• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.127-131
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• 2000

The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of an interface crack. This paper investigates determined the effects of the hole (existed on the path of the crack propagation) on the crack propagation behavior by comparing the experiment isochromatic fringes to the theoretical stress fields.

• ETRI Journal
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• 제28권2호
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• pp.247-249
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• 2006

In the development of a new wireless communications system, a versatile and accurate radio channel for indoor communications is needed. In particular, the investigation of radio transmission into buildings is very important. In this letter, we present an improved three-dimensional electromagnetic wave propagation prediction model for indoor wireless communications that takes into consideration building penetration loss. A ray tracing technique based on an image method is also employed in this study. Three-dimensional models can predict any complex indoor environment composed of arbitrarily shaped walls. A speed-up algorithm, which is a modified deterministic ray tube method, is also introduced for efficient prediction and computation.

• 대한조선학회지
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• 제21권3호
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• pp.27-34
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• 1984

When a ship is travelling in following seas, the encounter frequency is reduced to be very low. In that case broaching phenomenon is most likely to occur, and it may be due to wave exciting forces acting on ships. It is thought that the wave exciting forces acting on ships in following seas almost consist of two components. One is hydrostatic force due to Froude-Krylov hypothesis, and the other is hydrodynamic lift force due to orbital motion of water particles below the wave surface. In the present paper, the emphasis is laid upon wave exciting sway force, yaw moment and roll moment acting on ships in following seas. The authers take the case that the component of ship speed in the direction of wave propagation is equal to the wave celerity, i.e., the encounter frequency is zero. Hydrostatic force components are calculated by line integral method on Lewis form plane, and hydrodynamic lift components are calculated by lifting surface theory. Furthermore captive model tests are carried out in regular following waves generated by means of a wave making board. Through the comparison between calculated and measured values, it is confirmed that the wave exciting forces acting on ships in following seas can be predicted in terms of present method to a certain extent.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.334-339
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• 2002

In this report, numerical investigations have demonstrated, that the displacement underneath a moving loading reach a maximum value, if the speed of the load is equal to propagation velocity of the maximum wave. The load speed for which the maximum displacement occurs is called critical speed. The critical speed divides the velocities in a subcritical and a super-critical region. By means of calculations the dynamic behaviour of the slab track-soil is investigated. For concrete slab track dynamic wheel load are given in dependence of relevant excitation mechanismen and speed of the train. These loads can be used for the dimensioning of the track as well as for prognosis of the vibrations at the track and the surrounding soil.

• 한국철도학회논문집
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• 제8권2호
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• pp.116-121
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• 2005

In this report, numerical investigations have demonstrated, that the displacement underneath a moving loading reach a maximum value, if the speed of the load is equal to propagation velocity of the maximum wave. The load speed for which the maximum displacement occurs is called critical speed. The critical speed divides the velocities in a subcritical and a super-critical region. By means of calculations the dynamic behaviour of the slab track-soil is investigated. For concrete slab track dynamic wheel load are given in dependence of relevant excitation mechanismen and speed of the train. These loads can be used for the dimensioning of the track as well as far the prognosis of the vibrations at the track and the surrounding soil.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.91-96
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• 2003

In this report, numerical investigations have demonstrated, that the displacement underneath a moving loa야ng reach a maximum value, if the speed of the load is equal to propagation velocity of the maximum wave. The load speed for which the maximum displacement occurs is called critical speed. The critical speed divides the velocities in a subcritical and a super-critical region. By means of calculations the dynamic behaviour of the slab track-soil is investigated. For concrete slab track dynamic wheel load are given in dependence of relevant excitation mechanism and speed of the train. These loads can be used for the dimensioning of the track as well as for the prognosis of the vibrations at the track and the surrounding soil.

• 한국해양학회지:바다
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• 제8권3호
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• pp.274-284
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• 2003

본 연구에서는 제 3세대 파랑 모형인 WAVEWATCH-III모델 (Tolman, 1999)과 기상청 해양기상 관측부이(4기) 자료를 이용하여 파랑인자 특성에 관한 분석이 이루어졌다. 풍속이 증가한 후 약 2-3시간 후에 유의파고가 커지고, 풍속과 유의파고의 상관성은 비교적 외해에 위치한 동해 부이에서 크게 나타났다. 육풍 발생 시 두 인자 사이의 상관계수 값이 급격히 떨어졌으며, 풍속과 파고 편차 시계열 자료에서는 동채부이를 제외하고 지배적인 조석주기가 발견되었다 부이 자료와의 비교를 통하여 WAVEWATCH-III모델의 파랑 모의 성능을 진단한 후에, 쿠로시오 해역과 동해 해역의 수치 실험을 통해서 파랑의 진행 방향에 대해 반대 방향으로 해류가 흐를 때는 파고는 높아지고, 파장은 짧아진다는 사실을 재확인했다. 또한 이러한 효과는 풍속이 약하거나 해류가 강할 때 더 커지는 양상을 나타냈으며 이에 대한 정량적인 결과를 제시하였다.

• Structural Engineering and Mechanics
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• 제25권5호
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• pp.597-611
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• 2007

Many works have been done in classical theory of thermoelasticity in materials with memory by researchers like Nunziato, Chen and Gurtine and many others. No work is located in generalized thermoelasticity regarding materials with memory till date. The present paper deals with the wave propagation in materials with memory in generalized thermoelasticity. Plane progressive waves and Rayleigh waves have been discussed in details. In the classical theory of heat conduction it was observed that heat propagates with infinite speed. This paradox has been removed in the present discussion. The set of governing equations has been developed in the present analysis. The results of wave velocity and attenuation coefficient corresponding to low and high frequency have been obtained. For thermal wave the results show appreciable differences with those in the usual thermoelasticity theory.

• 한국가시화정보학회지
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• 제11권1호
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• pp.22-27
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• 2013

An investigation into the influence of ultrasonic standing wave on the structural behavior of propane/air premixed flame has been made to get a clue to the combustion reaction acceleration and combustion instability. Visualization technique utilizing the Schlieren photography was employed for the observation of structural variation of the flame reaction zone. Evolutionary characteristics of the flame front were caught by the high-speed Schlieren image, through which local flame velocity of the moving front were analyzed in detail.

• 제어로봇시스템학회논문지
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• 제1권1호
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• pp.38-42
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• 1995

This paper presents a target scoring method using shock wave signals, which are generated from the supersonic speed of a projectile. The shock wave is detected from three acoustic sensors located in the target plane and the difference of the delay times are measured. The target coordinates are calculated from the effective propagation of velocity (EPV) and the delay times of the shock wave; and the EPV is from the projectile velocity and the delay time. With a comparison between the measurement result and the known coordinates, the accuracy and the usefulness of the proposed scheme is validated.