Flexible polyurethane foam (PUF) is a very versatile material ever created. The material is used for various applications and consumer end-use products such as upholstered furniture and mattresses. The increased use of these polymeric materials causes fire safety concerns. This has led to the development of various regulations and flammability test standards aimed at addressing the hazards associated with polyurethane foam fires. Several fire protection engineering correlations and thermal models have also been developed for the simulation of fire growth behaviour of polyurethane foams. Thus, the overall objective of this research project is to investigate the laboratory test behaviour of this material and then use finer modeling techniques to predict the heat release rate of the specimens, based on information obtained from cone calorimeter tests.<p> Full-scale fire tests of 10 cm thick polyurethane foams of different sizes were conducted using center and edge-ignition locations. Flame spread and heat release rates were compared. For specimens of the same size, center-ignition tests produced flame areas and peak heat release rates which were respectively 10 and 20% larger compared to edge-ignition tests. Average flame spread rates for horizontal and vertical spread were determined, and results showed excellent agreement with literature. Cone calorimeter tests of the specimens were performed using steel edge frame and open durarock board. Results indicate that different test arrangements and heat sources have significant effects on the fire behaviour of the specimens.<p> Predictions using the integral convolution model and other fire protection engineering correlations were compared with the full-scale tests results. Results show that the model was more efficient in predicting the heat release rates for edge-ignition tests than the center-ignition tests. The model also was more successful in predicting the heat release rates during the early part of the growth phase than during the later stages of the fire. The predicted and measured peak heat release rates and total heat release were within 10-15% of one another. Flame spread and t-squared fire models also gave satisfactory predictions of the full-scale fire behaviour of the specimens.

Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

<p>A GL(2,R)-structure on a smooth manifold of dimension n+1 corresponds to a distribution of non-degenerate rational normal cones over the manifold. Such a structure is called k-integrable if there exist many foliations by submanifolds of dimension k whose tangent spaces are spanned by vectors in the cones.</p><p>This structure was first studied by Bryant for n=3 and k=2. The work included here (n=4 and k=2,3) was suggested by Ferapontov, et al., who showed that the cases (n=4,k=2) and (n=4, k=3) can arise from integrability of second-order PDEs via hydrodynamic reductions.</p><p>Cartan--Kahler analysis for n=4 and k=3 leads to a complete classification of local structures into 54 equivalence classes determined by the value of an essential 9-dimensional representation of torsion for the GL(2,R)-structure. These classes are described by the factorization root-types of real binary octic polynomials. Each of these classes must arise from a PDE, but the PDEs remain to be identified. </p><p>Also, we study the local problem for n >= 5 and k=2,3 and conjecture that similar classifications exist for these cases; however, the interesting integrability results are essentially unique to degree 4. The approach is that of moving frames, using Cartan's method of equivalence, the Cartan--Kahler theorem, and Cartan's structure theorem.</p> / Dissertation

<p>Cone beam computed tomography (CBCT) is a 3D x-ray imaging technique in which the x-ray beam is transmitted to an object with wide beam geometry producing a 2D image per projection. Due to its faster image acquisition time, wide coverage length per scan, and fewer motion artifacts, the CBCT system is rapidly replacing the conventional CT system and becoming popular in diagnostic and therapeutic radiology. However, there are few studies performed in CBCT dosimetry because of the absence of a standard dosimetric protocol for CBCT. Computed tomography dose index (CTDI), a standardized metric in conventional CT dosimetry, or direct organ dose measurements have been limitedly used in the CBCT dosimetry.</p> <p>This dissertation investigated the CBCT dosimetry from the CTDI method to the organ, effective dose, risk estimations with physical measurements and Monte Carlo (MC) simulations.</p> <p>An On-Board Imager (OBI, Varian Medical Systems, Palo Alto, CA) was used to perform old and new CBCT scan protocols. The new CBCT protocols introduced both partial and full angle scan modes while the old CBCT protocols only used the full angle mode. A metal-oxide-semiconductor-field-effect transistor (MOSFET) and an ion chamber were employed to measure the cone beam CTDI (CTDI_CB) in CT phantoms and organ dose in a 5-year-old pediatric anthropomorphic phantom. Radiochromic film was also employed to measure the axial dose profiles. A point dose method was used in the CTDI estimation.</p> <p>The BEAMnrc/EGSnrc MC system was used to simulate the CBCT scans; the MC model of the OBI x-ray tube was built into the system and validated by measurements characterizing the cone beam quality in the aspects of the x-ray spectrum, half value layer (HVL) and dose profiles for both full-fan and half-fan modes. Using the validated MC model, CTDI_CB, dose profile integral (DPI), cone beam dose length product (DLP_CB), and organ doses were calculated with voxelized MC CT phantoms or anthropomorphic phantoms. Effective dose and radiation risks were estimated from the organ dose results.</p> <p>The CTDI_CB of the old protocols were found to be 84 and 45 mGy for standard dose, head and body protocols. The CTDI_CB of the new protocols were found to be 6.0, 3.2, 29.0, 25.4, 23.8, and 7.7 mGy for the standard dose head, low dose head, high quality head, pelvis, pelvis spotlight, and low dose thorax protocols respectively. The new scan protocols were found to be advantageous in reducing the patient dose while offering acceptable image quality.</p> <p>The mean effective dose (ED) was found to be 37.8 ±0.7 mSv for the standard head and 8.1±0.2 mSv for the low dose head protocols (old) in the 5-year-old phantom. The lifetime attributable risk (LAR) of cancer incidence ranged from 23 to 144 cases per 100,000 exposed persons for the standard-dose mode and from five to 31 cases per 100,000 exposed persons for the low-dose mode. The relative risk (RR) of cancer incidence ranged from 1.003 to 1.054 for the standard-dose mode and from 1.001 to 1.012 for the low-dose mode.</p> <p>The MC method successfully estimated the CTDI_CB, organ and effective dose despite the heavy calculation time. The point dose method was found to be capable of estimating the CBCT dose with reasonable accuracy in the clinical environment.</p> / Dissertation

The design of interface elements in geotechnical engineering traditionally involves empiricism and lacks a solid fundamental underpinning based on the controlling mechanisms. These design shortcomings exist due to deficiencies in the fundamental understanding of geotechnical interface behaviors and the lack of test methods and devices available to directly measure interface properties in situ. The current work strives to improve the state of geotechnical knowledge and design with regard to interface behavior through fundamental laboratory studies and the development and use of a new in situ testing device. The current investigations are focused across a range of scales from micromechanical interactions to full scale field implementation. A series of laboratory investigations at the micromechanical level have been performed, specifically aimed at investigating the mechanisms controlling granular interactions against conventional and textured friction sleeves, and hook and loop type interactions present within textured geomembrane - geotextile systems. Additionally, a new in situ testing device has been designed and developed, the Multi Piezo Friction Attachment (MPFA), to allow for the characterization of geotechnical interface properties in situ within the context of an effective stress framework. The MPFA simultaneously provides four independent measures of interface friction (f

The concepts of continuity for set-valued mappings were introduced by G. Bouligand and K. Kuratowski. There are two ways defining differentiability of set-valued mapping. One is defined by classical differentiability theorem and another is defined by normal cone which was introduced by B.S. Mordukhovich. In this thesis, we survey various definitions of continuity and differentiability for set-valued mapping.

In this thesis, we consider receiver design problems in a multi-cell MIMO system using the coordinated multi-point transmission/reception technique. The linear minimum mean square error (LMMSE) receiver, which involves the inverse operation, is adopted. By the Cayley-Hamilton theorem, the matrix inverse can be represented by weighted sum of power of matrices. Given an order of the matrix power, we calculate the best weight in sense of the minimum mean square error. Both the uplink and the downlink scenarios are considered. Also, given a target signal to interference and noise ratio (SINR), we consider the best weight design problem in the downlink scenario. This problem can be formulated as the second-order cone programming (SOCP) and semidefinite relaxation (SDR) programming. By computer simulations, we show that the SDR and SOCP are equivalent.

Soil properties (shear modulus and damping) are normally determined from laboratory tests. These tests provide both values of the shear modulus in the linear elastic range for very small levels of strain, and its variation with the level of strain. It has become more common to measure the maximum shear modulus at low levels of strain directly in the field, using geophysical techniques. The values obtained in situ can differ significantly in some cases from those determined in the laboratory, and a number of reasons and correction factors have been proposed in the literature to account for this variation. As a result, when in situ properties are available, it is normal to use these values for very low levels of strain, but still assume that the variation of the ratio G/Gmax (normalized shear modulus) with shear strain is the same as determined in the laboratory. Recently, tests have been performed using large vibrators (the Thumper and Tyrannosaurus Rex of the University of Texas at Austin) to determine soil properties in situ for larger strains, and the variation of G/Gmax obtained from these tests has been compared to that reported in the literature from lab tests. Observation indicates some generally good agreement, but also some minor variations. One must take into account, however, that in the determination of the shear modulus versus strain in the field from vibration records, a number of approximations are introduced. The objective of this work is to evaluate the accuracy of some the procedures used and to assess the validity of the simplifying assumptions which are made. For this purpose, a shear cone that would reproduce correctly the horizontal stiffness of a circular mat foundation on the surface of an elastic, homogeneous half space, was considered. The cone was discretized using both a system of lumped masses and springs and a finite difference, using second-order central difference formulation, verifying that in the linear elastic range the results were accurate. A number of studies were conducted next, increasing the level of the applied force and using nonlinear springs that would reproduce a specified G/Gmax vs. γ curve. Using a similar procedure to that used in the field tests, the shear wave velocity between hypothetical receivers and the levels of strain were determined. The resulting values of G/Gmax vs. γ were then compared with the assumed curve to assess the accuracy of the estimated values.

Predatory shallow-water tropical marine snails within the genus Conus are estimated to consist of up to 700 species. These carnivorous mollusks have devised efficient venom harpoon-like radular teeth that allow them to predominantly incapacitate polychaete annelids (vermivores), in some cases fish (piscivores), or other mollusks (molluscivores) as an envenomation survival strategy for feeding, defense, and competitor deterrence. The venom of each Conus species contains a distinctive assortment of over 50 diversified disulfide-rich conotoxins with varied pharmacological specificities that selectively inhibit the function of ion channels (Ca2+, Na+, K+) or nicotinic acetylcholine receptors (nAChRs) involved in the animal neurotransmission. Across the genus Conus, the conotoxins represent an extensive array of ion channel blockers each showing an exquisite selectivity to distinguish between channels / receptors and even particular their subtypes. Novel conotoxins detected in the molecular neurobiological approach, providing chemists and pharmacologists a vast library (>50,000 individual toxins) of conotoxins have been further screened for their abilities to modify the responses of tissues to pain stimuli as a first step in describing their potential as lead compounds for novel drugs. In this article, we present the natural history of the Conus biology as well as the nomenclature, classification, structure, neurotoxicological mechanisms, post-translational modification, and pharmaceutical applications of conotoxins. In addition, we also set up the bioinformatic database and search engine about hitherto-identified name and distribution of Conus species and neuropharmacological mechanism, accession number, sequence, and 3D structure of conotoxins and provide researchers advantageous tools for further investigation.

In the first part of this dissertation, glass fiber reinforced/unreinforced polyamide 6 (PA6) and polyamide 66 (PA66) were compounded with three different flame retardants, which were melamine cyanurate, red phosphorus and brominated epoxy with antimony trioxide, by using an industrial scale twin screw extruder. Then, to investigate flame retardancy of these specimens, UL-94, Limiting Oxygen Index (LOI) and Mass Loss Cone Calorimeter (MLC) tests were carried out. In addition to flammability tests, thermogravimetric analysis (TGA) and tensile testing were performed. Results of the tensile tests were evaluated by relating them with fiber length distributions and fracture surface morphologies under scanning electron microscope (SEM). Incorporation of melamine cyanurate (MCA) to PA6 led to some increase in LOI value and minor reductions in Peak Heat Release Rate (PHRR) value. However, it failed to improve UL-94 rating. Moreover, poor compatibility of MCA with PA6 matrix caused significant reductions in tensile strength. Brominated epoxy in combination with antimony trioxide (Br/Sb) was compounded with both glass fiber reinforced PA6 and PA66. Br/Sb synergism was found to impart excellent flammability reductions in LOI value and UL-94 as V-0 rating. Effectiveness of Br/Sb flame retardant was also proven by the MLC measurements, which showed excessive reductions in PHRR and Total Heat Evolved (THE) values. On the other hand, Br/Sb shifted the degradation temperature 100&deg / C lower and decreased the tensile strength value, due to poor fiber-matrix adhesion and decreased fiber lengths. Red phosphorus (RP), when introduced to glass fiber reinforced PA66 induced V-0 rating in UL-94 together with significant increase in LOI value, and major decrease in PHRR. Degradation temperature was 20&deg / C lower while mechanical properties were kept at acceptable values compared to neat glass fiber reinforced PA66. In the second part of this dissertation, to investigate synergistic flame retardancy of nanoclays / glass fiber reinforced PA6 was compounded by certain nanoclay and an organo-phosphorus flame retardant (OP), which contains aluminum phosphinate, melamine polyphosphate and zinc borate, in a laboratory scale twin screw extruder. Exfoliated clay structure of the nanocomposites was assessed by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), while thermal stability and combustion behaviors were evaluated by TGA, LOI, UL-94 and MLC. Replacement of a certain fraction of the flame retardant with nanoclay was found to significantly reduce PHRR and THE values, and delay the ignition. Moreover, remarkable improvements were obtained in LOI values along with maintained UL-94 ratings. Residue characterization by ATR-FTIR and SEM ascribed the enhanced flame retardancy of nanocomposite specimens to the formation of a glassy boron-aluminum phosphate barrier reinforced by clay layers at the nanoscale.