• 공학교육연구
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• 제16권2호
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• pp.24-30
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• 2013

This paper deals with the measurement theory and technique of linear expansion coefficient for solid material using Michelson interferometer. The Michelson interferometer produces interference fringes by splitting a beam of monochromatic light so that one beam strikes a fixed mirror and the other a movable mirror. When the reflected beams are brought back together, an interference pattern results. Precise distance measurements until a quarter of wave length can be made with the Michelson interferometer by moving the mirror and counting the interference fringes which move by a photo diode. This paper represents the application of Michelson interferometer for measuring infinitesimal length system and shows the measurement method of linear expansion coefficients for various materials like copper, aluminum and iron. the results are good agreement with theoretical value within margin of error for each materials.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.47-50
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• 2000

In the Multirate DS/CDMA system based on VSL(Variable Spreading Length), the problem of the multiple access interference and effect similar to near-far effects in current system is generated. This problem can degrade performance of the system badly. Therefore, In this paper we proposed Hybrid Interference Cancellation to overcome this problems, Simulation result presents that the proposed Hybrid Interference Cancellation has the better performance than the conventional decorrelator, Parallel Interference Cancellation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.795-800
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• 2000

In a parallel manipulator, there are three constraints that determine workspace: link length constraint, passive joint angle constraint, and interference among links. Generally, the link length constraint is the most dominant. The interference among links is, however, also an important parameter in designing a desired parallel manipulator. In this study, the interference among links is mathematically modeled by considering the links as a line and a cylinder of radius of twice the link radius, and a new algorithm is suggested to check if arbitrary two links interfere each other or not. The workspace of a cubic parallel manipulator is illustrated in a 2D space satisfying the three constraints.

• 대한기계학회논문집
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• 제16권12호
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• pp.2261-2267
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• 1992

본 연구에서는 시일 립의 간섭량과 접촉력에 관련된 이론적 연구를 수행한다. 시일의 접촉면에서 축방향 접촉력이 크게 설계되면 시일 립 선단에서는 마찰과 마멸이 심하게 진행되어 시일수명을 크게 단출시킬 우려가 있고, 접촉력이 작으면 밀봉된 유 체의 누설유려가 증가되면서 볼과 레이스사이의 윤활상태를 나쁘게 하여 베어링 수명 을 크게 단축하는 결과를 초래하게 되므로 시일 립의 접촉력에 관련된 연구는 대단히 중요하다.

• 한국통신학회논문지
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• 제22권7호
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• pp.1559-1565
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• 1997

A new multitrack RLL codes with immunity to intertrack interference (ITI) is proposed. This code takes aim at a high density storage channels by reducing the track width and/or guard bands between tracks since it prevents transition in neighboring tracks at the same time epoch. The capacities of the codes are found for each maximum and minimum constraint pair.

• 한국정밀공학회지
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• 제14권10호
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• pp.151-156
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• 1997

A laser measurement system, a modified Michelson interferometer, which can accurately measure high speed length and displacement of servomechanisms by detecting a phase shift in the measurement beam using an optical interference was developed. A frequency stabilized laser source and a 20 fold frequency interpolation and digitizing circuit were applied to the system. The refra- ctive index of the ambient air was calibrated through the Edlens formula. The system achieved a resolution of /40, 16nm, a maximum allow-able measurement speed of 600nm/sec, and a length measure- ment range of 1500 mm. Performance of the system was evaluated on the machining center in short and long length measurements.

• 한국산업정보학회논문지
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• 제19권2호
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• pp.1-13
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• 2014

In IEEE 802.11p/1609-based vehicular networks, vehicles are allowed to exchange safety and control messages only within time periods, called control channel (CCH) interval, which are scheduled periodically. Currently, the length of the CCH interval is set to the fixed value (i.e. 50ms). However, the fixed-length intervals cannot be effective for dynamically changing traffic load. Hence, some protocols have been recently proposed to support variable-length CCH intervals in order to improve channel utilization. In existing protocols, the CCH interval is subdivided into safety and non-safety intervals, and the length of each interval is dynamically adjusted to accommodate the estimated traffic load. However, they do not consider the presence of hidden nodes. Consequently, messages transmitted in each interval are likely to overlap with simultaneous transmissions (i.e. interference) from hidden nodes. Particularly, life-critical safety messages which are exchanged within the safety interval can be unreliably delivered due to such interference, which deteriorates QoS of safety applications such as cooperative collision warning. In this paper, we therefore propose a new interference-aware Dynamic Safety Interval (DSI) protocol. DSI calculates the number of vehicles sharing the channel with the consideration of hidden nodes. The safety interval is derived based on the measured number of vehicles. From simulation study using the ns-2, we verified that DSI outperforms the existing protocols in terms of various metrics such as broadcast delivery ration, collision probability and safety message delay.

• 한국전자통신학회논문지
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• 제13권5호
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• pp.917-922
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• 2018

기존의 채널간간섭 자기소거법에서는 표본화창의 길이를 직교 주파수분할다중화의 심볼 길이와 동일하게 정하였다. 이로 인하여 각 부채널의 간섭계수를 구하기 위한 복소연산량이 급격이 증가된다. 이러한 문제점을 해결하기 위하여 본 논문에서는 채널간간섭 자기소거법에서 나타나는 간섭계수에 대한 근사식을 제시한다. 또한, 제시된 근사식을 기반으로 표본화창의 길이를 제한시킬 때 간섭계수의 평균자승오차와 복소연산량을 분석하였다. 그 결과, 제시된 근사식은 원식에 비하여 평균자승오차 면에서 0.01% 미만의 오차를 가지는 것으로 나타났다. 이에 비하여 부채널의 수가 1024인 경우 간섭계수 계산을 위한 연산량은 98% 이상 감소되는 것을 확인하였다. 따라서 제시된 근사식은 자기소거 능력은 거의 변화시키지 않으면서도 연산량을 현저히 감소시킬 수 있으므로 채널간간섭 자기소거법 알고리즘 개발에 유용하게 활용될 수 있을 것으로 기대된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.95-98
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• 2003

The physics of the plume-induced shock and separation particulary at a high plume to exit pressure ratio and supersonic speeds up to Mach 3.0 with aid without a passive control method, porous extension, were studied using computational techniques. Mass-averaged Navier-Stokes equations with the RNG k-$\varepsilon$ turbulence model were solved using a fully implicit finite volume scheme and a 4-stage Runge-Kutta method. The courol methodology for plume-afterbody interactions is to use a perforated wall attached at either the nozzle exit or the edge of the missile base. The Effect of porous wall length on plume interference is also investigated. The computational results show the main effect of the porous extension on plume-afterbody interactions is to in the plume from strongly underexpanding during a change in flight conditions. With control, a change in porous extension length has no significant effect on plume interference.

• 조명전기설비학회논문지
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• 제25권12호
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• pp.107-112
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• 2011

Multiple ground rods are commonly used to obtain the low ground impedance, but they will not reduce the ground impedance unless the spacings between the ground rods are sufficient. This paper presents the experimental results of frequency-dependent resultant ground impedance of two ground rods in parallel. The resultant ground impedance of two ground rods in parallel were measured as functions of the spacing and length of ground rods and the frequency of test currents and were discussed based on the potential interferences. As a consequence, the frequency-dependent ground impedance of single ground rod and two combined ground rods give capacitive. It was found that the effect of potential interference on the ground impedance is directly associated with the frequency-dependent ground impedance and is strong in low frequency. Also, in order to reduce the increasing rate of resultant ground impedance of two ground rods due to potential interference to within 10(%), two ground rods in parallel will be placed over one rod length apart.