• Title/Summary/Keyword: Reliability function

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Estimation of Fatigue Crack Initiation Life Distribution by Multi-notched Specimen (다응력집중부(多應力集中部)를 가진 판(判)에 의(依)한 피로균열(疲勞龜裂) 발생수명(發生壽命) 분포(分布) 추정(推定))

  • S.W. Kang;D.S. Uom;J.H. Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.4
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    • pp.234-243
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    • 1992
  • Fatigue crack initiation life has a wide scatter and this makes the fatigue design of structural members difficult. In order to make the fatigue life distribution clear, it is required to prepare a large number of specimens and repeat the fatigue tests under the same loading condition. Such fatigue tests usually take much time and cost. In this study, a fatigue testing method using a multi-notched test specimen for the purpose of estimating the distribution function of fatigue crack initiation life by small number of fatigue tests is used. The purpose of this study is to verify the above fatigue testing method of a multi-notched specimen by using Bayesian reliability analysis, Least square method and Skewness method for the determination of unknown Weibull parameters. The multi-notched specimen is a specimen in which several tens of statistically identical notches are prepared.

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The Study on the Effects of Organizational Support and Leader-Member Exchange on Organization Members' Committment and Citizenship (조직적 지원 및 리더-부하관계의 질이 조직전념도와 조직시민행동에 미치는 영향에 관한 연구)

  • Cha, Dae-Kyu;Kim, Woo-Taek;Kim, Tae-Hoon
    • Korean Business Review
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    • v.13
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    • pp.1-30
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    • 2000
  • The corporate make an effort to improve organizational committment and the degree of employees' satisfaction(internal customer satisfaction). And If it's possible, it enhance competitive advantage of organization for external customer satisfaction. But in fact, the external customer satisfaction and competitive power is made by the complex function between leader support and organizational support in organization. Those hypotheses has been supported by the study of many scholars. Nevertheless the reliability in the results is not to be enough for certain conclusion. Therefore this study investigated the influence of organizational support and leader support(as a independent variable) on commitment(as a mediating variable) and citizenship(as a dependent variable). The result indicated that employees who perceive a high degree of organization and leader support show a high committment to organization in affection and positive OCB. Also the result showed that high committment to organization in affection enhance the relation between organizational support, leader's support and OCB(organization citizenship behavior) Implications for managers in organizations are suggested.

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Verifying a Safe P2P Security Protocol in M2M Communication Environment (M2M 통신환경에서 안전한 P2P 보안 프로토콜 검증)

  • Han, Kun-Hee;Bae, Woo-Sik
    • Journal of Digital Convergence
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    • v.13 no.5
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    • pp.213-218
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    • 2015
  • In parallel with evolving information communication technology, M2M(Machine-to-Machine) industry has implemented multi-functional and high-performance systems, and made great strides with IoT(Internet of Things) and IoE(Internet of Everything). Authentication, confidentiality, anonymity, non-repudiation, data reliability, connectionless and traceability are prerequisites for communication security. Yet, the wireless transmission section in M2M communication is exposed to intruders' attacks. Any security issues attributable to M2M wireless communication protocols may lead to serious concerns including system faults, information leakage and privacy challenges. Therefore, mutual authentication and security are key components of protocol design. Recently, secure communication protocols have been regarded as highly important and explored as such. The present paper draws on hash function, random numbers, secret keys and session keys to design a secure communication protocol. Also, this paper tests the proposed protocol with a formal verification tool, Casper/FDR, to demonstrate its security against a range of intruders' attacks. In brief, the proposed protocol meets the security requirements, addressing the challenges without any problems.

An Experimental Study and Value Analysis for Performance Assessment of the Embo-thane Membrane Waterproofing Method (엘보탄도막방수공법의 성능평가를 위한실험적 연구 및 VE분석)

  • Yoon, Cha-Woong;Lee, Seung-Soo;Kim, Sang-Rok;Seo, Jong-Won
    • Korean Journal of Construction Engineering and Management
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    • v.10 no.5
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    • pp.123-134
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    • 2009
  • Since 1970s, urethane waterproofing method is broadly used in rooftops, underground spaces, and sports stadium for its outstanding ultraviolet blockage, watertightness, and elasticity. However, development of slippage-resistance and endurance, improvement of function considering convenience and visually pleasing of users, urethane waterproofing method is necessary, since rooftops and underground spaces have slippage and external force risks. Therefore, many improved waterproofing methods are being developed and, recently, embo-thane waterproofing method, which applies embo-spray coating system, has been developed. This paper explains exposure, nonexposure, and floor-material of embo-thane waterproofing method, and then perform experimental study for comparison with urethane waterproofing method about tensile strength, coefficient of expansion, performance of bond, anti-abrasion, and slippage-resistance. In addition, the performance index was presented for the superiority of embo-thane waterproofing method compared to urethane by setting up evaluation criteria considering not only physical performance but also design side of embo-thane waterproofing method, and Value Analysis applying AHP. Also for an assessment considering uncertain result, Monte Carlo Simulation Method was used to operate reliability analysis through statistic approach method.

A Secure AIS Protocol Suggestion with Analyses of the Standard AIS Protocol (표준 AIS 프로토콜 분석을 통한 보안 AIS 프로토콜 제안)

  • Lee, Jung-Su;Heo, Ouk;Kim, Jae-Hwan;Chung, Sung-Wook
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.9 no.1
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    • pp.49-57
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    • 2016
  • Recently, marine accidents such as the sinking accident Mongol freighter ship and the sinking accident of Sewol ferry in Jindo continuously happen. In order to decrease the number of these marine accidents, Korean ships are obliged to follow the AIS(Automatic Identification System) system. The AIS protocol includes all information for sailing ships. However, the standard AIS protocol does not provide any security function, In addition, it is possible to hijack the standard AIS protocol in case of using a satellite communication device called FUNcuve Dongle Pro+. Therefore, this paper analyzes weak points of the security in the standard AIS protocol. Furthermore, this paper ensures reliability by marking the MAC Address of sender and receiver for secure communication and suggests the protocol that can securely send data, using the VPN Tunnelling method. Therefore, the suggested AIS protocol provides the secure communication to the AIS protocol and protect the messages in the AIS protocol, which can serve safe voyages by decreasing the marine accidents.

HRV Evaluation under Stress Condition by Using Patch Type Bipolar Heart Activity Monitoring System (패치형 바이폴라 심장활동 모니터링 시스템을 이용한 스트레스 상태의 HRV 평가)

  • Yang, Heui-Kyung;Lee, Jeong-Whan;Lee, Young-Jae;Kim, Kyeong-Seop;Lee, Kang-Hwi;Choi, Hee-Jung
    • Science of Emotion and Sensibility
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    • v.12 no.2
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    • pp.161-168
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    • 2009
  • In this study, we have developed the patch type HAMS (Heart Activity Monitoring System) which is non-restricted, non-awarable and non-invasive. The module using wireless telecommunication to receive the ECG (electrocardiogram) signal at the computer has mobility which it easily monitors the heart activity of subjects in no time for long term at any time and places. We developed the small patch type electrode which can be attached on the chest. Also the reliability and moving artifact of ECG signal measured by this electrode have been verified. Using HAMS, we measured the HRV (Heart Rate Variability) parameters, the questionnaire evaluation for anxiety and stress and the amount of stress hormone (cotisol) to evaluate the stress effect in HRV on the same subject. As a result of comparing the values under non stressed and stressed condition, there was significant difference on many parameters. And the parameter highly related with stress on Pearson's Correlation Coefficient has been examined. These show that using HAMS is able to evaluate the function of autonomic nervous system. Therefore, we can predict heart problem in daily life by using HAMS. Also we expect that this module can be applied for more application as health monitoring system.

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Uncertainty Analysis of Wave Forces on Upright Sections of Composite Breakwaters (혼성제 직립벽에 작용하는 파력의 불확실성 해석)

  • Lee, Cheol-Eung
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.23 no.3
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    • pp.258-264
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    • 2011
  • A MCS technique is represented to stochastically analyze the uncertainties of wave forces exerted on the upright sections of composite breakwaters. A stochastical models for horizontal and uplift wave forces can be straightforwardly formulated as a function of the probabilistic characteristics of maximum wave height. Under the assumption of wave forces followed by extreme distribution, the behaviors of relative wave forces to Goda's wave forces are studied by the MCS technique. Double-truncated normal distribution is applied to take the effects of uncertainties of scale and shape parameters of extreme distribution into account properly. Averages and variances of relative wave forces are quantitatively calculated with respect to the exceedance probabilities of maximum design wave height. It is found that the averages of relative wave forces may be decreased consistently with the increases of the exceedance probabilities. In particular, the averages on uplift wave force are evaluated slightly larger than those on horizontal wave force, but the variations of coefficient of the former are adversely smaller than those of the latter. It means that the uncertainties of uplift wave forces are smaller than those of horizontal wave forces in the same condition of the exceedance probabilities. Therefore, the present results could be useful to the reliability based-design method that require the statistical properties about the uncertainties of wave forces.

A Study on the development of Test Report Information Service(TRIS) by User survey analysis (사용자 설문분석을 통한 군수품 시험성적서 정보서비스 고도화 방안에 대한 연구)

  • Park, Dongsoo;Lee, Donghun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.2
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    • pp.405-414
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    • 2017
  • In this study, a survey for a satisfaction evaluation of the Test Report Information Service (TRIS) was conducted. A survey questionnaire on modified Information System Success Model(ISSM) of Delone and Mclean was carried out by 183 users in three groups, such as munition quality assurance agency, munition corporation, and test institute. As a survey result, training on the TRIS was in strong demand in all three groups. An understanding and proficiency of the overall system were different from the work process of each user group. In addition, the munition quality assurance agency needs to enhance the system function with its characteristics. Test institute has necessity of the linkage method with the TRIS depending on the authentication system. User groups are different in the operational method of TRIS between the contractor and cooperation. Accordingly, cooperation needs to be educated continually. This study can help in the construction of a Military Quality Integration Information System to secure the reliability of munitions.

A Study on the Durability Performance of a Receptacle for CNG Vehicles (천연가스 차량용 리셉터클의 내구성능에 관한 연구)

  • Choi, Young;Kim, Young-Min;Lee, Yong-Gyu;Lee, Jang-Hee
    • Journal of the Korean Institute of Gas
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    • v.14 no.6
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    • pp.15-20
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    • 2010
  • Compressed Natural Gas (CNG) buses have been supplied since the year 2000 in order to resolve severe atmospheric pollution in metropolitan area and contributed on the improvement of urban atmospheric environment. However, it is indispensible to take an adequate measure to guarantee the safety of CNG vehicles because of the possibility of huge fire accident. A receptacle, connecting device between high pressure fuel supply tank and fuel line, plays an important role in CNG supply system. In recent, leakage of CNG from receptacles has been reported. So, the concern about the security and reliability of receptacles has been arisen. Therefore, a lot of efforts to prevent leakage are invested among researchers and the durability of this component should be guaranteed despite repeated operation. This research has performed durability tests of a CNG receptacle regarding the repeated usage, extreme chattering, and continuous full flow test. Although a receptacle used for CNG vehicle satisfies validation requirements in the test results, it has been found that failure in the function of leakage prevention in a receptacle could take place in the case of prolonged exposure to high supply pressure in common quick charging environment on site.

Development and Field Application of Apparatus for Determination of Limit State Design Strength Characteristics in Weathered Ground (한계상태설계법 지반정수 산정을 위한 풍화대 강도특성 측정장치의 개발 및 현장적용에 관한 연구)

  • Kim, Ki Seog;Kim, Jong Hoon;Choi, Sung-oong
    • Tunnel and Underground Space
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    • v.30 no.2
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    • pp.164-179
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    • 2020
  • Applying the limit state design method to geotechnical structures, accuracy and reliability of its design are mainly affected by parameters for geotechnical site characteristics, such as unit weight, Poisson's ratio, deformation modulus, cohesion and frictional angle. When the structures are located in weathered ground, especially, cohesion and frictional angle of ground are closely related with decision of parameters for structures' load and ground's resistance. Therefore, the accurate determination of these parameters, which are commonly obtained from field measurement, such as borehole shear test, are essential for optimum design of geotechnical structures. The 38 case studies, in this study, have been analyzed for understanding the importance of these parameters in designing the ground structures. From these results, importance of field measurement was also ascertained. With these evaluations, an apparatus for determining the strength characteristics, which are fundamental in limit state design (LSD) method, have been newly developed. This apparatus has an improved function as following the ASTM suggestion. Through the field application of this apparatus, the strong point of minimizing the possibility of error occurrence during the measurement has been verified and authors summarized that the essential parameters for LSD can be qualitatively obtained by this apparatus for determination of strength characteristics of weathered ground.