State-of-the-art silicon-based power supplies have reached a point of maturity in performance. Efficiency, power density, and cost are major trade-offs involved in further improvements. Most products are custom designed with significant non-recurrent engineering and manufacturing processes that are labor intensive. In particular, conventional magnetic components, including transformers and inductors, have largely remained the same for the past five decades. Those large and bulky magnetic components are major roadblocks toward an automated manufacturing process. In addition, there is no specific approach to reduce electromagnetic interference (EMI) in conventional practices. In certain cases, EMI filter design even requires a trial-and-error process. With recent advances in wide-bandgap (WBG) power semiconductor devices, namely, SiC and GaN, we have witnessed significant improvements in efficiency and power density, compared to their silicon counterparts. In a power factor correction (PFC) rectifier/inverter, the totem-pole configuration with critical conduction mode (CRM) operation to realize zero-voltage switching (ZVS) is deemed most desirable for a switching frequency 10 times higher than current practice. With a significantly higher operating frequency, the integration of inductors with embedded windings in the printed circuit board (PCB) is feasible. However, a PCB winding-based inductor has a fundamental limitation in terms of its power handling capability. The winding loss is proportional to the magnetomotive force (MMF), which is Ni. That is to say, with the number of layers (turns) and currents increased, winding loss is increased nonlinearly. Furthermore, for a large-size planar inductor, flux distribution is usually non-uniform, resulting in dramatically increased hysteresis loss and eddy loss. Thus, current designs are challenged by the capability to increase their power range. To address those issues, a modular building block approach is proposed in this dissertation. A planar PCB inductor is formed by an array of pillars that are integrated into one magnetic core, where each pillar handles roughly 750 W of power. The winding loss is reduced by limiting the number of turns for each pillar. The core loss is minimized with a proposed planar magnetic structure where rather uniformly distributed fluxes were observed in the plates. The proposed approach has a similar loss to a conventional litz wire-based design but features a higher power density and can be easily assembled in automation. A 3 kW high frequency PFC converter with 99% efficiency is demonstrated as an example. Furthermore, PCB-based designs up to 6 kW are provided. Another challenge in a WBG-based PFC/inverter is the high common-mode (CM) noises associated with the high dv/dt of the WBG devices. Symmetry and cancellation techniques are often employed to suppress CM noises in switching power converters. Meanwhile, shielding technique has been demonstrated to effectively suppress CM noises in an isolated converter with PCB-based transformer design. However, for non-isolated converters, such as PFC circuits, none of the techniques mentioned above are deemed applicable or justifiable. Recently, the balance technique has been demonstrated to effectively suppress CM noises up to a point where the parasitic ringing between the inductor and its winding capacitor is observed. This dissertation presents an improved balance technique in a PCB-based coupled inductor design that compensates for the detrimental effect of the interwinding capacitors. A CM noise model is established to simplify the convoluted couplings into a decoupled representation so as to illustrate the necessary conditions for realizing a balanced network. In the given 1 kW PFC example, CM noise suppression is effective in the frequency range of interest up to 30 MHz. The parasitic oscillation of inductors, known to be detrimental for CM noise reduction, is circumvented with the improved magnetic structure. By applying the balance technique to a PFC converter and the shielding technique to an LLC DC/DC converter, significant noise reductions were realized. This provides the opportunity to use a simple one-stage EMI filter to achieve the required EMI noise attenuation for a server power supply. This dissertation further offers an in-depth study on reducing the unwanted near-field couplings between the CM/DM inductors and DM filter capacitors, as well as unwanted self-parasitics such as the ESL of the DM capacitors. An exhaustive finite element analysis (FEA) and near field measurements are conducted to better understand the effect of frequency on the polarization of the near field due to the displacement current. The knowledge gained in this study enables one to minimize unwanted mutual coupling effects by means of physical placement of these filter components. Thus, for the first time, a single-stage EMI filter is demonstrated to meet the EMI standard in an off-line 1 kW, 12 V server power supply. With the academic contributions in this dissertation, a PCB winding-based inductor can be successfully applied to a high-frequency PFC/inverter to achieve high efficiency, high power density, automation in manufacturing, lower EMI, and lower cost. Suffice it to say, the proposed approach enables a paradigm shift in the designing and manufacturing of a PFC/inverter for the next generation of power supplies. / Doctor of Philosophy / State-of-the-art silicon device-based switching power supplies have reached a point of maturity in performance. Efficiency, power density, and cost are major trade-offs involved in performance improvements. Most products are custom designed, requiring significant non-recurrent engineering and labor-intensive manufacturing processes. In particular, conventional magnetic components, including transformers and inductors, have largely remained the same for the past five decades. Those large and bulky magnetic components are major roadblocks toward an automated manufacturing process. In addition, there is no specific approach to reduce electromagnetic interference (EMI) in conventional practices. In consequence, a large multi-stage EMI filter is usually adopted between the power converter and the grid to reduce the EMI noise. It generally occupies 1/4-1/3 of the total converter volume. In certain cases, EMI filter design even requires a trial-and-error process. Suffice it to say, EMI is still regarded as both science and art. With recent advances in wide-bandgap (WBG) power semiconductor devices, namely, SiC and GaN, we have witnessed significant improvements in efficiency and power density, compared to their silicon counterparts. With GaN devices, the switching frequency of a PFC converter is able to be increased by 10 times compared to the state-of-the-art design without compromising efficiency. With a significantly higher operating frequency, the integration of inductors with embedded windings in the printed circuit board (PCB) is feasible. However, the state-of-the-art PCB winding-based inductor has a fundamental limitation in power range. Its winding loss and core loss increase dramatically in high powers. To address this issue, a modular building block approach is proposed in this dissertation. A planar PCB inductor is formed by an array of pillars that are integrated into one magnetic core, where each pillar handles roughly 750 W of power. The winding loss is reduced by limiting the number of turns for each pillar. The core loss is minimized with a proposed planar magnetic structure where rather uniformly distributed fluxes have been observed in the magnetic core plates. A 3 kW high-frequency PFC converter with a 99% peak efficiency is demonstrated as an example. Furthermore, PCB-based designs up to 6 kW are provided. Another challenge in a WBG-based PFC/inverter is the high common-mode (CM) noises caused by the high switching speed of the WBG devices. Symmetry and cancellation techniques are often employed to suppress CM noises in switching power converters. Meanwhile, shielding technique has been demonstrated to effectively suppress CM noises in an isolated converter with PCB-based transformer. However, for non-isolated converters, such as PFC circuits, none of the techniques mentioned above are deemed applicable or justifiable. Recently, the balance technique has been demonstrated to effectively suppress CM noises up to several MHz. However, the CM noise reduction is not effective beyond that. This dissertation presents an improved balance technique in a PCB-based coupled inductor to circumvent the limits. In the given 1 kW PFC example, CM noise suppression is effective in the frequency range of interest up to 30 MHz. By applying the balance technique to a PFC converter and the shielding technique to an LLC DC/DC converter, significant noise reductions were realized. This provides the opportunity to use a simple one-stage EMI filter to achieve the required EMI noise attenuation for a server power supply. It features a smaller volume compared to a conventional multi-stage filter. To further enhance the filter's performance at high frequencies, an exhaustive finite element analysis and near field measurements are conducted to better understand the effect of frequency on the polarization of the near field due to the displacement current. The knowledge gained in this study enables one to minimize unwanted mutual coupling effects through physical placement of these filter components. Several approaches for improving the filter performance at high frequency are conducted. With these approaches applied, a single-stage filter is demonstrated in an off-line 1 kW, 12 V server power supply. Thus, for the first time, a single-stage EMI filter can be contemplated to meet the EMI standard in server power supplies. With the academic contributions in this dissertation, a PCB-winding based inductor can be successfully applied to a high-frequency PFC/inverter to achieve high efficiency, high power density, automation in manufacturing, lower EMI, and lower cost. Suffice it to say, the proposed approach in this work enables a paradigm shift in the designing and manufacturing of a PFC/inverter for the next generation of power supplies.

The FDR (Frequency Disturbance Recorder) is a data acquisition device for the power system. The device is portable and can be used with any residential wall outlet for frequency data collection. Furthermore, the FDR transmits calculated frequency data to the web for access by authorized users via Ethernet connection. As a result, Virginia Tech implemented Frequency Monitoring Network (FNET) with these FDR devices. FNET is a collection of identical FDRs placed in different measurement sites to allow for data integration and comparison. Frequency is an important factor for power system control and stabilization. With funding and support provided by ABB, TVA and NSF the FDRs are placed strategically all over the United States for frequency analysis, power system protection and monitoring. The purpose of this study is to refine the current FDR hardware design and establish a new design that will physically fit all the components on one Printed Circuit Board (PCB). At the same time, the software that is to be implemented on the new board is to be kept similar if not the same as that of the current design. The current FDR uses the Axiom CME555 development board and it is interfaced to the external devices through its communication ports. Even through the CME555 board is able to meet the demands of the basic FDR operations, there are still several problems associated with this design. This paper will address some of those hardware problems, as well as propose a new board design that is specifically aimed for operations of FDR. / Master of Science

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are common contaminants of sediment, soils and biological tissues. These compounds pose a significant risk to biological and ecosystem health and functioning due to these compounds being mutagenic, carcinogenic and are known to disrupt the endocrine system. The bioaccumulation and biomagnification potential that these compounds possess mean that they are capable of affecting the entire food chain and are not limited to the organisms that are directly in contact with the compounds Even though there has been an increase in the attention on identifying the presence and impacts that these compounds may have in South Africa, the level of attention is lower than what it is in other countries around the world. Although South Africa has guidelines in place for other pollutants, such as metals, there are no such guidelines in place to monitor PAHs and PCBs.. Industries are known to release both PAHs and PCBs, mainly from incomplete burning processes and the release of oils and fuels in the case of PAHs, and from heat transfer fluids in the case of PCBs. Durban Bay and surrounding areas of eThekwini, KwaZulu-Natal are highly industrialised with many aquatic systems, in which these contaminants are likely to deposit. The aim of this research was to determine the concentrations of these compounds by means of chemical analysis and additionally biological analysis, using the H4IIE-luc bioassay and compare these levels to international guideline levels. It was found that the concentrations of the 23 analysed PAHs were 6.5–3 235.6 ng.g-1 and the concentration of the PCBs analysed were 0–113.83 ng.g-1. Many sites were found to be in exceedance of the guideline limits, particularly in the harbour. Toxic equivalency factors (TEF) were used to gauge the toxic equivalency (TEQ) of the PAHs and PCBs that were found. The TEQs were generally low, and were below any guideline levels. The assay revealed the extract containing the PCBs had a bioassay equivalence (BEQ) of 0–93.54 pgTCDDeq. g-1 and the extract containing the PAHs of 0–776.08 pgTCDD-eq.g-1. With a proportion of the sites exceeding guideline limits. The BEQ results were two to three orders of magnitude greater than the TEQs calculated from the concentrations determined by the instrumental analysis, however, followed a similar trend. Additionally chemical analysis was not performed on a full suite of compounds that are able to elicit a response from the cells, which could be a reason why the BEQ and TEQ did not follow a similar trend among some of the samples. It would have been more beneficial to have performed chemical analysis on the 16 priority PAHs (as determined by the United States Environmental Protection Agency), the dioxin-like PCBs and polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDFs) which are all capable of eliciting a response from the cells and have TEF values. The areas that were most affected by contamination of these compounds was the harbour and surrounding canals, and there was point source contamination along the Umhlatuzana, Umbilo, and Amanzimnyana Rivers. All dl-PCBs should be chemically analysed at all the sample areas, as these cause adverse effects to biota. In addition to this, biota should be sampled to determine concentrations of the compounds to determine bioavailability and the degree of bioaccumulation in the food chain. Utilising biomarkers it would be possible to determine stresses of fish. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are common contaminants of sediment, soils and biological tissues. These compounds pose a significant risk to biological and ecosystem health and functioning due to these compounds being mutagenic, carcinogenic and are known to disrupt the endocrine system. The bioaccumulation and biomagnification potential that these compounds possess mean that they are capable of affecting the entire food chain and are not limited to the organisms that are directly in contact with the compounds Even though there has been an increase in the attention on identifying the presence and impacts that these compounds may have in South Africa, the level of attention is lower than what it is in other countries around the world. Although South Africa has guidelines in place for other pollutants, such as metals, there are no such guidelines in place to monitor PAHs and PCBs.. Industries are known to release both PAHs and PCBs, mainly from incomplete burning processes and the release of oils and fuels in the case of PAHs, and from heat transfer fluids in the case of PCBs. Durban Bay and surrounding areas of eThekwini, KwaZulu-Natal are highly industrialised with many aquatic systems, in which these contaminants are likely to deposit. The aim of this research was to determine the concentrations of these compounds by means of chemical analysis and additionally biological analysis, using the H4IIE-luc bioassay and compare these levels to international guideline levels. It was found that the concentrations of the 23 analysed PAHs were 6.5–3 235.6 ng.g-1 and the concentration of the PCBs analysed were 0–113.83 ng.g-1. Many sites were found to be in exceedance of the guideline limits, particularly in the harbour. Toxic equivalency factors (TEF) were used to gauge the toxic equivalency (TEQ) of the PAHs and PCBs that were found. The TEQs were generally low, and were below any guideline levels. The assay revealed the extract containing the PCBs had a bioassay equivalence (BEQ) of 0–93.54 pgTCDDeq. g-1 and the extract containing the PAHs of 0–776.08 pgTCDD-eq.g-1. With a proportion of the sites exceeding guideline limits. The BEQ results were two to three orders of magnitude greater than the TEQs calculated from the concentrations determined by the instrumental analysis, however, followed a similar trend. Additionally chemical analysis was not performed on a full suite of compounds that are able to elicit a response from the cells, which could be a reason why the BEQ and TEQ did not follow a similar trend among some of the samples. It would have been more beneficial to have performed chemical analysis on the 16 priority PAHs (as determined by the United States Environmental Protection Agency), the dioxin-like PCBs and polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDFs) which are all capable of eliciting a response from the cells and have TEF values. The areas that were most affected by contamination of these compounds was the harbour and surrounding canals, and there was point source contamination along the Umhlatuzana, Umbilo, and Amanzimnyana Rivers. All dl-PCBs should be chemically analysed at all the sample areas, as these cause adverse effects to biota. In addition to this, biota should be sampled to determine concentrations of the compounds to determine bioavailability and the degree of bioaccumulation in the food chain. Utilising biomarkers it would be possible to determine stresses of fish. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

The ability of Chromolaena odorata propagated by stem cuttings and grown for six weeks in the greenhouse to thrive in soil containing different concentrations of PCB congeners found in Aroclor and transformer oil, and to possibly remediate such soil was studied under greenhouse conditions. Chromolaena odorata plants were transplanted into soil containing 100, 200, and 500 ppm of Aroclor and transformer oil (T/O) in 1L pots. The experiments were watered daily at 70% moisture field capacity. Parameters such as mature leaves per plant, shoot length, leaf colour as well as the root length at harvest were measured. C. odorata growth was negatively affected by T/O in terms of shoot length and leaf numbers, but no growth inhibition was shown by Aroclor. At the end of six weeks of growth, Plants size was increased by 1.4 and 0.46%, but decreased at -1.0% in T/O, while increases of 45.9, 39.4 and 40.0% were observed in Aroclor treatments. Mean total PCB recoveries were 6.40, 11.7, and 55.8μg in plants tissues at Aroclor treated samples resulting in a percentage reduction of PCB from the soil to 2.10, 1.50, and 1.10 at 100, 200, and 500mg/kg Aroclor treatments respectively. There was no PCB recovery from plants in transformer oil treatments as a result of its inhibition to growth. Root uptake was found to be the probable means of remediation of PCB-contaminated soil by C. odorata, this was perhaps aided by microbes. This study has provided evidence on the ability of C. odorata to remediate PCB contaminated soil. However, the use of C. odorata for phytoremediation of PCB contaminated soil under field condition is therefore advised. / Environmental Sciences / M.Sc. (Environmental Science)

<p>The aim of the research work presented here, is to contribute to the adaptation of electronic packaging towards the needs of high frequency applications. As the field of electronic packaging stretches over several very different professional areas, it takes an interdisciplinary approach to optimize the technology of electronic packaging. Besides this, an extensive knowledge of industrial engineering should be an essential part of this undertaking to improve electronic packaging. Customary advances in technology are driven by new findings and a continuous development of processes in clearly defined fields. However, in the field of the higher levels of the interconnection hierarchy, that is external to the chip level interconnections and chip packaging, it is supposed that a wide combination of disciplines and technical creativity, instead of advanced technology in a special area should produce most added value.</p><p>The thesis is divided into five areas, interlinked by the overall aim of there advantages to the common goal. These areas are the Printed Wiring Board (PWB) technology, PWB connections using flexible printed circuit boards, multiconductor cable connections, shielded enclosures and the related EMC issues, and finally the cooling of electronics. A central issue was to improve the shielded enclosures to be effective also at very high frequencies; it will be shown that shielded enclosures without apertures can cope with frequencies up to and above 15 GHz. Due to this enclosure without apertures, it was necessary to develop a novel cooling structure. This cooling structure consists of a heat sink where the PCB’s are inserted in close contact to the cooling fins on one side, whereas the other side of the heat sink is cooled by forced ventilation. The heat transfer between these parts is completely inside the same body. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling.</p><p>Another problem area that is addressed are the interconnect problems in high frequency applications. Interconnections between parts of a local electronic system, or as within the telecom and datacom field between subscribers, are commonly accomplished by cable connections. In this research work multiconductor cables are examined and a patented novel cable-connector for high frequency use is presented. Further, an experimental complex soldering method between flexible printed circuits boards and rigid printed circuits boards, as part of connections between PCBs, is shown. Finally, different sectors of the PCB technology for high frequency applications are scrutinized and measurements on microstrip structures are presented.</p>

關於產品創新的研究，絕大多數學者均以B2C的企業產品作為研究探討的對象，強調以新的產品設計帶給消費者全新的生活體驗與感受。相較之下B2B的企業產品，特別是客製化零組件產品，業者大多只能以改善製程生產效率、提升良率等手法來維持競爭力。印刷電路板業即為上述B2B客製化零組件產品在台灣地區的代表性產業。本研究即以我國印刷電路板業A公司軟硬複合板的開發為例，探討此種B2B企業的客製化產品之產品創新模式。 本研究由相關文獻探討，推展出以「新產品開發管理」、「製程技術開發管理」與「組織文化」此三個構面的研究架構來探討印刷電路板業在產品創新活動的關鍵因素與管理項目，採個案研究法深入訪談個案公司的高階主管，以瞭解其產品創新過程的實務作為。由個案分析與研究發現得出研究結論如下: 結論一：在B2B企業的客製化產品開發過程中，明確的產品策略，具體的產品概念，和互動良好的客戶參與，是新產品開發成功的關鍵因素。 結論二：機器設備的開發與實驗活動，對B2B製造業的製程技術開發占有關鍵地位。 結論三：有效的知識管理及技術開發人員的管理與領導，是B2B客製化產品企業之製程開發活動中重要的管理項目。 結論四：差異化的企業組織策略，創新的價值觀與高階主管對創新活動的支持，對產品技術創新的成功有正面的影響。 / Regarding product innovation, a lot of studies did focus on B2C business, try to find a way to create “new feeling” product for consumers. For B2B business, especial for customization product, most firms do effort for production efficiency increasing, yield rate improvement, and cost reduction to maintain the competition. Printed circuit board (PCB) is this kind of industry in Taiwan typically. This research bases on a PCB company (A-company) rigid-flex PCB development case, to study B2B business’s product innovation model. The three major constructs of the research framework include new product development and its management, new process development and its management, and organizational culture. This research adopts case-study method to analysis the practice actions in A-company. The research results as below: 1. Clear product strategy, solid product concept, and good customers’ join, are the key points to get new product development success. 2. Equipment development and experiment actions are very important factors for process technology development in B2B firms. 3. Well knowledge management, good R&D people management and leadership, are the important management items for process technology development in B2B firms. 4. Differentiation strategy, innovation value, and top managers’ attitude for innovation action supporting, will lead product technology innovation success.

Obesity is a worldwide problem affecting both children and adults. Genetic, physiological, environmental, psychological, social and economic factors interact in varying degrees, influencing body weight and fat distribution and the progress of obesity. Moreover, some anthropogenic chemicals have proven to be endocrine disrupting chemicals (EDCs) with the potential to interfere with different actions of hormones in the body. EDCs may thereby disrupt homeostasis, modifying developmental, behavioral and immune functions in humans and animals, and also promoting adiposity. Because hormones generally act at low concentrations, small changes in the endocrine system may lead to extensive effects. Based on data from experimental and epidemiological studies this thesis elucidates the relationship between a large number of environmental contaminants and obesity. The experimental studies demonstrated that fructose supplementation in the drinking water resulted in unfavorable metabolic alterations such as a higher liver somatic index (LSI), an increase in plasma triglycerides and increased plasma levels of apo A-I. Fructose in combination with exposure to bisphenol A (BPA) increased liver fat content and plasma levels of apo A-I in juvenile female Fischer 344 rats. The experimental studies also showed that the retro-peritoneal fat, which in rats is a distinct fat depot easy to distinguish and dissect, correlated well with the measurements of total fat mass analyzed with MRI, and could therefore be used as a substitute for total fat mass in rats. The epidemiological studies showed that circulating levels of persistent organic pollutants (POPs) were related to fat mass measured by DXA. OCDD, HCB, TNC, DDE and the less chlorinated PCBs were positively related to fat mass, while the more highly chlorinated PCBs showed a negative association. Further, circulating levels of BPA were positively associated with levels of the hormones adiponectin and leptin, but negatively related with ghrelin, hormones which are involved in the regulation of hunger and satiety. However, serum BPA levels were not related to measures of fat mass in the elderly individuals in the PIVUS cohort. This thesis concludes that environmental contaminants such as BPA and POPs most likely are contributors, along with genetic, social and behavioral factors, to the development of obesity.

[pt] Este trabalho tem como objetivo avaliar a viabilidade técnica para fabricação de placas de circuito impresso de múltiplas camadas com espessuras reduzidas mantendo a integridade dos sinais que se propagam em conexões inter- chip, nas taxas de transmissão de 1Gb/s e 10Gb/s para aplicações em redes de comunicações nos padrões 1GB Ethernet e 10GB Ethernet. A avaliação inclui o projeto de uma placa de 6 camadas de planos condutores, com espessura total de 1,29mm. A placa desenvolvida contém linhas de transmissão, vias e curvas, microcapacitores , microresistores e conectores I/O adequados para a faixa de freqüência em questão. / [en] The main purpose of this work is to evaluate the technical reliability to fabricate a Printed circuit board (PCB) with reduced thickness multilayer keeping signal Integrity on inter-chip connections in 1Gb/s and 10Gb/s (1GB Ethernet and 10GB Ethernet network communications). This evaluation includes the development of a PCB project with 06 layers and 1,29mm thickness. The PCB contains several transmission lines, vias, bends, microcapacitors, microresistors, connectors (I/O) suitable to this frequency band.

This master thesis will cover the prestudy, hardware selection, design and implementation of a PCI Express bridge in the M.2 form factor. The thesis subject was proposed by WISI Norden who wished to extend the functionality of their hardware using an M.2 module. The bridge fits an M-Key M.2 slot and has the dimensions 80x22 mm. It is able to communicate at speeds up to 8 Gb/s over PCI Express and 200 Mbit/s on any of the 20 LVDS/CMOS pins. The prestudy determined that an FPGA should be used and a Xilinx Artix-7 device was chosen. A PCB was designed that hosts the FPGA as well as any power, debugging and other required systems. Associated proof-of-concept software was designed to verify that the bridge operated as expected. The software proves that the bridge works but requires improvement before the bridge can be used to translate sophisticated protocols. The bridge works, with minor hardware modifications, as expected. It fulfills all design requirements set in the master thesis and the FPGA firmware uses a well-established protocol, making further development easier.