• 소성∙가공
• /
• 제3권1호
• /
• pp.23-37
• /
• 1994

The upper bound element technique(UBET) is used to analyze the final stage of the axisymmetric forward extrusion. Kinematically admissible velocity field involving curved surface of velocity discontinuity is assumed. The required power to arise the piping defect is obtained and is compared with Aviture's solution a the same condition. Conditions for inception of the cavity and development of the pipe are predicted. The internal radius of the pipe and critical length of billet are also determined. Experiments are carried out for extrusion with lead specimens to investigate the piping phenomena. The theoretically predicted results showed reasonably good agreement with the experimental observation.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2007년도 추계학술대회 논문집
• /
• pp.217-220
• /
• 2007

본 논문에서는 이중 구조의 공동에서 작은 공동 내부에 존재하는 전자파원으로부터 방사되는 전자파를 내부 공동의 개구를 지나 외부 공동의 개구를 통해 방사될 때, 외부 공동의 개구 크기 변화에 따른 방사 전자파의 크기를 FDTD법으로 검토하고 있다. 외부 공동 개구의 크기는 최대 방사 전자파의 주파수를 결정하므로 개구의 크기를 조절하면 방사되는 전자파의 크기를 제어할 수 있음을 이론해석을 통하여 확인하고 있다.

• Tuberculosis and Respiratory Diseases
• /
• 제76권5호
• /
• pp.199-210
• /
• 2014

Pleural effusion is not a rare disease in Korea. The diagnosis of pleural effusion is very difficult, even though the patients often complain of typical symptoms indicating of pleural diseases. Pleural effusion is characterized by the pleural cavity filled with transudative or exudative pleural fluids, and it is developed by various etiologies. The presence of pleural effusion can be confirmed by radiological studies including simple chest radiography, ultrasonography, or computed tomography. Identifying the causes of pleural effusions by pleural fluid analysis is essential for proper treatments. This review article provides information on the diagnostic approaches of pleural effusions and further suggested ways to confirm their various etiologies, by using the most recent journals for references.

• 한국임상수의학회지
• /
• 제17권1호
• /
• pp.289-292
• /
• 2000

A Holstein cattle with third pregnancy was found to have clinical emergency findings of anxiety, dyspnea and recumbency at just before parturition. So Cesarean section and observation of internal organs were taken. Macroscopic examination showed enlargement of th lymph nodes and spleen, and ascites. A large tumor mass with solid and white to gray-white and focal hemorrhage, 55$\times$120cm in dimension and weighing 25.5kg was found in pelivc cavity. For conventional light microscopy, tissue samples were fixed in 10% neutral formalin solution, and then paraffin embedding, sectining and H-E staining were performed. In microscopic findings, tumor tissue, lymph node and spleeen were composed of mainly lymphoid tumor cells and the number of white blood cells in peripheral blood were increased 10-fold more than in normal. We concluded this tumor was bovine lymphoma.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.220-223
• /
• 2007

Acoustic test of the payload fairing of Korea satellite launch vehicle was conducted to verify the performance of acoustic protection system installed inside the payload fairing. This paper briefly introduces the acoustic test procedures and its results. Overall 148 dB acoustic loads were exerted on the payload fairing structures which mated with the upper stage structure of the launch vehicle. In order to verify the increase of insertion loss by the acoustic protection system, two kinds of test were performed. One is conducted with acoustic protection system and the other without acoustic protection system. Internal acoustic loads as well as external ones were measured and the measured insertion losses were compared with the requirement. The results showed that the acoustic protection system increases the insertion loss by more than 6 dB above 125 Hz. They also indicated that some design modification of Helmholtz resonator array is required to increase the insertion loss at a cavity resonant frequency.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 추계학술대회 논문집
• /
• pp.149-152
• /
• 2000

By using a three-dimensional finite element program HydroFORM-3D based on a rigid-plastic model, the hydroforming process for automobile subfrmae is analyzed in this study. The goal of this study is to accomplish preform design and determine the level of internal pressure for producing final hydroformed subframe component. Prior to hydroforming, the initial tube blank must be bent to the approximate centerline of the final part to enable the tube to be placed in the die cavity, After then, a preforming operation like stamping is carried out to the prebent tube. Finally, hydroforming process is performed to the preformed tube to get the final production. And through ductile fracture theory, the failure, bursting, is predicted during hydroforming process for tube blank with different diameter.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 춘계학술대회 논문집
• /
• pp.194-197
• /
• 2004

In the tube hydroforming process, a tube is placed into the die cavity and the ends of the tube are sealed by fixing the axial cylinder piston into the ends. Then the tube is pressurized with a hydraulic fluid and simultaneously the axial cylinders move to feed the material into the expansion zone. Therefore, the quantitative relationship between process parameters such as internal pressure and feeding amount and hydroformabillity, is hard to establish because of their high complexity and many unknown factors. In this study, the empirical and the quantitative relationship between process parameters and hydroformabillity are analyzed by fuzzy rules. Fuzzy expert system is an advanced expert system which uses fuzzy rule and approximate reasoning. Many process parameters are converted to the quantitative relationship by use of approximate reasoning of fuzzy expert system. The comparison between experimentally measured hydroformabillity from hydroforming experiments and the predicted values by fuzzy expert system shows a good agreement.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.102-105
• /
• 2000

A simple digital control system has been developed for the frequency stabilization of an internal mirror He-Ne laser. The system is based on one chip microprocessor with embedded Basic interpreter. To stabilize the laser output frequency, the signal such as power difference or beat frequency between two modes is supplied and processed by a microprocessor, and control signal is fed to the heating coil would round the laser tube for adjusting the spacing of the laser cavity mirror. Newly developed frequency stabilization system is totally digitized. The system and the frequency stability performance are briefly described.

• Journal of Chest Surgery
• /
• 제46권3호
• /
• pp.165-177
• /
• 2013

This is the third in a series on coronary artery bypass which reviews three alternative arterial conduits. The radial artery has become the most widely used of the three and accumulating experience demonstrates better patency at 10 years versus saphenous vein. Drawbacks are a long incision on the forearm, the propensity for spasm and persistent sensory disturbance in about 10%. The first is answered by endoscopic harvest which may yield a shorter conduit but reduces sensory nerve injury. Spasm is managed pharmacologically and by less harvest trauma. The gastroepiploic artery is used in situ and free and although the abdominal cavity is entered complications are minimal and patency compares favorably with the radial artery. Use of the inferior epigastric artery remains minimal and its similar length often requires composite use but limited patency data are supportive. Other arteries have had rare use and this is unlikely to change because the three presented here have significant advantages and acceptance.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1995년도 추계학술대회 논문집
• /
• pp.64-67
• /
• 1995

Transfer Molding is currently the most widely used process for encapsulation integrated circuits(;IC). Although the process has been introduced over 20 years ago, generating billions of parts each year, it is far from being optimized. With each new mold, epoxy mold, epoxy mold compound, and lead-frame, lengthy period and expensive qualification runs have to be performed to minimized defects ranging from wire sweep, incomplete fill, and internal voids etc. This studies describes how simulation can be applied to transfer molding to yield acceptable design and processing parameter. The non-isothermal filling of non-newtonian reactive epoxy molding compound(;EMC) in a multi-cavity mold is analyzed. Sensitivity analysis is conducted to investigate the influence of process deviations on the final molded profile. This study trend is carried out by following some heuristic process guidelines.