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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Microelectronics Device Inspection System Implementation and Modeling for Flip Chips and Multi-Layer Ceramic Capacitors

Erdahl, Dathan S. (Dathan Shane) 15 April 2005 (has links)
Increased demand for smaller electronics is driving the electronic packaging industry to develop smaller, more efficient component level packages. Surface mounted components, such as flip chips, ball grid arrays (BGAs), and chip-scale packages (CSPs), are being developed for use in high-volume production. All of these technologies use solder bumps to attach the active silicon to the substrate, and traditional nondestructive methods such as machine vision, acoustic microscopy or x-ray inspection cannot easily find solder bump defects. Therefore, a system, consisting of an Nd:YAG laser that delivers pulses of infrared energy to the surface of the chip, a laser interferometer to record surface vibrations, and a high-speed data acquisition system to record the signals, was developed. The pulsed laser generates ultrasound on the chips surface, exciting the whole chip into a vibration motion, and the interferometer measures the vibration displacement of the chips surface at several points. Changes in the quality of the device or its attachment to the board produce changes in the free vibration response. Characterization of the differences between good devices and devices with defects, both in time domain and frequency domain, is performed using signal analysis. The system has inspected flip chips and chip scale packages for missing and misaligned solder balls, but to characterize the resolution of the system for open solder joints, a study of the vibration modes excited by the laser source in a flip chip was performed on specimens with intentionally created defects. Experimental measurements of excited modes were compared with a modal analysis model created in ANSYS, and defects were detected as small changes in the mode shape on the surface of the chips. Current inspection methods have also been inadequate for inspecting multi-layer ceramic capacitors (MLCCs). Flex cracks, caused by manufacturing processes, often cause the capacitors to fail in-service. Samples that have been cracked intentionally were compared with reference samples to determine the feasibility of using this technique to monitor the condition of MLCCs on an assembly line. Currently, there is no on-line inspection method for controlling this problem, but this technique was able to differentiate between good and damaged capacitors.
52

Analysis of Davit Structure with a Telescopic Arm of a Ship

Chen, Hong-long 20 July 2007 (has links)
Abstract Maritime transportation is important to national development because of Taiwan is in surrounding seas region. Therefore it is necessary that this research aimed to safety of the crane transportation system. This research investigated davit structure with a telescopic arm of a ship by means of the static analysis and modal analysis. To achieve the purpose, the researcher used the computer-aided design software Solidworks to set up this structure model. After that, he used finite element analysis software ANSYS to analyze the data. This research simulated in three situations. In static analysis, the researcher found the maximum displacement, the maximum von Mises stress and factors for safety of the structure in 16 dimensional sets in 53¢X of inclination at the davit with the telescopic arm being the shortest. After that, he discussed its tendency situation. In addition, he also checked the original structure in 53¢X of inclination at the davit with the telescopic arm being the longest and horizontal at the davit with the telescopic arm being the longest, respectively. In modal analysis, the researcher found natural frequencies and vibration shapes of the original structure. The structure had good vibration-proof ability and the resonance effect possibility not to be high. Generally, the researcher hoped that this study could provide helpful references for the relevant davit structure designers in the future.
53

脊柱力学模型による特発性側彎症の成因解明

笹岡, 竜, SASAOKA, Ryu, 畔上, 秀幸, AZEGAMI, Hideyuki, 川上, 紀明, KAWAKAMI, Noriaki 01 1900 (has links)
No description available.
54

Attitude control of flexible structures

Ward, Christina C. January 1990 (has links) (PDF)
Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Agrawal, Brij N. Second Reader: Titus, Harold. "September 1990." Description based on title screen as viewed on December 17, 2009. DTIC Identifier(s): Attitude Control Systems, Flexible Structures, Spacecraft, Structural Response, Resonant Frequency, Experimental Design, Model Tests, Active Control, Gifts Computer Program, Dynamic Response, Computerized Simulation, Control Theory, Modal Analysis, Laboratory Tests, Theses. Author(s) subject terms: Attitude Control, Flexible Structures. Includes bibliographical references (p. 52). Also available in print.
55

Modal analysis of long wave equations

Socha, Katherine Sue 28 August 2008 (has links)
Not available / text
56

Frequency response computation for complex structures with damping and acoustic fluid

Kim, Chang-wan, 1969- 01 August 2011 (has links)
Not available / text
57

Multiple-Input Multiple-Output (MIMO) blind system identification for operational modal analysis using the Mean Differential Cepstrum (MDC)

Chia, Wee Lee, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2007 (has links)
The convenience of Operational Modal Analysis (OMA), over conventional Experimental Modal Analysis (EMA), has seen to its increasing popularity over the last decade for the purpose of evaluating dynamic properties of structures. OMA features an advantage of requiring only output information, which is in tandem with its main drawback of lacking scaled modeshape information. While correctly scaled modeshapes can be assumed under a restrictive assumption of spectrally white inputs, in reality, input spectra are at best broadband in nature. In this thesis, an OMA method for Multiple-Input Multiple-Output (MIMO) applications in mechanical structures is developed. The aim is to separate MIMO responses into a collection of Single-Input Single-Output (SISO) processes (matrix FRF) using cepstral-based methods, under less restrictive and hence more realistic coloured broadband excitation. Existing cepstral curve-fitting techniques can be subsequently applied to give regenerated FRFs with correct relative scaling. This cepstral-based method is based on the matrix Mean Differential Cepstrum (MDC) and operates in the frequency domain. Application of the matrix MDC onto MIMO responses leads to a matrix differential equation which together with the use of finite differences, directly solves or identifies the matrix FRF in a propagative manner. An alternative approach based on whitened MIMO responses can be similarly formulated for the indirect solution of the matrix FRF. Both the direct and indirect approaches can be modified with a Taylor series approximation to give a total of four propagative solution sequences. The method is developed using relatively simple simulated and experimental systems, involving both impulsive and burst random excitations. Detailed analysis of the results is performed using more complicated Single-Input Multiple-Output (SIMO) and MIMO systems, involving both driving and non-driving point measurements. The use of the matrix MDC method together with existing cepstral curve-fitting technique to give correct relative scaling is demonstrated on a simulated MIMO system with coloured inputs. Accurate representation of the actual FRFs is achieved by the matrix MDC technique for SIMO set-ups. In MIMO scenarios, excellent identification was obtained for the case of simulated impulsive input while the experimental and burst random input cases were less favourable. The results show that the matrix MDC technique works in MIMO scenarios, but possible noise-related issues need to be addressed in both experimental and burst random input cases for a more satisfactory identification outcome.
58

Optimization of model analysis and cross-orthogonality techniques to insure finite element model correlation to test data /

Miller, Carlton, W. January 1993 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 1993. / Includes bibliographical references (leaves 80-87).
59

Non-linear vibration control of long, flexible structures employing inter-modal energy transfer [modal damping]

May, James E. January 2009 (has links)
Dissertation (Ph. D.)--University of Akron, Dept. of Civil Engineering, 2009. / "August, 2009." Title from electronic dissertation title page (viewed 9/16/2009) Advisor, Craig C. Menzemer; Committee members, Wieslaw Binienda, Robert Liang, D. Dane Quinn, Kevin L. Kreider; Department Chair, Wieslaw Binienda; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
60

Application of sensors in an experimental investigation of mode dampings /

Berg, Richard Hiram. January 1993 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references (leaves 100-102).

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