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Synthesis and characterization of surfmers for the synthesis of polystyrene-clay nanocompositesSamakande, Austin 12 1900 (has links)
Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / Two cationic polymerizable surfactants (surfmers), (11-acryloyloxyundecyl)dimethyl-(2-hydroxyethyl)ammonium bromide (Ethanol surfmer) and (11-acryloyloxyundecyl)-dimethylethylammonium bromide (Ethyl surfmer) were synthesized and characterized. Characterization was done using, conductivity, Fourier transform infra-red spectroscopy (FT-IR), electrospray mass spectrometry (ESMS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS) and polarized light microscopy with a heating stage. These surfmers and the commercial surfactant cetyltrimethylammonium bromide (CTAB) were used for functionalization of sodium montmorillonite (Na+-MMT), thereby forming organophilic MMT. The functionalization of MMT dispersions was carried out by ion exchange of the sodium ions in Na+-MMT by surfactants in aqueous media. Organophilic MMT clays were then dispersed in styrene and subsequently polymerized by a free radical reaction to yield polystyrene-clay nanocomposites. This in-situ intercalative polymerization process resulted in an exfoliated structure for Ethyl surfmer modified clay, a partially exfoliated structure for Ethanol surfmer modified clay and an intercalated structure for CTAB modified clay. These nanocomposite structures were confirmed by SAXS and transmission electron microscopy (TEM). The nanocomposites exhibited enhanced thermal stability. All the nanocomposites exhibited an inferior storage modulus (GI) at low clay contents relative to polystyrene. At higher clay loadings there was an increase in GI which was dependent on the level of clay dispersion and the clay content. All the nanocomposites showed an increase in glass transition temperature (Tg), regardless of the amount of clay and the level of clay dispersion. There was a shift towards higher temperatures and broadening of the tan δ peak, which was in turn dependent on the amount of clay and level of clay dispersion. Molecular masses of polystyrene-clay nanocomposites were in the range 105 g/mol for bulk polymerization relative to 103 g/mol for solution polymerization as revealed by gel permeation chromatography (GPC).
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Design, synthesis and characterization of novel raft agentsBivigou Koumba, Achille Mayelle 12 1900 (has links)
Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This thesis begins with the description of the preparation of thirteen dithioesters (of the form Z-
(C=S)-S-R) which were characterized via Fourier-transform infrared spectroscopy (FT-IR), nuclear
magnetic resonance spectroscopy (NMR) and ultraviolet spectroscopy (UV). The dithioesters were
then used as reversible addition-fragmentation chain transfer (RAFT) mediating agents in the bulk
polymerization of styrene, in order to observe differences in the kinetic behaviour of the
polymerizations and, as a result, the efficiencies of the dithioesters in mediating the
polymerizations.
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Discriminating wine yeast strains and their fermented wines : an integrated approachOsborne, Charles D. 12 1900 (has links)
Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2007. / The discrimination between wine yeast strains as well as between their fermented wines
has been investigated in this pilot study. The study was divided in two parts, the first to
investigate the discrimination between wines fermented with five different
Saccharomyces cerevisiae yeast strains, analysed by gas chromatography (GC) and
Fourier transform infrared spectroscopy (FTIR) and the second part to investigate
discrimination between wine yeast strains in different liquid media and in dried form
using FTIR in transmission and attenuated total reflectance (ATR) modes.
Wines from three cultivars (Clairette Blanche, Pinotage and Cabernet Sauvignon)
that were fermented by five Saccharomyces cerevisiae yeast strains (VIN13, WE372,
VIN13-EXS, VIN13-PPK and ML01) were analysed by GC and FTIR. This analysis was
done on individual sample sets that consisted of the wines of each of the mentioned
cultivars and also on samples drawn throughout the ageing process of these wines. The
data obtained were analysed by PLS-Discrimination (PLS-discrim), a chemometric
method. Using the data from both the analytical methods, discrimination was observed
between wines fermented with different yeast strains in each of the two vintages (2005
and 2006) for all the cultivars. When combining the data from the two vintages no
discrimination could be observed between the fermented wines. The discrimination of
the fermented wines was found to be similar when using data from GC and FTIR,
respectively. Since analysis with FTIR is considerably faster than analysis by GC, it
would be recommended that FTIR is used for future studies of similar nature.
Combining the samples into one set consisting of wines fermented with commercial wine
yeast strains and wines fermented from closely related wine yeast strains (the parental
strain and two genetically modified versions thereof (VIN13, VIN13-EXS and VIN13-
PPK), those fermented with closely related stains did not show good discrimination from
each other. Discrimination was found between wines fermented with genetically
modified (GM) wine yeast strains and those fermented with non-GM wine yeast strains.
This was done on a limited number of yeast strains and a larger study is needed to
confirm these results. As this is the first study of this nature and differences seen could
be as result of the different phenotypes.
It was shown that it is possible to use both FTIR-transmission and FTIR-ATR
(attenuated total reflectance) to discriminate between different wine yeast strain
phenotypes. It was shown that when using FTIR-transmission there is discrimination
between yeast samples suspended in yeast-peptone-dextrose (YPD) and in water.
Dried yeast samples could be discriminated when the yeast samples were in a granular, powder form or in a pellet form, using FTIR-ATR. It was possible to discriminate
between the closely related yeast strain phenotypes using FTIR-ATR.
In this pilot study it was shown that there can be discriminated between different wine
yeast strains and also between the wines fermented with different wine yeast strains. It
is recommended that further studies be conducted to refine and expand the study.
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The evaluation of Fourier transform infrared (FT-IR) spectroscopy for quantitative and qualitative monitoring of alcoholic wine fermentationMagerman, Cynthia M 12 1900 (has links)
Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Fermentation is a complex process in which raw materials are transformed into high-value
products, in this case, grape juice into wine. In this modern and economically competitive
society, it is increasingly important to consistently produce wine to definable specifications and
styles. Process management throughout the production stage is therefore crucial to achieve
effective control over the process and consistent wine quality. Problematic wine fermentations
directly impact on cellar productivity and the quality of wine. Anticipating stuck or sluggish
fermentations, or simply being able to foresee the progress of a given fermentation, would be
extremely useful for an enologist or winemaker, who could then take suitable corrective steps
where necessary, and ensure that vinifications conclude successfully. Conventional methods of
fermentation monitoring are time consuming, sometimes unreliable, and the information limited
to a few parameters only. The current effectiveness of fermentation monitoring in industrial wine
production can be much improved. Winemakers currently lack the tools to identify early signs of
undesirable fermentation behaviour and to take preventive actions.
This study investigated the application of Fourier transform mid infrared (FT-IR)
spectroscopy in transmission mode, for the quantitative and qualitative monitoring of alcoholic
fermentation during industrial wine production. The major research objectives were firstly to
establish a portfolio of quantitative calibration models suitable for quantification of the major
quality determining parameters in fermenting must. The second major research objective
focused on a pilot study aimed at exploring the use of off-line batch multivariate statistical
process control (MSPC) charts for actively fermenting must. This approach used FT-IR spectra
only, for the purpose of qualitative monitoring of alcoholic fermentation in industrial wine
production. Towards these objectives, a total of 284 industrial-scale, individual, actively
fermenting tanks of the seven major white cultivars and blends, and nine major red cultivars, of
Namaqua Wines, Vredendal, South Africa, were sampled and analysed with FT-IR
spectroscopy and appropriate reference methods during vintages 2007 to 2009.
For the quantitative strategy, partial least squares regression (PLS1) calibration models for
determination of the classic wine parameters ethanol, pH, volatile acidity (VA), titratable acidity
(TA) and the total content of glucose plus fructose, were redeveloped to provide a better fit to
local South African samples. New PLS1 models were developed for the must components
glucose, fructose and yeast assimilable nitrogen (YAN), all of which are frequently implicated in
problem fermentations. The regression statistics, that included the standard error of prediction
(SEP), coefficient of determination (R2) and bias, were used to evaluate the performance of the
redeveloped calibration models on local South African samples. Ethanol (SEP = 0.15 %v/v, R2 =
0.999, bias = 0.04 %v/v) showed very good prediction and with a residual predictive deviation
(RPD) of 30, rendered an excellent model for quantitative purposes in fermenting must. The
models for pH (SEP = 0.04, R2 = 0.923, bias = -0.01) and VA (SEP = 0.07 g/L, R2 = 0.894, bias
= -0.01 g/L) with RPD values of 4 and 3 respectively, showed that the models were suitable for
screening purposes. The calibration model for TA (SEP = 0.35 g/L, R2 = 0.797, bias = -0.004
g/L) with a RPD of 2, proved unsatisfactory for quantification purposes, but reasonable for
screening purposes. The calibration model for the total content of glucose plus fructose (SEP =
0.6.19 g/L, R2 = 0.993, bias = 0.02 g/L) with a RPD of 13, showed very good prediction and can
be used to quantify total glucose plus fructose content in fermenting must. The newly developed
calibration models for glucose (SEP = 4.88 g/L, R2 = 0.985, bias = -0.31 g/L) and fructose (SEP
= 4.14 g/L, R2 = 0.989, bias = 0.64 g/L) with RPD values of 8 and 10 respectively, also proved fit
for quantification of these important parameters. The new calibration models of ethanol, total
glucose plus fructose; and glucose and fructose individually, showed an excellent relation to
local South African samples and can be easily implemented by the wider wine industry.
Two calibration models were developed to determine YAN in fermenting must by using
different reference methods, namely the enzyme-linked spectrophotometric assay and Formol
titration method, respectively. The results showed that enzyme-linked assays provided a good
quantitative model for white fermenting must (SEP = 14.10 mg/L, R2 = 0.909, bias = -2.55 mg/L,
RPD = 6), but the regression statistics for predicting YAN in red fermenting must, were less
satisfactory (data not shown). The Formol titration method could be used successfully in both
red- and white fermenting must (SEP = 16.37 mg/L, R2 = 0.912, bias = -1.01 mg/L, RPD = 4). A
minor, but very important finding was made with respect to the storage of must samples that
were taken from tanks, but that could not immediately be analysed with FT-IR spectroscopy or
reference values. Principal component analysis (PCA) of frozen samples showed that must
samples could be stored frozen for up to 3 months and still be used to expand the calibration
sample sets when needed. Therefore, samples can be kept frozen to a later stage if immediate
analyses are not possible.
For the purpose of the pilot study that focused on the use of FT-IR spectroscopy for
qualitative off-line monitoring of alcoholic fermentation, a total of 21 industrial-scale fermentation
tanks were monitored at 8- or 12-hourly intervals, from the onset of fermentation to complete
consumption of the grape sugars. This part of the work excluded quantitative data, and only
used FT-IR spectra. MSPC charts were constructed on the PLS scores of all the FT-IR spectra
taken at the various time intervals of the different batches, using time as the y-variable. The
primary aim of this research objective was to evaluate if the PLS batch models could be used to
discriminate between normal and problem alcoholic fermentations. The models that were
constructed clearly showed the variations in patterns over time, between red- and white wine
alcoholic fermentations. One Colombar tank that was fermented at very low temperature in
order to achieve a specific wine style, was characterised by a fermentation pattern that clearly
differed form the rest of the Colombar fermentations. This atypical fermentation was identified
by the batch models constructed in this study. PLS batch models over all the Colombar
fermentations clearly identified the normal and problem fermentations.
The results obtained in this study showed that FT-IR spectroscopy showed great potential
for effective quantitative and qualitative monitoring of alcoholic fermentation during industrial
wine production. The work done in this project resulted in the development of a portfolio of
calibration models for the most important quality determining parameters in fermenting must.
The quantitative models were subjected to extensive independent test set validation, and have
subsequently been implemented for industrial use at Namaqua Wines. Multivariate batch
monitoring models were established that show good discriminatory power to detect problem
fermentations. This is a very useful diagnostic tool that can be further developed by monitoring
more normal and problem fermentations. Future work in this regard, will focus on further
optimisation and expansion of the quantitative and qualitative calibration models and
implementation of these in the respective wineries of Namaqua Wines. / AFRIKAANSE OPSOMMING: Fermentasie is ‘n komplekse proses waartydens rou material getransformeer word na produkte
van hoë waarde, in hierdie geval, druiwesap na wyn. In die huidige ekonomies-kompeterende
samelewing, is dit al hoe meer belangrik om volhoubaar wyn te produseer wat voldoen aan
definieerbare spesifikasies en style. Goeie prosesbestuur tydens die wynproduksie stadium is
baie belangrik om herhaalbaarheid en gehaltebeheer te verseker. Problematiese
wynfermentasies het ’n direkte impak op beide kelderproduktiwiteit en wynkwaliteit. Die
voorkoming van slepende- of steekfermentasies, of selfs net om probleme te voorsien, sou
uiters bruikbaar wees vir ‘n wynkundige of wynmaker, wat dan die toepaslike regstellende
stappe kan neem waar nodig, om te verseker dat die wynbereiding suksesvol voltooi word.
Konvensionele metodes van monitering van alkoholiese fermentasie is tydrowend, soms
onbetroubaar en die inligting beperk tot ‘n paar parameters. Die huidige effektiwiteit van
fermentasie monitering in industriële wynproduksie kan heelwat verbeter word. Wynmakers
ervaar tans ’n behoete aan tegnologië wat die vroeë tekens van ongunstige fermentasiepatrone
kan identifiseer, en hul doeltreffendheid om moontlike regstellende aksies te neem, is dus
beperk.
Hierdie studie het die toepassing van Fourier transformasie mid-infrarooi (FT-IR)
spektroskopie in transmissie, ondersoek met die oog op kwantitatiewe en kwalitatiewe
monitering van alkoholiese gisting tydens industriële wynproduksie. Die vernaamste
navorsingsdoelwitte was eerstens om ’n portefeulje van kwantitatiewe kalibrasiemodelle te
vestig, wat geskik is om die belangrikste kwaliteitsbepalende parameters in gistende mos te
kwantifiseer. Die tweede hoofnavorsingsdoelwit was ’n loodsstudie wat ondersoek ingestel het
na die opstel van multiveranderlike statistiese proseskontrole grafieke van aktief-gistende mos,
met die oog op aflyn-kwalitatiewe monitering van alkoholiese gisting in industriële
wynproduksie. Hiervoor is slegs FT-IR spektra gebruik. Vir die doel van hierdie studie is
monsters van ’n totaal van 284 individuele, aktief-gistende tenke van die sewe hoof wit kultivars
en hul versnydings en nege hoof rooi kultivars van Namaqua Wyne, Vredendal, Suid Afrika,
geneem. Al die monsters is met toepaslike chemiese metodes en FT-IR spektroskopie analiseer
tydens die parsseisoene van 2007 tot 2009.
Vir die kwantitatiewe strategie is parsiële kleinste kwadraat (PKK1) kalibrasiemodelle vir die
bepaling van die klassieke wynparameters etanol, pH, vlugtige suur (VS), titreerbare suur (TS)
en die totale konsentrasie van glukose plus fruktose herontwikkel, om beter te pas op plaaslike
Suid-Afrikaanse monsters. Nuwe PKK1 kalibrasiemodelle is ontwikkel vir die komponente
glukose, fruktose en gis-assimileerbare stikstof, aangesien hierdie komponente gereelde
aanduidings van probleemgisting is. Die regressiestatistieke het die standaardvoorspellingsfout
(SVF), bepalingskoëffisiënt (R2) en sydigheid ingesluit en was gebruik om die prestasie van die
herontwikkelde kalibrasiemodelle vir plaaslike Suid-Afrikaanse monsters te evalueer. Etanol
(SVF = 0.15 %v/v, R2 = 0.999, sydigheid = 0.04 %v/v) het baie goeie regressiestatistiek getoon
en met ‘n relatiewe voorspellingsafwyking (RVA) van 30, was dit ‘n uitstekende model vir
kwantifisering in gistende mos. Die modelle vir pH en VS met RVA waardes van 4 en 3
onderskeidelik, is geskik vir semi-kwantitatiewe toepassings. Die kalibrasiemodel vir TS met ‘n
RVA waarde van 2, was nie geskik vir akkurate kwantifisering nie, maar wel vir semikwantitatiewe
analises. Die kalibrasiemodel vir die totale glukose plus fruktose inhoud in
gistende mos, met ‘n RVA waarde van 13, het uitstekende regressiestatistiek gegee en is
geskik vir akkurate kwantifiseringsdoeleindes. Die nuut-ontwikkelde kalibrasiemodelle vir
glukose en fruktose, met RVA waardes van onderskeidelik 8 en 10, is geskik vir akkurate
kwantifisering van hierdie belangrike parameters. Die kalibrasiemodelle vir etanol, totale
glukose plus fruktose, en glukose en fruktose afsonderlik, het uitstekende korrelasies getoon
met plaaslike Suid-Afrikaanse monsters en is gereed om toepassing te vind in die wyer
wynindustrie.
Twee kalibrasiemodelle is ontwikkel om gis-assimileerbare stikstof in gistende mos te
bepaal, deur gebruik te maak van verskillende verwysingsmetodes van analise; hierdie metodes
was ‘n ensiem-gekoppelde spektrofotometriese toets en die Formoltitrasie metode. Resultate
het getoon dat goeie regressiestatistiek vir FT-IR spektroskopie-gebaseerde kalibrasiemodelle
waar data wat met die ensiem-gekoppelde toetse verkry is, as verwysingwaardes gebruik is, in
wit gistende mos (SVP = 14.10 mg/L, R2 = 0.909, sydigheid = -2.55 mg/L, RVA = 6), maar nie in
rooi gistende mos nie. Die Formoltitrasie metode as verwysingsmetode, was geskik vir die
ontwikkeling van goeie kalibrasiemodelle in beide rooi- en wit gistende mos (SVP = 16.37 mg/L,
R2 = 0.912, sydigheid = -1.01 mg/L, RVA = 4). ’n Sekondêre, maar baie belangrike bevinding is
gemaak met betrekking tot die stoor van mosmonsters wat geneem is van tenke, maar wat nie
dadelik met die verwysingsmetodes en FT-IR spektroskopie analiseer kon word nie.
Multiveranderlike hoofkomponentanalise op vars en gevriesde sapmonsters het getoon dat
gevriesde monsters gebruik kan word om die kalibrasie datastel uit te brei, wanneer benodig.
Dus, sapmonsters kan gevries word tot ’n later stadium as onmiddelike analises nie moontlik is
nie.
Vir die doel van die tweede navorsingsdoelwit van die studie, naamlik kwalitatiewe af-lyn
monitering van alkoholiese fermentasie met FT-IR spektroskopie, is ‘n totaal van 21 industriëlegrootte
fermentasietenks ge-monitor deur sapmonsters met 8- tot 12-uurlikse intervalle te trek,
vanaf die begin van fermentasie, totdat al die druifsuiker gemetaboliseer is. Vir hierdie deel van
die werk is die kwantitatiewe data nie gebruik nie; slegs die FT-IR spektra. Multiveranderlike
statistiese proseskontrole grafieke is opgestel op grond van die PKK tellings wat bereken is op
al die FT-IR spektra wat gemeet is by die verskillende tydsintervalle. Vir hierdie analise is tyd as
y-veranderlike gebruik. Die vernaamste doel van hierdie ondersoek was om te evalueer of die
PKK-gebaseerde modelle kon onderskei tussen normale en slepende gistings. Die modelle wat
verkry is, het die variasie oor tyd in die fermentasiepatrone tussen wit- en rooiwyn fermentasies
tydens alkoholiese gisting, duidelik uitgewys. Een Colombar tenk wat teen baie lae temperatuur
gefermenteer is om ‘n spesifieke wynstyl te verkry, se fermentasiepatroon het aansienlik verskil
van die ander Colombar tenks wat gemonitor is, en hierdie atipiese patroon is ook deur die
kwalitatiewe modelle identifiseer. ‘n PKK model oor al die Colombar fermentasies kon duidelik
tussen normale en slepende gistings onderskei.
Die resultate wat in hierdie studie verkry is, het getoon dat FT-IR spektroskopie baie goeie
potensiaal toon vir die aanwending van kwantitatiewe en kwalitatiewe monitering van
alkoholiese fermentasie tydens industriële wynproduksie. Die werk wat in hierdie projek gedoen
is, het gelei tot die vestiging van ‘n portefeulje van kalibrasiemodelle vir die belangrikste
kwaliteitsbepalende parameters in fermenterende mos. Die kwantitatiewe modelle is baie
deeglik getoets met onafhanlike toets datastelle, en daarna is die kalibrasiemodelle geimplementeer
vir industriële gebruik by Namaqua Wyne. Multiveranderlike statistiese
proseskontrole grafieke wat baseer is op data wat vanaf 21 verskillende fermentasietenks
verkry is, het baie goeie potensiaal getoon om probleemfermentasies vroeg te identifiseer. Dié
grafieke is ‘n baie nuttige diagnostiese hulpmiddel wat verder ontwikkel kan word om
verskillende tipes probleemfermentasies te monitor. Toekomstige navorsing in hierdie konteks,
sal toegespits word op die optimisering en uitbreiding van die kwantitatiewe en kwalitatiewe
modelle, sowel as toepassing van die tegnieke in die onderskeie kelders van Namaqua Wyne.
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The optimal control of a Lévy processDiTanna, Anthony Santino 23 October 2009 (has links)
In this thesis we study the optimal stochastic control problem of the drift of a Lévy process. We show that, for a broad class of Lévy processes, the partial integro-differential Hamilton-Jacobi-Bellman equation for the value function admits classical solutions and that control policies exist in feedback form. We then explore the class of Lévy processes that satisfy the requirements of the theorem, and find connections between the uniform integrability requirement and the notions of the score function and Fisher information from information theory. Finally we present three different numerical implementations of the control problem: a traditional dynamic programming approach, and two iterative approaches, one based on a finite difference scheme and the other on the Fourier transform. / text
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Travel time reliability assessment techniques for large-scale stochastic transportation networksNg, Man Wo 07 October 2010 (has links)
Real-life transportation systems are subject to numerous uncertainties in their operation. Researchers have suggested various reliability measures to characterize their network-level performances. One of these measures is given by travel time reliability, defined as the probability that travel times remain below certain (acceptable) levels. Existing reliability assessment (and optimization) techniques tend to be computationally intensive. In this dissertation we develop computationally efficient alternatives. In particular, we make the following three contributions.
In the first contribution, we present a novel reliability assessment methodology when the source of uncertainty is given by road capacities. More specifically, we present a method based on the theory of Fourier transforms to numerically approximate the probability density function of the (system-wide) travel time. The proposed methodology takes advantage of the established computational efficiency of the fast Fourier transform.
In the second contribution, we relax the common assumption that probability distributions of the sources of uncertainties are known explicitly. In reality, this distribution may be unavailable (or inaccurate) as we may have no (or insufficient) data to calibrate the distributions. We present a new method to assess travel time reliability that is distribution-free in the sense that the methodology only requires that the first N moments (where N is any positive integer) of the travel time to be known and that the travel times reside in a set of known and bounded intervals. Instead of deriving exact probabilities on travel times exceeding certain thresholds via computationally intensive methods, we develop analytical probability inequalities to quickly obtain upper bounds on the desired probability.
Because of the computationally intensive nature of (virtually all) existing reliability assessment techniques, the optimization of the reliability of transportation systems has generally been computationally prohibitive. The third and final contribution of this dissertation is the introduction of a new transportation network design model in which the objective is to minimize the unreliability of travel time. The computational requirements are shown to be much lower due to the assessment techniques developed in this dissertation. Moreover, numerical results suggest that it has the potential to form a computationally efficient proxy for current simulation-based network design models. / text
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THREE-DIMENSIONAL NON-CONTACT SURFACE PROFILERS FOR SEMICONDUCTOR IC PACKAGE INSPECTIONNakazawa, Takeshi January 2011 (has links)
The subject of this dissertation is the development of three-dimensional (3D) surface profilers for semiconductor back-end inspection. The value of this study is: 1) to provide a new phase-to-height relationship for Fourier Transform Profilometry (FTP) that is universal as it allows alternate FTP system architectures for a micrometer scale object measurement, and 2) to provide a new method for full field substrate warpage and ball grid array (BGA) coplanarity inspection using machine vision. The desire to increase electronic device performance has resulted in denser and smaller IC packaging. As the dimensions of the devices decrease, the requirements for substrate flatness and surface quality become critical in avoiding device failure. For a high yield production, there is an increasing demand in the requirement for the dimensional verification of height, which requires 3D inspection. Based on the current demands from the semiconductor industry, this dissertation addresses the development of fast in-line surface profilers for large volume IC package inspection. Specifically, this dissertation studies two noncontact surface profilers. The first profiler is based on FTP for measuring the IC package front surface, the silicon die and the epoxy underfill profile. The second profiler is based on stereovision and it is intended for inspecting the BGA coplanarity and the substrate warpage. A geometrical shape based matching algorithm is also developed for finding point correspondences between IC package images. The FTP profiler provides a 1 σRMS error of about 4 μm for an IC package sample in an area of 14 mm x 6.5 mm with a 0.13 second data acquisition time. For evaluating the performance of the stereovision system, the linearity between our system and a confocal microscope is studied by measuring a particular IC sample with an area of 38 mm x 28.5 mm. The correlation coefficient is 0.965 and the 2σdifference in the two methods is 26.9 μm for the warpage measurement. For BGA coplanarity inspection the correlation coefficient is 0.952 and the 2difference is 31.2 μm. Data acquisition takes about 0.2 seconds for full field measurements.
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Fast infrared spectroscopy in supercritical fluidsSun, Xue-Zhong January 2000 (has links)
No description available.
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Fourier transform holography for magnetic imagingDuckworth, Thomas Andrew January 2013 (has links)
State-of-the art Fourier transform holography (FTH) techniques use x-ray magnetic circular dichroism (XMCD) as a contrast mechanism for element-specfi c imaging of magnetic domains. With the soft x-ray Nanoscience beamline at Diamond Light Source in the UK, and the Dragon beamline at the European Synchrotron Radiation Facility (ESRF) in France, the possibility of new methods to study nanostructured magnetic systems has been demonstrated. The ability to record images without the use of lenses, in varying magnetic fi elds and with high spatial resolution down to 30 nm has been used to study in-plane magnetism of 50 nm thin permalloy (NiFe alloy) nanoelements. The holographic technique used extended reference objects rather than conventional pinhole references, which allowed a high flexibility on the direction of magnetisation that is probed. The element specific nature of the imaging, with the additional choice in the directions of magnetisation that are probed has been used to study dipolar interactions in a hard/Ta/soft [Co/Pt]30/Ta/Py multi-layered system. Images of the out-of-plane magnetised domains of [Co/Pt]30 were found to bare strong spatial resemblance to the in-plane domains of the permalloy. The domain structure is thought to be magnetostatically imprinted into permalloy during the growth stage of the lm, where stray elds generated by the adjacent Co/Pt multilayer influence the formation of domains in the permalloy. Strong resemblance between the two layers could be found at remanence within a pristine sample, however the similarities disappear after the sample was exposed to a saturating magnetic field. This disagreed with micromagnetic simulations performed in The Object Oriented MicroMagnetic Framework (OOMMF) program, and an explanation for the observations has been sought in the growth process of the multi-layered fi lm, with conditions that are diffi cult to recreate in the model. Optical holography has been used for preliminary insight into implementing a method of FTH in a reflective geometry at soft x-rays wavelength. With scattering chambers at BESSY II in Germany and at the Stanford Synchrotron Radiation Lightsource (SSRL) in California the possibility of reducing scattered noise in a hologram recorded in a reflective geometry has been investigated. Studies into specular and dif use reflections have been performed optically however the use of extended references alone may alleviate the current problem at x-ray wavelengths which lie in the weak signal given by a reflective point-like reference source.
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Homogénéisation numérique de structures périodiques par transformée de Fourier : matériaux composites et milieux poreux / Numerical homogenization of periodic structures by Fourier transform : composite materials and porous mediaNguyen, Trung Kien 21 December 2010 (has links)
Cette étude est consacrée au développement d'outils numériques basés sur la Transformée de Fourier Rapide (TFR) en vue de la détermination des propriétés effectives des structures périodiques. La première partie est dédiée aux matériaux composites. Au premier chapitre, on présente et on compare les différentes méthodes de résolution basée sur la TFR dans le contexte linéaire. Au second chapitre on propose une approche à deux échelles, pour la détermination du comportement des composites non linéaires. La méthode couple, les techniques de résolution basées sur la TFR à l'échelle locale, une méthode d'interpolation multidimensionnelle du potentiel des déformations à l'échelle macroscopique. L'approche présente de nombreux avantages faces aux approches existantes. D'une part, elle ne nécessite aucune approximation et d'autre part, elle est parfaitement séquentielle puisqu'elle ne nécessite pas de traiter simultanément les deux échelles. La loi de comportement macroscopique obtenue a été ensuite implémentée dans un code de calcul par éléments finis. Des illustrations dans le cas d'un problème de flexion sont proposées. La deuxième partie du travail est dédiée à la formulation d'un outil numérique pour la détermination de la perméabilité des milieux poreux saturés. Au chapitre trois, on présente la démarche dans le cas des écoulements en régime quasi-statique. La méthode de résolution repose sur une formulation en contrainte du itératif basée sur la TFR, mieux adaptée pour traiter le cas des contrastes infinis. Deux extensions de cette méthode sont proposées au quatrième chapitre. La première concerne la prise en compte des effets de glissement sur la paroi de la matrice poreux. La méthodologie employée repose sur le concept d'interphase et d'interface équivalente, introduite dans le contexte de l'élasticité des composites et adaptée ici au cas des milieux poreux. Enfin, on présente l'extension de la méthode au cas des écoulements en régime dynamique. Pour cela, on propose un nouveau schéma itératif pour la prise en compte des effets d'origine inertiel / This study is devoted to developing numerical tools based on Fast Fourier Transform (FFT) for determining the effective properties of periodic structures. The first part is devoted to composite materials. In the first chapter, we present and we compare the different FFT-based methods in the context of linear composites. In the second chapter, we propose a two-scale approach for determining the behavior of nonlinear composites. The method uses both FFT-based iterative schemes at the local scale and a multidimensional interpolation of the strain potential at the macroscopic scale. This approach has many advantages over existing ones. Firstly, it requires no approximations for the determination of the macroscopic response. Moreover, it is sequential in the sense that it is not required to process both scales simultaneously. The macroscopic constitutive law has been derived and implemented in a finite element code. Some illustrations in the case of a beam bending are proposed. The second part of the work is dedicated to the formulation of a numerical tool for determining the permeability of saturated porous media. In chapter three, we present the approach in the context of quasi-static flows. To solve the problem we propose a FFT stress-based iterative scheme, better suited to handle the case of infinite contrasts. Two extensions of this method are proposed in the fourth chapter. The first concerns the slip effects which occurs at the interface between solid and fluid. The methodology use the concept of interface and the equivalent interphase, initially introduced in the context of elastic composites and adapted here to the case of porous media. Finally, we present the extension of the method in the dynamic context. We propose a new iterative scheme for taking into account the presence of inertial terms
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