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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.
171

Optimizing Solvent Extraction of PCBs from Soil

O'Connell, Maureen January 2009 (has links)
Polychlorinated biphenyls (PCBs) are carcinogenic persistent contaminants. Although their manufacturing in North America ceased in the late 1970s, their high heat resistance made their use widespread over their production lifetime. As a result, PCB contamination has occurred globally and in particular has plague brownfield redevelopment in urban environments. The remediation of PCB contaminated soil or sediments has historically been dealt with through the expensive and unsustainable practice of excavation followed by off-site disposal or incineration. One potential technology that has shown some success with on-site remediation of PCB contamination is solvent extraction. Solvent extraction is technically simple; it involves excavating the contaminated soil, placing it in a vessel and adding solvent. The PCBs are extracted by the solvent and the treated soil is returned for use on site. Although successful at removing a large quantity of PCBs from some soils, this technology can be improved upon by extracting additional PCB mass and making the extraction more efficient and suitable for colder climates. This thesis aimed to identify the factors controlling PCB extraction with solvents in order to optimize PCB extraction as it is applied on different soil types and in various climates. The research investigated the impact of elevated moisture contents (≤ 20% by weight) on solvent extraction efficiency, the effects of low temperatures (<5ºC) on solvent extraction, and developed a kinetic model to represent PCB solvent extraction. As past research has shown, weathered PCB in soil is more difficult to remove. Contaminated field samples from Southern Ontario, Canada were used for this work, rather than synthetically prepared samples. The impact of elevated moisture contents and low temperature on extraction efficiency was determined through a series of screening experiments using polar and non-polar solvents at both 20ºC and 4ºC. It was hypothesized that improved extractions may be possible with combinations of polar and non-polar solvents. Based on the results of these screening experiments, a factorial experiment was designed using solvent combinations to further assess the role of moisture contents and low temperatures. The role of PCB mass distribution among grain sizes was also evaluated to see if optimization based on grain size separation is possible. Finally, experiments were performed to generate data suitable for the development of a kinetic model that incorporates key factors affecting solvent extraction. Four suitable solvents for solvent extraction in Ontario were identified through a literature review and these were used for this work: isopropyl alcohol (polar), ethanol (polar), triethylamine (non-polar) and isooctane (non-polar). Triethylamine outperformed isooctane and performed best on its own rather than in combination with polar solvents. An interaction between soil moisture content and choice of polar solvent (isopropyl alcohol versus ethanol) was established: a given polar solvent achieves optimal PCB extraction at a specific moisture content range. Temperature was also identified as significantly influencing PCB extraction. Although it was determined that PCBs were distributed unevenly amongst grain sizes, a simple relationship between grain size and fractional organic carbon or organic content was not found. A simple two-compartment kinetic model was developed which is suitable for predicting the PCB concentrations extracted up to 24 hours. The model incorporates both temperature and soil to solvent ratio in order to estimate PCB concentration extracted.
172

The Study on Transformation Strategy in Production Base in Taiwan for the Printed Circuit Board Industry ¡V A Corporation as Case Study

Tu, Kung-Tzu 10 August 2010 (has links)
ABSTRACT In recent years China's rapid rise and low-cost advantages, has brought the greatest impact on the printed circuit board industry, low-cost competition for the majority of Taiwanese companies are not strengths, combined with the financial crisis began in 2008, followed by 2009, the world consumer electronics market tightening, are tested in Taiwan for the production of printed circuit board industry base in the viability of manufacturers. In this study, through the study of Taiwan as a production base in case the printed circuit board companies, in the face of financial crisis in 2008, and follow-up to internal and external changes in the industry and the growth and decline of national competitiveness, the restructuring strategy is adopted to overcome the external environmental challenges of rapid change, which concludes with Taiwan as a production base of the printed circuit board industry, in the face of financial turmoil and economic environment changes and the overall production of cross-strait ECFA signed, to the advantage of strengths and talents of Taiwan culture resources, so printed circuit board manufacturing industry can continue to Taiwan as a production base, more competitive challenges towards internationalization. In this study, the research method is qualitative research in the case study method, the scope of the production base of a Taiwanese printed circuit board industry, the use of literature survey and data compilation, and the case company interviews, and data collation, the first stage first motive of enterprise transformation, analysis and use of five forces analysis and diamond model to understand the background and conditions of business transformation, the second stage, the case company interviews, SWOT analysis summarized the case company and the feasibility assessment and develop transformation strategies, and understanding of the transformation strategy of the key success factors. The study concludes on the hope that the production base in Taiwan for the printed circuit board industry in the face of changing external environment when assessing the feasibility of transformation strategy and development, and further development of Taiwan companies for the future a reference transformation strategy. Keywords¡GPrinted Circuit Board (PCB), Five Forces Analysis, Diamond Model, SWOT Analysis, Transformation Strategies
173

N/A

Jian, Zhong-Yi 29 August 2005 (has links)
Electronic Industry is the leader of Taiwan manufacturing industries. Recently, the Electric Manufacture Service (EMS) of Taiwan has adopted the American professional model. In electronic products, Print Circuit Board (PCB) is a key important component with high reliability. Print Circuit Board is a customer-made product possesses unique manufacturing features, such as high quality, complicated and protracted manufacturing process, etc. The aim of this study is to evaluate whether the correct selection of the PCB supplier by the Supplier Evaluation Department is of utmost importance in assisting the establishment of a successful business among the electronic manufacturing service companies that utilizing the professional knowledge and techniques in the EMS value chain. This study integrates the management designs from ISO 9001, QS9000 and TQM to provide the evaluation system for PCB products. The related literatures were applied to the whole evaluation methodology, divided into Quality System and Processing Control. Using the Processing Control as the center, it breaks up all the product-related functional departments and processing procedures of PCB into units. According to the long-term PCB supplier evaluation experience, this study details the common mistakes and evaluation standard of each evaluation item. It also provides the related flow-charts for supplier evaluation process. The major differences of evaluation methodology between electronic and traditional industries are evaluated. Major conclusions and suggestions are obtained by simultaneously collecting a large amount of secondary information in the field, and in depth interview with the middle and high levels managers of the PCB factories. The major conclusions and suggestions are as follow: 1. Coordinate with purchasing strategy Establish an effective supplier evaluation system to select the most suitable supplier both in the quality- and cost-controls. The ordinary EMS factories will receive OEM orders of different PCB technical levels and products from different customers. This system could help finding the most suitable supplier for the job. 2. Obtain the best quality assurance for the final products According to the validation of the in-field evaluation, this study separates the analytical results into four categories. It concludes a variant table based on the levels of evaluation, manufacturing capability index and product usage. This variant table will recommend the most capable supplier in accordance with the different PCB technical levels. 3. Minimize the variation of evaluation personnel This study details the common mistakes and the evaluation standard of each evaluation item providing references to the EMS or ODM companies. After several in-field trainings, the variation of the evaluation personnel can be minimized to the least. 4. Improve the managing and manufacturing capability of PCB supplier Select the best part of the QS9000 management techniques as the references for PCB supplier to conduct the Six Sigma or Business Process Improvement (BPI). In order to improve the managing and manufacturing capability of PCB suppliers, this study suggests conducting the practical execution and prevention methods and continuous improvement activities. Through these action plans, it can decrease the unqualified rate and rejected cost, improve the management constitution, become the world-class manufacturing factories and obtain high profit.
174

A Case Study: Improvement Of Component Placement Sequence Of A Turret Style Smt Machine

Cengel, Savas Mehmet 01 January 2007 (has links) (PDF)
This study aims to improve component placement sequencing of a number of PCBs produced on a turret style SMT machine. After modeling the problem and having found that an optimal solution to the real PCB problem is hard to be achieved because of the concurrent behavior of the machine and the PCB design parameters, two heuristics are developed by oversimplifying the problem down to TSP. Performance of the heuristics and the lower bounds is evaluated by comparing the results with the optimal solution for two sets of randomly generated PCBs. The heuristic solutions are also compared with the lower bounds and the current implementation for the real PCBs. It is found out that the heuristics improve the current efficiency figures of the company.
175

An efficient FDTD modeling of the power delivery system of computer package with SMT decoupling capacitors

Tsai, Chia-Ling 08 July 2003 (has links)
The operation speed of modern computer system has been upgraded from several hundred MHz to GHz. The instant current will pass to the power plane of the mother board by way of the IC pins and result in electromagnetic wave propagation between the power and ground plane, so called ¡§Ground bounce.¡¨ To prevent the ground bounce from IC operation, decoupling capacitors are used. In this thesis, an efficient numerical approach which is based on the two-dimensional (2D) finite-difference time-domain (FDTD) method and with a new recursive algorithm has been used for modeling the power/ground planes characteristics with SMT capacitors above them. By the way, we take several methods, such as Debye model, FDTD-SPICE, and telegrapher¡¦s equation, for modeling various mother board structures. Finally, we use the genetic algorithm for calculating the optimum capacitor placements to meet the expect ground bounce limitation.
176

The Application of Ferrite Process on Industrial Wastewater Treatment and the Catalysis of Ferrospinels

Huang, Yu-jen 17 July 2009 (has links)
In industrial wastewater, there are usually many kinds of organics and heavy metals and can cause damage on human health and environment without well treatment. Printed Circuit Board (PCB) industrial wastewater is a typical example due to the complicated manufacture processes and the use of specific chemicals. In this study, the PCB industrial wastewater is collected and then treated by the combination of Fenton method and Ferrite Process (or called Fenton-Ferrite Process, FFP). Moreover, the recycling possibility of sludge generated from FFP is also studied. Through this study, the treatment procedure of wastewater containing organics heavy metals is established and the direction of sludge reuse is also provided. To realize the characteristic of PCB industrial wastewater, the wastewater from some PCB factory in southern Taiwan was firstly collected and analyzed to identify the pollution concentrations and then treated by FFP. The experimental results showed that the optimum parameters of Fenton method in FFP were pH = 2, [Fe2+]= 500 mg/L, [H2O2]= 3000 mg/L, reaction time= 60 min and batch dosing, and the residual COD and TOC were 84.9 mg/L and 58.3 mg/L under the COD regulation standard 120 mg/L. Meanwhile, the proper conditions of Ferrite Process in FFP were pH= 10, reaction temperature= 80¢J, reaction time= 40 min, aeration rate= 3 L/min/L wastewater, Fe/Cu molar ratio= 10 and three-stage reaction. Under that circumstance, the residual [Cu2+] in wastewater was 0.18 mg/L and the Toxicity Characteristic Leaching Procedure (TCLP) test of sludge from FFP was 4.58 far below the effluent standard 3 mg/L and TCLP standard 15 mg/L. The properties of sludge were further investigated by X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and Superconducting Quantum Interference Device (SQUID). The pattern of XRD indicated that the major structures were Fe3O4 and CuFe2O4; the figure of SEM showed that the surface of sludge was composed of many round particles and the distribution of particle size was from 50 nm-100 nm; the magnetic property analyzed by SQUID showed that the saturation moment was 62.85 emu/g. In the research of sludge applied in catalytic incineration, the o-xylene conversion was 97 % by sludge but only 31 % by quartz sand at 400 ¢J. Moreover, in the 72 hr-decay test of catalyst, the results clearly indicated that the performance did not obviously decline and there were no any byproducts but CO2. Therefore, the investigation revealed that the sludge had great potential in catalytic reaction. The catalytic performance of various ferrospinels generated from different manufactured conditions was also studied. Through the screening of catalysts, the order of various ferrospinels activity was Cu-ferrite > Mn-ferrite > ferrite ¡Ü Zn-ferrite and the most effective Cu-ferrite was manufactured at pH= 9 and T= 90 ¢J. After 72 hr test, the decay of catalyst was not also found. In the examination of Cu-ferrite physical property, the XRD pattern showed that the structure was CuFe2O4; the figure of SEM illustrated that there was no difference between the surface of fresh and used catalyst; the magnetic property measured by SQUID showed that the saturation moment was 30.89 emu/g.
177

Further Development of an Audio Analyzer / Vidareutveckling av en audioanalysator

Klevhamre, Benny, Nilsson, Peter January 2002 (has links)
<p>En del av en Audioanalystor har blivit utveckladoch implementerad som en applikation i det hårdvarubeskrivande språket VHDL. Denna del har sedan programmerats in i en PLD-krets på ett kretskort som används i audiotester för mobiltelefoner på Flextronics. Applikationen konverterar data så att det ska gå att skicka information mellan telefonen och olika mätinstrument. Applikationen består av två äldre applikationer. Av dessa två har en blivit helt implementerad. I den andra kvarstår att finna orsaken till varför den ger ifrån sig felaktigt data i form av oönskat brus. Arbetet avbröts p.g.a. slutdatum. A part of an audio analyzer has been developed and implemented as an application in the hardware description language VHDL. This part has later been programmed into a PLD device on a circuit board used for audio tests on mobile telephones at Flextronics. The application converts data, making it possible to send information between the telephone and different measuring instruments. The application consists of two older applications. One of them has been fully implemented. What is left in the other part is to find the cause why it is sending wrong data as unwanted noise. The work had to be stopped when deadline was reached</p> / <p>A part of an audio analyzer has been developed and implemented as an application in the hardware description language VHDL. This part has later been programmed into a PLD device on a circuit board used for audio tests on mobile telephones at Flextronics. The application converts data, making it possible to send information between the telephone and different measuring instruments. The application consists of two older applications. One of them has been fully implemented. What is left in the other part is to find the cause why it is sending wrong data as unwanted noise. The work had to be stopped when deadline was reached.</p>
178

Persistent organic pollutants (POPs) in soil associated with an active incinerator in Potchefstroom, South Africa / L.P. Quinn

Quinn, Laura Penelope January 2005 (has links)
POPs are a group of chemicals that have been extensively studied over the last few years. The main reason that these chemicals have received so much scientific attention is the myriad of negative effects they have on the environment and human health. The properties that cause the deleterious effects include a high molecular stability, rendering them highly persistent. Added to this is the lipophilic and hydrophobic nature of the compounds. POPs will thus tend to bio-accumulate and bio-magnify in the environment, causing a direct threat to humans and wildlife. To address this threat, the Stockholm Convention on Persistent Organic Pollutants, under the supervision of United Nations Environment programme (UNEP), was initiated and became legally binding on 17 May 2004. All countries, including South Africa, which ratified this agreement, will be expected to monitor and regulate the formation of POPs. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are all members of the dioxin-like family of POPs. This family of chemicals pose serious health threats such as carcinogenic effects and negative effects on reproduction. These substances, with the exception of PCBs, are formed unintentionally as by-products of industrial and thermal processes. One of the main sources of dioxin-like chemicals is medical waste incinerators. In this project the area surrounding a medical waste incinerator was monitored using a bio-assay technique. The determination of dioxin concentrations is usually preformed by chemical analysis, however, bio-assays have proven themselves to be a cheaper and time-saving screening method. The Toxic Equivalency Quotient (TEQs) determined through bio-assays can support chemical analysis in determining biologically-relevant risk assessments since bio-assay data has ecotoxicological relevance. These assays represent an integrated biological response to chemical pollutants, where biological effects are accounted for which is not possible in chemical analyses. One of the bio-assays used in the determination of the dioxin-like chemical TEQ is the H411 E reporter gene bio-assay. This assay is based on the Ah-receptor mediated toxicity of dioxin-like chemicals. Using this technique the TEQs for areas surrounding an active incinerator were determined, to indicate the distribution of these substances. The TEQs for the soil samples collected ranged between nondetectable and 154 ngTEQ/kg. There was no clear distributional pattern and the total organic carbon content in the soil did not seem to play a crucial role in the distribution of dioxin-like chemicals. Although a decrease in soil tillage showed a corresponding increase in TEQ. The predominant wind direction was taken into account but no correlation could be seen. However, meteorological parameters such as the ambient temperature and low precipitation in the area may have contributed to lower TEQ values. Cytotoxicity excluded data points and the phenomenon has to be addressed. High TEQ values in a residential area where free-range chickens are raised pose a serious concern to the level of dietary dioxin-like chemical intake. Eggs in the area could theoretically contain between 2.75 and 28.75 pgTEQ/g egg fat. Further studies are needed to determine how much dioxin-like chemicals are being transferred to humans through the consumption of free-range eggs / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2006.
179

SUSTAINABLE RESOURCE UTILIZATION IN MANUFACTURING OF PRINTED CIRCUIT BOARD ASSEMBLY: EXERGY ANALYSIS OF THE PROCESS

Saiganesh, Subramaniam 01 January 2010 (has links)
Engineering for sustainable development requires prudent utilization of resources under economic, environmental and societal constraints. Resource utilization must follow a holistic approach. This brings in a need for comprehensive metrics which are simple, standard and universal. Thermodynamics may offer a metric that focuses on both quality and quantity of energy resources which may carry information to be combined with other metrics. This metric may be a thermodynamic property called exergy or available energy, which provides a better insight into resource use in both energy and non-energy producing systems. This thesis is devoted to a study of the exergy concept in manufacturing. A high volume PCB assembly, manufactured in a state of the art soldering facility is chosen for the study. Various mass and energy resources flowing through the production line were quantified in terms of exergy. On the basis of exergy content and exergy utilization in the production process, the sustainability in terms of resources use is discussed. An early version of this approach was presented at the International Symposium on Sustainable Systems and Technologies, IEEE, Washington DC, in May 2010.
180

Persistent organic pollutants (POPs) in soil associated with an active incinerator in Potchefstroom, South Africa / L.P. Quinn

Quinn, Laura Penelope January 2005 (has links)
POPs are a group of chemicals that have been extensively studied over the last few years. The main reason that these chemicals have received so much scientific attention is the myriad of negative effects they have on the environment and human health. The properties that cause the deleterious effects include a high molecular stability, rendering them highly persistent. Added to this is the lipophilic and hydrophobic nature of the compounds. POPs will thus tend to bio-accumulate and bio-magnify in the environment, causing a direct threat to humans and wildlife. To address this threat, the Stockholm Convention on Persistent Organic Pollutants, under the supervision of United Nations Environment programme (UNEP), was initiated and became legally binding on 17 May 2004. All countries, including South Africa, which ratified this agreement, will be expected to monitor and regulate the formation of POPs. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are all members of the dioxin-like family of POPs. This family of chemicals pose serious health threats such as carcinogenic effects and negative effects on reproduction. These substances, with the exception of PCBs, are formed unintentionally as by-products of industrial and thermal processes. One of the main sources of dioxin-like chemicals is medical waste incinerators. In this project the area surrounding a medical waste incinerator was monitored using a bio-assay technique. The determination of dioxin concentrations is usually preformed by chemical analysis, however, bio-assays have proven themselves to be a cheaper and time-saving screening method. The Toxic Equivalency Quotient (TEQs) determined through bio-assays can support chemical analysis in determining biologically-relevant risk assessments since bio-assay data has ecotoxicological relevance. These assays represent an integrated biological response to chemical pollutants, where biological effects are accounted for which is not possible in chemical analyses. One of the bio-assays used in the determination of the dioxin-like chemical TEQ is the H411 E reporter gene bio-assay. This assay is based on the Ah-receptor mediated toxicity of dioxin-like chemicals. Using this technique the TEQs for areas surrounding an active incinerator were determined, to indicate the distribution of these substances. The TEQs for the soil samples collected ranged between nondetectable and 154 ngTEQ/kg. There was no clear distributional pattern and the total organic carbon content in the soil did not seem to play a crucial role in the distribution of dioxin-like chemicals. Although a decrease in soil tillage showed a corresponding increase in TEQ. The predominant wind direction was taken into account but no correlation could be seen. However, meteorological parameters such as the ambient temperature and low precipitation in the area may have contributed to lower TEQ values. Cytotoxicity excluded data points and the phenomenon has to be addressed. High TEQ values in a residential area where free-range chickens are raised pose a serious concern to the level of dietary dioxin-like chemical intake. Eggs in the area could theoretically contain between 2.75 and 28.75 pgTEQ/g egg fat. Further studies are needed to determine how much dioxin-like chemicals are being transferred to humans through the consumption of free-range eggs / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2006.

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