Detection of chemicals is a vital part of chemistry. For this reason, many detection systems are developed by scientists and every detection system has its own advantages. Raman spectroscopy is one of these detection systems having many advantages. However, this technique suffers from low signal intensity disadvantage. By developing a well prepared substrate, this problem can be easily solved / moreover, even single molecule detection can be possible. In this study, a novel surface enhanced Raman scattering (SERS) substrate was prepared in two steps: In the first step, ethylenedioxythiophene (EDOT) monomer was polymerized electrochemically onto indium tin oxide (ITO) coated glass. In the next step, silver ions were reduced electrochemically onto surface prepared in the previous step.In the substrate preparation part, the reduction potential of silver ion, the concentration of silver ions in solution, the polymer film thickness and reduced silver amount on substrates were optimized to get the best SERS performances from substrates. The prepared substrates were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) attached to SEM. In the SERS performance investigation part, homogeneity and the shelf life of the prepared silver-PEDOT substrates were tested. Homogeneity is very important in terms for the applications of Raman technique in quantitative analysis since most of the reported substrates are lack homogeneity consideration, our study will be an important contribution to the literature. The stability of the substrate was investigated for a period of one month. The very small change in the signal at the end of one month indicated that the substrate can be used even longer time with high efficiency. In all the studies, brilliant cresyl blue (BCB) is used as a model compound. Some important Raman active chemicals, namely, rhodamine 6G (R6G) and 4-mercapto benzoic acid (4-MBA) were detected by using the prepared substrates.

It is known that record values and order statistics are closely related. When record values and order statistics are viewed as point processes, the two processes both share the order statistics property. The results of Beg and Balasubramanian(1990), Wu and Ouyang(1996), and Huang and Su(1999) about record values and order statistics motivated us to investigate more general results of characterization for order statistics point processes by using conditional expectations based on order statistics. On the other hand, in the class of point processes, there are a lot of characterizations of homogeneous Poisson processes based on the memoryless property of exponential distribution. The result of Asadi(1999) about characterization of the Gumble bivariate exponential or the bivariate geometric distribution inspired us be interested in investigating some similar results about non-independent bivarite homogeneous Poisson processes.

Stochastic hybrid dynamic systems that incorporate both continuous and discrete dynamics have been an area of great interest over the recent years. In view of applications, stochastic hybrid dynamic systems have been employed to diverse fields of studies, such as communication networks, air traffic management, and insurance risk models. The aim of the present study is to investigate properties of some classes of stochastic hybrid dynamic systems. The class of stochastic hybrid dynamic systems investigated has random jumps driven by a non-homogeneous Poisson process and deterministic jumps triggered by hitting the boundary. Its real-valued continuous dynamic between jumps is described by stochastic differential equations of the It\^o-Doob type. Existing results of piecewise deterministic models are extended to obtain the infinitesimal generator of the stochastic hybrid dynamic systems through a martingale approach. Based on results of the infinitesimal generator, some stochastic stability results are derived. The infinitesimal generator and stochastic stability results can be used to compute the higher moments of the solution process and find a bound of the solution. Next, the study focuses on a class of multidimensional stochastic hybrid dynamic systems. The continuous dynamic of the systems under investigation is described by a linear non-homogeneous systems of It\^o-Doob type of stochastic differential equations with switching coefficients. The switching takes place at random jump times which are governed by a non-homogeneous Poisson process. Closed form solutions of the stochastic hybrid dynamic systems are obtained. Two important special cases for the above systems are the geometric Brownian motion process with jumps and the Ornstein-Uhlenbeck process with jumps. Based on the closed form solutions, the probability distributions of the solution processes for these two special cases are derived. The derivation employs the use of the modal matrix and transformations. In addition, the parameter estimation problem for the one-dimensional cases of the geometric Brownian motion and Ornstein-Uhlenbeck processes with jumps are investigated. Through some existing and modified methods, the estimation procedure is presented by first estimating the parameters of the discrete dynamic and subsequently examining the continuous dynamic piecewisely. Finally, some simulated stochastic hybrid dynamic processes are presented to illustrate the aforementioned parameter-estimation methods. One simulated insurance example is given to demonstrate the use of the estimation and simulation techniques to obtain some desired quantities.

Μια από τις πιο επιτυχείς προσεγγίσεις της γεωμετρίας είναι αυτή που πρότεινε ο Γερμανός μαθηματικός Felix Klein στο γνωστό Πρόγραμμα Erlangen. To πρόγραμμα αυτό αποτέλεσε ένα γενικό σχέδιο ταξινόμησης των διάφορων γεωμετριών που εμφανίστηκαν μετά την ανακάλυψη των μη Ευκλείδειων γεωμετριών, με τεράστιες επιπτώσεις όχι μόνο στα μαθηματικά αλλά και στη θεωρητική φυσική. Σύμγωνα με τον Klein, το αντικείμενο της γεωμετρίας είναι μια πολλαπλότητα στην οποία δρα μια ομάδα μετασχηματισμών, η οποία συνήθως είναι μια ομάδα Lie. Στη περίπτωση που η ομάδα δρα μεταβατικά πάνω στην πολλαπλότητα, τότε οδηγούμαστε στην περίτωση των ομογενών χώρων. Κλασικά παραδείγματα τέτοιων χώρων αποτελούν η σφαίρα και ο πραγματικός ή μιγαδικός προβολικός χώρος. Η βασική ιδιότητα των ομογενών χώρων είναι ότι αν γνωρίζουμε την τιμή κάποιου γεωμετρικού μεγέθους (για παράδειγμα της καμπυλότητας) σε ένα σημείο του χώρου τότε χρησιμοποιώντας κατάλληλες απεικονίσεις μεταφοράς μπορούμε να υπολογίσουμε την τιμή του μεγέθους αυτού σε οποιοδήποτε άλλο σημείο του χώρου. Στην εργασία μας περιγράφουμε τη γεωμετρία των χώρων αυτών χρησιμοποιώντας εργαλεία από τη θεωρία των ομάδων Lie. Το δεύτερο σκέλος της εργασίας αφορά τη θεωρία των πολλαπλοτήτων σημαιών, οι οποίες αποτελούν και μια ιδιαίτερη κλάση ομογενών χώρων. Μια πολλαπλότητα σημαιών είναι η τροχιά της συζυγούς αναπαράστασης μιας ημιαπλής ομάδας Lie. Οι χώροι αυτοί δέχονται μια κομψή αλγεβρική περιγραφή χρησιμοποιώντας τη δομική θεωρία των ημιαπλών αλγεβρών Lie και ταξινομούνται από τα χρωματιστά διαγράμματα Dynkin. / One of the most successful approaches to geometry is that suggested by the german mathematician Felix Klein and his famous Erlangen programm. According to Klein, a geometry is the study of all these objects which remain invariant under the action of a transormation group. Usually this group is a Lie group. If the above action is transitive then the space is called Homogeneous space. Classical examples of these spaces are the sphere and the real or complex projective space. The basic property of homogeneous spaces is that if we know the value of a geometrical object (e.g curvature) at a given point, then we can calculate the value of this quantity at any other point by using certain translations maps. In this project we describe the geometry of homogeneous spaces, by using tools of the Lie group theory. The second part of this project has to do with generalized flag manifolds, which are an important class of homogeneous spaces. A flag manifold is the orbit of the adjoint representation of a compact semisimple Lie group. These spaces admit a nice algebraic description by using the structure theory of semisimple Lie algebras and are classified by painted Dynkin diagramms.

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Darbe tirta tiekiamo oro temperatūros, deginių recirkuliacijos ir degalų savybių įtaka suslėgimu uždegamo homogeninio oro – bioetanolio mišinio degimo procesui, variklio darbo ir deginių emisijos rodikliams. Nustatytos variklio darbo homogeniniu oro – bioetanolio mišiniu maksimalios apkrovos zona, kurią riboja slėgio didėjimo greitis ir susidarantis detonacinis degimas. Gautieji rezultatai varikliui veikiant bioetanoliu, lyginti su rezultatais gautais varikliui veikiant baziniais degalais – benzinu. Dyzeliniam varikliui dirbant homogeniniu oro ir bioetanolio mišiniu, keičiant tiekiamo oro temperatūrą, naudojant deginių recirkuliaciją ir įmaišant 20 % reaktyvinių degalų, azoto oksidų emisijos lieka dešimtis kartų mažesnės negu tradicinio dyzelinio variklio. Slegiamo homogeninio oro – bioetanolio mišinio užsiliepsnojimui valdyti pirmą kartą panaudoti reaktyviniai degalai. / It was found that the intake air temperature, exhaust gas recirculation and fuel properties have the influence on the combustion characteristics of homogeneous air – bioethanol mixture, engine performance and emissions. The operating region was found at which critical rate of pressure rise was unacceptably high and engine worked at “knocking” combustion. In order to assess the combustion process in homogeneous charged compression ignition (HCCI) mode fuelled with the air – bioethanol mixture, it was compared whit the combustion process in HCCI mode fuelled with the air – gasoline mixture. When the diesel engine works in HCCI mode fuelled with air – bioethanol mixture, the nitrogen oxides can be reduced more than 10 times compared with normal diesel operation. For the first time, to control the autoignition of compressed homogeneous air and bioethanol mixture, the JET A1 fuel was simultaneously added in to combustible mixture in this study.

The High Pressure Test Unit (HPTU) forms part of the Pebble Bed Modular Reactor (PBMR) Heat Transfer Test Facility (HTTF). One of the test sections that forms part of the HPTU is the Braiding Effect Test Section (BETS). This test section allows for the evaluation of the so–called ‘braiding effect’ that occurs in fluid flow through a packed pebble bed. The braiding effect implies an apparent enhancement of the fluid thermal conductivity due to turbulent mixing that occurs as the flow criss–crosses between the pebbles. The level of enhancement of the fluid thermal conductivity is evaluated from the thermal dispersion effect. The so–called thermal dispersion quantity r K is equivalent to an effective Peclet number eff Pe based on the inverse of the effective thermal conductivity eff k . This thesis describes the experiments carried out on three different BETS test sections with pseudo–homogeneous porosities of 0.36, 0.39 and 0.45, respectively. It also provides the values derived for the enhanced fluid thermal conductivity for the range of Reynolds numbers between 1,000 and 40,000. The study includes the following: * Compilation of a literature study and theoretical background. * An uncertainty analysis to estimate the impact of instrument uncertainties on the accuracy of the empirical data. * The use of a Computational Fluid Dynamics (CFD) model to simulate the heat transfer through the BETS packed pebble bed.* Application of the CFD model combined with a numerical search technique to extract the effective fluid thermal conductivity values from the measured results. * The assessment of the results of the experiments by comparing it with the results of other investigations found in the open literature. The primary outputs of the study are the effective fluid thermal conductivity values derived from the measured data on the HPTU plant. The primary variables that were measured are the temperatures at radial positions at different axial depths inside the bed and the total mass flow rate through the test section. The maximum and minimum standard uncertainties for the measured data are 10.80% and 0.06% respectively. The overall effective thermal conductivities that were calculated at the minimum and maximum Reynolds numbers were in the order of 1.166 W/mK and 38.015 W/mK respectively. A sensitivity study was conducted on the experimental data and the CFD data. A maximum uncertainty of 5.92 % was found in the calculated effective thermal conductivities. The results show that relatively high values of thermal dispersion quantities or effective Peclet numbers are obtained for the pseudo–homogeneous packed beds when compared to randomly packed beds. Therefore, the effective thermal conductivity is low and it can be concluded that the radial mixing in the structured packing is low relative to the mixing obtained in randomly packed beds. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.

The High Pressure Test Unit (HPTU) forms part of the Pebble Bed Modular Reactor (PBMR) Heat Transfer Test Facility (HTTF). One of the test sections that forms part of the HPTU is the Braiding Effect Test Section (BETS). This test section allows for the evaluation of the so–called ‘braiding effect’ that occurs in fluid flow through a packed pebble bed. The braiding effect implies an apparent enhancement of the fluid thermal conductivity due to turbulent mixing that occurs as the flow criss–crosses between the pebbles. The level of enhancement of the fluid thermal conductivity is evaluated from the thermal dispersion effect. The so–called thermal dispersion quantity r K is equivalent to an effective Peclet number eff Pe based on the inverse of the effective thermal conductivity eff k . This thesis describes the experiments carried out on three different BETS test sections with pseudo–homogeneous porosities of 0.36, 0.39 and 0.45, respectively. It also provides the values derived for the enhanced fluid thermal conductivity for the range of Reynolds numbers between 1,000 and 40,000. The study includes the following: * Compilation of a literature study and theoretical background. * An uncertainty analysis to estimate the impact of instrument uncertainties on the accuracy of the empirical data. * The use of a Computational Fluid Dynamics (CFD) model to simulate the heat transfer through the BETS packed pebble bed.* Application of the CFD model combined with a numerical search technique to extract the effective fluid thermal conductivity values from the measured results. * The assessment of the results of the experiments by comparing it with the results of other investigations found in the open literature. The primary outputs of the study are the effective fluid thermal conductivity values derived from the measured data on the HPTU plant. The primary variables that were measured are the temperatures at radial positions at different axial depths inside the bed and the total mass flow rate through the test section. The maximum and minimum standard uncertainties for the measured data are 10.80% and 0.06% respectively. The overall effective thermal conductivities that were calculated at the minimum and maximum Reynolds numbers were in the order of 1.166 W/mK and 38.015 W/mK respectively. A sensitivity study was conducted on the experimental data and the CFD data. A maximum uncertainty of 5.92 % was found in the calculated effective thermal conductivities. The results show that relatively high values of thermal dispersion quantities or effective Peclet numbers are obtained for the pseudo–homogeneous packed beds when compared to randomly packed beds. Therefore, the effective thermal conductivity is low and it can be concluded that the radial mixing in the structured packing is low relative to the mixing obtained in randomly packed beds. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.

This work focuses on understanding the heterogeneous/homogeneous nature of the catalytic species for a variety of immobilized metal precatalysts used for C-C coupling reactions. These precatalysts include: (i) tethered organometallic palladium pincer complexes, (ii) an encapsulated small molecule palladium complex in a polymer matrix, (iii) mercapto-modified mesoporous silica metalated with palladium acetate, and (iv) amino-functionalized mesoporous silicas metalated with Ni(II). As part of this investigation, the use of metal scavengers as selective poisons of homogeneous catalysis is introduced and investigated as a test for distinguishing heterogeneous from homogeneous catalysis. The premise of this test is that insoluble materials functionalized with metal binding sites can be used to selectively remove soluble metal, but will not interfere with catalysis from immobilized metal. In this way the test can definitely distinguish between surface and solution catalysis of immobilized metal precatalysts. This work investigates three different C-C coupling reactions catalyzed by the immobilized metal precatalysts mentioned above. These reactions include the Heck, Suzuki, and Kumada reactions. In all cases it is found that catalysis is solely from leached metal. Three different metal scavenging materials are presented as selective poisons that can be used to determine solution vs. surface catalysis. These selective poisons include poly(vinylpyridine), QuadrapureTM TU, and thiol-functionalized mesoporous silica. The results are contrasted against the current understanding of this field of research and subtleties of tests for distinguishing homogeneous from heterogeneous catalysis are presented and discussed.

Homogeneously charged spark ignition (SI) engines are unable to stabilise the combustion in ultra lean mixtures, therefore they operate with a near stoichiometric air-fuel ratio (AFR) at all load points. This produces high engine out NOx and CO emissions with a compromise on fuel consumption. Moreover, stoichiometric operation is needed for effective operation of a three way catalyst, which is not adequate to meet future fuel consumption targets. (For complete abstract open document)