自從2004年人們在實驗室上發現石墨烯以來，IV族二維半導體材料，例如石墨烯、硅烯等，由於其優異的電學、力學、光學、以及熱力學性質，受到學術界的廣泛關注。為了使IV族二維半導體材料得到廣泛引用，穩定地生長高質量的石墨烯、硅烯二維半導體材料以及透徹的理解石墨烯、硅烯二維半導體材料和襯底之間的界面特性成為至關重要的研究方向。本文對在銅表面用多環芳香烴形成石墨烯的生長機理以及石墨烯、硅烯和襯底之間的界面電子學特性進行了詳細的分析和研究。希望以此能對IV族二維半導體材料的廣泛應用具有促進作用，並且對合理的設計電子器件結構具有新的啟示。 / 首先，我們用密度泛函理論對在銅表面用多環芳香烴形成石墨烯的生長機理進行了研究。理論計算表明在銅表面多環芳香烴形成石墨烯的生長過程主要包括：（1）在銅表面的誘導下多環芳香烴脫氫，（2）這些已經脫氫的多環芳香烴在銅表面相互結合形成石墨烯。由於銅和碳的相互作用非常弱，所以在銅表面這些已經脫氫的多環芳香烴並不會進一步分解成更小的碳團簇或者單個的碳原子。因此多環芳香烴的空間幾何構型對於最終形成的石墨烯的質量以及最低成長溫度有至關重要的影響。提高生長溫度可以提升脫氫多環芳香烴的活性和熱運動性，從而提高最終生成的石墨烯的質量。六苯并苯由於具有和石墨烯相同的六重對稱性和晶格結構，所以其在低溫生長高質量石墨烯方面最具有優勢。 / 其次，我們就石墨烯和（0001）二氧化硅表面所組成的界面的電子學特性進行了研究。結果表明石墨烯在（0001）二氧化硅表面的電子學特性主要有二氧化硅表面的性質以及氫化程度決定。如果用末端為甲基的分子修飾（0001）二氧化硅表面，可以進一步減弱二氧化硅表面氧原子對石墨烯電子學特性的影響，從而提高在二氧化硅表面石墨烯的載流子遷移率。此外，當石墨烯物理吸附在二氧化硅表面上時，垂直於石墨烯和二氧化硅界面的外加電場可以調製石墨烯和二氧化硅表面的電荷轉移。這一效應可以增強雙層石墨烯之間的電場，從而有效改變雙層石墨烯的能帶結構。我們的結果有助於更好的地認識和理解石墨烯吸附在二氧化硅表面所表現的實驗現象。 / 基於以上兩個結論，我們用三亚苯合成了高質量的單層石墨烯，並對其在普通二氧化硅表面上以及十八烷基鏈三甲氧基硅烷所修飾的二氧化硅表面上，所體現出的不同電子學性質和散射機理進行了詳細研究。用三亚苯作為石墨烯的生長源可以避免傳統氣象化學沉積方法在初期成核過程中所產生的缺陷，從而得到高質量的石墨烯。電學測量表明，石墨烯在普通二氧化硅表面上的載流子遷移率約為5090 cm²V⁻¹s⁻¹。而在十八烷基鏈三甲氧基硅烷所修飾的二氧化硅表面上，其遷移率可以提高到大約9080 cm²V⁻¹s⁻¹。此外，通過這兩種不同結構的電子器件進行定量的分析和對比，我們發現在室溫下，普通二氧化硅表面上的石墨烯電子器件的平均自由程主要由電離雜質所引起的長程散射所決定，電離雜質散射源密度約為5.34×10¹¹ cm⁻²。而對於十八烷基鏈三甲氧基硅烷所修飾的二氧化硅表面上的石墨烯電子器件的平均自由程主要由甲基以及石墨烯中的缺陷和晶界所引起的共振散射所決定，共振散射源密度為9.77×10¹° cm⁻²。我們的研究結果有助於揭示通過界面修飾來提升石墨烯電子器件性能的內在原理。 / 最後， 我們對單層石墨烯和硅烯封裝在金剛石薄膜和硅薄膜結構的電子學性質，以及其隨壓強的變化，進行了系統的理論研究。結果表明，當單層石墨烯和硅烯封裝在金剛石薄膜和硅薄膜中時，通過改變壓強和堆疊結構，單層石墨烯和硅烯在狄拉克點處的能隙和電子有效質量可以被有效地調製。電子有效質量和壓強成正比。硅烯的能隙對於壓強的變化比石墨烯更加敏感。並且異質封裝結構比同質封裝結構更有利於調製石墨烯和硅烯在狄拉克點處的能隙和電子有效質量。利用封裝技術和改變壓強的方法，石墨烯和硅烯的蜂窩狀結構不會被破壞，所以其小的載流子有效質量和高的載流子遷移率將會保持。所以對於構造高性能的納米電子學器件，這種方法有明顯的應用前景。 / Group IV two Dimensional Semiconductor Materials, such as graphene, silicene and so on, composed of an atomically thin layer of carbon and silicon atoms arranged in a honeycomb lattice, have received considerable attention, as their extraordinary electronic, mechanical, optical, and thermal properties arise from their unique 2D energy dispersions, since their representive, graphene, experimentally discovered in 2004. Reliable fabrication of high-quality graphene and silicene two dimensional layers and understanding the properties of interface between graphene or silicene two dimensional layers and substrates play an indispensable role for realizing their potential applications in nanoelectronics. This thesis attempts to paint a clear picture about the growth mechanism of graphene from Polycyclic aromatic hydrocarbons (PAHs) on Cu(111) surface and interfacial electronic properties of graphene and silicene to promote application of Two Dimensional Group IV Semiconductor and shed light on rational design of functional devices. / Firstly, in order to obtain insights into the reaction mechanism, the bottom-up growth of graphene from PAHs on Cu(111) surface has been systematically analyzed by means of large-scale ab initio simulation in a density functional theory (DFT) framework. Theoretical calculation shows that the underlying growth mechanism, which mainly involves surface-mediated nucleation process of dehydrogenated PAHs rather than segregation or precipitation process of small carbon clusters decomposed from the precursors. The quality of the synthesized graphene sheets and minimum growth temperature strongly depends on the structures of PAHs as well as the molecular activities. Increasing the growth temperature will augment the activity of carbon clusters, so as to increase the probability in formation of prefect graphene sheets. Coronene, having 6-fold rotational symmetry and the same lattice as graphene, has the highest probability in forming high quality graphene, especially at relatively low growth temperature. / Secondly, the electronic properties of graphene supported by (0001) SiO₂ surface are theoretically studied using the density functional theory. It is found that the electronic attributes of graphene on (0001) SiO₂ strongly depend on the underlying SiO₂ surface properties and the percentage of hydrogen-passivation. By applying methyl to passivate oxygen-terminated (0001) SiO₂ surface one can further reduce the interaction between the graphene sheet and oxygen-terminated surface. This can improve the charge carrier mobility of graphene supported by SiO₂ substrate and reduce the influence by residual interfacial molecules. In addition, the external electric field modulates the charge transfer between graphene and the SiO₂ surface, when graphene layers are physisorbed on the oxide surface. This phenomenon will enhance the built-in electric field of bilayer graphene so as to effectively modify its band structure. Our results shed light on a better atomistic understanding of the recent experiments on graphene supported by SiO₂. / Based on the above two conclusions, the graphene/substrate interface properties and engineering of bottom-gated, large-scale triphenylene-derived graphene transistors by applying octadecyltrimethoxysilane (OTMS) self-assembled monolayers (SAM) onto the gate dielectric surface are studied. To meet the challenge that the isolated carbon monomers are likely to form defective carbon clusters with pentagons, at the initial stage of CVD graphene growth, triphenylene (C₁₈H₁₂) (pentagon-free with only C and H) was used as the solid precursor for high-quality and large-scale graphene synthesis. Transport measurements performed on back-gated graphene field-effect transistors (GFETs) with large channel lengths (~25 μm) show a carrier mobility up to ~5090 cm²V⁻¹s⁻¹ on SiO₂/Si substrate at room temperature under vacuum. Furthermore we show that in virtue of the ultrasmooth SAM surface and reduced interfacial impurity scattering as well as attenuated surface polar phonon scattering, the GFET carrier mobility on octadecyltrimethoxysilane (OTMS) passiviated SiO₂ surface is consistently improved up to ~9080 cm²V⁻¹s⁻¹, whose graphene active layer has been grown with triphenylene precursor. This makes it promising for practical applications. In addition, in comparison with the devices without interface engineering, triphenylene-derived GFETs with OTMS-SAM modified SiO₂/Si substrate exhibit the marked carrier-density-dependent field-effect mobility. Quantitative analyses reveal that at ambient temperature, the predominant scattering sources affect the carrier mean free path for graphene devices on bare SiO₂ substrates and for those on OTMS passivated SiO₂ substrates are charged impurity induced long-range scattering (~5.34×10¹¹ cm⁻² in carrier density) and resonant scattering (short-range scattering ~9.77×10¹° cm⁻² carrier in density), respectively. Our findings elucidate the underlying dominate factors for achieving the significantly improved device performance of GFETs at room temperature. / Finally, by exploiting first-principles calculations, we show that the band gap and electron effective mass (EEM) of various confined graphene and silicene (D-X/G/H-D, Si-X/S/H-Si and D-X/S/H-D) can be effectively modulated by tuning the pressure (interlayer spacing) and stacking arrangement. The electron effective mass (EEM) is proportional to the band gap. The band gap of confined silicene is more sensitive to pressure than that of confined graphene. Moreover, heterogeneous interface would be beneficial to effectively control the band gap and carrier effective masses of confined graphene and silicene. Using the confined technique and pressure, the integrity of the honeycomb structure of graphene and silicene will be preserved, so the small effective masses and high mobility of graphene and silicene will remain during compression. The tunable band gap and high carrier mobility of the sandwich structures are promising for building high-performance nanodevices. / The aforementioned four sub-topics form the mechanistic understanding of graphene growth by PAHs and interfacial electronic properties of graphene and silicene down to the molecular level. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chen, Kun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Abstracts also in Chinese. / Abstract --- p.II / 博士學位論文摘要： --- p.VI / Acknowledgements --- p.X / Chapter Chapter 1 --- Introduction to Growth Methods and Electronic Properties of Graphene and Silicene --- p.1 / Chapter 1.1 --- Electronic Properties of Graphene --- p.2 / Chapter 1.1.1 --- The Direct Lattice and the Reciprocal Lattice --- p.2 / Chapter 1.1.2 --- Electronic Band Structure --- p.6 / Chapter 1.1.3 --- Tight-Binding Energy Dispersion --- p.7 / Chapter 1.1.4 --- Massless Dirac Fermions --- p.15 / Chapter 1.1.5 --- Carrier Density and Effective Mass --- p.21 / Chapter 1.1.6 --- The Tight-Binding Model of Bilayer Graphene --- p.24 / Chapter 1.1.7 --- The Two-Component Hamiltonian of Bilayer Graphene --- p.29 / Chapter 1.1.8 --- Trigonal Warping in Graphene --- p.32 / Chapter 1.1.9 --- Tunable Band Gap in Bilayer Graphene --- p.36 / Chapter 1.2 --- Synthesis of Graphene --- p.38 / Chapter 1.2.1 --- Exfoliation and Cleavage --- p.39 / Chapter 1.2.2 --- Thermal Decomposition of SiC --- p.40 / Chapter 1.2.3 --- Chemical Vapor Deposition of Graphene --- p.42 / Chapter 1.3 --- Electronic Properties at Graphene/Substrate Interface --- p.55 / Chapter 1.3.1 --- Graphene on SiO₂/Si Substrates --- p.56 / Chapter 1.3.2 --- Graphene on Hexagonal Boron Nitride (h-BN) --- p.60 / Chapter 1.3.3 --- Graphene on Organic Self-Assembled Monolayer (SAM) Passivation of Bared SiO₂/Si --- p.61 / Chapter 1.4 --- Synthesis and Electronic Properties of Silicene --- p.63 / Chapter 1.4.1 --- Synthesis of Silicene --- p.64 / Chapter 1.4.2 --- Electronic Properties of Silicene --- p.65 / Chapter References --- p.67 / Chapter Chapter 2 --- Introduction to Density Functional Theory --- p.75 / Chapter 2.1 --- Many-Particle Hamiltonian --- p.75 / Chapter 2.2 --- Born-Oppenheimer Approximation --- p.76 / Chapter 2.3 --- Hartree-Fock Method --- p.77 / Chapter 2.4 --- Density Functional Theory (DFT) --- p.77 / Chapter 2.4.1 --- Hohenberg-Kohn Theorems --- p.77 / Chapter 2.4.2 --- Kohn-Sham Method --- p.79 / Chapter 2.4.3 --- Kohn-Sham Equation --- p.80 / Chapter 2.4.4 --- Solution of Kohn-Sham Equation --- p.80 / Chapter 2.5 --- Electron Density Approximation --- p.80 / Chapter 2.5.1 --- Local Density Approximation (LDA) --- p.80 / Chapter 2.5.2 --- Generalized Gradient Approximation (GGA) --- p.82 / Chapter 2.5.3 --- Hybrid Functionals --- p.82 / Chapter 2.6 --- Plane Waves Expansion --- p.83 / Chapter 2.7 --- Pseudopotentials --- p.84 / Chapter 2.7.1 --- Ultrasoft Pseudopotentials (USPP) --- p.86 / Chapter 2.7.2 --- Projector Augmented Wave Potentials (PAW) --- p.87 / Chapter 2.8 --- DFT+U --- p.88 / Chapter References --- p.89 / Chapter Chapter 3 --- ab initio Study of Growth Mechanism of Graphene from Polycyclic Aromatic Hydrocarbons --- p.91 / Chapter 3.1 --- Introduction --- p.91 / Chapter 3.2 --- Experimental Results --- p.93 / Chapter 3.3 --- Calculation Method --- p.94 / Chapter 3.4 --- Calculation Results and Discussion --- p.96 / Chapter 3.5 --- Conclusion --- p.109 / Chapter References --- p.109 / Chapter Chapter 4 --- Electronic Properties of Graphene Altered by Substrate Surface Chemistry and Externally Applied Electric Field --- p.113 / Chapter 4.1 --- Introduction --- p.113 / Chapter 4.2 --- Calculation Method --- p.115 / Chapter 4.3 --- Results and Discussion --- p.116 / Chapter 4.4 --- Conclusions --- p.133 / Chapter References --- p.134 / Chapter Chapter 5 --- High Performance Devices Based on Large-Scale Triphenylene Derived Graphene and Interface Engineering --- p.138 / Chapter 5.1 --- Introduction --- p.138 / Chapter 5.2 --- Experimental Section --- p.140 / Chapter 5.3 --- Results and Discussion --- p.144 / Chapter 5.4 --- Conclusion --- p.163 / Chapter References --- p.164 / Chapter Chapter 6 --- Controllable Modulation of Electronic Properties of Graphene and Silicene by Interface Engineering and Pressure --- p.169 / Chapter 6.1 --- Introduction --- p.169 / Chapter 6.2 --- Modeling and Methods --- p.171 / Chapter 6.3 --- Results and Discussion --- p.174 / Chapter 6.4 --- Conclutions --- p.200 / Chapter References --- p.201 / Chapter Chapter 7 --- Conclusions and Future Plans --- p.204 / Chapter 7.1 --- Conclusions --- p.204 / Chapter 7.2 --- Future Plans --- p.206 / List of Publications during Ph.D. Study --- p.207

The chemistry of the tetrameric low-valent aluminium compoud (Cp*Al)4 (Cp* = 1,2,3,4,5- pentamethylcyclopentadienyl) is relatively undeveloped compared to its monomeric cousin dippNacNacAl (dippNacNac = 2,6-diisopropylphenyl-β-diketiminate). Given that the former can be formed by the reductive elimination of Cp*H from Cp*2AlH, a process common to transition metals yet rare with light main-group elements, using the Cp* ligand could unlock an abundance of unexpected reactivity for aluminium. An overview of the literature regarding the synthesis and reactivity of low oxidation state aluminium compounds is provided in chapter 1, as well as an introduction to relevant magnesium chemistry for this work. Chapter 2 studies the mechanism of C-H reductive elimination from Cp*2AlH to form (Cp*Al)4, and the properties which allow reductive elimination to take place are revealed. A transition state is identified where the Cp* group has a higher hapticity than in the starting material, a process which is thought to enable the reductive elimination. Using this insight, aluminium hydride and halide complexes featuring 9-methylfluorenyl ligands are synthesised and reduction of the aluminium centre is investigated. The reactivity of (Cp*Al)4 is considered in chapter 3 of this thesis. The formal cycloaddition reaction between (Cp*Al)4 and diphenylacetylene produces a Lewis acidic 1,4- dialuminacylohexadiene derivative. The inner Al2C4 ring of this complex is stable, with onward reactions happening at the complex's periphery. Insertion reactions in the Al-CCp* bonds are observed with unsaturated C-N species. With 2,6-dimethylphenylisonitrile the Al2C4 complex forms a zwitterionic aluminate, featuring a stable carbocation derived from the Cp* group. An amidinate complex with an unusual Cp* backbone is formed from the insertion of carbodiimides into the Al-CCp* bond of the 1,4-dialuminacyclohexadiene. Extending this, the insertion of carbon dioxide into the same bond is explored. The use of amidine ligands is common in main-group chemistry, however literature relating to the related phosphaamidinate ligands ([RPC(R)NR]-) is only reported sporadically. They have not been applied in a general manner to main-group chemistry thus far. Chapter 4 describes the synthesis of five new phosphaamidinate pro-ligands where the steric bulk of both the phosphorus and nitrogen components is increased systematically. To evaluate these new ligands, their coordination chemistry with magnesium was investigated. Three examples of heteroleptic LMgnBu (L = phosphaamidinate) complexes are synthesised, which all show high activity for the ring-opening polymerisation of racemic lactide. The resulting polylactide chains show good molecular weights and polydispersity indices. The synthesis of homoleptic L2Mg complexes is also described. Chapter 5 applies these new phosphaamidinate ligands to aluminium chemistry. An aluminium hydride species is isolated, which is shown to form via a probable lithium aluminate intermediate. The lifetime of this intermediate is found to be heavily dependent on the reaction solvent.

nÃo hà / Este trabalho trata de um estudo de caso que tem como objetivo investigar os efeitos da usura e do anatocismo no processo de endividamento bancÃrio em uma amostra de 60 operaÃÃes de crÃdito. Todas as observaÃÃes sÃo devedores inadimplentes e aguardando decisÃo judicial pertinentes à comarca de ParnaÃba, norte do estado do PiauÃ, tendo operaÃÃes contratadas no perÃodo de 1994 a 2003. Foi feita uma breve anÃlise dos aspectos histÃricos, jurÃdicos e econÃmicos da polÃtica de crÃdito no Brasil envolvendo os setores rural, comercial e industrial, declinando sobre os aspectos legais da cobranÃa bancÃria ante a conjuntura econÃmica. Como metodologia, utilizou-se uma pesquisa de campo, realizada com os 60 mutuÃrios quando do ajuizamento das operaÃÃes para auxiliar na avaliaÃÃo dos efeitos da usura e do anatocismo quanto à evoluÃÃo das dÃvidas. A conclusÃo a que se chegou à que a usura e o anatocismo foram fatores que contribuÃram para que tais operaÃÃes chegassem à situaÃÃo de inadimplÃncia. Ressalte-se, porÃm, que o poder de generalizar tais resultados à limitado, dada a falta de informaÃÃo do efeito da usura e do anatocismo sobre os tomadores adimplentes. / This case study aims to investigate the effects of usury and compound interest in the process of acquiring bank debt. The sample was made up of sixty (60) credit transactions, initiated from 1994-2003, all of which are in default and awaiting judicial rulings in the district court of ParnaÃba. A brief analysis of the historical, judicial and politico-economical aspects of credit in Brazil relating to the rural, commercial and industrial sectors is included with emphasis given to the legal aspects of debt collection and economic status. As methodology, a field study was undertaken, achieved with the sixty (60) borrowers during their judgment in order to assist the evaluation of the effects of usury and compound interest in the evolution of the debts. The conclusion reached is that usury and compound interest application were factors that contributed to the debt arriving at the point of default. It should be emphasized, however, that the power of said result does not extend to any and all type of credit transaction.

Esta dissertação investiga o comportamento do acento nos compostos do idioma japonês. Os compostos do japonês falado em Tóquio apresentam apenas um acento, ou queda tonal H*L, por frase fonológica. Isso faz com que não se possa manter os acentos que estariam originalmente nas palavras simples. Apenas um acento sobrevive e seu local é de difícil determinação, porque, na maioria das vezes, não coincide com o local do acento anterior. Muitos linguistas já se debruçaram sobre esse tópico (McCAWLEY, 1965; SAITOU, 1997; KUBOZONO, 2001; TANAKA, 2001; LABRUNE, 2012) e com o auxílio dessas diferentes pesquisas, conseguimos estabelecer que diversos fatores influenciam no processo de acentuação dos compostos, especialmente aspectos morfológicos e fonológicos, como a fronteira de palavra e o pé fonológico. Assim, a acentuação do japonês não é determinada por cada membro do composto, mas pela distância em que a fronteira entre os membros está da margem direita da palavra. / This dissertation investigates the behavior of the accent of Japanese compounds. Compounds in Tokyo Japanese only have one accent, or pitch drop H*L, in a phonological phrase. Therefore, it cannot maintain the accent of the simple words which make it up. Only one accent survives and its location is hard to determine, because, most of the time, it does not coincide with the location of the previous accents. Many linguists have tackled this topic (McCAWLEY, 1965; SAITOU, 1997; KUBOZONO, 2001; TANAKA, 2001; LABRUNE, 2012) and with the help of these different analyses, we established that several factors influence the accentuation of a compound, especially morphological and phonological aspects, such as word boundary and phonological feet. Thus, the accentuation of Japanese compounds is not determined by each member of the compound in particular, but from the distance that the boundary between the compound \'s member is from the right margin of the word.

Benzodiazepines (Benzos) and ketamine (K) are compounds that have been encountered in Drug-Facilitated Sexual Assault (DFSA) cases. Due to the intimate nature of these crimes, evidence collection is often postponed due to delays and/or reluctance in reporting these crimes. Further delays in analysis may be encountered in laboratories with large caseloads and/or backlogs. Drug identification in biological samples is important to determine whether victims knowingly or unknowingly took an impairing substance, however, the results could be negative due to chemical degradation over a long storage period. The purpose of this project was to study if degradation could be prevented with a new preservation method at the time of collection. Urine samples were prepared by the addition of K and metabolites and selected benzos and metabolites that were subjected to different sample pre-treatment techniques, and were analyzed after storage at room temperature (25°C), refrigerator (4°C) and freezer (-20°). The samples were either pre-treated with preservative (0.5% toluene) or filtration sterilization (sterile filter kit) within two hours after sample collection, and a control group with no pre-treatment was incorporated into the study for comparison. The changes in concentrations over 50 days (Benzos group) and 210 days (K group) were evaluated between different pre-treated methods and different temperature conditions. Sample that were treated with 0.5% toluene showed the most degradation: 44% of oxazepam and 96% of diazepam degraded over 10 days, and 80% of dehydronorketamine degraded after storage of 150 days regardless the temperature conditions. Clonazepam and flunitrazepam concentrations were reduced by 80% of the original concentration when stored at room temperature for 10 days. The major benzodiazepines evaluated in this study were stable when stored in the freezer. In K group, ketamine and norketamine that were stored at room temperature and refrigerated over 210 days were stable, however, degradation was observed after 150 days when the samples were stored in the freezer. There was no statistically different change observed among the samples pre-treated with or without filtration sterilization. Each sample pH was measured and it was determined that those stored at room temperature had an average pH of 8.5, while samples stored in the refrigerator and freezer had an average pH of 6.7 and 6.5, respectively. This finding revealed that pH could be the major factor affecting compound degradation rather than the bacterial contamination with high pH contributing to degradation, and low pH potentially preventing sample lost.

abstract: Deformation during hydration of concrete includes curling at joints and terminations. Previous research has explored mix designs, chemical additives, and other material factors to minimize slab distortion due to curling. This research study explores the development and use of externally applied silicone-based compounds after both the placing and cutting of joints. This exploratory study presents the results of controlled testing and a field study results that include distortion of contraction joints as measured with a Spectra LL300N under existing environmental conditions. Specifically, the study presents the results of a side-by-side test of two slabs, a base case, and a silicone-altered case, as well as field measures of two large commercial buildings using the developed methods. The results of the study show reduced distortion due to curling as compared to standard comparative slabs and warrant the continued exploration and testing of the concept. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

The ability of Mercuric Iodide (HgI2) to function as a highly efficient radiation detector at room temperature has generated great interest and has triggered further studies on this difficult material. This property is expected to enable significant enhancements to a far-ranging variety of applications and systems. HgI2 devices have shown superior performance at room temperature compared to elemental Si or Ge devices, which require to be cooled down to liquid nitrogen temperature when used as nuclear radiation detectors. While substantial studies have been conducted on single crystal HgI2, polycrystalline HgI2 remains a comparatively less studied form of this material. The primary use of HgI2 is as a direct radiation detector. It can also be used in applications with a scintillator intermediate to generate visible light from incident nuclear radiation. Hence its response to visible light can be used to study the electronic properties of HgI2 polycrystalline films. The films are deposited on TEC-15 LOF glass with a Tin Oxide(Sn02) coating which acts as the growth surface. It also acts as the front contact with Palladium (Pd) being the back contact. Wire leads are attached to the palladium for electrical contact. The deposited films are circular in shape with a diameter of 2.5cm with thickness ranging from 50 to 600µm. A maximum of 7 devices are contacted at various points on every film. For the measurements documented in this thesis, a tungsten-halogen lamp and an Oriel 1/4m grating monochromator are used as a light source. The incident flux on the sample is determined using a Si photodiode as reference. Device performance for both single crystal as well as polycrystalline films is documented. We have attempted to identify a set of optimum growth parameters using these measurements. For a film to be considered favorably, not only should the individual devices show high quantum efficiencies and low dark currents, but the response of all devices on the same film should be uniform. A number of films are studied and the optimum film deposition conditions are commented upon. A powerful semiconductor device simulation tool, MEDICItm, is used to simulate the photoresponse of these films. The simulations are compared to the measurements and the transport and light absorption parameters of the polycrystalline films are determined.

Dissolved organic matter (DOM) is the most dynamic and least understood part of the global oceanic carbon cycle. Furthermore the molecular composition of DOM is largely unknown. This study focused on the distribution pattern, removal processes and molecular characterisation of DOM in a range of estuaries and coastal zones in New Zealand. Doubtful Sound, the longest fjord in Fiordland National Park, South Island, New Zealand was of particular interest, because of the combination of extreme rainfall, enhanced production of DOM within the temperate rainforest which largely appears in the relatively deep ([greater than or equal to] 5 m) low salinity layer (LSL) at the fjord surface. A typical river estuary (Freshwater River) located in Stewart Island, New Zealand was also investigated. Optical water properties such as the UV/Vis absorption coefficient at 355 nm (a[CDOM](355)) and excitation-emission matrix fluorescence (EEM) were determined for samples from freshwater, across the LSL into open ocean water. These optical properties showed a marked decrease with salinity and highest levels of EEM fluorescence and a[CDOM] (355) in the brackish surface water. In addition to the observed changes in the optical properties, ultrahigh resolution Electrospray Ionisation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS) determination of molecular formulae revealed that in the fjord about 20 % of these formulae changed along a vertical salinity gradient across the LSL between the brackish surface water and the saline water at 5 m depth. This trend was even more pronounced along the salinity gradient of the Fresh Water River Estuary in Stewart Island, where 60 % of all assigned molecular masses changed from freshwater over the mixing zone to ocean water. Associated with these changes was a marked increase in aromaticity with increasing salinity. Comparable behaviour with increasing salinity was also observed in estuarine samples from the Cape Fear River system, North Carolina, USA. In contrast, only minor changes were determined in molecular formulae for surface water samples collected along a transect off the Otago Coast and across the Subtropical Convergence (STC) into Subantarctic Water (SAW). However, a comparison of the molecular formulae assigned to the DOM pool for the STC water and a freshwater stream in Doubtful Sound, revealed that 75 % of all the assigned formulae for the open ocean sample were common to these two markedly different types of natural waters. This seemingly refractory DOM contained nearly 600 assigned molecular formulae, which were all very similar (only spaced by two hydrogen and CH₂ groups) and could be explained with only 9 general molecular formulae. However, the comparison of all assigned formulae for the freshwater sample suggested that about 90 % of the assigned molecular formulae for the terrestrially-derived DOM changed as it moved from rivers to the open ocean and that only 10 % remained the same. Singlet oxygen showed a very close relationship with the optical properties such as the absorption coefficients (a[CDOM](355)) and the EEM fluorescence intensities and these results suggested that singlet oxygen steady state concentrations are linked to CDOM. Photodegradation processes were confirmed to be responsible for a significant destruction of CDOM. Samples collected from different salinity waters showed major differences in wavelength-dependent photo-decay of CDOM suggesting that the rate of photodegradation in the UV range decreased with increase in salinity whereas it was enhanced for longer wavelength radiation ([greater than or equal to]400 nm). Additionally, the predominantly unsaturated compounds produced during estuarine mixing were found to be highly photolabile and were either destroyed or new unsaturated compounds were produced within 21 h of solar irradiation.

<p>To be able to ensure quality, efficiency and safety in nuclear reactors, non-destructive evaluations (NDE) are performed. The moulding technique, which has been studied in this project, is an NDE method used to verify surface breaking cracks at various objects in reactor vessels.</p><p>The idea of moulding is to receive a copy of the replicated surface for microscopic analysis. Within forensic science the moulding technique is used at crime scenes to collect evidence and tie suspects to crimes. Underwater moulding, however, is a newly developed technique and WesDyne TRC is a pioneer in offering services within moulding for underwater purposes.</p><p>This project was initiated by WesDyne TRC to further their knowledge within the moulding technology. In the project, studies have been made at three important parameters effect on cast quality using three different polymer compounds. Problems during moulding, such as crack detection failures and bubbles in the casts, raise the question whether the underwater moulding technique can be trusted to detect cracks.</p><p>Results from the experiments led to a greater insight into the problem with receiving high quality casts during underwater moulding. Only if a satisfactory cast is made, the moulding method can be trusted to detect defects down to the detection target in both dry and wet environment.</p><p>To increase the surface quality of underwater casts a suggestion for mould design and a recommended moulding method was developed. In addition, one of the polymer compounds approved for use, turned out not to be suitable for underwater moulding.</p>

Over the last decade, endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs) have been detected in drinking water at very low levels, mostly ng/L concentrations, suggesting that these compounds resisted removal through water treatment processes. Concerns have been raised regarding the effectiveness of common drinking water treatment technologies to remove these emerging contaminants. Adsorption processes were suggested to play an important role in the removal of PhACs and EDCs, based on the assumption that these compounds are similar to other conventional micropollutants such as pesticides in both physicochemical properties and concentration levels present in water. However, this remains to be demonstrated since the availability of adsorption data for PhACs and EDCs is extremely limited and their environmental concentrations are typically much lower than the ones for pesticides. The primary objective of this research was to evaluate in detail the removal of representative EDCs and PhACs at environmentally relevant concentrations by granular activated carbon (GAC) adsorption. In the first stage of this study, EDCs (15) were screened separately from the PhACs (86) with two different sets of assessment criteria due to the different nature and the availability of information for these two groups of compounds. As a result, 6 EDCs and 12 PhACs were selected for further evaluation. Subsequently, a multi-residue analytical method based on gas chromatography/mass spectrometry (GC/MS) was developed for the simultaneous determination of the selected PhACs and EDCs. Two key analytical steps - solid phase extraction and derivatization - were systematically optimized using full factorial design and a central composite design, respectively. The statistical experimental design in combination with the concept of the total desirability was demonstrated to be an effective tool for developing a multi-residue analytical method. The application of the developed method to Grand River water, a local raw water source, and finished drinking water from this source indicated that PhACs such as naproxen, carbamazepine, salicylic acid, ibuprofen, and gemfibrozil, and EDCs such as estrone (E1) and nonylphenol mono-ethoxy carboxylate (NP1EC) were the most common contaminants. Based on these results, the quality of the analytical data, and the physicochemical properties relevant to the adsorption on activated carbon, two PhACs (naproxen, carbamazepine) and one EDC (nonylphenol (NP)) were finally chosen for the adsorption studies. Adsorptions of the selected target compounds were evaluated on two types of activated carbon (coal-based Calgon Filtrasorb® 400 (F400) and coconut shell-based PICACTIF TE (PICA) by first investigating their isotherms at environmentally relevant concentrations (equilibrium liquid phase concentration ranging from 10 to 1000 ng/L). The single-solute isotherm data determined for both carbons showed that the relative adsorbabilities of the three target compounds were not in agreement with expectations based on their log Kow values. Overall, in this low concentration range, carbamazepine was most easily removed, and NP was least adsorbable. The adsorption of naproxen was negatively influenced by its dissociation in water. Comparison of single-solute isotherms on F400 carbon for the target compounds to those for other selected conventional micropollutants showed that naproxen and carbamazepine have generally comparable isotherms to 2-methylisoborneol (MIB) and geosmin. The isotherm tests in a post-sedimentation (PS) water from a full-scale plant demonstrated that the presence of background natural organic matter (NOM) significantly reduced the adsorption of all three target compounds, among which.NP was the least impacted compound. Based on the quantification of the direct competition using the ideal adsorbed solution theory (IAST) in combination with the equivalent background compound (EBC) approach, the minimum carbon usage rates (CURs) for removing 90% of the target compounds in PS water were calculated at two environmentally relevant concentrations (50 and 500 ng/L). This work confirmed that the percentage removal of the trace level target compound at a given carbon dosage was independent of the initial target compound concentration. Isotherm experiments were conducted for the target compound on GACs preloaded with PS water for various time intervals (up to 16 weeks) at the Mannheim Water Treatment Plant (Region of Waterloo, ON, Canada). The results indicated that the adsorption of all target compounds were subject to significant negative impacts from preloading of NOM, albeit to different extents. Among the three target compounds, reduction in adsorption capacity for naproxen was most severe, followed by carbamazepine and then NP. The three target compounds followed quite different patterns of decrease in adsorption capacity with increasing preloading time, thus revealing different competitive mechanisms at work for the different compounds. For naproxen, the change in heterogeneity of the carbons due to preloading suggests that some pre-adsorbed NOM could not be replaced by naproxen. However, both direct competitive and pore blockage mechanisms could successfully explain the adsorption performance of naproxen and carbamazepine. The removal of NP even at prolonged preloading times could be explained by absorption or partitioning in the NOM matrix on the surface of, or inside the carbons. The kinetic parameters for each target compound-virgin carbon pair were determined using the short fixed bed (SFB) approach based on the pore and surface diffusion model (PSDM). The SFB results and sensitivity analyses indicated that, under the very low influent concentration conditions, film diffusion (indexed as βL) exerts a much greater effect on breakthrough profiles than internal diffusion. The SFB tests on preloaded GACs showed that mass transport of all the target compounds decreased with increasing preloading time. Similar to the impact of preloading on adsorption capacity, naproxen was subject to the most deteriorative effect, followed by carbamazepine and then NP. In addition, potential mechanisms for the decay of the film diffusion coefficient with increased preloading time were discussed based on scanning electron microscope (SEM) images of virgin and preloaded GAC. Electrostatic interactions between the NOM/bio film formed on the preloaded carbon and dissociated naproxen may have contributed to the enhanced reduction in its film diffusion. Sensitivity analyses and subsequent calculations of the Biot numbers confirmed that film diffusion was also the predominant mechanism controlling the mass transport on preloaded carbon, in particular for naproxen. This suggests that the early breakthrough prediction of the target compounds at their environmentally relevant concentrations could be further simplified by only considering film diffusion and adsorptive capacity. Kinetic and isotherm parameters were used as input for modeling using time-variable PSDM. It was found that the varying trends for Freundlich KF and 1/n, and βL could be generally depicted by a corresponding empirical model. Pilot scale treatability tests were performed for the target compounds which subsequently validated the time-variable PSDM results thus demonstrating its effectiveness and robustness to model GAC adsorber performance for PhAC and EDC removal at environmentally relevant concentrations. The time-variable approach was further improved by adjusting for NOM surface loading differences between the preloading and the pilot columns, which successfully compensated for the prediction errors at the early phase. The validated NOM surface loading associated time variable PSDM was used to predict performances of hypothetical F400 and PICA full-scale adsorbers. Both adsorbers were expected to provide satisfactory performance in achieving 90% removals for the neutral target compounds (carbamazepine and NP). Naproxen was predicted to break through fast since both, capacity and kinetic parameters decay quickly due to carbon fouling by NOM and the physicochemical properties of this compound. Initial recommendations on the choice of adsorption process (GAC vs. PAC) for removing EDCs and PhACs can be made based on the comparison of carbon usage rates (CUR) which were calculated for a GAC adsorber using the validated improved PSDM and for PAC using the minimum applied dosages predicted by the IAST-EBC model.