The problem of self-heating of combustible dusts accumulated on hot surfaces has caused several fires and dust explosions. The current test standards (ASTM E 2021, EN50281-2-1) used to ensure safe environment for a given dust, define a safe temperature of the flat hot surface for certain dust layer thickness. Since in these standards, measurement of temperature is taken along the centerline, they mainly represent a simplified scenario of one-dimensional heat transfer. A need to investigate behavior of spontaneous ignition in dust deposits in complex geometries forms the motivation of this work. The effect of hot surface geometry is experimentally studied by devising wedge-shaped configurations having angles of 60o and 90o. Results show that ignition always occurred around the top region in the case of 60o wedge, and in the top and middle regions in the case of 90o wedge. These trends are explained by investigating three parameters affecting the ignition behavior, namely, the heat transfer from the hot plate to the dust, the rate of heat transfer between different regions within the dust and the minimum volume of dust required to produce sufficient heat release. A mathematical method has been proposed to predict the ignition behavior of dust deposit subjected to any boundary conditions arising due to geometrical confinement. Further, numerical simulations have been carried out to simulate the conjugate heat transfer in the interface of dust surface and air. Both analyses, mathematical and numerical, compare well with the experimental data. Furthermore, in the standard test method, ASTM E- 2021, a metal ring is used to contain the sample dusts. It is observed from experimental and numerical simulations that the resultant temperature field is not one-dimensional as desired since the corner part ignites first due to heat transfer from both the bottom plate and the metal ring, which is at almost same temperature as that of bottom plate. Theories those describe the thermal ignition in these standard tests, use the assumption that the heat flow is unidirectional. Therefore, a better substitute to the metal ring has been proposed as a ring made out of an insulating material (having low thermal conductivity). This makes the heat transfer to the dust layer phenomenally one-dimensional. Another leg of the experiments have been carried out to investigate the effect of weathering of combustible dusts on their spontaneous ignition process. Two types of weathering methods, heat- and moisture-weathering are used. Sample preparation and weathering quantification methods follow the standard test procedure. Thermogravimetric analysis has been employed to understand the variation in weight loss of fresh, heat-weathered and moisture-weathered samples of coal and organic dusts. Preliminary results show that heat weathering increases the hazard level for organic (wheat) dust. In summary, the current research work mainly involves modification of the standard test method such as ASTM E-2021 to include an insulated ring instead of a metal ring to ensure one-dimensional heat transfer and extending the test method to include wedge-shaped geometries. The spontaneous ignition of combustible dust in the new setups is investigated thoroughly. Furthermore, mathematical and numerical models have been proposed to simulate the experimental tests. Finally, the effect of two types of weathering processes on the characteristics of spontaneous ignition has been studied. In all the cases, results are thoroughly discussed with the explanation of the physics involved.

At the Castle Creek study area in east-central British Columbia a well-exposed section about 450 m wide and 30 m thick in the (Neoproterozoic) Isaac Formation was analyzed to document vertical and lateral changes in a succession of distinctively heterolithic strata. Strata are interpreted to have been deposited on a deep-marine levee that was sandwiched between its genetically related channel on one side and an erosional escarpment sculpted by an older (underlying) channel on the other. Flows that overspilled the channel (incident flow) eventually encountered the escarpment, which then set up a return flow oriented more or less opposite to the incident (from the channel) flow. This created an area of complex flow that became manifested in the sedimentary record as a highly tabular succession of intricately interstratified sand and mud overlain by an anomalously thick, plane-parallel interlaminated sand-mud unit capped finally by a claystone.

acase@tulane.edu / Ever since the successful isolation of graphene, plenty of researches have been pursued to study fundamental physics in low-dimensional van der Waals materials, referred to as materials with the existence of out of plane vdW force. Not only graphene but also many other novel vdW materials start to emerge and play important roles in quantum physics. Due to the highly preserved crystal quality of the nanostructures achieved by micromechanical exfoliation, a variety of new phenomenon have been discovered in these novel materials. This dissertation focuses on the discovery and electronic properties study of new vdW materials both in 2D and 1D systems. Semiconducting transition metal dichalcogenides with layered structure have been viewed as the promising channel materials for field-effect transistors (FETs) in modern electronics. To characterize the performance, we have fabricated FETs based on multilayer WS2 thin crystals. By using gold as the contact metal and varying the thickness of the crystal, high-performance FETs with on/off ratio of 108 and mobility up to 234 cm2V-1s-1 at room temperature have been realized. The high performance is associated with the minimized Schottky barrier and a shallow impurity level below the conduction band. Elementary substance and binary compound crystals have limited members belong to 2D or 1D family. Thus, expanding the research to ternary compound materials is necessary. In this regard, we focused on a novel ternary compound 2D material Nb3SiTe6 and studied its magneto-transport. We have discovered that by using such a high crystalline 2D metal, we could study the inelastic electron-phonon (e-ph) interactions involved with reducing dimensions. From 3D bulk to 2D films with a rigid substrate, the weak antilocalization (WAL) signature is gradually enhanced according to our magnetoresistance (MR) measurements. Systematic studies of the temperature dependence of the dephasing rate in the crystal with various thicknesses suggest the suppression of electron-phonon interaction due to quantum confinement of the phonon spectrum. Our work shows great consistency with the long-standing predicted theory. We have successfully expanded the mechanical exfoliation method to 1D material group. As demonstrated by semiconducting quasi-1D materials, Ta2Pd3Se8 (TPdS) and Ta2Pt3Se8 (TPtS), the external force can efficiently break the weak vdW interactions between ribbons. In our work, we have produced ultrathin 1D TPdS and TPtS nanowires, and fabricated 1D FETs showing p-type and n-type transistor behavior respectively. Moreover, we have successfully built the functional logic NOT gate using these two different 1D FETs. / 1 / Xue Liu

This thesis examines the world of solitary confinement within the prison system. My research was inspired by Ashley Smith, a 19-year old segregated inmate who died in isolation while seven guards watched. This outrageous occurrence prompted me to question the practice of solitary confinement and a prison system in which such an event could occur. Studying the history of solitary confinement left me surprised to learn that it was originally intended as a therapeutic and merciful alternative to the punishments of the day. This revelation was one of a series of inversions that led me to conclude that solitary confinement is a world apart, not just physically, but also socially, temporally and legally. I have concluded that improving the lives of those segregated within our prisons requires the world of solitary confinement to become anchored within the broader legal and social context.

This thesis examines the world of solitary confinement within the prison system. My research was inspired by Ashley Smith, a 19-year old segregated inmate who died in isolation while seven guards watched. This outrageous occurrence prompted me to question the practice of solitary confinement and a prison system in which such an event could occur. Studying the history of solitary confinement left me surprised to learn that it was originally intended as a therapeutic and merciful alternative to the punishments of the day. This revelation was one of a series of inversions that led me to conclude that solitary confinement is a world apart, not just physically, but also socially, temporally and legally. I have concluded that improving the lives of those segregated within our prisons requires the world of solitary confinement to become anchored within the broader legal and social context.

Graduation date: 1993

This study highlights the role of humanitarian diplomacy to obtain humanitarian access to civilian victims of forced confinement in the municipality of Samaniego, Colombia. Humanitarian diplomacy is made of humanitarian negotiations, coordination and advocacy to provide suffering-alleviation to victims of armed conflicts, and these components will be discussed thoroughly. To inquire in the use of humanitarian diplomacy by international relief organizations, interviews with thirteen humanitarian workers, two public officers and a human rights worker were conducted. The findings, which are complemented with humanitarian and human rights reports and framed in the theoretical discussion, will be the base to discuss whether humanitarian diplomacy contributed to gain humanitarian access in villages of Samaniego facing restrictions in the mobility of civilians and limitations in the supply of basic means of livelihood and humanitarian assistance.

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Electron heat transport at the scale of electron gyroradius are investigated via numerical simulation of a fluid model and a role of E x B shear flow with intermediate E x B shearing rate is explored in Euler's equation. The anomalous transport, enhanced transport due to turbulent electro-magnetic fields caused by plasma instabilities, has been a focus of the inter-national fusion research communities. Among the instabilities, the drift-type instabilities from the pressure-gradient universal in magnetic fusion devicesare considered responsible for the anomalous transport. In the current status of wide use of wave heating on electrons and subsequent high core electron temperature, the turbulent heat loss through electrons has one of the most important science element in preventing the large fusion tokamaks from reaching breakeven in the past decade. The Electron Temperature Gradient fluid model consists of electrostatic potential, toroidal magnetic flux function and electron temperature (or pressure) describing electron drift waves. The fluid model proves to be highly useful to electron heat flux analysis in fusion machines. We analyze the discharges in National Spherical Tokamak eXperiment(NSTX) and Tokamak Configuration Variable (TCV) and found that the electron thermal diffusivities can be explained in terms of the mixing length argument based on electron gyroradius, linear theory and our nonlinear fluid simulation. The nonlinear fluid model predicts reasonable heat flux observed in the experiments. Based on the analysis, we investigate the dependences of the dynamics on the ratio of electron and ion temperature T[subscript e]/T[subscript i] and plasma beta [beta subscript e-]. The nonlinear dynamics such as saturation mechanism of the ETG turbulence and the electromagnetic dynamics in terms of micro-tearing at the scale of electron gyroradius are discussed briegly. In most of plasma confinement devices, the equilibrium radial electric field exists and the turbulence-generated electric field is observed. The coherent structure, called as zonal flow, has been know to be effective to suppress the micro-turbulence. But at intermediate E x B shear, where the vortex eddy turn-over time is comparable to E x B shearing rate, the suppression is weak and the flow shear can leads to vortex amplification through interaction of nonlinear dynamics and shear flow. / text

Alfalfa is an important forage crop in North America which can also escape cultivation and establish in unmanaged habitats. Genetically modified (GM) alfalfa has been approved for environmental release in Canada and the United States and the occurrence of alfalfa in unmanaged natural and semi-natural habitats may compromise the successful co-existence of GM and non-GM alfalfa. To-date, little information has been available on the nature and dynamics of roadside alfalfa populations and their ability to become feral. Such knowledge is necessary to design efficient trait confinement protocols and to enhance the co-existence of GM and non-GM alfalfa within agricultural regions. The overall aim of this work was to characterize roadside alfalfa populations and to establish their role in novel trait movement. A roadside survey revealed the widespread occurrence of feral alfalfa populations in southern Manitoba. We described the seedbanks of roadside alfalfa populations, seedling recruitment and adult reproductive success, indicating that alfalfa is capable of establishing self-perpetuating feral populations in unmanaged habitats. We also noted the successful establishment of alfalfa in a grass sward representing roadside vegetation. Roadside mowing can reduce (and perhaps prevent) seed production in roadside alfalfa; however, mowing failed to drive the populations to extinction in the short-term. Herbicide (2,4-D) applications controlled alfalfa plants but seeds in the seedbank may still contribute to new seedling recruitment. The roadside alfalfa populations we worked with exhibited high levels of genetic diversity, indicating an absence of past population bottlenecks or genetic drift. In addition, phenotypic characterization provided evidence that roadside alfalfa populations were experiencing selection pressure for adaptive traits including winter survivability, rhizome production and prostrate growth habit; all traits that favor persistence in unmanaged habitats. We also noted the occurrence of high (>60%) levels of outcrossing in feral alfalfa populations, establishing their role as sources and sinks for novel traits. Our findings indicate that alfalfa populations occurring in unmanaged habitats need to be considered in trait confinement protocols in order to reduce the adventitious presence (AP) of novel traits and to enhance the successful co-existence of GM and non-GM alfalfa.