• 대한교통학회지
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• 제8권1호
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• pp.17-24
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• 1990

The first-best pricing rule which achieves economic efficiency is to equate price with marginal cost. Since public transport demand is derived from some other demand, the user cost as well as the producer cost are considered in its pricing. The optimal price is derived from a derivative of the total social cost with respect to demand. In case of the bus, if there is enough capacity for demand increase, the optimal price is determined by the marginal producer cost resulting from bus sped decrease and by the marginal user cost resulting from journey time increase. Both are caused by boarding and fare collecting time of an additional passenger. Because of the budget constraints, the marginal cost pricing cannot be applied in practice. Then price discrimination as the second-best pricing is introduced. The Ramsey pricing, to charge different prices for different demand elasticities, and nonuniform prices such as travelcards can be applied. However, there is practical difficulty in implementing these prices because of great informational requirements, the costs of administration and the ease to users.

• Journal of Communications and Networks
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• 제17권3호
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• pp.265-266
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• 2015

In a recent paper [1], the authors investigated the maximum stable throughput region of a network composed of a rechargeable primary user and a secondary user plugged to a reliable power supply. The authors studied the cases of an infinite and a finite energy queue at the primary transmitter. However, the results of the finite case are incorrect. We show that under the proposed energy queue model (a decoupled M/D/1 queueing system with Bernoulli arrivals and the consumption of one energy packet per time slot), the energy queue capacity does not affect the stability region of the network.

• 한국통신학회논문지
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• 제42권1호
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• pp.39-41
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• 2017

본 논문에서는 무선 다중셀 다중 사용자 네트워크에서 전송용량과 도청용량의 차로 정의되는 기밀용량을 증대시키기 위한 단말의 전력조절 기법을 제안한다. 모의실험 결과를 통해 제안 전력조절 기법과 임계값 기반의 스케줄링의 결합이 다중셀 환경에서 기밀 전송률을 상당히 향상시킬 수 있다는 것을 확인하였다.

• 디지털콘텐츠학회 논문지
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• 제5권3호
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• pp.171-175
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• 2004

본 논문에서는 TH PPM UWB-IR 시스템에서 다중 접속시 발생하는 간섭을 개선하기 위해 CCI canceller를 적용하여 동일 채널 상의 다중 사용자 간섭을 제거하였다. 결과에 의하면, CCI canceller를 적용함으로써 낮은 수신 전력에서도 고속의 데이터 전송이 가능한 수신 성능을 얻을 수 있었고 100Mbps의 고속 전송 시에도 최대 동시 접속 수 40까지 수용이 가능한 채널 용량을 얻을 수 있었다.

• 한국컴퓨터정보학회논문지
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• 제13권1호
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• pp.21-27
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• 2008

소규모 환경에서 크로마키 기법은 UCC 콘텐츠를 제작하는데 매우 필요한 부분이다. 지금까지는 크로마키를 하기 위해 배경에 단일 색을 사용한 막을 사용 하였다. 본 논문은 일반 배경에 객체가 설정 되었을 때 객체를 추출하는 크로마키를 제안한다. 본 논문은 웨이블릿을 이용하여 고주파와 저주파를 분리하여 노이즈를 제거하는 새로운 방법으로 크로마키를 시도 하였다 결과로 성능 좋은 크로마키 기법을 개발하였다.

• ETRI Journal
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• 제27권6호
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• pp.768-776
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• 2005

We compare the achievable throughput of time division multiple access (TDMA) multiple-input multiple-output (MIMO) schemes illustrated in the 3rd Generation Partnership Project (3GPP) MIMO technical report, versus the sum-rate capacity of space-time multiple access (STMA). These schemes have been proposed to improve the 3GPP high speed downlink packet access (HSDPA) channel by employing multiple antennas at both the base station and mobile stations. Our comparisons are performed in multi-user environments and are conducted using TDMA such as Qualcomm's High Data Rate and HSDPA, which is a simpler technique than STMA. Furthermore, we present the unified optimal power allocation strategy for HSDPA MIMO schemes by exploiting the similarity of multiple antenna systems and multi-user channel problems.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1999년도 추계학술대회 논문집
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• pp.93-99
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• 1999

The service level of Metro stations is affected by the design criteria such as platform area, width and length of stairways, and the number of turnstile, etc. The Korean station design process utilizes peak-hour volume as design volume. Hourly volume, however, can not explicitly account for the variation of traffic and consequently the variation of the level of service within the one-hour time period. Movements in various areas inside of stations are simulated with a queueing network under various operating conditions. A discrete simulation tool called SIMUL8 was utilized. Based on the results, peak volume for 15 minutes period was recommended as a preferred base volume over the peak-hour volume for station design purpose to realistically account for user delays under. Simulation runs also confirmed that escalators have positive effects on passenger processing capacity and on securing stability of passenger flows in stations.

• ETRI Journal
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• 제34권3호
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• pp.297-307
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• 2012

A femtocell is a small cellular base station, typically designed for use in a home or small business. The random deployment of a femtocell has a critical effect on the performance of a macrocell network due to co-channel interference. Utilizing the advantage of a multiple-input multiple-output system, each femto base station (FBS) is able to form a cluster and generates a precoding matrix, which is a modified version of conventional single-cell block diagonalization, in a cooperative manner. Since interference from clustered-FBSs located at the nearby macro user equipment (MUE) is the dominant interference contributor to the coexisting networks, each cluster generates a precoding matrix considering the effects of interference on nearby MUEs. Through simulation, we verify that the proposed algorithm shows better performance respective to both MUE and femto user equipment, in terms of capacity.

• 한국정밀공학회지
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• 제20권8호
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• pp.166-174
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• 2003

Hydrostatic bearings are widely used in precision machines due to their high motion guide accuracy, low friction and high load carrying capacity. It is very useful to estimate the moving characteristics of hydrostatic bearings in the design stage. A new method is suggested for the analysis of fluid film in hydrostatic bearings. A combined mesh of 8 node solid elements with negligible deformation resistance and spring-dashpot elements is used in conjunction with the user subroutine of ABAQUS to represent the fluid film. The mesh can be used to capture the deformation of the bearing structure as well as the varying properties of fluid film. Analysis results from the finite element model are compared with theoretical solutions, results from FLUENT analysis and some previous works. With this method, static and dynamic analyses of the system containing the bearings can be performed efficiently.

• 한국통신학회논문지
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• 제34권11A호
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• pp.822-830
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• 2009

The spectrum efficiency of mobile communication networks can be improved dramatically adopting multiple antennas technologies. In order to guarantee the licensed rights of primary user (PU), the cognitive radio system should perform in a relatively low interference manner when it gets access to the spectrum of licensed networks. In this paper, we explore a uniformly distributed circular antenna array to implement beamforming algorithm that is accomplished by optimization method at the base station of cognitive radio networks, and therefore we can suppress the interference to PU by steering quite low transmission power toward PU and constructing a narrow beam toward cognitive user (CU). By reducing the constraint number of the optimization problem, we also propose a null steering algorithm that steers rather low radiation power toward PU, while the other areas in the same cell are covered by radiation power except the local area around PU. It is pursued to reduce the computation load and enlarge the capacity of cognitive radio networks extremely. The simulation results demonstrate that the proposed algorithms process superior performance.