• Title, Summary, Keyword: unreliability

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Navigation control of mobile robot using elliptical world model (타원형 환경 모델을 이용한 이동로보트의 주행 제어)

  • 한재종;이기철;고재원;김현태;이희진;박민용
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.2
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    • pp.21-32
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    • 1997
  • This paper proposes an elliptical world-modeling mehtrod in order to secure the safety of the mobile robot from the unreliability of ultrasonic sensors and to estimate the lateral orientation of the detected objects. This method is advnatageous because the total amount of data that the robot utilizes is reduced when historical and new data are clusterd during each sensing period and also because the objects in the environment can be almost exactly recognized. This paper also proposes a new local path planning algorithm which is divided into four different situations and gudies the robot through the safe local path using dat acollected in elliptical form. This algorithm can help the AMR navigate by allowing it to sum up the virtual vector forces made form the ellipses in order to select a safe subgoal. This local path plannin gmehtod using the elliptical world model has been proved by several navigation experiments.

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Flexible Real Time Embedded System Using RTOS and SOPC (RTOS와 SOPC를 이용한 유연한 실시간 처리 임베디드시스템)

  • Ahn, Sang-Min;Choi, Woo-Chang;Kong, Jung-Shik;Lee, Bo-Hee;Kim, Jin-Geol;Huh, Uk-Youl
    • Proceedings of the KIEE Conference
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    • pp.2843-2845
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    • 2005
  • This paper deals with the design of real-time embedded system using RTOS (real-time operating system) and SOPC (system on a programmable chip). It is, in general, known that RTOS has the problem of time delay caused by the multiple tasks and task management approach. Since the increase in time delay in real-time embedded system makes the overall system have the poor performance or the critical behavior of instability and unreliability, the method employed RTOS and SOPC is proposed to attack the above problems. The proposed system is implemented on the RC-motor controller and is verified by real experiment.

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Study on Framework for Performance Optimization and Synchrony of Transaction-based ERP in Wireless Communication Environments (무선통신 환경에서 트랜잭션 기반의 기업 어플리케이션(ERP)의 성능 최적화와 동기화를 위한 프레임워크 연구)

  • Park Sung-Hoon
    • The Journal of the Korea Contents Association
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    • v.6 no.9
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    • pp.60-66
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    • 2006
  • With the advances of wireless information technology, many application softwares such as ERP gradually has increased. But those application softwares have some serious problems such that performance degradation and concurrency control resulting from the limited bandwidth and unreliability of wireless communication, In this paper, as a solution to take around those limitations, we propose a middleware framework for wireless communication environments.

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Unreliability of Official Population in Korea (우리나라 공식인구의 신뢰성 및 문제점에 대한 고찰)

  • Park, You-Sung;Kim, Kee-Whan;Kim, Seong-Yong
    • Survey Research
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    • v.11 no.2
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    • pp.71-95
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    • 2010
  • Base population, intercensal and postcensal population estimates, and population projections have been regularly published as official populations. Base population is usually made out based on census conducted every 5 or 10 years, and is most important from which intercensal, postcensal estimates, and population projections are derived. We investigate how base population in Korea is made out and then compare it with those of other countries. We also present problems arising from making out base population in Korea.

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Failure Evaluation of The Digital Substation Based on Fault Tree Analysis (FTA에 기반한 디지털 변전소의 고장 분석)

  • Kim, Sung-Hun;Park, Ji-yeol;An, Yong-Ho;Kim, Seok-Kon;Lee, Seung-Hak;Lee, Dong-Ju
    • Proceedings of the KIEE Conference
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    • pp.553-554
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    • 2015
  • This paper presents the selection method of Minimal Cut Sets(MCS) for substation reliability evaluation. We used the Quality solution in order to model the FT for the substation equipment. Quantitative analysis is performed to estimate the probability of top event occurrence and unreliability of the substation component. In this result, it means that reliability indices which can be predict get electricity services and better maintenance in substation management.

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Adaptive Forward Error Correction Scheme for Real-Time Communication in Satellite IP Networks

  • Cho, Sung-Rae
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.4 no.6
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    • pp.1116-1132
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    • 2010
  • In this paper, a new forward error correction (FEC) protocol is proposed for point-to-multipoint satellite links. Link-layer error control protocols in point-to-multipoint satellite links impose several problems such as unreliability and receiver-heterogeneity. To resolve the problem of heterogeneous error rates at different receivers, the proposed scheme exploits multiple multicast channels to which each receiver tunes. The more channels a receiver tunes to, the more powerful error correcting capability it achieves. Based on its own channel condition, each receiver tunes to as many channels as it needs, which prevents from receiving unwanted parities. Furthermore, each receiver saves the decoding time, processing overhead, and processing energy. Performance evaluation shows that the proposed scheme guarantees the target PER while saving energy. The proposed technique is highly adaptive to the channel variation with respect to the throughput efficiency, and provides scalable PER and throughput efficiency.

SVD-LDA: A Combined Model for Text Classification

  • Hai, Nguyen Cao Truong;Kim, Kyung-Im;Park, Hyuk-Ro
    • Journal of Information Processing Systems
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    • v.5 no.1
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    • pp.5-10
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    • 2009
  • Text data has always accounted for a major portion of the world's information. As the volume of information increases exponentially, the portion of text data also increases significantly. Text classification is therefore still an important area of research. LDA is an updated, probabilistic model which has been used in many applications in many other fields. As regards text data, LDA also has many applications, which has been applied various enhancements. However, it seems that no applications take care of the input for LDA. In this paper, we suggest a way to map the input space to a reduced space, which may avoid the unreliability, ambiguity and redundancy of individual terms as descriptors. The purpose of this paper is to show that LDA can be perfectly performed in a "clean and clear" space. Experiments are conducted on 20 News Groups data sets. The results show that the proposed method can boost the classification results when the appropriate choice of rank of the reduced space is determined.

Development of the Mountain Search and Rescue System (MSRS) Based on Ubiquitous Sensor Network

  • Sim, Kyu-won;Lee, Ju-Hee
    • Journal of Korean Society of Forest Science
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    • v.96 no.5
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    • pp.510-514
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    • 2007
  • The main purpose of this study was to develop Mountain Search and Rescue System for enhancing search and rescue operations in the mountains. This study also focused on presenting an alternative to using a cellular phone for requesting rescue due to their unreliability in remote areas. This system is designed to help in the search and rescue of people in emergency situations in the mountains. It is composed of buzzer sensors, environmental information sensors, and a statistical analysis program. A key feature of this system is that it does not require an infrastructure of internet or CDMA networks for its operation in the mountains. The measure for the study was conducted by using a zigbee protocol analyzer, RF module and 433MHz Helical antenna to analyze the rate of data reception in relation to the distance between nodes. This system is applicable to mountains provided the distance between nodes is over 100 m and under 150 m.

A Prediction of Number of Patients and Risk of Disease in Each Region Based on Pharmaceutical Prescription Data (의약품 처방 데이터 기반의 지역별 예상 환자수 및 위험도 예측)

  • Chang, Jeong Hyeon;Kim, Young Jae;Choi, Jong Hyeok;Kim, Chang Su;Aziz, Nasridinov
    • Journal of Korea Multimedia Society
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    • v.21 no.2
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    • pp.271-280
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    • 2018
  • Recently, big data has been growing rapidly due to the development of IT technology. Especially in the medical field, big data is utilized to provide services such as patient-customized medical care, disease management and disease prediction. In Korea, 'National Health Alarm Service' is provided by National Health Insurance Corporation. However, the prediction model has a problem of short-term prediction within 3 days and unreliability of social data used in prediction model. In order to solve these problems, this paper proposes a disease prediction model using medicine prescription data generated from actual patients. This model predicts the total number of patients and the risk of disease in each region and uses the ARIMA model for long-term predictions.

Probabilistic Estimation of LMR Fuel Cladding Performance Under Transient Conditions

  • Kwon, Hyoung-Mun;Lee, Dong-Uk;Lee, Byung-Oon;Kim, Young ll;Kim, Yong-Soo
    • Nuclear Engineering and Technology
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    • v.35 no.2
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    • pp.144-153
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    • 2003
  • The object of this paper is the probabilistic failure analysis on the cladding performance of WPF(Whole Pin Furnace) test fuel pins under transient conditions, and analysis of the KALIMER fuel pin using the preceding analysis. The cumulative damage estimation and Weibull probability estimation of WPF test are performed. The probabilistic method was adapted for these analyses to determine the effective thickness thinning due to eutectic penetration depth. In the results, it is difficult to assume that a brittle layer depth made by eutectic reaction is all of the thickness reduction due to cladding thinning. About 93% cladding thinning of the eutectic penetration depth is favorable as an effective thickness of cladding. And the unreliability of the KALIMER driver fuel pin under the same WPF test condition is lower than that of the WPF pin because of the higher plenum-fuel volume ratio and lower cladding inner radius vs. thickness ratio. KALIMER fuel pin developed from conceptual design has a more stable transient performance for a failure mechanism due to fission gas buildup than the WPF pin.