• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.6
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• pp.616-625
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• 2011

Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.

• Journal of Applied Reliability
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• v.5 no.4
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• pp.487-500
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• 2005

MEMS devices usually have micro actuators contained in a cavity, If the pressure level of testing chamber is higher than that of cavity, moisture will ingress into the cavity, which may cause critical failure such as stiction of the moving parts. To design an accelerated life test based on high temperature and high humidity, such a phenomena should be considered. In this study, a throughput model that can estimate the amount of moisture ingress is used to decide the testing time and conditions of a high temperature and high humidify test.

• Journal of Korean Society for Quality Management
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• v.24 no.2
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• pp.77-86
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• 1996

In this paper, we consider the problem of testing independence in the absolutely continuous bivariate exponential distribution of Block and Basu(1974). We construct a bootstrap procedure for testing zero and non-zero values of the parameter ${\lambda}_3$ which measures the degree of dependence and compare the power of the bootstrap test with likelihood ratio test(LRT) by Gupta et al.(1984) and the test based on maximum likelihood estimator(MLE) $\hat{{\lambda}}_3$ by Hanagal and Kale(1991) for small and moderate sample sizes.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1681-1684
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• 2004

90 년대 후반부터 웹 기반 수업(Web-based instruction)이라 하여 인터넷을 이용한 새로운 교육방법이 시도되었다. WBI에 필요한 각종 프로그래밍을 수작업으로 진행하여야 한다는 문제점을 극복하기 위해 개발된 학습운영체제(Learning Management System)가 개발되면서 인터넷을 통한 교육은 급속히 확산되고 있다. 무선 인터넷 기술까지 수용하는 개념인 소위 e-Learning 체제로 발전되면서 e-Learning의 수요는 급속히 증가하게 되었다. e-Learning 기술 표준 개발을 실질적으로 주도하는 기관들인 IEEE, AICC, IMS가 제안하는 개별 표준안들을 ADL에서 SCORM(Sharable Content Object Reference Model)이라는 종합적인 표준안으로 수렴하게 되면서 SCORM을 기준으로 만든 다양한 컨텐츠가 개발되고있다.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.8
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• pp.3879-3887
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• 2012

Background: Development of effective educational strategies should accompany increases in public awareness and the availability of genetic testing for breast cancer (BC). These educational strategies should be designed to fulfill the knowledge gap while considering factors that influence women's interest in order to facilitate decision making. Objective: To determine the possible correlates of Saudi women's interest in BC genes testing including socio-demographics, the level of awareness towards BC genes, the family history of BC and the perceived personal risk among adult Saudi women in Al Hassa, Saudi Arabia. Subjects and methods: This cross-sectional study was carried out during the second BC community-based campaign in Al Hassa, Saudi Arabia. All Saudi women aged ${\geq}18$ years (n=781) attending the educational components of the campaign were invited to a personal interview. Data collection included gathering information about sociodemographics, family history of BC, the perceived personal risk for BC, awareness and attitude towards BC genes and the women's interest in BC genes testing. Results: Of the included women (n=599), 19.5% perceived higher risk for BC development, significantly more among < 40 years of age, and with positive family history of BC before 50 years of age. The participants demonstrated a poor level of awareness regarding the inheritance, risk, and availability of BC genetic testing. The median summated knowledge score was 1.0 (out of 7 points) with a knowledge deficit of 87.8%. The level of knowledge showed significant decline with age (> 40 years). Of the included women 54.7% expressed an interest in BC genetic testing for assessing their BC risk. Multivariate regression model showed that being middle aged (Odds Ratio 'OR'=1.88, confidence intervals 'C.I'=1.14-3.11), with higher knowledge level (OR=1.67, C.I=1.08-2.57) and perceiving higher risk for BC (OR=2.11, C.I=1.61-2.76) were the significant positive correlates for Saudi women interest in BC genetic testing. Conclusion: Saudi women express high interest in genetic testing for BC risk despite their poor awareness. This great interest may reflect the presence of inappropriate information regarding BC genetic testing and its role in risk analysis.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.1
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• pp.6-12
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• 2006

A popular method used by primary protection for power transformer is current ratio differential relaying (RDR) with 2nd harmonic restraints. In modern power transformer due to the use of low-loss amorphous material, the 2nd harmonic component during inrush is significantly reduced. The higher the capacitance of the high voltage status and underground distribution, the more the differential current includes the 2nd harmonic component during internal fault. Thus the conventional method may not operate properly. This paper proposes an advanced relaying algorithm and the prototype IED hardware design and it's real-time experimental results. To evaluate performance of the proposed algorithm, the study is well constructed power system model including power transformer utilizing the EMTP software and the testing is made through simulation of various cases. The proposed relaying that is well constructed using DSP chip and microprocessor etc. has been developed and the prototype IED has been verified through on-line testing. The results show that an advanced relaying based prototype IED never mis-operated and correctly identified all the faults and that inrushes that are applied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.623-629
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.173-183
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• 1996

In this paper, a new structure that can do fault detection and location of digial logic circuits more efficiently using current testing techniques is proposed. In the conventional method, observation point for steady state power supply current was only one, but in the proposed method more fault classes are divided for fault detection and location through the ovservation of steady state power supply current at two points. Also, it is shown that this structure can be easily applied in detection of stuck-open fault which is not easy to do testing with conventional current testing techniques. In the presented mehtod, an extra trasnistor is used, and current path is made compulsorily in the CMOS circuits in which no current path can be established in steady state, then it can be known that stuck-open tault is in the MOS transistor on the considering current path, if this path disappears due to stuck-open fault. The validity and the effectiveness is shwon, thorugh the SPICE simulation of circuits with fault and the current path search experiment using current path search program based on transistor short model wirtten in C language on SUN sparc workstation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.290-296
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• 2005

This paper proposes the modeling scheme of the Miniature Universal Testing Machine (MUTM) composed of 36 thin-beam-type bimorph PZTs and the control algorithm to minimize the residual vibration of the MUTM in the dynamic testing of specimens. In the operation of the MUTM, hysteresis, residual displacement and vibration of it are major issues. From the analysis of the MUTM behaviors, the hysteresis is described by the curving fitting scheme with the function of an input voltage. The dynamic characteristics of the MUTM are identified by the frequency domain modeling technique based on the experimental data. The interested bandwidth is focused on 125-315HZ for effective modeling and control. For the robust vibration control of the MUTM, the sliding mode control and the Kalman filter as observer are proposed. The paper also proposes the best input signal type to operate the MUTM effectively. The feasibility of the proposed modeling scheme and control algorithm are tested and verified experimentally.

• Transactions of Materials Processing
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• v.33 no.5
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• pp.309-314
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• 2024

Supersonic aircraft and missiles often encounter damage issues due to high-speed collisions with small objects such as ice particles and water droplets. This can significantly impact the safety and performance of these vehicles, making the assessment and development of collision testing crucial. Existing collision testing methods have relied on equipment such as gas guns, which utilize high pressure. However, most accelerators for projectiles are large-scale devices designed for weaponry and high-pressure gases, rendering them inaccessible and unsuitable for laboratory use. Therefore, there is a need for research into easily accessible and economically efficient testing devices at the laboratory level. An impact tester can launch a projectile with a velocity of 100 m/s using low-pressure compressed air at approximately 10 bar. The velocity of the impact tester projectile is determined by the pressure within the chamber, friction, and the length of the barrel. In this study, computational fluid dynamics was utilized to define friction coefficients that match experimental results based on projectile weight, enabling accurate prediction of velocity. The resulting data provides practical and effective insights for the design of impact testers, utilizing the defined friction coefficients to understand and predict complex physical phenomena.