• Journal of the korean Society of Automotive Engineers
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• v.9 no.3
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• pp.10-14
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• 1987

우리나라는 이제 그동안의 꾸준한 노력의 결과로 자동차 수출국으로 발돋움하고 있으며 이 분야 에서으 선진국과의 경쟁이 점점 치열해질 전망이다. 이러한 세계 시장에서의 경쟁 대열에서 탈 락되지 않기 위해서는 무엇보다도 제품 품질의 향상, 원가의 절감 등이 이루어져야 할 것이며 이 에 대한 노력을 게을리 해서는 안될 것이다. 한편 이와는 별도로 좀더 다른 각도에서 자동차 공업의 방향을 고찰할 필요가 있다. 즉 미래에도 계속해서 현재의 왕복동 내연기관이 자동차 구동용으로 사용될 것인가 하는 점이다. 엔진의 성능 향상, 연비의 감소, 엄격한 배기가스 규 제에의 대처 등에 대한 연구가 활발히 진행되고 있지만 기술개발에는 한계가 있으며 제품은 점점 복잡하게 되어 결국은 제품가격 및 A/S 비용이 상승되는 역효과를 나타낼 가능성이 높다. 이에 세계적인 자동차 제조회사에서는 오래전부터 새로운 방식의 미래형 자동차 engine 개발에 착수 하였으며 계속적인 연구를 진행하고 있다. 이러한 미래형 자동차 engine의 대표적인 것으로 gas turbine engine이 있다. 가스터어빈이라 하면 우선 항공기용의 jet engine을 생각하게 된다. 그 외에 발전용으로 가스터어빈은 이용되고 있으며 근래 다시 등장한 자동차용의turbocharger 역시 가스터어빈의 한 응용분야라고 할 수 있다. turbocharger의 경우는 내연기관의 출력향상을 주 목적으로 내연기관에 부착되어 이용되고 있는 반면에 gas turbine engine은 기존의 내연기관을 대체하여 자동차 구동용으로 이용되는 점에 그 차이가 있다. 아직은 실용화되징 않았지만 미래형 자동차 기관으로서의 이용가능성이 높은 gas turbine engine을 다음에 간략히 소개하고자 한다. 생산량과 하천수에 의한 생산량과의 비는 풍건물의 경우 0.6, 매물의 경우 0.5였으며 감자의 경우는 0.2이하였다. 4. 염분용수 관개구와 하천수 관개구의 모든작물에서 풍건물 생산량과 축배량 사이에는 강한 직선적인 관계를 보였다. 보리, 감자의 작물 생산량과 축배량사이에도 선형의 관계가 성립되었으나, 밀과 옥수수의 매물 생산량과 축배량사이에는 곡선적인 관계를 나타내었다..18cm)에 필적되는 연평균 4.16cm로 나타났다. 5. 전체 시험구로부터으 연평균 토양유실량은 Sharpsburg 점질양토에 대한 S.C.S 한계허용치 10ton/ha/year 이내로 나타났다. 비처리구에서의 토양유실량은 평균 2.56ton/ha/year로 높게 나타난 반면 3개의 서로 다른 추리구인 비수구, 초생수로구 및 Bromegrass구에서는 각각 0.152, 0.192 및 0.290ton/ha/year로 낮은 결과를 가져왔다. 6. 평균 침전량에 대한 L.S.D. 검정 걸과 전시험구중 비처리구가 고도의 유의차를 나타낸 반면 비수구, 초생수로구 및 Bromegrass 목초구 간에는 아무런 유의차가 인정되지 않았다. 7. 농지보전 처리구인 배수구와 초생수로구는 비처리구에 비해 낮은 침두 유출량과 낮은 토양유실량을 나타내었다.구보다 14% 절감되는 것으로 나타났다.작용하는 것으로 사료된다.된다.정량 분석한 결과이다. 시편의 조성은 33.6 at% U, 66.4 at% O의 결과를 얻었다. 산화물 핵연료의 표면 관찰 및 정량 분석 시험시 시편 표면을 전도성 물질로 증착시키지 않고, Silver Paint 에 시편을 접착하는 방법으로도 만족한 시험 결과를 얻을 수 있었다.째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.748-757
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• 2007

This paper is intended to solve the technical problem that fails in large-capacity induction motor starting due to serious voltage drop during starting period. One induction motor that is established already can reach in steady-state using reactor starting method but the voltage magnitude of PCC (point of common coupling) has dropped down a little. When the same capacity induction motor is installed additionally in the PCC, where the existing induction motor is operating, voltage drop becomes more serious by starting of additional induction motor. As a result, the additional induction motor fails in starting. Therefore, voltage compensation method is proposed so that all of two induction motors can be started completely. First, modeling technique is described in order to implement starting characteristics of large induction motor. And then, this paper proposes strategic starting scheme by proper voltage compensation that use no-load transformer tap control (NLTC) and step voltage regulator (SVR) for starting of two large induction motors successfully and improving the feeding network voltage profile during the starting period. The induction motor discussed in this paper is the pumped induction motor of 2500kVA capacity that is operating by KOWACO (Korea Water Resources Corporation). Modeling and simulation is conducted using PSCAD/EMTDC software.

• Journal of radiological science and technology
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• v.28 no.1
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• pp.1-7
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• 2005

High-quality single crystals of pure $Li_2B_4O_7$ as well as $Li_2B_4O_7$ doped with Cu, Mn and Mg impurities (1.0mol%, respectively) have been grown from the melt of $Li_2CO_3+2B_2O_3$ by Czochralski method in platinum crucibles. To study the thermoluminescent properties, $Li_2B_4O_7$ series single crystal TLDs were made by cutting in the size of $4{\times}5{\times}1\;mm^3$. The glow curves show two or three peaks which can be easily deconvoluted. It is observed that room temperature($20{\sim}30^{\circ}C$) fadings of the dosimetric peaks of $Li_2B_4O_7$ series single crystal TLDs were about 10 % for 30 days. The relative photon energy response for $Li_2B_4O_7$ series single crystal TLDs were about 85 % when the responses were normalized to that measured with $^{60}Co\;(1.25\;MeV)\;{\gamma}-rays$. The measured data are in a good agreement with theoretical ones. The $Li_2B_4O_7$ series single crystal TLDs fabricated in this work can be used for monitoring personal and environmental radioactivity.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.294-294
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• 2012

홍수위험도 추정에 있어서 불확실성은 수리, 수문, 구조, 환경 및 사회경제적인 불확실성과 관련 있으며, 수리 수문학적 불확실성은 주로 수리 수문학적 현상과 그 과정에 대한 불완전한 지식, 그리고 그 과정에 포함된 매개변수들에 대한 불완전한 지식과 관련이 있다. 이러한 여러 가지 불확실성은 홍수위험도 추정에 있어서의 불확실성에 중요한 요인으로 작용하므로 불확실성을 설명하기 위한 통계적 정보는 신뢰성 있는 홍수위험도 추정에 있어서 선행조건이라 할 수 있다. 이러한 불확실성 요인중 강우의 공간분포에 대한 신뢰성 있는 추정은 수자원 해석 및 설계에 있어서 필수적인 요소이다. 강우장의 공간변동성에 대한 고해상도 추정은 홍수, 특히 돌발홍수의 원인이 되는 국지성 호우의 확인 및 분석에 있어서 중요하다. 또한 강우의 공간 변동성에 대한 고려는 면적평균강우량 추정의 정확도를 향상시키는데 있어서 중요하며, 강우-유출모델의 모의결과에 대한 신뢰도를 향상시키는데 큰 영향을 미친다. 최근 공간자료에 대한 공간분포예측에 있어서 공간상관성을 고려할 수 있는 공간통계학적 기법의 적용이 증가하고 있으며, 이러한 공간통계학적 기법의 적용에 있어서 신뢰성 있는 모델 매개변수의 추정 및 불확실성 평가는 공간분포 예측결과에 대한 신뢰성을 향상시키는데 중요한 역할을 한다. 외국의 경우 공간분포예측 및 모의, 매개변수의 불확실성 평가 등과 관련하여 활발한 연구가 이루어지고 있는 반면 국내 수자원 분야에서는 아직까지 활발한 연구가 이루어지고 있지 않은 실정이다. 국내의 수문설계실무에서와 같이 확률홍수량을 강우빈도분석과 강우-유출모델을 이용하여 추정할 경우 확률홍수량 추정에 있어서 확률강우량 및 공간분포에 대한 불확실성과 강우-유출모델에서의 불확실성이 확률홍수량 추정에서의 불확실성에 영향을 미치며, 이후 연피해기대치 추정과 같은 홍수위험도 추정의 불확실성에도 영향을 미치게 된다. 따라서 본 연구에서는 강우공간분포의 불확실성을 고려한 홍수량 추정을 위하여 공간추계모의 기법인 CEM을 적용하여 강우공간분포의 불확실성을 정량화하고 강우-유출모델의 입력 강우량에 대한 확률분포를 추정하였다. 강우-유출해석의 경우 유효우량 및 홍수수문곡선 산정을 위하여 국내 수자원 실무에서 가장 많이 적용되고 있는 NRCS CN 기법, Clark 및 Muskingum 모델을 적용하였다. 이로부터 강우공간분포의 불확실성 추정, 소유역별 입력 강우량에 대한 확률분포의 추정 및 재현기간별 확률홍수량의 불확실성 정량화 방안을 제시하였다. 이러한 결과들은 풍수해저감대책, 유역종합치수대책 등 각종 수자원 계획 및 설계실무에서 확률홍수량 및 홍수 또는 재해위험도 추정의 신뢰성을 향상시킬 수 있는 방법론적 대안으로 활용될 수 있을 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.44 no.1
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• pp.51-64
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• 2011

The objective of this study is to develop a continuous rainfall-runoff model for flood prediction on a large-scale basin. For this study, the hourly surface runoff estimation method based on the variable retention parameter and runoff curve number is developed. This model is composed that the soil moisture to continuous rainfall can be simulated with applying the hydrologic components to the continuous equation for soil moisture. The runoff can be simulated by linking the hydrologic components with the storage function model continuously. The runoff simulation to large basins can be performed by using channel storage function model. Nakdong river basin is selected as the study area. The model accuracy is evaluated at the 8 measurement sites during flood season in 2006 (calibration period) and 2007~2008 (verification period). The calibrated model simulations are well fitted to the observations. Nash and Sutcliffe model efficiencies in the calibration and verification periods exist in the range of 0.81 to 0.95 and 0.70 to 0.94, respectively. The behavior of soil moisture depending on the rainfall and the annual loadings of simulated hydrologic components are rational. From this results, continuous rainfall-runoff model developed in this study can be used to predict the discharge on large basins.

• Land and Housing Review
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• v.4 no.3
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• pp.271-277
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• 2013

The BNWF (Beam on Nonlinear Winkler Foundation) model is one of the simplest idealizations for a pile embedded in soil as it ignores the continuity of the soil. This method is difficult to model the behavior of pile group foundation subjected to lateral loading. The limitation can be overcome with the utilization of the finite element method (FEM) or finite different method (FDM) to represent a pile element embedded in a soil medium. Both the ground and piles are modeled with soild elements. The solid elements, which do not have rotational degree of freedom, is not appropriate for modeling piles. It can be overcome by substantially increasing the number of elements, which can be prohibitive for 3D modeling. This paper used the beam element and rigid link incorporated in the OpenSees to model the pile. The accuracy of the model is validated through comparison with lateral load test and BNWF analysis. It is shown that the method can capture the measured behavior accurately. It is therefore recommended to be used in group pile analyses.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• Weed & Turfgrass Science
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• v.2 no.2
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• pp.138-151
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• 2013

This study was carried out to investigate the distribution and habitat types of prickly lettuce, Lactuca scariola of Europe origin for supplying the basic data of management plan. It showed fairly nation-wide distribution although excessive growth was rather limited in the wild. Its habitat types were divided into four types like open fields, roadsides, seashores and riversides. Species diversity examined by species rank-dominance curve tended to increase over riverside > seashores > open fields > roadsides. As a result of analyzing life form, therophytes were more than 50%, means that the habitats of L. scariola were disturbed by human activities etc. Urbanization Index was analyzed 9.1% in roadsides, 7.4% in seashores, 5.8% in open fields and riversides. It has high spread potential with a large number of wind-flying seed per plant. It was evaluated that prickly lettuce was mainly spread along the newly constructed road, expressway and invaded the original ecosystem in the cultivated land as weeds. But it has played a role as a pioneer species in open fields. It is recommended to remove where it has considerable impact on the native plant species of conservation value.

• Journal for History of Mathematics
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• v.25 no.4
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• pp.53-67
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• 2012

Today, it is necessary to calculate orbits with high accuracy in space flight. The key words of Poincar$\acute{e}$ in celestial mechanics are periodic solutions, invariant integrals, asymptotic solutions, characteristic exponents and the non existence of new single-valued integrals. Poincar$\acute{e}$ define an invariant integral of the system as the form which maintains a constant value at all time $t$, where the integration is taken over the arc of a curve and $Y_i$ are some functions of $x$, and extend 2 dimension and 3 dimension. Eigenvalues are classified as the form of trajectories, as corresponding to nodes, foci, saddle points and center. In periodic solutions, the stability of periodic solutions is dependent on the properties of their characteristic exponents. Poincar$\acute{e}$ called bifurcation that is the possibility of existence of chaotic orbit in planetary motion. Existence of near exceptional trajectories as Hadamard's accounts, says that there are probabilistic orbits. In this context we study the eigenvalue problem in early 20th century in three body problem by analyzing the works of Darwin, Bruns, Gyld$\acute{e}$n, Sundman, Hill, Lyapunov, Birkhoff, Painlev$\acute{e}$ and Hadamard.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.3
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• pp.27-27
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• 1987

The purpose of this study is to find the light intensity which induced maximum gathering rate and to observe the variation of the gathering rate both at daytime and night by using Sea-bass, Epinephelus septemfasciatus (Thunberg). An experimental tank (360 L×50 W×55H cm) was set up in a dark room. An illumination system was attached to the end of one side of the tank to control horizontal light intensity. Eight artificial light sources were prepared by combination of three with white light bulbs (10W, 60W, 100W) and eight filters. During the experiment water depth was maintained 50cm level in the tank. The tank was marked into six longitudinal sections each being 60cm long to observe the distribution of fish. The fish were acclimatized in dark condition for 50 minutes before the main experiment. Upon turning on the light, the number of fish in each section was counted 60 times every 30 seconds, and the gathering rate was obtained from the average number of fish in each section. The light intensity inducing maximum gathering rate was 24.13 lux (15.25~35.93 lux) at daytime and 0.41 lux (0.25~0.63 lux) at night. The variation of the gathering rate of fish in illumination time was great and did not show any definite pattern but fluctuated irregularly. Its different between daytime and night is remarkable.