• 대한두개안면성형외과학회지
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• 제22권5호
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• pp.232-238
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• 2021

Background: Galeal or temporalis muscle flaps have been traditionally used to reconstruct skull base defects after tumor removal. Unfortunately, these flaps do not provide sufficient vascularized tissue for a dural seal in extensive defects. This study describes the successful coverage of large skull base defects using anterolateral thigh (ALT) free flaps. Methods: This retrospective study included five patients who underwent skull base surgery between June 2018 and June 2021. Reconstruction was performed using an ALT free flap to cover defects that included the intracranial space and extended to the frontal sinus and cribriform plate. Results: There were no major complications, such as ascending infections or cerebrospinal leakage. Postoperative magnetic resonance imaging showed that the flaps were well-maintained in all patients. Conclusion: Successful reconstruction was performed using ALT free flaps for large anterior skull base defects. In conclusion, the ALT free flap is an effective option for preventing communication between the nasal cavity and the intracranial space.

• 한국전자파학회논문지
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• 제17권10호
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• pp.959-966
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• 2006

본 논문은 다이플렉서를 이용하여 디지털 셀룰라 대역($f_o$=880 MHz)과 IMT-2000 대역($f_o$=2,140 MHz) 기지국에서 동시에 사용 가능한 이중 대역 전치 왜곡 선형 전력 증폭기(Predistortion Linear Power Amplifier: PD LPA)의 설계 방법을 제시하였다. 입 출력단에 사용된 다이플렉서는 결함 접지 구조(Defected Ground Structure: DGS)를 이용한 저역 통과 여파기와 높은 Q값을 갖는 캐패시터와 마이크로 스트립 스터브를 이용한 고역 통과 여파기로 이루어져 있다. 입출력 반사 계수 특성을 좋게 하기 위하여 3 dB 하이브리드 결합기를 이용한 반사형 타입의 전치 왜곡 선형화기를 설계하였다. IS-95 CDMA IFA 신호와 WCDMA IFA 신호를 이용하여 각 대역에서 제작된 이중 대역 전치 왜곡 선형 전력 증폭기의 인접 채널 누설비(Adjacent Channel Leakage Ratio: ACLR) 개선 정도를 측정한 결과 880 MHz 대역에서 약 10 dB, 2,140 MHz 대역에서 약 9.36 dB 개선되었다.

• Journal of Korean Neurosurgical Society
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• 제58권1호
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• pp.36-42
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• 2015

Objective : Complete sellar floor reconstruction is critical to avoid postoperative cerebrospinal fluid (CSF) leakage during transsphenoidal surgery. Recently, the pedicled nasoseptal flap has undergone many modifications and eventually proved to be valuable and efficient. However, using these nasoseptal flaps in all patients who undergo transsphenoidal surgery, including those who had none or only minor CSF leakage, appears to be overly invasive and time-consuming. Methods : Patients undergoing endoscopic endonasal transsphenoidal tumor surgery within a 5 year-period were reviewed. Since 2009, we classified the intraoperative CSF leakage into grades from 0 to 3. Sellar floor reconstruction was tailored to each leak grade. We did not use any tissue grafts such as abdominal fat and did not include any procedures of CSF diversions such as lumbar drainage. Results : Among 200 cases in 188 patients (147 pituitary adenoma and 41 other pathologies), intraoperative CSF leakage was observed in 27.4% of 197 cases : 14.7% Grade 1, 4.6% Grade 2a, 3.0% Grade 2b, and 5.1% Grade 3. Postoperative CSF leakage was observed in none of the cases. Septal bone buttress was used for Grade 1 to 3 leakages instead of any other foreign materials. Pedicled nasoseptal flap was used for Grades 2b and 3 leakages. Unused septal bones and nasoseptal flaps were repositioned. Conclusion : Modified classification of intraoperative CSF leaks and tailored repair technique in a multilayered fashion using an en-bloc harvested septal bone and vascularized nasoseptal flaps is an effective and reliable method for the prevention of postoperative CSF leaks.

• Journal of Korean Neurosurgical Society
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• 제29권5호
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• pp.640-643
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• 2000

Objective : In neurosurgical practice, it has been generally accepted that when the dura is opened, it should be watertightly closed, and traditionally non-watertight closure has not been performed. We clinically tried non-watertight closure, analyzed the frequency of CSF leakage and evaluated the possible clinical application of non-watertight closure. Methods : After classifying our cases with supratentorial and infratentorial approach, we tried non-watertight and watertight closures and compared the results. We also analyzed the cases with or without dural graft. Results : In supratentorial approach, the rate of cerebrospinal fluid leakage noted in non-watertight closure was similar to that of watertight closure. In infratentorial approach, except microvascular decompression(MVD), the rate of cerebrospinal fluid leakage in non-watertight closure was higher than that of watertight closure. Dura graft application did not seemed to influence the cerebrospinal fluid leakage. Conclusion : Since the frequency of cerebrospinal fluid leakage was not higher in non-watertight closure than that of watertight closure, non-watertight closure can be applied in supratentorial approach. In infratentorial approach, non-watertight closure may be applied in surgery with relatively short dural incision, such as MVD. However, non-watertight closure doesn't seem to be appropriate in surgery that requires wide dural incision, such as skull base surgery.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.613-617
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• 2001

The test items like as endurance, air leakage and oil endurance test is requested for reliability evaluation about O-ring which is a kind of core machinery accessories of semi-conduct manufacturing equipment. For verification of these, we design and manufactured a test system for endurance, air leakage and oil endurance of O-ring for semi-conduct manufacturing equipment, and also performed the test for two kinds of O-ring, as it were Viton and Kalretz. The characteristics of this test equipment consist in realization of the test conditions of semi-conduct manufacturing equipment and satisfying the test method. The test conditions are cut gas, vacuum grade, temperature and revolution numbers in the endurance test system, vacuum grade and temperature in the air leakage test system, temperature and time in the oil endurance test system. The separating test results for wearing which is an oil endurance test item, the wearing index of domestic produced Viton O-ring is higher than foreign product by 2%, wearing rate of Kalretz O-ring better than Viton O-ring by 17%, and particles existed in various place. The test result of air leakage which is measured through the RGA sensor used Helium, the vacuum grade was $10^-3$Torr. And the test result of oil endurance, the volume change rate was 7~15%. Hereafter, we intend to analysis the reliability test evaluation and to utilize for domestic manufacturing companies by establishing data base and developing reliability softwares.

• 전기전자학회논문지
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• 제15권3호
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• pp.218-226
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• 2011

본 논문은 현재 유선방송 기술기준에서 CDMA 이동통신서비스 대역의 누설전자파 기준이 적절한지를 검증하고자 하였다. 먼저, CDMA 2000 1X 기지국 장비를 통한 실험결과로부터 CDMA 이동통신 시스템의 최대 허용 간섭 레벨은 -110dBm/1.23MHz인 것으로 분석되었다. 이를 토대로 이동통신기지국에 거의 영향을 주지 않을 케이블 방송 옥외 전송설비의 누설 간섭전력의 임계레벨과 누설전자파 세기를 산출하였다. 일반적으로 옥외에서 측정되는 외부시스템의 배경 간섭레벨인 -100~-80dBm/1.23MHz에 대해서 허용될 수 있는 케이블 방송 설비의 누설전자파 임계치는 현행 유선방송 기술기준을 만족시키지 못하였다. 이것은 현행 기술기준이 지나치게 최악의 경우를 상정하여 설정되었음을 의미하므로 이동통신사업자의 실제적인 기지국 조건을 적용하여 합리적인 기술기준을 마련하여야 할 것이다.

• 한국전기전자재료학회논문지
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• 제13권7호
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• pp.598-606
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• 2000

In this paper we investigated the relation between the surface degradations and anti-pollution characteristics of Room Temperature Vulcanized(RTV) silicone rubber coating that has different roughness through immersing into saline water. We utilized several analytic techniques such as atomic force microscopy(AFM) scaning electron microscopy(SEM) contact angle Salt Deposit Density(SDD) and average leakage current under the condition of salt fog. It is found that the surface roughness of treated RTV silicone rubber increased and the hydrophobicity of sample surface decreased with increasing the duration o immersion into water due to the erosion of base polymer the melting down alumina trihydrate(ATH) and the diffusion of Low Molecular weight(LMW) fluid. Despite the roughness of surface had been increased by water immersion excellant anti-pollution and recovery characteristics were maintained and SDD saturated to 0.1~0.14mg/cm$^2$. The average leakage current under salt fog increased with surface roughness. Measurement of average leakage current will be helpful to investigate surface degradation and lifetime expectation of RTV silicone coating.

• 대한기계학회논문집B
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• 제23권8호
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• pp.957-968
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• 1999

Performance tests of an airfoil fan and measurement of flow fields at the impeller exit are carried out to investigate the effects of the tip clearance between the rotor and inlet casing on the impeller performance. The impeller is twelve bladed of NACA 65-810 airfoils and tested with 3 different size of gap; 1, 2, 4mm. The relative decrease of pressure rising performance of the fan is 15 percent for the design flow rate when the gap size is 1 percent of the impeller diameter. The reduction of performance becomes large as the flow rate increases. The leakage flow through the clearance affects the through flow of the impeller, which results in decrease of the slip factor as well as the impeller efficiency. The data base obtained in the present study can be used for the design and flow analysis of the airfoil fans.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.21-23
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• 2007

It is well known that the characteristics of the induction machine depend on a great degree on the leakage reactance. And the leakage reactance is different according to a level of slant. So in this paper, we calculated the inductance per coil side. And the torque and speed characteristics are analyzed using a method base on the two-dimensional (2-D) finite element method (FEM) and on the circuits theory to model the rotor bar in a induction machine. The variable values of bar angle of slant are considered.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.272-278
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• 2006

This study is quantitatively assessing of safety about dispenser of hydrogen station because it is hydrogen energy to efficient safety use. The large leakage of hydrogen gas is the most important accident among others occurrence possibility in hydrogen station. It had written FT by top event and calculated unavailability, m-cutsets, leakage frequency, etc with FTA after each base event collect reliability data by reliability data handbook, THERP-HRA and estimation of the engineering.