• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.448-455
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• 1996

In this study, to reduce vibration of step motor we use Microstep control. Microstep control of stepmotor is usually thought of as an extension of conventional stepmotor control technology. The essence ofmicro stepping is that we divide the full step of a stepmotor into a number of substep called microstep and cause the stepmotor to move through a substep per input pulse. In ideal case, bycontrolling the individual phase currents of a two-phase step motor sinusoidally we can get uniform torque and step angles. But due to the monlinear characteristics of the step motor, we need to compensate current waveform to improve the overall smoothness of the conventional micro stepping system. We implement digital Pulse Width Modulation(PWM) driver to drive step motor and microphone was used for detecting vibration. Driver enables speed change automatically byincreasing or decreasing micro stepping ratio which we call Automatic Switching on the Fly. To compensate the torque harmonics, Neural Networks is applied to the system and we foundcompensated optimal input current waveform. Finally we can get smooth motion of step motor in a wide range of motor speed.

• 무역상무연구
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• 제13권
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• pp.283-302
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• 2000

The firms aim to acquire services and costs advantage from logistics outsourcing strategy. But it is very important to select optimum service provider. A checklist of the criteria for the evaluation of service providers follows : service quality, low cost, logistics information system, service network, financial stability, investments in plant and equipment, management attitude and lookout for the future strategic fit, cultural and psychological barriers etc. Also, a 8-step implement of logistics outsourcing strategy will be of help for maximizing benefits of logistics outsourcing. It follows : 1-step : logistics environment analysis, 2-step : check service provider availability, 3-step : logistics outsourcing determinant analysis, 4-step : select of optimum service provider, 5-step : contract with optimum service provider, 6-step : identify of remaining barriers, 7-step : performance of logistics outsourcing, 8-step : evaluation.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1712-1717
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• 1997

Stability and accuracy for the trapezoidal rule of the Newmark time integration method are analyzed when variable time step sizes are adopted. A new analytic approach to stability and accuracy analysis is also proposed for time integration methods with variable time step sizes. The trapezoidal rule with variable time step sizes has the "actual" unconditional stability which is the same as that of the method with constant time step sizes. However, the method with variable time step sizes is first-order accurate while the method with constant time step sizes is second-order accurate. accurate.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.190-200
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• 1996

Step-by-step time integration methods are widely used for solving structural dynamics problem. One difficult yet critical choice an analyst must make is to decide an appropriate time step size. The choice of time step size has a significant effect on solution accuracy and computational expense. The objective of this research is to derive error estimate for newly developed time integration method and develop automatic time step size control algorithm for structural dynamics. A formula for computing error tolerance is derived based on desired period resolution. An automatic time step size control strategy is proposed based on a normalized local error estimate for the generalized-α method. Numerical examples demonstrate the developed strategy satisfies general design criteria for time step size control algorithm for dynamic problem.

• 한국CDE학회논문집
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• 제9권2호
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• pp.175-182
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• 2004

As a bridge between design and manufacturing, process planning is to generate a sequenced set of instructions to manufacture the specified part. Automatic interpretation of manufacturing information incorporated in the design documentation such as CAD file has been a knotty subject for manufacturing engineers since no current data exchange format for product data provides a perfect interface between heterogeneous systems. The recent neutral data exchange format STEp, standard for the exchange of product model data, includes not only geometry but also technical and managerial information. STEP AP(Application Protocol) 224 is specifically dedicated to the mechanical product definition for process planning using machining features. Given a design information in STEP AP 224 format, process planning can be made without human intervention. This paper describes a method to determine the sequence of machining features by using the machining features and the manufacturing information expressed in STEP AP224.

• 한국전자거래학회지
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• 제9권3호
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• pp.57-77
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• 2004

본 연구의 목적은 건설도면정보 공유를 위한 XML 스키마 개발 및 STEP 연계기술을 개발하는 것이다. 이를 위해 STEP/AP202를 바탕으로 도면정보를 표현하는 STEP 데이터 모델 개발, ISO 표준도면을 관리할 수 있는 STEP 데이터 검색기 개발, 그리고 벡터형식으로 표현되는 도형정보와 각 도형요소가 연관되는 외부적 기술 자료들이 상호 유기적으로 통합될 수 있는 구조를 지원하기 위한 XML 스키마를 개발하였으며, 자재정보와 법규체크를 대상으로 STEP과 XML의 상호 연계를 통한 도면정보 공유방안을 제시하였다. 따라서 제안된 건설도면정보 공유방안을 통해 건설산업 전반에서 발생하는 건설도면을 포함한 각종 외부문서, 기술문서들의 상호 연계로 건설설계 업무지원 및 정보의 최적화된 관리가 가능할 것이다.

• 수산해양기술연구
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• 제41권3호
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• pp.199-206
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• 2005

As the basic study about improvement of yellow croaker drift gill net fishing implement and development of the fishing system, this study drew problem after synthetically analyzing hauling system of yellow croaker drift gill net used in the coast of Chuja Island and tested several characters and analyzed in hauling process with 5 step net hauler model for improving the problem. The analysis results are as follows. When the angle between axises of drum centers was small, it showed the tendency that hauling time was fast. Hauling time was faster when drum was 5 step rather than 3 step. When drum was 5 step, slippery phenomenon was small and hauling was stable. Tension was larger when drum was 5 step rather than 3 step. When drum was 5 step, the range of change of the maximum and minimum value was small and hauling was stable. When drum was 3 step, there was following formula between hauling time ($Ht_3$) and angle between axises of drum centers ($A_g$) $Ht_3$ : ($7.15Hs^{-0.81}$) $A_g^{-0.81}$, when drum was 5 step there was following formula.$Ht_5$ : ($6.45Hs^{-0.75}$) $A_g0.10$, here, Hs is hauling speed. When drum was 3 step and hauling speed was 28cm/sec, tension was $T=0.08A_8^3-1.60A_g^3-0.49A_g+369.56(r=0.99)$, when drum was 5 step, tension was, $T=-0.01A_g^3+1.96A_g^2-34.05A_g+414.58$ (r-0.99), here, T was tension(g).

• 한국컴퓨터그래픽스학회논문지
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• 제2권2호
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• pp.69-74
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• 1996

최근 점점 통합되는 세계시장과 증가하는 경쟁에서 살아남기 위해 시간과 공간의 제약을 받지 않고 제품정보를 공유할 수 있는 기술의 확보가 요구되고 있다. 제품정보의 공유를 위한 방안으로 제품정보를 중립형태의 표준으로 표현해 네트워크를 통해 전송하는 방법이 있다. 본 논문에서는 인터넷상에서 STEP 물리적 파일의 3차원 형상정보를 가시화하는 방법을 소개한다. 제품정보의 국제표준으로 새롭게 제시되는 STEP에서 형상정보가 어떻게 표현되는지 알아보고, 인터넷 환경에서의 프로그래밍 언어인 자바와 3차원 데이터 포맷인 VRML을 이용하여 형상정보를 가시화한 후 각각의 장단점을 파악하여, STEP 모델 가시화 기술을 자동차 PDM에 적용해 본다.

• 한국운동역학회지
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• 제16권4호
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• pp.31-38
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• 2006

The purpose of this study was to investigate the effect of changing the steps height on the joint moment of lower extremity in stair-descent activity of elderly persons. Data were collected by 3-D cinematography and force platform. 9 male elderly subjects in the 60s and 70s participated in this study. All subjects performed a stair-descent in four different heights of stairs (10, 14, 18, 22cm) having 5 step staircase. The results were as follows. 1. For the step height of 22cm the maximum. plantarflexion moment was the smallest and the largest for the step height of 14cm. 2. There was not a statistical difference shown for the extension moment of the knee joint for the different height of steps. 3. There was not a statistical difference shown for the flexion moment of the hip joint for the varying height of steps but on average for the 18cm step this increased rapidly. 4. The smallest maximum. value for inversion moment was revealed for the step height of 10cm and this increased significantly for the step height of 22cm. 5. The smallest maximum. value for abduction moment of the hip joint was revealed for the step height of 10cm and this increased significantly for the step height of 22cm. 6. There was no significant difference shown for the maximum. abduction moment for the hip joint. The main conclusion is that there is a huge difference in the moment of the lower extremities for the elderly while walking down a stairs with a step height above 18 cm and that this moment increased or decreased rapidly under a condition of step height being 22cm. With the results from this research and related research of elderly walking upstairs it can be shown that the step height has a large role in the safety for the elderly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.313-315
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• 2005

In a power system, an out-of-step condition causes a variety of risk such as serious damage to system elements, tripping of loads and generators, mal-operation of relays, etc. Therefore, it is very important to detect the out-of-step condition and take a proper measure. Several out-of-step detection methods have been employed in relays until now Mo,;t common method used for an out-of-step detection is based on the transition time through the blocking impedance area in R-X diagram. Also, the R-R dot out-of- step relay, the out-of-step prediction method and the adaptive out-of-step relay using the equal area criterion (EAC) and Global Positioning Satellite (GPS) technology have been developed. This paper presents the out-of-step detection algorithm using the time variation of the complex power. The complex power is calculated and the mechanical power of the generator is estimated by using the electrical power, and then the out-of-step detection algorithm, which is based on the complex Power and the estimated mechanical power, is presented. This algorithm, may detect the instant when the generator angle passes the Unstable Equilibrium Point (UEP). The proposed out-of-step algorithm is verified and tested by using Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP) MODELS.