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      • 板材와 單板의 熱板乾燥에 關한 硏究

        鄭希錫 서울大學校 農科大學 1979 서울대농학연구지 Vol.4 No.1

        Current rapid increase in the wood demand promotes utilization of fast-growing species and small diameter log as timber resources. These woods have a greater proportion of juvenile wood in their volume, and are unstable in dimension due to anisotropy in shrinkage than mature wood. It is understood that severe drying defects could occur with conventional drying. The present studies aimed to elucidate characteristics on drying such as the core temperature, current moisture content, moisture gradient, drying rate, drying time, dimensional change and drying defect of board, and drying rate of veneer for an efficient utilization of timber resources. Species selected for the study were poplar(P. euramericana G.) as a fast-growing species and oak(Q. acutissima C.) as refractory wood. The condition of press-drying adopted was that of platen temperature of 175℃ and pressure of 2.46 kilogram per square centimeter with board thickness of 7, 15 and 24 milimeters. For veneer experiment, the conditions adopted were of temperature of 110℃, 120℃ and 130℃ and pressure of 2.46 kilogram per square centimeter, and veneer thickness of 0.6, 1.2 and 1.8 milimeters. The results of the study are summarized as follows. 1. The core temperature of board thicker than 15 milimeters was divided into three stages of drying : the period of initial heating, the period of the stable core temperature and the period of the slowly rising core temperature. On the other hand, the board with 7 milimeters thick did not show the period of the stable core temperature. 2. The plateau temperature of thicker board was lower and kept longer than that of thinner board. For the board with same thickness, the plateau temperature for end-grained board was lower and kept longer than the temperature for flat-grained board. 3. The average moisture content of thicker board was lower than that of thinner board when the core temperature was reached at 150℃. For the board with same thickness and the same core temperature of 130℃, the average moisture content of end-grained board was lower than that of flat-grained board. 4. The variation of the moisture content in relation to the drying time showed a curvilinear, and that of thinner board changed much faster than that of thicker board. For the board with same thickness the drying rate of end-grained board was greater than that of flat-grained board. 5. The moisture gradient in board was great at the beginning stage of drying, but decreased as the drying was progressed. 6. The drying rate of flat-grained boards showed a positive correlation with the initial moisture content, platen temperature and the pressure applied, but a negative correlation with the board thickness and drying time. 7. The drying time of flat-grained boards showed a positive correlation with the board thickness and initial moisture content, but a negative correlation with platen temperature, pressure and final moisture content. 8. The drying rates of poplar flat-grained boards treating with cold water, hot water and steam were greater than that of controlled(untreated) specimen. 9. The thickness shrinkage of boards for press-drying increased as the drying was progressed. The thickness shrinkage of edge-grained boards was greater than that of flat-grain, and its shrinkage of end-grain was the least. The width of edge-and flat-grained boards expanded as the drying was progressed, but in contrast the end-grained board shrank. 10. The thickness shrinkage of edge-and flat-grained boards increased with pressure applied. The thickness recovery of edge-grained board in relation to pressure variation showed significant difference, but that of flat-grain showed no significant difference. 11. Except for board with high moisture content and drying condition of higher platen temperature and higher pressure, poplar flat-grained boards dried without a serious drying defect such as surface check, honeycomb and collapse. The end-grained board was also showed no significant drying defects. 12. Drying defects of sapwood board was milder than that of heartwood. Drying defects of oak heartwood with steaming treatment reduced the amount of drying defects as compared to those with cold water and hot water treatments. 13. The drying rate of veneer was decreased as drying was progressed. The tinner veneer thickness and higher platen temperature, the greater the drying rate was.

      • 선박 안전을 위한 선내 모니터링 시스템 구축

        정희석 한국항해항만학회 2017 한국항해항만학회 학술대회논문집 Vol.2017 No.추계

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

        선박의 안전운항을 위해, 선내 센서데이터 수집장치를 설치하여 선박의 항해/기관 데이터를 수집하고, 수집된 데이터를 이용하여 긴급상황레벨 결정 및 위기대응 가이던스를 제공한다. 선박에서 수집된 데이터는 LTE-M 망을 이용하여 육상으로 전송하는 시스템을 개발한다. 선데 데이터 수집장치는 IEC 61162-1 표준으로 항해통신 장비들의 데이터를 수집하고, 기관부 데이터는 Moubus로 데이터를 수집한다. 수집된 데이터는 UDP로 육상 송수신 장치로 데이터를 전송한다.

      • KCI등재

        자가팽창성 금속 담도스텐트의 동맥손상에 의한 지연성 대량 혈담즙증의 중재적 치료

        정희석,신태범,황재철,배재익,김창원 대한영상의학회 2012 대한영상의학회지 Vol.66 No.1

        목적: 악성 담도폐쇄 환자에서 고식적 치료로 이용되는 자가팽창성 금속스텐트에 의한 동맥손상과 동반된 지연성 대량 혈담즙증에 대한 중재적 치료술의 효과에 대하여 알아보고자 하였다. 대상과 방법: 최근 8년간 악성 담도폐쇄 환자 중 자가팽창성 스텐트에 의한 동맥손상과 동반된 지연성 대량 혈담즙증이 발생한 8명을 대상으로 하였다. 스텐트 설치술과 대량의 혈담즙증 발생기간은 평균 66.5일(15~152일)이었다. 기저질환은 췌장암 2예, 간문부담도암 2예, 담도암 2예, 간내담도암 1예, 위암의 담도침범 1예였다. 혈관조영술에서 손상된 동맥의 가성동맥류 6예, 조영제의 혈관 외 유출 1예, 손상혈관부 연축 1예였다. 8명 중 4명에서 손상된 혈관에 대하여 미세코일, 1명에 대하여 히스토아크릴을, 1명에 대하여 미세코일과 히스토아크릴을 이용하여 색전술을 시행하였다. 간문맥의 폐쇄가 확인된 2예의 환자에서는 간동맥색전술시 간부전의 가능성이 있어 병변부에 스텐트 그라프트를 시행하였다. 결과: 8명 모두에서 성공적으로 지혈을 시행하였다. 시술과 연관된 합병증은 없었으며 8명의 환자생존기간 중에 재출혈은 발생하지 않았다. 결론: 악성 담도폐쇄 환자에서 고식적 치료로 시행하는 스텐트 설치술에 의한 동맥손상에 의한 지연성 대량 혈담즙증은 혈관 내 중재적 시술로 효과적인 치료가 가능하다. Purpose: To evaluate the effectiveness of interventional management for delayed and massive hemobilia secondary to arterial erosion self expandable metallic stent (SES) in with biliary duct malignancy. Materials and Methods: Over 8-year period, eight patients who suffered from de¬layed massive hemobilia after SES placement for malignant biliary obstruction as palliative procedure, were included. The mean period between SES placement and presence of massive gastrointestinal hemorrhage was 66.5 days (15-152 days), pancreatic cancer (n = 2), Klatskin tumor (n = 2), common bile duct cancer (n = 2), intrahepatic cholangiocarcinoma (n = 1), and gastric cancer with ductal invasion (n = 1). Angiographic findings were pseudoaneurysm (n = 6), contrast extravasation (n = 1) and arterial spasm at segment (n = 1). Six patients underwent embolization of injured vessels using microcoils and N-butyl cyanoacrylate. Two patients underwent stent graft placement at right hepatic artery to prevent ischemic hepatic damage because of the presence of portal vein occlusion. Results: Massive hemobilia was successfully controlled by the embolization of ar-teries (n = 6) and stent graft placement (n = 2) without related complications. Conclusion: The delayed massive hemobilia to arterial erosion metallic biliary stent is rare this complication be successfully treated by interventional management.

      • KCI등재

        Alternative Surgical Methods in Patients with Recurrent Palmar Hyperhidrosis and Compensatory Hyperhidrosis

        정희석,이두연,박준석 연세대학교의과대학 2018 Yonsei medical journal Vol.59 No.2

        Recurrent hyperhidrosis after thoracic sympathectomy is an uncomfortable condition, and compensatory hyperhidrosis (CH) is one of the most troublesome side effects. Here, we describe two patients with recurrent palmar hyperhidrosis (PH) and CH over the whole body simultaneously. They were treated with bilateral T4 sympathetic clipping and reconstruction of the sympathetic nerve from a T5 to T8 sympathetic nerve graft, which was transferred to the resected T3 sympathetic bed site. They reported improvementsin sweating and were fully satisfied with the results. Our method can be considered as an alternative approach for patients with recurrent PH and CH.

      • 디오비팅 태양돛 제작 및 전개 실험

        정희석,김상호,김승진,방인혁,심연보,강석현,소윤민,이병철,정주현,노진호 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4

        본 논문에서는 디오비팅 태양돛을 설계 및 제작하고 전개 특성을 살펴보고자 한다. 태양돛 구조 지지를 위하여 “Ω” 형상의 복합재료 붐을 제작하였고 수납 및 전개 가능성을 살펴보았다. DC 모터를 이용하여 정확한 전개속도를 제어하였고, Miura-ori 방법을 이용하여 두께가 얇은 Kapton 필름을 효과적으로 접고 다시 펼쳐지게 하였다. 태양돛의 전개 시연을 통하여, 향후 디오비팅 장치의 적용 가능성을 살펴보고자 한다. In this research, the fabrication procedures and the deployment characteristics of the de-orbiting solar sails are demonstrated. The “Ω” shaped cross section composite boom is designed and fabricated for the support structure of the sail. Deployment displacement and speed are controlled with a DC motor and an ultra-thin film of Kapton is efficiently folded and deployed using the Miura-ori method. Moreover, the potential application for the de-orbiting devices using solar sails should be discussed.

      • KCI등재

        수중 센서 네트워크에서 수심, 수온, 염도를 고려한 환경에서 MDS를 이용한 위치인식 연구

        정희석,김은찬,양연모,Jung, Hui-Sok,Kim, Eun-Chan,Yang, Yeon-Mo 대한임베디드공학회 2012 대한임베디드공학회논문지 Vol.7 No.4

        In these days, there are huge increases of concerning underwater acoustic sensor networks (UWASNs) to explore marine resources and to monitor climate change. To collect information from sensor nodes which are randomly deployed in underwater, Multi-Dimensional Scaling (MDS) based locating methods have been recently introduced, which consider sound speed to be constant in underwater. However, underwater sound speed tends to vary depending on underwater environment factors, such as depth, temperature, and salinity. In this paper, we propose a method considering environment factors, can influence upon sound speed in underwater, and introduce experimental setup which can follow up environmental factors.

      • KCI등재

        β-Ga2O3 Nanowires and Nanobelts Synthesized by Using GaAs Powder Evaporation

        정희석,Seul Cham Kim,Do Hyun Kim,Ji Woo Kim,권오정,Chan Park,Kyu Hwan Oh 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

        We report the synthesis and characterization of β (monoclinic)-Ga2O3 nanowires and nanobelts prepared by using GaAs powder evaporation under a low vacuum condition (300Torr). As-grown β-Ga2O3 nanostructures were synthesized based on the well-known vapor-liquid-solid (VLS) mechanism by employing a Au thin film and vapor-solid (VS) reaction. Dense and uniform Ga2O3 nanowires with a diameter of 80 nm were synthesized at a higher temperature (~800℃), while various nanostructures including nanowires and nanobelts were found around 650℃. The crystalline structures and the chemical compositions of the as-synthesized β-Ga2O3 nanostructures were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectrometry (EDS). We report the synthesis and characterization of β (monoclinic)-Ga2O3 nanowires and nanobelts prepared by using GaAs powder evaporation under a low vacuum condition (300Torr). As-grown β-Ga2O3 nanostructures were synthesized based on the well-known vapor-liquid-solid (VLS) mechanism by employing a Au thin film and vapor-solid (VS) reaction. Dense and uniform Ga2O3 nanowires with a diameter of 80 nm were synthesized at a higher temperature (~800℃), while various nanostructures including nanowires and nanobelts were found around 650℃. The crystalline structures and the chemical compositions of the as-synthesized β-Ga2O3 nanostructures were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectrometry (EDS).

      • KCI등재

        동북아 다자안보협력과 러시아

        정희석 한국정치외교사학회 2006 한국정치외교사논총 Vol.27 No.2

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

        동북아 다자안보협력(Multilateral Security Cooperation in Northeast Asia)에 대한 러시아의 구상은 크게 세 시기, 즉 제정 러시아 시기, 소련 시기, 러시아 연방시기로 나누어 살펴볼 수 있다. 이들 각각의 시기마다 제안된 동북아 다자안보협력구상은 러시아의 정치적, 경제적, 군사적 이해관계를 반영한 것이었다.제정 러시아 시기 동방주의자들에 의해 제안된 동북아 안보협력 구상은 황제 니콜라이 2세의 퍼스낼리티와 매파의 득세로 인해 실현되지 못했다. 소련시기 일방적으로 제안된 아시아다자안보체제의 구상은 아시아 국가들이 중소 분쟁에 연루되기를 꺼려했을 뿐만 아니라 소련의 붕괴로 실현될 수 없었다.러시아 연방시대 들어서 제안되어 온 동북아다자안보협력 구상은 소련시대와 달리 일방적인 제안이 아니라 외교적 접촉과정에서 나온 것으로 양자성 내지는 다자성을 지니고 있었기에 아시아 국가들에 의해 수용되어 지기도 했다는 사실에 주목할 필요가 있다.러시아의 동북아 다자안보협력 구상이 실현되기 위해서는 그 동안 제약요인이었던 외교상에서의 소극적 추진력 문제가 극복되어야 하며, 동북아 다자안보협력정책이 외교정책에서 우선순위가 되어야 한다.나아가 러시아는 군비증강이나 무기수출외교와 같은 반다자주의적 행위를 삼가면서 확고한 외교적 의지를 가지고 평화정책을 추진함으로써 평화국가로서의 이미지를 확보하는 것이 중요하다. We can analyze the Russian schemes as to the multilateral security cooperation in the Northeast Asia in terms of three periods, namely that of Tsarist Russia, USSR, and Russian Federation. The Russian scheme in each period respectively reflected the political, economic, and military interests of Russia.The scheme proposed by the Easterners in the Tsarist Russia could not be materialized due to the personality of Emperor Nikolai II and the hegemony of the hawks. The USSR Scheme, unilaterally issued, did not come into effect because Asian countries were reluctant to get involved in the Sino-Soviet disputes, and USSR eventually collapsed. Concerning the scheme of the Russian Federation, however, we need to pay attention to the facts that, unlike the USSR version, it has bilaterality and multilaterality so that Asian countries often accepted it. For the successful implementation, however, it should meet these two conditions: the passivity of the Russian diplomacy has to be overcome, and the priority has to be set on the multilateral security cooperation in the Northeast Asia.Further, Russia has to establish its image as a peaceful country by firmly pursuing peace policy and giving up such anti-multilateral activities as armament and export of weapons.

      • KCI등재

        형광체 코팅에 따른 Remote Phosphor 구조의 백색 LED 패키지 특성 평가

        정희석,이정근,강한림,황명근,이미재,김진호,채유진,이영식,Jeong, Hee-Suk,Lee, Jung-Geun,Kang, Han-Lim,Hwang, Myung-Keun,Lee, Mi-Jae,Kim, Jin-Ho,Chae, Yoo-Jin,Lee, Young-Sik 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.4

        We developed a package of remote phosphor structure having blue LED chips and phosphors physically separated, and the characteristics were evaluated according to different classifications of phosphor coatings. Remote phosphor was produced by screen printing coating on glass substrate with phosphor content rated paste and heat treatment. After mounting Remote phosphor, which has been classified according to number of coatings, on top of blue LED chips, luminous flux, luminous efficacy, CCT and CRI were measured. The measurement results showed the most suitable characteristics of white LED package as a general light source when the content rate of phosphor in Remote phosphor was 80 wt.% with 3 layers of coatings and thickness over $12{\mu}m$.

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