지정석관리를 위한 효율적 시스템 개발

오현식 ( Hyun Sik Oh ),현정민 ( Jeong Min Hyun ),정진승 ( Jin Seung Jeong ),이학인 ( Hak In Lee ),정규영 ( Gyu Young Jeong ),소대화 ( Dea Wha Soh ) 한국동굴학회 2007 동굴 Vol.77 No.-

From the computer or the library the use of the place about lower the case which gives a damage to the different person occurs with four three anger backs. It became from the hazard which manages the library place efficiently it used the AVR and a RF communication to make a system.

CT AAPM 팬텀의 슬라이스 두께, 공간분해능, 저대조도분해능의 MATLAB을 이용한 정량적 분석 방법에 관한 연구

오현식(Hyun Sik Oh),이건호(Kun Ho Lee),정일천(Il Chun Chung) 대한CT영상기술학회 2015 대한CT영상기술학회지 Vol.17 No.1

Purpose : During the performance evaluation for CT device, it presents the objective data structured with the evaluated results quantified by computer using the MATLAB program for over coming the differences among testers that can occur on spatial resolution, low contrast resolution, and slice thickness (5 mm and 10 mm). Methods and Materials : We performed the quantitative analysis using MATLAB for slice thickness, spatial resolution, and low contrast resolution with the 50 received images which have suitable judgement by scanning AAPM phantom using GE, PHILIPS, SIEMENS, and TOSHIBA Slice thickness and spatial resolution were measured by using full width at half maximum(below FWHM). Spatial resolution was confirmed that FWHM interval more than 1.0 mm size. Low contrast resolution was measured that how close by using Roundness Index(below RI) until 6.4 mm size. The spatial resolution 9 images and low contrast resolution 10 images which have disapproved judgement were also had the quantitative analysis. The statistic analysis was judged to have statistically significant differences when p-value is less than 0.05 through SPSS statistics 19.0 and T-test (paired t-test). Results : For slice thickness 5 mm, the average qualitative evaluation group shows 4.98 mm and quantitative evaluation group shows 5.02. For slice thickness 10 mm, the average qualitative evaluation group shows 9.98 mm and quantitative evaluation group shows 9.86. No significant differences(p=0.07, p=0.06) with 5 mm and 10 mm. It confirmed the interval for all FWHM until 1.75, 1.50, 1.25, 1.00 mm as approved images on spatial resolution, and the average distance was 0.102 mm and the minimum distance 0.054 mm. For disapproved images, all interval was not showed under 1.00 mm. For low contrast resolution, spproved image’s RI value shows average 0.81 and minimum 0.77. The disapproved image’s RI average shows 0.70. Statiscally significant differences were presented (all p<0.05) following hole size. Conlusion : When slice thickness did not show statiscally significant differences for qualitative and quantitative tests, quantitative test usning MATLAB could be useful. When measured spartial resolution, it should be approved if interval distance shows over 0.05mm. For low contrast resolution, it is considered to meet circle 80% condition as qualitative test if RI value shows over 0.77. because of that, the method of this study should be standard to judge phantom image apprevemnet and considered to use secondary method for inspection oragization. 목적 : CT장치의 성능평가시 공간분해능, 저대조도분해능, 슬라이스 두께(5 mm 및 10 mm)에 발생할 수 있는 검사자간의 차이를 극복할 수 있도록 MATLAB 프로그램을 이용하여 컴퓨터로 정량화한 평가결과를 구조화한 객관적이 데이터로 제시하고자 한다. 대상 및 방법 : GE, PHILIPS, SIEMENS, TOSHIBA 로 AAPM phantom 스캔을 하여 얻은 적합판정을 받은 50개의 영상으로 슬라이스 두께, 공간분해능, 저대조도 분해능을 MATLAB으로 이용하여 정량적인 분석을 하였다. 슬라이스 두께와 공간분해능은 full width at half maximum(이하 FWHM)을 이용하여 측정하였다. 공간분해능은 1.0 mm 크기 이상에서 FWHM의 interval이 있는지를 확인하고 합격여부를 확인하였다. 저대조도분해능은 6.4 mm 크기까지 Roundness Index(이하 RI)를 이용하여 원형에 얼마나 가까운지를 측정하였다. 부적합 판정을 받은 공간분해능의 9개 영상과 저대조도분해능 10개의 영상도 정량적인 분석을 하였다. 통계분석은 SPSS statistics 19.0 을 통해 T-test(paired t-test) 을 통해 p-value가 0.05 미만일 때 통계적으로 유의차이가 있다고 판정하였다 결과 : 슬라이스 두께가 5 mm 에서는 정성적 평가군 평균이 4.98 mm, 정량적 평가군에서는 5.02 mm 로 나타났으며 10 mm 에서는 정성적 평가군 평균이 9.98 mm, 정량적 평가군에서는 9.86 mm 로 나타났고 5 mm 와 10 mm 모두 유의한 차이(p=0.07, p=0.06)가 없었다. 공간분해능에서는 적합판정 영상에서는 1.75, 1.50, 1.25, 1.00 mm 까지는 모두 FWHM에서 interval이 확인되고 평균거리는 0.102 mm 이고 최소거리는 0.054 mm 였다. 부적합판정 영상에서는 1.00 mm 이하에서는 모두 interval이 나타나지 않았다. 저대조도분해능에서는 적합판정 영상의 RI 값 평균은 0.81 이었고 최소값은 0.77이었다. 부적합판정 영상의 RI 값 평균은 0.70 으로 나타났다. 구멍의 크기에 따라서 통계적으로 유의한 차이(모두 p<0.05)를 나타났다. 결론 : 슬라이스 두께는 정성적인 평가와 정량적인 평가에서도 통계적으로 유의한 차이를 나타나지 않았으므로 MATLAB을 이용한 정량적인 방법이 유용하다고 생각된다. 공간분해능 측정시 interval 거리가 0.05mm 이상이면 적합이라고 판정 할 수 있다. 저대조도분해능에서는 RI 값이 0.77이상이면 정성적인 평가인 원형의 80% 조건을 만족시킬 수 있을 거라고 생각되어진다. 따라서 본 연구에서 제시한 방법이 팬텀 영상의 적합 여부를 판단하는데 있어서 일정한 기준이 될 수 있으며 검사기관에서 보조적인 수단으로 활용할 수 있다고 사료된다.

X-CARE 사용시 안구와 유방의 선량 감소 효과와 영상 평가에 관한 연구

오현식(Hyun Sik Oh),유형태(Hyung Tae Yoo),남윤철(Yoon Cheul Nam),김문찬(Moon Chan Kim),한동균(Dong Kyoon Han) 대한CT영상기술학회 2011 대한CT영상기술학회지 Vol.13 No.2

목적 감수성이 높은 표재성 장기인 안구와 유방의 선량감소 효과가 있는 X-CARE를 대상으로 두부와 흉부 검사 시 선량감소효과와 영상의 화질을 평가하여 보고하고자 한다. 대상 및 방법 CT 장비는 Siemens사의 Dual Source Somatom Definition Flash를 사용하였으며, organ dose 측정을 위해 Female Alderson Radiation Therapy Phantom과 유리선량계를 사용하였다. 두부 검사시 안구의 표면, 두부 전면부, 후면부에서 측정하였으며, X-CARE를 사용하지 않을 때와 사용했을 때의 선량을 각각 2번씩 측정하여 비교하였다. 흉부 검사시에는 유방과 흉부의 전면부, 중간부, 후면부의 선량을 AEC 모드의 사용여부에 따라서 X-CARE를 사용하지 않을때와 사용했을 때의 선량을 각각 2번 측정하여 비교하였다. 영상의 화질 평가는 ACR 팬텀을 사용하여 얻어진 영상을 ImageJ 분석 프로그램을 이용하여 직선성과 균일도를 평가하였다. 통계분석은 Minicab을 통해 2 Sample t-test로 분석하여 선량의 유의성을 확인하였다. 결과 두부 검사시 안구의 표면선량과 전면부 선량은 X-CARE의 사용전에 비해 사용후에는 35.2%, 14.6% 감소하였으며, 후면부에서는 9.1% 증가하였다. 흉부 검사에서 AEC를 적용하지 않으면서 X-CARE를 사용하면 사용 전에 비해 유방, 흉부 전면부, 중간부의 선량은 각각 30.0%, 11.3%, 3.8% 감소하여 유의한 선량감소를 타나냈다(p<0.05). 그러나 후면부에서는 13.6%로 증가하였다. AEC를 적용하면서 X-CARE를 사용하면 사용전에 비해 유방, 흉부 전면부의 선량이 27.8%, 11.0% 감소하여 유의한 감소 효과를 나타냈다(p < 0.05). 그러나 흉부중간부와 후면부에서는 각각 1.4%, 4.5% 증가하였다. 영상의 화질 평가는 직선성과 균일도 모두 ACR에서 정한 기준 범위에 포함되었다. 결론 X-CARE는 영상의 화질 변화 없이 감수성이 높은 표재성 장기인 안구와 유방에 선량 감소 효과를 나타낼 수 있는 방법으로 여성과 소아 검사에 있어서 적극적인 사용을 권고한다. I. Purpose To measure absorbing dose reduction and evaluate image quality by glass dosimeter to eyeball and breast which are high sensitive superficial organs when examining head and chest using X-CARE. II. Meterial and Methods Dual Source Somatom Definition Flash of Siemens Company was usedfor the CT scan and Female Alderson Radiation Therapy Phantom and glass dosimeter were used for organ dose evaluation. ACR phantom was used for image quality evaluation and program Minicab was used for statistics analysis. For organ dose evaluation, we compared eyeball skin dose during head exam and the dose examined two times whether using X-CARE or not to the frontal and occipital partial of the head. For chest exam, we compared the dose examined two times whether using X-CARE or not to breast dose and the frontal, middle, rear side of chest following to use AEC mode or not. Using image j analysis program, we evaluated the linearity and uniformity the image gotten by ACR phantom. Through out Minitab, we confirmed dose significance by analyzing 2 Sample r-test. III. Result For dose evaluation of head exam, eyeball skin dose and the frontal dose show 35.2%, 14.6% reduction comparing before use and after use, the rear side shows 9.1% growth. To not apply AEC of chest exam, after use of X-CARE show the breast front, middle, rear dose were decreased 30.0%, 11.3%, 3.8% and the rear side increased 13.56% comparing before use. To apply AEC,however, after use of X-CARE show the breast dose and the frontal dose shows 27.8%, 11.0% reduction and the middle and rear side shows 1.4%, 4.5% growth. For image quality evaluation, it contains the standard range of ACR phantom The dose evaluated at the head shows all small differences(p < 0.05) and the breast dose and the front and rear side show small differences(p < 0.05), the middle partial shows no small differences(p > 0. 05) without the use of chest AEC. When the breast does and the frontal dose show small differences(p < 0.05) with the use of AEC, the middle and rear side show no small differences(p > 0. 05). IV. Conclusions X-CARE is the good way to show to eyeball and breast which are high sensitive superficial organswithout the image changing I think.

궤적 성형을 통한 극초음속 활강 비행체 모델링 및 시뮬레이션

오현식(Hyun-Shik Oh),김윤식(Yoon Sik Kim),이순주(Sun Ju Lee),노성규(Sungkyu Noh) 한국항공우주학회 2022 한국항공우주학회 학술발표회 논문집 Vol.2022 No.4

부적법한 부동산의 평가기준

오현식 ( Hyun Shik Oh ),방경식 ( Kyung Sik Bang ) 한국감정평가학회 2009 감정평가학논집 Vol.8 No.2

Real estate environment has continuously changed on account of the variability of social, economic and administrative status as one of the humane characteristics. All of them are factors which can influence property values, and such value determinating factors are the main target to analyse surely in the process of appraisal which is the nature of quest for how value forms and how value produces. This time around, there are legally nonconforming properties by laws legislation or revision placed on them resulting from the changeability of administrative status which can be seen as one of the peculiarity of real estate. These can come in many forms and can affect the land, buildings, or the uses of the property. The highest and best use principle is based on the premise that it is legitimate state under current laws. It raises theoretical and practical questions about how to establish related concepts, where the hierarchy location be, and how final value reflection does on legally nonconforming property by appraisal theory evaluated on the basis of the highest and best use principle about legally nonconforming property. The purpose of this study is to establish a new definition of legally nonconforming property which has yet to be systemized, and is to present the standards of appraisal of legally nonconforming property which has always created challenges in the appraisal process. The results of this study are as follows: It establishes a clear definition of legally nonconforming property. It surveys value analysis in violation of the existing regulations of the building-to-land ratio through case study of legally nonconforming property. Finally, it presents standards of appraisal of legally nonconforming property. The process is for the purpose of solving the disorientation of property appraisers.

K-IFRS 부동산 공정가치 평가의 문제점과 대응방안

오현식 ( Hyun Shik Oh ),노용호 ( Yong Ho Noh ),방경식 ( Kyung Sik Bang ) 한국감정평가학회 2011 감정평가학논집 Vol.10 No.2

Recently, Fair Value Measurement has been issued. It is very important for success of IFRS Adoption to valuate Fair Value objectively. Therefore, there is a very urgent need to investigate the differences between Appraisal theory and Accounting measurement. If there are any problems to practice Fair Value Measurement, We have to find alternatives for that. The purposes of this research is to suggest alternatives for the problems which may occur when applying Fair Value Measurement of K-IFRS to real estate valuation. Ultimately, it is to achieve a good international reputation. Fair value measurement of real estate for a financial accounting report has a very low level in systems and contents in comparison to Appraisal Businesses. Therefore, the role of appraisers is more important than before. The findings are as follows : First, it is necessary to define the meanings of fair value and market value in order to avoid the confusion in concepts. Second, appraisers need to ensure the objectivity and professionalism of fair value valuation. Third, a variety of valuation approaches and international collaboration is required to build the reliability of fair value valuation. Fourth, it will be helpful to issue fair value valuation manuals and show materials to the public to improve the insufficient disclosure of financial accounting reports.

논 문 : 부동산 감정평가서의 신뢰성과 질 향상

오현식 ( Hyun Shik Oh ),방경식 ( Kyung Sik Bang ) 한국감정평가학회 2010 감정평가학논집 Vol.9 No.1

This paper examines the quality of appraisal reports for credibility and impartiality. The purpose of appraisal is to estimate the value of the subject property. The logical analysis and value estimating process should be fully described in appraisal reports. So that, the clients could rely on the credibility of appraisal through more reasonable and understandable appraisal reports. Korean appraisal standards, data element items on foreign appraisal standards and reports, content analysis, and the Supreme Court``s precedents relevant to data element of appraisal reports was analyzed for a logical explanation. There have been few discussions on the research of appraisal reports on quality in Korea. This research is to gain implications for effective methods of appraisal reports writing by analyzing present appraisal standards in Korea and referential articles in Appraisal Journal(USA). These findings are as follows. The analysis from mandatory data element of Korean appraisal standards indicates that Korean appraisal report needs details and logical construction. There are a few suggestions for improvement. Firstly, appraisal reports should be clarified types and details of value in valuation. Secondly, appraisal reports should contain effects of value and its reflecting degree by assumptions and conditions of valuation. Thirdly, appraisal reports should contain analysis details of real estate appraisal principles such as highest and best use, etc.. Morality, professionalism, and impartiality are prerequisite for writing appraisal reports. It is advisable to take the identification of purpose, the concretion of contents, and communicability in writing appraisal reports for credibility into consideration.

ODM과 bismuth를 이용한 수정체와 갑상선 선량 감소 효과 및 영상 화질 평가

이승현(Seung Hyun Lee),오현식(Hyun Sik Oh),김완역(Wan Yuk Kim),장광현(Kwang Hyun Chang) 대한CT영상기술학회 2016 대한CT영상기술학회지 Vol.18 No.2

Purpose : It is to know the method of the limiest dose reduction of lens and Thyroid which is comparative high sensitivity with the implementation of the best images during head and neck exam by using ODM(Organ Dose Modulation, ODM) that is AOBCM(automated organ current modulation) by GE manufacture company, AEC(Automatic exposure control) and bismuth. Materials and Methods : CT equipment is used Discovery CT 750HD(General Electric Medical System, Milwaukee, Wisconsin USA), and Alderson Rando phantom(CNMC Company, USA) is used with attached Radiophoto Luminescent Glass Dosimeter five to head and six to neck for dose measurement using tour methods(AEC, ODM, bismuth, ODM+bismuth) with 10 times scan and acquired average value. Also to evaluate image quality, we used noise and CT number, and to measure linearity and uniformity by using ACR phantom (Model #438, Gamex RMI, USA). Statistic is used MedCalc version 16.1 to have average and standard deviation of all measurement values, and it could be judged statistically when p-value under 0.05 by AVOVA test. Result : The standard by the usage of AEC, the measured dose result shows that lens were ODM 19.2%, bismuth 32.9%, ODM and bismuth 46.7% down, and to Thyroid shows that ODM 31.2%, bismuth 24.9%, ODM and bismuth 56.8% down. To evaluate image quality for noise, lens shows that ODM 7.1 %, bismuth 17.7%, ODM and bismuth 13.3% increase, to Thyroid shows that ODM 10.1 %, bismuth 30.0%, ODM and bismuth 36.9% increase, for CT number values, lens show that ODM 0.3%, bismuth 50.0% and ODM+bismuth 48.8% increase, to Thyroid shows that ODM 1.9% down, bismuth 296.2%, ODM and bismuth 305.8% increase. To evaluate using ACR phantom, for the usage of bismuth, linearity and uniformity were out of tolerance field recommended ACR because of artifact, by ODM case was under tolerance field for ACR recommendation. To judge statistical significance test, as the result of dose, noise and CT number values by ANOVA test, we confirmed that all results were significant with p-value< 0.05. Conclusion : When using ODM, it was known that dose could be reduced over 25% and increased noise, but continued CT number. Also, neck which is lower thickness compared head shows low noise changes and CT number values continuation. Through this result, it is considered that ODM is more effective method for dose reduction and image quality to less thickness area. 목적 : GE사에서 개발한 자동장기기준선량제어장치(automated organ current modulation, AOBCM) 인 ODM(Organ Dose Modulation, ODM)과 자동노출제어장치(Automatic exposure control, AEC), 그리고 비스무스(bismuth)를 이용하여 두경부 검사 시 최고의 영상을 구현하면서 상대적으로 감수성이 높은 장기인 수정체와 갑상선의 선량을 최소로 낮추는 방법을 찾아보고자 한다. 대상 및 방법 : CT장비는 Discovery CT 750HD(General Electric Medical System, Milwaukee, Wisconsin USA)를 사용하였고, 선량측정을 위해 Alderson Rando phantom(CNMC Company, USA)을 이용하여 두부에 5개, 경부에 6개씩 형광유리선량소자를 이용하여 AEC, ODM, bismuth, ODM+bismuth 4가지 방법으로 10회 scan하여 평균값을 구하였다. 또한 화질평가를 위해 noise와 CT number값을 이용하여 평가하였으며, 영상평가를 위해 ACR phantom(Model #438, Gamex RMI, USA)을 사용하여 직선성과 균일성을 측정하였다. 통계는 MedCalc version 16.1을 사용하여 모든 측정치의 평균과 표준편차를 구하였으며, AVOVA로 통계분석 하여 유의확률(p-value)가 0.05 미만일 때 통계적으로 유의하다고 판단하였다. 결과 : AEC를 사용한 경우를 기준으로 선량을 측정한 결과 수정체는 ODM 19.2% bismuth 32.9% ODM과 bismuth 46.7% 감소하였고, 갑상선은 ODM 31.2%, bismuth 24.9%, ODM과 bismuth 56.8% 감소하였다. 화질평가를 위해 측정한 noise값의 경우 수정체는 ODM 7.1%, bismuth 17.7%, ODM+bismuth 13.3% 증가하였고, 갑상선은 ODM 10.1%, bismuth 30.0%, ODM+bismuth 36.9% 증가하였으며, CT number값의 경우 수정체는 ODM 0.3%, bismuth 50.0%, ODM+bismuth 48.8% 증가하였으며, 갑상선은 ODM 1.9% 감소하였고 bismuth 296.2% ODM+bismuth 305.8% 증가하였다. ACR phamtom을 이용한 영상평가에서는 bismuth를 사용하였을 경우 Artifact로 인해 직선성과 균일성 모두 ACR에서 권고하는 허용범위에 속하지 않았으며, ODM을 사용한 경우에는 ACR에서 권고하는 허용범위에 속하였다. 통계적 유의성을 판단하기 위하여 ANOVA test로 각각의 선량, noise, CT number값을 검정한 결과 모든 측정값이 p-value<0.05 미만으로 유의하다고 판단하였다. 결론 : ODM을 사용하였을 경우 선량은 25% 이상을 감소시키면서 noise 값은 증가하지만 CT number값은 유지됨을 알 수 있다. 또한 두부보다 상대적으로 두께가 얇은 경부의 경우 noise값은 변화가 적으면서 CT number값은 유지됨을 알 수 있다. 이를 통해 ODM은 두께가 얇은 부위에 선량감소 및 영상평가에 더욱 효과적이라 사료된다.

차량용 열교환기의 납작관의 열유동 성능평가

강희찬(Hiechan Kang),오현식(Hyun-sik Oh),전길웅(Gilwoong Jun),김광일(Kwangil Kim),정순안(Sunan Jung) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

The present work was performed to investigate friction and heat transfer inside flat tubes having high aspect ratios for automobile applications. The pressure drop and heat transfer coefficients for laminar, transition and turbulent flow regimes were measured and discussed. The transition flow regime was observed at the Reynolds numbers 900-4,000. The pressure drop coefficients were 15% higher for the laminar flow and 12% higher for the turbulent flow than the theoretical predictions. The present experimental data for the flat tube were higher than those for the circular tube.

딤플에 의한 루우버휜 열교환기의 공기측 압력강하, 열전달 및 배수 성능향상

강희찬(Hiechan Kang),오현식(Hyun-sik Oh),임무기(Moogi Lim),공태윤(Taeyun Kong),박성욱(Sungwook Park),정순안(Sunan Jung) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

The present study proposed a dimpled louver fin by adding dimpled slots between the end region of louver fin and the brazing line of the flat to reduce flow resistance and enhance drainability. Numerical simulations were conducted for the conjugated heat transfer of 2 kinds of fin geometry by using the commercial CFD code. The drainability was tested for the four enlarged plastic models made by the rapid prototype machine. The dimpled louver fin showed 14% less airflow pressure drop coefficient than the baseline louver fin, the advantage increasing at low air velocity. The dimpled louver fin shows up to 5% higher than the baseline fin in the performance index of the heat transfer capability per unit temperature potential for the same fan power. The dimpled louver fin drained water better and held substantially less than the baseline fin in the deep test.