• Title/Summary/Keyword: 반구계

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Campus Entrepreneurial Ecosystems and Regional Culture: A Comparison of Seoul National University and KAIST in Korea (캠퍼스 창업생태계와 지역문화: 서울대와 카이스트 비교를 중심으로)

  • Chun, Youyoung;Koo, Yangmi
    • Journal of the Economic Geographical Society of Korea
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    • v.25 no.3
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    • pp.320-338
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    • 2022
  • This article examines how and why entrepreneurship differs by region concerning the history of Korea's entrepreneurial ecosystems (EEs). Through a qualitative analysis of 19 interviews, this article compares the history and components of Seoul National University and KAIST (Korea Advanced Institute of Science and Technology) EEs. First, these ecosystems emerged around 1996 and are currently experiencing the second startup boom, with various supporting organizations and actors involved. Second, these ecosystems revealed differences concerning material, social and cultural attributes. Third, differences in the networking of the two ecosystems are due to different regional cultures, which allow individuals to interpret entrepreneurial opportunities. In other words, the maintenance and development of EEs are cultural in essence and display regional variation.

Development of Phantom and Comparison Analysis for Performance Characteristics of MOSFET Dosimeter (MOSFET 선량계 특성분석을 위한 팬톰 개발 및 특성 비교)

  • Chung, Jin-Beom;Lee, Jeong-Woo;Kim, Yon-Lae;Lee, Doo-Hyun;Choi, Kyoung-Sik;Kim, Jae-Sung;Kim, In-Ah;Hong, Se-Mie;Suh, Tae-Suk
    • Progress in Medical Physics
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    • v.18 no.1
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    • pp.48-54
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    • 2007
  • This study is to develope a phantom for MOSFET (Metal Oxide Semiconductors Field Effect Transistors) dosimetry and compare the dosimetric properties of standard MOSFET and microMOSFET with the phantom. In this study, the developed phantom have two shape: one is the shape of semi-sphere with 10cm diameters and the other one is the flat slab of $30{\times}30cm$with 1 cm thickness. The slab phantom was used for calibration and characterization measurements of reproducibility, linearity and dose rate dependency. The semi-sphere phantom was used for angular and directional dependence on the types of MOSFETs. The measurements were conducted under $10{\times}10cm^2$ fields at 100cm SSD with 6MV photon of Clinac (21EX, Varian, USA). For calibration and reproducibility, five standard MOSFETS and microMOSFETs were repeatedly Irradiated by 200cGy five times. The average calibration factor was a range of $1.09{\pm}0.01{\sim}1.12{\pm}0.02mV/cGy$ for standard MOSFETS and $2.81{\pm}0.03{\sim}2.85{\pm}0.04 mV/cGy$ for microMOSFETs. The response of reproducibility in the two types of MOSFETS was found to be maximum 2% variation. Dose linearity was evaluated In the range of 5 to 600 cGy and showed good linear response with $R^2$ value of 0.997 and 0.999. The dose rate dependence of standard MOSFET and microMOSFET was within 1% for 200 cGy from 100 to 500MU/min. For linearity, reproducibility and calibration factor, two types of MOSFETS showed similar results. On the other hand, the standard MOSFET and microMOSFET were found to be remarkable difference in angular and directional dependence. The measured angular dependence of standard MOSFET and microMOSFET was also found to be the variation of 13%, 10% and standard deviation of ${\pm}4.4%,\;{\pm}2.1%$. The directional dependence was found to be the variation of 5%, 2% and standard deviation of ${\pm}2.1%,\;{\pm}1.5%$. Therefore, dose verification of radiation therapy used multidirectional X-ray beam treatments allows for better the use of microMOSFET which has a reduced angular and directional dependence than that of standard MOSFET.

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Machining Precision according to the Change of Feedrate when Ball Endmilling of Semisphere Shape (볼 엔드밀에 의한 반구 가공시 이송속도 변화에 따른 가공정밀도)

  • 임채열;우정윤;김종업;왕덕현;김원일
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.05a
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    • pp.930-933
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    • 2000
  • Experimental study was conducted for finding the characteristics of machining precision according to the change of feedrate when ball endmilling of semisphere shape. The values of tool deflection and cutting force were measured simultaneously by the systems of eddy-current sensor and dynamometer. The machining precision was analyzed by roundness values, which were deeply relating with tool deflection and forces. the roundness was decreased in down-milling than in up-milling for each feedrate. As the cutting edge is moved to radius direction on the tool path, the tool deflection and the cutting force were seemed to be decreased. As the tool path was moved downward, the values of roundness, cutting force and tool deflection were obtained better ones. When compared the values of roundness, cutting force and tool deflection for different feedrate, the best machining accuracy was obtained at feed rate of 90mm/min in down-milling.

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$LP_{11}$ Mode Fiber Optic Resonant Ring Interferometer with a $LP_{11}$ Modal Filter ($LP_{11}$ 결모양 빛살거르게를 사용한 $LP_{11}$ 결모양 빛살 광섬유 공진고리 간섭계)

  • 이현재;이두희;서상준;양진성
    • Korean Journal of Optics and Photonics
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    • v.2 no.1
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    • pp.20-25
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    • 1991
  • Using evanescent field coupling between single ($LP_{01}$) and double ($LP_{01}, LP_{11}$) mode optical fiber, we selected LPII mode beam. With a $LP_{11}$ mode beam from a double mode fiber. we fabricated $LP_{11}$ mode fiber optic resonant ring interferometer, and assured that the guided mode is $LP_{11}$ mode from a radiation beam coming through the prism output coupler. When an external perturbation applied to the signal arm of the $LP_{11}$ fiber optic resonant ring interferometer, we examined the change of radiation mode coming from a prism output coupler and an end of optical fiber. Using two photodiode, LPn mode beam converted to voltage. This two output voltages is applied to X and Y terminal of oscilloscope to display circular motion on oscilloscope.

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태양계의 물: 기원과 진화

  • Choe, Byeon-Gak;Choe, Hye-Rim
    • 한국지구과학회:학술대회논문집
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    • 2005.09a
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    • pp.3-8
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    • 2005
  • 지구는 현재 태양계에서 액체 상태의 물이 표면에 존재하는 유일한 천체이다. 하지만, 고체 또는 기체 상태의 물은 태양계의 다른 행성이나, 위성, 소행성, 혜성 등에도 풍부하게 존재하고 있다. 풍부한 액체 상태의 물은 지구 표면에서 일어나고 있는 기후의 변화, 해류의 이동, 퇴적 및 침식 작용, 화산활동과 같은 여러 지구과학적 현상에 밀접하게 관여하고 있을 뿐 아니라 생명의 탄생과 진화에도 매우 중요한 역할을 하였다. 현재 지구 표면에 액체 상태의 물이 존재할 수 있는 이유는 태양으로부터의 거리, 지구의 조성 및 크기 등과 관련된 지구 표면의 물리-화학적 조건이 액체 상태의 물이 존재할 수 있는 조건과 일치하고 있기 때문이다. 이와는 달리 지구보다 태양에 더 가깝게 위치하고 있고, 두터운 이산화탄소 대기를 갖고 있어 표면의 온도가 매우 높은 금성의 경우 H2O는 기체 상태로 존재하며, 지구보다 더 멀리 떨어져 있고 희박한 대기를 갖고 있는 화성의 경우에는 현재 H2O가 고체 즉 얼음의 형태로 존재한다. 태양계를 탄생시킨 태양계 성운에서는 압력이 너무 낮아 액체 상태의 물이 존재할 수 없으며, 고온에서는 기체 상태로 매우 낮은 저온에서는 얼음의 형태, 또는 함수 광물 내에 포함되어 존재할 수 있다. 지구와 같은 규모의 행성은 비교적 중력이 작아 태양계 성운의 기체를 거의 끌어들이지 못했다. 따라서 현재 지구에 존재하는 물은 대부분은 고체 상태로 지구에 집적되었을 것이다. 하지만 지구가 탄생한 위치에서 초기 태양계의 온도는 얼음이 형성되기에는 너무 높았기 때문에 좀 더 먼 곳에서(현재의 목성 위치보다 바깥쪽)에서 생성된 얼음 즉, 혜성이 태양계 안쪽으로 들어와 지구에 물을 공급했거나 함수광물을 포함하고 있는 소행성(예를 들어 CI chondrites와 같은 조성의)이 물을 가져왔을 것으로 생각되고 있다.서의 활성화는 어미 변환과 관련된 영역이라기보다는 산출시 관련되는 articulation, motor coordinate관련 영역으로 추정되고, 측두엽의 활성화는 형태소, 의미 관련 지식의 data base로 추정된다. 또한 우반구 전두엽 부분에서 관찰된 활성화는 억제관련 영역으로 짐작된다.러한 동물실험이 그 기초를 제공해 줄 수 있을 것이다. 또한 행동성향 및 기억의 종류에 따른 약물효과의 차이는 기억과 관련된 질병인 알츠하이머 환자에 있어 개개인에게 맞는 적절한 특징적인 치료약물이 존재할 것이라는 가능성을 제공해줄 뿐만 아니라 학습과 기억력 증진 효과를 기대해 볼 수 있을 것이라고 생각된다. 및 지역산업발전의 기획${\sim}$조정기구로서, 선진국의 지역발전기구(Regional Development Agency : RDA)인 지역전략산업기획단이 2002년도부터 산업자원부와 9개 시도에 의해 설립되어 지역네트워크의 활성화와 클러스터의 형성 촉진을 하게 되었고 2004년도에는 13개시도로 확대${\sim}$운영되고 있고, 지역특화사업(H/W)과 지역산업기술개발과제(S/W)와 함께 패케지 형태로 지원되며, 주요역할은 크게 지역산업의 정책기획 분야와 평가관리, 지역혁신역량 조사 및 DB구축 등으로 구분된다. 그중에서도 권역별, 지역별, 지역산업진흥사업 육성과 중장기 산업발전계획을 수립하기 위하여 지역혁신역량을 바탕으로 한 지역 Technology Road Map(TRM)작성사업은 전국공통의 1단계 사업으로 실시 ?榮쨉?, 2005년 3월 기준으로 9개 지역(강원, 대전, 충남, 충북, 경북, 울산, 전남, 전북, 제주) 26개 산업분야를 대상으로 23개가 완료된 상황이다. 이를 근거로 한 지역정책과 R&D 과제 및 필요 인프라의 도출이 체계적으로 구축되어 지역산업 발전을 위한

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Building the University Entrepreneurial Ecosystem towards Hub University at Seoul National University in Korea (서울대 창업생태계의 형성과정과 허브 대학으로의 변화)

  • Soyeong Jung;Yangmi Koo
    • Journal of the Economic Geographical Society of Korea
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    • v.25 no.4
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    • pp.469-483
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    • 2022
  • This paper aims to examine how and why the role of Seoul National University has evolved through the formation of Seoul National University's entrepreneurial ecosystems (SNUEEs). To identify this, we used secondary data on SNU entrepreneurship and did in-depth interviews with 17 student entrepreneurs and supportive actors in the ecosystems. First, the university-industry cooperation policy and the first start-up boom in the late 1990s gave rise to the first generation of SNUEEs. They entered the second generation with the second start-up boom in 2010. The third generation emerged through the government's start-up support policy and the venture investment market revitalization in 2017. Second, SNUEEs have experienced transformations of the university's role from an 'ivory tower' to a 'feeder of knowledge and labor' and have become a 'hub of knowledge networks.' Third, hub institutions and organizations were established and supported by government policies, and networks of SNUEEs have been embedded in these hub institutions and organizations. SNUEEs as a hub university are evolving through the formation of a voluntary entrepreneurial culture by student entrepreneurs, the supportive policy at the university level, and the establishment of linkages with the region where the university is located.

Variations of Fish Community and Fish Density on Artificial Reefs (인공어초어장의 어류 군집상과 어획량 변동)

  • LEE Jeong-Woo;KANG Young-Shil
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.27 no.5
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    • pp.535-548
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    • 1994
  • Community structures and fish densit were investigated on three different types of artificial reefs, dice, turtle artificial reef and tubes, constructed in the Korean waters. Variations of fish fauna according to type of artificial reef and the proper artificial reef in each area for optimizing harvest were discussed. Fish were captured by trammel gill net during May, June, September and November, 1988 and both identified and counted. Fourty-five fish species were found in the artificial reefs. Of these, Sebastes spp., Hexagrammos otakii, Pleuronectidae, Navodon modestus and Stephanolepis cirrhifer showed high occurrence-frequency. The dominant species groups were coastal settlement, demersal or rock fishes such as Pleuronectidae, Rajiformes, Stephanolepis cirrhifer, Navodon modestus, Hexagrammos otakii and Sebastes spp. in all of the Artificial reefs except the oceanic area of southern waters. Scomber japonicus was predominant in the oceanic area of southern waters. Composition of demersal, rock and pelagic fishes were different depending on the types of artificial reef. Dice artificial reefs were occupied by rock fish, on the other hand turtle artificial reefs were dominated by dermersal fish. Fish density was high at the dice artificial reef in all survey areas except the middle area of Eastern waters, with high fish density evident in the Tube artificial reef. Fish community structures were remarkably different between Dice and Turtle artificial reefs. The Tube artificial reef showed intermediate characteristics between the above two types of artificial reefs. The coastal areas of Southern waters and the middle and southern areas of Western waters revealed similar fish fauna. Results from the oceanic areas of Southern waters were well associated with the middle and southern areas of Eastern waters.

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Soil Ionization Phenomena around a Hemispherical Electrode Stressed by Impulse Voltages (임펄스전압에 의한 반구형 전극계에서 토양의 이온화 현상)

  • Heo, Dae-min;Kim, Hoe-gu;Lee, Bok-hee
    • KEPCO Journal on Electric Power and Energy
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    • v.2 no.4
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    • pp.601-608
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    • 2016
  • The electrical characteristics of the soil where a ground electrode is buried vary with regions, seasons and environmental factors. Electrical discharge in the vicinity of the ground electrode will occur differently and significantly affect the performance of the grounding system. It is necessary to analyze discharge and ionization characteristics of soils when the grounding system is designed. The aims of this investigation are to understand correlation between the soil ionization and the transient ground impedance. This paper presents the experimental results on the soil ionization parameters and the transient ground resistance due to the soil ionization around a hemispherical ground electrode stressed by lightning impulse voltages.

Ionization Behaviors by Types of Soil due to Lightning Impulse Voltages in a Hemishperical Electrode System (반구형 전극계에서 뇌임펄스전압에 의한 토양의 종류별 이온화 특성)

  • Lee, Kyu-Sun;Park, Geon-Hun;Kim, Hoe-Gu;Lee, Bok-Hee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.1
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    • pp.119-125
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    • 2009
  • This paper deals with the characteristics of soil ionization affecting the dynamic performance of grounding systems under lightning impulse voltage. A concentric hemispherical electrode system was employed in order to facilitate the field calculation and analysis of the experimental results. The parameters such as the ionization threshold and breakdown field intensity, the pre-ionization and the post ionization resistances, the time-lag to ionization, the transient impedance, the equivalent ionized radius for various soil media were measured and analyzed. The dynamic characteristics of ionization processes under lightning impulse voltage are strongly dependent on the types of soil and water content. As a result, a soil ionization reduces the ground resistance and there is a little effect of applied impulse polarity on the soil ionization threshold field intensity. Although the ionization threshold field intensity of wet clay with 30% water content is the highest, its ionized zone was found to be the smallest amongst the test samples.

The Study of Aerodynamic Heating Characteristics for the Design of Nose Shapes of Space Launcher (발사체 선두부의 공력가열현상 특성연구)

  • Choi, Won;Kim, Kyu-Hong;Lee, Kyung-Tae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.6
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    • pp.14-20
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    • 2002
  • The aerodynamic heating at a nose cone is predicted under the KSR-III flight conditions. An equilibrium reacting gas condition is applied. The parametric study is performed with Mach number of 4.9, 10.2 and 15 and for the following nose shapes of hemisphere, cut cylinder and parabola. AUSMPW+ and shock aligned grid technique are used to provide the best aerodynamic solutions. In addition, the composite material of a nose cone is discussed in the viewpoint of a thermal safety.