• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.199-209
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• 2001

Modal analysis method (MAM) is introduced for the fully coupled structural dynamic problems. In this paper, the beam with active constrained layered damping (ACLD) treatment is considered as a representative problem. The ACLD beam consists of a viscoelastic layer that is sandwiched between the base beam structure and an active piezoelectric layer. The exact damped natural modes are spectrally formulated from a set of fully coupled dynamic equations of motion. The orthogonality property of the exact damped natural modes is then derived in a closed form to complete the modal analysis method. The accuracy of the present MAM is evaluated through some illustrative examples: the dynamic characteristics obtained by the present MAM are compared with the results by spectral element method (SEM) and finite element method (FEM). It is numerically proved that MAM solutions become identical to the accurate SEM solutions as the number of exact natural used in MAM is increased.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.410-415
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• 2000

In this paper feasible direction method which is one of the optimization method is adopted to natural frequency optimization. In order to find the optimum design of structures that have characteristic natural frequency range, a numerical optimization method to solving eigenvalue problems is a widely used approach. However most cases, it is difficult to decide the accurate thickness and shape of structures that have allowable natural frequency in design constraints. Parallel analysis algorithm involving the feasible direction optimization method and Rayleight-Ritz eigenvalue solving method is developed. The method is implemented by using finite element method. It calculated the optimal thickness and the thickness ratio of each element of 2-D plane element through the parallel algorithm method which satisfy the design constraint of natural frequency.

• 한국소음진동공학회논문집
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• 제14권9호
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• pp.801-810
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• 2004

Parameter modification of a linear finite element model(FEM) based on modal sensitivity matrix is usually performed through an effort to match FEM modal data to experimental ones. However, there are cases where this method can't be applied successfully; lack of reliable modal data and ill-conditioning of the modal sensitivity matrix constitute such cases. In this research, a novel concept of introducing feedback loops to the conventional modal test setup is proposed. This method uses closed-loop natural frequency data for parameter modification to overcome the problems associated with the conventional method based on modal sensitivity matrix. We proposed the whole procedure of parameter modification using the closed-loop natural frequency data including the modal sensitivity modification and controller design method. Proposed controller design method is efficient in changing modes. Numerical simulation of parameter estimation based on time-domain input/output data is provided to demonstrate the estimation performance of the proposed method.

• 한국해양공학회지
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• 제27권5호
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• pp.36-42
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• 2013

We present the optimum design for the cross-sectional(sizing) and shape optimization of truss structures with natural frequency constraints. The optimum design method used in this paper employs continuous design variables and the Harmony Search Algorithm(HSA). HSA is a meta-heuristic search method for global optimization problems. In this paper, HSA uses the method of random number selection in an update process, along with penalty parameters, to construct the initial harmony memory in order to improve the fitness in the initial and update processes. In examples, 10-bar and 72-bar trusses are optimized for sizing, and 37-bar bridge type truss and 52-bar(like dome) for sizing and shape. Four typical truss optimization examples are employed to demonstrate the availability of HSA for finding the minimum weight optimum truss with multiple natural frequency constraints.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.51-61
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• 2022

Gas separation via hollow fibre membrane modules (HFMM) is deemed to be a promising technology for natural gas sweetening, particularly for lowering the level of carbon dioxide (CO₂) in natural gas, which can cause various problems during transportation and process operation. Separation performance via HFMM is affected by membrane properties, module specifications and operating conditions. In this study, a mathematical model for HFMM is developed, which can be used to assess the effects of the aforementioned variables on separation performance. Appropriate boundary conditions are imposed to resolve steady-state values of permeate variables and incorporated in the model equations via an iterative numerical procedure. The developed model is proven to be reliable via model validation against experimental data in the literature. Also, the model is capable of capturing axial variations of process variables as well as predicting key performance indicators. It can be extended to simulate a large-scale plant and identify an optimal process design and operating conditions for improved separation efficiency and reduced cost.

• 한국의류학회지
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• 제35권3호
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• pp.359-370
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• 2011

This study analyzes the textiles design of natural indigo dyed products in Korea and Japan. In this study, a total of 556 Korean natural indigo dyed products, and 2,730 Japanese natural indigo dyed products were used for analysis. The subjects of this study were 556 natural indigo dyed products and 2,730 Japanese natural indigo dyed products selling natural indigo dyed products which were found using search engine keywords of natural indigo dyeing and natural dyeing. Research and analysis was treated regarding the products, items, patterns, and the representation techniques of the patterns. The results of this study are as follows. In the pattern used for natural indigo dyed products, 71.4% of Korean products have no pattern, but 77.1% of Japanese products have patterns. On the representation techniques of the patterns, Korean products used tie-dyeing and a dip patterned fabric. While in the Japanese products, the most frequent patterning techniques were paraffin dye, followed by tie-dyeing, yarn-dyed and weaving, screen printing, and yarn-dyed and knitting. Regarding the kinds of patterns for natural indigo dyed products, only 8 kinds of patterns were used in Korean products; however, over 50 kinds of various patterns were used in Japanese products. Most patterns in the Korean products were ion patterns made by tie-dyeing. While in the Japanese products, the most frequent patterns were stripe patterns, followed by flower, dot, and ion patterns. Based on these research results, the problems of the textile design of Korean natural indigo dyed products were that most of the products have no pattern, and even though there were patterns, they lacked variations between the products. While in the case of Japan, they used the traditional and modem patterns of various textile representation techniques.

• Journal of applied mathematics & informatics
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• 제34권1_2호
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• pp.85-94
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• 2016

In this paper, we first propose a fast one-parameter relaxation (FOPR) method with a scaled preconditioner for solving the saddle point problems, and then we present a formula for finding its optimal parameter. To evaluate the effectiveness of the proposed FOPR method with a scaled preconditioner, numerical experiments are provided by comparing its performance with the existing one or two parameter relaxation methods with optimal parameters such as the SOR-like, the GSOR and the GSSOR methods.

• Journal of applied mathematics & informatics
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• 제31권5_6호
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• pp.733-745
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• 2013

In this paper, we first propose a new technique of the functional iterative methods VIM (Variational iteration method) and NHPM (New homotopy perturbation method) for solving two-point boundary value problems, and then we compare their numerical results with those of the finite difference method (FDM).

• Journal of applied mathematics & informatics
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• 제26권3_4호
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• pp.481-491
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• 2008

In this paper, we introduce and analyze a new class of generalized mixed equilibrium-like problems. By using the auxiliary principle technique, we suggest three iterative algorithms for the generalized mixed equilibrium-like problem. Under certain conditions, we establish the convergence of the iterative algorithms. Our results extend, improve and unify several known results in this field.

• 대한수학회지
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• 제53권3호
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• pp.691-707
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• 2016

In this paper, we first introduce two one-parameter relaxation (OPR) iterative methods for solving singular saddle point problems whose semi-convergence rate can be accelerated by using scaled preconditioners. Next we present formulas for finding their optimal parameters which yield the best semi-convergence rate. Lastly, numerical experiments are provided to examine the efficiency of the OPR methods with scaled preconditioners by comparing their performance with the parameterized Uzawa method with optimal parameters.