• 대한기계학회논문집
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• 제19권5호
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• pp.1176-1181
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• 1995

Microdrilling is one of the most difficult operations because of the poor chip discharge and the weakness of tool. This study is concerned about the development of a microdrilling monitoring system that is useful for minimizing the tool breakage and enhancing the machinability in the air spindle based microdrilling. The system is composed of a drilling state detection unit and an adaptive step-feed control unit that controls the micro-stepping motor driven spindle axis. Drilling states such as overload, tood breakage are recognized by the change of the air spindle speed which is measured via the reflective photo sensor. Based on the monitoring results, the adaptive step-feed control algorithm adjusts the step increment to keep the decrease of spindle speed within a specified range. The results of evaluation tests have shown that the developed system is very effective to prevent the breakage of microdrill and improves the productivity in comparison with the conventional microdrilling.

• 한국물환경학회지
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• 제22권1호
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• pp.110-115
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• 2006

Flooding situation of Sutak basin was simulated and simulation seemed to be consistent with the real flooding situation in terms of high water levels and timings of flooding. The flood simulation model was used to evaluate alternatives to mitigate flooding problems in Sutak basin. From the evaluation of flood mitigation plans, it was found that combined operation of Sutak and Inchang pumping stations through partial diversion of inflow of Sutak pumping station to Inchang pumping station was the most effective one among the suggested mitigation plans. About 500 meter diversion channel will be needed to send 30% of Sutak pumping station inflow to Inchang pumping station. This will reduce overload of Sutak pumping station and the storage capacity of Inchang pumping station will be more efficiently utilized.

• 대한인간공학회지
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• 제18권1호
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• pp.133-147
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• 1999

Traffic signs without a cognitive consideration in their design may cause information-processing problem that could result in a mental confusion among drivers often lead to a serious traffic accident. Therefore, in this study, several traffic signs currently used in Seoul Metropolitan area have been sampled and analyzed to identify design problems that usually caused by neglecting drivers cognitive ability. To classify the practical design problems, five major information-processing problems have been suggested: indistinguishable information, information conflict, missing information, sign-load mismatch, and information overload. In order to solve these cognitive problems, new traffic signs have been suggested in this study. An experiment was also performed to validate the new traffic sign. Twenty-four healthy subjects participated in the experiment. They were asked to answer the Question after observing the traffic signs continuously displayed on computer screen. The result indicated that subjects improved the accuracy in understanding the signs by 1.4 times when they used the suggested traffic sign compared to the old one. Based upon the results, a cognitive guideline was suggested for correct and speedy reading of traffic signs by improving information processing and reducing of human error. In conclusion, the traffic sign may well be applied to design an intelligent traffic sign system to increase the safety and comfort of drivers, especially in complex load condition.

• Journal of Information Processing Systems
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• 제8권4호
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• pp.721-738
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• 2012

The Internet has become an increasingly important source for finding the right employees, so more and more companies post their job openings on the Web. The large amount and dynamic nature of career recruiting information causes information overload problems for job seekers. To assist Internet users in searching for the right job, a range of research and commercial systems were developed over the past 10 years. Surprisingly, the majority of existing job search systems support just one, rarely two ways of information access. In contrast, our work focused on exploring a value of comprehensive access to job information in a single system (i.e., a system which supports multiple ways). We designed Proactive, a recommendation system providing comprehensive and personalized information access. To assist the varied needs of users, Proactive has four information retrieval methods - a navigable list of jobs, keyword-based search, implicit preference-based recommendations, and explicit preference-based recommendations. This paper introduces the Proactive and reports the results of a study focusing on the experimental evaluation of these methods. The goal of the study was to assess whether all of the methods are necessary for users to find relevant jobs and to what extent different methods can meet different users' information requirements.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.129-137
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• 1999

Reinforced concrete structures using early age concrete were result in the degradation of structural performance due to crack, overload, unexpected vibration and impact load. It demands urgently that reinforced concrete structure using early age concrete should be improved the serviceability and structural performance with the application of new fiber materials. Therefore specimens, designed by the test varibles, such as with or without stirrup and percent of steel fiber incorporated, were constructed and tested to evaluate and develop the structural performance of reinforced steel fiber concrete beam. Based on the test results reported in this study, the following conclusions are made. Specimens, designed by the over 0.75% of steel fiber incorporated, were showed the ductile behavior and failed slowly with flexure and flexure-shear. Comparing with the load-displacement relationship of specimen BSS, designed by the recommendations of the Ministry of Construction and Transportation, reinforced steel fiber concrete beam using early age concrete, over 0.75% of steel fiber incorporated, gets enough load carrying capacity and ductility. Increasing the percent of steel fiber incorporated(0.25~2.0%), the ultimate shear stress of each specimen were increased 12~40% than that of control specimen SSS.

• 한국정밀공학회지
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• 제12권5호
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• pp.98-107
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• 1995

The in-process detection of drill wear and breakage is one of the most importnat technical problems in unmaned machining system. In this paper, the monitoring system is developed to monitor abnormal drilling states such as drill breakage, drill wear and unstable cutting using motor current. Drill breakage is detected by level monitoring. Tool wear is classified by fuzzy pattern recognition. The key feature for classification of tool wear is the estimated flank wear which is calculated by the proposed flank wear model. The characteristic of the model is not sensitive to the variation of cutting conditions but is sensitive to drill wear state. Unstable cutting states due to the unsmooth chip disposal and the overload are monitored by the variance/mean ratio of spindle motor current. Variance/mean ratio also includes the information about the prediction of drill wear and drill breakage. The evaluation experiments have shown that the developed system works very well.

• 풍력에너지저널
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• 제10권4호
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• pp.20-27
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• 2019

High-speed shaft coupling in a wind power system transmits power and absorbs variations in length and spindle dislocation between the gearbox and generator. Furthermore, the coupling has an insulation function that prevents electrical corrosion caused by the flow of the generator's current into the gearbox and prevents overload resulting from sudden power failure from being transferred to the gearbox. Its design, functions, and part verification are described in the IEC61400 and GL Guidelines, which specify that the part must have a durability life of 20 years or longer under distance variation and axial misalignment between the gearbox and the generator. This study presents the design of a high-speed coupling through composite stiffness calculation, structural analysis, and comparative analysis of test and theory to identify the characteristics of high-speed coupling for a large-capacity 6 MW wind power generator. A prototype was fabricated by optimizing the manufacturing process for each part based on the design, and the reliability of the fabricated prototype was verified by evaluating the performance of the target quantitative evaluation items.

• 벤처혁신연구
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• 제1권2호
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• pp.75-87
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• 2018

본 연구는 동일 기업의 국내 직원과 중국 지사의 중국인 직원들을 대상으로 직무스트레스 요인의 종류과 스트레스 수준이 어떻게 다른지를 확인하고자 하였으며 연구 결과는 다음과 같다. 직무스트레스 관련 주요 원인에서 유의한 차이가 검증되었는데, 한국 직원은 중국 직원보다 경계 및 집단 갈등, 감독 및 평가, 역할과부하, 과제특성, 인구통계학적 특성으로 인한 스트레스 요인을 더 크게 지각한 반면, 중국 직원은 한국 직원보다 역할갈등 및 역할모호성, 가정으로 인한 스트레스 요인을 더 크게 지각하였다. 스트레스 수준에서는 불안, 우울, 신체적 징후 등에서 전반적으로 한국 직원이 중국 직원보다 더 높은 점수를 보였으며, 특히 불안과 우울 차원의 점수는 통계적으로 유의미하게 높은 것으로 나타났다. 직무스트레스 요인이 직무스트레스 정도에 미치는 영향에 있어서, 한국인 직원의 경우는 감독 및 평가, 의사결정 및 책임, 가정 요인이 유의미하게 나타난 반면, 중국인 직원의 경우는 가정, 사회적 지원, 인구통계학적 요인이 유의미하게 나타났다. 본 연구의 시사점과 제한점, 그리고 향후 연구 과제에 대해서 논의하였다.

• 한국시뮬레이션학회논문지
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• 제17권3호
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• pp.1-8
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• 2008

멀티미디어 서비스의 QoS가 전송 지연 및 패킷 손실에 의하여 현저히 저하될 수 있으므로, 멀티미디어 데이터의 전송 동안 셀 부하와 무선 링크의 에러에도 불구하고 연속적인 QoS를 유지하는 것이 필요하다. 본 논문은 이종 망상에서 멀티미디어 서비스의 QoS를 지원하기 위한 셀 선정 방법을 다룬다. 제안된 방식은 사용자 시스템 선호도, 통신비용, 셀 부하 그리고 전송지연과 같은 다수의 부정확한 요소가 퍼지 집합 함수를 사용한 의사 결정에 사용되는 다기준 의사 결정 방법에 근거한다. 이 방법은 이진 논리를 사용하는 경우보다 의사 결정 시 평가 항목의 오차가 총체화된 평가치에 완만한 변화를 유발하고 최종적인 기준치를 변화시켜 셀 선정의 유연선을 증가시킬 수 있다. 시뮬레이션을 통하여 평균 지연과 패킷 손실률을 평가하고, 제시한 셀 선정 방법이 이동 단말기에게 최적의 성능을 제공함을 보인다.

• 한국콘텐츠학회논문지
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• 제21권12호
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• pp.662-675
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• 2021

본 연구는 전라북도 사회복지심부름센터의 효과성을 평가하기 위해 이용자의 개인특성 및 종사자 직무환경특성이 이용만족도에 미치는 영향을 파악함에 주목한 연구이다. 분석 자료는 전라북도 각 시·군 사회복지심부름센터 11개소의 이용자 및 종사자를 대상으로 수집한 서베이 자료이다. 구체적인 분석에서는 이용자들의 개인특성은 1수준 독립변수, 종사자의 직무환경 특성은 2수준 독립변수, 이용만족도를 종속변수로 설정한 다음 위계적 선형모형분석 모델을 적용하였다. 분석결과 장애인 가구, 직무가치감, 직무스트레스, 역할과다, 급여만족도가 이용자의 서비스 만족도에 유의미한 영향을 미침을 확인할 수 있었다. 이와 같은 분석결과는 종사자의 직무환경특성이 서비스 이용자들의 만족도에 주요한 영향을 보여주는 바로, 사회복지심부름센터 이용자들의 만족도를 높이기 위해서는 직무가치감, 직무스트레스, 역할과다, 급여만족도 등의 종사자의 직무환경 측면들에의 개선이 적극 필요함을 시사하여 준다.