dimensional space spanned by the rows of the constraint jacobian matrix. The orthogonal vectors defining the constraint manifold are projected to null vectors by the tangential vectors defined on the constraint manifold. Therefore the orthogonal projection matrix is defined by the tangential vectors. For correcting the generalized position coordinate, the optimization problem is formulated. And this correction process is analyzed by the quasi Newton method. Finally this method is verified through 3 dimensional vehicle model.

• 한국자동차공학회논문집
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• 제11권2호
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• pp.31-39
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• 2003

Numerical analysis for valve train dynamics of an internal combustion engine is presented. The components of the valve train are modeled by finite element techniques, and the dynamic contacts between the components are analyzed by the solution strategies of differential algebraic equations. Also an iterative scheme similar to the augmented Lagrange multiplier method is employed to enforce the contact constraints. It is shown that the contact and separation between the components of the valve train can be computed by the finite element techniques, and the numerical examples are presented to demonstrate the efficiency of the solution.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.44-51
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• 2011

Polymer Electrolyte Fuel Cells (PEFCs) operate in wide-range changes in temperature, humidity, and electric current for automotive applications. In order to operate automotive PEFC efficiently, optimal air supply is required to adjust to these changes. This paper presents an air-supply optimization process that consists of experiments, modeling of the PEFC system, and optimization. The objective is to establish an air supply suitable for the required power for PEFC system and optimized with a Lagrange multiplier. Our simplified PEFC system model is used as a constraint for optimization problem. The result of this paper presents that efficient operation of PEFC system can be achieved by air-supply optimization.

• 전기의세계
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• 제30권6호
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• pp.375-385
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• 1981

New algorithms are derived for nonlinear programming problems which are characterized by their large variables and equality and inequality constraints. The algorithms are based upon the introduction of the Dependent-Variable-Elimination method, Independent-Variable-Reduction method, Optimally-Ordered-Triangular-Factorization method, Equality-Inequality-Sequential-Satisfaction method, etc. For a case study problem relating to the optimal determination of load flow in a 10-bus, 13-line sample power system, several approaches are undertaken, such as SUMT, Lagrange's Multiplier method, sequential applications of linear and quadratic programming method. For applying the linear programming method, the conventional simplex algorithm is modified to the large-system-oriented one by the introduction of the Two-Phase method and Variable-Upper-Bounding method, thus resulting in remarkable savings in memory requirements and computing time. The case study shows the validity and effectivity of the algorithms presented herein.

• 전자공학회논문지A
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• 제31A권3호
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• pp.68-76
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• 1994

In the automatic transistor sizing with computer for optimizing delay and the chip area of CMOS digital circuits, conventionally either a mathematical method or a heuristic method has been used. In this paper, we present a new method of transistor sizing, a sort of combination of the above two methods, in which the mathematical method is used for sizing of critical paths and the heuristic method is used for desizing of non-critical paths. In order to reduce the overall problem dimension, a basic block called an extended stage is introduced which includes a basic stage, parallel transistors and complementary part. Optimization for multiple critical paths is formulated as a problem of area minimization subject to delay constraints and is solved by the augmented Lagrange multiplier method. The transistor sizes along non-critical paths are decreased successively without affecting the critical path delay times. The proposed scheme was successfully applied to several test circuits.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.11-18
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• 2001

In this paper, a new algorithm of coupling Element-Free Galerkin Method(EFGM) and Boundary Element Method(BEM) using the variational formulation is presented. A global variational coupling formulation of EFGM-BEM is achieved by combining the variational form on each subregion. In the formulation, Lagrange multiplier method is introduced to satisfy the compatibility conditions between EFGM subregion and BEM subregion. Some numerical examples are studied to verify accuracy and efficiency of the proposed method, in which numerical performance of the method is compared with that of conventional method such as EFGM-BEM direct coupling method, EFGM and BEM. The proposed method incorporating the merits of EFGM and BEM is expected to be applied to special engineering problems such as the crack propogation problems in very large domain, and underground structures with joints.