• 대한기계학회논문집A
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• 제27권4호
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• pp.524-530
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• 2003

This paper presents a new model on deformation characteristics of cylindrical tubes under pure bending. The model is based on the upper bound method that minimizes total strain energy of a system. It does not assume inextensibility condition. Geometric relations and displacement fields are derived by analysis of deformation behaviors of elastic tubes. Simulations are calculated using numerical optimization and integration techniques. The results give information about cross-sectional deformation of cylindrical tubes. Simulation results are compared with available data in literatures, which show that this method predicts deformation characteristics of tube bending process.

• 한국정밀공학회지
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• 제15권6호
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• pp.139-144
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• 1998

In Semi-Solid Forging, it is necessary to control the forming variables accurately in order to make near-net-shape products. Generally, the defects of products may occur due to liquid segregation which can be caused by the degree of deformation and strain rate, and condition of friction in Semi-Solid Forging, where the segregation is to be predicted by flow analysis. This paper presents the feasibility of theoretical analysis model using the new yield function for compressible P/M materials which is proposed by Doraivelu et at. to the flow analysis of the semi-solid dendritic Sn-15％Pb alloys instead of adopting the yield criterion of Shima and Oyane which is used by Charreyron and Flemings. The simple compression process is taken into consideration as the model to confirm the usefulness of the adopted yield function. The distribution of the liquid fraction at various strains and strain rates in radial direction, and the influence of friction are estimated by upper-bound method.

• 월간양계
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• 제48권1호
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• pp.129-131
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• 2016

부모 가업을 잇는 후계자들이 늘어나면서 양계인 2세대 경영인들의 조합 또는 조직화된 모임이 탄탄하게 결성돼 왕성히 활동하고 있다. 부모로부터 기술과 경영력을 물려받고, 축산 전문 교육 과정 수료 등 전문 지식 습득과 2세대 양계인들은 서로간의 정보 교류까지 더해져 보다 빠른 시대변화에 적응하고 경쟁력을 갖추고 있다. 산란계 분야에서는 2세대 법인 또는 조직적인 모임으로 대표적으로 경기도 광주 일대의 '다한영농조합법인'과 김포 일대의 '풍우동주'가 있으며 경상도 일대의 '대구경상계우회(이하 대경회)'가 요즘 핫한 산란계 2세대 양계인 모임이다. 2016년 신년을 맞아 대경회 회장이자 경북 칠곡군 소재 창일농장에서 부모의 가업을 이어 부모님과 함께 경영하는 이수고 대표를 만나 농장 운영과 대외 활동사항에 대해 인터뷰한 내용을 정리했다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.578-584
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• 2008

In this study, a extrusion process with torsion of the bottom die is investigated to improve the forming performance of conventional extrusion process. In the experiment, plasticine is used as a model material. The results of experiments are compared with the two numerical methods, the Experiment and the Finite Element Method(FEM). An attempt is made to link programs incorporating with the process variables obtained by commercial FEM software, DEFORM-3D a useful package. Numerical result is compared with experimental one. These results show that the torsional extrusion process is very useful process because this process can obtain the homogenous deformations.

• 대한기계학회논문집
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• 제13권3호
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• pp.330-336
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• 1989

본 연구에서는 상계해법을 이용하여 축대칭 후방압출에 있어서 압출하중뿐 아니라 소성변형역의 형상 및 비유동영역(dead metal zone)까지 에측이 가능한 단순하고 체계적인 이론해석법을 제안하고 이에 대한 실험을 수행하여 확인해 보고자 한다.

• 한국정밀공학회지
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• 제16권9호
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• pp.89-95
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• 1999

The compression behavior of semi-solid materials in studied from a viewpoint of yield criteria and analysis methods. To describe the behavior of materials in semi-solid state, several theories have been proposed by extending the concept of plasticity of porous compressible materials. in the present work, the upper-bound method and the finite element method are used to model the simple compression process using yield criteria of Kuhn and Doraivelu. Segregation between solid and liquid which cause defect of product is analysed for Sn-15%Pb alloy is compared with the experimental result of Charreyron et al..

• 임상이비인후과
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• 제29권2호
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• pp.321-326
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• 2018

Warthin's tumor is the second most common benign tumor of the parotid gland, which consists of epithelial and lymphoid components. Malignant change is known to be extremely rare. In Korean literature, only a case of low grade adenocarcinoma arising from Warthin's tumor was reported. For squamous cell carcinoma, there has never been reported in Korea. The authors report a case of squamous cell carcinoma arising from Warthin's tumor in a 77-year-old male, who was treated with primary resection. The patient is well without any recurrence or metastasis after 15 months of follow-up.

• 임상이비인후과
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• 제29권2호
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• pp.295-300
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• 2018

Pleomorphic liposarcoma is extremely rare in the head and neck region. It can be diagnosed by identifying multivacuolated lipoblast with pleomorphism. Most studies have reported that pleomorphic liposarcoma shows an aggressive behavior with poor prognosis. The treatment of choice is wide resection to ensure negative margin. The authors report a case of pleomorphic liposarcoma in a 67-year-old female, who was treated with primary resection of tumor and postoperative radiation therapy. The patient is well without any recurrence or metastasis after 1 year of follow-up.

• Journal of Rhinology
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• 제25권2호
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• pp.118-122
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• 2018

Epithelioid hemangioendothelioma is a rare vascular tumor with intermediate malignity and metastasis risk. It presents epithelioid cells with intracytoplasmic vacuoles and low mitotic activity. Its vascular nature can be confirmed by immunohistochemical studies (vimentin, CD31, CD34, and factor VIII). It is extremely rare in the nasal cavity, with only one case reported on the middle turbinate in Korea. The authors present a case of epithelioid hemangioendothelioma on the choana with a size of 2mm, which easily coult have been misdiagnosed as a blood clot.

• 한국정밀공학회지
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• 제12권11호
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• pp.91-97
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• 1995

In this study, a deformation model for the regular polygonal-shaped tubes from hollow-cylindrical billets is proposed and a kinematically admissible velocity field is obtained from this deformation model. The final stage upper-bound extrusion load and the average extruded length are determined by minimizing the total power consumption with respect to chosen parameters. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreement in average extruded height between theory and experiment.