• 한국통신학회논문지
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• 제33권6A호
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• pp.635-642
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• 2008

본 논문에서는 time-varying Rayleigh fading channel에서 분산 안테나 시스템의 최적 전력 분배 기법을 제안한다. 기존 관련 연구에서는 각 기지국으로부터 수신되는 전력의 차이를 기지국간 전력 분배에 고려하지 않았으나, 최근 들어 빠르게 변하는 small scale fading까지 Channel State Information (CSI)로하여 전력 분배를 하는 경우에 대한 연구가 진행되었다. 하지만, 실제 무선통신 환경에서 송수신단간의 거리 차이 때문에 피드백이 반영된 신호가 수신될 때의 페이딩 채널은 피드백을 하는 시점과는 차이가 있고, 이로 인한 성능저하가 나타난다. 본 논문에서는 이러한 성능저하를 극복하고 CSI 피드백의 부담을 경감시키기 위하여 small scale fading을 제외하고, 느리게 변하는 경로손실과, 섀도잉에 의한 large scale fading값만을 피드백하는 분산 안테나 시스템을 제안하고 Bit Error Rate (BER)을 최소화하기 위한 최적 전력 분배 공식을 유도했다. 빠른 페이딩 환경에서, 제안된 최적 전력 분배 기법이 small scale fading까지 고려한 전력 분배 기법보다 월등히 좋은 성능을 보이며, 피드백 지연이 없는 환경에서도 1dB 이내의 성능을 보이는 것을 확인했다. 또한, 본 논문에서 Rayleigh fading channel을 가정하여 유도한 전력 분배 기법이 Line-of-Sight (LOS) 성분의 크기가 작은 Ricean fading channel에서도 최소의 BER과 거의 비슷한 값을 달성함을 보였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2600-2608
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• 2011

The dynamic stability of railway vehicle has been one of the important issues in railway safety. The dynamic simulator has been used in the study about the dynamic stability of railway vehicle and wheel/rail interface. Especially, a small scale simulator has been widely used in the fundamental study in the laboratory instead of full scale roller rig which is not cost effective and inconvenient to achieve diverse design parameters. But the technique for the design of the small scale simulator for the fundamental study about the dynamic characteristics of the wheel-rail system and the bogie system has not been well developed in Korea. Therefore, the research about the development of the small scale simulator and the bogie has been conducted. As this paper, To predict the dynamic behavior of railway vehicle, we studied running stability test of 1/5 scaled bogie that similarity laws is applied using small scale derailment simulator. For the operation of the small scale derailment simulator, it is required to investigate the performance and characteristics of the system. This could be achieved by a comparative study between an analysis and an experiment. This paper presented the analytical model which could be used for verifying of the test results and understanding of the physical behavior of the dynamic system comprising the small scale bogie and the simulator.

• 한국실내디자인학회논문집
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• 제23권3호
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• pp.212-221
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• 2014

This study aims to analyze and explore phenomenological elements that appear in small-scall art museums with spatial concepts, such as top and bottom, depth, movement, and experienced space on the basis of Merleau-Ponty $Ph\acute{e}nom\acute{e}nologie$ de la perception.' Therefore, small-scale art museums may be regarded as an ideal space that can be analyzed with Merleau-Ponty's phenomenological theory since they should provide viewers with various spatial experiences in a limited space, breaking away from spatial limitations beyond appreciation of artworks. As research subjects, the range of art museums was limited to ones whose designs architectures or interior designers participated in out of all the small-scale art museums constructed after the 1990s, when the concepts and directing methods of spatial experience elements started being applied to art museums. Small-scale art museums chosen as cases were analyzed with Merleau-Ponty's spatial concepts explained earlier, and this study drew conclusions for each one. The significance of this study is that the results of this study can be used as efficient materials to reflect phenomenological elements on planning future small-scale art museums through further studies on various small-scale art museums.

• 전기학회논문지P
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• 제62권4호
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• pp.210-215
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• 2013

This paper analyze the bus voltage sags in the power distribution system with a small scale cogeneration system when the superconducting fault current limiter was introduced. Among the solutions to decrease the short-circuit current considering the locations of the small scale cogeneration system, the superconducting fault current limiter (SFCL) has been announced as one of the promising methods to reduce the fault current because the installation of the small scale cogeneration system which increases the short-circuit current. According to the application locations of the small scale cogeneration system in a power distribution system, it has caused the variations of voltage sag and duration which depends on the change of the short-circuit current, which can make the operation of the protective device deviate from its original set value when the fault occurs. To investigate the voltage sag when a SFCL was applied into a power distribution system where the small scale cogeneration system was introduced into various locations, the SFCL, small scale cogeneration system, and power system are modeled using PSCAD/EMTDC. In this paper, the effects on voltage sags are assessed when the SFCL is installed in power distribution system with various locations of the small scale cogeneration system.

• Steel and Composite Structures
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• 제20권5호
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• pp.1119-1131
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• 2016

As a first attempt, an inverse hybrid numerical method for small scale parameter estimation of functionally graded (FG) nanobeams using measured frequencies is presented. The governing equations are obtained with the Eringen's nonlocal elasticity assumptions and the first-order shear deformation theory (FSDT). The equations are discretized by using the differential quadrature method (DQM). The discretized equations are transferred from temporal domain to frequency domain and frequencies of the nanobeam are obtained. By applying random error to these frequencies, measured frequencies are generated. The measured frequencies are considered as input data and inversely, the small scale parameter of the beam is obtained by minimizing a defined functional. The functional is defined as root mean square error between the measured frequencies and calculated frequencies by the DQM. Then, the conjugate gradient (CG) optimization method is employed to minimize the functional and the small scale parameter is obtained. Efficiency, convergence and accuracy of the presented hybrid method for small scale parameter estimation of the beams for different applied random error, boundary conditions, length-to-thickness ratio and volume fraction coefficients are demonstrated.

• 한국경제지리학회지
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• 제14권4호
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• pp.568-582
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• 2011

본 연구에서는 소무역을 둘러싼 다양한 행위 주체들의 관계를 중심으로 한 중 소무역의 성격을 규명하고, 소무역 활동이 직면하는 불확실성 내지 위험을 극복하기 위해 소무역상들이 동원하는 사회 자본을 중심으로 한 중 소무역의 운영 메커니즘을 밝혀보고자 했다. 한 중 소무역은 비공식적인 성격에도 불구하고 일자리 창출과 지역 경제의 활성화 및 이윤 추구 등 공식 부문이 당면하고 있는 사안들과 맞물리면서, 지방 정부와 세관, 기업, 그리고 해운사 등 공식 부문의 암묵적인 지원과 묵인 속에 운영되고 있다. 또한 한 중 소무역은 타 지역에서와 마찬가지로 그 운영에 있어 가족 네트워크, 민족네트워크, 사회적 네트워크 및 신뢰 등 사회 자본이 중요한 역할을 하는 것으로 나타났다.

• 한국측량학회지
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• 제34권2호
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• pp.171-183
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• 2016

Small-scale maps currently used are made by scanning and editing printed maps and its shortcoming is accumulated errors at the time of editing and low accuracy. TM projection method is used but its accuracy varies. In addition, small-scale maps are made without consideration of usability and compatibility with other scale maps. Therefore, it is necessary to suggest projection and coordinates system improvement methods in consideration of usability and compatibility between data. The results of this study reveal that in order to make the optimum small-scale map, projection that fits the purpose of map usage in each scale, coordinate system and neat line composition should be selected in consideration of interrelation and compatibility with other maps. Conic projection should be used to accurately illustrate the entire country, but considering usability and compatibility with other maps, traversing cylindrical projection should be used instead of conic projection. For coordinates system of the small-scale map, Universal Transverse Mercator (UTM-K) based on the World Geodetic System should be used instead of conventional longitude and latitude coordinate system or Transverse Mercator.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.545-552
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• 2006

Small-scale models have been frequently used for seismic performance tests because of limited testing facilities and economic reasons. However, there are not also enough studies on similitude law for analogizing prototype structures accurately with small-scale models, although conventional similitude law based on geometry similitude is not well consistent in their inelastic seismic behaviors. When fabricating prototype and small-scale model of reinforced concrete structures by using the same material, added mass is demanded from a volumetric change and scale factor could be limited due to aggregate size. Therefore, it is desirable to use different materials for small-scale model. In our recent study, a modified similitude law was derived depending on geometric scale factor, equivalent modulus ratio and ultimate strain ratio. And quasi-static and pseudo-dynamic tests on the specimens are carried out using constant and variable modulus ratios, and correlation between prototype and small-scale model is investigated based on their test results. In this study, tests on scaled model of different concrete compressive strength aye carried out. In shaking table tests, added mass can not be varied. Thus, constant added mass on expected maximum displacement was applied and the validity was verified in shaking table tests. And shaking table tests on non-artificial mass model is carried out to settle a limitation of acceleration and the validity was verified in shanking table tests.

• 대한기계학회논문집
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• 제14권3호
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• pp.636-645
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• 1990

본 연구에서는 전보에서 수행한 이론해석의 결과를 실험결과에 적용하여 세라 믹의 마멸형태를 파괴역학적 견지에서 고찰하고, 새로운 세라믹의 마멸이론과 마멸평 가를 위한 파라메타를 제안하고자 한다.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.407-420
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• 2019

In the present work, an attempt is made to explore the effects of shear in-plane preload on the wave propagation response of small-scale plates containing nanofibers. The small-scale system is assumed to be embedded in an elastic matrix. The nonlocal elasticity is utilized in order to develop a size-dependent model of plates. The proposed plate model is able to describe both nanofiber effects and the influences of being at small-scales on the wave propagation response. The size-dependent differential equations are derived for motions along all directions. The size-dependent coupled equations are solved analytically to obtain the phase and group velocities of the small-scale plate under a shear in-plane preload. The effects of this shear preload in conjunction with nanofiber and size effects as well as the influences of the elastic matrix on the wave propagation response are analyzed in detail.