• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.62-69
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• 2014

In this paper, WBAN(Wireless Body Area Network) On-body system using the surface-oriented antenna about the impact of human internal organs were analyzed through experiments. The received signal strength is measured for effect of human using the human model and the phantom of torso. Experiments are performed in anechoic chamber without moving and measured by Vector Network Analyzer. This paper confirms the effect of human body by comparing the human model and the phantom of torso. And also know the human internal organs effect on the antennas loss of received signal strength by measured data.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.76-83
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• 1991

자기회귀-이동평균모델에 의하여 시스템의 파라미터를 추정할 수 있는 벡터채널 원형 격자 필터(vector channel circular lattice filter)의 알고리즘을 제시하였다. 이 알고리즘은 스칼라 연산만으로 이루어져 계산이 간단한 장점이 있다. 3자유도 시스템의 시뮬레이션 결과로부터 격자 필터의 성능을 검증하였으며, 1자유도 팔의 고유진동수와 감쇄비를 추정하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.755-764
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• 1999

In this study, the system level network simulation is considered with adaptive array antenna in CDMA mobile communication system. A network simulation framework is implemented based on IS-95A/B system to consider dynamic handoff, system level network behavior, and deploying strategy into the overall CDMA mobile communication network under adaptive array algorithm. Its simulation model, such as vector channel model, adaptive beam forming antenna model, handoff model, and power control model, are described in detail with simulation block. In order to maximize SINR of received signal at antenna, maximin algorithm is particularly considered, and it is computed at each simulation snap shot with SINR based power control and handoff algorithm. Graphic user interface in this system level network simulator is also implemented to define the simulation environments and to represent simulation results on real mapping system. This paper also shows some features of simulation framework and simulation results.

• Journal of the Korea Society for Simulation
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• v.8 no.4
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• pp.33-51
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• 1999

In this study, the system level network simulation is considered with adaptive array antenna in CDMA mobile communication system. A network simulation framework is implemented based on IS-95A/B system to consider dynamic handoff, system level network behavior, and deploying strategy into the overall CDMA mobile communication network under adaptive array algorithm. Its simulation model, such as vector channel model, adaptive beam forming antenna model, handoff model, and power control model, are described in detail with simulation block. In order to maximize SINR of received signal at antenna, Maximin algorithm is particularly considered, and it is computed at each simulation snap shot with SINR based power control and handoff algorithm. Graphic user interface in this system level network simulator is also implemented to define the simulation environments and to represent simulation results on real mapping system. This paper also shows some features of simulation framework and simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2335-2339
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• 2003

To prevent the critical situation due to the fault in the aircraft sensor system, the fault tolerant system with triple or quadruple redundancy can be made. However, if the faults are occurred in two or more than sensors simultaneously, the conventional fault detection process, such as cross-channel monitoring, may give the wrong fault alarm. For this case, we can detect the fault by estimating the state vector based on the system dynamics model, which is nonlinear for aircraft. In this paper, we propose the unscented Kalman filter to estimate the nonlinear state vector. This filter utilizes the so-called unscented transformation of sigma points featured the statistical characteristics of the random variable. For verification, we perform the simulations for F-16 aircraft with accelerometers, gyros, GPS and air data system.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.59-70
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• 1998

Two-dimensional trend-vector model of sediment transport is first tested in the tidal flat of Garolim Bay, mid-western coast of the Korean Peninsula. Three major parameters of surface sediment, i.e., mean grain size, sorting and skewness, are used for defining the best-fitting transport trend-vector on the sand ridge and muddy sand flat. These trend vectors are compared with the real transport directions determined from morphology, field observation and bedforms. The 15 possible cases of trend vectors are calculated from total sediments. In order to find the role of coarse sediments, trend vectors from sediments coarser than < 4.5 ${\phi}$, (sand size) are separately calculated from those of total sediments. As compared with the real directions, the best-fitting transport-vector model is the "case M" of coarse sediments which is the combined trend vectors of two cases: (1) finer, better sorted and more negatively skewed and (2) coarser, better sorted and more positively skewed. This indicates sand-size grains are formed by simpler hydrodynamic processes than total sediments. Transported sediment grains are better sorted than the source sediment grains. This indicates that consistent hydrodynamic energy can make sediment grains better sorted, regardless of complicated mechanisms of sediment transport. Consequently, both transported vector model and real transported direction show that the source of sediments are located outside of bay (offshore Yellow Sea) and in the baymouth. These source sediments are transported through the East Main Tidal Channel adjacent the baymouth. Some are transported from the subtidal zone to the upper tidal flat, but others are transported farther to the south, reaching the south tidal channel in the study area. Also, coarse sediment grains on the sand ridge are originally from the baymouth, and transported through the subtidal zone to the south tidal channel. These coarse sediments are moved to the northeast, but could not pass the small north tidal channel. It is interpreted that the great amount of coarse sediments is returned back to the outside of the bay (Yellow Sea) again through the baymouth during the ebb tide. The distribution of muddy sand in the northeastern part of study area may result from the mixing of two sediment transport mechanisms, i.e., suspension and bedload processes. The landward movement of sand ridge and the formation of the north tidal channel are formed either by the supply of coarse sediments originating from the baymouth and outside of the bay (subaqueous sand ridges including Jang-An-Tae) or by the recent relative sea-level rise.

• Economic Analysis
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• v.25 no.3
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• pp.100-137
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• 2019

In this study, I analyzed the effects of government spending on macro variables and on each industry by using a factor augmented vector autoregressive model (FAVAR) and 167 macro-variables in Korea since 2000. The results reveal that the effects of two types of government spending - government consumption and government investment - greatly differ, therefore it is better to consider the two types of spending separately for a more precise analysis. The stimulus effects of government consumption are clear, but those of government investment are not. In addition, the crowding-out effects of government spending take place through the current account deficit channel rather than the traditional crowding-out channel, reducing private consumption and investment. Both types of government spending show a positive effect on the construction industry. Also, an increase in government consumption stimulates output in various manufacturing and service sectors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.11 s.242
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• pp.1265-1276
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• 2005

The elliptic conceptual second moment models for turbulent heat fluxes, which are proposed on the basis of elliptic-blending and elliptic-relaxation equations, are applied to calculate the combined forced and natural turbulent convection in a vertical plane channel. The models satisfy the near-wall balance between viscous diffusion, viscous dissipation and temperature-pressure gradient correlation, and also have the characteristics of approaching its respective conventional high Reynolds number model far away from the wall. Also the models are closely linked to the elliptic blending model which is used for the prediction of Reynolds stress. In order to calibrate the heat flux models, firstly, the distributions of mean temperature and scala flux in fully developed channel flow with constant wall difference temperature are solved by the present models. The buoyancy effect on the turbulent characteristics including the mean velocity and temperature, the Reynolds stress tensor, and the turbulent heat flux vector are examined. In the opposing flow, the turbulent transport is greatly enhanced with both the Reynolds stresses and the turbulent heat fluxes being remarkably increased; whereas, in the aiding flow, the opposite change is observed. The results of prediction are directly compared to the DNS to assess the performance of the model predictions and show that the behaviors of the turbulent heat transfer in the whole flow region are well captured by the present models.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.4
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• pp.10-15
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• 2017

Feedback burden of a full-digital energy beamforming, which is known as the optimal precoding scheme for radio frequency (RF) energy transfer, is huge because it uses a vector quantization for a channel feedback. To reduce the feedback burden, we consider a beam steering based wireless energy transfer, which uses a scalar quantization. Researches related to the beam steering based wireless energy transfer have been studied in special channel model with an assumption of full channel state information at the transmitter. In this paper, we analyze the beam steering scheme compared with the full-digital energy beamforming for practical channel models with channel estimation errors. According to characteristics of the millimeter wave channel, the number of antennas of the base station and the user, the distance between them, and channel estimation errors, we simulate the performance of the beam steering scheme and analyze reasons why.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2585-2596
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• 1994

Many particle filled materials like Poweder/Binder mixtures for poweder injection moldings, have complicated rheological behaviors such as an yield stress and slip phenomena. In the present study, numerical simulation programs via a finite element method and a finite difference method were developed for the quasi-three-dimensional flows and the two-dimensional flow models, respectively, with the slip phenomena taken into account in terms of a slip velocity. In order to qualitatively understand the slip effects, typical numerical results such as vector plots, pressure contours in the cross-channel plane, and isovelocity controus for the down-channel direction were discussed with respect to various slip coefficients. Slip velocities along the boudary surfaces were also investigated to find the effects of the slip coefficient and processing conditions on the overall flow behavior. Based on extensive numerical calculations varying the slip coefficients, pressure gradient, aspect ratio, and power law index, the screw characteristics of the extrusion process were studied in particular with comparisons between the slip model and non-slip model.