• 전력전자학회논문지
• /
• 제25권6호
• /
• pp.503-510
• /
• 2020

The importance of DC breakers as key protection equipment is increasing in accordance with growing concerns on MVDC distribution network systems without DC/AC conversion. Different from the situation in AC systems, no natural zero-crossing point exists in DC systems. Thus, DC breaker technology is more difficult than AC breaker technology. The solutions for DC breakers can be divided into three types: mechanical, power electronics, and hybrid. In this study, the operating principles of several topologies of hybrid circuit breakers and that of the proposed DC breaker are analyzed and simulated by sorting two types. The breakers are compared in terms of the type and number of semiconductors, volume, power loss, auxiliary components, isolation, and other aspects. The advantages and disadvantages of the breakers are also analyzed.

• 유통과학연구
• /
• 제8권2호
• /
• pp.13-22
• /
• 2010

기업이 고객을 차별화하기 시작한 것은 고객관계관리가 확산되면서부터이다. CRM이 확산된 배경에는 마케팅활동이 브랜드중심에서 고객중심으로 옮겨가면서 고객관계와 고객자산의 중요성이 크게 부각되었고, IT를 기반으로 하여 고객정보를 획득하고 관리하며, 모형화 할 수 있는 능력이 경쟁우위를 지속하는데 핵심요소가 되었기 때문이다. 그러나 최근 CRM의 효과에 대한 회의론이 퍼지면서 학계와 실무진에서는 어떤 경우에 CRM의 성과가 나타나고, 어떤 경우에 실패하는가에 대한 연구가 활발히 이루어지고 있다. 저자들 또한 CRM 성과에 지대한 영향을 미칠 것이라고 생각되는 유통정보기술의 역할에 따라 기업의 CRM 성과가 어떻게 달라지는가를 검증하고자 하였다. 따라서 본 연구에서는 CRM 성과에 영향을 미치는 선행변수인 유통정보기술 요인으로 IT기술투자, IT 시스템 활용, Website 활용, 그리고 커뮤니케이션 등을 설정하였다. 본 연구는 CRM 성과는 IT 기술투자, IT 시스템 활용과 커뮤니케이션에 영향을 받을 수 있음을 가설로 제시하고, 설문조사 결과를 토대로 실증 분석하였다. 분석결과, IT 기술투자, IT 시스템 활용, 웹사이트 활용이 좋을수록 고객과 조직구성원간의 커뮤니케이션이 향상되는 것으로 분석되었다. 또한 IT 기술투자, IT시스템 활용, 고객과 조직구성원간의 커뮤니케이션이 좋을수록 기업의 CRM 성과는 향상되는 것으로 분석되었다. 마지막으로 본 연구가 갖는 학문적 의미와 관리적 의미를 제시하였다.

• 한국위성정보통신학회논문지
• /
• 제12권1호
• /
• pp.38-42
• /
• 2017

본 논문은 양자 키 분배 시스템에서의 보안성을 증폭시키기 위한 이중 해시 함수의 개념을 소개한다. 양자 오류 정정과 보안사이의 관계를 이용하여 보안성 증폭을 제공하는 것을 보인다. 또한 보안성 증폭 측면에서 접근 방식이 위상 오차 보정 방식이 더 보다 나은 보안성을 제시한다는 것을 보인다. QKD의 대표적인 예인 BB84 프로토콜을 이용하여 유니버셜 해시 함수가 보안성을 강화하는 과정을 설명한다. 마지막으로 결정적인 유니버셜 해시 함수가 메시지의 길이에 의존하지 않고 양자 Pauli 채널에서 보안성을 평가 받는 것을 유도한다.

• 융합보안논문지
• /
• 제21권3호
• /
• pp.3-11
• /
• 2021

현존하는 대부분의 인터넷 보안 프로토콜은 소인수분해 문제의 수학적 복잡도에 기초한 고전적인 암호화 알고리즘에 의존하고 있으나, 이러한 고전 알고리즘은 양자 컴퓨터의 공격에 취약하다고 알려져 있다. 최근 양자 컴퓨팅 기술이 비약적으로 발전하면서 기존 통신의 물리 및 네트워크 계층 보안을 위해 양자키분배 기술을 적용하는 것이 국제적으로 필수적인 과제가 되고 있다. 본 연구에서는 성형 네트워크에 적용하기 위한 plug & play 방식의 양자키분배 장치를 제작하고, 생성된 양자키를 IPSec의 키 교환 과정에 이용함으로써 기존 IPSec 장치와 연동 실험한 결과를 보고하고자 한다.

• 산업경영시스템학회지
• /
• 제24권65호
• /
• pp.81-88
• /
• 2001

In logistics decision making, Key elements in the design of any physical distribution are the location of depots and the distribution of goods from the depots to the customers. Considering open and close the depots, This paper presents a flexible analysis on the combined location-routing problem(LRP) the case for variation capacity of vehicle and customers demands each. The scenario examples are given the use of heuristic(Saving-Drop) in LRP types. The results is useful in apply to the logistics environment changes.

• Journal of Electrical Engineering and Technology
• /
• 제13권3호
• /
• pp.1079-1088
• /
• 2018

A line overload emergency control strategy based on the source-load synergy coefficient is proposed in this paper. First, the definition of the source-load synergy coefficient is introduced. When line overload is detected, the source-load branch synergy coefficient and source-load distribution synergy coefficient are calculated according to the real-time operation mode of the system. Second, the generator tripping and load shedding control node set is determined according to the source-load branch synergy coefficient. And then, according to the line overload condition, the control quantity of each control node is determined using the Double Fitness Particle Swarm Optimization (DFPSO), with minimum system economic loss as the objective function. Thus load shedding for the overloaded line could be realized. On this basis, in order to guarantee continuous and reliable power supply, on the condition that no new line overload is caused, some of the untripped generators are selected according to the source-load distribution synergy coefficient to increase power output. Thus power supply could be restored to some of the shedded loads, and the economic loss caused by emergency control could be minimized. Simulation tests on the IEEE 10-machine 39-bus system verify the effectiveness and feasibility of the proposed strategy.

• Journal of Communications and Networks
• /
• 제18권5호
• /
• pp.688-698
• /
• 2016

In this paper, we investigate the achievable sum rate and energy efficiency of downlink massive multiple-input multiple-output antenna systems with zero-forcing precoding, by taking into account the randomness of user locations. Specifically, we propose two types of non-uniform user distributions, namely, center-intensive user distribution and edge-intensive user distribution. Based on these user distributions, we derive novel tight lower and upper bounds on the average sum rate. In addition, the impact of user distributions on the optimal number of users maximizing the sum rate is characterized. Moreover, by adopting a realistic power consumption model which accounts for the transmit power, circuit power and signal processing power, the energy efficiency of the system is studied. In particular, closed-form solutions for the key system parameters, such as the number of antennas and the optimal transmit signal-to-noise ratio maximizing the energy efficiency, are obtained. The findings of the paper suggest that user distribution has a significant impact on the system performance: for instance, the highest average sum rate is achieved with the center-intensive user distribution, while the lowest average sum rate is obtained with the edge-intensive user distribution. Also, more users can be served with the center-intensive user distribution.

• 한국시뮬레이션학회:학술대회논문집
• /
• 한국시뮬레이션학회 1998년도 The Korea Society for Simulation 98 춘계학술대회 논문집
• /
• pp.101-105
• /
• 1998

A large system predictor, which can perform prediction of sales trend in a huge number of distribution centers, is presented using neural predictive model. There are 20,000 number of distribution centers, and each distribution center need to forecast future demand in order to establish a reasonable inventory policy. Therefore, the number of forecasting models corresponds to the number of distribution centers, which is not possible to estimate that kind of huge number of accurate models in ERP (Enterprise Resource Planning)module. Multilayer neural net as universal approximation is employed for fitting the prediction model. In order to improve prediction accuracy, a sequential simulation procedure is performed to get appropriate network structure and also to improve forecasting accuracy. The proposed simulation procedure includes neural structure identification and virtual predictive model generation. The predictive model generation consists of generating virtual signals and estimating predictive model. The virtual predictive model plays a key role in tuning the real model by absorbing the real model errors. The complement approach, based on real and virtual model, could forecast the future demands of various distribution centers.

• 대한안전경영과학회지
• /
• 제10권1호
• /
• pp.139-144
• /
• 2008

Recently, a multi-facility, multi-product and multi-period industrial production-distribution planning problem has been widely investigated in Supply Chain Management (SCM). One of the key issues in the current SCM research area involves reducing both production and distribution costs. We have developed an optimization model to tackle the above problems under the restricted conditions such as transportation time and a zero inventory. Computational experiments using commercial tool Ms-Excel Solver show that the real size problems we encountered can be solved in reasonable time. The model can be used to decide an appropriate production-distribution planning problem in SCM research area.

• Journal of Power Electronics
• /
• 제16권2호
• /
• pp.685-694
• /
• 2016

This paper presents a reliability assessment model for the power semiconductors used in wind turbine power converters. In this study, the thermal loadings at different timescales of wind speed are considered. First, in order to address the influence of long-term thermal cycling caused by variations in wind speed, the power converter operation state is partitioned into different phases in terms of average wind speed and wind turbulence. Therefore, the contributions can be considered separately. Then, in regards to the reliability assessment caused by short-term thermal cycling, the wind profile is converted to a wind speed distribution, and the contribution of different wind speeds to the final failure rate is accumulated. Finally, the reliability of an actual power converter semiconductor for a 2.5 MW wind turbine is assessed, and the failure rates induced by different timescale thermal behavior patterns are compared. The effects of various parameters such as cut-in, rated, cut-out wind speed on the failure rate of power devices are also analyzed based on the proposed model.