• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.2
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• pp.96-105
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• 1992

The objective of this paper is to study experimentally on the noise characteristics of supersonic jet from multihole orifice in the range of jet pressure from $at_g$ to $at_g$ in the reverberation room. At first, the single orifice jets are investigated for various hole diameter from 3.8mm to 10mm. Through the noise spectrum, the turbulent mixing noise and the shock associated noise is analyzed. The noise for confined jets into a tube of diameter 30mm or 90mm with length 2m is investigated in comparision with that for the free jets. The sound power level is measured and compared with thoretical models for free jet. At second, multihole orifice jets are investigated to study the effect of multijet on noise reduction. The spectrum and power level of multijets are measured and compared with single jets. The multi-jets in a confined pipe are also investigated. It is found that the noise spectrum is significantly altered by increasing the number of jet with decrease in jet diameter and also by confining the jet into tube.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.431-438
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• 2011

Flame lift-off conditions determine the operating conditions of burners. It is known that a flame can be lifted when the Schmidt number (Sc), which is the ratio of the dynamic viscosity to the mass diffusivity, is greater than unity. In this study, the flame lift-off characteristics of non-premixed flames of propane (Sc > 1) and methane (Sc < 1) in a coaxial outer air tube were experimentally compared. The experimental results indicated that stable lifted flames could be obtained even when Sc < 1 in a confined air tube. On the basis of the results of a simple numerical analysis, it was confirmed that a new flame stabilization mechanism exists in the tube. A velocity field is preferentially developed upstream of the flame, and it results in a new stabilization condition. This result can be very useful in explaining the stabilization of the flames of ordinary burners in which a flame is produced in a confined space.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.64-70
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• 1985

Fully Reynolds Stress model is applied to predict recirculation pattern, velocity and Reynolds shear stress distributions in a circular jet coaxially confined in a round pipe. It is found that the generation of velocity region depends on Curtet number(Ct). It is also found that the Reynolds shear stress and velocity distributions in the inital jet region depend strongly on the Curtet number up to about X/D = 2.0 but they are almost independent of the Curtet number further downstream.

• Korean Journal of Animal Reproduction
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• v.23 no.1
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• pp.45-51
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• 1999

The morphological study was carried out to classify the spermatogenic germ cells of the seminiferous tubule in Korean Native Pheasant during the breeding season. The results were as follows : 1. The spermatogonia can be classified into the three types of A, In(intermediate) and B. 2. The primary spermatocyte can be classified into the five types as preleptotene, leptotene, zygotene, pachytene and diakinesis. 3. The maturing processes of nucleus of spermatid can be divided into seven steps. The round shape of the spermatid was changed to the elongated form during the spermiogenesis. This observation may be useful to the study of the breeding cycles in the Korean Native Pheasant.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.342-345
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• 2008

산재 발생 시 산재근로자는 근로복지공단을 통해서 각종 급여를 받게 된다. 본 논문은 심사 과정과 급여지급 후에 부정수급으로 판명된 산재 청구 건을 데이터 마이닝을 통해서 분석하여 부정수급의 유형을 발견하고자 한다. 이 연구에서는 서울관내 4개 지사에서 8년 동안(2000년$\sim$2007년)의 총 61,536명의 최초요양 신청을 한 산재근로자 자료를 대상으로 하였고, 종속변수에 영향을 미치는 8개의 독립변수를 선택해서 사용한다. 데이터 마이닝을 적용함에 있어서 가장 효율적인 허위 부정 탐지 모델을 만들기 위해 의사결정나무분석(Decision Tree)과 로지스틱 회귀분석(Logistic Regresion)등의 다양한 기법을 적용하여 결과를 비교분석 하고, 오분류 비용을 적용하여, 최적의 분류결정 값을 가지는 모델을 도출한다. 분석결과, 로지스틱 회귀분석이 산재보험 부정수급 유형 발견에 보다 효과적인 모델로 판명되었다. 또한 판별점(Cut-Off) 0.01로 했을 때 4개변수(요양기간, 업종형태, 의료기관, 재해발생형태)가 부정수급에 탐지하는데 영향력이 큰 변수로 선정되었다.

• Radiation Oncology Journal
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• v.21 no.1
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• pp.35-43
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• 2003

Purpose :To analyze the survival period, prognostic factors and complications of patients having undergone high-dose-rate intraluminal brachytherapy (HDR-ILB) as a salvage radiation therapy, while having a catheter, for percutaneous transhepatic billary drainage (PTBD), inserted due to biliary obstruction caused by a secondary malignant biliary tumor Methods and Materials : A retrospective study was performed on 24 patients having undergone HDR-ILB, with PTBD catheter Insertion, be)ween December 1992 and August 2001. Their median age was 58.5, ranging from 35 to 82 years. The primary cancer site were the stomach, gallbladder, liver, pancreas and the colon, with 12, 6, 3, 2 and 1 cases, respectively. Eighteen patients were treated with external beam radiation therapy and HDR-lLB, while slx were treated with HDR-lLB only. The 4otal external beam, and brachytherapy radiations dose were 30$\~$61.2 and 9$\~$30 Gy, with median doses of 50 and 15 Gy, respectively. Results : Of the 24 patients analyzed, 22 died during the follow-up period, with a median survival of 7.3 months. The 6 and 12 months survival rates were 54.2 (13 patients) and 20.8$\%$ (5 patients), respectively. The median survivals for stomach and gailbladder cancers were 7.8 and 10.2 months, respectively, According to the unlvariate analysis, a significant factor affecting survival of over one year was the total radiation dose (over 50 Gy) (o=0.0200), with all )he patients surviving more than one year had been Irradiated with more than 50 Gy. The acute side effects during the radiation therapy were managed with conservative treatment. During the follow-up period, 5 patients showed symptoms of cholangltis due to the radiation therapy Conclusion :An extension to the survival of those patients treated with HDR-ILB is suggested compared to the median historical survival of 4hose patients treated with external biliary drainage. A boost radiation dose could be effectively given, by performing HDR-lLB, which is a prognostic factor In addition, the acute complications of radiation therapy were effectively controlled by conservative management, and It could be regarded as a safe treatment.

• Journal of Korea Multimedia Society
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• v.9 no.9
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• pp.1131-1138
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• 2006

This paper proposes a novel method for grading of underground communication conduits by laser projection image analysis. The equipment thrust into conduit consists of a laser diode, a light emitting diode and a camera, the laser diode is utilized for generating projection image onto pipe wall, the light emitting diode for lighting environment and the image of conduit is acquired by the camera. In order to segment profile region, we used a novel color difference model and multiple thresholds method. The shape of profile ring is represented as a minimum diameter and the Fourier descriptor, and then the pipe status is graded by the rule-based method. Both local and global features of the segmented ring shaped, the minimum diameter and the Fourier descriptor, are utilized, therefore injured and distorted pipes can be correctly graded. From the experimental results, the classification is measured with accuracy such that false alarms are less than 2% under the various conditions.

• Journal of the Korea Society of Computer and Information
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• v.26 no.3
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• pp.19-28
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• 2021

Esophagogastroduodenoscopy is a method commonly used for early diagnosis of upper gastrointestinal lesions. However, 10-20 percent of the gastric lesions are reported to be missed, due to human error. And countries including the US, the UK, and Japan, the World Endoscopy Organization (WEO) suggested guidelines about essential gastrointestinal parts to take pictures of so that all gastric lesions are observed. In this paper, we propose deep learning techniques for classification of anatomical sites, aiming for the system that informs practitioners whether they successfully did the gastroscopy without blind spots. The proposed model uses pre-processing modules and data augmentation techniques suitable for gastroscopy images. Not only does the experiment result with a maximum F1 score of 99.6%, but it also shows a error rate of less than 4% based on the actual data. Given the performance results, we found the model to be explainable with the potential to be utilized in the clinical area.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.9-9
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• 1998

가스터빈 연소기의 난류유동장을 구성하는 기본적인 유동형태는 크게 밀폐관내의 돌연 확대를 가지는 동축제트, 선회유동, 그리고 연소공기공 및 회석공기공을 통해 연소실에 수직방향으로 유입되는 제트유동 등으로 분류할 수 있다. 실제 가스터빈 연소기내의 난류유동장을 수치해석하기 위해서는 임의의 형상을 갖는 3차원 유동장을 모사할 수 있는 수치해석법과 고차정확도를 유지하면서도 수렴안정성을 만족시키는 대류항 처리기법 등과 같은 수치모델의 개발이 선행되어야 하며, 이와 함께 복잡한 난류연소유동장을 정확히 묘사할 수 있는 난류모델 및 난류연소모델의 개발 및 검증이 가장 중요한 요인이 된다. 또한 가스터빈 연소기의 최적 설계는 넓은 작동구간에서 높은 효율, NOx 및 CO 배기량의 저감, 희박연소 가연한계의 확장, 연소계통에서의 낮은 압력강하, 낮은 연소벽면온도와 온도구배를 유지시키기 위한 공기에 의한 충분한 냉각 같은 서로 상충되는 설계조건을 만족해야 한다. 그리고, 이러한 상충된 연소설계조건들을 충족시키는 최적 연소기의 설계를 위해서는 실험적인 연구뿐만 아니라 연소기내의 물리적인 현상을 잘 반영할 수 있는 물리적 모델을 바탕으로 한 연소유동의 해석적인 연구를 필요로 한다. 본 연구에서는 원통형 가스터빈 연소기의 등온 및 연소유동장, 그리고 연소기와 연결되는 Scroll 내부의 난류유동장에 대한 수치해석을 수행하여 수치 및 물리모델의 예측능력을 검증하였고, 가스터빈 연소유동장 해석에 관련된 중요 논점들에 대하여 심도있게 분석하였다.

• Radiation Oncology Journal
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• v.9 no.2
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• pp.253-263
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• 1991

Twenty-seven patients with unresectable extrahepatic bile duct carcinoma (n=21) or with microscopic evidence of tumor rest after aggressive surgery for extrahepatic bile duct carcinoma (n=6) between 1985 and 1990 were given radiotherapy consisting intentionally external radiotherapy and/or intraluminal therapy using Gamma-Med 12i (192-Ir) high dose rate (HDR) remote control afterloading system following bile drainage procedures and Gianturco stent insertion. The objectives of this study has been to assess the feasibility and effects on survival of a combination of external radiotherapy and brachytherapy with which we hope to achieve optimal loco-regional control for patients with unresectable extrahepatic bile duct tumors. Sixteen patients were men and eleven were women, and the mean age was 58 years (34-70). 10MV X-ray was used for radiation therapy, with the total dose ranging from 45 Gy to 55 Gy, and intraluminal brachytherapy performed after external radiotherapy, with the dose of total 15 Gy. The minimum follow up was 12 months. Failure were predominantly local-regional, without distant failure. Median survival was 10 months; 2-year actuarial survival rates was $21\%$. Median survival for common hepatic duct (CHD) cancer was 9 months; for common bile duct (CBD) cancer, was 16 months. And median survival for incomplete surgery/external radiotherapy group and external/intraluminal radiotherapy group was 10 months; for external radiotherapy alone group, was 6 months. Use of chemotherapy and/or hyperthermia were not affected in survival. Therefore, our result is that the survival rates in the group of external/intraluminal radiotherapy were comparable with ones in the group of incomplete resection/external radiotherapy, and so we believe that the aggressive local and regional radiotherapy can improve the quality of life and the survival length.