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현철 경성대학교 환경문제연구소 2000 環境硏報 Vol.10 No.1
Soil is ecological and healthful material. Specially loess among soil is more effective. The producing places of loess are common under the mountain surface. The purpose of this study is to investigate development of concrete adding soil as admixture. This study shows characteristics of compressive strength, fluidity, autogenous shrinkage and abaibatic temperature rise according to the replacement ratios of loess powder and W/C ratio through experiment. In this study, It is reported that the concrete of mixing ratio 5% of loess is most effective. The results obtained are as follows, 1)In case of normal temperature curing and mixing ratio 5% of loess, the compressive strength of concrete is similar to the case without loess. Generally, compressive strength of concrete decrease according to increase of mixing ratio of loess. 2)In case of normal temperature curing and mixing ratio 5% of loess, the fluidity of concrete is nearly equal to the case without loess. Generally, fluidity of concrete decrease according to increase of mixing ratio of loess. 3)In case of W/C ratio 40% and mixing ratio 5% of loess, the autogenous shrinkage of concrete is similar to the case without loess. But in case of W/C ratio 35%, autogenous shrinkage of concrete grow according to increase of mixing ratio of loess. 4)It is proved that abaibatic temperature rise of concrete considerably decrease with increase of mixing ratio of loess.
측두엽 간질로 인정된 환자들의 MRI와 EEG에 대한 ICTAL SPECT의 Sensitivity와 Specificity
현철호 ( Chul Ho Hyun ),김병수 ( Byung Su Kim ) 대한임상검사과학회 1998 대한임상검사과학회지(KJCLS) Vol.30 No.2
The efficacy of MRI, CCTV -EEG monitoring and ictal SPECT for the localization of seizure foci was evaluated in 21 patients with temporal lobe epilepsy. Ictal and interictal Tc-99m-Ethyl Cysteinnate Dimer(ECD) cerebral perfusion SPECT images of 21 patients were processed to get parametric subtracted images. Epileptogenic foci of 17 patients among 18patients were diagnosed by seizure free state after resection of epileptogenic zones. we found epileptogenic zones in substraction SPECT and compared with visual diagnosis of ictal and interictal MRI, CCTV -EEG monitoring and SPECT. The sensitivity was 100%, the specificity was 14 of 15(93%) in CCTV -EEG monitoring and ictal SPECT. The sensitivity was 100%. the specificity was 14 of 15(94%) in MRI and ictal SPECT.
사후 경과시간의 추정: 야외에 노출된 돼지사체를 이용한직장 온도의 하강평가
현철호,심경양,김나진,윤신규,송태화 한국과학수사학회 2017 과학수사학회지 Vol.11 No.2
변사체의 사후경과시간(PMI)을 추정하기 위한 시도의 한 방법으로 돼지사체를 이용하여 직장(直腸)의 온도변화를 관찰한 결과는 다음과 같다. 초기에 직장체온의 하강은 일정시간 체온을 유지하는고원평정상태를 보이다가 비교적 일정한 비율로 하강하면서 대기온도와 같아진다. 그러나 고원평정상태의 유무와 유지시간 등은 여전히 불명확하다. 이러한 고원평정상태의 불명확함은 체온의 하강을 이용하는 모든 사후경과시간 측정 방법에서 여전히 가장 중요한 오차의 원인이다. 이에 본 연구에서는 돼지사체 주변의 온도와 직장체온의 하강을 관찰한 바 직장체온과 상관성이 높은 온도는 사체와 지면의 온도로 관찰되었으며 고원평정상태는 모든 실험군에 있어서 짧게는 1시간 30분에서 길게는 6시간 50분으로관찰되었다. 그리고 대기온도와 직장체온이 역전되는 시점은 19시간 18분에서 41시간 26분으로 관찰되었다.
현철 慶星大學校 1999 論文集 Vol.20 No.1
The purpose of this paper is to investigate gravity, strength, emissivity, incombustibility and heat conduction property in order to verify utility of loess pannel. The results obtained are as followes ; 1) Specific gravity of loess pannel is 0.88 in case of normal temperature curing and mixing ratio 45% of foaming agent. It is profitable to light-weight property and production cost. 2) Heat conduction ratio of loess panel is 0.271 W/mK. 3) Pore volume increase in proportion to mixing volume of fiber and cohesion agent for tension strength reinforcement. It is unfavorable to workability and strngth. 4) 3 hours curing( 80℃) is enough to harden loess pannel.
현철봉(Zhefeng Xuan),김태렬(Tailie Jin),구남서(Nam Seo Goo),배병운(Byung-Woon Bae),김태흔(Tae-Heun Kim),고한서(Han Seo Ko),윤기원(Ki-Won Yoon) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.1
집적형 하이브리드 구동장치는 적층형 압전재료(압전스택)를 이용한 마이크로 펌프에서 토출되는 유체로 피스톤을 구동시키는데 크기는 작으면서도 큰 구동력과 높은 속도를 동시에 출력할 수 있는 새로운 개념의 통합 구동장치로서 현재 소형화 및 고출력을 요구하는 항공 우주, 유도무기 등 다양한 분야에서 광범위하게 연구되고 있다. 본 연구에서는 이러한 하이브리드 구동장치의 구동원리 및 성능 시험에 대해 소개하였다. 우선 구동장치의 주 동력인 압전 스택의 성능 시험을 수행함으로써 압전 스택의 구동전력과 구동시간에 따른 성능 변화를 관찰하였고 다음 구동장치의 성능 시험을 통해 구동장치의 최대 이송속도와 최대 구동력을 측정하였다. 구동장치의 최대 이송속도는 53.3 ㎜/s로, 최대 구동력은 240.7 N으로, 최대 일률은 3.2 W로 측정되었다. The piezoelectric-based hydraulic actuator is a hybrid device consisting of a hydraulic pump driven by piezoelectric stacks that is coupled to a conventional hydraulic cylinder via a set of fast-acting valves. Nowadays, such hybrid actuators are being researched and developed actively in many developed countries by requirement of high performance and compact flight system. In this research, operation principle and performance testing of the hybrid actuator were introduced. Output velocities have been measured in both loaded case and not loaded case and the blocking force also has been measured in external loaded case. The maximum velocity of the actuator is 53.3 ㎜/s, blocking force is 240.7 N and corresponding power output is 3.2 W.