• Title/Summary/Keyword: Ranking system

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A Determining Contingency Ranking Using the Weather Effects of the Power System (날씨효과를 고려한 전력계통의 상정사고 순위 결정)

  • 김경영;이승혁;김진오;김태균;전동훈;차승태
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.53 no.9
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    • pp.487-493
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    • 2004
  • The electric power industry throughout the world is undergoing considerable changes from the vertically integrated utility structure to the deregulated market. However, the deregulated electricity market is operated with respect to theory of economical efficiency, and therefore, the system operator requires data with fast contingency ranking for security of the bulk power system. This paper compares the weather dependant probabilistic risk index(PRI) with the system performance index for power flow in the IEEE-RTS. The system performance index for power flow presents the power system stability. This paper presents fast calculation method for determining contingency ranking using the weather dependant probabilistic risk index(PRI). The probabilistic risk index can be classified into the case of normal and adverse weather. This paper proposes calculation method using the probabilistic risk index in determining contingency ranking required for security under the deregulated electricity market.

Comparative Study of Exposure Potential and Toxicity Factors used in Chemical Ranking and Scoring System (화학물질 우선순위선정 시스템에서 고려되는 노출.독성인자 비교연구)

  • An, Youn-Joo;Jeong, Seung-Woo;Kim, Min-Jin;Yang, Chang-Yong
    • Environmental Analysis Health and Toxicology
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    • v.24 no.2
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    • pp.95-105
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    • 2009
  • Chemical Ranking and Scoring (CRS) system is a useful tool to screen priority chemicals of large body of substances. The relative ranking of chemicals based on CRS system has served as a decision-making support tools. Exposure potential and toxicity are significant parameters in CRS system, and there are differences in evaluating those parameters in each CRS system. In this study, the parameters of exposure potential, human toxicity, and ecotoxicity were extensively compared. In addition the scoring methods in each parameter were analyzed. The CRS systems considered in this study include the CHEMS-1 (Chemical Hazard Evaluation for Management Strategies), SCRAM (Scoring and Ranking Assessment Model), EURAM (European Union Risk Ranking Method), ARET (Accelerated Reduction/Elimination of Toxics), and CRS-Korea. An comparative analysis of the several CRS systems is presented based on their assessment parameters and scoring methods.

Analysis of Korean Baduk rating system and dum (한국기원 기사 랭킹과 덤에 관한 분석)

  • Cho, Seonghun;Jang, Woncheol
    • The Korean Journal of Applied Statistics
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    • v.32 no.6
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    • pp.783-794
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    • 2019
  • The current ranking system of the Korean Baduk Association is based on the Elo rating system, which is widely used in the field of chess. Despite the 6.5 point dum (penalty) as compensation for playing as White, many Baduk players still prefer to playing as Black due to Black's higher winning percentage. In this paper, we present the ranking of Baduk players based on the Bradley-Terry model and address the advantage of playing as Black. We compare the ranking from our model with rankings from the Korean Baduk Association.

Chemical Ranking and Scoring Methodology for the Protection of Human Health and Aquatic Ecosystem in Korean Surfacewater: CRAFT (Chemical RAnking of surFacewater polluTants) (인체 및 수생태 보호를 위한 지표수 우선관리대상 항목 선정기법: CRAFT (Chemical RAnking of surFacewater polluTants))

  • Nam, Sun-Hwa;Kwak, Jin Il;Yoon, Sung-Ji;Jeong, Seung-Woo;An, Youn-Joo
    • Journal of Korean Society on Water Environment
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    • v.27 no.6
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    • pp.804-812
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    • 2011
  • To prevent the overflow of various harmful chemicals, it is necessary to modify the chemical management system with an expansion to institutionally regulated substances. This modification should be preceded by selection of the priority chemicals, with a diverse chemical ranking system (CRS) applied to select the chemicals in developed countries. In Korea, a systematic CRS was used in a project related to soil and groundwater, however, it is inadequate to compare soil and groundwater CRS to that of surfacewater. In this study, a priority chemical ranking system for surfacewater was proposed through the analysis of international and domestic CRS cases. This was then applied to 161 chemicals to derive the priority list of harmful chemicals. As a result, Chemical RAnking of surFacewater polluTants (CRAFT) is presented for the protection of human health and the aquatic ecosystem from surfacewater pollutants. The components of CRAFT are the human health toxicity, aquatic ecosystem toxicity and reliability assessment factors. Three lists were derived from the 161 priority harmful chemicals for the protection of human health, aquatic ecosystem or both. It is expected that this result can be useful to prioritize harmful chemicals for the protection of human health and the aquatic ecosystem from Korean surfacewater.

Tag Ranking System based on Semantic Similarity of Tag-pair (태그쌍의 의미유사도 기반 태그 랭킹 시스템)

  • Lee, Si-Hwa;Hwang, Dae-Hoon
    • Journal of Korea Multimedia Society
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    • v.16 no.11
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    • pp.1305-1314
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    • 2013
  • The existing tag based system deducts a retrieval result with low accuracy through the usage of a single tag matching by using tags tagged in contents. And the system doesn't provide effectively contents related information which the tags have, as the users place tags on contents without considering the priority and associative relation between tags. For a solve of above problems, this paper suggests a tag ranking system which extracts semantic similarity between tags and re-ranks the tags tagged in contents. In order to evaluate the performance of suggested system, this paper experiments and compares the ranking result of this paper's tag ranking system with the result of baseline method using tags tagged in images and frequency method adapting tag co-appearance frequency.

PhotoToc: an Implementation of a Ranking System by using User Favor-Based Metrics (포토톡 : 사용자 선호 기반 멀티미디어 콘텐츠 랭킹 시스템의 구현)

  • Lee, Jin-Soo;Park, Al-Eum;Choi, Song-Ah;Ahn, Hoo-Young;Park, Young-Ho
    • Journal of Digital Contents Society
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    • v.8 no.2
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    • pp.113-119
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    • 2007
  • Recently, multimedia applications using internet are increasing by emergency of UCC. The retrieval of photo, video, audio is a main issue to increase utility of access and efficiency of access time. But the exist multimedia applications do not provide the practical ranking system. They provide only simple ranking system using metric. This paper provides "PhotoToc", the user favor-based multimedia ranking system, that can provide differenced view to users. The proposed system has a to retrieve the user centered results.

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Contingency Severity Ranking Using Direct Method in Power Systems (전력계통에 있어서 직접법을 활용한 상정사고 위험순위 결정)

  • Lee, Sang-Keun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.54 no.2
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    • pp.67-72
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    • 2005
  • This paper presents a method to select contingency ranking considering voltage security problems in power systems. Direct method which needs not the detailed knowledge of the post contingency voltage at each bus is used. Based on system operator's experience and knowledge, the membership functions for the MVAR mismatch and allowable voltage violation are justified describing linguistic representation with heuristic rules. Rule base is used for the computation of severity index for each contingency by fuzzy inference. Contingency ranking harmful to the system is formed by the index for security evaluation. Compared with 1P-1Q iteration, this algorithm using direct method and fuzzy inference shows higher computation speed and almost the same accuracy. The proposed method is applied to model system and KEPCO pratical system which consists of 311 buses and 609 lines to show its effectiveness.

A Folksonomy Ranking Framework: A Semantic Graph-based Approach (폭소노미 사이트를 위한 랭킹 프레임워크 설계: 시맨틱 그래프기반 접근)

  • Park, Hyun-Jung;Rho, Sang-Kyu
    • Asia pacific journal of information systems
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    • v.21 no.2
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    • pp.89-116
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    • 2011
  • In collaborative tagging systems such as Delicious.com and Flickr.com, users assign keywords or tags to their uploaded resources, such as bookmarks and pictures, for their future use or sharing purposes. The collection of resources and tags generated by a user is called a personomy, and the collection of all personomies constitutes the folksonomy. The most significant need of the folksonomy users Is to efficiently find useful resources or experts on specific topics. An excellent ranking algorithm would assign higher ranking to more useful resources or experts. What resources are considered useful In a folksonomic system? Does a standard superior to frequency or freshness exist? The resource recommended by more users with mere expertise should be worthy of attention. This ranking paradigm can be implemented through a graph-based ranking algorithm. Two well-known representatives of such a paradigm are Page Rank by Google and HITS(Hypertext Induced Topic Selection) by Kleinberg. Both Page Rank and HITS assign a higher evaluation score to pages linked to more higher-scored pages. HITS differs from PageRank in that it utilizes two kinds of scores: authority and hub scores. The ranking objects of these pages are limited to Web pages, whereas the ranking objects of a folksonomic system are somewhat heterogeneous(i.e., users, resources, and tags). Therefore, uniform application of the voting notion of PageRank and HITS based on the links to a folksonomy would be unreasonable, In a folksonomic system, each link corresponding to a property can have an opposite direction, depending on whether the property is an active or a passive voice. The current research stems from the Idea that a graph-based ranking algorithm could be applied to the folksonomic system using the concept of mutual Interactions between entitles, rather than the voting notion of PageRank or HITS. The concept of mutual interactions, proposed for ranking the Semantic Web resources, enables the calculation of importance scores of various resources unaffected by link directions. The weights of a property representing the mutual interaction between classes are assigned depending on the relative significance of the property to the resource importance of each class. This class-oriented approach is based on the fact that, in the Semantic Web, there are many heterogeneous classes; thus, applying a different appraisal standard for each class is more reasonable. This is similar to the evaluation method of humans, where different items are assigned specific weights, which are then summed up to determine the weighted average. We can check for missing properties more easily with this approach than with other predicate-oriented approaches. A user of a tagging system usually assigns more than one tags to the same resource, and there can be more than one tags with the same subjectivity and objectivity. In the case that many users assign similar tags to the same resource, grading the users differently depending on the assignment order becomes necessary. This idea comes from the studies in psychology wherein expertise involves the ability to select the most relevant information for achieving a goal. An expert should be someone who not only has a large collection of documents annotated with a particular tag, but also tends to add documents of high quality to his/her collections. Such documents are identified by the number, as well as the expertise, of users who have the same documents in their collections. In other words, there is a relationship of mutual reinforcement between the expertise of a user and the quality of a document. In addition, there is a need to rank entities related more closely to a certain entity. Considering the property of social media that ensures the popularity of a topic is temporary, recent data should have more weight than old data. We propose a comprehensive folksonomy ranking framework in which all these considerations are dealt with and that can be easily customized to each folksonomy site for ranking purposes. To examine the validity of our ranking algorithm and show the mechanism of adjusting property, time, and expertise weights, we first use a dataset designed for analyzing the effect of each ranking factor independently. We then show the ranking results of a real folksonomy site, with the ranking factors combined. Because the ground truth of a given dataset is not known when it comes to ranking, we inject simulated data whose ranking results can be predicted into the real dataset and compare the ranking results of our algorithm with that of a previous HITS-based algorithm. Our semantic ranking algorithm based on the concept of mutual interaction seems to be preferable to the HITS-based algorithm as a flexible folksonomy ranking framework. Some concrete points of difference are as follows. First, with the time concept applied to the property weights, our algorithm shows superior performance in lowering the scores of older data and raising the scores of newer data. Second, applying the time concept to the expertise weights, as well as to the property weights, our algorithm controls the conflicting influence of expertise weights and enhances overall consistency of time-valued ranking. The expertise weights of the previous study can act as an obstacle to the time-valued ranking because the number of followers increases as time goes on. Third, many new properties and classes can be included in our framework. The previous HITS-based algorithm, based on the voting notion, loses ground in the situation where the domain consists of more than two classes, or where other important properties, such as "sent through twitter" or "registered as a friend," are added to the domain. Forth, there is a big difference in the calculation time and memory use between the two kinds of algorithms. While the matrix multiplication of two matrices, has to be executed twice for the previous HITS-based algorithm, this is unnecessary with our algorithm. In our ranking framework, various folksonomy ranking policies can be expressed with the ranking factors combined and our approach can work, even if the folksonomy site is not implemented with Semantic Web languages. Above all, the time weight proposed in this paper will be applicable to various domains, including social media, where time value is considered important.

Stability Index Based Voltage Collapse Prediction and Contingency Analysis

  • Subramani, C.;Dash, Subhransu Sekhar;Jagdeeshkumar, M.;Bhaskar, M. Arun
    • Journal of Electrical Engineering and Technology
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    • v.4 no.4
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    • pp.438-442
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    • 2009
  • Voltage instability is a phenomenon that could occur in power systems due to stressed conditions. The result would be an occurrence of voltage collapse leading to total blackout of the system. Therefore, voltage collapse prediction is an important part of power system planning and operation, and can help ensure that voltage collapse due to voltage instability is avoided. Line outages in power systems may also cause voltage collapse, thereby implying the contingency in the system. Contingency problems caused by line outages have been identified as one of the main causes of voltage instability in power systems. This paper presents a new technique for contingency ranking based on voltage stability conditions in power systems. A new line stability index was formulated and used to identify the critical line outages and sensitive lines in the system. Line outage contingency ranking was performed on several loading conditions in order to identify the effect of an increase in loading to critical line outages. Correlation studies on the results obtained from contingency ranking and voltage stability analysis were also conducted, and it was found that line outages in weak lines would cause voltage instability conditions in a system. Subsequently, using the results from the contingency ranking, weak areas in the system can be identified. The proposed contingency ranking technique was tested on the IEEE reliability test system.