• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.176-181
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• 1994

As tools for machining precesion componants, end mills and ball end mill are widely used. For the end mill have longer cylindrical shape comparing diameter, they are liable to deflect when machining and induce geometrical error and deterioration of surface roughness. To improve the stiffness and the sharpness of the cutting edge of end mill, a software for manufaturing end mills are developed. The progeam predicts the result of helical flute grinding and the configuration of cutting edge which is located in cylindrical surface. Furthermore to facilitate the manufacturing end mill using CNC grinding machine, the setting conditions which satisfy the geometrical requirments like tool rake angle and stiffness are obtained.

• Journal of Electrical Engineering and Technology
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• 제6권1호
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• pp.42-47
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• 2011

Automatic generation control (AGC) is an important function for load frequency control, which is being implemented in Energy Management System (EMS). A key feature of AGC is to back up governors to enhance the performance of frequency control. The governor regulates system frequency in several to ten seconds, while the droop control concept results in steady-state control error. AGC is a supplementary tool for compensation of the steady-state error caused by the droop setting of the governors. As the AGC target is delivered to each generator as an open loop control target, the generator output is not guaranteed to follow the AGC target. In this paper, we introduce generating unit controller (GUC) control block, which has the purpose of enabling the generator output to track the AGC target while maintaining the governor performance. We also address the tuning methods of GUC for better performance of AGC in the Korea Energy Management System (K-EMS).

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2016년도 춘계학술대회
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• pp.181-185
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• 2016

본 논문은 선원 훈련을 보다 효율적으로 수행하기 위한 가상현실 기반 선원 훈련 플랫폼을 위한 저작도구를 제안한다. 제안하는 저작도구는 훈련의 효율도를 높이기 위해 실 선박 환경을 3D 스캔하여 가상현실 환경으로 불러오는 가상환경 구축부와 다양한 시나리오 기반의 훈련 내용을 소화할 수 있는 드래그-앤-드롭 기반의 스크립트 편집부를 지원한다. 본 저작 도구에서는 가상현실 장비들을 지원하고 실환경을 3D 스캔을 통해 가상 현실로 변환하기 때문에 피훈련자는 훈련이 필요한 실환경 내에서 요구되는 동일한 훈련을 이행하게 됨으로써 피훈련자의 몰입감과 훈련 효과를 높인다. 또한 다양한 선박 환경에 대한 훈련 시뮬레이션을 빠른 시간 내에 제작할 수 있게 함으로써 제작에 필요한 비용을 줄인다. 본 저작도구는 시나리오 편집부를 통해 다중 참여형 훈련 시나리오의 편집과 임무 평가를 가능하게 한다.

• 지식경영연구
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• 제13권2호
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• pp.37-52
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• 2012

A spreadsheet is a office automation software which has been widely used in almost all areas in business. A spreadsheet is used for calculation, data analysis, model building and so on. As a result, spreadsheet is a very important tool for generating knowlege in a firm. Errors in a spreadsheet model can cause a serious financial damage in a corporation. However in Korea few researches for reducing errors have been performed. Neither serious efforts to reduce errors have been executed by corporations. In this research we provided summarized the results from a survey for spreadsheet usage, summarized researches on errors in spreadsheet up to now, and suggested a rules and structured development method for reducing errors in a spreadsheet. Errors in spreadsheets are prevalent. To solve this serious problem, we need much more attention on this problem in research area. Corporations must put more efforts on setting policies and rules. And also we need the government's concern and support.

• 한국정보전자통신기술학회논문지
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• 제9권5호
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• pp.496-502
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• 2016

본 논문에서는 소프트웨어 제품을 개발하여 테스팅을 하는 시행에서 소프트웨어 운용자들이 소프트웨어 검사 도구에 적용할 수 있는 학습기법에 근거한 NHPP 소프트웨어 모형에 대하여 비교 연구 하였다. 수명분포는 Makeham 분포를 이용하고 유한고장 NHPP모형을 적용하였다. 소프트웨어 오류 탐색 방법은 미리 인지하지 못하지만 자동적으로 발견되는 에러에 영향을 주는 영향요인과 사전경험에 기초하여 에러를 관찰하기 위하여 테스팅 운용자가 미리 설정해놓은 요인인 학습효과의 영향에 대한 문제를 비교 분석하였다. 그 결과 학습요인이 자동 에러 탐색요인보다 큰 경우가 일반적으로 효율적인 모형으로 나타났다. 본 논문의 신뢰특성분석에서는 소프트웨어고장시간을 적용하고 모수추정 방법은 최우추정법을 적용하고 추세분석을 통하여 자료의 신뢰성을 확보한 이후에 평균제곱오차와 $R^2$ (결정계수)를 적용하여 효율적인 모형을 선택 비교 분석하였다. 이 연구를 통하여 소프트웨어 운영자들은 다양한 학습효과를 고려함으로서 소프트웨어 고장추세에 대한 기본지식을 파악하는데 하나의 지침으로 사용가능함을 보여주고 있다.

• 한국방사선학회논문지
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• 제14권5호
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• pp.619-626
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• 2020

이 연구의 목적은 경피적 혈관내 풍선 확장술이나 스텐트 삽입술에서 Balloon이나 Stent의 직경 및 길이를 예측 할 때 사용되는 정량적인 평가 도구인 Calibration Mode중 Catheter Calibration Mode, Auto Calibration Mode 그리고 Segment Calibration Mode에서의 오차율에 대해 알아보고자 하였다. Calibration의 정량적인 평가를 위해 정교하게 제작된 직경 × 길이(2 mm × 80 mm) Copper Wire와 5, 10, 15, 30, 40 mm의 Metal Ball을 이용하여 실험하였고, 아크릴 팬텀은 25 mm, 50 mm, 75mm, 100 mm, 125 mm, 150mm, 175 mm, 200 mm로 하여 각각의 높이에서 혈관조영 촬영장치로 Subtraction 영상을 획득하여 장비 회사에서 제공하는 소프트웨어인 Stenosis Analysis Tools을 이용하여 측정하였다. Catheter Calibration Mode에서의 오차율을 평가하기 위한 방법으로 Copper Wire를 각각의 아크릴 팬텀위에 올려놓고 촬영하였으며, Copper Wire 직경 2 mm를 Catheter의 직경으로 Setting하였고, 길이 8 mm Copper Wire의 길이를 Multi-segments로 측정하여 분석한 결과 1.13 ~ 5.63%의 오차율이 나타났다. Auto Calibration Mode에서의 오차율을 평가하기 위한 방법으로 각각의 아크릴 팬텀을 높이에서 아크릴 높이에 대한 수치를 입력하고, 8 mm Copper Wire의 길이를 Multi-segments 측정하여 분석한 결과 0 ~ 0.26%의 오차율이 나타났다. Segment Calibration Mode에서의 오차율을 평가하기 위한 방법으로 테이블 바닥에 있는 각각의 Metal Ball을 각각 Calibration하고, 각각의 아크릴 팬텀 위에 올려 있는 8 mm Copper Wire의 길이를 측정하여 아크릴 팬텀 높이 변화에 대한 8 mm Copper Wire 길이를 Mutli-segments 측정하여 분석한 결과 1.05 ~ 19.04%의 오차율이 나타났다. 그리고 Auto Calibration Mode에서 OID 변화에 대한 실험은 아크릴 팬텀의 높이는 100mm로 고정하고 OID만 450 mm ~ 600 mm로 변화를 하였을때 오차율은 0.13 ~ 0.38%로 나타났다. 결론적으로 소프트웨어에서 제공하는 정량적인 혈관의 치수평가를 하기 위한 이들 Calibration Mode 중 Auto Calibration Mode에서 높이 값을 입력하는 것이 오차율이 가장 적은 Calibration 방법임을 확인하였으며, Metal ball이나 기타 다른 물체를 이용하여 Calibration을 하기 위해서는 시술부위와 동등한 높이에 놓고 Calibration을 하는 방법이 오차율을 가장 줄일 수 있는 방법으로 사료된다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.252-257
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• 2000

This paper describes a look-ahead algorithm of PCNC(personal computer numerical control). The algorithm is based on acceleration/deceleration before interpolation never including a command error and determines a velocity value in end point of each block(or start point of each block). The algorithm is represented as following; 1) calculating two maximum arrival velocity(v1, v2) by a acceleration value, a command velocity and distance in a previous block and a next block, 2) getting a tangent velocity(v3) of the adjacent blocks, 3) choosing a minimum value among these three velocities, and 4) setting the value to a velocity of a start point of the next block(or a end point of the previous block). The proposed look-ahead algorithm was implemented and tested by using a commercial RTOS(real time operation system) on the MS-Windows NT 4.0 in a PC platform. For interfacing to a machine, a counter board, a DAC board and a DIO board were used. The result of the algorithm increased a machining precision and a machining speed in many short blocks.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.659-664
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• 2000

In this paper, We have discussed on the modeling of machined outer geometry which was established for the case of round shape machining, also the effects of externally machined profile are analyzed and its modeling realiability was verified by the experiments of roundness testing, especially in lathe operation. In this study, we established harmonic geometric model with the parameter harmonic function. In general, we can calculate the theoretical roundness profile with arbitrary multilobe parameter. But in real experiments, only 2-5 lobe profile was frequently measured. the most frequently ones are 3 and 5 lobe profile in experiments. With this results, we can predict that these results may be applies to round shape machining such as turning, drilling, boring, ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. In this study, simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling method in real process for the prediction of part profile behaviors machined such as in round shape machining operation.

• International Journal of Reliability and Applications
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• 제3권1호
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• pp.1-16
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• 2002

In reliability engineering, the bathtub-shaped hazard rates play an important role in survival analysis and many other applications as well. For the bathtub-shaped, initially the hazard rate decreases from a relatively high value due to manufacturing defects or infant mortality to a relatively stable middle useful life value and then slowly increases with the onset of old age or wear out. In this paper, we present a new two-parameter lifetime distribution function, called the Loglog distribution, with Vtub-shaped hazard rate function. We illustrate the usefulness of the new Vtub-shaped hazard rate function by evaluating the reliability of several helicopter parts based on the data obtained in the maintenance malfunction information reporting system database collected from October 1995 to September 1999. We develop the S-Plus add-in software tool, called Reliability and Safety Assessment (RSA), to calculate reliability measures include mean time to failure, mean residual function, and confidence Intervals of the two helicopter critical parts. We use the mean squared error to compare relative goodness of fit test of the distribution models include normal, lognormal, and Weibull within the two data sets. This research indicates that the result of the new Vtub-shaped hazard rate function is worth the extra function-complexity for a better relative fit. More application in broader validation of this conclusion is needed using other data sets for reliability modeling in a general industrial setting.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.1226-1236
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• 2022

Because students majoring in construction-related fields must develop a broad repository of knowledge and skills, effective transferal of these is the primary focus of most academic programs. While inculcation of this body of knowledge is certainly critical, actual construction projects are complicated ventures that involve levels of risk and uncertainty, such as resistant neighboring communities, unforeseen weather conditions, escalating material costs, labor shortages and strikes, accidents on jobsites, challenges with emerging forms of technology, etc. Learning how to develop a level of discernment about potential ways to handle such uncertainty often takes years of costly trial-and-error in the proverbial "school of hard knocks." There is therefore a need to proactively expedite the development of a sharpened intuition when making decisions. The AGC Education and Research Foundation case study committee was formed to address this need. Since its inception in 2011, 14 freely downloadable case studies have thus far been jointly developed by an academics and industry practitioners to help educators elicit varied responses from students about potential ways to respond when facing an actual project dilemma. AGC case studies are typically designed to focus on a particular concern and topics have thus far included: ethics, site logistics planning, financial management, prefabrication and modularization, safety, lean practices, preconstruction planning, subcontractor management, collaborative teamwork, sustainable construction, mobile technology, and building information modeling (BIM). This session will include an overview of the history and intent of the AGC case study program, as well as lively interactive demonstrations and discussions on how case studies can be used both by educators within a typical academic setting, as well as by industry practitioners seeking a novel tool for their in-house training programs.