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      • KCI등재

        Sol-Gel 법을 이용한 칼슘-알루미네이트계 전자화물 박막의 제조와 특성

        김경훈,박주석,채재홍,서원선,소성민,김태관,김형순,이병하,Kim, K.H.,Park, J.S.,Chae, J.H.,Seo, W.S.,So, S.M.,Kim, T.K.,Kim, H.S.,Lee, B.H. 한국결정성장학회 2010 韓國結晶成長學會誌 Vol.20 No.6

        Sol-gel법을 적용하여 $12CaO{\cdot}7Al_2O_3$(C12A7) 전자화물 박막을 제조하기 위해 CaO-$Al_2O_3$ sol을 제조하여 dip 코팅법을 적용하여 quartz 기판에 박막을 형성하였으며 열처리를 통해 C12A7의 박막을 제조하였다. C12A7 상의 형성 $800^{\circ}C$에서 시작되었고 $1,200^{\circ}C$ 온도에서 1시간 열처리를 통해 치밀화된 박막을 제조할 수 있었다. 제조된 C12A7 박막은 부도체였지만 수소 환원 분위기 열처리를 통해 전기전도도를 나타내기 시작했으며 $1,200^{\circ}C$ 48시간 열처리 시 120 S/cm의 전기전도도를 나타내었다. The Calcium-aluminate electride thin films on the quartz substrates was coated by sol-gel process. The crystallization of the C12A7 thin film was observed at $800^{\circ}C$ and high density C12A7 thin film was achieved on heat treatment at $1,200^{\circ}C$ for 1 hour. The reduction heat treatment of C12A7 thin film could be converted from insulator to conductor and the electrical conductivity was 120 S/cm in the C12A7 thin film heat treated at $1,200^{\circ}C$ with $H_2$ gas for 48 hours.

      • KCI등재

        요양급여적정성 평가자료를 이용한 예방적 항생제 사용과 수술부위 감염 발생의 관련성 연구

        김경훈,박춘선,장진희,김남순,이진서,최보람,이병란,이규덕,김선민,염선아,Kim, Kyoung-Hoon,Park, Choon-Seon,Chang, Jin-Hee,Kim, Nam-Soon,Lee, Jin-Seo,Choi, Bo-Ram,Lee, Byung-Ran,Lee, Kyoo-Duck,Kim, Sun-Min,Yeom, Seon-A 대한예방의학회 2010 Journal of Preventive Medicine and Public Health Vol.43 No.3

        Objectives: To examine the prophylactic antibiotic use in reducing surgical site infection. Methods: This was a retrospective study for patients aged 18 years and older who underwent gastrectomy, cholecystectomy, colectomy, cesarean section and hysterectomy. The data source was quality assessment data of the Health Insurance Review & Assessment Service gathered from medical records of 302 national hospitals. Prophylactic antibiotic use was defined as: timely antibiotic administration or inappropriate antibiotic selection. We performed hierarchical logistic regression to examine the association between prophylactic antibiotic use and surgical site infection with adjustment for covariates. Results: The study population consisted of 16 348 patients (1588 gastrectomies, 2327 cholecystectomies, 1,384 colectomies, 3977 hysterectomies and 7072 cesarean sections) and surgical site infection was identified in 351 (2.1%) patients. The rates of timely antibiotic administration and inappropriate antibiotic selection varied according to procedures. Cholecystectomy patients who received timely prophylactic antibiotic had a significantly reduced risk of surgical site infection compared with those who did not receive a timely prophylactic antibiotics (OR 0.64, 95% CI=0.50-0.83), but no significant reduction was observed for other procedures. When inappropriate prophylactic antibiotics were given, the risk of surgical site infection significantly increased: 8.26-fold (95% CI=4.34-15.7) for gastrectomy, 4.73-fold (95% CI=2.09-10.7) for colectomy, 2.34-fold (95% CI=1.14-4.80) for cesarean section, 4.03-fold (95% CI=1.93-8.42) for hysterectomy. Conclusions: This study examines the association among timely antibiotic administration, inappropriate antibiotic selection and surgical site infection. Patients who received timely and appropriate antibiotics had a decreased risk of surgical site infection. Efforts to improve the timing of antibiotic administration and use of appropriate antibiotic are needed to lower the risk of surgical site infection.

      • 신뢰도를 요구하는 임베디드 시스템에서의 저전력 태스크 스케쥴링

        김경훈,김유나,김종,Kim, Kyong Hoon,Kim, Yuna,Kim, Jong 대한임베디드공학회 2008 대한임베디드공학회논문지 Vol.3 No.1

        In this paper, we provide an adaptive power-aware checkpointing scheme for fixed priority-based DVS scheduling in dependable real-time systems. In the provided scheme, we analyze the minimum number of tolerable faults of a task and the optimal checkpointing interval in order to meet the deadline and guarantee its specified reliability. The energy-efficient voltage level at a fault arrival is also analyzed and used in the recovery of the faulty task.

      • KCI등재

        LNG 냉열과 재생 유기 랭킨 사이클을 이용한 복합 사이클의 성능 특성 해석

        김경훈,정영관,한철호,KIM, KYOUNG HOON,JUNG, YOUNG GUAN,HAN, CHUL HO 한국수소및신에너지학회 2020 한국수소 및 신에너지학회논문집 Vol.31 No.2

        This paper presents a thermodynamic performance analysis of a combined cycle consisting of regenerative organic Rankine cycle (ORC) and liquefied natural gas (LNG) Rankine cycle to recover low-grade heat source and the cold energy of LNG. The mathematical models are developed and the system performances are analyzed in the aspect of thermodynamics. The effects of the turbine inlet pressure and the working fluid on the system performance such as the mass flow rates, heat transfers at heat exchangers, power productions at turbines, and thermal efficiency are systematically investigated. The results show that the thermodynamic performance of ORC such as net power production and thermal efficiency can be significantly improved by the regenerative ORC and the LNG cold energy.

      • KCI등재

        방전플라즈마 소결법을 이용한 고밀도 탄화 붕소 제조 및 기계적 특성

        김경훈,채재홍,박주석,김대근,심광보,Kim, Kyoung-Hun,Chae, Jae-Hong,Park, Joo-Seok,Kim, Dae-Keun,Shim, Kwang-Bo 한국결정성장학회 2007 韓國結晶成長學會誌 Vol.17 No.3

        방전플라즈마 소결법을 적용하여 탄화붕소 세라믹스를 제조하여 그 소결 특성, 미세 구조 및 기계적 특성을 평가하였다. 탄화붕소의 소결에 방전플라즈마 소결법을 적용하여 소결 조제의 첨가 없이 전통적인 소결법보다 낮은 온도에서 99% 이상의 완전 치밀화된 소결체를 제작할 수 있었으며, 탄화붕소 분말의 메탄을 세척을 통하여 분말 표면에 형성되어 있는 $B_2O_3$ 상을 사전에 제거함으로써 결정립의 조대화를 방지하여 균일한 미세구조의 형성을 유도할 수 있었으며 결과적으로 탄화붕소 소결체의 기계적 특성을 향상시킬 수 있었다. 특히 파괴인성의 경우 메탄을 세척을 통하여 30% 이상의 물성 향상을 달성하였다. [ $B_4C$ ] ceramics were fabricated by spark plasma sintering process and their sintering behavior, microstructure and mechanical properties were evaluated. Relative density of $B_4C$ ceramics were obtained by spark plasma sintering method reached as high as 99% at lower temperature than conventional sintering method, in addition, without any sintering additives. The mechanical properties of $B_4C$ ceramics was improved by a methanol washing process which can be removed $B_2O_3$ phase from a $B_4C$ powder surface. This improvement results ken the formation of homogeneous microstructure because the grain coarsening was suppressed by the elimination of $B_2O_3$ phase. Particularly, fracture toughness of the sintered specimen using a methanol washed powder improved over 30% compared with the specimen using an as-received commercial powder.

      • KCI등재

        Charlson 동반질환의 ICD-10 알고리즘 예측력 비교연구

        김경훈,Kim, Kyoung-Hoon 대한예방의학회 2010 Journal of Preventive Medicine and Public Health Vol.43 No.1

        Objectives: To compare the performance of three International Statistical Classification of Diseases, 10th Revision translations of the Charlson comorbidities when predicting in-hospital among patients with myocardial infarction (MI). Methods: MI patients ${\geq}20$ years of age with the first admission during 2006 were identified(n=20,280). Charlson comorbidities were drawn from Heath Insurance Claims Data managed by Health Insurance Review and Assessment Service in Korea. Comparisions for various conditions included (a) three algorithms (Halfon, Sundararajan, and Quan algorithms), (b) lookback periods (1-, 3- and 5-years), (c) data range (admission data, admission and ambulatory data), and (d) diagnosis range (primary diagnosis and first secondary diagnoses, all diagnoses). The performance of each procedure was measured with the c-statistic derived from multiple logistic regression adjusted for age, sex, admission type and Charlson comorbidity index. A bootstrapping procedure was done to determine the approximate 95% confidence interval. Results: Among the 20,280 patients, the mean age was 63.3 years, 67.8% were men and 7.1% died while hospitalized. The Quan and Sundararajan algorithms produced higher prevalences than the Halfon algorithm. The c-statistic of the Quan algorithm was slightly higher, but not significantly different, than that of other two algorithms under all conditions. There was no evidence that on longer lookback periods, additional data, and diagnoses improved the predictive ability. Conclusions: In health services study of MI patients using Health Insurance Claims Data, the present results suggest that the Quan Algorithm using a 1-year lookback involving primary diagnosis and the first secondary diagnosis is adequate in predicting in-hospital mortality.

      • KCI등재

        Methanol washing effects on spark plasma sintering behavior and mechanical properties of B4C ceramics

        김경훈,Jae Hong Chae,Joo Seok Park,Dae Keun Kim,심광보,이병하 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.4

        B4C ceramics were fabricated by a spark plasma sintering process and their sintering behavior, microstructure and mechanical properties were evaluated. The relative densities of B4C ceramics obtained by spark plasma sintering method reached were as high as a 99% at lower temperature than used in the conventional sintering method, in addition, without any sintering additives. The mechanical properties of B4C ceramics were improved by a methanol washing process which can remove B2O3 coatings from the B4C powder surface. This improvement results from the formation of a fine and homogeneous microstructure because the grain coarsening was suppressed by the elimination of the B2O3 coating. In particular, the fracture toughness of the sintered specimen using a methanol washed powder improved by more than 30% compared with the specimen using an as-received commercial powder. B4C ceramics were fabricated by a spark plasma sintering process and their sintering behavior, microstructure and mechanical properties were evaluated. The relative densities of B4C ceramics obtained by spark plasma sintering method reached were as high as a 99% at lower temperature than used in the conventional sintering method, in addition, without any sintering additives. The mechanical properties of B4C ceramics were improved by a methanol washing process which can remove B2O3 coatings from the B4C powder surface. This improvement results from the formation of a fine and homogeneous microstructure because the grain coarsening was suppressed by the elimination of the B2O3 coating. In particular, the fracture toughness of the sintered specimen using a methanol washed powder improved by more than 30% compared with the specimen using an as-received commercial powder.

      • KCI등재

        듀얼클러치 변속기의 쉬프트 포크에 관한 피로해석 연구

        김경훈,정종규,원종진,정재일,Kim, Kyounghoon,Jeong, Jongkyu,Won, Jongjin,Jeong, Jayil 한국자동차안전학회 2012 자동차안전학회지 Vol.4 No.1

        본 논문은 듀얼클러치 변속기 변속 메커니즘 개발을 위한 동역학적 시뮬레이션 해석 및 피로수명 해석에 관한 연구이다. 캠을 이용한 쉬프트 포크의 이송으로 기어를 변속하는 개념을 갖는 쉬프트 메커니즘의 작동성 및 설계안 검증을 위해 캠의 회전 속도, 접촉면의 경계조건 및 싱크로나이저 슬리브에서의 저항을 반영한 모델링을 구성하여 동역학적 시뮬레이션을 실시하였다. 각 파트의 응력 및 변형률 발생을 해석하여 설계 개선안을 도출하고, 개선안이 반영된 최종 시작모델의 시뮬레이션 상 최대 응력 발생 시점에서 시프트 포크의 각 접촉면 별 외력 작용을 분석하여 이를 적용한 피로 해석을 진행하였다.

      • KCI등재

        EGML 기반 이동 객체 검출 알고리듬의 하드웨어 구현

        김경훈,안효식,신경욱,Kim, Gyeong-hun,An, Hyo-sik,Shin, Kyung-wook 한국정보통신학회 2015 한국정보통신학회논문지 Vol.19 No.10

        영상에서 움직임이 있는 객체 영역을 검출하기 위한 이동 객체 검출(moving object detection; MOD) 알고리듬을 EGML(effective Gaussian mixture learning) 기반 배경 차분 방법을 적용하여 하드웨어로 설계하였다. EGML 계산 일부의 근사화를 통해 하드웨어 복잡도를 줄였으며, 파이프라이닝 적용을 통해 동작속도를 개선하였다. Verilog-HDL을 이용하여 하드웨어를 설계하였으며, MATLAB/Simulink와 FPGA가 연동된 FPGA- in-the-loop 환경에서 하드웨어 동작을 검증하였다. 설계된 MOD 프로세서는 XC5VSX95T FPGA 디바이스에서 2,218 슬라이스로 구현되었으며, 102 MHz의 클록 주파수로 동작하여 102 MS/s의 처리율을 갖는 것으로 평가되었다. IEEE CDW-2012 데이터 세트의 12가지 영상에 대해 MOD 프로세서의 성능을 분석한 결과, 평균 recall 값은 0.7631, 평균 precision 값은 0.7778, 그리고 평균 F-measure 값은 0.7535로 각각 평가되었다. A hardware implementation of MOD(moving object detection) algorithm using EGML(effective Gaussian mixture learning)- based background subtraction to detect moving objects in video is described. Some approximations of EGML calculations are applied to reduce hardware complexity, and pipelining technique is adopted to improve operating speed. The MOD processor designed in Verilog-HDL has been verified by FPGA-in-the-loop verification using MATLAB/Simulink. The MOD processor has 2,218 slices on the Virtex5-XC5VSX95T FPGA device and its throughput is 102 MSamples/s at 102 MHz clock frequency. Evaluation results of the MOD processor for 12 images in the IEEE CDW-2012 dataset show that the average recall value is 0.7631, the average precision value is 0.7778 and the average F-measure value is 0.7535.

      • KCI등재

        콘크리트 혼합타설시 품질확보 방안

        김경훈,이상학,Kim, Kyung-Hoon,Lee, Sang-Hak 한국건축시공학회 2018 한국건축시공학회지 Vol.18 No.3

        콘크리트의 특징은 그 품질을 확보함에 있어서 시멘트, 모래, 자갈, 물, 혼화재료 등 구성재료 개개의 품질 및 그 배합비 그리고 생산관리 및 시공관리, 양생 등에 의해 영향을 받는다는 점이다. 콘크리트 배합설계에 따라 시공연도와 강도가 변화하게 된다. 대부분의 건설현장은 동일구간에 여러 레미콘 회사의 제품을 동시에 타설하는 것이 일반적이나 표준시방서에는 혼합타설을 원칙적으로 금지하고 있으며 필요시 책임기술자의 확인을 받도록 규정되어 있다. 이 연구는 불가피한 혼합타설시 콘크리트 품질확보를 하기 위한 방안을 제시하고자 하였으며, 연구방법은 문헌검토, 설문조사를 통하여 혼합타설의 문제점을 파악하고 불가피함을 확인하였으며, 사례현장의 콘크리트 타설계획과 군산지역의 레미콘 회사의 현황을 통하여 혼합타설의 문제점을 파악하고 불가피함을 확인하였다. 혼합타설을 하지 않는 방법으로 5가지 안을 제시하여 그 중에서 지역별 표준배합설계를 작성하여 동일한 배합비로 11개 레미콘 회사로 하여금 생산하도록 하여 혼합타설의 위험성을 배제하였으며 그 과정의 문제점을 제시하였다. 향후 연구과제로는 본 연구를 통하여 검증되지 않은 방안인 레미콘 회사의 규모확장 및 통폐합, 혼합타설된 콘크리트의 품질 추적조사, 혼화제의 상응성테스트 그리고 콘크리트 강도의 조기판정기법의 개발 및 골재등의 재료 통일방안등을 연구하여 혼합타설시 피해를 최소화할 수있도록 해야 할 것이다. Concrete mix design controls the various concrete properties such as workability and strength. Fresh concrete requires workability and the hardened concrete requires compressive strength. If using the concrete from different supplier concurrently, the concrete placed can show different properties unlike originally designed. However most of construction sites place the concrete from several companies. One of the predictable problems is whether the ultimate performance of concrete achieves the originally designed performance after placing the concrete from several companies. Therefore this research aims to keep the concrete quality in the above cases. This research has been done through literature review, questionnaire and the verification at the sample construction site. A literature review describes the general characteristics and quality control of concrete and a questionnaire describes the awareness and implementation of Korean Construction Specification(KCS). The production capacity and the delivery capacity of concrete suppliers is smaller than the daily quantity required on the sample site, therefore the placing of the concrete with different mixing ratio is inevitable and it can not keep the KCS. As a conclusion, this research proposed 5 alternatives and one of them has been adopted, i.e. to unify the concrete mix design of multiple concrete suppliers.

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