• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.5
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• pp.583-589
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• 2013

In this paper, we proposed a system that efficiently provides support maps which includes the grid based terrain analysis information. To do this, we use the FDB which is defined as a GIS database that contains features with attributes attached to the features. The FDB is composed of a number of features and feature classes. In order to create support maps, it is necessary to classify feature classes that are associated with each support map and to search them in a grid map. The proposed system use a ontology model to classify semantically feature classes and the quad-tree data structure to find them in a grid map quickly. Therefore, our system is expected to be utilized for global path planning of UGV. In this paper, we show the possibility through an experimental implementation.

• Journal of Environmental Science International
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• v.2 no.1
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• pp.1-8
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• 1993

This study was carried out to find the relationships between species pairs in the vegetation of eastern valley vegetation in Mt. Kumjung from September 20, 1991 to October 15, 1992. Eight sites were selected, each being divided into 5 quadrats, and thus 40 quad- rats were in total. To know the correlation among plant species the $x^2$ values were calculated by using the method of Yates, and the results were analyzed by cluster analysis according to Sneath and Sokal, and the following conclusions were obtained. The species examined can be subdivided into five groups according to the relationships. However, the relationships are not correlated with pH, water-content, maximum water holding capacity and mineral content of soil probably due to the environmental discontinuity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.107-120
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• 2021

Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.

• Journal of Power Electronics
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• v.6 no.2
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• pp.104-113
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• 2006

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; $(1^{st})$ paying attention to details, and $(2^{nd})$ handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application. This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

• Journal of Navigation and Port Research
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• v.34 no.5
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• pp.367-373
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• 2010

When the numerical analysis is carried out, it is necessary to set proper elements as a feature of analysis domains for more accurate simulations. In this study, Distinct Element Method(DEM) is applied, only considering repulsive force and tensile force except for frictional force and resisting force of particle. When the filled particles with initial Quad-tree type is relocated by DEM, a blank space existing among the particles can be minimized because the shape of particle is circular. Finally, it is the effective feature that the centroidal disposion of the particles is similar to an equilateral triangle. Triangular mesh are formed by using the Delaunay triangular technique on these relocated particles, the quality of triangular mesh is more improved by carrying out Laplace interpolations. The compared result of Aspect Ratio before and after the Laplace interpolation is shown that although the quality of triangular mesh made by DEM is good, the later triangular mesh are higher quality than the formers. In this study, although the developed technique takes a longer calculational time than the previous technique to generate triangular mesh, it is considered that the applicable possibility is very high in the generation of finite element mesh about wave analysis and various numerical simulation to need a complex or reappearance of exact topography.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.56-57
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• 2015

근래 3D산업의 발전으로 디지털 홀로그램 기술이 부각되고 있다. 본 논문에서는 디지털 홀로그램 영상을 쿼드트리형식으로 Fresnelet 변환을 통한 양자화기를 구현하기위해 특징 및 중요도를 분석하는 방식에 대해 제안한다. 디지털 홀로그램 영상을 Fresnelet 변환을 수행한 뒤 부대역 별로 평균에너지에 따른 에너지 분포의 순위를 정하였고, 크기에 따른 히스토그램의 결과를 이용해 향후 디지털 홀로그램 압축 및 전송 기법에 적용할 수 있는 것을 확인 하였다.

• YAKHAK HOEJI
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• v.36 no.3
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• pp.199-204
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• 1992

The trace elements in animal feed were analyzed by Inductively Coupled Plasma Mass Spectrometer (ICP-MS, VG-PlasmaQuad Co.) to find possible sources of heavy metals accumulation in rat organ. The study about spectral interference was performed by analysis of a background spectrum of ICP-MS. Recovery test using standard of Cd and Se (100 ppb) was found to be better than 90%. Twenty elements (Ca, Fe, Mg, Ti, Cr, Ni, Cu, Zn, Ba, Al, Mn, Pb, B, Ce, Bi, U, V, Cd, and W)are determined.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.163-166
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• 2012

OpenMP를 이용할 경우 컴파일러 디렉티브의 삽입으로 병렬화가 가능하다. 본 논문은 쿼드 트리를 이용한 데이터베이스 검색 프로그램을 OpenMP로 병렬화하여 실험을 진행한다. 실험을 통해 논리코어의 개수와 쓰레드 개수에 따른 상관관계가 적다는 것을 알 수 있다. 또한 쓰레드 개수 증가에 따른 오버헤드 발생이 성능에 영향을 준다는 사실을 알 수 있다. 쿼드 트리 자료구조를 이용한 데이터베이스 검색 프로그램을 OpenMP를 이용해 병렬화할 경우 논리적 코어의 개수가 8개, 쓰레드 개수가 16개일 경우에 1.8배의 최대의 성능향상을 이룬다.

• Journal of the Korean Society of Visualization
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• v.8 no.1
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• pp.39-45
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• 2010

The optimal design is needed for the blade geometry of the quad-rotor blades which is mainly used for Unmanned Aerial Vehicle. To do this, it is important to analyze the wakes under the blades. In the present study, the flow around the rotating blades was analyzed using PIV(Particle Image Velocimetry) and CFD(Computational Fluid Dynamics). The maximum axial velocity was measured at about 60% position toward the radial direction of the blade. The positions of vorticities in the test section obtained by PIV and CFD were turned out to be almost alike. The values in the difference of pressure coefficients at the upper and the lower blades were increased depending on the radial direction. Then, the values were decreased at the blade tip. The data of the flow analysis in the present study are expected to be served as the design of blades and ducts for the thrust improvement in the future.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.17-20
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• 2003

The EMC's rheological effects on molding process are evaluated in this study. When considering mold processing for IC packages, the major concerning items in current studies are incomplete fill, severe wire sweeping and paddle shifts etc. To simulate EMC's fast curing rheokinetics with 3D mold flow behavior, one should select appropriate rheometry which characterize each EMC's rheological motion and finding empirical parameters for numerical analysis current studies present the new rheometry with parallel plate rheometry for reactive rheokinetic experiments, the experiment and numerical analysis is done with the commercial higher filler loaded EMC for the case of Thin Quad Plant Packages (TQFP) with package thickness below 1.0 mm. The experimental results and simulation results based on new rheometry matches well in point of the prediction of wire sweep, filling behavior of melt front advancement and void trapping position.