• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.1
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• pp.63-73
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• 2014

Recently, researches on DBRN(DataBase Referenced Navigation) system are being carried out to replace GNSS(Global Navigation Satellite System), as weaknesses of GNSS were found that are caused by the intentional interference and the jamming of the satellite signal. This paper describes the gravity gradient modeling and the construction of EKF(Extended Kalman Filter) based GGRN(Gravity Gradient Referenced Navigation). To analyze the performance of GGRN, fourteen flight trajectories were made for simulations over whole South Korea. During the simulations, we considered the errors in both DB(DataBase) and sensor as well as the flight altitudes. Accurate performances were found, when errors in the DB and the sensor are small and they located at lower altitude. For comparative evaluation, the traditional TRN(Terrain Referenced Navigation) was also developed and performances were analyzed relative to those from the GGRN. In fact, most of GGRN performed better in low altitude, but both of precise gravity gradient DB and gradiometer were required to obtain similar level of precisions at the high altitude. In the future, additional tests and evaluations on the GGRN need to be performed to investigate on more factors such as DB resolution, flight speed, and the update rate.

• Journal of Korean Society of Forest Science
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• v.78 no.3
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• pp.314-322
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• 1989

For the improvement of nursery condition and the study of eco-physiological characteristics of Pinus koraiensis(2-2) seedlings, the primary productivity was investigated and the growth characteristics and their correlationship were analyzed from May to September in 1987. Seedlings used in this study were grown at the nursery of Experimental Forestry of Kyung Hee Univ. The installation of experimental plots were divided into control plot (100%), 63%, 37% and 19% relative light intensity, and each relative light intensity plots were split into $15{\times}15/m^2$, $12{\times}12/m^2$, $9{\times}9/m^2$ and $6{\times}6/m^2$ plnting density by randomized black design method. To take into account the edge effect of plant population, material were selected from each plot by random sampling at 30 days interval. Each sampled material was divided into leaf and stem drived in a drying oven at the temperature of $85^{\circ}C$ until it had constant weight and weighed. and leaf area was surveyed. Growth analysis for RGR and NAR was done by Blackman method and correlation coefficient were investigated between RGR and NAR by analyzing the dry matter production and growth characteristics of the material, cultivated on the experimental nursery under the condition of different treatment the obtained result were as follows : 1. The increasing rate of dry matter was similar at early stage of growth, but not at late stage. 2. Leaf area growth was the maximum value at 63% relative light intensity and the minimum at 19% RLI 3. The value of RGR was the highest on June under $6{\times}6/m^2$ planting density in 63% relative light intensity, the lowest on September under $12{\times}12/m^2$ of 19% relative light intensity. 4. The change NAR decreased in early stage of growth, while it increased on August and September, The value of RGR on June under $6{\times}6/m^2$ planting density in 100 light intensity was the highest, and on September under $12{\times}12/m^2$ planting density in 19% relative light intensity was the lowest. 5. Regression and correlation between RGR and NAR showed significantly positive.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1770-1771
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• 2011

In mission planning of UAV applications, especially for the missions requiring height transitions, it is required to generate reference flight trajectories considering the performances of the engine installed in the UAV. Even though the vertical line following guidance based height transition trajectory generation method has been developed to build reference height transition trajectories easily, it is not adequate for considering engine performances effectively since many engine characteristics and performances have conventionally been described in the V-H(speed-height) plane which is not the very space where the UAVs are actually flying. In this paper, we derive the trajectories in V-H plane for the vertical line following flights. And based on the results, a new algorithm to design the reference height transition trajectories for UAV applicaions. Simulation results demonstrate that the proposed algorithm is very effective and easily applicable.

• Tribology and Lubricants
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• v.3 no.1
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• pp.12-17
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• 1987

밀봉장치는 밀봉요소 또는 시일(seal)이라 불리우며, 서로 접촉한 부분 사이에서 유체의 누설방지 및 이물질의 침입방지에 이용되고 있다. 밀봉면에 거시적인 상대운동이 있는가 없는가에 따라 동적요소와 정적요소로 분리된다. 동적밀봉요소를 운동용 시일 또는 패킹(packing)이라하고 크게 접촉형과 비접촉형으로 분리된다. 정적밀봉요소를 정지용 또는 고정용 시일이라하며 가스켓(gasket)이라고도 한다. 오일 시일의 일반적인 사항에 대해 설명하였다. 사용기기의 고속, 고성능화에 다라 오일 시일의 사용조건이 점점 가혹하게 되고 있으므로 신뢰성과 안정성에 대한 요구도 증가하고 있다. 특히 트러블 원인은 살펴보면 취급법이나 축에 기인하는 초기 고장이 많으므로, 사용조건에 적당한 오일 시일을 선정하고 올바른 사용 방법을 지키므로서 초기 고장을 대폭 감소시킬 수 있다. 보다 전문적인 내용들은 관련 문헌을 참조바란다.

• Journal of the Korean earth science society
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• v.38 no.7
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• pp.496-510
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• 2017

This study presents a new nationwide quantitative precipitation estimation (QPE) based on the hybrid surface rainfall (HSR) technique using the weather radar network of Korea Meteorological Administration (KMA). This new nationwide HSR is characterized by the synthesis of reflectivity at the hybrid surface that is not affected by ground clutter, beam blockage, non-meteorological echoes, and bright band. The nationwide HSR is classified into static (STATIC) and dynamic HSR (DYNAMIC) mosaic depending on employing a quality control process, which is based on the fuzzy logic approach for single-polarization radar and the spatial texture technique for dual-polarization radar. The STATIC and DYNAMIC were evaluated by comparing with official and operational radar rainfall mosaic (MOSAIC) of KMA for 10 rainfall events from May to October 2014. The correlation coefficients within the block region of STATIC, DYNAMIC and MOSAIC are 0.52, 0.78, and 0.69, respectively, and their mean relative errors are 34.08, 30.08, and 40.71%.

• Strategy21
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• s.43
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• pp.89-124
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• 2018

평화를 전쟁의 부재라고 정의할 때 현재 전쟁이 없다면 지금 이 시간은 안전하고 평화로워야 한다. 그러나 지금 현 세상은 비록 공식적으로 선포된 전쟁은 없다고는 하지만 그래도 결코 평화롭다곤 할 수 없을 것이다. 흑해의 크림반도가 노골적인 군사적 침략이 없었지만 결과적으로 러시아의 수중에 떨어졌다. 남중국해의 여러 섬이나 암초들이 정규 군사작전 없이 사실상의 중국의 소유로 기정사실화 되고 있다. 전시 군사적 침략을 통해서만이 확보 가능한 전략적 목표들이 전시도 아니고 그렇다고 평시도 아닌 어중간한 시기에 적 또는 상대의 수중에 떨어지고 있다. 즉, 전시와 평시 사이의 회색지대에서 소위 회색지대전략이라고 부르는 공세적 전역을 통해 이러한 전략적 목표들이 달성되어 지고 있다. 소시지가 너무 커 한입에 다 먹을 수 없으면 잘게 썰어 하나씩 먹으면 결국 전체를 다 먹을 수 있듯이 소규모의 절차적 행동을 단계적으로 실행, 대규모 전투를 통해서만이 확보 가능한 거대하고 중대한 목표를 확보하는 게 회색지대전략의 한 특징이다. 이를 전략적 점진주의(strategic gradualism)라고 한다. 또한 단계적 행동은 누구나 인지할 수 있지만 그러한 점진적 행동의 결과에 대해선 쉽게 간파할 수 없기 때문에 대응자의 입장에선 대부분 특별한 대응책을 세우지 못하고 방치하고 만다는 게 이 전략의 또 다른 특성이다. 즉, 회색지대전략은 특성상 반드시 애매모호성(ambiguity)을 띄고 있다는 것이다. 회색지대에서의 도전자의 행위는 일종의 속임수일 수도 있다. 전략의 본질은 위계, 즉 상대로 하여금 오인, 착각, 부지를 일으키도록 하여 소기의 목적을 달성하는 것이다. 그래서 회색지대전략(gray zone strategy)이라고도 한다. 양육강식의 논리가 작용되는 현실 세계에선 힘이 곧 정의이고 국익이 최고의 선이다. 국가이익은 오직 과정보다는 결과만을 놓고서 정당화된다. 이에 회색지대전략에서도 결과에 대한 유용성만 거론되지 과정상 불법성이나 비도덕성 등은 따지지 않는다. 대부분 이 전략의 애매모호성 때문에 과정 자체를 식별하기가 쉽지 않다. 그래서 대응자의 입장에서도 사전에 예방할 수 있는 선제적 대응전략을 구사하기가 어려운 게 사실이다. 한국도 예외가 아니다. 중국이 해상민병을 이용한 회색지대전략을 구사, 이어도에 대한 도발을 감행할 수도 있다. 일본이 민간 극우파 등을 이용한 회색지대 전략을 구사, 독도에 대한 도발을 감행할 수도 있다. 평화는 거저 존재하지 않는다. 확전을 각오한 사전대비차원의 억지책이 마련되어야 상대의 회색지대전략을 단념시킬 수 있다. 그것도 신뢰성 있는 억지력만이 진정한 평화를 담보할 수 있다. 전략이 있어야 대응계획을 세울 수 있고, 상대는 이럴 때 도발을 단념하게 된다. 대응전략이 없다는 것은 대응계획이 없다는 것을 의미하고, 이러한 무계획은 늘 실패만을 계획하고 있다는 것을 명심해야 할 것이다.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.123-132
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• 1995

We developed a S/W system to simulate the orbit tracking data as nearly equal as the real data obtained at the tracking antenna by modeling various causes that could have effects on the tracking data (range, range rate, azimuth, elevation) of an artificial satellite. Using the S/W developed we produced delay values of tracking data due to the light-time effect and the terrestrial atmosphere. According to the simulation results due to the Earth atmosphere, the values delayed by the troposhpere were increased as the temperature, relative humidity, and pressure of the troposphere are more larger. However, delay values due to the ionosphere were dependent on both the maximum electron density and the frequencies used. They are more and more increased as the maximum electron density and frequency are more larger. And the delaying values by the light-time effect are more larger by the fast orbital motion as the altitude of an artificial satellite is more lower.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1002-1009
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• 2009

Precision guidance filter design for a tactical missile with a strapdown seeker aided by low-cost strapdown sensors has been addressed in this paper. The low-cost strapdown sensors consist of an IMU with 3-axis accelerometers and gyroscopes, 3-axis magnetometers, and a barometer. Missile's position, velocity, attitude, and bias error of the barometer are considered as state variables. Since the state and measurement equations are highly nonlinear, we adopt UKF(Unscented Kalman Filter). The proposed guidance filter has a function of a navigation filter if target position error is not considered. In the case that the target position error is introduced, the proposed filter can effectively estimate the relative states of the missile to the true target. For specific engagement scenarios, we can observe that observability problems occur.

• Journal of Ginseng Research
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• v.13 no.2
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• pp.165-168
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• 1989

Ginseng plants in the 2nd year were grown under the shade (90-95%) of colored cellophane films at $15^{\circ}C$ in a natural light phytotron. Relative root grown (final/initial) was in decreasing order of blue, green, white, yellow and red. The growth of aerial part, especially stem length was poorest in blue light with relative root growth negatively correlated with stem length. In this relation each color showed specific domain. Stem length showed positive linear correlation with leaf area per plant in each and among light though it was not significant in red light. The content and ratio of chlorophyll a and b in leaf were in the decreasing order of White, Blue, Green, Red and Yellow. There is positive correlation between chlorophyll a and chlorophyll b, and between total chlorophyll and chl:a/b ratio. Blue color shade is expected to be beneficial for ginseng production.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.4
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• pp.337-342
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• 1984

224 profiles representing 19 soil series were subjected to multiple regresion analysis to determine the relative contribution of organic matter(OM) and clay content to total cation exchange capacity(CEC) in sandy soil. The independent variables were OM and clay, with the dependent variable CEC. Simple correlation coefficients showed high significance at CEC-OM and CEC-clay. The partial regression coefficients indicated that CEC for each gram of OM was calculated to be 0.549 and 1.351 meq of top and subsoil. The clay contributions of top and subsoil were 0.247 and 0.226 meq, respectively. The standard partial regression coefficients appeared that clay content was 1.23 times as important as orgnic matter in predicting CEC.