• Title/Summary/Keyword: 직교모델

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A Mathematical Model for Asymmetrical/Heterogeneous Traffic Management in TD-CDMA System (시분할-코드분할 다중 접속 시스템에서 비대칭/불균질 트래픽 처리에 대한 수학적 모델)

  • Shin Jung chae;Lee Yutae;Kim Jeong ho;Cho Ho shin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.4A
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    • pp.259-270
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    • 2005
  • This paper proposes a mathematical model to analyze call-and packet-level performance of the TD-CDMA/TDD system which could serve a flexible radio resource management against multi-type heterogeneous and asymmetrical traffic conditions. On call-level analysis, the mathematical model based on queueing theory performs multi-dimensional operations using random vectors or matrices to consider multiple types of traffic and also deal with asymmetrical up- and down-direction transmissions separately. Employing the mathematical model, we obtain rail blocking probability for each type of traffic and also the optimum switching-point with the smallest call flocking probability. And on packet-level analysis, employing a non-prioritized queueing scheme between circuit and packet calls, we solve 2-dimensional random vector problem composed of the queue length for packets and the number of circuit calls being served. Finally, packet-level performance is analyzed in terms of the packet loss probability and the buffer size required under mixed-traffic conditions of multiple types of circuit and packet calls.

A Constant Time RMESH Algorithm for the Union of Iso-Oriented Rectangles (좌표축에 평행한 직사각형들의 합집합을 구하는 상수시간 RMESH 알고리즘)

  • Kim, Soo-Hwan;Choi, Jinoh
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2017.10a
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    • pp.627-629
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    • 2017
  • There are a lot of research results on the problem of finding the union and intersection of n rectangles on a plane. Lipski와 Preparata(1981) presented a sequential algorithm with O(nlogn) time and O(nlogn) space for the problem of finding the union of rectangles whose sides are parallel to the coordinate axes[1]. Alevizos(2013) presented an improved O(nlogn) time and O(n) space algorithm for the same problem[2]. In this paper, we consider the problem of finding the union of iso-oriented rectangles such that the intersection of them is not an empty set. In this case, the union of the rectangles becomes a connected area, that is, an orthogonal polygon. In this paper, we propose a parallel algorithm that solves this problem in constant time in a reconfigurable mesh(in short, RMESH) model.

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Analysis of Doppler Effects in OFDM Systems Using Transceiver Diversity (송수신 다이버시티를 이용한 OFDM시스템에서의 도플러 영향분석)

  • Lee, Jong-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.9
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    • pp.1658-1664
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    • 2007
  • The popularity of OFDM systems is being increased because of high speed data transmission capability md the spectral efficiency characteristics. However, since OFDM systems are very sensitive to the Doppler spread, The interference among subcarriers and the total system noise can be increased seriously due to the degree of Doppler effects which can cause the orthogonality problems. Therefore, these Doppler effects were analyzed using the Doppler spectrum models by varying its parameters. Especially in this paper, The degree of system performance degradation was investigated for the OFDM systems applying the relatively simple transmit and receiver diversity. The degree of the system performance degradation depends on the specific diversity structures of transceiver systems. Here, the performances of OFDM systems with two antennas transceiver diversity were analyzed and compared with that of systems with only transmission diversity and without diversity as the Doppler characteristics varied.

Intensified Low-Temperature Fischer-Tropsch Synthesis Using Microchannel Reactor Block : A Computational Fluid Dynamics Simulation Study (마이크로채널 반응기를 이용한 강화된 저온 피셔-트롭쉬 합성반응의 전산유체역학적 해석)

  • Kshetrimatum, Krishnadash S.;Na, Jonggeol;Park, Seongho;Jung, Ikhwan;Lee, Yongkyu;Han, Chonghun
    • Journal of the Korean Institute of Gas
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    • v.21 no.4
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    • pp.92-102
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    • 2017
  • Fischer-Tropsch synthesis reaction converts syngas (mixture of CO and H2) to valuable hydrocarbon products. Simulation of low temperature Fischer -Tropsch Synthesis reaction and heat transfer at intensified process condition using catalyst filled single and multichannel microchannel reactor is considered. Single channel model simulation indicated potential for process intensification (higher GHSV of $30000hr^{-1}$ in presence of theoretical Cobalt based super-active catalyst) while still achieving CO conversion greater than ~65% and $C_{5+}$ selectivity greater than ~74%. Conjugate heat transfer simulation with multichannel reactor block models considering three different combinations of reactor configuration and coolant type predicted ${\Delta}T_{max}$ equal to 23 K for cross-flow configuration with wall boiling coolant, 15 K for co-current flow configuration with subcooled coolant, and 13 K for co-current flow configuration with wall boiling coolant. In the range of temperature maintained (498 - 521 K), chain growth probability calculated is desirable for low-temperature Fisher-Tropsch Synthesis.

Application of Hydro-Cartographic Generalization on Buildings for 2-Dimensional Inundation Analysis (2차원 침수해석을 위한 수리학적 건물 일반화 기법의 적용)

  • PARK, In-Hyeok;JIN, Gi-Ho;JEON, Ka-Young;HA, Sung-Ryong
    • Journal of the Korean Association of Geographic Information Studies
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    • v.18 no.2
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    • pp.1-15
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    • 2015
  • Urban flooding threatens human beings and facilities with chemical and physical hazards since the beginning of human civilization. Recent studies have emphasized the integration of data and models for effective urban flood inundation modeling. However, the model set-up process is tend to be time consuming and to require a high level of data processing skill. Furthermore, in spite of the use of high resolution grid data, inundation depth and velocity are varied with building treatment methods in 2-D inundation model, because undesirable grids are generated and resulted in the reliability decline of the simulation results. Thus, it requires building generalization process or enhancing building orthogonality to minimize the distortion of building before converting building footprint into grid data. This study aims to develop building generalization method for 2-dimensional inundation analysis to enhance the model reliability, and to investigate the effect of building generalization method on urban inundation in terms of geographical engineering and hydraulic engineering. As a result to improve the reliability of 2-dimensional inundation analysis, the building generalization method developed in this study should be adapted using Digital Building Model(DBM) before model implementation in urban area. The proposed building generalization sequence was aggregation-simplification, and the threshold of the each method should be determined by considering spatial characteristics, which should not exceed the summation of building gap average and standard deviation.

Buckling Analysis of Laminated Composite Plates Longitudinally Stiffened with U-Shaped Ribs (축방향 압축을 받는 폐단면리브로 보강된 복합적층판의 좌굴 해석연구)

  • Choi, Byung-Ho;Choi, Su-Young;Park, Sang-Kyun
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.3 no.1
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    • pp.29-34
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    • 2012
  • Even though the longitudinally stiffened laminated composite plates with closed section ribs should be an effective system for axially compressed members, the existing researches on the applications of closed-section ribs, especially for the laminated composite plates, are not sufficient. This study is aimed to examine the influence of the sectional stiffness of U-shaped ribs on the buckling modes and strengths of laminated composite plates. Applying the orthotropic plates with eight layers of the layup $[(0^{\circ})_4]_s$ and $[(0^{\circ}/90^{\circ})_2]_s$, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. From the parametric studies, the minimum required ply thicknesses as well as the buckling strengths were presented for the analysis models. The buckling strengths were compared with the theoretical critical stress equation for simply supported plates based on the Classical laminated plate theory. This study will contribute to the future study for evaluating the minimum required stiffness and optimum design of U-rib stiffened plates.

Spherical Slepian Harmonic Expression of the Crustal Magnetic Vector and Its Gradient Components (구면 스레피안 함수로 표현된 지각 자기이상값과 구배 성분)

  • Kim, Hyung Rae
    • Economic and Environmental Geology
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    • v.49 no.4
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    • pp.269-280
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    • 2016
  • I presented three vector crustal magnetic anomaly components and six gradients by using spherical Slepian functions over the cap area of $20^{\circ}$ of radius centered on the South Pole. The Swarm mission, launched by European Space Agency(ESA) in November of 2013, was planned to put three satellites into the low-Earth orbits, two in parallel in East-West direction and one in cross-over of the higher altitude. This orbit configuration will make the gradient measurements possible in North-South direction, vertical direction, as well as E-W direction. The gravity satellites, such as GRACE and GOCE, have already implemented their gradient measurements for recovering the accurate gravity of the Earth and its temporal variation due to mass changes on the subsurface. However, the magnetic gradients have little been applied since Swarm launched. A localized magnetic modeling method is useful in taking an account for a region where data availability was limited or of interest was special. In particular, computation to get the localized solutions is much more efficient and it has an advantage of presenting high frequency anomaly features with numbers of solutions fewer than the global ones. Besides, these localized basis functions that were done by a linear transformation of the spherical harmonic functions, are orthogonal so that they can be used for power spectrum analysis by transforming the global spherical harmonic coefficients. I anticipate in scientific and technical progress in the localized modeling with the gradient measurements from Swarm and here will do discussion on the results of the localized solution to represent the three vector and six gradient anomalies over the Antarctic area from the synthetic data derived from a global solution of the spherical harmonics for the crustal magnetic anomalies of Swarm measurements.

Modeling Three-dimensional Free Surface Flow around Thin Wall Incorporation Hydrodynamic Pressure on δ-coordinate (δ-좌표계에서 동수압 계산 수중벽체 인근흐름 수치모형실험)

  • Kim, Hyo-Seob;Yoo, Ho-Jun;Jin, Jae-Yul;Jang, Chang-Hwan;Lee, Jung-Su;Baek, Seung-Won
    • Journal of Wetlands Research
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    • v.16 no.3
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    • pp.327-336
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    • 2014
  • Submerged thin walls are extreme case of submerged rectangular blocks, and could be used for many purposes in rivers or coastal zones, e.g. to tsunami. To understand flow characteristics including flow and pressure fields around a specific submerged thin wall a numerical model was applied which includes computation of hydrodynamic pressure on ${\sigma}$-coordinate. ${\sigma}$-coordinate has strong merits for simulation of subcritical flow over mild-sloped beds. On the other hand ${\sigma}$-coordinate is quite poor to treat sharp structures on the bed. There have been a few trials to incorporate dynamic pressure in ${\sigma}$-coordinate by some researchers. One of the previous approaches includes process of sloving the Poisson equation. However, the above method includes many high-order terms, and requires long cpu for simulation. Another method SOLA was developed by Hirt et al. for computation of dynamic pressure, but it was valid for straight grid system only. Previous SOLA was modified for ${\sigma}$-coordinate for the present purpose and was adopted in a model system, CST3D. Computed flow field shows reasonable behaviour including vorticity is much stronger than the upstream and downstream of the structure. The model was verified to laboratory experiments at a 2DV flume. Time-average flow vectors were measured by using one-dimensional electro-magnetic velocimeter. Computed flow field agrees well with the measured flow field within 10 % error from the speed point of view at 5 profiles. It is thought that the modified SOLA scheme is useful for ${\sigma}$-coordinate system.

The Contact and Parallel Analysis of SPH Using Cartesian Coordinate Based Domain Decomposition Method (Cartesian 좌표기반 동적영역분할을 고려한 SPH의 충돌 및 병렬해석)

  • Moonho Tak
    • Journal of the Korean GEO-environmental Society
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    • v.25 no.4
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    • pp.13-20
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    • 2024
  • In this paper, a parallel analysis algorithm for Smoothed Particle Hydrodynamics (SPH), one of the numerical methods for fluidic materials, is introduced. SPH, which is a meshless method, can represent the behavior of a continuum using a particle-based approach, but it demands substantial computational resources. Therefore, parallel analysis algorithms are essential for SPH simulations. The domain decomposition algorithm, which divides the computational domain into partitions to be independently analyzed, is the most representative method among parallel analysis algorithms. In Discrete Element Method (DEM) and Molecular Dynamics (MD), the Cartesian coordinate-based domain decomposition method is popularly used because it offers advantages in quickly and conveniently accessing particle positions. However, in SPH, it is important to share particle information among partitioned domains because SPH particles are defined based on information from nearby particles within the smoothing length. Additionally, maintaining CPU load balance is crucial. In this study, a highly parallel efficient algorithm is proposed to dynamically minimize the size of orthogonal domain partitions to prevent excess CPU utilization. The efficiency of the proposed method was validated through numerical analysis models. The parallel efficiency of the proposed method is evaluated for up to 30 CPUs for fluidic models, achieving 90% parallel efficiency for up to 28 physical cores.

Accurate Localization of Metal Electrodes Using Magnetic Resonance Imaging (자기공명영상을 이용한 금속전극의 정확한 위치 결정)

  • Joe, Eun-Hae;Ghim, Min-Oh;Ha, Yoon;Kim, Dong-Hyun
    • Investigative Magnetic Resonance Imaging
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    • v.15 no.1
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    • pp.11-21
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    • 2011
  • Purpose : Localization using MRI is difficult due to susceptibility induced artifacts caused by metal electrodes. Here we took an advantage of the B0 pattern induced by the metal electrodes by using an oblique-view imaging method. Materials and Methods : Metal electrode models with various diameters and susceptibilities were simulated to understand the aspect of field distortion. We set localization criteria for a turbo spin-echo (TSE) sequence usingconventional ($90^{\circ}$ view) and $45^{\circ}$ oblique-view imaging method through simulation of images with various resolutions and validated the criteria usingphantom images acquired by a 3.0T clinical MRI system. For a gradient-refocused echo (GRE) sequence, which is relatively more sensitive to field inhomogeneity, we used phase images to find the center of electrode. Results : There was least field inhomogeneity along the $45^{\circ}$ line that penetrated the center of the electrode. Therefore, our criteria for the TSE sequence with $45^{\circ}$ oblique-view was coincided regardless of susceptibility. And with $45^{\circ}$ oblique-view angle images, pixel shifts were bidirectional so we can detect the location of electrodes even in low resolution. For the GRE sequence, the $45^{\circ}$ oblique-view anglemethod madethe lines where field polarity changes become coincident to the Cartesian grid so the localization of the center coordinates was more facilitated. Conclusion : We suggested the method for accurate localization of electrode using $45^{\circ}$ oblique-view angle imaging. It is expected to be a novelmethodto monitoring an electrophysiological brain study and brain neurosurgery.