• 대한기계학회논문집
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• 제14권1호
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• pp.1-12
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• 1990

본 연구에서는 자유단조용 프레서를 이용하여 돌출부가 있는 비대칭 중공형단 조 제품을 생산할 수 있도록 금형장치를 설계.제작하고, Fig.1에서 보는 바와 같이 경 사진 돌출부가 있는 비축대칭 복합단조에 UBET를 적용하여 해석하였다. 단조시편은 원주형태를 가지도록 하였다. 즉 원주형 소재가 요구되는 비축대칭 단조제품으로 변 형되는 과정에서 단조하중, 재료가 돌출부를 충만하도록 하는 유동특성, 재료가 돌출 부로 차들어가는 속도 등에 영향을 주는 인자(예:펀치 직경의 크기, 금형 상하면의 각 도)의 특성을 이론적으로 해석하고 실험으로 확인하였다.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.847-852
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• 2006

A fitting process carried out in the automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that applies heat in the outer diameter of a gear to a suitable range under the tempering temperature and assembles the gear and the shaft made larger than the inner radius of the gear. Its stress depends on the yield strength of a gear. Press fitting is a method that generally squeezes gear toward that of a shaft at room temperature by a press. Another method heats warmly gear and safely squeezes it toward that of a shaft. A warm shrink fitting process for an automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by the process produced dimensional change in both outer diameter and profile of the gear so that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of a warm shrink fitting process in which design parameters such as contact pressure according to fitting interference between outer diameter of a shaft and inner diameter of a gear, fitting temperature, and profile tolerance of gear are involved. In this study, an closed form equation to predict the contact pressure and fitting load was proposed in order to develop an optimization technique of a warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, thermal-structural coupled field analysis. Actual loads measured in the field have a good agreement with the results obtained from theoretical and finite element analysis and also the expanded amounts of the outer diameters of the gears have a good agreement with the results.

• Journal of Chest Surgery
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• 제24권5호
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• pp.451-458
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• 1991

We have observed 101 cases of recurrent spontaneous pneumothorax from Sep. 1979 to Dec. 1989 at the Department of Thoracic & Cardiovascular Surgery, College of Medicine, Inje University, Pusan Paik Hospital and the result obtained as follows. 1] Age range of patients was the first decade to seventh decade. Males outnumbered females by 6.7: l. One or two episodes of recurrent attack were noted in majority cases. 2] In distribution of the lesion sites, right side was 55 cases[55.4%], left 42 cases[41.9%], and bilateral 4 cases[3.0%]. 3] In clinical manifestations, abrupt onset of dyspnea was 78 cases[77.2%], chest pain 48 cases[47.5%], cough 9 cases[8.9%] and chest discomfort 8 cases[7.9%]. 4] Of 101 cases, 48 cases were associated with pulmonary tuberculosis and other cases were associated with subpleural bullae and blebs[26 cases], emphysema[7 cases], bronchiectasis[2 cases], lung cancer[1 case], and silicosis[1 case], 5] In 88 cases[87.2%] of patients, the magnitude of collapse was above 50% in plain chest film. 6] The interval of recurrence after last attack was frequently within 1 year. 7] In the management, closed thoracostomy with underwater-sealed drainage was applied in first recurrent 53 cases but 2nd recurrence was developed in 16 cases. In 52 cases, surgical management was applied. The pleurodesis with chemical agent[tetracycline] via chest tube was applied in 2 cases. Among 51 cases subjected to the open thoracotomy, pleural abrasion was performed in 3 cases, excision of bullae & blebs in 12 cases, wedge resection in 28 cases, lobectomy in 6 cases and wedge resection combined with lobectomy in 2 cases. In one case subjected to the median sternotomy, wedge resection on both lung apex was performed. 8] Postoperative complications were developed in 8 cases but not serious.

• 한국광물학회지
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• 제16권2호
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• pp.125-133
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• 2003

삼팔면체형의 스멕타이트계 사포나이트(saponite)를 천연 광물질인 활석을 이용하여 수열법에 의해 합성하였다. 출발물질은 활석에 $Na_2$$CO_3$를 첨가하여 공기중에서 $800^{\circ}C$로 가열한 후, 화학양론적 조성에 맞게 Al($NO_3$)$_3$$.$$9H_2$O 및 Mg($NO_3$)$_2$$.$ $6H_2$O 금속염 수용액를 첨가하였고, pH는 7∼12 범위내로 $NH_4$OH 수용액에 의해 조절하여 제조하였다. 수열반응 조건은 약 1리터의 수열반응 용기에서 $230^{\circ}C$, 압력은 25∼75 kgf/$\textrm{cm}^2$의 범위 내에서 10∼60시간이었다. 실험결과, 반응온도 및 회전속도를 230 $^{\circ}C$와 180 rpm으로 고정시킨 수열조건 하에서 반응시간, 반응압력, pH 조건을 각각 40시간, 25kgf/$\textrm{cm}^2$, 약 10으로 하였을 때, 그리고, 화학조성을 화학양론적 조성에 필요한 $Na_2$O의 양보다 200% 과량 추가하였을 때, 양호한 사포나이트가 합성되었다. 또한 압력을 75 kgf/$\textrm{cm}^2$까지 증가시켜도 결정도에 미치는 영향은 미미하였으며, 반응시간이 길수록 더 좋은 결정도를 나타냈다.

• Journal of Chest Surgery
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• 제18권3호
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• pp.446-455
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• 1985

A total and consecutive 156 patients have undergone cardiac valve surgery including 13 closed mitral commissurotomy, 13 open mitral commissurotomy, one mitral annuloplasty, 75 mitral valve replacement, one aortic annuloplasty, 24 aortic valve replacement, 3 tricuspid valve replacement, 25 double valve replacement and one triple valve replacement. 155 prosthetic valves were replaced in a period between September 1976 and August 1985. There were 68 males and 88 females with age range from 8 to 69 yrs [mean 36.5 yr]. Out of replaced valves, 61 was tissue valve including 54 Carpentier-Edwards, and 4 was mechanical valves including 74 St. Jude Medical, and the position replaced was 101 valves for mitral, 46 for aortic and 8 for tricuspid. Single valve replacement in 102 cases, double valve replacement in 25 cases [17 for AVR+MVR, and 8 for MVR+TVR], and only one case was noted in the triple valve replacement. Early mortality within 30 days after operation was noted in 11 cases [7%]; 7 after MVR, 2 after DVR, and each one after open mitral commissurotomy and mitral annuloplasty. Cause of death was valve thrombus, cerebral air embolism, low output syndrome, uncontrollable arrhythmia, parapneumonic sepsis, acute cardiac tamponade and left atrial rupture. 7 late deaths were noted during the follow-up period from 1 to 104 months [average 48 month]; three due to valve and left atrial thrombus formation, two due to CVA from overdose of warfarin, and each one due to congestive heart failure and chronic constrictive pericarditis, Anticoagulants after prosthetic valve replacement were maintained with warfarin, dipyridamole and aspirin to the level of around 50% of normal prothrombin time in 79 cases, and Ticlopidine with aspirin in 47 cases to compare the result of each group. There were 11 major thromboembolic episodes including 3 deaths in the warfarin group. Two cases of CVA due to overdose of warfarin was noted in the warfarin group. In the ticlopidine group, there was only one left atrial thrombus confirmed at the time of autopsy. Among the survived 138 cases, nearly all cases[136 cases] were included in NYHA functional class I and II during the follow-up period. In conclusion, surgical treatment of the cardiac valve disease in 156 clinical cases revealed excellent result with acceptable operative risk and late mortality. Prevention of thrombus formation with anti-platelet aggregator Ticlopidine has better result than warfarin group presently with no specific side effect such as bleeding or gastrointestinal trouble.

• 정보보호학회논문지
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• 제23권4호
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• pp.721-728
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• 2013

빅데이터는 오늘날 가장 각광받고 있는 데이터 수집 및 분석기술의 경향으로, 대량의 비정형 데이터 분석을 요구하는 다양한 분야에 접목되어 효용성을 인정받고 있다. 네트워크 트래픽 분석 역시 대량의 비정형 데이터를 다루는 분야로, 빅데이터 접목시 그 효과가 극대화될 수 있다. 따라서 본 논문에서는 고도의 보안이 요구되는 군 C4I망과 같은 내부망 환경의 침해사고 및 이상행위를 실시간으로 탐지하기 위한 빅데이터 기반의 네트워크 트래픽 분석 플랫폼(RENTAP)을 소개한다. 빅데이터 분석 지원을 위해 최근 각광받고 있는 오픈소스 솔루션들을 대상으로 비교 분석을 수행하였으며, 선정된 솔루션을 기반으로 고안된 최종 설계에 대해서 설명한다.

• 한국통신학회논문지
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• 제38A권12호
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• pp.1102-1109
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• 2013

블라인드 간섭 정렬 (Blind Interference Alignment: BIA) 기법은 기지국과 사용자 간의 채널 상태 정보(Channel State Information: CSI)가 부재한 상황에서도 최대의 다중화 (Degrees of Freedom: DoF) 이득을 얻을 수 있는 전송 방식이다. 하지만 BIA 기법은 다중화 이득의 극대화를 통해 높은 신호 대 잡음비 영역에서는 좋은 합 전송률 성능을 나타내는 반면, 신호 대 잡음비가 낮은 영역에서는 성능이 크게 열화되는 단점이 있다. 본 논문에서는 BIA 기법이 갖는 단점을 극복하기 위하여, BIA 기법과 수신 모드 선택 기법 기반의 단일 사용자 SISO 전송 기법을 신호 대 잡음비에 따라 적응적으로 사용하는 이중 전송 기법을 제안한다. 먼저, 각 전송 기법의 평균 합 전송률의 닫힌 형태를 유도하며, 이를 기반으로 신호 대 잡음비에 따라 각 사용자의 전송 기법을 선택하는 저 복잡도 알고리즘을 제안한다.

• Journal of Power Electronics
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• 제16권4호
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• pp.1513-1525
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• 2016

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.938-945
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• 2005

The microstructure evolution in hot forging process is composed of dynamic recrystallization during deformation as well as grain growth during dwell time. Therefore, the control of forging parameters such as strain, strain rate. temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. Modeling equations are developed to represent the flow curve. grain size. recrystallized volume fraction and grain growth phenomena by various tests. The developed modeling equations were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The large exhaust valve spindle (head diameter of 512mm) was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to each 1080 and 1150$^{\circ}C$. Numerical calculation was performed by DEFORM-2D. a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. In order to obtain the fine and homogeneous microstructure and good mechanical properties in forging. the FEM would become a useful tool in the simulation of the microstructure development. In forging, appropriate temperature, strain and strain rate and rapid cooling are required to obtain the fine grain microstructure The optimal forging temperature and effective strain range of Nimonic 80A for large exhaust valve spindle are about 1080$\∼$l120$^{\circ}C$ and 150$\∼$200$\%$.

• Journal of Chest Surgery
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• 제25권9호
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• pp.968-975
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• 1992

A clinical analysis was performed on 404 cases of the chest trauma who were admitted and treated at department of thoracic and cardiovascular surgery, Chung Ang University, Yong San Hospital during the past 8 years from July 1984 to April 1992. The results were as follows. 1. The sex ratio was 3: 1 with male predominence. 2. The common age groups were 3rd, 4th, 5th and 6th decades. 3. The most common chief complaint was chest pain[58.2%]. 4. Of 404 cases of chest trauma, 50 cases were resulted from penetrating injuries whereas 354 cases were from non penetrating injuries. The most common cause of the non penetrating injuries was traffic accident[234/354, 66.1%] and of the penetrating injuries were stab wound[47/50, 94%]. 5. The left thorax was the preferred site of chest trauma. 6. The range of hospital stay was from less than 1 week to over 6 weeks and the average duration was about 2 weeks. 7. The common chest trauma was rib fracture[51.6%] and others were simple contusion [18.8%], hemothorax[14.6%], hemopneumothorax[14.9%] and pneumothorax[8.7i]. The rib fracture was prevalent between 4th to 9th rib laterally. 8. There were 92 cases of associated injuries which were bone fracture[66/92, 71.7%], head injury[17/92, 18.5%] and abdominal injury[9/92, 9.8%]. 9. The methods of treatment were conservative management[58.6%], closed tho-racostomy[23.3%], open thoracotomy[3.4%] and others. 10. There were 28 cases[6.9%] of complication, such as pneumonia, atelectasis, emp-yema, respiratory failure and others. 11. The overall mortality was 2.5%[10 cases] and causes of death were hypovolemic shock, acute renal failure, adult respiratory distress syndrome, sepsis and multiple organ failure.