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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.
431

Mechanical Fatigue And Life Estimation Analysis Of Printed Circuit Board Components

Genc, Cem 01 August 2006 (has links) (PDF)
In this thesis, vibration induced fatigue life analysis of axial leaded Tantalum &amp / Aluminum capacitors, PDIP and SM capacitors mounted on the printed circuit boards are performed. This approach requires the finite element model, material properties and dynamic characteristics of the PCB. The young modulus of the PCB material is obtained from 3 point bending tests, resonance frequencies are obtained from modal tests and transmissibility&amp / #8217 / s of the PCB are obtained from transmissibility tests which are used as fatigue analysis inputs. Step Stress Tests are performed to obtain failure times of the tested electronic components which are also used as the numerical fatigue analysis inputs. Consecutively, fatigue analysis of a sample PCB used in military systems is aimed since it is important to compare the calculated fatigue damage to estimated life limits in order to determine which component(s), if necessary, must be moved to positions of lower damage . For this purpose, power PCB of the power distribution unit used in Leopard 1 battle tank is examined. Numerical fatigue analysis coupled with accelerated life test whose profile is convenient to military platforms is performed. Furthermore, the effects of eccobond and silicone on the fatigue life of the components are also surveyed since these techniques are common in electronic packaging. In addition, mean-time-to-failure values are obtained for the tested components by using Weibull distribution. Finally, sensitivity analysis is performed to indicate the effect of certain parameters on the fatigue life of a sample axial leaded capacitor.
432

Catalytic Wet Air Oxidation of the High-concentration (COD) Wastewater Generated from the Printed Circuit Board Industry

Lin, Shyh-Liang 21 July 2000 (has links)
In this study, the wastewater generated from etching process of the Printed Circuit Board (PCB) was treated by a process including both acidification and coagulation/sedimentation and then followed by the catalytic wet air oxidation (CWAO) over different catalysts (either Pt/SiO2¡PAl2O3 or Pt¡PX/£^-Al2O3) process in series. Although the initial chemical oxygen demand (COD) concentration of the wastewater is as high as 7740-12700 mg/L, the effluent of the pretreatment process was measured to have COD value in ranges of 3050-4260 mg/L. Several re-action parameters, such as reaction temperatures (200-260¢J), oxygen partial pressures (0-3 MPa), and two kinds of catalysts were performed experimentally to investigate the COD reduction of the wastewater during the CWAO process. Both reaction temperature and variety of catalyst are found most effectively on the COD reduction. However, the effect of oxygen partial pressure on the COD reduction is just in little. Results showed that the COD reduction during the CWAO over the Pt¡PX/£^-Al2O3 catalyst process is the most significant, which with a tow-step re-action and both the two reactions do obey first-order reaction kinetics. A change from a higher reaction activity of the CWAO reaction to a slower one implies a decrease of the reaction rate. On basis of our experiments data, the effective operating conditions of CWAO for the COD reduction was observed to be at temperature of 260¢J under oxygen partial pressure of 2.0 MPa and at a retention time period of 60 min. The COD conversion was calculated as high as 75%; however, it could be enhanced up to 78% and 91%, respectively, when the CWAO was conducted in presence of the Pt/SiO2¡PAl2O3 and Pt¡PX/£^-Al2O3 catalysts, respectively. It can be seen that the organic compound of the wastewater was mineralized most completely (with a COD/TOC ratio of 3.7¡Ó0.2) after the CWAO over the Pt¡PX/£^-Al2O3 catalyst process. Furthermore, a higher COD/TOC ratio of 3.9¡Ó0.3 was achieved when the Pt/SiO2¡PAl2O3 catalyst was in presence of the CWAO process, and the primitive WAO process had the highest COD/TOC ratio of 4.8¡Ó0.4. The experimental data showed that both a higher reaction temperature (¡Ù260¢J) and an application of catalyst are more important factors for the min-eralization of the organic compound of the wastewater during the CWAO process. In our investigation, BOD5/COD ratio has been used to assess if the WAO and/or the CWAO process treatment yield products more amenable to biodegradation. The BOD5/COD ratio was 0.68-0.93 when the reaction temperature was above 220¢J and the retention time was as long as 60 min. Unfortunately, the BOD5/COD ratio of the effluent from the CWAO process came out a lower value (0.45-0.65) though it was under the same reaction conditions. It is probable that the biodegradable portion of the organic compounds of the wastewater were decomposed easier during the CWAO process than during the WAO process. In addition, it was found that the products of the wastewater was decomposed partially into CO2 and into some low molecular weigh acids, such as formic acid, acetic acid, propionic acid, etc. The activation energy with respect to COD was calculated to be 38.42 kJ/mole and 83 kJ/mole, respectively, for the first-step reaction and for the second-step reaction, respectively, of the WAO process. It was al-so calculated that the first-step reaction of the CWAO over the Pt/SiO2¡PAl2O3 catalyst process has activation energy of 18.25 kJ/mole and 25.76 kJ/mole is for the second-step reaction. However, 16.05 kJ/mole and 49.61 kJ/mole are calculated for the first-step and the sec-ond-step reactions, respectively, of the CWAO over the Pt¡PX/£^-Al2O3 catalyst process. It can be seen that the application of both the Pt/SiO2¡PAl2O3 and the Pt¡PX/£^-Al2O3 catalysts has a significant effect on reducing the activation energy of the WAO. It was observed that the total COD conversion of the wastewater is as high as 96% and the BOD5/COD ratio of the effluent has been en-hanced up to more than 0.6. The combination of both the CWAO over the Pt¡PX/£^-Al2O3 catalyst and the biological treatment is a promising tech-nique for the PCB¡¦s wastewater treatment to fit the wastewater control regulation in Taiwan, which requests the COD value of the wastewater discharged should be less than 120 mg/L.
433

NOVEL ANTENNA DESIGNS FOR WLAN OPERATIONS FOR A PDA

Su, Saou-Wen 12 June 2003 (has links)
Novel antennas attractive to fit in the internal space of a PDA (Personal Digital Assistant) for WLAN (Wireless Local Area Network) operations are presented in this dissertation. The proposed antennas have in common good impedance bandwidth (defined by 10 dB return loss), covering the dual-band WLAN operation in the 2.4/5.2 GHz bands. Two novel designs of foam-base surface-mount antennas are proposed in Chapters 2 and 3. Surface-mountable antennas, compared with ceramic antennas, are generally low cost in fabrication and rigid in nature. Low-profile and good dual-band operation of the proposed surface-mountable antennas can be observed in Chapters 2 and 3, and in addition, a few present-day WLAN bands at 5 GHz are covered in the operating bandwidths of the proposed foam-base surface-mountable shorted monopole antenna, shown in Chapter 3. Finally, in Chapter 4, a novel planar helical antenna printed on both surfaces of a dielectric substrate is demonstrated. This patent-pending helical antenna is very suitable to print and integrate on a circuit board of a PDA device for 2.4/5.2 GHz WLAN operation.
434

Design of a Highly Constrained Test System for a 12-bit, 16-channel Wilkinson ADC

Pannell, Zachary William 01 December 2009 (has links)
Outer space is a very harsh environment that can cause electronics to not operate as they were originally intended. Aside from the extreme amount of radiation found in space, temperatures can also change very dramatically in a relatively small time frame. In order to test electronics that will be used in this environment, they first need to be tested on Earth under replicated conditions. Vanderbilt University designed a dewar that allows devices to be tested at these extreme temperatures while being radiated. For this thesis, a test setup that met all of the dewar's constraints was designed that would allow a 12-bit, 16-channel analog-to-digital converter to be tested while inside.
435

The Use Of Wavelet Type Basis Functions In The Mom Analysis Of Microstrip Structures

Cakir, Emre 01 December 2004 (has links) (PDF)
The Method of Moments (MoM) has been used extensively to solve electromagnetic problems. Its popularity is largely attributed to its adaptability to structures with various shapes and success in predicting the equivalent induced currents accurately. However, due to its dense matrix, especially for large structures, the MoM suffers from long matrix solution time and large storage requirement. In this thesis it is shown that use of wavelet basis functions result in a MoM matrix which is sparser than the one obtained by using traditional basis functions. A new wavelet system, different from the ones found in literature, is proposed. Stabilized Bi-Conjugate Gradient Method which is an iterative matrix solution method is utilized to solve the resulting sparse matrix equation. Both a one-dimensional problem with a microstrip line example and a two-dimensional problem with a rectangular patch antenna example are studied and the results are compared.
436

Cell Formation: A Real Life Application

Uyanik, Basar 01 September 2005 (has links) (PDF)
In this study, the plant layout problem of a worldwide Printed Circuit Board (PCB) producer company is analyzed. Machines are grouped into cells using grouping methodologies of Tabular Algorithm, K-means clustering algorithm, and Hierarchical grouping with Levenshtein distances. Production plant layouts, which are formed by using different techniques, are evaluated using technical and economical indicators.
437

The ONCE Bibliographic Services’s Digital Library

Pérez Arnaez, Rafael 15 June 2011 (has links) (PDF)
The ONCE provides its membership with a cost-free online library service, through which they can obtain books in both print and DAISY format. The present paper contains a brief description of the structure and growing popularity of this service.
438

Correlation between near field and far field radiated emission of printed circuit boards by genetic algorithms

Fan, Hongmei January 2009 (has links)
Most electromagnetic interference standards specify that measurements of radiated emissions must be performed in the far field (FF), e.g. at an open-area test site or in a semi-anechoic chamber. Since near field (NF) measurements are cheaper, quicker and more flexible compared to FF tests, establishing a correlation between NF and FF data is of great research interest. One strategy to achieve this goal is to find a set of basic radiators comprising electric and magnetic dipoles that generate the same NF as the original source at selected observation points. This set of dipoles, based on the uniqueness theorem, can then be used to predict the FF radiation patterns. The uniqueness theorem requires that electric or magnetic fields are matched on a closed surface with respect to the magnitude and phase. The focus of this thesis is the investigation of FF prediction based on NF magnitude-only data. In this thesis, a robust NF-FF conversion model based on Genetic Algorithms (GAs) is built up to predict the radiation of printed circuit boards (PCBs). This is done by introducing a dipole moment magnitude range pre-selection before the initialisation step of GAs, customising the processes of selection, crossover and mutation for anti-sticking and checking the correlation between NF and FF fitness values. Since the performance of GAs is tightly related to the number of dipoles in the GA model, FF characteristics of generic radiation sources (such as a long wire and a large loop) are analysed using both analytical calculation and source modelling by GAs. For structures with simple FF patterns, if more dipoles than necessary are used, the computational cost of GAs is unnecessarily high. On the other side, for structures with complicated FF patterns, the GA modelling may not be able to well approximate the FF radiation, due to the limitation for GAs to tackle too many unknowns. Therefore the scope of the model applicability is discussed, and a dipole number N, depending on the electrical size of the source, is recommended for GA modelling. By applying GAs to get the equivalent dipole set of a radiating PCB from the magnetic NF magnitudes, NF sampling approaches are investigated in detail, including where to locate NF sampling planes, what plane coverage angle to choose, how many points to observe, what type of data to collect, what dynamic range to allow for the data, and how many planes to choose. Two case studies are presented for predicting the FF radiation of PCBs from magnetic NF magnitude-only observations, and validate the NF sampling approaches in this thesis.
439

Pb-free process development and microstructural analysis of capacitor filter assemblies using solder preforms

Shah, Vatsal. January 2005 (has links)
Thesis (M.S.)--State University of New York at Binghamton, Department of Systems Science and Industrial Engineering, 2005. / Includes bibliographical references (p. 94-96).
440

Using oscillator gain and injection-locking to measure on-chip inductor cupling /

Popplewell, Peter Harris Robert, January 1900 (has links)
Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 110-113). Also available in electronic format on the Internet.

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