• Journal of the Computational Structural Engineering Institute of Korea
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• 제26권6호
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• pp.447-454
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• 2013

A model-based method is proposed to diagnose the gear crack in the gearbox under variable loading condition with the objective to apply it to the wind turbine CMS(Condition Monitoring System). A simple test bed is installed to illustrate the approach, which consists of motors and a pair of spur gears. A crack is imbedded at the tooth root of a gear. Tachometer-based order analysis, being independent on the shaft speed, is employed as a signal processing technique to identify the crack through the impulsive change and the kurtosis. Lumped parameter dynamic model is used to simulate the operation of the test bed. In the model, the parameter related with the crack is inversely estimated by minimizing the difference between the simulated and measured features. In order to illustrate the validation of the method, a simulated signal with a specified parameter is virtually generated from the model, assuming it as the measured signal. Then the parameter is inversely estimated based on the proposed method. The result agrees with the previously specified parameter value, which verifies that the algorithm works successfully. Application to the real crack in the test bed will be addressed in the next study.

• Ecology and Resilient Infrastructure
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• 제7권3호
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• pp.181-188
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• 2020

In this study, a temperature distribution sensing method using optical fiber was applied to a large-scale levee experiment, and the applicability of wide-area levee or embankment monitoring technology to observe the changes inside the levee was reviewed. The optical fiber was buried in a large-scale levee, and the temporal and spatial temperature changes were measured according to the water level changes in the reservoir. As the water level of the reservoir increased, the temperature of the embankment slope decreased, and as the infiltration progressed, a change in the spatial location of the temperature change was detected. The temperature change due to embankment infiltration varied depending on the time of the infiltration progress, and the change assumed to be the seepage line could be observed. This study has demonstrated that information about temperature changes inside the levee can be interpreted as the information on the locations that are judged to be relatively vulnerable, investigating the changes in the condition inside the levee.

• Korean Security Journal
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• 제11호
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• pp.37-60
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• 2006

The area of security service has been maintaining the high growth curve annually by improving security consciousness from increase of the income and the progress of public services's level by the accomplishment in the info-communication field, recently the demand for unmanned security system is extended form commercial purposes into public offices and individual's houses. In addition to, the possible distance of offering services is scheduled to magnify. At the period when security company's influence has been becoming significant, the injustice transaction is the serious factor which obstructs the development of security companies. Therefore, it is urgent thing to devise counterplans to extirpate injustice transactions. There are the legalistic approaches of the breakthroughs against injustice transactions. One thing is settling the standard of the judgment and the other is renovating the provision of injustice transactions. Utilizing the principles of the fair competitions and importing self-obedience programs within the range of trade actions which is permitted by law, acted as the system approach. Moreover, there are such three things which can achieve mutual balances as establishing the range of the permitted action toward business corporations, applying spontaneously the fair competition principles and introducing the system of standard agreements. Gong further, this can establish order of security service areas and control them. Besides, it is possible for every organizations to make and operate the system appropriately by importing the self-observance system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• 제40권1호
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• pp.24-36
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• 2003

The digital mobile communication will be developed till getting multimedia service in anyone, any where, any time. Theses requiring items are going to be come true via IMT-2000 system. Transmitting signal bandwidth of IMT-2000 system is 3 times as large as IS-95 system. That is mean peak to average of signal is higher than IS-95A system. So we have to design it carefully not to effect in adjacent channel. HPA(High Power Amplifier) located in the end point of system is operated in 1-㏈ compression point(Pl㏈), then it generates 3rd and 5th inter modulation signals. Theses signals affect at adjacent channel and RF signal is distorted by compressed signal which is operated near by Pl㏈ point. Then the most important design factor is how we make HPA having high linearity. Feedback, Pre-distorter and Feed-forward methods are presented to solve theses problems. Feed-forward of these methods is having excellent improving capacity, but composed with complex structure. Generally, Linearity and Efficiency in power amplifier operate in the contrary, then it is difficult for us to find optimal operating point. In this paper we applied algorithm which searches optimal point of linear characteristics, which is key in Power Amplifier, using minimum current point of error amplifier in 1st loop. And we made 2nd loop compose with new structure. We confirmed fabricated LPA is operated by having high linearity and minimum current condition with ACPR of -26 ㏈m max. @ 30㎑ BW in 3.515㎒ and ACLR of 48 ㏈c max@${\pm}$㎒ from 1W to 40W.

• Journal of the Institute of Electronics and Information Engineers
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• 제52권12호
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• pp.55-63
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• 2015

Recently, terroristic threats using a radio controlled improvised explosive device (RCIED) that is remotely controlled and exploded have been increased around the world. In order to prevent the explosion of an RCIED, jamming techniques that interrupt an RCIED receiver can be used, so that the receiver can not demodulate the trigger code. Conventional jamming technique is a type of active barrage jamming that always emits the noise jamming signal for all the frequency band. However, it needs large power consumption and thus is limited in operation time for a vehicle. In order to overcome the shortage of the active barrage jamming, reactive jamming technique has drawn attention. In reactive jamming, all the frequency band is firstly scanned, and then if any trigger signal exists, one emits the jamming signal to the corresponding frequency band. Therefore, the reactive jamming is superior to the active barrage jamming in terms of power efficiency. However, a reactive jammer emits a jamming signal only after the trigger signal is intercepted, which means that the jamming signal may be late for interrupting an RCIED receiver. In this sense, it is needed to evaluate a delay in an RCIED receiver. To achieve this, we analyze the reaction time and present the simulation result for jamming performance of reactive jamming against an RCIED using mobile devices.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제45권10호
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• pp.7-14
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• 2008

In this paper, we designed the HVIC(High Voltage Gate Driver IC) which has improved noise immunity characteristics and high driving capability. Operating frequency and input voltage range of the designed HVIC is up to 500kHz and 650V, respectively. Noise protection and schmitt trigger circuit is included in the high-side level shifter of designed IC which has very high dv/dt noise immunity characteristic(up to 50V/ns). And also, rower dissipation of high-side level shifter with designed short-pulse generation circuit decreased more that 40% compare with conventional circuit. In addition, designed HVIC includes protection and UVLO circuit to prevent cross-conduction of power switch and sense power supply voltage of driving section, respectively. Protection and UVLO circuit can improve the stability of the designed HVIC. Spectre and Pspice circuit simulator were used to verify the operating characteristics of the designed HVIC.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.443-443
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• 2014

CIS 박막을 제조하기 위한 방법으로 셀렌화(selenization)방식, MOCVD방식, 동시진공증발(co-evaporation)방식, 전착(electrodeposition)방식 등이 있으나, 이러한 방식을 이용하여 CuInSe2 박막을 제조하는 경우 어떤 방법으로든 다원화합물의 조성 및 결정성을 조절하기가 매우 어려운 단점이 있었다. 기판의 온도를 일정 온도로 유지하도록 하고, 증발원을 가열하여 이에 내포된 물질(이원화합물 또는 단일원소)을 증발시켜 기판에 증착이 이루어지도록 하거나, 기판의 온도를 승온시키고 구리 이원화합물을 내포한 증발원을 가열해 물질을 증발시켜 기판에 증착이 이루어지도록 하는 방법으로 기판에 박막이 형성되도록 한다. 기판의 대면적화로 인해 균일한 박막의 형성이 어려워지고 있으며, 이중 15% 이상의 고효율을 보인 방법은 3-stage process를 이용한 동시진공증발방식으로, Cu, In, Ga, Se 등의 각 원소를 동시에 진공 증발시키면서 조성을 조절하여 태양전지에 적절한 전기적, 광학적 특성을 가지는 Cu(In,Ga)Se2 (CIGS)박막을 증착시키는 방법이다. 일반적으로, 실험실에서 연구되고 있는 장비의 구조는 증발원이 아래에 장착되어서 상향 증착되는 방식이다. 본 연구에서 사용된 장비는 하향 증발원이 측면에 장착되어서 하향 증착되는 방식으로 구성하였다. 증착되는 면방향으로, 적외선온도계(pyrometer)가 설치된 시창(viewport)의 오염 등으로 인하여, 지속적인 공정이 이루어지기 힘든 점을 개선하여 증착기판의 후면에 적외선 온도계를 설치하여 기판의 온도변화를 감지하여 공정에 반영할 수 있도록 하였다. 본 연구에서는 하향식 진공 증발원, 기판후면 온도모니터링모듈 등을 개발 장착하여, CIGS 박막을 제조하였으며, 버퍼층은 moving 스퍼터링법으로 ZnS를 증착하였고, 투명전극층은 PLD(Pulsed Laser Deposition)를 이용하여 제조하였다. 가장 높은 광변환효율을 보인 Al/ZnO/CdS/Mo/SLG박막시료는 유효면적 $0.45cm^2$에 광변환효율 15.65 %, Jsc : $33.59mA/cm^2$, Voc : 0.64 V, FF : 73.09 %를 얻을 수 있었으며, CdS를 ZnS로 대체한 Al/ZnO/ZnS/Mo/SLG박막시료는 유효면적 $0.45cm^2$에 광변환효율 12.45 %, Jsc : $33.62mA/cm^2$, Voc : 0.59 V, FF : 62.35 %를 얻을 수 있었다.

• Journal of KIISE:Databases
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• 제30권2호
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• pp.197-208
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• 2003

Abstract Workflow is not appropriately applied to coordinated execution of applications(steps) that comprise business process such as a collaborative series of tasks because of the lacks of network infra, standard of information exchange and data consistency management with conflict mode of shared data. Particularly we have not mentioned the problem which can be occurred by shared data with conflict mode. In this paper, to handle data consistency in the process of rollback for failure handling or recovery policy, we have classified rollback dependency into three types such as implicit rollback dependency in a transactional workflow, implicit rollback dependency in collaborative transactional workflows and explicit rollback dependency in collaborative transactional workflows. Also, we have proposed the rollback dependency compiler that determines above three types of rollback dependency. A workflow designer specifies the workflow schema and the resources accessed by the steps from a global database of resources. The rollback dependency compiler generates the enhanced workflow schema with the rollback dependency specification. The run-time system interprets this specification and executes the rollback policy with data consistency if failure of steps is occurred. After all, this paper can offer better correctness and performance than state-of-the-art WFMSs.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제20권12호
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• pp.468-474
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• 2019

Korea had the highest accident rate among OECD countries in 2018, with 8.4 per 100,000 population, ranking 4th among 35 countries. In addition, the accident rate of traffic with children and the elderly was also high. This study reviewed the relevant literature and analyzed the traffic-accident analysis system. Customized traffic safety facilities were developed. In addition, by measuring the visibility of the traffic safety facilities by installing a test bed, this study measured the forward driving frequency and vehicle driving speed while driving. As a result of applying the "pedestrian pedestrian model" collision test model, the possibility of serious injury after installing the facility was reduced greatly to 4.6%. In this study, the visibility of traffic safety facilities and the effect of reducing the traffic speed were verified through test beds. Recognizing traffic safety facilities will reduce traffic accidents.

• Journal of Soil and Groundwater Environment
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• 제12권1호
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• pp.103-115
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• 2007

Risk assessment by living indicator species provides the information about the ecosystem disturbance, disapperance of symbiosis and change of living group. In the initial stage of this kind research, the degree of contamination was reported using the level of simple number, but simple number may not represent the risk itself which can be casued in the living organisms. Risk assessment using various indicator species overcomes these limitations and can be expanded to the DNA level. In many developed counties, the government has supervised the researches about the indicator species for the monitoring and its application to ecosystem restoration. Several living indicator species found in the vicinity of the abandoned Au mines such as fern, earthworm, bacteria, rhizosphere-rhizoplane, salamamdor and DNA change of these species are described in this paper.