No description available.

Made available in DSpace on 2014-10-09T12:54:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:45Z (GMT). No. of bitstreams: 0 / A avaliação do desempenho dos detectores termoluminescentes de CaSO4:Dy, produzidos pelo IPEN, tem como objetivo apresentar uma alternativa aos dosímetros de LiF:Mg,Ti comerciais (TLD-100), amplamente empregados em radioterapia, na dosimetria de feixes clínicos de elétrons. Os dois tipos de detectores termoluminescentes foram caracterizados, com a utilização de objetos simuladores de PMMA, água sólida do tipo RMI-457 e água, em campos de radiação de elétrons de 4, 6, 9, 12 e 16 MeV de energias nominais, nos quais as curvas de dose-resposta foram obtidas e as doses superficial e profunda foram determinadas. A dependência da resposta termoluminescente com a energia nominal dos elétrons e com o objeto simulador empregado foram estudadas. O CaSO4:Dy apresentou o mesmo comportamento do LiF:Mg,Ti; de maneira que sua aplicação como uma alternativa às pastilhas TLD-100 na dosimetria de feixes de elétrons em radioterapia é viável e apresenta a sensibilidade à radiação de elétrons significativamente mais alta como principal vantagem. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:37:22Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:16Z (GMT). No. of bitstreams: 1 02037.pdf: 3257325 bytes, checksum: 6f7184b35c6dddcd40410864962f58fe (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

No description available.

The present approach to the design of prestressed beams is antiquated and time consuming. Neither SLS or ULS requirements are satisfied directly. There is a need for a new approach using plastic principles to design the prestressing requirements at ULS considering a whole span at a time, with checks made for SLS requirements afterwards. For a plastic design, the designer would need to know the limits of the bending moment redistribution for the beam under consideration. An equation is therefore necessary to assist the designer in this regard. Such an equation should take into account the cross-section shape of the beam and the prestress to reinforcing steel ratios. Many examples would have to be investigated using a rigorous plastic analysis to formulate such an equation. A computer program has been written as part of this thesis to perform such a rigorous analysis. It's accuracy has been evaluated by comparison with laboratory test beam results. The comparison was favourable, although more results would have to be compared to establish the accuracy that could be expected. A few examples were investigated and the observations noted. Two extreme cases were examined, those of a T-beam and I-beam. The redistribution of bending moments was similar in both cases, but the percentage of the central moment capacity reached was considerably less for the T-beam. For both beams it was impossible to reach the ultimate capacity at the centre before the strain capacity at the supports was exhausted. It was concluded that a plastic design procedure should be introduced, based on the ULS capacity of a span at a time. SLS requirements could then be checked afterwards. This approach would provide a design procedure corresponding to those used for other forms of modern structural design and would be much quicker, safer, more accurate and less costly that the existing design procedures.

In proton therapy systems with pencil-beam scanning, output of Halo effect is not necessarily included in Treatment Planning System (TPS). Halo effect (low-intensity tail) can significantly affect a patient’s dose distribution. The output of this dose depends on the field size being irradiated. Although much research has been made to investigate such relation to the field size, the number of reports on dose calculations including the halo effect is small. In this work we have investigated the Halo effect, including field size factor, target depth factor, and air gaps with a range shifter for a Varian ProBeam. Dose calculations created on the Eclipse Treatment Planning System (vs15.6 TPS) are compared with plane-parallel ionization chambers (PTW Octavius 1500) measurements using PCS and AcurosPT MC model in different isocenters: 5cm, 10cm, and 20cm. We find that in AcurosPT algorithm deviations range between -7.53% (for 2cm field in 25cm air gap with range shifter) up to +7.40% (for 20cm field in 15cm air gap with range shifter). Whereas, in PCS algorithm the deviations are -2.07% (for 20x20cm field in open conditions) to -6.29% (for 20x20cm field in 25cm air gap with range shifter). / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

The aim of this research project is to investigate, experimentally and analytically, the effects of reinforcement corrosion on the flexural, shear and blast behaviours of reinforced concrete beams. As part of the experimental study, twenty-four beams reinforced were tested under quasi-static and simulated blast loads using the University of Ottawa Shock tube. All beams had dimensions of 125 mm x 250 mm x 2400 mm and were tested under four-point bending. Tension reinforcement consisted of either 2 – 10M (ρ= 1%) or 2 – 15M bars (ρ= 1.6%) for the flexure dominant specimens, and 2 – 25 M bars (ρ= 4%) for the shear-dominant specimens. In all cases, transverse reinforcement consisted of 6 mm stirrups spaced at s = 100 mm (d/2) throughout the beam span. Eighteen of the specimens were subjected to an accelerated corrosion process to induce different amount of mass loss in the longitudinal and transverse steel reinforcement. The test variables included: the type of corrosion (i.e. on the longitudinal or transverse reinforcement), the amount of corrosion (i.e. % mass loss in the steel reinforcement) and the extent / location of corrosion on the tension steel reinforcement (i.e. over the full length, middle span or end spans). The results from the experimental tests showed that corrosion of the tension and transverse steel reinforcement decreased the strength and ductility of the reinforced concrete beams under static loading, ultimately changing the failure mode. Similarly, the results from the blast tests showed that corrosion of the longitudinal and transverse reinforcement affected maximum displacements and support rotations, reduced blast capacity, increased damage and fragmentation, and ultimately changed the failure process from ductile to brittle. Results under both static and blast loads were sensitive to the amount and extent/location of the corrosion. As part of the analytical study, the static results were predicted using 2D finite nonlinear element (FE) modelling. The effects of corrosion were considered using several modeling features including: reduction in steel bar cross-sectional area, modification of the steel stress-strain response, and introducing corrosion-induced cracking using applied pre-strains. The predicted results from the FE simulations were to provide acceptable predictions in terms of load capacity and failure mode when compared to the experimental static test results. The blast results were predicted using two approaches, including: 1) single-degree of freedom (SDOF) analysis (with the resistance functions developed using FE modelling); and 2) the blast analysis capabilities of FE software VecTor2. Overall both approaches led to acceptable predictions of maximum mid-span displacements when compared to the experiments.

The intersection of decreasing resource size and increasing population and its associated demand creates a pressing need to develop products that act as alternatives to solid sawn lumber. Engineered composite lumber is one such alternative. The product described herein utilizes a modified form of sawn lumber as the raw material. The objective of this research was to manufacture, mechanically test, and evaluate a novel type of engineered lumber. Non destructive evaluation of raw materials and finished beams, and final mechanical testing to determine mean strength and stiffness values as per ASTM 5456 were used. The mechanical property data was converted into design values for fiber stress in bending (Fb) and stiffness (MOE). These design values was compared to those published by the U.S. (NDS) for wood construction. Pine logs were reduced into cants and further processed into matched symmetrical trapezoids. Symmetrical trapezoids were then non-destructively evaluated via E-computer and Director, and sorted by results. Next, the sorted trapezoids were matched into pairs and assembled into bowtie beams. Polyvinyl acetate adhesive was used throughout. Stiffness of the manufactured beams was nondestructively evaluated too. Then the beams were mechanically tested. The information from the E-computer was correlated to the strength and stiffness for each beam. The design strength and stiffness was compared to the values of sections of equivalent depth and maximum width as shown in the NDS. Also, non destructive test values were compared and correlated to those from the destructive tests. Finally, the design strength and stiffness values were respectively multiplied by the sectional area or the moment of inertia. This produced a strength efficiency factor and a stiffness efficiency factor. These factors were compared to factors derived from multiplying the design strength or design stiffness values (from the NDS) times the area or the moment of inertia of a rectangular section of equivalent depth and maximum width. It is found that the mechanically efficient bowtie section produced an increased strength and stiffness efficiency as compared to that of solid sawn material.

No description available.

No description available.