• 한국위성정보통신학회논문지
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• 제8권3호
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• pp.6-9
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• 2013

Cognitive Radio는 유휴 스펙트럼을 찾아 환경에 맞는 통신방식과 주파수 대역폭을 능동적으로 판단해 재활용하는 지능적인 간섭회피로 방식으로 스펙트럼을 공유하여 전파자원효율을 극대화 하는 기술이다. 이때 PU에 간섭을 일으키지 않기 위한 스펙트럼 센싱 기술이 중요하다. 하지만 상황에 따라 스펙트럼 센싱 알고리즘을 선택할수 있다면 좀더 효율적 센싱을 할수 있을 것이다. 따라서 본 논문에서는 퍼지컨트롤러를 통해 에너지검출, 자기상관검출,M atched filter 검출 등을 개별 센싱에 반영하는 시스템 모델을 제안하고 분석한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.266-269
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• 2004

A satellite ground control system (SGCS) which monitors and controls a geostationary satellite 24 hours a day has to achieve the system architecture assuring high-level availability and redundancy scheme. The SGCS for Communication, Ocean, and Meteorological Satellite (COMS) is currently being developed in Korea, which will be implemented to satisfy high availability (HA), expansibility, and compatibility in design. In order to implement the system architecture to meet these characteristics, the SGCS for COMS introduces the concept of the real-time distributed system structure based on redundancy scheme for high availability, data replication and sharing, and CORBA middleware.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.449-452
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• 2005

For home networking system with a function of air quality monitoring, a wireless sensor module with several air quality monitoring sensors was developed for indoor environment monitoring system in home networking. The module has various enlargements for various kinds of sensors such as humidity sensor, temperature sensor, CO2 sensor, flying dust sensor, and etc. The developed wireless module is very convenient to be installed on the wall of a room or office, and the sensors in the module can be easily replaced due to well designed module structure and RF connection method. To reduce the system cost, only one RF transmission block was used for sensors' signal transmission to 8051 microcontroller board in time sharing method. In this home networking system, various indoor environmental parameters could be monitored in real time from RF wireless sensor module. Indoor vision was transferred to client PC or PDA from surveillance camera installed indoor or desired site. Web server using Oracle DB was used for saving the visions by web-camera and various data from wireless sensor module.

• 대한산업공학회지
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• 제25권2호
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• pp.150-161
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• 1999

This paper deals with the design and development of a real-time integrated communication architecture for heterarchical SFCS(Shop Floor Control System). In autonomous agent-based heterarchical SFCS, each functional unit of parts and resources is equipped with an intelligent controller (agent) that acts as the representative of the entity. The controllers communicate and negotiate with other controllers on a real-time basis through message passing and bidding protocol to achieve mutual agreements for task sharing. ICPL(Integrated Communication Protocol and Language) is proposed for this purpose. ICPL is a language and a protocol for supporting communication among intelligent controllers. Based on the speech act theory, this paper proposes a semantic description for ICPL that associates the description of the cognitive states of controllers with the use of language primitives (message_type). Semantics for the basic set of ICPL messages is described. Eventually, an ICPL-based communication architecture can provide the implementation of the distributed and heterarchical SFCS, and makes the intelligent controller transparent to the negotiation problem.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 2003년도 춘계학술대회
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• pp.400-409
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• 2003

Collaborative filtering (CF) recommendation is a knowledge sharing technology for distribution of opinions and facilitating contacts in network society between people with similar interests. The main concerns of the CF algorithm are about prediction accuracy, speed of response time, problem of data sparsity, and scalability. In general, the efforts of improving prediction algorithms and lessening response time are decoupled. We propose a three-step CF recommendation model which is composed of profiling, inferring, and predicting steps while considering prediction accuracy and computing speed simultaneously. This model combines a CF algorithm with two machine learning processes, SOM (Self-Organizing Map) and CBR (Case Based Reasoning) by changing an unsupervised clustering problem into a supervised user preference reasoning problem, which is a novel approach for the CF recommendation field. This paper demonstrates the utility of the CF recommendation based on SOM cluster-indexing CBR with validation against control algorithms through an open dataset of user preference.

• 정보처리학회논문지D
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• 제11D권7호
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• pp.1367-1374
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• 2004

XML 트리를 공유하면서 여러 사용자가 동시에 수정할 수 있게 하기 위해서는 부분 트리의 삽입/삭제가 공유될 수 있어야 한다. 이를 위해서는 트리 데이터의 구소 변경 행위에 대한 통시성 제어가 가능해야 한다. 본 논문에서는 DTD 문서 타입 정보를 이용하여 XML 트리의 반복부에 대해서만 부분 트리의 삽입/삭제가 가능한 리스트 데이터 공유 모델을 제안한다. 제안된 리스트 데이터 공유 모델은 구조 변경 행위의 적용 결과가 항상 유효하며, 여러 사용자가 동시에 접근하는 경우에도 문서의 유효성을 보장할 수 있다. 리스트 데이터 공유 모델에서 반복부 자식 노드 리스트를 잠금의 대상으로 하는 리스트 잠금 프로토콜을 제안하였다. 이 잠금 프로토콜은 기존의 방법들과 비교하여 훨씬 간단하면서 적은 수의 잠금 객체만을 다루며, 높은 접근성을 가능하게 한다. 일반적으로 공유되는 XML 트리의 삽입 및 삭제는 흔히 반복부 데이터에 대해서 적용되는 경우가 많으므로 제안된 모델은 터미널 노드 데이터 값에 대한 기존의 접근제어 방법과 함께 사용하였을 때 효과적인 데이터 공유 방법을 제공할 수 있을 것으로 기대된다.

• 한국전자거래학회지
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• 제4권1호
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• pp.87-101
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• 1999

To operate the automatic devices of manufacturing process more effectively and to solve the needs of the resource sharing, network technology is applied to the control devices located in common manufacturing zone and operated by connecting them. In this paper, functional standard of the network layers are set as physical and data link layer of IEEE 802.2, 802.4, and VMD application layer and ISO-CIM reference model. Then, they are divided as minimized architecture, designed as group objects which perform group management and service objects which organizes and operates the group. For the stability in this network, this paper measures the variation of data packet length and node number and analyzes the variated value of the waiting time for the network operation. For the method of the analysis, non-exhausted service method are selected, and the arrival rates of the each data packet to the nodes that are assumed to form a Poission distribution. Then, queue model is set as M/G/1, and the analysis equation for waiting time is found. For the evalution of the performance, the length of the data packet varies from 10 bytes to 100 bytes in the operation of the group management network, the variation of the wating time is less than 10 msec. Since the waiting time in this case is less than 10 msec, response time is fast enough. Furthermore, to evaluate the real time processing of the group management network, it shows if the number of nodes is less than 40, and the average arrival time is less than 40 packet/sec, it can perform stable operation even taking the overhead such as software delay time, indicated packet service, and transmissin safety margin.

• Journal of Power Electronics
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• 제17권2호
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• pp.551-560
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• 2017

The present study proposes an angle droop controller for converter interfaced (dispatchable) distributed generation (DG) resources in the islanded mode of operation. Due to the necessity of proper real and reactive power sharing between different types of resources in microgrids and the ability of systems to respond properly to abnormal conditions (sudden load changes, load uncertainty, load current disturbances, transient conditions, etc.), it is necessary to produce appropriate references for all of the mentioned above conditions. The proposed control strategy utilizes a current controller in addition to an angle droop controller in the discrete time domain to generate appropriate responses under transient conditions. Furthermore, to reduce the harmonics caused by switching at converters' output, a LCL filter is used. In addition, a comparison is done on the effects that LCL filters and L filters have on the performance of DG units. The performance of the proposed control strategy is demonstrated for multi islanded grids with various types of loads and conditions through simulation studies in the DigSilent Power Factory software environment.

• The Journal of Asian Finance, Economics and Business
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• 제4권4호
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• pp.17-26
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• 2017

Many workers today encounter the problem of overemployment which occurs when actual working hours exceed preferred or desired working hours. Overemployed workers desire to work fewer hours although this may entail a concomitant decline in earnings. This research is conducted to examine the likelihood of overemployment among employees in a particular state in Malaysia, that is, Penang. This study uses primary data that was collected in a survey encompassing a total of 525 employees in the state. A logit model is used to analyse the relationship between the likelihood of overemployment and various socio-demographic, household and work-related variables. The factors that are significantly related to overemployment are ethnicity, age, education, number of children in the household, occupation, hours of work and control over work schedule. Based on the findings of this paper, it is suggested that policies such as offering part-time jobs or job-sharing options to older workers, implementing family-friendly policies, adopting decent working time measures and strategies that give workers more control over their work schedule are some possible ways to deal with the issue of overemployment.

• 디지털콘텐츠학회 논문지
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• 제3권1호
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• pp.47-57
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• 2002

최근, 정보 통신 기술의 발전에 따라 무선 통신망에서 음성, 데이터, 정지화면, 동영상 및 다양한 멀티미디어 데이터를 추구하고 있다. 효율적인 실시간 멀티미디어 데이터 전송을 위해서는 실시간 데이터의 지연 한계를 보장하고 비실시간 멀티미디어 데이터의 데이터 손실을 최소화해야 한다. 무선 ATM은 유선 ATM을 기본으로 하고 있지만 무선 환경에서의 다양한 서비스에 대한 힘든 전송률과 품질에 따른 문제점들이 수반된다. 그 결과, 무선 통신 환경에서 각각의 트래픽 종류에 따른 품질 서비스(QoS)를 보장하는 방법을 찾는 것이 중요하다. 이 논문에서는 무선 ATM망에서 실시간 멀티미디어 데이터 서비스 전송을 위한 스케줄링 방법으로 개선된 TCRM 스케줄링 알고리즘을 제시한다. 무선 환경에 따라 Uplink와 Downlink시 각각 다른 방법으로 실시간 멀티미디어 데이터 전송 스케줄링 정책을 적용하며 실시간 데이터와 비실시간 데이터의 QoS의 요구사항을 보장하고 불충분한 무선 자원을 공유분배를 위한 공평성 문제를 다룬다. 또한 VC(Virtual Control)를 BS(Base Station)에 두어 예약버퍼와 임의의 전송속도 pk를 사용하여 TCRM의 단점인 비실시간 데이터에 대한 비효율성 문제를 해결한다.