• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.533-534
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• 2006

Micro-source units having power ratings in thousands of watts can provide power quality with higher reliability and efficiency than the conventional large scale units. This paper develops switching level model of micro-source and studies the characteristics of the micro-grid consisting of multiple micro-sources and interfaced with electric power system. The developed model adopts the space vector PWM to fully utilize the capacity of inverter. The interaction of the grid connected micro-sources and the characteristics of the control system parameters are investigated. Micro-sources and micro-grid are implemented using PSCAD/EMTDC. Simulation results show that the proposed model is efficient for studying micro-grid system.

• 한국통신학회논문지
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• 제22권8호
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• pp.1659-1667
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• 1997

In DS-CDMA cellular systems, using the same frequency channel at the adjacent cells simultaneously makes soft handoff possible. In soft handoff, mobiles use multiple radio resources for the space diversity of signal in the overlapped region. The previous traffic models of hard handoff are not applicable to the system with soft handoff due to switching radio channels in that region. The handoff rate can be calculated by the mobility of mobiles, which is a function of the size and shape of a cell, and the speed and density of the mobiles. In this paper, we propose an analytical traffic model to study the soft handoff rate. We assume that the system uses a two-way handoff scheme for practical purposes, which connects only two cells to a mobile during soft handoff. We performed a computer simulation to confirm the accuracy of the proposed soft handoff model. The simulation results show good agreement with the analytical model.

• 한국정보처리학회논문지
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• 제7권9호
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• pp.2815-2826
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• 2000

본 논문은 ATM교환 시스템과 같은 실시간 분산 소프트웨어를 범용 컴퓨터 시스템에서 실행할 수 있는 환경을 제공하는 CHILL 실행시간 지원 시스템(CHILL, Run-time System)의 설계 및 구현 기술에 관하여 기술한다. 이를 위하여 실시간 분산 CHILL 프로그램을 위한 실행 모델을 제시하고 해당 실행 모델을 갖는 소프트웨어를 범용 컴퓨터에서 실행하는 CRS를 개발하였다. CRS는 목적 시스템 운영체제와 동일한 실행환경을 호스트 컴퓨터에서 제공함으로 프로그래머는 목적 시스템이 없이도 소프트웨어 개발이 가능하다. 또한 다수의 개발자가 동시에 소프트웨어를 실행할 수 있는 환경을 제공하여 프로그램 생산성 향상에 도움이 된다. 이 실행환경은 SROS(Scalable Real-time Operating System)를 위하여 개발되었지만 다른 내장형 운영체제의 실행환경으로 확장이 용이하다.

• 한국IT서비스학회지
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• 제15권3호
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• pp.247-263
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• 2016

The purpose of the study is to derive success factors of B2C reverse auction business model, a business model contributes to the recent innovative practices in e-commerce and service sector. Electronic reverse auction has been traditionally used to ensure the procurement convenience and purchasing efficiency in B2B or B2G settings, however, e-RA is now expanding its basis toward B2C commerce industry along the huge success of an online e-RA travel service provider Priceline.com. Recently, B2C e-RA business model is getting the spotlight in the Korean venture industry with a variety of startups in diverse areas. However, e-RA does not work perfect in all kinds of trade settings. Therefore, we conducted a multiple case study to find out the success factors of B2C business model as follows : First, large supplier basis is an important factor that constructs a quasi-perfect competition environment. Second, the high online and mobile accessibility or e-readiness of Korean consumers was also a critical aspect of the success of e-RA. Lastly, e-RA performs best when the supplier switching cost is low and the trading occurs infrequently.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권10호
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• pp.5035-5057
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• 2019

Advancements in nanotechnology and novel nano materials in the past decade have provided a set of tools that can be used to design and manufacture integrated nano devices, which are capable of performing sensing, computing, data storing and actuation. In this paper, we have proposed cooperative nano communication using Power Switching Relay (PSR) Wireless Power Transfer (WPT) protocol and Time Switching Relay (TSR) WPT protocol over independent identically distributed (i.i.d.) Rayleigh fading channels in the Terahertz (THz) Gap frequency band to increase the range of transmission. Outage Probability (OP) performances for the proposed cooperative nano communication networks have been evaluated for the following scenarios: A) A single decode-and-forward (DF) relay for PSR protocol and TSR protocol, B) DF multi-relay network with best relay selection (BRS) for PSR protocol and TSR protocol, and C) DF multi-relay network with multiple DF hops with BRS for PSR protocol and TSR protocol. The results have shown that the transmission distance can be improved significantly by employing DF relays with WPT. They have also shown that by increasing the number of hops in a relay the OP performance is only marginally degraded. The analytical results have been verified by Monte-Carlo simulations.

• 조명전기설비학회논문지
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• 제13권1호
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• pp.60-68
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• 1999

본 논문은 미지이거나 변화하는 산업용 로봇 매니퓰레이터의 추종문제를 다룬다. 제시된 방법은 간접적응 제어기 구조를 근거로 퍼지추론에 의한 스위칭 구조를 통해 다중모델 적응제어기를 설계하고자 한다. 매니퓰레이터 한 개의 식별기를 이용한 다중 식별기들은 미지 관성 파라미터와 부하무게의 초기 추정치를 제외하고는 동일하다. 관절 액츄에이터에 가해진 토크입력은 매순간 로봇 동적시스템의 가장 근접한 식별기 모델에 의해 결정된다. 제시된 방법을 이용하여 용접라인 및 부품조립 자동화 설비 등의 적용 예로서 산업용 로봇 매니퓰레이터의 추종성능이 개선됨을 컴퓨터 모의 실험을 통해 보인다.

• Journal of Information Processing Systems
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• 제7권4호
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• pp.679-690
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• 2011

In this paper we consider a local area network (LAN) of dual mode service where one is a token bus and the other is a carrier sense multiple access with a collision detection (CSMA/CD) bus. The objective of the paper is to find the overall cell/packet dropping probability of a dual mode LAN for finite length queue M/G/1(m) traffic. Here, the offered traffic of the LAN is taken to be the equivalent carried traffic of a one-millisecond delay. The concept of a tabular solution for two-dimensional Poisson's traffic of circuit switching is adapted here to find the cell dropping probability of the dual mode packet service. Although the work is done for the traffic of similar bandwidth, it can be extended for the case of a dissimilar bandwidth of a circuit switched network.

• 한국통신학회논문지
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• 제30권4A호
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• pp.259-270
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• 2005

본 논문에서는 비대칭적이고 불균질적인 트래픽이 혼재하는 멀티미디어 서비스 환경에서 시분할 듀플렉싱을 사용하는 시분할-코드분할 다중 접속(TD-CDMA) 시스템의 직교 코드와 시간의 2차원적인 자원을 효율적으로 운용하는 방법을 수학적 모델링을 통해서 알아본다. 호-계층에서는 상/하향 트래픽 부하를 2차원 벡터로 나타내어 대기 이론을 기반으로 하여 호손율을 구하며, 최소의 호손율을 보이는 최적의 스윗칭-포인트를 찾는다. 패킷-계층에서는 서킷호와 패킷호로 구분하여 대기 중인 패킷과 서비스 중인 서킷호를 2차원의 상태로 나타내어 패킷 손실율을 구한다. 또한 일정 수준 이상의 서비스 품질을 위해 요구되는 버퍼 크기를 알아본다.

• Asia pacific journal of information systems
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• 제20권1호
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• pp.127-140
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• 2010

The benefit that a consumer derives from the use of a good often depends on the number of other consumers purchasing the same goods or other compatible items. This property, which is known as network externality, is significant in many IT related industries. Over the past few decades, network externalities have been recognized in the context of physical networks such as the telephone and railroad industries. Today, as many products are provided as a form of system that consists of compatible components, the appreciation of network externality is becoming increasingly important. Network externalities have been extensively studied among economists who have been seeking to explain new phenomena resulting from rapid advancements in ICT (Information and Communication Technology). As a result of these efforts, a new body of theories for 'New Economy' has been proposed. The theoretical bottom-line argument of such theories is that technologies subject to network effects exhibit multiple equilibriums and will finally lock into a monopoly with one standard cornering the entire market. They emphasize that such "tippiness" is a typical characteristic in such networked markets, describing that multiple incompatible technologies rarely coexist and that the switch to a single, leading standard occurs suddenly. Moreover, it is argued that this standardization process is path dependent, and the ultimate outcome is unpredictable. With incomplete information about other actors' preferences, there can be excess inertia, as consumers only moderately favor the change, and hence are themselves insufficiently motivated to start the bandwagon rolling, but would get on it once it did start to roll. This startup problem can prevent the adoption of any standard at all, even if it is preferred by everyone. Conversely, excess momentum is another possible outcome, for example, if a sponsoring firm uses low prices during early periods of diffusion. The aim of this paper is to analyze the dynamics of the adoption process in markets exhibiting network effects by focusing on two factors; switching and agent heterogeneity. Switching is an important factor that should be considered in analyzing the adoption process. An agent's switching invokes switching by other adopters, which brings about a positive feedback process that can significantly complicate the adoption process. Agent heterogeneity also plays a important role in shaping the early development of the adoption process, which has a significant impact on the later development of the process. The effects of these two factors are analyzed by developing an agent-based simulation model. ABM is a computer-based simulation methodology that can offer many advantages over traditional analytical approaches. The model is designed such that agents have diverse preferences regarding technology and are allowed to switch their previous choice. The simulation results showed that the adoption processes in a market exhibiting networks effects are significantly affected by the distribution of agents and the occurrence of switching. In particular, it is found that both weak heterogeneity and strong network effects cause agents to start to switch early and this plays a role of expediting the emergence of 'lock-in.' When network effects are strong, agents are easily affected by changes in early market shares. This causes agents to switch earlier and in turn speeds up the market's tipping. The same effect is found in the case of highly homogeneous agents. When agents are highly homogeneous, the market starts to tip toward one technology rapidly, and its choice is not always consistent with the populations' initial inclination. Increased volatility and faster lock-in increase the possibility that the market will reach an unexpected outcome. The primary contribution of this study is the elucidation of the role of parameters characterizing the market in the development of the lock-in process, and identification of conditions where such unexpected outcomes happen.

• 조명전기설비학회논문지
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• 제20권3호
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• pp.12-19
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• 2006

마이크로소스는 1[kW]${\sim}$수[MW] 사이의 전력을 공급하고, 기존의 대규모 발전설비보다 높은 신뢰도와 에너지 효율을 가지는 고품질의 전력을 공급할 수 있다. 본 논문에서는 마이크로소스의 스위칭레벨 모델을 개발하였으며, 다수의 마이크로소스가 전력시스템과 연계되어 마이크로그리드를 형성할 경우의 특성에 대하여 연구하였다. 마이크로소스는 인버터의 효율을 극대화 할 수 있도록 공간벡터 펄스폭변조(Space Vector PWM, SVPWM) 기법을 채용하였으며, 마이크로소스의 제어시스템 파라미터 특성 및 마이크로소스 상호작용에 관하여 연구하였다. 마이크로소스는 PSCAD/EMTDC를 이용하여 구현하였으며 이를 이용해 마이크로그리드를 구성하여 시뮬레이션하였다. 사례 연구를 통하여 제안된 모델의 효용성을 확인하였다.