• 한국정밀공학회지
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• 제21권1호
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• pp.109-115
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• 2004

Polishing process has been applied to get extremely fine surfaces, e.g., mirror surfaces such as optical mirrors, lens, molds and etc. Nowadays not only fine surface quality but also submicron order of dimensional accuracy is required for many applications. To meet the requirements polishing process should be provided with an active control of polishing pressure especially for automation of polishing process. In this paper a study on development of an active polishing pressure control system has been presented. A new type of tool assembly has been developed to facilitate the control. The tool is attached to an axis of a polishing machine with a coil spring and control of the polishing pressure is done by the position control of the axis, which needs no additional actuator. The polishing pressure is successfully measured by the measurement of the spring deformation. Control specifications were quantitatively considered by weighting functions and a controller was designed by using loop-shaping technique based on the no synthesis. Some experiments have been executed on a polishing machine with a PC-NC controller. It is shown that the results were coincident well with the theoretical analyses and satisfied the design specifications.

• 영어어문교육
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• 제16권4호
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• pp.153-184
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• 2010

On the bases of the 5 principles and the 4 criteria for designing and developing of the listening and the reading test of National English Ability Test (NEAT), this study presents Item-Types Decision-Making Model as a blueprint for designing and constructing the two tests. It sets up the criteria for validating item types, designs a modular type of test specifications, constructs an item-types bank, and specifies a complementary type of test specifications of the two tests. To gather all these threads up, it constructs Item-Types Decision-Making Model which consists of such components as the item-type pool, the validity criteria and the procedures of testing item types, the item-types bank, the modular and the complementary type test specification. Thus, it shows how the Model works in developing and constructing the two level-differentiated listening and reading tests (the 2nd and the 3rd rank) of NEAT. Finally, it discusses some implications and applications of the Model to the two level-differentiated tests (the A and the B type) of 2014 CSAT (College Scholastic Ability Test) systems, National Assessment of Educational Achievement (NAEA), and classroom testing. In conclusion, Item-Types Decision-Making Model functions as a testing template in an item development system and as a matrix in an item-types bank system.

• 한국소음진동공학회논문집
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• 제21권8호
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• pp.741-751
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• 2011

Vibrations caused by automobile engine are absorbed mostly by a passive-type engine mount. However, user specifications for automobile vibrations require more stringent conditions and higher standard. Hence, active-type engine mounts have been developed to cope with such specifications. In this study, the active vibration absorber which can be attached to the sub-frame of automobile is used for the suppression of vibrations caused by engine. The active vibration absorbing system consists of sensor, actuator and controller where a control algorithm is implemented using DSP. The vibration caused by engine reveals harmonic disturbances varying with engine revolution. Therefore, the control algorithm should be able to cope with harmonic disturbances. In this study, the modified higher harmonic control technique which can selectively suppress harmonic disturbance is considered. Experimental results on automobile show that the proposed active vibration absorbing system is effective in suppressing vibrations caused by engine.

• 한국항공우주학회지
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• 제39권8호
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• pp.788-795
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• 2011

본 논문에서는 각종 탑재체에 가장 광범위하게 사용되는 중급성능의 레이저 관성항법 장치에 적용 가능한 소형 링레이저 자이로를 설계하기 위한 요구규격을 제시한다. 이를 위하여 우선 중급성능 관성항법장치 구성을 위하여 요구되는 링레이저 자이로의 요구 성능규격을 분석하였다. 그리고 이를 만족시키기 위하여 해외기술 조사 및 이론적으로 분석을 통하여 링레이저 자이로 시스템을 설계한 결과를 제시하였으며 요구 기술을 정리하였다.

• Structural Engineering and Mechanics
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• 제29권5호
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• pp.489-504
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• 2008

In piezoelectric flexible structures, the contribution of vibration modes to the dynamic response of system may change with the location of piezoelectric actuator patches, which means that the ability of actuators to control vibration modes should be taken into account in the development of modal reduction model. The spatial $H_2$ norm of modes, which serves as a measure of the intensity of modes to system dynamical response, is used to pick up the modes included in the reduction model. Based on the reduction model, the paper develops the state-space representation for uncertain flexible tructures with piezoelectric material as non-collocated actuators/sensors in the modal space, taking into account uncertainties due to modal parameters variation and unmodeled residual modes. In order to suppress the vibration of the structure, a dynamic output feedback control law is designed by imultaneously considering the conflicting performance specifications, such as robust stability, transient response requirement, disturbance rejection, actuator saturation constraints. Based on linear matrix inequality, the vibration control design is converted into a linear convex optimization problem. The simulation results show how the influence of vibration modes on the dynamical response of structure varies with the location of piezoelectric actuators, why the uncertainties should be considered in the reductiom model to avoid exciting high-frequency modes in the non-collcated vibration control, and the possiblity that the conflicting performance specifications are dealt with simultaneously.

• 대한인간공학회지
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• 제27권4호
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• pp.65-71
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• 2008

This study conducted two surveys to establish an educational system to prevent work-related musculoskeletal disorders. The first survey investigates the factors influencing the recognition of job specifications for risk factor analysts of work-related musculoskeletal disorders. The respondents of the first survey were selected from 173 different small-sized manufacturing enterprises having less than 300 workers and had experienced the inspection of risk factors. The results of the first survey shows that better recognition of job specifications are followed by the increase of education time, but regardless of the positions and periods of job experience. Among the respondents with a high level recognition, the second survey was conducted. According to the results, it is presented that 2, 8, 16 hours are the most suitable for educating workers, superintendents, and risk factors analysts. Based on the results of the second survey, educational contents have also been suggested. This research will provide the basic information when forming education systems to prevent musculoskeletal disorders.

• Tribology and Lubricants
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• 제38권1호
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• pp.22-26
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• 2022

A 1.7-ton grade small excavator is a construction equipment that can perform various functions in limited spaces where heavy equipment cannot enter easily. Owing to the recent acceleration of urbanization, it has been used increasingly in drainage and gas pipes, as well as for road repair works in urban areas. The power train of a traveling reducer for a 1.7-ton grade small excavator utilizes a complex planetary gear system. Complex planetary gears are vital to the power train of a traveling reducer as it mitigates the fatigue strength problem. In the present study, the specifications of a complex planetary gear train are calculated; furthermore, the gear bending and compressive stresses of the complex planetary gears are analyzed to achieve an optimal design of the latter in terms of cost and reliability. In this study, the actual gear bending and compressive stresses of a planetary gear system are analyzed using a self-developed gear design program based on the Lewes and Hertz equation. Subsequently, the calculated specifications of the complex planetary gears are verified by evaluating the results with the data of allowable bending and compressive stress based on curves of stress vs. number of cycles of the gears.

• 항공우주시스템공학회지
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• 제17권2호
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• pp.71-77
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• 2023

액상성형공정(LCM, Liquid Composite Molding) 은 복합재료 오토클레이브(Autoclave) 성형공정의 단점을 극복할 수 있는 탈 오토클레이브(OoA, Out of Autoclave) 공정의 하나로 매우 복잡한 형상이나 대형 구조물을 일체형으로 만들 수 있어 항공산업에서 큰 경쟁력을 가진 공법으로 알려져 있다. 이러한 장점 때문에 액상성형공정을 적용한 항공 부품제작 수요가 늘고 있으며 FAA에서는 액상성형공정을 적용한 복합재료에 대한 인증(Qualification) 방법을 제시한 바 있다. 국내에서도 액상성형공정 적용 복합재료에 대한 부품제작 수요 및 재료인증 수요가 꾸준히 제기되고 있다. 따라서 본 연구에서는 기존에 구축된 프리프레그 복합재료 인증방안 이외에 LCM 공정을 적용한 복합재료에 대한 인증방안을 수립하기 위한 연구를 진행하였다.

• 방송공학회논문지
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• 제19권6호
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• pp.847-853
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• 2014

재난이 발생한 경우, 재난경보를 신속 정확하게 전달하면 인명과 재산피해를 최소화 할 수 있다. 통합경보시스템은 효과적인 경보전달을 위해 기존의 경보시스템을 통합하여 운영하는 국가재난관리시스템이다. 통합경보시스템을 위한 가장 핵심적인 기술은 경보메시지 교환 프로토콜이다. 우리나라에서는 2014년 "통합경보시스템을 위한 공통경보프로토콜 프로파일"이 TTA표준으로 제정되었다. 본 논문에서는 경보서비스를 향상시키기 위한 요구사항을 도출하고, 이를 "통합경보시스템을 위한 공통경보프로토콜 프로파일"에 반영하기 위한 방법을 제안하였다. 경보서비스를 향상시키기 위해서는 외국인을 위한 다국어 경보 서비스가 필요하고, 더 효과적인 위치기반 경보서비스를 위해 다양한 지역 표현 방법을 활용할 수 있어야 한다. 본 논문에서는 이와 같은 요구사항을 반영하기 위해 공통경보프로토콜 표준과 해외의 프로파일을 분석하여 다양한 다국어 지원방법을 도출하고, 가장 효율적인 다국어 경보메시지 전송방법과 지역 표현 방법을 제안하였다.

• 한국통신학회논문지
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• 제42권3호
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• pp.585-594
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• 2017

무선 Docking 시스템은 기존에 설치된 모니터, 키보드 등의 별도 환경을 통하여 스마트폰 등의 이동형 컴퓨팅 장치 사용에 편의성을 제공하는 환경으로써, 사용자는 Docking 시스템이 구축된 어느 환경에서라도 자신의 이동형 컴퓨팅 장치를 다양한 주변 장치들을 활용하여 편리하게 사용할 수 있다. Docking 시스템은, 컴퓨팅 장치를 중심으로 구축된 기존 데스크탑 및 Laptop 환경과 달리, 컴퓨팅 장치를 제외한 주변 장치들로 구성되어 있다. Wi-Fi Alliance에서는 이러한 환경을 제공하기 위하여 Wi-Fi Docking 표준화를 최근 진행 중이며, 기존에 발표된 Wi-Fi Direct 표준 기술(Wi-Fi Peer-to-Peer Technical Specifications v1.2, 2010)을 활용하고 있다. 하지만, Docking 시스템에서 Bluetooth 장치를 사용할 경우 인터페이스 상이로 인하여 복잡한 Connectivity가 발생될 수 있다. 본 고에서는 이러한 문제를 해결하기 위하여 Wi-Fi Direct 환경에서 Bluetooth 장치 연결을 Tunneling 할 수 있는 기술을 설계하고 실험을 통하여 분석하였다.