• 한국정밀공학회지
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• 제12권3호
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• pp.32-41
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• 1995

In the analysis of metal forming processes by the finite element method, there are many numerical instabilities such as element locking, hourglass mode and shear locking. These instabilities may have a bad effect upon accuracy and convergence. The present work is concerned with improvement of stability and efficiency in two-dimensional rigid-plastic finite element method using various type of elemenmts and numerical intergration schemes. As metal forming examples, upsetting and backward extrusion are taken for comparison among the methods: various element types and numerical integration schemes. Comparison is made in terms of stability and efficiency in element behavior and computational efficiency and a new scheme of adaptive directional reduced integration is introduced. As a result, the finite element computation has been stabilized from the viewpoint of computational time, convergency, and numerical instability.

• 소성∙가공
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• 제4권4호
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• pp.365-374
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• 1995

Numerical simulation of blade forming is carried out as stretch forming by an elasto-plastic finite element method. The method adopts a Lagrangian formulation, which incorporates large deformation and rotation, with a penalty method to treat the contact boundary condition. Numerical integration is done with a directional reduced integration scheme to avoid shear locking. The numerical results demonstrates various final shapes of blades which depend on the variation of the stretching force. The strain distributions in deformed blades are also obtained with the variation of the stretching force.

• 대한기계학회논문집
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• 제18권10호
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• pp.2640-2652
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• 1994

The stiffness of 6-node isotropic element is stiffer than that of 8-node isotropic element of same configuration. This phenomenon was called 'Relative Stiffness Stiffening Phenomenon'. In this paper, an equation of sampling point modification which correct this phenomenon was derived for the composite plate, as well as an equation for an isotropic plate. The relative stiffness stiffening phenomena of an isotropic plate element could be corrected by modifying Gauss sampling points in the numerical integration of stiffness matrix. This technique could also be successfully applied to the static analyses of composite plate modeled by the 3-dimensional 16-node elements. We predicted theoretical errors of stiffness versus the number of layers that result from the reduction of numerical integration order. These errors coincide very well with the actual errors of stiffness. Therefore, we can choose full integration of reduced integration based upon the permissible error criterion and the number of layers by using the thoretically predicted error.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.36-47
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• 1999

Three-way catalyst converter, cleaning up the exhaust gas contamination of SI engine, has the best efficiency when A/F ratio is near the stoichiometry . The feedback control using oxygen sensors in the exhaust manifold has limits caused by the system delays. So the accurate measurement of air flow rate to an engine is essential to control the fuel injection rate especially on transient condition like the rapid throttle opening and closing. To measure the rapid change of flow rates. the air flow meter for the engine requires quick response, flow reversal detection, and linearity . Tjhe proposed integration type air flow meter (IFM), composed of an ultrasonic flow meter with an integration circuit, has significantly improved the measurement accuracy of air mass inducted through the throttle body. The proposed control method estimated the air mass at the cylinder port using the measured air mass at the throttle . For the fuel dynamic model, the two constant fuel model is introduced . The control parameters from air and fuel dynamics are tuned to minimize the excursion of the air fuel ratio. As a result A/F ratio excursion can be reduced within 5% when throttle rapidly opens and closes at the various engine conditions.

• 농업과학연구
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• 제18권2호
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• pp.127-139
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• 1991

1. The purpose of this study was to recommend ways of more efficient pheasant farm business management and promoting the demand of pheasant foods by reviewing the current pheasant farm business management and the general pattern of consumption of pheasant foods. The study was conducted on the basis of the field survey covering 83 pheasant feeders and 283 consumers. 2. Majority of pheasant feeders, 86.8%(n=72), utilized broiler feed for pheasant rearing because of high price of exclusive pheasant feed. 3. In case of producing 1,000 heads of 5 month-old pheasant, the primary production cost per head was roughly calculated at about 5,530 Won. And 40.3% of primary production cost was consisted of feed cost and 12.9% was depreciation cost for facillities including artificial incubator equipments. 4. 81.1%(n=51) of whole surveyed feeders disposed of 1-4 week-old birds directly to the new feeders and 6%(n=6) sold them to the middlemen who were almost pioneering pheasant feeders. 5. 48.9%(n=138) of the surveyed consumer respondents have taken the pheasant foods once and several times, and the others never once. And 50.6%(n=69) of the respondents who had taken the pheasant foods were satisfied with the tastes. 6. The surveyed consumers were asked whether they knew the nutritional value of pheasant foods and 47.3(n=136) recognized it positively and 37.5%(n=106) negatively. 7. To increase the pheasant farm income and promote the demand of pheasant foods. followings are recommended. - Production cost should be reduced by cooperative utilization of facilities and equipments at farm level, and exclusive pheasant feed of good quility should be developed and supplied to the feeders at a low price. - Pheasant marketing and pricing system should be improved to prevent consumers from price disorder of retail shop including pheasant food reataurants and to popularize the pheasant foods. - Various type of menu of pheasant foods should be developed not only to satisfy consumers in tastes but also to solve the seasonality of pheasant supply. But it is preferable that this action is led by pheasant feeders and their cooperative organization, espectially through vertical intergration system owned by pheasant feeders. - Generic, pioneering advertisement and promotion should be carried out to promote primary demend of pheasant foods. It would be preferable that these primary demend advertising and promoting activities shuld be sponsored by pheasant feeders and government together. And their activities should be supported by institutional regulation.

• 보건행정학회지
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• 제5권1호
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• pp.80-105
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• 1995

Assuming that we introduced integration of medical insurance society for self-employed, this study was conducted to examine effects and results after the integration and to research more effective method for integration. To assess effects and results of the finacial status of 266 insurance societies after intergration, the data were obtained from "The Medical Insurance Program for Self-Employeds Statistical Yearbook in 1992". The major finding are as follows : 1. Three alternative integration proposals were made. First alternative proposal was consisted of 232 medical insurance societies, second was 187, and third was 115. 2. As the results of average number of the insured per insurance societies of medical insurance program for self-employed every alternative proposal, first was 88, 119 persons, second was 108, 576, and third was 178, 967 from 76, 576 persons of present socienties. 3. It was true that the more average size of societies increased, the more average administration expenditure per 1, 000 insured reduced. 4. The average size of societies grew bigger, the rate of general expenditure to general revenue more improved. Also, the rate of benefits to contributions was changed for better. But if not to have had correct analysis and precise preparation for integration, effects and results of integration were always not optiized. 5. According to results of simple regression formulas, it was proved that the more the average size of societies was increased, the more result was advantaged. 6. The law of majority and the economy of scale were applied in this study, and it was necessary to analyze and assess effectiveness and efficiency of integration. Therefore, when the integration of medical insurance societies for self-employeds will be performed, it must be taken into consideration. Among three alternative proposals, third was showed more effective alternative than anothe, second was presented more ineffective result than present system. To achieve more effective and efficient integration of regional medical insurance societies throughout the result of the regression formula on present cost curve, it is necessary to operate well-integrated societies and to know appropriative countermeasures of present situation of each societies. Also, for integrating regional medical insurance societies, it is necessary to continue more deep research through practical model activity and to investigate the effective size and managed method of the societies.societies.