• Title/Summary/Keyword: Safe Factor

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Estimation of Power Collector Wear Considering the Operating Environment of a Maglev (자기부상열차의 주행 환경을 고려한 집전자 마모도 평가)

  • Lee, Kyoung-bok;Ma, Sang-kyeon;Lim, Jae-won;Park, Do-young;Son, Jeong-ryong;Kang, Hyun-il
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.1
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    • pp.38-42
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    • 2017
  • The wear of the third track power collector is one of the essential check factors for safe train operation. Rapid wear of the current collector accelerates the line of the catenary. In addition, the arc generated when the catenary line is turned off causes a malfunction in the minute portion of the catenary line, thereby shortening the life of the catenary line. In this paper, to analyze the mechanical wear of the current collector during driving according to the environmental factor of the Maglev(magnetic levitation train), it was divided into dry season and wet season. the wear of metallized collector, copper alloy collector and carbon collector were measured and compared with each other. The wear rate was measured according to the position of the wire, the position of the power collector and the position per hour. Microscopic photographs of the cross section and surface of the power collector were measured. The electrical currents of the metallized collector, copper alloy collector and carbon collector were measured.

A Study on the P.S.M. system for the Construction Safety (건설안전을 위한 P.S.M. 기법에 관한 연구)

  • Lee, Song;Son, Gi-Sang;Choi, Won-Il;Oh, Tae-Sang;Chae, Jum-Sik
    • Journal of the Korean Society of Safety
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    • v.15 no.4
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    • pp.101-111
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    • 2000
  • In order to introduce P.S.M. system adequate to domestic construction first, many cases similar to advanced foreign P.S.M. system have been collected and compared to the domestic situation. Then, the current safety management status of bridges, subways, apartment and office building construction are investigated while visiting interview, using questionnaire at site have being done. The potential hazard and measurement have been investigated for each kind of works, and the domestic introducing method of P.S.M. system is analyzed with expert discussion. In order to represent how to make out P.S.M. plan, the questionnaire is made out using each five place for bridge, subways, apartment and office building. As the weight factor for potential hazard of each work obtained from more than forty site places, is produced and shown. Also, a direction the recommendation is suggested to improve tool in each construction site with work schedule. It is thought that proposed schedule contributed to keeping in safe business administration of each company in decreasing many effort at the construction site.

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Feasibility study of an earth-retaining structure using in-situ soil with dual sheet piles

  • An, Joon-Sang;Yoon, Yeo-Won;Song, Ki-Il
    • Geomechanics and Engineering
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    • v.16 no.3
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    • pp.321-329
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    • 2018
  • Classic braced walls use struts and wales to minimize ground movements induced by deep excavation. However, the installation of struts and wales is a time-consuming process and confines the work space. To secure a work space around the retaining structure, an anchoring system works in conjunction with a braced wall. However, anchoring cannot perform well when the shear strength of soil is low. In such a case, innovative retaining systems are required in excavation. This study proposes an innovative earth-retaining wall that uses in situ soil confined in dual sheet piles as a structural component. A numerical study was conducted to evaluate the stability of the proposed structure in cohesionless dry soil and establish a design chart. The displacement and factor of safety of the structural member were monitored and evaluated. According to the results, an increase in the clearance distance increases the depth of safe excavation. For a conservative design to secure the stability of the earth-retaining structure in cohesionless dry soil, the clearance distance should exceed 2 m, and the embedded depth should exceed 40% of the wall height. The results suggest that the proposed method can be used for 14 m of excavation without any internal support structure. The design chart can be used for the preliminary design of an earth-retaining structure using in situ soil with dual steel sheet piles in cohesionless dry soil.

Paradigm Shift in Intra-Arterial Mechanical Thrombectomy for Acute Ischemic Stroke : A Review of Randomized Controlled Trials after 2015

  • Sheen, Jae Jon;Kim, Young Woo
    • Journal of Korean Neurosurgical Society
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    • v.63 no.4
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    • pp.427-432
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    • 2020
  • Three randomized control trials (RCTs), published in 2013, investigated efficacy of mechanical thrombectomy in large vessel occlusions and did not show better results compared to intravenous (IV) recombinant tissue-type plasminogen activator (tPA) alone. However, most clinicians treating stroke consider mechanical thrombectomy as the standard treatment rather than using IV tPA alone. This paradigm shift was based on five RCTs investigating efficacy of mechanical thrombectomy in acute ischemic stroke conducted from 2010 to 2015. They demonstrated that mechanical thrombectomy was effective and safe in acute ischemic stroke with anterior circulation occlusion when performed within 6 hours of stroke onset. There are four reasons underlying the different results observed between the trials conducted in 2013 and 2015. First, the three RCTs of 2013 used low-efficiency thrombectomy devices. Second, the three RCTs used insufficient image selection criteria. Third, following the initial presentation at the hospital, reperfusion treatment required a long time. Fourth, the three RCTs showed a low rate of successful recanalization. Time is the most important factor in the treatment of acute ischemic stroke. However, current trends utilize advanced imaging techniques, such as diffusion-weighted imaging and multi-channel computer tomographic perfusion, to facilitate the detection of core infarction, penumbra, and collateral flows. These efforts demonstrate that patient selection may overcome the barriers of time in specific cases.

Fatigue Evaluation of Steam Separators of Heat Recovery Steam Generators According to the ASME Boiler and Pressure Vessel Code (ASME Boiler & Pressure Vessel Code에 따른 배열회수보일러 기수분리기의 피로 평가)

  • Lee, Boo-Youn
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.17 no.4
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    • pp.150-159
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    • 2018
  • The present research deals with a finite element analysis and fatigue evaluation of a steam separator of a high-pressure evaporator for the Heat Recovery Steam Generator (HRSG). The fatigue during the expected life of the HRSG was evaluated according to the ASME Boiler and Pressure Vessel Code Section VIII Division 2 (ASME Code). First, based on the eight transient operating conditions prescribed for the HRSG, temperature distribution of the steam separator was analyzed by a transient thermal analysis. Results of the thermal analysis were used as a thermal load for the structural analysis and used to determine the mean cycle temperature. Next, a structural analysis for the transient conditions was carried out with the thermal load, steam pressure, and nozzle load. The maximum stress location was found to be the riser nozzle bore, and hence fatigue was evaluated at that location, as per ASME Code. As a result, the cumulative usage factor was calculated as 0.00072 (much less than 1). In conclusion, the steam separator was found to be safe from fatigue failure during the expected life.

Roles of Safety Management System (SMS) in Aircraft Development

  • Lee, Won Kwan;Kim, Seung Jo
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.3
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    • pp.451-462
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    • 2015
  • Safety is the first priority in civil aviation, and so the International Civil Aviation Organization (ICAO) has introduced and mandated the use of Safety Management Systems (SMS) by airlines, airports, air traffic services, aircraft maintenance organizations, and training organizations. The aircraft manufacturing industry is the last for which ICAO has mandated the implementation of SMS. Since SMS is a somewhat newer approach for most manufacturers in the aviation industry, they hardly believe in the value of implementing SMS. The management of safety risk characteristics that occur during early aircraft development stages and the systematic linkage that the safety risk has to do with an aircraft in service could have a significant influence on the safe operation and life cycle of the aircraft. This paper conducts a case analysis of the McDonnell Douglas MD-11 accident/incident to identify the root causes and safety risk levels, and also verified why aircraft manufacturing industry should begin to adopt SMS in order to prevent aircraft accident.

Study on Multibody Dynamic Analysis and Durability of Heavy Load Bucket Roller Chain System (고하중용 버킷 롤러체인 시스템의 다물체 동역학 해석 및 내구성 연구)

  • Kim, Chang Uk;Park, Jin Chul;Lee, Dong Woo;Song, Jung Il
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.11
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    • pp.919-925
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    • 2016
  • In this study, multibody dynamic and mechanical analyses were conducted for the structure of roller chain bucket elevator system. The fatigue life of the roller chain elevator system was determined under static and fatigue loadings. Results of multibody dynamic analysis suggested that the maximum contact force occurred at the drive sprocket engagement point with the roller chain due to maximum tension. Fatigue analysis results suggest that the high load roller chain system is durable and safe because its life time is more than 700,000 cycles, close to its designed value (1,000,000 cycle). However, the contact portion of plate and pin needed a safety factor. The dynamic analysis of the heavy load roller chain was conducted with a multibody dynamic analysis program. The results obtained in this study can be utilized for dynamic analysis of roller chain systems in all industries.

Perception and Purchase Behavior on Environment-friendly Agricultural Products of College Students in Daejeon (대전지역 대학생의 친환경농산물 인식 및 구매행동)

  • Cho, Yu-Jin;Koo, Nan-Sook
    • Korean journal of food and cookery science
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    • v.31 no.3
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    • pp.328-334
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    • 2015
  • The survey was conducted to investigate the perception and purchase behaviors regarding environment-friendly agricultural products (EFAP). 353 questionnaires were collected from college students in Daejeon and analyzed using SPSS 21.0. The students recognized EFAP as foods containing less or no agricultural pesticides and chemical fertilizers. More food major students knew the definition of EFAP compared to non-food major students (p<0.05). The students discriminated EFAP based on certificat on label and obtained information about EFAP from TV/home shopping. More non-food major students purchased EFAP than food major students (p<0.001). The main reason for hesitation with EFAP purchases was the high price. However, students purchased EFAP because of their family's safety. Price reduction is the most important factor to promote the consumption of EFAP. Proper education programs are required so that college students can easily purchase EFAP to promote safe and healthy dietary habits.

A Study for the Best Estimation of Geotechnical Parameters on the Slope Analysis (사면해석에 있어서 지반변수의 최적추정에 관한 연구)

  • Kim, Du-Jun;Jeong, Dae-Suk;Baek, Yeong-Sik
    • Proceedings of the Korean Geotechical Society Conference
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    • 1993.06b
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    • pp.19-44
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    • 1993
  • The purpose of this paper is to study the design and the construction for the most economic and safe slope stability analysis. The approach to the purpose Iies in analyzing the characteristic on direction and distance by the sample value for the geotechnical parameters using the semi-variogram concept. Based on the result, we derive the Kriging system equation from the stochastical concept and solve the equation to find the weighting factor which is applied both the point estimation and the block estimation in the particular position. Comparing and analyzing the various methods. we find the best reliability, which is more accurate than any other.

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The characteristics of polymer electrolyte for lithium polymer battery

  • Park Soo-Gil;Park Jong-Eun;Lee Ju-Seong
    • Journal of the Korean Electrochemical Society
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    • v.2 no.1
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    • pp.1-4
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    • 1999
  • A lithium ion battery with polymer electrolyte is expected as a safe and long cycle life battery. This paper reports primarily the recent development results of a solid polymer electrolyte, which is a key factor of the secondary battery system, that has been obtained during the process of the development of a polymer type lithium battery. As a successful result of the solid polymer electrolyte. The ionic conductivity of the solid polymer electrolyte, which is composed of polyacrylonitrile and $LiClO_4\;with\; Al_2O_3$ dissolved as the supporting electrolyte, has been confirmed to be $2.3\times10^{-4} S/cm$ at room temperature.