Siga este link para ver outros tipos de publicações sobre o tema: Lead.
Teses / dissertações sobre o tema "Lead"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Lead".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
1
Lydon, P. "The simultaneous electrodeposition of lead and lead dioxide". Thesis, London Metropolitan University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373911.
Texto completo da fonte
2
Zubikarai, Iturralde Nerea. "Lean management´s impact on lead time of ETO processes". Thesis, Tekniska Högskolan, Jönköping University, JTH, Industriell produktutveckling, produktion och design, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-50590.
Texto completo da fonteResumo:
Lean management is considered a key to lead time reduction while being efficient, in order to survive in the actual market. Despite this, there is relatively little research done about implementation of lean management in ETO processes. Knowing that ETO processes are a reality in the industry, because there is a demand of customized products in the market. Nonetheless, the early phases of the ETO processes are critical. The purpose of this study was therefore to investigate how lean management can be used to understand and early phases of ETO processes, in order to evaluate potential lead time reduction. Analysing issues that arise when implementing lean in this kind of processes, such as variety, variation and standardization. The empirical data was collected from two different companies with ETO processes on different stages of lean implementation. A theoretical background in the area is supported by a comparison of the historical development and current state of two companies. The access to these two companies provides a view of the state before lean implementation and during implementation, and also a brief view of the effects. This helps to understand how lean management could be implemented in ETO processes. As a result, this research describes what should be considered when implementing lean management in early phases of ETO processes and what the effect of this implementation could be.
3
Mohammadi, Abdulreza Tabe. "Electrochemistry of lead and lead alloy anodes in lead-acid batteries for photovoltaic energy storage". Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7884.
Texto completo da fonteResumo:
The performance of lead-acid batteries for energy storage in photovoltaic/diesel/battery hybrid systems strongly depends on several electrochemical and/or operational factors such as the alloying elements incorporated in the electrode plates, the addition of expander materials to the anode or to the electrolyte, temperature, and the charging regime of the battery. In this study, the influences of the above mentioned factors on battery performance were investigated using cyclic voltammetry and potentiostatic transient techniques supplemented by surface analysis techniques including scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). The behaviour of binary lead-calcium and lead-antimony, and ternary lead-calcium-tin and lead-antimony-selenium alloy anodes were compared to that of the pure lead anode. In addition, the effect of ammonium ligno-sulphonate (ALS), as an expander added to the electrolyte, on the anode behaviour, was studied at room (23$\sp\circ$C) and cold (0$\sp\circ$C) temperatures.
4
Fleming, David E. B. "Human lead metabolism : chronic exposure, bone lead and physiological models /". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/NQ42735.pdf.
Texto completo da fonte
5
Hendricks, Warren Charles. "Metallorganic chemical vapor deposition of lead oxide and lead titanate". Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/41492.
Texto completo da fonteResumo:
The purpose of this study was two-fold: firstly, the MOCVD deposition behavior
of Pb(thd)2 was studied in detail and a one-dimensional kinetic model was proposed to
successfully predict the effect of processing conditions on the deposition rate profile for
PbO. Assuming the surface reaction is the rate-limiting step in the process, the effective
activation energy for the process, Ea, was found to be 82 kJ/mol while the
preexponential rate constant was found to be 33 g/cm2/min (0.15 moVcm2/min). The
process was found to consistently produce a combination of the high temperature,
orthorhombic modification of lead monoxide with randomly oriented plates of tetragonal
lead monoxide. TEM electron diffraction was used to investigate the crystal orientation of
the individual plates which was found to be in the plane normal to the <201> zone.
Secondly, the deposition behavior of PbTi03 and the resulting film structure and
properties were investigated. Pb(thd)2 was used in conjunction with titanium ethoxide
(Ti(OEt)4) as a titanium source. Stoichiometric lead titanate films which were found to be
smooth, specular and transparent, and well-adhered were deposited on a variety of
substrates by careful control of the experimental conditions. Film structure, composition,
and thickness were studied and correlated to changes in various experimental parameters.
Additionally, a high temperature regime at which the film stoichiometry is relatively
insensitive to experimental conditions was found to occur. The effects of post-annealing
on the as-deposited films including compositional changes, morphological changes and
crystal structure was also studied. Some problems were obtained with film peeling on the
ruthenium oxide (Ru02)-coated substrates which could be alleviated somewhat by the use
of (100) oriented silicon wafer rather than (111) oriented silicon; a possible mechanism to
explain this behavior is also suggested. Optical properties were obtained using UV -VISNIR
transmission and reflectance spectroscopy; the ferroelectric hysteresis behavior of the
films was observed using standard R T -66 A test equipment.
Master of Science
6
Holt, Adrian C. "The intestinal absorption of lead: the importance of lead speciation". Thesis, Aston University, 1988. http://publications.aston.ac.uk/14519/.
Texto completo da fonte
7
Schlesinger, Mark E. "LEAD OXIDE SOLUBILITY IN LEAD BLAST-FURNACE SLAGS (ACTIVITY, THERMODYNAMICS)". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291261.
Texto completo da fonte
8
Aronoff, Leya. "Dynamic Motivation to Lead: Construct Validity of Motivation to Lead". Scholarship @ Claremont, 2019. https://scholarship.claremont.edu/cmc_theses/2254.
Texto completo da fonteResumo:
Although motivation to lead (MTL) was characterized as stable, recent research suggested otherwise. This study explored the malleability of MTL and its predictors. Individuals with high affective-identity MTL are motivated to lead because they enjoy leading. Individuals with high social normative MTL are motivated by an obligation to lead. Individuals with high noncalculative MTL are drawn to leadership because they avoid weighing the costs and benefits of leading. Applicants to a California college were sent a questionnaire on MTL and leadership self-efficacy (LSE) (Time 1 assessment, N = 2704). Four years later (Time 2), participants who responded at Time 1 were sent a survey on motivation to lead, leadership self-efficacy, college leadership experience, and leader identity (LID) (N = 96). Results showed that participants’ affective-identity and noncalculative MTL have decreased over time. Leadership self-efficacy at Time 2 and leader identity at Time 2 were related to the changes in all 3 categories of MTL. Only specific college leadership experiences related to changes in affective-identity MTL. Lastly, leader identity at Time 2 mediated the relationship between affective-identity MTL at Time 1 and Time 2. Most high school students applied to college aspiring to be leaders, but only students who cultivate their leader identity should continue to be motivated to lead. Implications are discussed in the context of the construct validity of MTL, specifically for student leadership development in higher education.
9
ZHANG, BAOWEI. "Surface Chemistry of Lead and Lead Free Metal Halide Nanocrystals". Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1071937.
Texto completo da fonteResumo:
In this thesis, the surface chemistry of different metal halide NCs were investigated. Two new synthesis approaches to produce LHP NCs were developed by employing phosphonic acids (either alkyl or oleyl PAs) as the sole surfactants. The NMR analysis of these samples indicated the steric binding state of PA. PA-capped NCs show near unity PLQY with uncommon truncated shape, and high stability against dilution. We also investigated the interaction between neutral ligands and LHP NCs. Among various neutral ligands, it was found out that oleyl PAs are able to strip a large fraction of original surface species. Surprisingly, after such loss of ligands, the PLQY, morphology and phase of CsPbBr3 NCs remain unaltered, empirically confirming the defect tolerance of LHP NCs. We also studied the surface chemistry of Pb-free double perovskite NCs. We optimized the optical properties of Bi-doped Cs2(NaxAg1-x)InCl6 NCs by systematically varying the amine and acid. We found out that both ligands are anchored to the surface of the NCs. Moreover, we observed that even with a high ligands density, the PLQY of the NCs was still low indicating that ‘normal’ surface passivation is not enough to efficiently passivate these NCs, which suggest that such DP NCs is sensitivity to non-radiative surface traps. We also investigated the optical physical behavior of Sb3+ centers in different coordination environment. The Rb7Sb3Cl16 NCs were composed by isolated [SbCl6]3- octahedra and [Sb2Cl10]4- dimer. The isolated [SbCl6]3- octahedra show dual emission under different excitation, whereas the [Sb2Cl10]4- dimer is non-emissive even in cryogenic temperature. In the final part, we have investigated a special LHP species, so called nanoclusters (NCLs), which was regard as intermediate between molecular precursors and solid LHP NCs. We here firstly revealed their shape and structure by SXAX, WAXS and PDF analysis.
10
Still, Michael Charles William. "Roman lead sealings". Thesis, University College London (University of London), 1995. http://discovery.ucl.ac.uk/1317870/.
Texto completo da fonteResumo:
This thesis is based on a catalogue of c.1800 records, covering over 2000 examples of Roman lead sealings, many previously unpublished. The catalogue is provided with indices of inscriptions and of anepigraphic designs, and subsidiary indices of places, military units, private individuals and emperors mentioned on the sealings. The main part of the thesis commences with a history of the use of lead sealings outside of the Roman period, which is followed by a new typology (the first since c.1900) which puts special emphasis on the use of form as a guide to dating. The next group of chapters examine the evidence for use of the different categories of sealings, i.e. Imperial, Official, Taxation, Provincial, Civic, Military and Miscellaneous. This includes evidence from impressions, form, texture of reverse, association with findspot and any literary references which may help. The next chapter compares distances travelled by similar sealings and looks at the widespread distribution of identical sealings of which the origin is unknown. The first statistical chapter covers imperial sealings. These can be assigned to certain periods and can thus be subjected to the type of analysis usually reserved for coins. The second statistical chapter looks at the division of categories of sealings within each province. The sealings in each category within each province are calculated as percentages of the provincial total and are then compared with an adjusted percentage for that category in the whole of the empire. The final chapter is based on the iconography found in the impressions on the sealings. This includes the styles of imperial portraits, deities, animals, inanimate objects, designs which may come from outside of the empire, similar impressions on other items, epigraphic styles and possible examples of matrices.
11
Halici, Safak. "Development Of Lead Alloys For Valve-regulated Lead-acid (vrla) Batteries". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612422/index.pdf.
Texto completo da fonteResumo:
In this study, Mg, Sn, Cd, Bi and Sb containing, five binary, three ternary and two quaternary different alloys to be used in a Valve-Regulated Lead-Acid (VRLA) batteries have been studied in terms of their mechanical and electrochemical properties. The investigated properties are hardness, passivity, corrosion rate, hydrogen gassing and the conductivity of the passive film. All electrochemical tests were carried out in 3.75 M H2SO4 solution by using open-circuit potential, anodic polarization, polarization resistance measurement and gas collection techniques.
The results showed that while the minimum hardness values were observed in Pb and Pb-Bi alloy, Mg containing alloys have the highest hardness values among all alloys. According to corrosion measurements, lowest icritical value was obtained for Pb, Pb-Bi and Pb-Sn, which reached to passivation region earlier than others. Passive film formation was seen for all specimens. The noble Ecorr value and minimum corrosion rates belonged to Pb and Pb-Mg. Pb-Bi and Pb-Cd have the highest gas evolution rate. Besides, there were not seen much difference in the gassing behavior of Pb-Sn and Pb-Sb alloys. Mg is found to have a superior effect on hydrogen gassing. Addition of Sn, as an alloying element, to lead increases the conductivity of the passivation layer. Mg containing alloys did not show good conductivity characteristic. As a result, Mg containing alloy seemed to have an important role because of the desired hardness, corrosion and, gas evolution behavior. However, conductivity of passivation layer of these alloys came up to be low due to the higher tendency of Mg to oxidation. Even so, Mg seems to be a promising alloying element for lead grid alloys in Valve-Regulated Lead-Acid (VRLA) batteries.
12
Schreier, Martin, e Reinhard Wilhelm Prügl. "Extending lead user theory: Antecedents and consequences of consumers' lead userness". Wiley-Blackwell, 2008. http://dx.doi.org/10.1111/j.1540-5885.2008.00305.x.
Texto completo da fonteResumo:
Lead users have been shown to be a highly promising source of innovation for generating
radical new product ideas. According to lead user theory, these users are defined as being
ahead of an important market trend and experiencing high benefits from innovating. There is
strong empirical support that these users tend to come up with commercially attractive user
innovations. Other than that, however, there is hardly any knowledge available which helps to
describe and differentiate this "species" of user from more "ordinary" users. The present
article aims to fill this gap and extends lead user theory by exploring some antecedents and
consequences of consumers' "lead userness". As regards antecedents, it is argued that a
consumer's leading-edge status will depend on field-related as well as field-independent
variables. First, it is hypothesized that a consumer's basis of knowledge and use experience
gained in the underlying field will help explain one's lead userness. Second, it is hypothesized
that the two general personality traits of "locus of control" and "innovativeness" will be
related to users' leading-edge status in a given domain. As regards consequences, this article
develops a link between individuals' lead userness and new product adoption behavior. It is
hypothesized that lead users will demonstrate innovative behavior not only by innovating on
their own, but also by adopting new products faster and more intensively. These tenets are
tested in the course of three studies on extreme sports communities (sailplaners [n=129],
technical divers [n=193], and kite surfers [n=139]). Overall, findings are throughout
affirmative. First, it is found that the proposed antecedents (both field-related as well as both
field-independent variables) are strongly related to consumer's lead userness. These findings
have important implications: One major challenge of the lead user method has been the
reliable and efficient identification of leading-edge users in the first place. Findings related to
antecedents suggest that these variables might be employed to improve the lead user search
process - they might be used as a proxy to identify the rare "species" of lead users. Second,
also the proposed consequence of being a lead user finds strong empirical support: Lead user
tend to adopt new products faster and more intensively than other users. These findings
suggest that lead users might be highly valuable to companies beyond the fuzzy front end of
generating radically new product ideas. Lead users might also be relevant to more general
product development and marketing issues. For example, they might be integrated into new
product concept testing methods and "lead userness" might serve as an additional positioning
variable for the marketing of new products. (authors' abstract)
13
Zhou, Hengrui, e 周恆瑞. "Synthesis and characterization of lead compounds in waste lead battery treatment". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2015. http://hdl.handle.net/10722/212611.
Texto completo da fonte
14
Nell, Michael Paul. "Lead user screening and testing of lead user generated product concepts". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15122.
Texto completo da fonte
15
French, Kyle J. "Growth of Optical Quality Lead Magnesium Niobate-Lead Titanate Thick Films". University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1575993750125728.
Texto completo da fonte
16
Luke, Colin G. "A study of factors associated with trends in blood lead levels in Port Pirie children exposed to home-based interventions /". Title page, contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09MPM/09mpml954.pdf.
Texto completo da fonte
17
Stålnacke, Emil. "Microstructure-corrosion interrelations in new low-lead and lead-free brass alloys". Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217355.
Texto completo da fonteResumo:
In new low-lead and lead-free brass alloys, it is not understood how the corrosion properties,such as dezincification, are related to material composition as well as annealing temperatureand duration. This study aims to fill this knowledge gap by mapping sixteen annealingconditions and three different brass alloy compositions to their respective microstructure anddezincification performance. It was found that high dezincification depth was a result ofannealing temperatures at 300°C – 400°C, which promoted precipitation of intermetallicAlAs-particles along grain boundaries, twins and lead particles as well as precipitation of β-phase along grain boundaries. Their presence was correlated to high micro additions ofaluminium or iron in the material composition. An additional compositional factorcontributing to precipitation of high amount of β-phase was low copper/zinc-ratio.
18
Thiagarajan, Suraj Joottu. "Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites". Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196263620.
Texto completo da fonte
19
Thompson, Jessica Ann. "Determining the concentration and source of lead in chocolate using lead isotopes". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/114339.
Texto completo da fonteResumo:
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2007.Cataloged from PDF version of thesis. Pages 81 and 87 missing from original thesis.
Includes bibliographical references (pages 86-91).
Single-origin dark chocolate samples derived from cocoa grown in developing countries from around the world were analyzed to determine their lead concentrations and the isotopic composition of the lead. The lead isotope ratios were compared with published data from aerosols and volcanic rocks nearest to the cocoa growing regions. Samples from different countries and manufacturers were compared, and we conclude that the source of lead depends on the country of origin and not the manufacturer. Chocolates grown in the Northern Hemisphere usually had lead isotope ratios that matched the global atmospheric lead isotopic signature from the Northern Hemisphere. Chocolates grown in the Southern Hemisphere did not match the global signature, but rather more closely matched the lead isotopic signature from volcanic rocks in their respective countries, and had a lower average lead concentration than chocolates from the Northern Hemisphere. Soils from Venezuela were also analyzed, and confirmed the conclusion that atmospheric lead is the predominant source of bioavailable lead. Many of the chocolates also had lead concentrations below the limit of 0.1 ppm set by the FDA; however, one manufacturer, Dagoba, consistently had lead concentrations above the limit. The percent of cocoa in each chocolate bar was also compared with the lead concentrations, concluding that the concentration of lead is not necessarily dependent on the amount of cocoa in the bar.
by Jessica A. Thompson.
S.B.
20
Thiagarajan, Suraj Joottu. "Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites". The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1196263620.
Texto completo da fonte
21
Weaver, Cameron L. "Lead silicate solubility and the control of lead contamination in drinking water". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07112009-040433/.
Texto completo da fonte
22
Zhu, Zangyuan. "Lead-free piezoelectric ceramics". Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581971.
Texto completo da fonteResumo:
Legislation arising from health and environmental concerns has intensified research into finding suitable alternatives to lead-based electroceramics. Lead zirconate titanate (PZT) has been developed over several decades to become the market-leading piezoelectric ceramic. Lead-free solid solutions based on sodium potassium niobate, Na0.5K0.5NbO3 (NKN), show promising dielectric and piezoelectric properties. 1-2 The related (l-x)( Na0.5K0.5NbO3)-xBiScO3 binary system (NKN-BS) has been reported to exhibit maximum d33 values of 200 pCIN at 2 mol% BS.3 Similarly, an optimal d33 value has been reported for the binary NKN-LT system at 5-6 mol% LiTa03.4 In this work, a series of compositions along the compositional join in the ternary NKN-LT-BS system, extending from 0. Na0.5K0.5NbO3 -0.02BiScO3 toward LiTa03 have been prepared and characterized. A 0.98[0.98NKN - 0.02(LiTaO3)] - 0.02[BiScO3] (NKN- 2L T -2BS) composition showed enhanced piezoelectric properties, relative to similar compositions, with d33 values of 215 pCIN. This can be attributed to a phase content of mixed orthorhombic (or monoclinic) and tetragonal phases at ambient temperatures. Variable temperature X-ray diffraction (XRD), and dielectric measurements as a function of temperature, indicated phase transitions (on heating) from an orthorhombic (or monoclinic) crystal system to tetragonal and then cubic crystal systems at ~25°C and ~370°C respectively. Different types of dielectric behaviour were observed on increasing the LT content. A NKN-5%LT-2%BS composition exhibited twin dielectric peaks at high temperatures (~370°C and ~470°C), along with broad X-ray diffraction peaks and a fine grain size, < 0.5 μm. The twin dielectric peaks suggest that chemical inhomogeneities may have been present; this was examined using transmission electron microscopy (TEM) with energy dispersive X-ray analysis (EDX). Elemental segregation was observed within individual grains, such that a core-shell grain structure was evident. The twin high temperature dielectric peaks are attributed to the separate response from the core and shell regions, each of which have a characteristic Curie temperature range. Subsequently, a series of other compositions were prepared in the wider Na0.5K0.5NbO3 - LiTaO3-BiScO3 ternary system. Considering the combined data from XRD, dielectric measurements, SEM, TEM and piezoelectric properties for a wide range of compositions within the NKN-rich region of the NKN-LT-BS system, materials may be grouped into three categories, exhibiting the following defining characteristics. Type I: single, sharp dielectric Curie peak (~ 370°C); single phase by XRD; large grain size (5-10μm); chemically uniform by TEM-EDX. Type II: broad, single dielectric peak (~ 350°C); single phase by XRD; large grain size; no obvious chemical segregation. Type Ila: twin, broad dielectric peak(s) (~ 370°C and ~ 470°C); broad XRD peaks; small grain size (~ O.5μm); chemical segregation (core-shell structure) identified by TEM-EDX. Reasons for the properties of these three classes of material are discussed; comparisons are drawn with other lead-free dielectrics and piezoelectrics; finally, the potential of the materials in future device applications are considered.
23
Weller, Sean David Tomey. "Lead-free solder technology". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/5575/.
Texto completo da fonteResumo:
Aerospace applications typically require electronic products with not only higher levels of reliability than the consumer electronics industry but also longer service lives within demanding working environments. The transition will inevitably mean changes to design and manufacturing procedures, which is likely to incur a significant cost to the business. For example, the best candidate Pb-free solder alloys have been shown to require higher soldering temperatures and have higher surface tensions. Moreover, a reduction in product safety and reliability is not acceptable to the industry. This present work is divided into three sections. Firstly, the effect of increased component soldering temperatures on the integrity of the epoxy laminate material used for manufacture of printed circuit boards (PCB) has been assessed. Secondly, the required changes in soldering process parameters have been investigated for a range of solders and PCB finishes, largely due to the different wetting characteristics brought about by the increased surface tension of the Pb-free solders. Thirdly, the reliability of SnAgCu solder is assessed in comparison to the currently utilised SnPbAg solder alloy. This has been achieved firstly by accelerated thermal cycling, as the dominant mode of failure in a solder joint is typically thermo-mechanical fatigue and as such is already well researched. In addition, the mechanical fatigue properties have been assessed using a novel accelerated vibration test method and then finally, the two individual accelerated environmental tests of thermal cycling and vibration have been combined in a novel way to assess whether the combination is especially dangerous for SnAgCu solder reliability. A secondary objective of the combined environment test was to see if the well established thermal cycling test method for demonstration of product reliability can be further accelerated while still producing solder joint failure representative of those in-service. The present work shows that SnAgCu solder has inferior thermo-mechanical and mechanical fatigue life to SnPbAg solder. A combined environment test has been developed which effectively combines the single environments of thermal and vibration. The combination of thermal cycling with superimposed vibration is especially dangerous for SnAgCu solder, where an 89% reduction in the characteristic life is observed when compared to the equivalent thermal cycling characteristic life. It is suspected that a large reduction in life will be observed in SnPbAg solder, but not as pronounced as SnAgCu due to SnPbAg solders ability to better withstand plastic deformation that is induced by thermal cycling.
24
Jacox, Laura (Laura A. ). "Molecular toxicity of lead". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/114343.
Texto completo da fonteResumo:
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2008.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 23-28).
Introduction - Lead is a heavy metal that has been in use for over 8000 years (White, 2007). It was first smelted it 4000BC as a byproduct of silver processing. Since then, Pb has played a dynamic role in history, possibly contributing to the fall of the Roman Empire (Nraigu, 1983). Pb is a highly malleable and ductile Group IVa metal. It has been utilized in a variety of products including makeup, water pipes, cooking vessels, wine bottle seals, glass, batteries, solder, electronic components, paint, and antiknock fuel additives (White, 2007). Its prevalent, long-term use has distributed anthropogenic Pb across the planet in soil, air-borne dust, and water (White, 2007). As a result, human exposure can occur via inhaled air, dust, food, and drinking water. Pb has no known biological functions, yet it has numerous detrimental effects on the body, several of which have been recognized for millennia.
by Laura Jacox.
S.B.
25
Birdwell, Kent N. "The Global Lead Programme". Thesis, Stellenbosch : Stellenbosch University, 2006. http://hdl.handle.net/10019.1/20892.
Texto completo da fonteResumo:
Thesis (MBA)--Stellenbosch University, 2006.This study project sets out to examine the validity of an idea - an idea to create a study-abroad programme complemented by combining studies with mission work for Christian university undergraduates. In support of this idea, this study researches the overwhelming arguments that would validate the programme. The study then looks into how the programme can be designed and what its desired focus should be. In this study, the author first examines the prominent external forces that justify the programmes' needs. Two prominent forces include the lack of valued, quality leadership roles in today's business community, as well as the coming of a more integrated world where business managers must gain the skills to transact beyond borders. These two forces become the focal point of the education component, while the last external issue examined explores the business mission possibilities for southern Africa. The study then delves to understand how business schools are adapting to the issues of teaching leadership skills and the ability to transact beyond borders. The author finds that even though many schools have responded by adding soft skill courses such as leadership or internationalising their student bodies and curricula, many organisations are still reporting the lack of quality global leaders. With this, many organisations are creating Corporate Universities where they themselves educate their employees through the use of Action Based Learning (ABL). The author thus believes this ABL concept is a most effective tool in not only training for specific functions of business, but also in tacitly improving the soft skills of business management, which is becoming important for today's global leaders. Knowing these external and internal issues, the author studies the potential of such a programme by analysing a Christian university's existing curriculum and ABL missions structure, and then meets with prospective students, deans, professors, and administrators who may desire a programme that combines study abroad with mission work. The findings suggest that the focus of the programme narrow in on global based leadership education complemented with the use of Action Based Learning in the missions field to promote multidisciplined business missions. However, designing this Global Leadership Programme will require a model from which to begin. The author chose the Value Chain concept; however, Porter's (1985) Value Chain concept was thought to be too onerous for developing this short-term programme. The author then describes and illustrates the use of Sviokla and Rayport's Virtual Value Chain model (1994) and chose to use this model in designing the programme. As a result, the subsequent Chapters first establish direction by suggesting vision and mission statements and the Global Lead Programme objectives, and then research the content (what is offered) and context (how the content is offered) components of the model. In the end, the author concludes the study by offering insight into infrastructure (the enabler) considerations and options to enable the Global Lead Programme to grow and succeed.
26
Droessler, Laura Melanie. "Lead oxides for photovoltaics". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:8a0216a2-3efe-4de4-a853-d5b6ec53eeee.
Texto completo da fonteResumo:
This thesis investigates lead oxides as photovoltaic materials. Vacuum deposition methods and ex-situ annealing are used to produce different stoichiometries of lead oxide. The relationship between structure and the optoelectronic properties is then investigated. Following this, a number of photovoltaic devices are prototyped and a Kelvin probe used to determine and understand the band structure of devices. Thin films of PbO produced via air annealing of thermally evaporated lead consist of a mixture of two phases, orthorhombic and tetragonal, that determine the materials properties and effectiveness as absorber layer in a Schottky device. Films of higher tetragonal content are more photoactive, showing lower series resistance. Kelvin probe reveals that with an increasing work function of the PbO with increasing duration of the annealing, the Schottky barrier between PbO and Al increases, which results in a higher VOC. This trend is inverted when the Fermi level of PbO drops below that of ITO, creating an opposing junction. Reactively sputtered PbO2 films are highly conductive degenerate semiconductors. Increasing oxygen flow rate during deposition leads to increased resistivity and decreased mobility, resulting from a decrease in grain size. Alongside this an increase in carrier concentration is observed as the material gets less ordered at higher oxygen flow rates, which results in an increase in Fermi level. Due to its high conductivity the material is not photoactive, and the high work function between -5.6 and -5.8 eV does not allow the formation of a Schottky junction or a p-n junction with the evaporated p- type PbO. Post deposition annealing of the sputtered films leads to the formation of the more resistive Pb3O4 phase. This material shows lower carrier concentration and mobility, however, work functions are similarly high. The changes induced by the heat treatment are not substantial enough to be able to create a junction between the as-deposited and the annealed material, as is revealed by Kelvin probe and Hall Effect measurements. Heterojunctions between P3HT and Pb3O4 were made to test predictions made by KP measurements. A heat treatment on P3HT improved its electronic properties and raised the Fermi level, resulting in the transformation of a diode in to a photovoltaic device and a decrease in dark current.
27
Foley, Daniel Jason. "Realising lead-oriented synthesis". Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9222/.
Texto completo da fonteResumo:
The concept of lead-oriented synthesis (LOS) seeks to address to the paucity of diverse compounds with appropriate properties for biological screening. This thesis focuses on the preparation of diverse scaffolds, which, following decoration, may provide access to lead-like compounds. Key polyfunctionalised building blocks were prepared to enable the synthesis of such scaffolds by applying small tool-kits of robust synthetic methodologies. Computational tools were used to guide the development of key methodologies and to target the preparation of specific scaffolds. In addition, computational tools were used to retrospectively analyse the ability of the scaffolds prepared to provide access to lead-like space. Chapter 1 discusses ideal molecular properties for drugs and leads, modern synthetic approaches to the preparation of diverse screening compounds, and the emergence of LOS as a concept to resolve the challenge of sourcing large numbers of ideal screening compounds. Chapter 2 details the preparation of small polyfunctionalised building blocks through the allylation of amino acid-derivatives. A building-up (‘bottom-up’) approach was used to prepare scaffolds, exploiting the intramolecular capture of pendant nucleophiles at alkene or ester functionalities, and the use of transition metal-catalysed cyclisations. Four building blocks were used to prepare 22 scaffolds. A virtual library of 1110 compounds was enumerated from the scaffolds, of which 66% were found to be lead-like. Chapter 3 describes the preparation of larger polycycles using an intramolecular [5+2] oxidopyrylium cycloaddition. The two polycyclic assemblies prepared were deconstructed using a ‘top-down’ approach to give six scaffolds. A virtual library of 798 compounds was enumerated from the scaffolds, of which 72% would be lead-like. Chapter 4 compares the value of the different LOS approaches developed, this considers the ability of the scaffolds to provide access to lead-like space, their three-dimensionality, and the synthetic economy of their preparation.
28
Anson, Scott J. "Analysis of lead free tin-silver-copper and tin-lead solder wetting reactions". Diss., Online access via UMI:, 2007.
Encontre o texto completo da fonte
29
Neiström, Linda. "Characterisation of Used Lead-Acid Batteries for Feed Optimisation in Secondary Lead Production". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70740.
Texto completo da fonteResumo:
Used lead-acid batteries are the main raw material in secondary lead production. Technologicalprogress in the car industry, have raised concerns regarding the lead-acid battery’s leading positionas electrochemical storage system in the future. However, the lead-acid battery industry isadvancing with innovations, such as hybrid and micro-hybrid vehicles, and is believed to have acontinued important role in the rechargeable battery market. Lead is one of the most investigatedmetal due to concerns from society regarding the negative effect on human health and theenvironment. Consequently, that has led to tighter controls and regulations of the lead processingindustry which, in turn, has led to technological improvement concerning design and operation ofthe lead processing plants. Used lead-acid batteries have a complex composition with a variety ofcomponents made of lead (i.e., metallic, oxide or sulphate) and non-lead materials (plastics andelectrolyte). Traditionally, battery recycling is done without separating those components.However, to optimise the use of resources and decrease the environmental impact of secondarylead production, a pre-treatment step to the batteries recycling is desired. The pre-treatment iscomprised of breaking the batteries and separation of the battery components. The aim of the present thesis, was to study the components of a used lead-acid battery, which willbe the outgoing material of a future plastic separation plant at Boliden Bergsöe, and their effect onthe process. Furthermore, the study aimed at investigating the possibilities to adjust the feedcomposition for further process optimisation and improvement of the process quality in terms ofenergy usages and environmental impact. This was done by characterise, through qualitative andquantitative composition and mass distribution, the fractions in a used lead-acid car battery. Four lead-acid car batteries were provided for dismantling to study mass distribution, and toliberate the components for further analysis. The analytical techniques used in this study werequalitative and quantitative (Rietveld) XRD analysis, SEM-EDS and TGA. The result showed thatoverestimated amount of battery separators (PE) has been used at production planning in energyandemission calculations, which can cause financial losses due to overpaid emission tax. The pastefraction showed a large variation in mass between the studied batteries and consists mostly ofPbSO4. Large variation in the paste mass may cause uneven sulphur emission from smelter.Consequently, this reinforces the need for implementation of the separation of the battery feed fora better control of the paste addition to the smelter. When PE decomposes in the shaft furnace the remaining ash will mainly consist of silica, whichwill affect the sulphur uptake in the shaft furnace. The large content of silica leads to a lower energycontribution to the process; however, a lower content of hydrocarbons leads to lower CO2emissions. If a desulphurisation of the pastes would be implemented, it is believed to affect theprocess through a decreased need of coke and iron. A reduced usage of coke and iron would lowerthe production costs and lead to decreased CO2 emissions. A desulphurisation will also decreasethe lead sulphate content in the feed, thus lead to better control of the sulphur emissions. This study provides additional support and further insight into composition and mass distributionof the components in a lead-acid battery. Furthermore, the study indicates possible impact of thefuture separation on the new feed properties and on the subsequent processing.
30
Stinson-Bagby, Kelly Lucile. "Microstructural Evolution in Thermally Cycled Large-Area Lead and Lead-Free Solder Joints". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34573.
Texto completo da fonteResumo:
Currently, there are two major driving forces for considering alternative materials to lead-
based products, specifically interconnections, in electronics applications, including the
impending legislation or regulations which may tax, restrict, or eliminate the use of lead
and the trend toward advanced interconnection technology, which may challenge the
limits of present soldering technology. The reliability of solder joints is a concern
because fracture failures in solder joints accounts for 70% of failures in electronic
components. Lead-free solders are being investigated as replacements for lead solders
currently used in electronics. Thermo-mechanical properties describe the stresses
accumulated due to thermal fatigue as a result of CTE mismatch within the system. By
understanding the failure mechanisms related to lead-free solders, the application of lead-
free solders could be more strategically designed for specific applications.
The objective of this thesis is to observe microstructural change in large-area solder joints
caused by thermal cycling and relate these changes to reliability issues in large-area lead
and lead-free solder constructed semiconductor power devices. This study focused on the
microstructural changes within the solder alloy of a large-area solder joint under thermal
cycling conditions. Two major primary observations were made from this research, they
are: 1) due to a combination of testing conditions and material properties, the lead-free
solders, Sn/3.5Ag and Sn/Ag/0.7Cu, sustained the most severe damage as compared to
Sn/37Pb, and 2) due to elevated stresses at the solder/substrate interface in a simulated
power semiconductor device sample damage was found to be most severe.Master of Science
31
Joshi, Rahul V. "Thermo-mechanical behavior of tin-lead and lead-free ceramic column grid array packages". Diss., Online access via UMI:, 2005.
Encontre o texto completo da fonte
32
Jönsson, Johanna, e Melinda Luong. "Reducing Supplier Lead Time : - A case study on Supplier Lead Time at purchasing companies". Thesis, Linnéuniversitetet, Institutionen för ekonomistyrning och logistik (ELO), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-48474.
Texto completo da fonteResumo:
Title: Reducing Supplier Lead time – a case study on Supplier Lead Time at purchasing companies Authors: Johanna Jönsson and Melinda Luong Tutor: Dr. Åsa Gustavsson Examiner: Dr. Lars-Olof Rask Course code: 4FE06E - Master Thesis _________________________________________________________________________ Research questions: ● How are companies working with and defining Supplier Lead Time? ● What activities are included to reduce Supplier Lead Time? ● How can companies further develop their work to reduce Supplier Lead Time? Purpose: The purpose of this Master Thesis is to describe and explain how purchasing companies are working to reduce Supplier Lead Time, in order to maintain or achieve an efficient and flexible supply chain. Moreover the study aims to recommend what approaches companies could further use to reduce Supplier Lead time. Method: To answer these research questions the authors have done two case studies. The theoretical material has been collected and processed, which has formed the basis for the semi-structured interview guide that was answered by the interviewees. The authors also attended meetings to get other inputs about the subject. Conclusion: IKEA Components are today taking different actions to improve the SLT but can improve their volume agreements (AGV) by aligning all involved parts and have a functional leader that makes sure that they follow it up. At IKEA IMS the authors recommend them to work with volume commitments with suppliers and develop a clearer structure for who is responsible for improving the SLT and evaluating it. Keywords Supply chain management, Supplier Lead Time, Reducing Supplier Lead Time, Organization management, Performance evaluation
33
Manmee, Charuwan. "Lead levels in teeth as a measure of life-time lead exposure in children". Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2177.
Texto completo da fonteResumo:
Background and aims Lead exposure has irreversible health effects in children who are susceptible even at very low levels of exposure. The usual test for lead exposure is blood lead level (BLL), but this indicates only recent exposure. This study aimed to ascertain the suitability of milk teeth as biomarker of the history of lead exposure and to develop a methodology for this novel biomarker. Methods My study comprised three stages: Firstly, I explored potential determinants of dentine lead levels (DLLs) in children living in Newcastle upon Tyne (the Tooth Fairy Study). Secondly, I developed a methodology for assessing the history of early life lead exposure using dentine, and thirdly I applied my methodology to newly extracted teeth from children in Teesside. The Tooth Fairy study cohort consisted of 69 children aged 5-8 years. DLLs were measured in primary dentine using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). To identify determinants of early life exposure, a questionnaire was used. I assessed associations between lifestyle characteristics and DLLs. As teeth develop chronologically they offer the opportunity to study histories of exposure in detail. I collected two deciduous molars each from 15 children aged 6-8 years living in Northeast England. By combining high spatial resolution LA-ICP-MS with dental histology, I acquired information on the age specific concentrations of lead in dentine from in utero to several years after birth. Results Dentine lead levels in the Tooth Fairy cohort ranged from 0.06 to 0.77μg/g, median 0.21μg/g. Unlike other studies, I did not find significant associations between socio-economic status or other possible determinants and lead exposure. In developing the biomarker I found that the 100 micron ablation pit represented 42 days of dentine growth, enabling me to assign an age interval to each ablation pit. I found lead ratios in primary dentine to be consistent between teeth from the same child, and at the same age within each tooth. This indicated that the history of exposure can be determined using a single, multi-point ablation transect on high quality longitudinal sections of individual teeth. Conclusions I found no association between socio-economic status and dentine lead levels in a cohort of children from Newcastle upon Tyne. I developed a novel technique to date ablation points in dentine in milk teeth, and, using this technique have demonstrated that primary dentine is a potential biomarker for characterising the early life history of lead exposure in children.
34
Shimmield, Tracy Marjory. "A study of radionuclides, lead and lead isotope ratios in Scottish sea loch sediments". Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/9988.
Texto completo da fonteResumo:
This research involved the study of sediment cores from Loch Etive, Loch Long, Loch Goil and Loch Fyne with the aims of investigating the geochemistry of natural, and manmade radionuclides and heavy metals within the sea loch environment. The main aims of the research were to determine accumulation rates and the extent of mixing within these sediments and to assess the fluxes, sources and temporal variations in input of pollutant heavy metals to these environments. In recent years it has been suggested that Pb is mobile in sea loch sediments which questions the validity of applying ²¹⁰Pb dating in this environment. This has important implications with respect to interpreting sediment cores to assess temporal trends of pollutant inputs and investigating the rates of physical and biogeochemical processes that are taking place in the coastal environment. Hence, one of the aims of this research was to determine whether Pb was mobile in these sediments. The ²⁰⁶Pb/²⁰⁷Pb isotope ratio can potentially be used to determine the extent of pollutant Pb input from leaded petrol to the environment and a further objective of the work was to investigate the isotopic signature of pollutant Pb in the sediment. Concentration of ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁸U, ¹³⁷Cs, ¹³⁴Cs and ²⁴¹Am in the sediments were analysed using gamm a spectroscopy and the heavy metals, Pb, Zn and Cu were determined using X-ray Fluorescence. Stable Pb isotope ratios were determined using Inductively coupled plasma Mass spectrometry. The results obtained indicated that Pb is not subject to diagenetic mobility in these sediments and that ²¹⁰Pb profiles can be used to determine sedimentation rates for most of the sediment cores. lt was not possible to determine accumulation rates for the two cores from Loch Fyne by ²¹⁰Pb dating, and in this case the sedimentation rate was assessed by correlating the maximum concentration of ¹³⁷Cs in the sediments with the maximum ¹³⁷Cs discharge from Sellafield, BNFL's reprocessing plant located on the Cumbrian coast. The flux of ²¹⁰Pb to the lochs varied significantly suggesting that there has been sediment focusing of fine and/or organic rich material to the deeper sites, resulting in an enhanced flux of ²¹⁰Pb to these sediments. Sellafield waste radionuclides also provided useful chronologies by relating sediment maximum concentrations to maxima in the discharges. ¹³⁷Cs was observed to be subject to diffusive movement, invalidating the use of its total depth of penetration as a chronological indicator. The temporal trends of pollutant metal input agreed well with known historical trends and the Pb isotope profiles indicated that the onset of deposition from pollutant Pb from petrol occurred in the late 1920's. The maximum input of Pb from petrol peaked in the early 1980's and since then there has been a decrease in this input. The two sea lochs which were closest to the industrial centre of Glasgow exhibited a large anthropogenic pollutant input, confirming that these sediments have been highly perturbed by human activities, either directly as a result of sludge dumping or due to changes in land use (eg. road construction, deforestation, etc.) in the catchment. All the sea lochs reflected a change in the supply of material to the sediments over the last eighty years, indicating that increased anthropogenic activity has had an effect on these environments.
35
Challapalli, Dharmendra, e Ahmad El-masri. "Study and analysis of surface layer characteristics of lead brass and lead free brass". Thesis, Högskolan i Halmstad, Maskinteknisk produktframtagning (MTEK), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-32207.
Texto completo da fonteResumo:
The addition of lead to the copper alloys increase the machinability of thework material (without reference here to environmental factors) and reduces the overall production cost of the components at different stages, despite copper being expensive, which makes a challenging task to replace lead. Since lead is dangerous to human health. Many materials are considered to replace lead in brass and silicon is one of the alternative. This thesis characterizes the lead and the lead free brass's surfacemetallurgy for a certain cutting data. The study includes identification of alteredmaterial zones (AMZ) defined by the plastic deformation, hardness alterationsand grain distributions.The study results include the analysis of deformed subsurface region andcomparison exemplifying differences between the two materials under twodifferent studies.Lead free brass
36
Etminan, Ali. "Prediction of Lead Conversion With Imbalanced Data : A method based on Predictive Lead Scoring". Thesis, Linköpings universitet, Statistik och maskininlärning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-176433.
Texto completo da fonteResumo:
An ongoing challenge for most businesses is to filter out potential customers from their audience. This thesis proposes a method that takes advantage of user data to classify po- tential customers from random visitors to a website. The method is based on the Predictive Lead Scoring method that segments customers based on their likelihood of purchasing a product. Our method, however, aims to predict user conversion, that is predicting whether a user has the potential to become a customer or not. Six supervised machine learning models have been used to carry out the classifica- tion task. To account for the high imbalance in the input data, multiple resampling meth- ods have been applied to the training data. The combination of classifier and resampling method with the highest average precision score has been selected as the best model. In addition, this thesis tries to quantify the effect of feature weights by evaluating some feature ranking and weighting schemes. Using the schemes, several sets of weights have been produced and evaluated by training a KNN classifier on the weighted features. The change in average precision obtained from the original KNN (without weighting) is used as the reference for measuring the performance of ranking and weighting schemes.
37
Namboodri, Chettoor G. "Experimental investigation and modeling of the electrostrictive relaxor ferroelectric lead magnesium niobate-lead titinate". Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07212009-040304/.
Texto completo da fonte
38
Bergdahl, Ingvar A. "Lead in blood ICP-MS studies of lead in plasma, blood and erythrocyte proteins /". Lund : Dept. of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/39159416.html.
Texto completo da fonte
39
Dooley, Joan Mary 1961. "LEAD MOBILIZING ACTIVITY OF DMPS, DMSA, AND DMPA FOLLOWING ORGANIC AND INORGANIC LEAD EXPOSURE". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275507.
Texto completo da fonte
40
Haner, Andrew Lloyd. "Iola, Kansas residential lead contamination". Thesis, Wichita State University, 2007. http://hdl.handle.net/10057/1536.
Texto completo da fonteResumo:
In the late 1800’s and early 1900’s lead and zinc mining became prominent in Kansas, Oklahoma, and Missouri. With no knowledge of the effects that would impact the future, the mining companies continued to strip the land. With the discovery of lead and zinc ores in southeast Kansas, southwest Missouri, northeast Oklahoma in the late 1800’s a way to process the ores in a cheap way was needed. Natural gas in locations like Iola Kansas helped led to cheap ore processing and smelting. After the cheap fuel for the processing began to diminish in the early 1900’s, the multitude of smelters began to decrease. With the creation of the Environmental Protection Agency in 1970, concerns for the environment became a more than ever important issue. In the 1990’s, the EPA began to collect environmental impact data from areas potentially affected by mining, to access the effects of lead mining on residential areas in southeast Kansas and southwest Missouri. Thus, the methods of residential lead sampling were created. In Iola, Kansas the Kansas Department of Health and Environment performed tests to measure the extent that environmental impact from the smelters had on human residents of the town. With this evidence, the EPA was asked to conduct more testing, and to perform a cleanup of residential sites to help protect the environment and human health.Thesis [M.S]: Wichita State University, College of Liberal Arts and Science, Dept. of Geology
"December 2007."
41
Vineberg, Daryl Geoffrey. "A study of lead softening /". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80149.
Texto completo da fonteResumo:
Softening represents one of the stages in the pyrometallurgical refining of lead, in which oxygen is top-blown into a bath of impure bullion through a group of lances in order to preferentially oxidize arsenic, antimony and tin dissolved in the melt. The oxides of these species float to the melt surface, where they are removed as dross.It has been observed at Teck Cominco Lead Operations in Trail, BC that there is an "ignition temperature" in the range of 600°C, below which the softening reactions are reported to occur very slowly, if at all. Currently, disproportionately large efforts are made to initiate and sustain the softening process. This research was motivated by Teck Cominco's wish to have a clearer understanding of the ignition temperature phenomena, and a more robust and reliable process control.
Experimental trials were performed using a homemade thermogravimetric analyzer with a data acquisition system. The unit was constructed in such a way as to allow for simultaneous video recording of the sample surface, for future examination and reference.
42
Mossman, Susan. "Mycenaean Lead: Archaeology and Technology". Thesis, University of Birmingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508338.
Texto completo da fonte
43
Anjos, Mafalda Goulão Escaleira dos. "Philips Sweden - From led to lead". Master's thesis, 2014. http://hdl.handle.net/10362/21386.
Texto completo da fonte
44
曾琪婷. "Characterization of lead isotopes distribution of ingested lead dust from lead battery plant". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/81121335782714387771.
Texto completo da fonteResumo:
碩士國立臺灣大學
職業醫學與工業衛生研究所
88
The purpose of this study was to determine the bioavailability of ingested lead dust from a lead battery plant and changes in lead isotope composition in the blood. At the same time, this study tries to evaluate the possibility of distinguishing the lead exposure sources by examining isotope ratio changes. An animal experiment was performed with 5-6 weeks old male Sprague-Dawley rats. The rats of each experiment group were fed the mixture of AIN-76 semipurifed diet with various lead dusts from the assembly line of a lead battery plant. The target doses were 5mg Pb/kg BW/Day and 10 mg Pb/kg BW/Day, respectively, for each type of lead dust which control group were fed with AIN-76 semipurified diet only. Every three animals for a specific lead dust and dose group were sacrificed at the15th, 29th, 43rd, respectively. Blood samples were collected and analyzed for blood lead level and lead isotope composition. Results of blood lead determination showed that, in addition to the effect of lead dose on the bioavailability, the lead dust species and their particle sizes also had influences on the bioavailability. It was found that the bioavailability of lead dust was inversely associated with particle size, and the lead peroxide dust demonstrated higher bioavailability than the elemental lead powder. Besides, the results of lead isotope composition analysis showed that Pb206/Pb207 was a sensitive indicator in this study, for lead source identification. According to the results of present study, Pb206/Pb207 ratio is a useful tool to trace the lead dusts to which the workers were exposed. Moreover, with different extents of lead exposure, there were few changes in various lead isotope ratios in blood. If the original isotope ratios of lead dust from the lead battery plant were known, it would be available to use this method to estimate the lead exposure level of the workers in the battery plant, and to set up the priority for working environment improvement.
45
Ferguson, Stephen Hutton. "Electromechanical properties of lead magnesium niobate-lead titanate and lead zirconium titanate ceramic actuators". Thesis, 2005. http://hdl.handle.net/1828/1875.
Texto completo da fonteResumo:
Piezoelectric and electrostrictive actuators composed of lead titanate zirconate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) are important in a variety of engineering applications. A review of the literature indicated that published phase diagrams for the PMN-PT system are based primarily on temperatures of dielectric transitions. rather than direct measurements of structural changes. Structural transformations in the PMN-PT ceramic system have not been investigated at non-ambient temperatures for compositions with less than 0.29 PT. The review also revealed that crack growth in cyclic electric fields has been observed in only two compositions of PZT, while no crack initiation or growth is observed in a relaxor composition of PMN-PT.
The X-ray diffraction results showed that the PMN-PT samples undergo multiple structural transformations on cooling through the temperature regions of their dielectric transitions. In compositions containing 0.0, 0.08, 0.10 and 0.20, an upper transformation temperature Ta, derived from a sharp change in coefficient of thermal expansion, lies well above the temperature Tm, of the observed maximum in dielectric constant. Lower structural transformation temperatures observed in these c compositions lie close to the freezing temperature Tf, below which ceramics exhibit remanent polarization. The temperatures of an upper structural transformation in PMN-PT ceramics with the higher PT mole fractions 0.30 and 0.35, agree closely with the Curie Temperature Tc.
Cracks emanating from the corners of Vickers diamond indents in the soft piezoelectric ceramics BM532 PZT (Navy-Type VI) and PMN-0.30PT were increased in length when subjected to low frequency cyclic electric fields that were applied normal to the crack. Crack growth was observed in fields of 2-5 x Ec, but no new cracks were initiated when these higher fields were applied. Similar induced cracks in hard piezoelectric PZT ceramics, did not exhibit visible crack growth when subjected to low frequency fields with amplitudes up to +3.15 MV/m (1.6 x Ec), which is considered to be a safe maximum to avoid dielectric breakdown in PZT ceramics. No cracks were observed to emanate from the corners of either Vickers, or Knoop, diamond indents in samples of PMN-0.08PT. The intergranular cracks which emanate from the sides of the indents did not grow, and no new cracks were initiated, when the specimens were subjected to similar electric fields.
46
Morrison-Ibrahim, Deborah E. "Lead Distribution in Urban Soils: Relationship Between Lead Sources and Children's Blood Lead Levels". Thesis, 2011. http://hdl.handle.net/1805/2598.
Texto completo da fonte
47
Chen, Li-Min, e 陳立敏. "The Study of Competitiveness of LED Lead Frame Industry". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/9953b3.
Texto completo da fonteResumo:
碩士國立臺北科技大學
管理學院工業工程與管理EMBA專班
102
Over the years, global warming has been identified as being the main significant cause for climate change, and the economic losses from severe weather are inestimable. Today, we are facing large challenges, not only from the energy crisis issues but also environmental protection as well. Therefore, environmental impact management and green energy are issues gaining extraordinary attention among companies throughout the world, and leading to a rapid growth of green industry development. Light Emitting Diote(LED) is one of the green products which have a number of advantages such as being able to use less power consumption, lower carbon dioxide (CO2) emissions, and maintenance costs are reduced, with these benefits LED products are believed to be one of the best green technologies for lighting worldwide. With a greater need for LED, the LED lead frame industry continues to grow rapidly. For a firm to outperform its competitors in LED lead frame industry, the firm needs to know its core competences. In terms of firm competitiveness, the capabilities of product research and development, the speed of process development, cost control, quality management and flexible services, are the key value activities to enhance and maintain a sustainable competitive advantage and to stay ahead in the market. This research focuses on the analysis of the background, infrastructure, current situation and the supply chain of the LED lead frame industry. It, like other industries, are facing great pressures from the lower priced competitors, and the current trend towards shortening product life cycles. This study implements the Delphi method and the Analytic Hierarchy Process, to analyze the competitiveness of the LED lead frame, and to summarise it into six dimensions and thirty-five key factors. The main purpose of this study is to offer a method to enhance the competitiveness of the LED lead frame industry.
48
Chueh, Miao-Ju, e 闕妙如. "A Study of the relationship between airborne lead and blood lead among lead-acid battery workers". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/16737211692761399395.
Texto completo da fonteResumo:
碩士國立臺灣大學
環境衛生研究所
91
Lead poison has been considered as one of the occupation hazard for lead-acid battery workers. The studies investigating the relationship between the lead dust concentration in the enviroment and the blood lead concentration of the workers have shown that other factors might play an important role in modulating the blood lead concentration in those workers. Those workers are then educated about how and why these identified factors may endanger to their health and follow-up studies are carried out as well. During the process, the workers with high blood lead concentrations are monitored and the changes in the blood lead concentration are analyzed. The results are subsequently used to investigate how the airborne lead concentration can be used as an index for lead exposure. This study is focused on the labors who work in a major battery manufacture. The labors are divided into two different groups. The first group is defined by measuring the real airborne lead concentration in the working environment. The second group is defined by estimating the airborne lead exposure concentration. In addition to measuring the level of lead dust these workers are exposed to, the information obtained from the blood lead concentration of those workers and a survey are also used. Based on the results of these analyses, we found that the blood lead concentration of the workers is positively correlated with the lead dust concentration in the environment and the length of exposure and whether the workers smoke or not. However, there was a negative correlation between the blood lead concentration of the workers and the usage of personal protection equipments or personal hygiene. Generally, this study did not find any significant difference between these two groups. Based on our data analysis, we identified some factors that might affect the blood lead concentration such as the use of a personal protection equipment or personal hygiene. To empirically test the effects of these factors on the level of blood lead concentration, this study recruited 105 workers who have high blood lead concentration. These workers were educated about how these identified factors may endanger to their health. Four months later, the number of workers with high blood lead concentration has reduced to 62 persons. This study supports that it is feasible to reduce the risk of exposing to lead if all these risks factors can be identified and controlled. To sum up, the risk of exposing to lead dust can be reduced, if the focus is placed on the idiosyncrasy of the workers such as personal hygiene and whether the personal protection equipment was wear appropriately. Lead poison has been considered as one of the occupation hazard for lead-acid battery workers. The studies investigating the relationship between the lead dust concentration in the enviroment and the blood lead concentration of the workers have shown that other factors might play an important role in modulating the blood lead concentration in those workers. Those workers are then educated about how and why these identified factors may endanger to their health and follow-up studies are carried out as well. During the process, the workers with high blood lead concentrations are monitored and the changes in the blood lead concentration are analyzed. The results are subsequently used to investigate how the airborne lead concentration can be used as an index for lead exposure. This study is focused on the labors who work in a major battery manufacture. The labors are divided into two different groups. The first group is defined by measuring the real airborne lead concentration in the working environment. The second group is defined by estimating the airborne lead exposure concentration. In addition to measuring the level of lead dust these workers are exposed to, the information obtained from the blood lead concentration of those workers and a survey are also used. Based on the results of these analyses, we found that the blood lead concentration of the workers is positively correlated with the lead dust concentration in the environment and the length of exposure and whether the workers smoke or not. However, there was a negative correlation between the blood lead concentration of the workers and the usage of personal protection equipments or personal hygiene. Generally, this study did not find any significant difference between these two groups. Based on our data analysis, we identified some factors that might affect the blood lead concentration such as the use of a personal protection equipment or personal hygiene. To empirically test the effects of these factors on the level of blood lead concentration, this study recruited 105 workers who have high blood lead concentration. These workers were educated about how these identified factors may endanger to their health. Four months later, the number of workers with high blood lead concentration has reduced to 62 persons. This study supports that it is feasible to reduce the risk of exposing to lead if all these risks factors can be identified and controlled. To sum up, the risk of exposing to lead dust can be reduced, if the focus is placed on the idiosyncrasy of the workers such as personal hygiene and whether the personal protection equipment was wear appropriately.
49
Wang, Po-Yung, e 王博勇. "The Optimized Design of Transferred Material in LED Lead Frame". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/yyafhy.
Texto completo da fonteResumo:
碩士中華科技大學
經營管理研究所
103
The frame is the rack of the chips as well as the transportation medium for the inner electrics to the board. Taiwan suppliers of SMD LED frame share the world make about 18~21%. The usage of LED spread, LED supplier expanded the factory accordingly, the newer should face big challenge. Herewith the research for taking place of PPA plastic as the SMD LED reflector by Epoxy which is high temperature resistance & Good resistance to ultraviolet radiation intensity. It can increase the power from 0.5w to 0.7~2.0W. Compare with the low power LED frame in the market, Epoxy need extra proceedure to remove the extra plastic, and the new proceeding is required as well, it may drop the rate of production, and increase the production cost, and the technology is not well developed still not grown enough that is why the high power LED still not popular yet. So, This research on the foundation of the LED frame or the photoelectric company with many years development experience, develop the high temperature resistance & Good resistance to ultraviolet radiation intensity LED frame to fit for the mass production, and to obtain the molding parameter determination, including temperature and timing of the clamping force of transfer molding, transfer force, transfer speed, and the electricity and timing of deflasing, etc. Then to test the reliability during the assembly section. The test including High humidity environment test, High temperature weather resistance test,Red ink leakage test and UV test. The result including two parts: squeeze pressure 16.7 kgf/cm²、 clamp pressure 100 kgf/cm²、Dispensing time 9-12s, deflasing power is 3A,electrolytic reaction time 3 minutes, then get the best parameter.No bubble and fall off during 168H test with 85% humidity & 85°C high temperature,non-discolouring with 2h roast of 150°C, and get 70% reflectivity with 1000h roast of 150°C, and pass Red ink leakage test. And hereby, we got the the high power epoxy LED frame with UV resistant, and develop the tooling for the transfer-molding and assembly section. And research for the high power LED technology, Promote the competitiveness of the LED industry,Let the whole LED industry development in Taiwan leading force in Asia, China, Japan, South Korea, in international beyond Europe and the United States and other countries.
50
Hsia, Kuo Ching, e 郭青遐. "Comparison of the effects of blood lead and serum lead on health among occupational lead exposed workers". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/zkm27b.
Texto completo da fonteResumo:
碩士高雄醫學大學
職業安全衛生研究所
91
Although the whole blood lead measurement is currently used widely, about 99% of lead in blood is considered to be distributed in erythrocytes and which is a non-diffusible lead bound to the hemoglobin and the erythrocyte membrane. Only about 1% of lead in serum or plasma is considered to be diffusible and has greater bioavailability than lead in erythrocytes. Several investigators have proposed that plasma or serum Pb levels may better reflect the fraction of circulatory Pb that is more freely available for exchange with peripheral target tissues (e.g., brain, kidney, skeleton). At present there are few studies about the health effects of serum or plasma lead. Therefore, we have conducted a cross-sectional study to investigate the relationship between Pb in whole blood and serum and comparison of the effects of blood lead and serum lead on health among occupational lead-exposed workers in a battery factory. Before the assessment, we assessed if the serum lead concentrations will be stable in one-week storage days. The present data show that the serum lead did not significantly change when stored in a Vacutainer during one week. The second, we found that whole blood lead concentrations did not significantly correlated to hemoglobin nor haematorcrit. However, we found that natural log transformed serum lead concentrations inversely correlated to hemoglobin and haematocrit. But we found that the association of the natural log transformed serum lead concentrations and haematocrit is nonlinear . The parabola is the best model in our study. Therefore serum lead is a better exposure marker than whole blood lead to the effect on hemopoiesis. The present study also clearly shows that the relation between serum lead and whole blood is exponential. The association between serum lead levels and the other health effects need further study and assessment.