• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1066
  • 286
  • 169
  • 143
  • 109
  • 49
  • 44
  • 37
  • 23
  • 18
  • 15
  • 15
  • 9
  • 7
  • 7
  • Tagged with
  • 2475
  • 332
  • 207
  • 203
  • 200
  • 191
  • 172
  • 161
  • 157
  • 147
  • 131
  • 129
  • 129
  • 127
  • 123
  • 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.
81

An investigation of multi-layer integrated passive structures for application as three-phase EMI filters

De Jager, Kylie 15 May 2008 (has links)
The advent of the integration of discrete passive components is a direct result of the drive towards the minimisation of power electronic converters and filters. To this end Integrated Power Passive Modules (IPPMs) have been utilised in the past. The IPPMs discussed in this dissertation refer to structures consisting of dielectric layers sandwiched between layers of conductive material. The use of these types of structures in various applications has been well documented. However, the applications have been single-phase in nature and the exact configuration of the IPPMs has been largely dependent on the designers’ past experience with the modules. The development of a synthesis procedure to identify the required configuration for any particular application would be of great benefit to designers. The foundation of such a synthesis procedure was laid through an exhaustive search of all possible configurations that can be realised with a three conductive layer IPPM. From this exhaustive search a number of general trends, between the configurations and their associated frequency response, were observed. Furthermore, a number of principles underlying the functionality of the configurations were highlighted during the course of the exhaustive search. The validity of some of these results was experimentally investigated through the design and implementation of an integrated EMI filter. The EMI filter considered in this study differed from integrated EMI filters, previously reported on, through the fact that the filter considered herein was to be implemented in a three-phase application. To this end a set of configurations that realise low pass filters were identified from the results of the exhaustive search. The application of these configurations was expanded from single-phase to three-phase by mapping the configurations onto a building block component used to realise the three-phase application. Simulations of these three-phase filters were used to analyse the filter performance. From this analysis a subset of configurations were identified as displaying the best performance characteristics. The configurations within this subset were further analysed using the results of the exhaustive search. In so doing two configurations were isolated for use in a practical realisation of the three-phase filters. The physical design and construction of the integrated three-phase filters, as well as the test bench, was considered. The performance of the filters was investigated through comparative measurements of common mode and differential mode currents, in the test bench, in the presence and absence of the filters. From this investigation significant reduction in the conducted EMI noise was seen through the introduction of the filters into the system. / Dr. I. W. Hofsajer
82

Notch Filter Design for Power Line Interference Artifact Reduction of ECG Signal and Feature Extraction in LabVIEW

Kasidi, Divyasri 05 1900 (has links)
Electrocardiogram (ECG) is a biological signal that represents the heart's electrical activity. Interference from power lines introduces a frequency component of 50 to 60 Hz into the signal, which is the principal cause of ECG corruption. By using the Cadence Virtuoso Spectre circuit simulator and typical TSMC RF 180 nm CMOS technology, a notch filter was created to reduce powerline interference. The advantage of utilizing a notch filter for PLI is that noise at 60 Hz is completely eliminated without sacrificing any important information. Additionally, this study contains a MATLAB-based model for, which is used to compute the power spectral density for the obtained time-domain signal. By incorporating power spectral density into data gathering procedures, it is feasible to enhance data collection methodologies, construct models that appropriately account for observed power and aid in the removal of undesired components. NI LabVIEW is used to extract features. The advantage of ECG feature extraction is that it provides information that assists in the identification of cardiac rhythm issues, and gives information about the occurrence of heart attack. In this study, several patient data sets are utilized to extract characteristics and provide information regarding heart condition abnormalities.
83

Digital Holographic Microscopy of Microparticles

Alotibi, Satam Fahad 06 May 2017 (has links)
Digital holography is a method for recording holograms through the use of an optoelectronic sensor, which serves as a replacement for the use of film [1]. Through the use of coherent light, the microparticles’s characterization can be observed with this method. Yet even using partially coherent light, images of particles can be formed revealing particle shape and size at scales larger than 10 micrometers. For example, ragweed pollen sporeclusters and glass microspheres are investigated here. The holographic images results are compared with conventional optical microscope images for validation.
84

Analysis and design of enclosures for electromagnetic suscepibility measurements over a wide frequency range (20MHz-30GHz)

Mishra, Shantnu R. January 1982 (has links)
No description available.
85

Junction theories of photoelectric effects at dye-semiconductor interfaces /

Ferrier, Jack Moreland January 1973 (has links)
No description available.
86

The Rise in Prices: Is Artificial Interference ever Justifiable?

Lang, Harold 05 1900 (has links)
N/A / Thesis / Master of Business Administration (MBA)
87

Assessment of RANS Turbulence Models for Strut-Wing Junctions

Knight, Kyle Cohn Davis 17 May 2011 (has links)
Multidisciplinary Design Optimization (MDO) studies show the Strut/Truss Braced Wing (SBW/TBW) concept has the potential to save a significant amount of fuel over conventional designs. For the SBW/TBW concept to achieve these reductions, the interference drag at the wing strut juncture must be small compared to other drag sources. Computational Fluid Dynamics (CFD) studies have concluded the interference drag is small enough for the TBW concept to be practical. However, the turbulence models used in these studies have not been validated for transonic, high Reynolds number, junction flows. This study intends to assess turbulence models by comparing drag and surface streamlines obtained from experiment and CFD. The test model is a NACA 0012 fin at Mach number of 0.75 and a Reynolds number of 6 million with varying angle of attack. The CFD analysis includes both the fin and tunnel test section. The main turbulence model tested is the k-w Shear Stress Transport model. The fin is tested at different Mach numbers and inlet conditions to account for experimental variations. The study shows the CFD over predicts separation. The reasons for this discrepancy is likely the turbulence models employed. / Master of Science
88

STUDY ON GPS RECEIVER ALGORITHMS FOR SUPPRESSION OF NARROWBAND INTERFERENCE

Yongkang, Hu, Qishan, Zhang, Yanhong, Kou, Dongkai, Yang 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Despite the inherent resistance to narrowband signal interference afforded by GPS spread spectrum modulation, the low level of GPS signals makes them susceptible to narrowband interference. This paper discusses the application of a pre-correlation adaptive temporal filter for stationary and nonstationary narrowband interference suppression. Various adaptive algorithms are studied and implemented. Comparison of the convergence and tracking behavior of various algorithms is made.
89

An Interference Cancellation Scheme for Carrier Frequency Offsets Compensation in the Uplink of OFDMA systems

Wang, Sen-Hung 20 August 2006 (has links)
A successive interference cancellation (SIC) structure is proposed for multiuser interference cancellation (MUI) due to carrier frequency offsets (CFOs) in the uplink of orthogonal frequency division multiple access (OFDMA) systems. The proposed architecture adopts a circular convolution to suppress the impacts caused by CFOs. This paper demonstrates that, with 2 iterations, the SIC has better performance than that of the parallel interference cancellation (PIC), but system complexity is only 1/2K, where K is the number of users in the uplink of OFDMA system. This study also shows that system complexity can be significantly reduced if proper approximation is made.
90

Performance Analysis for WRANs

Zhang, Zhuang-wei 12 February 2009 (has links)
none

Page generated in 0.0632 seconds