擴張 PASTd 알고리즘을 利用한 블라인드 多重 使用者 檢出

학위논문(석사)--서울대학교 대학원 :전기.컴퓨터공학부,2001.Maste

直接數列-符號分割多元接續 시스템을 위한 廣義線形 最小出力에너지 알고리즘

학위논문(박사)--서울대학교 대학원 :전기·컴퓨터공학부,2005.Docto

High Frequency Vibration Analysis of Arrayed Panel Structures Using a Ray Tracing Technique

본 논문에서는 2차원 구조물의 고주파수 대역 진동 해석을 위하여, 원형파를 기본으로 한 레이 추적 기법(RTM)의 특성에 관한 논의를 하였다. 발산되는 원형파를 묘사하는 레이튜브 개념을 사용하여, 연성경계에서 입사파, 전달파, 그리고 반사파가 경계조건을 만족하도록 관계식을 유도하였다. 제안된 레이 모델을 직렬 배열 연결 평판 구조물에 적응하였는데, 직렬로 배열된 2개의 연결된 평판, 3개 및 4개의 연결된 평판에 대한 해석 결과를 통계적 에너지 해석법(SEA) 및 파동 인텐시티 해석법(WIA)과 비교하여 보았다. 그 결과, SEA 보다 개선된 예측을 할 수 있으며, WIA와는 비슷한 예측 성능을 보임을 확인할 수 있었다. 또한, 제안된 RTM을 사용하면 진동 에너지와 진동 인텐시티의 대략적 공간 분포를 알 수 있는 장점이 있다. 제안된 RTM은 2차원 연성 구조물의 고주파수 진동 해석을 위한 유용한 기법으로써 쓰일 것으로 기대된다. In this paper, the characteristics of the ray tracing method (RTM) based on the cylindrical wave are discussed for the high frequency vibration analysis of two-dimensional structures. A ray tube describing the emanating cylindrical wave is used to derive the governing equation for incident reflected, and transmitted ray tubes which satisfies the condition at the coupled boundary. The suggested ray model is applied to panel array structures, and the predicted results for 2-panel, 3-panel, and 4-panel array structures are compared to those by Statistical energy analysis (SEA) and Wave intensity analysis(WIA). More enhanced prediction was obtained compared to the SEA, and similar prediction performance was observed to the WIA. Additionally, the RTM has a novel feature that it can estimate the spatially smoothed distribution of vibration energy and vibration intensity. It is expected that the present RTM can be used as one of the useful tools for the high frequency vibration analysis of two-dimensional coupled structures

점성을 가진 물질이 입혀진 원형평판으로부터의 음압복사

학위논문(박사) - 한국과학기술원 : 기계공학과, 1987.8, [ xx, 110 p. ]Sound radiation from the vibration of an elastic structure excited by impact forces is a fundamental problem in acoustics. The mechanism of sound radiation depends on the geometry and the nature of contact between the impinging objects. In general, the dynamic response of a plate by an impact forces can be divided into its forced and free vibrations. The forced response of the plate may be elastic deformation of its surface, and the free vibrations of the plate result in what is called "ringing" radiation. The increasing needs for reducing vibration and sound radiation in light weighted structural members such as aircraft and automobile components, have focused on the attenuation by employment of viscoelastic coating, as a possible solution for this problem. The flexural vibration characteristics of a composite plate consisting of one or two outer layers of a linear viscoelastic material bounded to an elastic core have been discussed because of their increasing application in various fields. Sound radiation from most mechanical systems results from various kinds of impact forces. In this paper, the transient sound radiation from the impact on the clamped circular plate with viscoelastic layers is studied both analytically and experimentally. First, the contact force applied during the collision between an elastic sphere and a composite plate is obtained by Hertz contact theory. The composite plate vibrations are obtained by using the Laplace transform, the convolution theorem, the normal mode analysis and the eigenvalues that are obtained by a Mindlin plate theory. In the classical plate theory the effects of rotary inertia and shear deformation are neglected, while in the Timoshenko-Mindlin plate theory these effects are included. The radiated sound pressure is calculated by the Rayleigh integral in the farfield. Prediction of the waveforms of sound radiating from the plate with attached layers and a method for reducing noise generation from the plate by impac...한국과학기술원 : 기계공학과