• 한국정밀공학회지
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• 제27권12호
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• pp.41-47
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• 2010

There are many unbalanced models such as helicopter's rotor blades, small-sized precision motor in industrial applications. In the real products, their gravity center usually does not accord with the desired gravity center. If the deviation is large between them, it can be a major cause of vibration and noise as the part of model rotate. Therefore the gravity center in the rotational parts should be controlled properly because of static and dynamic balancing of the parts. In the research, the rotor blade of unmanned helicopter has been selected to obtain the high quality of balancing. In order to achieve the purpose, measuring system has been developed. In the system applied principle is three point weighting method, which is one of the Multiple-point Weighting Method. It has circle fitting for compensation of machining error, after measuring the values. From this study, the results showed that the proposed measurement procedure gives reliable and precise gravity center.

• Journal of applied mathematics & informatics
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• 제30권1_2호
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• pp.235-244
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• 2012

In this paper, we solve the three-dimensional biharmonic equation with Dirichlet boundary conditions of second kind using the full multigrid (FMG) algorithm. We derive a finite difference approximations for the biharmonic equation on a 18 point compact stencil. The unknown solution and its second derivatives are carried as unknowns at grid points. In the multigrid methods, we use a fourth order interpolation to producing a new intermediate unknown functions values on a finer grid, and the full weighting restriction operators to calculating the residuals at coarse grid points. A set of test problems gives excellent results.

• 한국멀티미디어학회논문지
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• 제11권4호
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• pp.471-480
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• 2008

농자들은 청각장애를 가지고 있기 때문에 알람, 도어 벨, 싸이렌, 경적, 전화 벨 등과 같은 유용한 소리정보를 인식할 수 없다. 이러한 문제를 해결하기 위해서는 주요한 환경소리 인식방법을 탑재한 휴대형 청각보조 장구가 요구되어진다. 본 논문에서는 환경소리 인식시스템에 적용할 수 있는 능동형 기울기 가중치제약 방식의 새로운 동적 시간정합 알고리듬을 제안하였다. 환경소리 인식방법은 크게 세 단계로 구성된다. 첫 번째 단계에서는 소리의 주파수 성분과 크기를 이용하여 시작점과 끝점을 추출한다. 두 번째 단계에서는 추출된 구간에 대하여 특징을 추출하며 세 번째 단계에서는 추출된 특징들을 분류한다. 실험 결과 제안한 방법의 인식률이 거의 90%가 되었다. 그리고 기존의 동적 시간정합 알고리듬과 비교하였을 때 인식율에 있어서 약 20%정도의 개선이 있었다. 따라서 제안된 방법을 사용하여 농자가 환경소리를 인식할 수 있는 휴대형 청각 보조 장구가 개발된다면 그들의 생활에 편리함을 줄 수 있을 것으로 판단된다.

• Structural Monitoring and Maintenance
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• 제9권1호
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• pp.59-80
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• 2022

In the present study, the objective is to detect the structural damages using the responses obtained from the sensors at the optimal location under uncertainty conditions. Reducing the error rate in damage detection process due to responses' noise is an important goal in this study. In the proposed algorithm for optimal sensor placement, the noise of responses recorded from the sensors is initially reduced using the principal component analysis. Afterward, the optimal sensor placement is obtained by the damage detection equation based sensitivity analysis. The sensors are placed on degrees of freedom corresponding to the minimum error rate in structural damage detection through this procedure. The efficiency of the proposed method is studied on a truss bridge, a space dome, a double-layer grid as well as a three-story experimental frame structure and the results are compared. Moreover, the performance of the suggested method is compared with three other algorithms of Average Driving Point Residue (ADPR), Effective Independence (EI) method, and a mass weighting version of EI. In the examples, young's modulus, density, and cross-sectional areas of the elements are considered as uncertainty parameters. Ultimately, the results have demonstrated that the presented algorithm under uncertainty conditions represents a high accuracy to obtain the optimal sensor placement in the structures.

• 한국주거학회논문집
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• 제20권4호
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• pp.131-142
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• 2009

High-rise and high-density apartment complexes have been built and supplied on a large scale in the 1st period of the New Town project in metropolitan areas since the late 1980s. Now It has become necessary to improve those apartment complexes, which have serious deterioration problems for aging more than about 20 years accompanying simultaneity and a large scale. The purpose of this research is to develop the evaluating indicators to measure the level of deterioration of apartments inclusively and practically in order to regenerate apartments as sustainable residential environments. This study is composed of the following four parts; (a) establishing the conceptual model of evaluation of apartment deterioration, (b) selecting evaluation items, (c) constituting evaluation measurement, and（ｄ)weighting evaluation indicators. First, deterioration of apartments was conceptualized by physical. social, and economical aspects in terms of sustainable development and proposed the conceptual model of hierarchy structure of evaluation of apartment deterioration by literature reviews. Second, evaluating items were selected based on literature reviews of existing indicators and preceding studies about apartments of Korea and foreign countries. The evaluating indicators were identified as a total of 77 evaluating items which were composed of three dimensions and 9 attributes on the basis of the conceptual model. They cover comprehensive scope of the apartment such as unit, building, complex, and site. Third, as the measurement, the 5 point ordinal scale measure was suggested. The evaluating measurement including measure standards, measure methods, and measure contents were developed by each evaluating items. Lastly, the weighting of evaluating indicators was analyzed by AHP method conducted by survey on the expert group. Items were identified as high contributors or low contributors. The weighting of these items could suggest several evaluations according to the situation. The evaluation of the level of deterioration can be done by both total evaluation and a specific field of evaluation. In addition, it is easy to grasp deteriorated attributes or dimensions by providing a radar and bar chart showing evaluation results. These evaluating indicators could be a useful tool to grasp actual methods for the regeneration of apartments.

• 한국유체기계학회 논문집
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• 제13권6호
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• pp.42-50
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• 2010

The present analysis deals with a numerical procedure for optimizing the shape of elliptical dimples in a cooling channel. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis is employed in conjunction with the SST model for predictions of the turbulent flow and the heat transfer. Three non-dimensional geometric design variables, such as the ellipse dimple diameter ratio, ratio of the dimple depth to the average diameter, and ratio of the distance between dimples to the pitch are considered in the optimization. Twenty-one experimental points within design space are selected by Latin Hypercube Sampling. Each objective function values at these points are evaluated by RANS analysis and producing optimal point using surrogate model. The linear combination of heat transfer coefficient and friction loss related terms with a weighting factor is defined as the objective function. The results show that the optimized elliptical dimple shape improves considerably the heat transfer performance than the circular dimple shape.

• 대기
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• 제26권4호
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• pp.697-709
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• 2016

This study estimates and evaluates the extreme value of 30 m-resolution daily maximum and minimum temperatures over South Korea, using inverse distance weighting (IDW), parameter-elevation regression on independent slopes model (PRISM) and generalized extreme value (GEV) method. The three experiments are designed and performed to find the optimal estimation strategy to obtain extreme value. First experiment (EXP1) applies GEV firstly to automated surface observing system (ASOS) to estimate extreme value and then applies IDW to produce high-resolution extreme values. Second experiment (EXP2) is same as EXP1, but using PRISM to make the high-resolution extreme value instead of IDW. Third experiment (EXP3) firstly applies PRISM to ASOS to produce the high-resolution temperature field, and then applies GEV method to make high resolution extreme value data. By comparing these 3 experiments with extreme values obtained from observation data, we find that EXP3 shows the best performance to estimate extreme values of maximum and minimum temperatures, followed by EXP1 and EXP2. It is revealed that EXP1 and EXP2 have a limitation to estimate the extreme value at each grid point correctly because the extreme values of these experiments with 30 m-resolution are calculated from only 60 extreme values obtained from ASOS. On the other hand, the extreme value of EXP3 is similar to observation compared to others, since EXP3 produces 30m-resolution daily temperature through PRISM, and then applies GEV to that result at each grid point. This result indicates that the quality of statistically produced high-resolution extreme values which are estimated from observation data is different depending on the combination and procedure order of statistical methods.

• 한국농공학회지
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• 제44권4호
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• pp.85-98
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• 2002

The purpose of this study is to develop a land use planning model (LUPM) which can be applied to development of rural villages considering their spatial expansion. The LUPM finds out and allocates the new built site required for the improvement of existing villages. in the development of LUPM, CA (cellular automata) and land suitability analysis methods were applied combinedly. The model uses basically numerical data of CIS based on grid data. Agglomerated settlement, as a type of village for simulation, was adopted. Probability of land use change for optimizing development area was calculated by the six criteria: slope. drainage characteristic, direction of slope, as absolute suitability of grid itself, distance from road. distance from stream and distance from the village center, as relative probability by neighborhood cells. Weighting values of these criteria were quantified by AHP (analytic hierarchy process) method, which is one of MCE(multi-criteria evaluation) method. The algorithm of the model was verified by three example villages: an isolation village, a village with horizontal road, and a village with nodal point of cross road

• 대한기계학회논문집B
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• 제31권8호
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• pp.663-671
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• 2007

In this work, shape optimization of a wire-wrapped fuel assembly in a liquid metal reactor has been carried out by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial basis neural network method, a well known surrogate modeling technique for optimization. Sequential Quadratic Programming is used to search the optimal point from the constructed surrogate. Two geometric design variables are selected for the optimization and design space is sampled using Latin Hypercube Sampling. The optimization problem has been defined as a maximization of the objective function, which is as a linear combination of heat transfer and friction loss related terms with a weighing factor. The objective function value is more sensitive to the ratio of the wire spacer diameter to the fuel rod diameter than to the ratio of the wire wrap pitch to the fuel rod diameter. The optimal values of the design variables are obtained by varying the weighting factor.

• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.271-280
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• 2017

This study presents the application of satellite laser ranging (SLR) to orbit determination (OD) of high-Earth-orbit (HEO) satellites. Two HEO satellites are considered: the Quasi-Zenith Satellite-1 (QZS-1), a Japanese elliptical-inclinedgeosynchronous-orbit (EIGSO) satellite, and the Compass-G1, a Chinese geostationary-orbit (GEO) satellite. One week of normal point (NP) data were collected for each satellite to perform the OD based on the batch least-square process. Five SLR tracking stations successfully obtained 374 NPs for QZS-1 in eight days, whereas only two ground tracking stations could track Compass-G1, yielding 68 NPs in ten days. Two types of station bias estimation and a station data weighting strategy were utilized for the OD of QZS-1. The post-fit root-mean-square (RMS) residuals of the two week-long arcs were 11.98 cm and 10.77 cm when estimating the biases once in an arc (MBIAS). These residuals were decreased significantly to 2.40 cm and 3.60 cm by estimating the biases every pass (PBIAS). Then, the resultant OD precision was evaluated by the orbit overlap method, yielding three-dimensional errors of 55.013 m with MBIAS and 1.962 m with PBIAS for the overlap period of six days. For the OD of Compass-G1, no station weighting strategy was applied, and only MBIAS was utilized due to the lack of NPs. The post-fit RMS residuals of OD were 8.81 cm and 12.00 cm with 49 NPs and 47 NPs, respectively, and the corresponding threedimensional orbit overlap error for four days was 160.564 m. These results indicate that the amount of SLR tracking data is critical for obtaining precise OD of HEO satellites using SLR because additional parameters, such as station bias, are available for estimation with sufficient tracking data. Furthermore, the stand-alone SLR-based orbit solution is consistently attainable for HEO satellites if a target satellite is continuously trackable for a specific period.