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Optimization of Stream Gauge Network Using the Entropy Theory (엔트로피 이론을 이용한 수위관측망의 최적화)

  • Yoo, Chul-Sang;Kim, In-Bae
    • Journal of Korea Water Resources Association
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    • v.36 no.2
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    • pp.161-172
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    • 2003
  • This study has evaluated the stream gauge network with the main emphasis on if the current stream gauge network can catch the runoff characteristics of the basin. As the evaluation of the stream gauge network in this study does not consider a special purpose of a stream gauge, nor the effect from a hydraulic structure, it becomes an optimization of current stream gauge network under the condition that each stream gauge measures the natural runoff volume. This study has been applied to the Nam-Han River Basin for the optimization of total 31 stream gauge stations using the entropy concept. Summarizing the results are as follows. (1) The unit hydrograph representing the basin response from rainfall can be transferred into a probability density function for the application of the entropy concept to optimize the stream gauge network. (2) Accurate derivation of unit hydrographs representing stream gauge sites was found the most important part for the evaluation of stream gauge network, which was assured in this research by comparing the measured and derived unit hydrographs. (3) The Nam-Han River Basin was found to need at least 28 stream gauge stations, which was derived by considering both the shape of the unit hydrograph and the runoff volume. If considering only the shape of the unit hydrograph, the number of stream gauges required decreases to 23.

Analysis of Correlation between Construction Business and Insolvency of Construction Company (건설경기와 건설업체 부실화 간의 관계성 분석)

  • Seo, Jeong-Bum;Lee, Sang-Hyo;Kim, Jae-Jun
    • Korean Journal of Construction Engineering and Management
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    • v.14 no.3
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    • pp.3-11
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    • 2013
  • The changes in construction business have impact on overall operation of construction companies. Poor business of construction companies following a s low industrial cycle could have broader implications and influences on the industry. Since a construction project involves various stakeholders including public organizations, financial institutions and households, a downturn in construction industry might lead to significant economic loss. In this regard, it is meaningful to examine the relationship between changes in construction business cycles and insolvency of construction companies. This study conducts an empirical analysis of the relationship between construction business cycles and how much they affect operation of construction companies. To this end, KMV model was used to estimate probability of bankruptcy, which represents business condition of a construction company. To examine construction business cycles, investment amount for different construction types-residential, non-residential, and construction work-was used as a variable. Based on the investment amount, VECM was applied and the analysis results suggested that construction companies should put priority on diversifying project portfolio. In addition, it was shown that once a construction company becomes unstable in business operation, it is hard to recover even when the market condition turns for the better. This suggests that, to improve business operation of a construction company, internal capacity-building is as important as the market condition and other external circumstances.

Performance of an Efficient Backoff Retransmission Algorithm with a Proactive Jamming Scheme for Realtime transmission in Wireless LAN (재밍 기반의 재전송 방식을 사용한 무선 LAN에서의 효율적인 실시간 트래픽 전송 방안의 성능 분석)

  • Koo Do-Jung;Yoon Chong-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.2B
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    • pp.98-106
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    • 2006
  • In order to provide a realtime transmission over a wireless LAM, we here present a new jamming based retransmission mechanism. In a legacy wireless LAN system, all stations use the binary exponential backoff algorithm to avoid collisions among frames. It is well known that the backoff algorithm causes more collisions as the numbers of active stations increases. This makes transmission of real time traffic hard. In the proposed scheme, when each station senses collisions, it promptly allows to send a jamming signal during a unique jamming window period which is determined by its own channel access count database(CACDB). This jamming windows is chosen not to be overlapped each other by using of CACDB, and thus channel access of another station is prevented. Hereafter the station gets the ownership of the medium when the wireless medium becomes idle after sending the jamming signal and sensing carrier, and then sends frame in medium. In our proposal, repeating collisions is never happened. We here assume that real time traffic use a frame of fixed length in order to make the time for receiving its ACK frame same. Comparing the proposed jamming-based retransmission scheme with the the 802.11 and 802.11e MAC by simulation. one can find that the proposed scheme have advantages in terms of delay, average backoff time, and average number of collisions per frame. One can find that the proposed scheme might be practically applicable to several applications of realtime traffic transmission in wireless LAN systems.

English Vocabulary Learning Application Development Applying Forgetting Curve and Match Result Based Rating System (망각곡선과 대결 기반 순위 결정 시스템을 적용한 영어 단어 학습 어플리케이션 개발)

  • Youm, Kiho;Oh, Kyoungsu;Chun, Youngjae
    • Journal of Korea Game Society
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    • v.15 no.3
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    • pp.151-160
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    • 2015
  • This paper presents English vocabulary memorization system using forgetting curve to automatically adjust the vocabulary difficulty to match learner's level. Our system will decide the appropriate repetition cycle, depending on the number of memorizing words through the forgetting curve, then requires an iterative learning. No matter what learners know or do not know, words are reviewed. To save time by reviewing some words which have the highest probability that learners forget. And it provides vocabulary based on learner level, which makes learner maintain their interest and achievement. A general system provides vocabularies which difficulty matches with evaluated ones, or randomly provides some vocabularies without consideration of users' level. But we apply the "Glicko" system which is being used in the online chess game ranking system to adjust the vocabulary's difficulty. We utilize the system used in the one-by-one player system to our vocabulary-human system. As a result, learners's level and the vocabularies's difficulty is measured in the review process. Moreover it maximizes the performance of English vocabulary memorization by applying feedbacks from practice testing and distributed learning.

Implementation Techniques for the Seafarer's Human Error Assessment Model in a Merchant Ship: Practical Application to a Ship Management Company (상선 선원의 인적과실 평가 모델 구축기법: 선박관리회사 적용 실례)

  • Yim, Jeong-Bin
    • Journal of Navigation and Port Research
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    • v.33 no.3
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    • pp.181-191
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    • 2009
  • In general, seafarer's human error is considered to be the preponderant muse for the majority of maritime transportation accidents in a merchant ship. The implementation techniques for Human Error Model (HEM) to assess possible accident risk by deck officers including captain, chief officer, second mate and third mate are described in this study. The scope of this work is focused to 642 deck officers in the ship management company with 130 vessels. At first, HEM can be constructed through the statistical analysis and expert's brainstorming process with human data to 642 deck officers. Then the variables υ for the human factors, the evaluation level EP(υ) for υ, the weight α of υ, and the title weight β of each deck officers can be decided. In addition, through the analysis of ship's accident history, the accident causation ratios by human error γH and by external error γB can be found as 0.517(51.7%) and 0.483(48.3%), respectively. The correlation coefficients to υ are also shown significant for a 95% confidence interval (p < 0.05) for each coefficient. And the validity of HEM is also surveyed by the analysis of normal probability distribution of risk level RL to each deck officer.

An Efficient Routing Algorithm Considering Packet Collisions in Cognitive Radio Ad-hoc Network (CR Ad-hoc Network에서 패킷 충돌을 고려한 효율적인 경로탐색 알고리즘)

  • Kim, Jin-Su;Choi, Jun-Ho;Shin, Myeong-Jin;Lee, Ji-Seon;Yoo, Sang-Jo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38B no.9
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    • pp.751-764
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    • 2013
  • In cognitive radio ad-hoc networks, common control channel overload and packet collisions are occured due to indiscriminate broadcasting of control packets. So that the path reliability is reduced and control channel is easily saturated. In this paper, we propose a new routing algorithm considering the probability of appearance of primary user and channel status of neighbor nodes. When the source node needs to transmit a data packet to the destination, it performs route discovery process by exchanging control messages using a control channel in ADOV CR Ad-hoc networks. If any intermediate node doesn't have common data channel with previous node to transmit data, it doesn't rebroadcast control packet. And if it has common data channels with previous node, each node determines channel contribution factor with the number of common channels. Based on the channel contribution factor, each node performs different back-off broadcasting. In addition, each node controls control packet flooding by applying to proposed advanced mode using such as number of available channels and channel stability. With the proposed method, the number of control packets to find the data transmission path and the probability of collision among control packets can be decreased. While the path reliability can be increased. Through simulation, we show that our proposed algorithm reduces packet collisions in comparison with the traditional algorithm.

Multiple Cause Model-based Topic Extraction and Semantic Kernel Construction from Text Documents (다중요인모델에 기반한 텍스트 문서에서의 토픽 추출 및 의미 커널 구축)

  • 장정호;장병탁
    • Journal of KIISE:Software and Applications
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    • v.31 no.5
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    • pp.595-604
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    • 2004
  • Automatic analysis of concepts or semantic relations from text documents enables not only an efficient acquisition of relevant information, but also a comparison of documents in the concept level. We present a multiple cause model-based approach to text analysis, where latent topics are automatically extracted from document sets and similarity between documents is measured by semantic kernels constructed from the extracted topics. In our approach, a document is assumed to be generated by various combinations of underlying topics. A topic is defined by a set of words that are related to the same topic or cooccur frequently within a document. In a network representing a multiple-cause model, each topic is identified by a group of words having high connection weights from a latent node. In order to facilitate teaming and inferences in multiple-cause models, some approximation methods are required and we utilize an approximation by Helmholtz machines. In an experiment on TDT-2 data set, we extract sets of meaningful words where each set contains some theme-specific terms. Using semantic kernels constructed from latent topics extracted by multiple cause models, we also achieve significant improvements over the basic vector space model in terms of retrieval effectiveness.

Implementation of Video-Forensic System for Extraction of Violent Scene in Elevator (엘리베이터 내의 폭행 추출을 위한 영상포렌식 시스템 구현)

  • Shin, Kwang-Seong;Shin, Seong-Yoon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.10
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    • pp.2427-2432
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    • 2014
  • Color-X2 is used as a method for scene change detection. It extracts a violent scene in an elevator and then could be used for real-time surveillance of criminal acts. The scene could be also used to secure after-discovered evidences and to prove analysis processes. Video Forensic is defined as a research on various methods to efficiently analyze evidences upon crime-related visual images in the field of digital forensic. The method to use differences of color-histogram detects the difference values of histogram for RGB color from two frames respectively. Our paper uses Color-X2 histogram that is composed of merits of color histogram and ones of X2 histogram, in order to efficiently extract violent scenes in elevator. Also, we use a threshold so as to find out key frame, by use of existing Color-X2 histogram. To increase the probability that discerns whether a real violent scene or not, we take advantage of statistical judgments with 20 sample visual images.

The Development of Fixing Equipment of the Unit Module Using the Probability Distribution of Transporting Load (운반하중의 확률분포를 활용한 유닛모듈 운반용 고정장치 개발)

  • Park, Nam-Cheon;Kim, Seok;Kim, Kyoon-Tai
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.6
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    • pp.4267-4275
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    • 2015
  • Prefabricated houses are fabricated at the factory for approximately 60 to 80% of the entire construction process, and assembled in the field. In the process of transporting and lifting, internal and external finishes of the unit module are concerned about damages. The purpose of this study is to improve the fixing equipment by analyzing load behavior. The improved fixing equipment would minimize the deformation of internal and external finishes. In order to develop the improved fixing equipment, transporting load on the fixing equipment is analyzed using Monte Carlo simulations, and structural performance is verified by the non-linear finite element analysis. Statistical analysis shows load distribution of unit module is similar with extreme value distribution. Based on the statistical analysis and Monte Carlo simulation, the maximum transporting load is 28.9kN and 95% confidence interval of transporting load is -1.22kN to 9.5kN. The nonlinear structural analysis shows improved fixing equipment is not destructed to the limit load of 35.3kN and withstands the load-bearing in the 95% confidence interval of transporting load.

A Quantitative Risk Analysis of LPG Leaked During Cylinder Delivery (가스용기 운반 중 누출된 LPG의 정량적 위험 분석)

  • Kim B-J,;Park Ki-Chang;Lee Kuen-Won
    • Journal of the Korean Institute of Gas
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    • v.7 no.2 s.19
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    • pp.33-41
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    • 2003
  • There exists high hazard when transporting LPG as well as using, storing, and producing. For small scale LPG consumer, retailers deliver LPG to customers via a truck loading many LPG cylinders. Suppose there occurred a accident during LPG cylinder transfer, this could result in serious damages to the life and properties in the near or neighbor of the accident spot. In this regard, we made a quantitative risk analysis to estimate the possible damages and the probability through the identification of accidents causes and the simulation of the possible scenario. In this study, we made the Excel & Visual Basic computer program to perform quantitative LPG accident analysis. The simulation showed the following results. In case of UVCE(Unconfined Vapor Cloud Explosion), the effect within l0m of the accident spot showed very severe structural damages and even the accident can break the window glasses of the area of 150 m apart from accident spot. In case of TNT corresponding probit analysis, after 10 minutes LPG leaking, 75% window glasses of 40 m distance was expected to be broken. And 16% frames of 20m distance, 10% frames of 40m distance was expected to be collapsed.

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