• Title, Summary, Keyword: 시스템다이나믹스

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Performance Improvement of Cylindrical Turbine Guide Bearings with Pad Leading-Edge Tapers for Vertical Hydro-Power Application: Effects of Taper Angle and Length (패드 선단 테이퍼를 갖는 수력 수직 원통형 터빈 가이드 베어링의 성능향상 - 테이퍼 각도와 길이의 영향)

  • Lee, An Sung;Jang, Sun-Yong;Park, Soo Man
    • Tribology and Lubricants
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    • v.34 no.1
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    • pp.16-22
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    • 2018
  • Cylindrical turbine guide bearings (TGBs) with simple plain pads have conventionally been used in vertical hydro-power turbine-generator applications in order to provide turbine runner shafts with smooth rotation guides and supports. To overcome low-load/low-eccentricity performance drawbacks, such as very low film stiffness and lack of design credibility in the stiffness values themselves, of conventional cylindrical TGBs, the introduction of a rotational-directional leading-edge taper to each partitioned pad, simply pad leading-edge taper, has been found to be very effective in enhancing their design-application availability and usefulness. In this study, we investigate the effects of taper angle and length for given taper heights in detail in order to systematically establish the effectiveness of design on the performance improvement of vertical hydro-power application cylindrical TGBs with pad leading-edge tapers. The analysis results with $4-Pad{\times}1-Row$ cylindrical TGBs show that the lubrication performance of the cylindrical TGBs is optimized with an approximate taper angle ratio of 0.8 and taper length ratio of 0.9. We conclude that the introduction of pad leading-edge tapers along with the optimization of taper designs can be very effective in improving the overall operation reliability of cylindrical TGBs and the rotordynamic characteristics of vertical hydro-power turbine-generator rotor-bearing systems as well, to which the TGBs are applied.

Abnormal High-Temperature Behavior Troubleshooting of Process Compressor Tilting Pad Journal Bearing (프로세스 압축기 틸팅패드 저널베어링의 비정상 고온거동 트러블슈팅)

  • Lee, An Sung;Lee, Woonsil;Choi, Dong-Hoon
    • Tribology and Lubricants
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    • v.33 no.2
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    • pp.37-44
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    • 2017
  • A DE-side LBP tilting pad journal bearing of a 1-stage overhung heat-pump compressor in a propylene process exhibited abnormal high-temperature behavior. Its temperature had been relatively high at $78^{\circ}C$ from the beginning of operation. In 2014, after three years of operation, it increased suddenly and reached $103^{\circ}C$. Installing a varnish removal equipment and others managed to stabilize the temperature at $95^{\circ}C$. We undertook a troubleshooting approach for reviewing the comprehensive status and integrity of the temperature design of the bearing. We performed lubrication and heat-balance analysis, based on the design engineering data and documents supplied by the OEM. For the base design data of DE-side TPJB, evaluating the effects of key design variables on bearing metal temperature showed that firstly, increasing the bearing clearance and supply oil flow-rate, and next, changing the oil type, and finally, increasing the machined pad clearance and offset, are more effective in reducing the bearing metal temperature. Furthermore, a clarification meeting with the OEM revealed that an incorrect decision had been made to decrease the bearing clearance to eliminate the SSV harshness issue, while not maintaining a sufficient oil flow-rate. We conducted a detailed retrofit design analysis, wherein we increased the oil flow-rate and bearing clearance by decreasing the preload. We predicted that the bearing temperature would decrease to $63^{\circ}C$ from $75.7^{\circ}C$ even at the rerate condition. Finally, after installing and operating a retrofit replacement bearing in 2015, the bearing temperature stabilized at a low temperature of $65^{\circ}C$. Currently (January. 2017), two year later, the bearing metal temperature remains at $65^{\circ}C$. Therefore, we can conclude that the abnormal high-temperature behavior of the bearing has been resolved completely.

Low-Load/Low-Eccentricity Performance Improvement Designs for Hydro Power Application of Cylindrical Turbine Guide Bearings - Introduction of Pad Leading-Edge Tapers (수력 원통형 터빈 가이드 베어링의 저부하/저편심 성능향상 설계 - 패드 선단 테이퍼의 도입)

  • Lee, An Sung;Jang, Sun-Yong
    • Tribology and Lubricants
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    • v.33 no.2
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    • pp.65-70
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    • 2017
  • In vertical hydro/hydraulic power turbine-generator applications, traditionally, cylindrical turbine guide bearings (TGBs) are widely used to provide turbine runner shafts with smooth rotation guides and supports. All existing cylindrical TGBs with simple plain pads have drawbacks such as having no pressure generation and film stiffness at the no-load condition and in addition, at the low-load/low-eccentricity condition, having very low film stiffness values and lacking design credibility in the stiffness values themselves. In this paper, in order to fundamentally improve the low-load/low-eccentricity performance of conventional cylindrical TGBs and thus enhance their design-application availability and usefulness, we propose to introduce a rotation-directional leading-edge taper to each partitioned pad, i.e., a pad leading-edge taper. We perform a design analysis of lubrication performance on $4-Pad{\times}4-Row$ cylindrical TGBs to verify an engineering/technical usefulness of the proposed pad leading-edge taper. Analysis results show that by introducing the leading-edge taper to each pad of the cylindrical TGB one can expect a constant high average direct stiffness with a high degree of design credibility, regardless of load value, even at the low-load/low-eccentricity condition and also control the average direct stiffness value by exploring the taper height as a design parameter. Therefore, we conclude that the proposed pad leading-edge tapers are greatly effective in more accurately predicting and controlling rotordynamic characteristics of vertical hydro-power turbine-generator rotor-bearing systems to which cylindrical TGBs are applied.

Improvement and Expected Effect of Construction Supervision System for Mix-Use Residential Building (주상복합건물의 감리제도 개선방안과 기대효과)

  • Son, Bo-Sik;Bu, Seung-Hyon;Kim, Kyung-Whal;Lee, Hyun-Soo;Ryu, Han-Guk
    • Korean Journal of Construction Engineering and Management
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    • v.7 no.2
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    • pp.62-70
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    • 2006
  • As buildings are changing variously from the side of use, efficiency and size, the construction qualities are more importantly recognized. Supervision system was enacted in the Residential Building Law in 1990 and responsibility supervision system in the Construction Engineering Management Law in 1994, respectively. However, recently revised supervision system in 2003 has some limitations: the present problems of appointing supervisor, disposing the supervisors, supervisor's works. Therefore, the aim of this study is to improve the present supervision system for mix-use residential building. By implementing the proposed revised supervision system, it will be able to expect quality improvement, confidence of the owner and the user, development of construction technology, and increase international competitiveness of supervision company.

A Study on Forecasting Model of the Apartment Price Behavior in Seoul (서울시 아파트 가격 행태 예측 모델에 관한 연구)

  • Kwon, Hee-Chul;Yoo, Jung-Sang
    • Journal of Digital Convergence
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    • v.11 no.2
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    • pp.175-182
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    • 2013
  • In this paper, the simulation model of house price is presented on the basis of pricing mechanism between the demand and the supply of apartments in seoul. The algorithm of house price simulation model for calculating the rate of price over time includes feedback control theory. The feedback control theory consists of stock variable, flow variable, auxiliary variable and constant variable. We suggest that the future price of apartment is simulated using mutual interaction variables which are demand, supply, price and parameters among them. In this paper we considers three items which include the behavior of apartment price index, the size of demand and supply, and the forecasting of the apartment price in the future economic scenarios. The proposed price simulation model could be used in public needs for developing a house price regulation policy using financial and non-financial aids. And the quantitative simulation model is to be applied in practice with more specific real data and Powersim Software modeling tool.

Investigation of Topic Trends in Computer and Information Science by Text Mining Techniques: From the Perspective of Conferences in DBLP (텍스트 마이닝 기법을 이용한 컴퓨터공학 및 정보학 분야 연구동향 조사: DBLP의 학술회의 데이터를 중심으로)

  • Kim, Su Yeon;Song, Sung Jeon;Song, Min
    • Journal of the Korean Society for information Management
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    • v.32 no.1
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    • pp.135-152
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    • 2015
  • The goal of this paper is to explore the field of Computer and Information Science with the aid of text mining techniques by mining Computer and Information Science related conference data available in DBLP (Digital Bibliography & Library Project). Although studies based on bibliometric analysis are most prevalent in investigating dynamics of a research field, we attempt to understand dynamics of the field by utilizing Latent Dirichlet Allocation (LDA)-based multinomial topic modeling. For this study, we collect 236,170 documents from 353 conferences related to Computer and Information Science in DBLP. We aim to include conferences in the field of Computer and Information Science as broad as possible. We analyze topic modeling results along with datasets collected over the period of 2000 to 2011 including top authors per topic and top conferences per topic. We identify the following four different patterns in topic trends in the field of computer and information science during this period: growing (network related topics), shrinking (AI and data mining related topics), continuing (web, text mining information retrieval and database related topics), and fluctuating pattern (HCI, information system and multimedia system related topics).

An Optimizing Simulation for Designing the Numbers of Electric Train Car (전동열차 편성량수 설계를 위한 최적화 시뮬레이션)

  • Kim, Ick-Hee;Yun, Dong-Hee;Kum, Ki-Jung;Lee, Sang-Myoung
    • Journal of Korean Society of Transportation
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    • v.30 no.3
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    • pp.95-106
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    • 2012
  • The railway service in the Seoul metropolitan area is facing variety of l changes such as extension of service coverage, new construction, and introduction of express service which in turn causes changes on demands. The demand affects train operation characteristics (frequency of service, train formation) as well as on the congestion rate which is one of the major evaluation index in metropolitan area user service. For the efficient operation of the train, the relationship among the minimization of fleet number, operating cost, and service level has been analyzed. Using the Powersim, which is a system dynamics (System Dynamics) simulation program for realizing optimized simulation for train-formation, this paper identified that some stations of Gyeong-bu line exceeded limit congestion rate(150%) of a fleet already that means it is best to maintain current condition of the line; however, the Gyeong-in line and the Gwa-chon line showed no excess of the limit congestion rate so that it is possible to reduce 2-4 fleets of train for efficient operation. In addition, in case of Jang-hang line between Cheon-an and Sin-chang, a train consisting of 10 fleets provides services which is same formation of train for Gyeong-bu line. This study proved that the congestion rate will not rise greatly with only 4 fleets of a train for the service in Jang-hang line, and it is considered that a study for shuttle service between Cheon-an and Sin-chang is necessary.

An Exploratory Study on the Sharing and Application of Public Open Big Data (공공 빅데이터 개방 및 활용 활성화 방안에 대한 연구)

  • Jeon, Byeong-Jin;Kim, Hee-Woong
    • Informatization Policy
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    • v.24 no.3
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    • pp.27-41
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    • 2017
  • With the growing interest in the 4th industrial revolution and big data, various policies are being developed for facilitating the use of public open big data, which are leading to a wide range of added values created from use of such data. Despite the expanded requirements for public data disclosure and the legal system improvement, however, the use of public open big data is still limited. According to the literature review, there are studies on policy proposals for the government guiding directions for public open big data, but there is a lack of studies that handle the issue from the users' viewpoint. Therefore, this study aims to analyze the public open data ecosystem in Korea and to analyze public open big data through interviews with the providers (the government and public institutions) and users (private sector companies and citizens). This way, the study finds inhibition factors and facilitation factors, draws out issues and suggests solutions through a causal relationship analysis between each factor. Being a research on finding measures for facilitating both public big data release and use, this study has theoretical implications. In the meanwhile, the derived issues and alternatives provide practical implications also for stakeholders who are planning to facilitate release and use of public open big data.

A Study on the Promotion of Mobile Easy Payment Services in the Fintech Era (핀테크 모바일 간편결제 서비스 활성화 방안)

  • Cho, Eun-Young;Kim, Hee-Woong
    • Informatization Policy
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    • v.22 no.4
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    • pp.22-44
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    • 2015
  • With the growing interest being reflected in the FinTech industry, much attention has been paid to mobile easy payment services as well. In the era of mobile commerce, the core advantage of using mobile easy payment services(simplifying complex payment procedures and thus facilitating user convenience and reducing the chance of giving up payment) are being more emphasized. Mobile easy payment service market not only includes mobile easy payment service providers but also users, non-users, affiliates, banks, and credit card companies as main stakeholders. Exploring those stakeholders is thus important to thoroughly understand such market. However, extant literature on mobile easy payment services mostly focuses on examining adoption intention of users or non-users. This study, an exploratory research based on interviews, thus aims to extract driving as well as inhibiting factors of mobile easy payment service use from six different perspectives (i.e., social platform, bank, credit card company, affiliate, user, and non-user) and analyze a sequence of cause and effect for each factor. For this, the causal loop diagram was developed to deduce key issues and propose an alternative. Theoretical and practical implications of this study will also be discussed.

Autopoiesis, Affordance, and Mimesis: Layout for Explication of Complexity of Cognitive Interaction between Environment and Human (오토포이에시스, 어포던스, 미메시스: 환경과 인간의 인지적 상호작용의 복잡성 해명을 위한 밑그림)

  • Shim, Kwang Hyun
    • Korean Journal of Cognitive Science
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    • v.25 no.4
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    • pp.343-384
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    • 2014
  • In order to unravel the problems of the mind, today's cognitive science has expanded its perspective from the narrow framework of the past computer model or neuronal network model to the wider frameworks of interaction with the brain in interaction with the body in interaction with their environments. The theories of 'the extended mind', 'embodied mind', or 'enactive mind' appeared through such processes are working on a way to move into the environments while the problem to unravel the complex process of interactions between the mind, the body and the environments are left alone. This problem can be traced back as far as to Gibson and Maturana & Varela who tried at first to unravel the problem of the mind in terms of interaction between the brain, the body and there environments in 1960~70s. It's because Gibson stressed the importance of the 'affordance' provided by the environment while Maturana & Varela emphasized the 'autonomy' of auto-poiesis of life. However, it will be proper to say that there are invariants in the affordances provided by the environment as well as the autonomy of life in the state of structural coupling of the environment's variants and life's openness toward the environment. In this case, the confrontational points between Gibson and Maturana & Varela will be resolved. In this article, I propose Benjamin's theory of mimesis as a mediator of both theories. Because Benjamin's concept of mimesis has the process of making a constellation of the embodiment of the affordance and the enaction of new affordance into the environment at the same time, Gibson's concept of the affordance and Maturana & Varela's concept of embodiment and enaction will be so smoothly interconnected to circulate through the medium of Benjamin's concept of mimesis.