• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.437-443
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• 2005

Controlling the friction between wheel and rail is direct and very effective measures to improve the curving performances of railway trucks, because the curving performances depend much on friction characteristics. Authors have proposed a method, 'friction control', which utilizes friction modifier ($KELTRACK^{TM}$ HPF) with onboard spraying system. With the method, not only friction coefficient, but also friction characteristics can be controlled as expected. In this study, MBD simulation is very valuable tool to foresee the effect of the control in advance of experiment with real car. And the creep characteristics of wheel/rail contact with the friction modifier takes very important role in the simulation. In this paper, authors propose a theoretical model of wheel/rail contact condition considering the creep characteristics of friction modifier, which is derived the application of principle tribological theories.

• Advances in Automotive Engineering
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• 제1권1호
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• pp.1-20
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• 2018

The aim of this study is the optimization of the parameters of interconnected Hydro-Pneumatic (HP) suspension system of a three-axle vehicle for ride comfort and handling. For HP suspension systems of equivalent vertical stiffness and damping characteristics, interconnected HP suspension systems increase roll and pitch stiffness and damping characteristics of the vehicle as compared to unconnected HP suspension systems. Thus, they result in improved handling and braking/acceleration performances of the vehicle. However, increased roll and pitch stiffness and damping characteristics also increase roll and pitch accelerations, which in turn result in degraded ride comfort performance. Therefore, in order to improve both ride comfort and vehicle handling performances simultaneously, an optimum parameter set of an interconnected HP suspension system is obtained through an optimization procedure. The objective function is formed as the sum of the weighted vertical accelerations according to ISO 2631. The roll angle, one of the important measures of vehicle handling and driving safety, is imposed as a constraint in the optimization study. Upper and lower parameter bounds are used in the optimization in order to get a physically realizable parameter set. Optimization procedure is implemented for a three-axle vehicle with unconnected and interconnected suspension systems separately. Optimization results show that interconnected HP suspension system results in improvements in both ride comfort and vehicle handling performance, as compared to the unconnected suspension system. As a result, interconnected HP suspension systems present a solution to the conflict between ride comfort and vehicle handling which is present in unconnected suspension systems.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2019년도 추계학술발표대회
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• pp.491-494
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• 2019

The results from the analysis of recent security breach cases of industrial control systems revealed that most of them were caused by the employees of a partner company who had been managing the control system. For this reason, the majority of the current company security management systems have been developed focusing on their performances. Despite such effort, many hacking attempts against a major company, public institution or financial institution are still attempted by the partner company or outsourced employees. Thus, the institutions or organizations that manage Industrial Control Systems (ICSs) associated with major national infrastructures involving traffic, water resources, energy, etc. are putting emphasis on their security management as the role of those partners is increasingly becoming important as outsourcing security task has become a common practice. However, in reality, it is also a fact that this is the point where security is most vulnerable and various security management plans have been continuously studied and proposed. A system that enhances the security level of a partner company with a Virtual Desktop Infrastructure (VDI) has been developed in this study through research on the past performances of partner companies stationed at various types of industrial control infrastructures and its performance outcomes were statistically compiled to propose an appropriate model for the current ICSs by comparing vulnerabilities, measures taken and their results before and after adopting the VDI.

• 경영과학
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• 제21권2호
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• pp.111-122
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• 2004

Measuring performance of corporate information system has become one of the core issues in that development of the information system requires substantial amount of investments and the system works as a crucial leverage to enhance competitive edge. Most of the previous researches for performance of the information system have narrow and limited focus on such as the effect of user satisfaction and productivity. This paper suggests a model to measures the comprehensive performance which is classified as user scope (user involvement and satisfaction), operational scope (task productivity, task innovation, customer satisfaction, management control) and efficiency scope (financial performance), and to represent the relationship among the scopes by the path analysis model. Followings are conclusions from statistical hypothesis test of the model: (i) user involvement through user satisfaction has positive effect on all the performances in the operational scope, (ii) task innovation and customer satisfaction in the operational scope has statistically significant impact on financial performance but task productivity and management control do not. This conclusion indicates that task productivity and management control has the long term effect in nature, and evaluation of the information system has managerial implication when it Is measured in comprehensive performance which includes internal operational performances as well as financial performance.

• 한국통신학회논문지
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• 제31권7A호
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• pp.666-673
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• 2006

본 연구에서는 송신 측이 전송한 데이터를 오류 없이 수신하기 위해 IEEE 802.16d 서 채택하고 있는 4가지 ARQ 기법을 전송오류가 빈번하게 발생하는 무선채널환경에서 성능을 분석하였다. NS-2 네트워크 시뮬레이터를 사용하여 성능평가를 위한 시뮬레이터를 구현하였고, 성능평가의 척도로 시뮬레이션 수행시간 동안 수신 측이 송신 측으로부터 오류 없이 순서대로 수신한 총 ARQ 블록의 바이트 수와 본 연구에서 새롭게 정의한 ACK-Efficiency를 사용하였다. 성능평가 결과에 따르면 각 ARQ 기법이 다양한 우선채널환경에 띠라 서로 상이한 성능을 제공함을 알 수 있었으며, 특정 채널환경에서 데이터 전송률을 높이기 위해서는 채널상태에 알맞은 ARQ 기법을 선택해야 하고, ARQ 기법의 적절한 ACK 전송주기를 선정하는 것이 중요함을 알 수 있었다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.804-807
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• 2006

The SRI(Super Resolution Imager) with 800mm aperture primary mirror is the ground development model of the high resolution satellite camera. The SRI focal plane electronics including detector array generates the data for high-resolution images by converting incoming light into digital stream of pixel data. Since the focal plane including a detector is the basic building block of the camera system, the main system performances is directly determined by its performance. This paper measures the SRI focal plane electronics’ performance such as the dark signal, the dark signal noise, the linearity, the PRNU(Photo Response Non-Uniformity), the SNR(Signal to Noise Ratio) and the sensor saturation capability. In addition, this paper verifies the various functionalities of the SRI focal plane electronics. The electrical test equipment with the specialized software and the optical test equipments such as the integrating sphere, the rotation stage and the target are implemented and used to verify these functionalities and performances.

• 한국생활과학회지
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• 제15권4호
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• pp.551-561
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• 2006

The purpose of the study is to examine the influence of children's familiarity with a task and teachers' feedback on their problem solving performances. It was assumed that children's' problem solving performance would be different depending on the children's familiarity with a task and the feedback from teachers. The study also examined whether children's' problem solving competence would be different depending on their gender and age. The experiment was conducted with two experimental tools. The subjects were 58 children who were 5 to 6-year-old, enrolled in kindergartens in Koyang city in Kyunggi province. The collected data were processed with SPSS 11.0 program to get the average and the standard deviations, and with one-way ANOVA and two-way ANOVA with repeated measures. The results of the experiment are as follows; First, children's' problem solving competence was different depending on their age. Older children showed higher performance than younger children, while there's no difference in children's performance depending on their gender. Second, the teachers' feedback didn't influence children's problem solving performance. Third, children showed higher performance when familiar tasks were provided, compared to when typical tasks were provided. Finally, this study found that children's task familiarity has an influence on their problem solving performance.

• 응용통계연구
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• 제35권5호
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• pp.645-655
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• 2022

본 논문에서는 R에서 시계열 자료 예측을 위한 자동화 함수에 대하여 고찰하고 그 예측 성능을 비교합니다. 대표적인 시계열 예측 방법인 지수 평활 모형과 ARIMA (autoregressive integrated moving average) 모형을 대상으로 하였으며, 이들의 모형화 및 예측 자동화를 가능하게 하는 R의 4가지 자동화 함수인 forecast::ets(), forecast::auto.arima(), smooth::es()와 smooth::auto.ssarima()를 대상으로 하였습니다. 이들의 예측 성능을 비교하기 위하여 3,003가지의 시계열로 구성되어 있는 M3-Competition자료와 3가지의 정확성 척도를 사용하였습니다. 4가지 자동화 함수는 모형화의 다양성 및 편리성, 예측 정확도 및 실행 시간 등에서 각자 장단점이 있음을 확인하였습니다.

• 한국지구과학회지
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• 제23권4호
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• pp.324-333
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• 2002

최근의 연구들은 과학영역에서 남학생이 여학생에 비해 훨씬 더 높은 학업 성취도를 보인다고 주장하고, 과학영역에서의 창의성 측면에서도 남학생이 여학생에 비해 더 높은 창의적 성취를 보일 것이라는 것이 일반적인 통념이다. 과학영재교육이 본격화되고 남${\cdot}$여 과학영재들의 창의적 특성에 대한 이해의 중요성이 부각되고 있지만, 이를 뒷받침할 연구들은 거의 부재한 상황이다. 본 연구에서는 135명의 과학영재학생들을 대상으로 창의성의 다양한 영역에서, 특히 확산적 사고라는 영역 보편적 입장과 과학에서의 창의적 행동특성과 문제해결 및 발견이라는 영역 특수적 입장에서, 남학생과 여학생간의 창의성의 차이를 살피고 창의성의 본성에 대한 이해를 돕고자 했다. 본 연구의 결과는 과학 영재여학생들이 남학생들에 비해 모든 영역에서 유의미하게 큰 차이를 보이지는 않았지만, 전반적으로 창의성의 세 영역 모두에서 상대적으로 높은 성취를 보이는 것으로 나타났다. 구체적으로 살펴보면 확산적 사고의 융통성, 제목의 추상성, 정교성 영역에서, 과학에서의 창의적 문제 해결력 및 문제 발견력을 측정하는 CPSF의 가설 설정 능력의 유창성과 독창성 영역에서, 그리고 과학에서의 창의적 행동 특성을 측정하는 CBCS에서 개방성, 심미안에서 과학 영재 여학생이 남학생보다 유의미하게 창의성이 높은 것으로 나타났다. 남학생은 여학생에 비해 CBCS에서의 '과학적 호기심' 문항에서만 유의미하게 더 높은 창의성 점수를 보임으로 본 연구 결과는 '남학생이 여학생보다 더 창의적이다'라는 사회의 일반적인 통념과 상반된 결과를 보였다.

• 대한기계학회논문집A
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• 제41권9호
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• pp.817-823
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• 2017

기존에는 연비를 고려한 적응형 순항 제어 알고리즘 개발과 연비 등의 성능을 고려한 적응형 순항 제어 시스템 개발 연구가 수행되었지만, 제어 파라미터를 포함한 차량 파라미터의 적응형 순항 제어에 대한 최적설계 연구는 미흡한 편이다. 이에 본 논문에서는 연비, 추종성, 승차감, 안전거리를 고려한 차량 및 제어 파라미터 최적설계를 수행하고자 한다. 이를 위해 차량 거동의 성능 측정 방법을 제안하고 적응형 순항 제어 시스템을 구축하였다. 그리고 성능에 주요한 영향을 미치는 차량 파라미터를 선별하여 이를 토대로 순차적 실험계획을 통해 크리깅 대체모델을 구축하였고, 연비를 최대화하며 목표 성능을 만족하는 크리깅 대체모델 기반 최적설계를 수행하였다.