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1
Curry, Richard. "Response of plates subjected to air-blast and buried explosions". Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26877.
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Explosive threats have become more prevalent in both military and terrorist theatres of conflict, showing up largely in the form of Improvised Explosive Devices (IED) which are often buried in soil to conceal them and increase their effectiveness. The response of a structure subjected to a blast load is influenced by many factors, namely stand off distance, mass of explosive, degrees of confinement and medium surrounding the charge. This study focuses on characterizing the transient deformation of test plates which have been exposed to different explosive loading conditions including free air blasts (AIR), backed charge (VBP) and buried charge (SBP) configurations. In the three loading configurations, four charge masses are considered, utilizing 10g, 15g, 20g and 25g masses of PE4 plastic explosive which were moulded into cylindrical charges of a constant 38mm diameter. The transient deformation of the test plates was captured using high speed Digital Image Correlation (DIC), which utilized two high speed cameras to record the experiments. Extensive modifications to the blast pendulum to incorporate the cameras was necessary to adapt this technique in a different method to that used in previous literature. The mounting method proposed allowed the cameras to record the experiment while capturing the impulse imparted on a test plate using a blast pendulum. The experimental plates exhibited only Mode I failure, which is plastic deformation, enabling the effect of different loading configurations on the transient and final plate deformation profiles to be identified. Numerical simulations of the experiments were developed to further the understanding of the load arising from the three configurations and the deformation mechanisms involved. The experimental results are used to validate the numerical models, which allow for a better understanding of the evolution of the deformation and strains across the plate. The transient data for the numerical simulation and the experiments were found to match closely. This work clearly shows the effect that the different loading conditions have on the tests plates, specifically the impulse distributions and transient strain in the plates. It was observed in this study that the impulse imparted on a test plate increases with the addition of sand while keeping other test conditions constant. The impulse recorded was observed to increase by 490-540% and 19-100% when compared to AIR and VBP 50mm SOD tests respectively. The loading profile acting on the test plate as a result of the specific impulse changes significantly with the inclusion of sand. The midpoint deflection increases with a decrease in stand off distance, increase in charge mass, increase in level of confinement or the inclusion of an overburden of sand. The observed increase in midpoint deflection of between 90-160% and 30-40% when compared to AIR and VBP 50mm SOD tests respectively was reported. The transient plate profile does not match the final deformation profile.
2
Chock, Jeffrey Mun Kong. "Review of Methods for Calculating Pressure Profiles of Explosive Air Blast and its Sample Application". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/32066.
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Blast profiles and two primary methods of determining them were reviewed for use in the creation of a computer program for calculating blast pressures which serves as a design tool to aid engineers or analysts in the study of structures subjected to explosive air blast. These methods were integrated into a computer program, BLAST.F, to generate air blast pressure profiles by one of these two differing methods. These two methods were compared after the creation of the program and can conservatively model the effects of spherical air blast and hemispherical surface burst.
The code, BLAST.F, was used in conjunction with a commercial finite element code (NASTRAN) in a demonstration of method on a 30 by 30 inch aluminum 2519 quarter plate of fixed boundary conditions in hemispherical ground burst and showed good convergence with 256 elements for deflection and good agreement in equivalent stresses of a point near the blast between the 256 and 1024 element examples. Application of blasts to a hypothetical wing comprised of aluminum 7075-T6 was also conducted showing good versatility of method for using this program with other finite element models.
Master of Science
3
Magnusson, Johan. "Structural concrete elements subjected to air blast loading". Licentiate thesis, Stockholm : Byggvetenskap, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4441.
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4
Ismail, Mohamed Mohamed. "Blast wave parameter studies of fuel-air explosives". Thesis, Cranfield University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316143.
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5
Avasarala, Srikanti Rupa. "Blast overpressure relief using air vacated buffer medium". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54211.
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Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 85-88).
Blast waves generated by intense explosions cause damage to structures and human injury. In this thesis, a strategy is investigated for relief of blast overpressure resulting from explosions in air. The strategy is based on incorporating a layer of low pressure-low density air in between the blast wave and the target structure. Simulations of blast waves interacting with this air-vacated layer prior to arrival at a fixed wall are conducted using a Computational Fluid Dynamics (CFD) framework. Pressure histories on the wall are recorded from the simulations and used to investigate the potential benefits of vacated air layers in mitigating blast metrics such as peak reflected pressure from the wall and maximum transmitted impulse to the wall. It is observed that these metrics can be reduced by a significant amount by introducing the air-vacated buffer especially for incident overpressures of the order of a few atmospheres. This range of overpressures could be fatal to the human body which makes the concept very relevant for mitigation of human blast injuries. We establish a functional dependence of the mitigation metrics on the blast intensity, the buffer pressure and the buffer length. In addition, Riemann solutions are utilized to analyze the wave structure obtained from the blast-buffer interactions for the interaction of a uniform wave an air-depleted buffer. Exact analytical expressions are obtained for the mitigation obtained in the incident wave momentum in terms of the incident shock pressure and the characteristics of the depleted buffer. The results obtained are verified through numerical simulations.
(cont.) It is found that the numerical results are in excellent agreement with the theory. The work presented could help in the design of effective blast protective materials and systems, for example in the construction of air-vacated sandwich panels. Keywords: Blast Mitigation, Air-depleted Buffer, Low Pressure, Blast Waves, Sandwich Plates, Numerical Simulations
by Srikanti Rupa Avasarala.
S.M.
6
Fox, Matthew J. "Numerical modeling of air blast effects on hybrid structures". Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2630.
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Thesis (M.S.)--West Virginia University, 2002.Title from document title page. Document formatted into pages; contains x, 114 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 42-45).
7
Bigikocin, Onur. "Presplit Blast Induced Air Overpressure Investigation At Usak Kisladag Gold Mine". Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608741/index.pdf.
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In presplit blasting operations airborne energy called air blast overpressure or
impulsive sound is produced. The air blast induced by blasting may vary
significantly at or around an open pit mine depending on several parameters such as
the amount of charge detonated, the physical distance between the blast and the
monitoring locations and the weather conditions. Therefore evaluation and
assessment of noise condition at or around an open pit mine is necessary.
The objective of this research study is to monitor and record the noise and to
investigate and assess the noise conditions that will be induced from presplit
blasting operations at Kisladag Gold Mine. In this research study, several
parameters such as the amount of charge, the physical distance to the location of
monitoring device or residential structures and the weather condition parameters
such as wind direction, wind speed were recorded, analyzed and evaluated.
It is observed that with increasing charge per delay air overpressure increases,
whereas with increasing scaled distances it decreases. It is also understood that
wind speed and the direction are effective in air overpressure propagation also, but
this subject needs further investigation. It is concluded that according to the U.S.
regulations there is no damage risk to the structures and no disturbance to the
inhabitants at present. Due to the uncertainties in weather conditions, in order not to
take any risks, the charge amount per delay should be kept at 35 kg or less for
presplit blasting at the mine.
8
Davids, Sean. "The influence of charge geometry on the response of cylinders to internal air blasting". Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20400.
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The effect of charge geometry on the structural response of right circular cylinders, subjected to internal blast loading, was investigated. Thin-walled, seamless 304 stainless steel cylinders were subjected to blast loads from partially confined bare cylindrical PE4 charges with different diameter and aspect ratios(charges length to charge diameter). The diameters of interest were:
25 mm (aspect ratios of 0.5 -3).
30 mm (aspect ratios of 0.5 -1.6).
35 mm (aspect ratios of 0.5 - 1.1).
40 mm (aspect ratios of 0.5 - 0.9).
The effect of aspect ratio, for the constant diameter or constant mass cases, on the structural response of the cylinders (that is, diametric deflection, axial impulse, and axial shortening) is reported. Cylindrical charges with an aspect ratio of 1, were compared to spherical charges of equivalent mass. For charges with constant diameter with varying length: The diametric deflection increased with increasing aspect ratio. The axial shortening increased with increasing aspect ratio. The axial impulse increased with increasing aspect ratio. For charges with constant mass with varying diameter and length: The long charges (that is, charges with aspect ratios greater than 1) caused larger diametric deflections than their mass equivalent short (that is, charges with aspect ratios less than 1) charges. This is because the long charges had more side effective charge mass (that is, the mass of the charge that contributes directly to the diametric deflection of a cylinder) than the shorter charges. The short charges transferred more axial impulse to the ballistic pendulum, because they had more axial effective charge mass (that is, the mass of the charge that contributes directly to the axial impulse that is transferred to a ballistic pendulum) than their mass equivalent long charges. It was observed that a lighter charge can diametrically deflect a cylinder more effectively than a heavier charge, if its side effective charge mass is greater than that of the heavier charge. The structural responses of the cylinders obtained from cylindrical charge detonations were greater than those obtained from the mass equivalent spherical charge detonations. The deflections resulting from the cylindrical charges were also more localised compared to the spherical charges.
9
Ahmed, Tushar. "Atomization and Combustion of Hybrid Electrohydrodynamic-Air-Assisted Sprays". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28180.
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This thesis presents an extensive study of the atomization and combustion of dielectric liquids using a hybrid air-blast electrostatic atomizer. While airblast atomization relies on the shear stresses generated at the liquid-air interface, electrostatic atomization introduces an electric charge into the bulk liquid, and the resulted Coulombic repulsive force facilitates the fragmentation process. The atomizer introduced in this contribution is specifically designed to operate in either a single (air-blast or electrostatic) or hybrid mode to enable the delivery of a charged and/or air-assisted spray for combustion applications. The aim is to understand the effect of adding electric charge to a liquid jet which is subject to break up in a co-flowing air stream. In addition to analysis of atomization processes, the influence of charge on flame structure is also analyzed. Laser diagnostics are utilized for measurements and the results obtained for the atomizer in hybrid mode (air-blast + electrostatic) are compared with the pure air-blast mode.
Firstly, a high-speed microscopic shadowgraphy technique is implemented to examine near-field spray structure. Diesel is used as a dielectric liquid to create various sprays that cover a range of non-dimensional numbers. The effect of charge on liquid jet unsteadiness and on the probability distribution of wavelength and amplitude of instabilities is discussed. The influence of charge on droplet and ligament size and their population is also analyzed. The findings show that the application of charge makes the liquid jet more unstable and the instabilities forming on the liquid core exhibit a shift to a shorter wavelength with a broadening in the probability distribution of wave amplitude. In addition, a droplet and ligament size reduction along with an increase in droplet count is observed with the addition of charge.
The thesis then progresses to discussing results from reacting sprays stabilized on a pilot where kerosene is chosen as the liquid. A premixed pilot flame is used to provide a steady heat source for stabilizing the hybrid atomized sprays. Flame stability characteristics, in terms of blow-off velocity, are presented as a function of controlling parameters, without and with charge. Downstream droplet statistics and flow field for both non-reacting and reacting sprays are shown using laser Doppler velocimetry/phase Doppler anemometry (LDV/PDA) revealing key features in the droplet fields from this burner. Due to relatively low spray specific charge for the aerodynamic Weber numbers investigated, the droplet size and velocity remained largely unaffected through the addition of charge, however, a rise in particle concentration at the center of the spray was noted.
Finally, high-speed hydroxyl planar laser induced fluorescence (OH-PLIF) is used to locate reaction zones and comment on the morphology of the reaction zone structures. In a hybrid mode, the charge was seen to push reaction zones radially outward and assisted in stabilizing the flame by keeping OH islands more connected when compared to a pure air-blast mode. This observation was also consistent with a slight improvement in flame stability with the addition of charge.
10
Deng, Tian. "LES combined with statistical models of spray formation closely to air-blast atomizer". Thesis, Ecully, Ecole centrale de Lyon, 2011. http://www.theses.fr/2011ECDL0037/document.
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Cette thèse présente une extension de l'approche stochastique de l'atomisation primaire de type air assisté près d'un injecteur. Cette approche avait déjà été introduite dans les publications de Gorokhovski et al. Dans le cadre de la simulation des grandes échelles, la zone d'atomisation primaire est simulée comme un corps immergé avec une structure stochastique. Ce dernier est défini par la simulation stochastique de la position et de la courbure de l'interface entre le liquide et le gaz. La simulation de la position de l'interface est basée sur l'hypothèse de symétrie d'échelle pour la fragmentation. La normale extérieure à l'interface est modélisée en supposant une relaxation statistique vers l'isotropie. Les statistiques de la force du corps immergé servent de conditions aux limites pour le champ de vitesse issu de la LES ainsi que pour la production des gouttes de l'atomisation primaire. Celles-ci sont ensuite transportées par une approche lagrangienne. Les collisions entre les gouttes dans la zone d'atomisation primaire sont prises en compte par analogie avec l'approche standard de la théorie cinétique des gaz. Une fermeture est proposée pour la température statistique des gouttelettes. Cette approche est validée par des comparaisons avec les mesures expérimentales de la thèse de Hong. Les résultats numériques pour la vitesse et de la taille des gouttes dans le spray à différentes distances du centre du jet et de l'orifice de la buse sont relativement proches des résultats expérimentaux. Différentes conditions d'entrée pour la vitesse sont testées et comparées aux résultats expérimentaux. Par ailleurs, le rôle spécifique de la zone de recirculation devant le dard liquide est soulignée par le battement du dard liquide et la production de gouttelettesThis thesis introduced an extension to stochastic approach for simulation of air-blast atomization closely to injector. This approach was previously proposed in publications of Gorokhovski with his PHD students. Our extension of this approach is as follows. In the framework of LES approach, the contribution of primary atomization zone is simulated as an immersed solid body with stochastic structure. The last one is defined by stochastic simulation of position-and-curvature of interface between the liquid and the gas. As it was done previously in this approach, the simulation of the interface position was based on statistical universalities of fragmentation under scaling symmetry. Additionally to this, we simulate the outwards normal to the interface, assuming its stochastic relaxation to isotropy along with propagation of spray in the down-stream direction. In this approach, the statistics of immersed body force plays role of boundary condition for LES velocity field, as well as for production of primary blobs, which are then tracked in the Lagrangian way. In this thesis, the inter-particle collisions in the primary atomisation zone are accounted also by analogy with standard kinetic approach for the ideal gas. The closure is proposed for the statistical temperature of droplets. The approach was assessed by comparison with measurements of Hong in his PHD. The results of computation showed that predicted statistics of the velocity and of the size in the spray at different distances from the center plane, at different distances from the nozzle orifice, at different inlet conditions (different gas velocity at constant gas-to-liquid momentum ratio, different gas-to-liquid momentum ratio) are relatively close to measurements. Besides, the specific role of recirculation zone in front of the liquid core was emphasized in the flapping of the liquid core and in the droplets production
11
Gardner, Kevin Alexander. "Experimental Study of Air Blast and Water Shock Loading on Automotive Body Panels". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1468938824.
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Emmanuelli, Gustavo. "An Assessment of State Equations of Air for Modeling a Blast Load Simulator". Thesis, Mississippi State University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10979719.
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When an explosive detonates above ground, air is principally the only material involved in the transmission of shock waves that can result in damage. Hydrodynamic codes that simulate these explosions use equations of state (EOSs) for modeling the behavior of air at these high-pressure, high-velocity conditions. An investigation is made into the effect that the EOS selection for air has on the calculated overpressure-time waveforms of a blast event. Specifically, the ideal gas, Doan-Nickel, and SESAME EOSs in the SHAMRC code were used to reproduce experiments conducted at the Blast Load Simulator (BLS), a large-scale shock tube operated by the U.S. Army Engineer Research and Development Center, that consisted of subjecting an instrumented rigid box at three angles of orientation inside the BLS to a blast environment. Numerical comparisons were made against experimentally-derived confidence intervals using peak values and several error metrics, and an attempt was made to rank the EOS based on performance. Issues were noted with the duration of decay from maximum pressure to negative phase that resulted in a general underprediction of the integrated impulse regardless of EOS, while the largest errors were noted for gages on faces at 45 to 90 degrees from the initial flow direction. Although no significant differences were noticed in the pressure histories from different EOSs, the ideal gas consistently ranked last in terms of the error metrics considered and simultaneously required the least computing resources. Similarly, the Doan-Nickel EOS slightly performed better than SESAME while requiring additional wallclock time. The study showed that the Doan-Nickel and SESAME EOSs can produce blast signatures with less errors and more matches in peak pressure and impulse than the ideal gas EOS at the expense of more computational requirements.
13
Hadjiyiannis, Constantinos. "Investigation of break-up process of liquids and downstream spray characteristics in air-blast atomisers". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/23215.
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The research of this thesis focuses on the study of sprays produced by twin fluid air-blast atomisers and the main objective is to study the liquid jet break-up mechanism and relate it to the downstream spray characteristics. Two different air-blast atomiser geometries are used; coaxial, where the liquid co-flows with the gas stream, and the liquid jet in a gaseous cross-flow. The thesis describes advanced and novel measurements to reveal the temporal and spatial development of the liquid flow and its interaction with the surrounding gas stream. Initially, the break-up process is studied by measuring the characteristics of the continuous liquid jet. Techniques such as electrical conductivity, high-speed shadowgraphy and optical connectivity were used to characterise the atomisation process. The latter is a novel laser-based technique used to illuminate internally the continuous liquid column by introducing a laser beam within the liquid nozzle, while a fluorescent dye in the liquid ensures that the whole volume of the liquid is visualised. The laser light propagates downstream while reflecting on the gas-liquid interface to be interrupted at the break-up position, where the light is scattered and diffuses widely. In the case of a jet in a cross-flow gas stream the fluorescent intensity images were recorded from two different angles to reveal the various features involved in the liquid jet structure. The study of the spatial and temporal characteristics of the instabilities and the developed surface waves on the liquid column can provide information on jet morphology and a better understanding of the physics that elicit the break-up phenomenon. For that purpose, Proper Orthogonal Decomposition (POD) is applied to reveal the various flow scales and elucidate the mechanism of transfer of momentum from the gas to the liquid flow. The most energetic modes are used to describe the jet interface dynamics that may well define the formation of the downstream droplet sizes. Interferometric Laser Imaging for Droplet Sizing (ILIDS) was also used for planar measurements of droplet sizes and velocities. ILIDS images the scattered light from droplets in an out-of-focus mode at different streamwise distances from the nozzle exit to obtain interference fringe patterns associated with each droplet. The spacing of each fringe pattern is proportional to the corresponding droplet diameter. Instantaneous droplet clustering is measured along with the primary atomisation process and the liquid jet break-up characteristics are correlated with the downstream droplet sizes. Several time delays are used between optical connectivity and ILIDS measurements to capture the various classes of droplet sizes that travel with different velocities from the break-up region to the downstream spray location. The small droplets travel faster and move with a velocity similar to the gas flow, in contrast to the larger droplets, which are conveyed to the size measuring region with a lower velocity and, therefore, higher time delays. A conditional correlation method was developed to reduce statistical uncertainties. Negative correlations were found between the break-up length of the liquid jet and downstream number of droplets, indicating that they are inversely proportional. The relation between the break-up length and droplet Arithmetic and Sauter Mean Diameters seems to be more complex since a sinusoidal relation was extracted. The estimated correlation coefficients varied with time delay and a repeatable trend was observed which exposed the coherent behaviour of the break-up process and its frequency, revealing that it is not a random phenomenon, but rather a multifaceted mechanism governed by physical laws.
14
La, Flèche Maxime. "Dynamics of Blast Wave and Cellular H2-Air Flame Interaction in a Hele-Shaw Cell". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38178.
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The present thesis investigates the interaction of a shock wave with a cellular flame and the ensuing mechanisms on the dynamics of the subsequent flame deformation. The inter- action is known to disrupt the flame surface through the Richtmyer-Meshkov instability, hence potentially enhancing the local combustion rates. This study aims to clarify the evolution of a flame when perturbed head-on by a shock wave. Two novel series of experiments were conducted in a vertically-oriented Hele-Shaw cell, which could successfully isolate a quasi-bidimensional cellular flame structure at ambient conditions. In the first configuration, the passage of the shock wave arising in the burned products of a deflagration wave was investigated, while both waves propagated in the same outward direction. In the other configuration, the shock wave centrally emerged in the unburned gases and collided with a cellular flame front traveling in the opposite direction. The event was captured using a Z-type Schlieren imaging system to visualize the growth of the flame cells.
Shock characterization was determined in the Hele-Shaw apparatus to estimate the strength of the blast wave generated by energy deposition using a high-voltage igniter or by decoupled detonation from a detonation tube. A combustion study was also performed to determine the laminar flame speed in a mixture of hydrogen-air according to different equivalence ratios in the apparatus. The experiments revealed that inherent cellular flame instabilities are well developed in the observation scale of the Hele-Shaw geometry. The shock-flame complex was therefore analyzed experimentally for selected mixtures. As the shock wave traversed the interface separating the burned and unburned gases, the flame became more corrugated. Following the interaction, the flame cusps were stretched and/or flattened. At later times, the wrinkled interface was reversed and developed finer scales. A time scale analysis was performed to identify the contribution of the competing effects of Richtmyer-Meshkov and Rayleigh-Taylor instabilities on the flame interface deformation. For the case of a shock wave traversing the flame interface from the unburned to the burned side, the early perturbations were mainly governed by the Richtmyer-Meshkov instability. Finally, Rayleigh-Taylor instability resulted from the decaying pressure profile of the blast wave and tended to stabilize the perturbed interface to eventually reverse the cellular structure. Experimental and inert numerical results on the flame cell’s amplitude growth were found to be in good agreement.
15
ABU-NABAH, BASSAM ABDEL-JABER. "SWIRL ORIENTATION EFFECT ON THE INSTABILITY AND THE BREAKUP OF ANNULAR LIQUID SHEETS". University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1060978117.
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McBride, David Iain. "Air blast circuit breaker impulse noise : the role of audiometry in risk assessment of industrial noise". Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393839.
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Amirrasouli, Benyamin. "Mechanical properties of low density fibre-reinforced cellular concrete and its energy absorption potential against air blast". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-properties-of-low-density-fibrereinforced-cellular-concrete-and-its-energy-absorption-potential-against-air-blast(a8457a33-c479-4db9-adbc-579599783bc9).html.
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The scope of this study is to establish extensive material tests to determine the mechanical properties of cellular concrete and evaluate its potential as energy absorption material against air blast load. This study includes a literature review of existing studies on cellular concrete, proportioning, and its mechanical properties, together with studies on the properties and application of other foams such as aluminium and polymer foams. It is concluded that, unlike other foam materials, there is a lack of systematic studies on the mechanical properties of cellular concrete especially for densities less than 1000 kg/m3. The survey also reviewed the existence of materials being used as a sacrificial layer against air blast load, together with the analytical models proposed to determine the parameters required to design a cladding system. As a result it was found that cellular concrete can maintain most of the properties of the cladding materials and can be applied as a new sacrificial layer against the blast load. Extensive material tests are carried out to characterise the effect of ingredients and density on material properties of cellular concrete. Based on the experimental results, an empirical model is proposed which determines the plateau and densification regime of nominal stress-strain curve of the cellular concrete with different densities. The penetration resistance of cellular concrete with different densities under truncated, conical, flat and hemi-spherical solid indenters are studied experimental. By determining the deformation mechanism of cellular concrete under indentation with application of an X-Ray tomography image system, an analytical model is proposed to determine the resistance of cellular concrete under penetration of flat indenter. Experimental closed range blast tests are performed with 1kg and 3kg C4 explosive to determine the mitigation potential of cellular concrete against air blast load. Numerical modelling of the experimental blast test is carried out using Ansys LS-DYNA to evaluate the feasibility of the numerical modelling techniques to predict the response of cellular concrete against air blast load.
18
Ruiz, Josue O. "Manufacturing and Instrumentation of an Open End Compressed Air Shock Tube". DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1843.
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Shock tubes have been used extensively to study shock wave structures and high speed flow features. The purpose of constructing this open end shock tube was to have the ability to produce shock waves in a laboratory setting but also understand the exit flow coming out which can be applied to future studies that are beyond the scope of this work. This undertaking would require that an open end shock tube be built and instrumented with PCB Integrated Circuit Piezoelectric (ICP) Pressure Sensor Model 113B24 that would then be connected to a PCB Model 482C05 Signal Conditioner with the purpose of measuring the the pressure jumps as well as the speed of the shock wave. The data was acquired using National Instruments NI PXIe-1071 chassis with a PXI 1088 Embedded Controller as well as three PXI 5114 digitizer cards with the Virtual Instrument coded using LabView. The data was written to a text file that was then transferred to MATLAB for post processing using a Savitzy-Golay filter to clean up the signal noise. The shock tube was driven using compressed air and a diaphragm burst was achieved through spontaneous rupture of a 0.003" Mylar diaphragm. The open shock tube built for this undertaking fits in a lab space and successfully produces a shock wave that propagates down the tube that exits at the open end to reproduce a blast wave. Additionally the available pressure sensors and DAQ were integrated into the shock tube to measure the different predicted shock structures in each run. The experimental runs at the exit of the shock tube demonstrate the expected exit flow features, but a flow visualization is necessary to get a better understanding of the exit flow
19
Yokomizu, Yasunobu, Toshiro Matsumura, Akiji Matsuda i Hideyuki Ohno. "Dependence of arc interrupting capability on spatial distribution of airflow velocity in air-blast flat-type quenching chamber". IEEE, 2003. http://hdl.handle.net/2237/6793.
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Silveira, Carina Folgearini. "Extensão, gravidade e fatores associados à hipersensibilidade dentinária : estudo transversal". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/152690.
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A hipersensibilidade dentinária (HD) é descrita na literatura como uma dor aguda, de curta duração, provocada por estímulos térmico, tátil, osmótico, químico ou evaporativo em região de exposição dentinária, não sendo atribuída à dor causada pela presença de defeito ou doença de origem dentária. Esse tipo de acometimento tem sido cada vez mais reportado pelos pacientes, em vista disso, o objetivo desse estudo foi avaliar a extensão e gravidade de HD, bem como sua associação com indicadores periodontais [índice de placa (IP), índice gengival (IG) e recessão gengival (RG)] em uma amostra composta por 132 indivíduos com HD diagnosticada por meio de estímulo térmico/evaporativo (jato de ar) associada à escala Schiff. Análises descritivas foram feitas e as porcentagens médias de IP e IG foram estimadas considerando 6 sítios por dente e também 3 sítios das faces vestibulares. Além disso, os dados foram analisados através de modelos uni e multivariados utilizando análises de regressão linear. A média de idade foi de 30.66±10.33, sendo o sexo feminino mais afetado pela HD (83.3%). Foi possível observar que a HD esteve associada à recessão gengival. A prevalência de dentes com recessão gengival foi de 17.17%, enquanto que a prevalência de recessão em dentes com HD foi de 77.1% e a média de recessão vestibular foi de 1.58±0.87. Quando considerada a média de dentes com 1 ou mais milímetros de recessão, observou-se que, em média, 4.48 dos dentes apresentaram esta condição. Um maior número médio de dentes com recessão e menores escores médios de IP nos sítios vestibulares apresentaram-se signicativamente associados ao número médio de dentes com HD. A gravidade da HD nos pacientes foi significativamente influenciada por maior média de recessão gengival e foi maior nos pacientes do sexo feminino. Dentes que possuíam maiores médias de recessão e maiores escores médios de IP e menores de IG nos sítios vestibulares apresentaram maiores valores na escala Schiff (p<0.05). Frente aos achados, é possível observar que portadores de HD têm um grande número de dentes afetados por esta condição e que estes apresentam recessão. Além disto, nos dentes que apresentam HD, a gravidade desta está associada a presença de mais placa e melhor condição gengival, além da extensão da recessão.Dentin hypersensitivity (DH) is described in the literature as an acute short-term pain caused by thermal, tactile, osmotic, chemical or evaporative stimuli in the region of dentin exposure and not attributed to pain caused by the presence of defect or disease of dental origin. Therefore, the aim of this study was to evaluate the extent and severity of DH, as well as its correlation with periodontal indicators [plaque index (PI), gingival index (GI) and gingival recession (GR)] in 132 individuals with DH diagnosed by thermal/evaporative (air blast) stimulation associated with the Schiff scale. Descriptive analyzes were made and the mean percentages of PI and GI were estimated considering 6 sites per tooth and also 3 buccal sites. In addition, the data were analyzed using univariate and multivariate models using linear regression analysis. The mean age was 30.66 ± 10.33, female sex being more affected by DH (83.3%). It was possible to observe that DH was associated to gingival recession. The prevalence of teeth with gingival recession was 17.17%, while the prevalence of recession in teeth with DH was 77.1%. The mean of vestibular recession was 1.58 ± 0.87, and when considered the mean teeth with 1 or more millimeters recession, it was observed that, a mean of 4.48 teeth presented this condition. A higher mean number of teeth with recession and lower mean PI scores in the vestibular sites were associated (p<0.001) with the mean number of teeth with DH. The severity of DH in number of patients was significantly influenced by the higher mean of gingival recession and was higher in the female patients. Teeth that had higher recession mean and higher mean PI scores at the buccal sites, but lower GI scores at this sites, presented significantly higher values on the Schiff scale (p <0.05). In view of the findings, it is possible to observe that DH patients have a large number of teeth affected by this condition and that these present gingival recession. In addition, in the teeth that present DH, the severity is associated with the presence of more plaque and better gingival condition, in addition to the extent of the recession.
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Venter, Sarel Jacobus, i D. G. Kroger. "The effectiveness of axial flow fans in a-frame plenums". Thesis, Stellenbosch : University of Stellenbosch, 1990. http://hdl.handle.net/10019.1/15625.
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Thesis (PhD (Mechanical and Mechatronic Engineering)--University of Stellenbosch, 1990.260 leaves printed single pages, preliminary pages i-xxi and numbered pages Chapter 1/1.1-1.3, Chapter 2/2.1-2.17, Chapter 3/3.1.1-3.10, Chapter 4/4.1-4.18, Chapter 5/5.1-5.3, References pages R.1-R.7, Appendix A pages A.1-A.34, Appendix B pages B.1-B.34, Appendix C pages C.1-C.26, Appendix D pages D.1-D.16, Appendix E pages E.1-E.30, Appendix F pages F.1-F.39. Includes bibliography, list of tables, figures and symbols.
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ENGLISH ABSTRACT: The ultimate goal of this project is to ensure a better understanding of the governing mechanisms present when flow distorting components are installed in close proximity of an axial flow fan. The effect of different parameters on the operation of axial flow fans is investigated. These parameters are divided into flow enhancing and flow reduction effects. The performance of an axial flow fan can be enhanced by changing the tip clearance, by adding a solid disc to the hub of the fan or by varying the number of fan blades. Flow reductions are caused by components such as inlet grids, walkways and their supporting structures, heat exchangers and windwalls. The effects of flow enhancing components are measured and compared to the results of other authors. The sensitivity of these effects to parameters such as the type of fan rotor and the specific system in which the rotor is installed is highlighted. The system effect (the interaction between the fan rotor and flow resistances in close proximity of each other) of individual components, as well as the combination of different components, is predicted both theoretically and experimentally. These predictions are compared to measured data relevant to the components in an installation where the system effects are present. The results are correlated to the kinetic energy flux coefficient of the flow at different locations within the installation. Experimental data obtained from a full scale unit (inlet shroud diameter of 9,216 m) are used to compare to scaled data from the model (inlet shroud diameter of 1,542 m). The hub to tip ratio of the axial flow fans investigated is 0,15. The most important conclusions are that the performance of the type of axial flow fan under investigation can be improved by reducing its tip clearance and by installing a solid disc to the downstream side of the rotor. An increase in the number of blades of the fan leads to only marginal improvements in the fan performance. The overall performance of the system can also be improved by removing some of the flow resisting components, or by changing their relative positions. All these conclusions are based on the assumption that the power input to the fan rotor remains constant.
AFRIKAANSE OPSOMMING: Die uiteindelike doel van hierdie projek is om te verseker dat die beherende meganismes wat teenwoordig is wanneer vloeiversteurende komponente in die nabyheid van 'n aksiaalwaaier geinstalleer word, beter verstaan word. Die effek van verskillende parameters op die werkverrigting van aksiaalwaaiers word ondersoek. Hierdie parameters word verdeel in vloeiverbeterings- en vloeiverminderingseffekte. Die werkverrigting van 'n aksiaalwaaier kan verbeter word deur die lempuntspeling te verstel, deur 'n soliede skyf aan die naaf van die waaierrotor te installeer, of deur die aantal lemme te verander. Die vloeiverminderings word veroorsaak deur inlaatsiwwe, loopvlakke en hul ondersteuningsstrukture, warmteruilers en windwande. Die effekte van vloeiverbeteringskomponente word gemeet en vergelyk met die resultate van ander outeurs. Die sensitiwiteit van hierdie effekte op parameters soos die tipe rotor en die spesifieke stelsel waarin die rotor geinstalleer is, word uitgelig. Die stelseleffek (die interaksie tussen die rotor van die waaier en vloei weerstande wat naby mekaar geinstalleer is) van individuele, sowel as 'n kombinasie van verskillende komponente, word teoreties en eksperimenteel voorspel. Hierdie voorspellings word dan vergelyk met eksperimentele data wat van toepassing is op die komponente in 'n installasie waar stelseleffekte voorkom. Die resultate word gekoppel aan die kinetiese energievloedkoeffisient van die vloei by verskillende posisies binne die installasie. Eksperimentele data, verkry vanaf 'n volskaaleenheid (inlaatmondstukdiameter van 9,216 m), word met die geskaleerde data van die model (inlaatmondstukdiameter van 1,542 m) vcrgelyk. Die naaf- tot hulsverhouding van die aksiaalwaaiers wat ondersoek word is 0,15. Die belangrikste gevolgtrekkings is dat die werkverrigting van die tipe aksiaalwaaier wat ondersoek word verbeter kan word deur die lempuntspeling te verminder en deur 'n soliede skyf te installeer by die stroomaf kant van die rotor. 'n Toename in die aantal lemme van die waaier lei slegs tot marginale verbeterings in die werkverrigting van die waaier. Die totale werkverrigting van die stesel kan ook verbeter word deur sommige vloeiweerstandskomponente te verwyder, of deur hulle relatiewe posisies te verander. Al hierdie gevolgtrekkings is gebasseer op die aanname dat die drywingsinset na die waaierrotor konstant bly.
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Pawlowicz, Jakub. "Evaluation of air entraining behaviour in concrete using computer aided methods on hardened samples". Thesis, KTH, Betongbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264752.
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Increasing awareness of sustainability in the concrete industry forces structural design and executionto focus on avoiding costly and unpredictable maintenance action, instead paying higher attention todamage prevention by direct actions on early stages of production. One of such approaches, whichdeals with the problem of freezing and thawing deterioration, is intentional air bubble introductionto the concrete mix. However, the mechanism of air entrainment in concrete can be negativelyaffected on different stages of production by many factors including cement type, admixture dosage,casting conditions or mixing procedure. Therefore, reliable tools for the end-product evaluationought to be considered. The experimental study, presented in this work, focuses on understandingthe blast furnace slag (BFS) influence as well as admixtures’ dosage effect on pore structure ofhardened concrete. Three types of cement were evaluated, including ordinary portland cement(OPC) and two types of CEM III cements with different BFS percentage. The optimal amountsof air entraining agent (AEA) and super plasticizer (SP) were chosen and later reduced in orderto evaluate their impact on total air content, spacing factor and specific surface of the air voids.The main method chosen for this evaluation was the use of an office flat-bed scanner to acquireimages and application of BubbleCounter software for the analysis of the air void structure. Thisapproach is based on linear traverse method and requires special surface treatment for contrastenhancement. Specimens for the analysis were cut from hardened concrete cubes and polishedto achieve a flat surface. The samples were later treated with black ink and zinc oxide paste toachieve a clear contrast between white voids and black paste/aggregate area. In order to estimatethe accuracy of this method, more conventional tools such as pressurised gauge method and air voidanalyser were applied for comparison. Resulted mixtures showed significant differences in air voidproperties between OPC and BFS containing concrete, with the latter being less affected by AEAdosage reduction. Changes in spacing factor and specific surface were also registered; however,their deterioration did not follow the same pattern as that of total air content. No significantdeviation between the two cements containing BFS was observed. An interesting effect of the usedpolycarboxylate ether SP on the AEA reactivity was registered, showing deterioration of air voidproperties with the decrease of plasticizer amount. Comparison of the results from different air voidanalysis methods, suggested an overall agreement on the measured air void system changes due tochanging the AEA content. However, the BubbleCounter software tended to slightly overestimatethe material’s resistance to freeze and thaw phenomenon, giving the most optimistic values inspacing factor and specific surface of air voids.Betongindustrins ökande medvetenhet om hållbarhet leder till att man inom dimensionering ochutförande fokuserar mot att undvika kostnadskrävande och oförutsedda underhållsåtgärder ochistället lägga större vikt på att förebygga skador i produktionens tidiga skeden. En av dessaåtgärder, som hanterar problemet frostnedbrytning, är en medveten inblandning av luftbubblor ibetongen. Mekanismen för att skapa luftporssystemet kan emellertid bli negativt påverkad underolika skeden av produktionen av många faktorer såsom cementtyp, tillsatsmedelsdos, gjutvillkoroch blandningsordning. Därför behöver man reflektera över pålitliga verktyg för utvärderingenav slutprodukten. Den experimentella studien, som presenteras i detta arbete, fokuserar motförståelse hur slagg och tillsatsmedelsdos påverkar den hårdnade betongens luftporssystem. Tretyper av cement utvärderades, dels ett normalt portlandcement, dels två typer av CEM III-cementmed olika andelar av slagg. Optimala mängder av luftporbildare och flyttillsatsmedel valdesmen reducerades senare för att undersöka deras inverkan på totalt luftinnehåll samt luftporernasavståndsfaktor och specifika yta. Den huvudsakliga metoden som valdes för denna utvärderingvar en flatbäddsscanner (kontorsmodell) för att ta bilder och användningen av en programvaravid namn BubbleCounter för att analysera luftporssystemet. Detta tillvägagångssätt baseras påanalys av tvärgående linjer och kräver en speciell behandling av ytan för att åstadkomma kontraster.Provkroppar för analysen sågades ut ur hårdnade betongkuber och polerades för att erhålla en jämnyta. Provkropparna var senare behandlade med svart bläck och zinkoxidpasta för att åstadkomma entydlig kontrast mellan de vita porerna och den svarta ytan av cementpasta och ballast. För att studeranoggrannheten hos denna metod användes som jämförelse även mer konventionella metoder sommätningar med trycksatta givare och luftporsanalys. De framtagna blandningarna visade signifikantaskillnader i luftporernas egenskaper mellan betong med normalt portlandcement och betong medslaggcement, där den senare påverkades i mindre grad av reduktioner i dosen luftporbildare.Förändringar I avståndsfaktor och specifik yta noterades också men försämringen följde inte sammamönster som den för totala luftinnehållet. Ingen signifikant skillnad mellan de två cementeninnehållande slagg kunde observeras. En intressant inverkan av det använda polykarboxylateterbaseradeflyttillsatsmedlet på luftporbildarens reaktivitet noterades. Den visade en försämringav luftporernas egenskaper vid en reduktion av mängden flyttillsatsmedel. En jämförelse avresultaten från de olika metoderna för luftporsanalys indikerade en övergripande överensstämmelsegällande de uppmätta luftporssystemens förändring p.g.a. förändringar i mängden luftporbildare.Programvaran BubbleCounter tenderade emellertid att något överskatta materialets motstånd motfrostnedbrytning med de mest optimistiska värdena för luftporernas avståndsfaktor och specifikayta.
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Shittu, Kazeem Dolapo. "An investigation of the response of an FPSOV structures to external air blast : a case study of FPSOV operating in the Niger Delta". Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2496.
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Floating production storage and offloading systems, otherwise known as FPSOs in the oil and gas industry, are high risk structures because of their exposure to hazardous and flammable hydrocarbons which they carry and in some situations, because of their vulnerability to terrorist attack especially in their areas of operation. These structures have been widely used for the development of offshore oil and gas fields all over the world, especially in most part of Africa, because of their attractive features such as large work area and storage capacity, relative lower cost of construction and good stability. They are either converted from existing tankers or bulk carriers or purposely built. However the recent wave of terrorism across the Nigerian Niger Delta has necessitated the study for the need for offshore structures especially FPSO to be protected from the activities of terrorist. One of the worst case scenarios that is likely to occur on an FPSO is an attack by terrorist resulting in an above water external air blast on the side plate of a midship section of an FPSO. The resulting damage effects that would be caused by this form of attack can be devastating in terms of loss of revenue to a nation, loss of life, assets and degradation to the local environment. This was tragically demonstrated in the North Sea with the loss of the Piper Alpha Platform mentioned by (lees, 1996), albeit initiated by an accidental internal blast, unrelated to terrorist activities. At present, most design methods on the midshipsection structural members of a merchant vessel are based on working stress design concepts that are safe and suitable for normal pre-commissioning and operating conditions and which emphasize the minimum acceptable requirement for the classification society. However, design under extreme air blast loading especially those typical of terrorist/Militant attack, whose magnitude would be far higher than ordinary operating load, are desirable. In order to make it a major design consideration, this study addressed this issue on minimizing the effects of blast overpressure through the evaluation of the 3 types of T stiffeners and 3 L stiffeners to local structural response of such blast pressure on the side shell of the midshipsection of a typical FPSO code named FPSO Nigeria. The Nigerian Niger Delta accounts for over 95% of Nigerian oil and foreign reserve earning, and has been a source of attack and insurgence by militant of the Niger Delta. The objective of this study is to examine an above water air blast pressure attack to the side plate of a midshipsection of an FPSO code named FPSO Nigeria. This blast pressure is converted to an equivalent amount of TNT explosive typical to that which may be used by the militants of the Nigeria Niger delta or other parts of the world and to v KAZEEM SHITTU-An Investigation Of The Response OF AN FPSOVStructure To External Blast: A Case Study Of FPSOV Operating In The Niger Delta recommend ways by which an FPSO operating in this area could be made more resilient to terrorist attack to a larger extent or at least to minimize terrorist caused damage to the barest minimum by the selection of the best of the 3 types of T and L stiffeners considered. Additionally, blast resistant anti-ballistic material was recommended and a cost benefit analysis carried out in order to justify the need and the importance of using such blast resistance anti-ballistic materials. In order to achieve the aim of the thesis, the study commenced with the investigation of the displacement and stresses of plates and stiffened plates using Abaqus software code and compared the results of displacement and stresses generated from Abaqus with that of classical theory in order to validate the accuracy of the Software code by considering different plate thickness and boundary conditions, frequency extraction analysis were generated for plates and stiffened plates in order to obtain frequencies at which resonance could occur and to prevent such. The results generated from Abaqus software code were found to correlates with those generated from classical theory. Actual FPSO Nigeria stiffened panel were then considered and subjected to non-linear blast analysis under different boundary conditions where effects of mesh refinement were considered in details. The mid ship section of the above water side of the FPSO Nigeria was then subjected to blast pressure attack considering the different type of stiffeners with a view to determine the best stiffener configuration and to determine the rupture strain consequently an anti-ballistic blast resistant material was recommended as an aftermath of Cost Benefit analysis was carried out to validate the need for such anti-ballistic blast resistance material on the above water side of FPSOs operating in the Nigeria Niger Delta and the cost savings to nigerian Government was highlighted vis a vis the loss that would have been incurred by the Government should such attack occurs. The research concentrates mainly on developing an appropriate methodology and an illustrating the behavior of typical ship structures to high rate transient air blast loading effects, rather than undertaking a specific detail design study as such. Consequently the research has made modest contribution to knowledge by the determination of all of the above including the cost benefit analysis carried out.
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Pumipunta, Surachai Quackenbush Stephen L. "Can money buy health? foreign aid, changes in aid, and the impact of human health in sub-Saharan Africa /". Diss., Columbia, Mo. : University of Missouri-Columbia, 2009. http://hdl.handle.net/10355/6721.
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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 23, 2010). Thesis advisor: Dr. Stephen Quackenbush. Includes bibliographical references.
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Lopes, Claudio Rocha. "Caracteriza??o f?sica, qu?mica e energ?tica de biomassa e seus carv?es para inje??o em altos-fornos". Universidade Federal Rural do Rio de Janeiro, 2010. https://tede.ufrrj.br/jspui/handle/jspui/2247.
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2010 - Cla?dio Rocha Lopes.pdf: 2005134 bytes, checksum: 3f0410cad2ed7af0f6a0fb58a582090a (MD5)Made available in DSpace on 2018-04-10T12:58:11Z (GMT). No. of bitstreams: 1 2010 - Cla?dio Rocha Lopes.pdf: 2005134 bytes, checksum: 3f0410cad2ed7af0f6a0fb58a582090a (MD5) Previous issue date: 2010-03-26
The aim of this study was to characterize the main physical and chemical properties, and testing of combustion and CO2 reactivity of biomass, towards its use as material injetante the tuyeres of blast furnaces. This aims to use economic and environmental gains by reducing the rates of carbon emissions and trading of Certified Emission Reductions. The biomass studied were two types of cellulignin: cellulignin from 100% wood and 50% wood + 50% organic matter of trash- MOL, five types of waste biomass in natura: marc barley, macadamia shells, cobs corn, sugar cane bagasse and wood Eucalytus urophylla. Carbonization was carried out at three temperatures (450, 600 and 900 oC) to provide data that could determine the temperature or temperature range in which the ?in natura? biomass and cellulignin should be carbonized to obtain the best properties to use as fuel/reducer in blast furnaces. Simulation tests of injection of powdered materials in blast furnaces were performed with three different masses (200, 250 and 300mg) for setting the rate of injection, after setting the mass to be injected (250mg) studied the carbonaceous were tested to obtain rates of combustion (burning efficiency). Tests were also made of mixtures of biomass with coal of low volatile coal, showing the synergy when mixing these coals. The rates of combustion-IC is obtained from the analysis of gaseous combustion products by gas chromatography. Tests of reactivity to CO2 at three temperatures (950, 1000 and 1050 oC) in order to obtain kinetic data (apparent activation energy and frequency factor) of various coals. The continuous reaction model (Equation Mampel-1st order) was used and the kinetic values obtained from the Arrhenius plot. Correlations of various physical and chemical properties of carbonaceous study (total carbon, fixed carbon, volatile matter, alkali content, density-He, density-Hg, open porosity, total porosity and surface area) compared to the rate of combustion-IC were obtained. It was also correlated the rate of combustion-IC with the values of reactivity to CO2
O objetivo geral deste trabalho foi avaliar a viabilidade de utiliza??o de biomassas e seus carv?es atrav?s da inje??o pelas ventaneiras dos Altos-Fornos - t?cnica conhecida como Inje??o de Carv?es Pulverizados (ICP). Desta forma, diferentes biomassas e seus carv?es tiveram as suas propriedades f?sicas e qu?micas avaliadas, sendo realizados tamb?m testes de combust?o e de reatividade ao CO2. Esta utiliza??o visa ganhos ambientais e econ?micos, atrav?s da redu??o dos ?ndices de emiss?es de carbono e comercializa??o de Certificados de Emiss?es Reduzidas. As biomassas estudadas foram dois tipos de celuligninas: celuligninas provenientes de 100% madeira e celuligninas provenientes de 50% madeira + 50% mat?ria org?nica do lixo, cinco tipos de res?duos de biomassas ?in natura?: baga?o de cevada, cascas de macad?mia, sabugo de milho, baga?o de cana e madeira de Eucalyptus urophylla. Foram realizadas carboniza??es em tr?s temperaturas (450?C, 600?C e 900?C), visando obter dados que pudessem determinar a temperatura ou faixa de temperatura na qual as celuligninas e biomassas ?in natura? devem ser carbonizadas para se obter as melhores propriedades visando a utiliza??o como combust?veis/redutor nos Altos-Fornos. Os carbon?ceos estudados foram ensaiados para a obten??o dos ?ndices de combust?o (efici?ncia de queima). Tamb?m foram realizados testes de misturas de carv?es de biomassas com carv?o mineral baixo vol?til, mostrando a sinergia quando se misturam estes carv?es. Foram realizados ensaios de reatividade ao CO2 em tr?s temperaturas (950?C, 1000?C e 1050?C) com o intuito de obter dados cin?ticos (energia de ativa??o aparente e fator de frequ?ncia) de diversos carv?es. Utilizouse o modelo de rea??o cont?nua (Equa??o de Mampel-1? ordem) e os valores cin?ticos foram obtidos atrav?s do gr?fico de Arrhenius. Correla??es de diversas propriedades f?sicas e qu?micas dos carbon?ceos estudados em rela??o ao ?ndice de combust?o-IC foram obtidas. Tamb?m foi correlacionado o ?ndice de combust?o-IC com os valores de reatividade ao CO2. Os resultados mostraram que as celuligninas CCC3(50% madeira + 50 % lixo) e CCC5 (100% madeira) possuem caracter?sticas semelhantes ao carv?o vegetal tradicional, podendo serem injetadas nas ventaneiras, sem necessidade de carboniza??o. A temperatura de carboniza??o de biomassas deve ser entre 450?C e 600?C, possibilitando melhores rendimentos gravim?tricos e boas caracter?sticas f?sico-qu?micas. De modo geral, os maiores ?ndices de combust?o foram obtidos pelos carv?es carbonizados ? 600?C e pelo Carv?o vegetal tradicional (madeira de Eucalyptus). Avaliando-se as propriedades f?sicas e qu?micas dos materiais carbon?ceos com o ?ndice de combust?o, pode-se dividir os materiais em quatro grupos espec?ficos (grupo de biomassas in natura, grupo das celuligninas, grupo dos carv?es vegetais e grupo dos carv?es minerais). Os valores dos ensaios de reatividade ao CO2 est?o em conson?ncia com os resultados de ?ndice de combust?o, onde os carv?es de celulignina, bem como os carv?es de biomassa tradicional, s?o materiais de alta reatividade com grande potencial para utiliza??o na inje??o em altoforno.
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Xiao, Weifang [Verfasser], Norbert [Akademischer Betreuer] Gebbeken, Norbert [Gutachter] Gebbeken i Hong [Gutachter] Hao. "Experimental and Numerical Investigations on the Effectiveness of Protective Barriers against Air Blast / Weifang Xiao ; Gutachter: Norbert Gebbeken, Hong Hao ; Akademischer Betreuer: Norbert Gebbeken ; Universität der Bundeswehr München, Fakultät für Bauingenieurwesen und Umweltwissenschaften". Neubiberg : Universitätsbibliothek der Universität der Bundeswehr München, 2019. http://d-nb.info/1186723874/34.
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Bacharoudis, Evangelos. "Etude expérimentale et théorique du début de l'atomisation des films liquides cisaillés horizontaux en présence d'un changement brusque de géométrie : application aux essuie-glaces". Thesis, Valenciennes, 2012. http://www.theses.fr/2012VALE0029/document.
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La conduite à grande vitesse d’une voiture dans des conditions dangereuses, tel un environnement très poussiéreux, est une des situations auxquelles sont confrontés les conducteurs. Dans ce cas, les essuie-glaces doivent fonctionner correctement et nettoyer efficacement le pare-brise sale pour à la fois assurer la sécurité des passagers et le bon fonctionnement des différents organes du véhicule. La mise en route des essuie-glaces entraîne l’activation des buses d’injection du liquide nettoyant qui s’atomise et qui se dépose sur les essuie-glaces et le pare-brise. Une fine couche du liquide se développe sur les surfaces des balais d’essuie-glace. Lorsque l’injection s’arrête et que les essuie-glaces continuent leur mouvement, la fine couche de liquide interagit avec le champ d’écoulement d’air extérieur. Il en résulte une génération de gouttelettes qui sont emportées par l’air en s’éloignant des balais d’essuie-glace. Une partie de ces gouttelettes impacte le pare-brise avec pour conséquence un nettoyage insuffisant et une mauvaise visibilité pour le conducteur. Dans cet exemple, les essuie-glaces peuvent à la fois enlever la poussière du pare-brise mais aussi être à l’origine de la formation des gouttelettes et de leur impact sur le pare-brise. Le phénomène d’interaction air-liquide sur les essuie-glaces produisant une génération de gouttelettes, leur transport et leur impact sur le pare-brise est connu sous le vocable ‘Overspray’ dans le domaine de l’automobile. Il est important de tenir compte du phénomène d’Overspray pour la conception et laréalisation des essuie-glaces. Bien que ce phénomène ait été mis en évidence depuis longtemps, les mécanismes qui le régissent demeurent encore peu connus. C’est pour cette raison que les essuie-glaces ne parviennent pas à satisfaire tous les critères de qualité liée à leur fonction. Cette thèse vise à une meilleure compréhension du phénomène de l’Overspray en mettant l’accent sur les interactions air-liquide pour la génération des gouttelettes, et plus particulièrement sur les conditions critiques où le film commence à s’atomiser. Cette étude a été réalisée essentiellement par voie expérimentale à partir de laquelle un modèle a été proposéDriving the car in hazard conditions, like an environment with a lot of dust, is a case which is encountered often by the drivers. The wiper blades have to work successfully and clean the dirty windshield for both the safety of the passengers and the functionality of the car. Activating the car nozzle jets, washer is ejected from the nozzles towards the wiper blades and the windshield. A thin layer of liquid is developed on the surfaces of the wiper blades. When the nozzle jets stop and the wiper blades continue to move, the thin layer of liquid interacts with the strong external air flow field. The result of the interaction is the generation of droplets which are transported by the air flow far from the wiper blades. However, a part of those droplets impact on the windshield resulting in an insufficient cleaning of the screen and the deterioration of the driver’s sight. The wiper blades may remove the dust from the screen but they will cause the droplet impact on it. The phenomenon of the air-liquid interaction on the wiper blades involving the droplet generation, transport and impact on the screen is known as Overspray in the automotive domain. The Overspray is an important parameter for the design and development of the wiper blades. Although Overspray has been observed quite early, little is known for the mechanisms involved in. Thus, the wiper blades still suffer to clean the windshield adequately in such conditions. The current thesis aims to give a deep insight in the Overspray focusing more on the air-liquid interactions for the droplet generation, especially, the investigation of the critical conditions for the onset of the film atomization from the blade surfaces. For that reason mainly experimental and theoretical work has been conducted
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Šenovský, Petr. "Parní kotel s přihříváním páry na spalování vysokopecního plynu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231184.
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The aim of this Diploma thesis is design of steam boiler with steam reheating, for combustion the blast furnace gas. The fuel composition and primary parameters for calculation of the boiler were provided. In the first part the fuel composition is described. The main part of the thesis consists of stoichiometric calculations, establishing efficiency of the boiler, calculating combustion chamber as well as design and calculation individual heating surfaces. Part of the work is also drawing documentation of boiler.
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Dohnal, Jakub. "Kotel na spoluspalovaní vysokopecního plynu a koksárenského plynu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-242878.
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This diploma thesis deals with the constructional and calculation design of boiler for blast furnace and coke gas mixture combustion, including sizing of the heating surfaces. The opening section is dedicated to a brief characterization of burned fuels. The following chapter shows the parameters and composition of the resulting fuel mixture. The main part of this thesis involves; determining the stoichiometric amount air required for combustion and the resulting flue gas, determining the boiler efficiency and steam production rate, calculations regarding the combustion chamber and the detailed design of the individual heat exchangers. At the end of the thesis the heat balance of the entire boiler is verified. Drawing documentation of boiler is also part of this diploma thesis.
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Tyagi, P. K. "Linear Instability Of Laterally Strained Constant Pressure Boundary Layer Flows". Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/265.
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The linear instability of laterally diverging/converging flows is an important aspect towards understanding the laminar-transition process in many viscous flows. In this work the linear instability of constant pressure laterally diverging/converging flow has been investigated.
The laminar velocity field for laterally diverging/converging flows, under the source/sink approximation, has been reduced to two-dimensional flows. This reduction is alternative to the Mangier transformation used earlier. For a constant pressure laterally strained flow, the laminar velocity is found to be governed by the Blasius equation for flow over a flat plate.
The non-parallel linear instability of constant pressure laterally strained flows has been examined. The instability equation is found to be same as that for the Blasius flow. This implies that the stability is same as that for the Blasius flow. A lateral divergence/convergence is shown to alter the Reynolds number from that in a two-dimensional flow. The instability of a laterally converging/diverging flow thus can be obtained from the available results for the Blasius flow by scaling the Reynolds numbers. This leads to the result that while a diverging flow is more unstable than the Blasius flow, a converging flow is more stable. Some additional relevant results are also presented.
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Tyagi, P. K. "Linear Instability Of Laterally Strained Constant Pressure Boundary Layer Flows". Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/265.
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The linear instability of laterally diverging/converging flows is an important aspect towards understanding the laminar-transition process in many viscous flows. In this work the linear instability of constant pressure laterally diverging/converging flow has been investigated.
The laminar velocity field for laterally diverging/converging flows, under the source/sink approximation, has been reduced to two-dimensional flows. This reduction is alternative to the Mangier transformation used earlier. For a constant pressure laterally strained flow, the laminar velocity is found to be governed by the Blasius equation for flow over a flat plate.
The non-parallel linear instability of constant pressure laterally strained flows has been examined. The instability equation is found to be same as that for the Blasius flow. This implies that the stability is same as that for the Blasius flow. A lateral divergence/convergence is shown to alter the Reynolds number from that in a two-dimensional flow. The instability of a laterally converging/diverging flow thus can be obtained from the available results for the Blasius flow by scaling the Reynolds numbers. This leads to the result that while a diverging flow is more unstable than the Blasius flow, a converging flow is more stable. Some additional relevant results are also presented.
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Machara, Radek. "Návrh kotle na spoluspalování vysokopecního plynu a koksárenského plynu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319265.
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The diploma thesis deals with design of gas steam boiler with given parameters of steam. Blast furnace and coke oven gas are used as fuel. At the beginning of this work, both co-fired fuels are presented to us, their chemical analysis and stoichiometry are performed. The main part of the diploma thesis deals with the dimensioning of individual heat exchange surfaces such as steam superheaters, evaporators, economizers and air heaters. All heat exchange surfaces meet recommended parameters such as recommended steam rates, flue gas, etc. At the end, the total heat balance of the boiler is performed. Part of the work is also drawing documentation showing the main dimensions of the boiler. It is also indicated the connection of individual heat exchange surfaces.
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Bedon, Chiara. "Problemi di stabilità negli elementi in vetro strutturale e studio innovativo di facciate in vetro-acciaio sottoposte a carico da esplosione". Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7403.
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2010/2011Recentemente, la richiesta architettonica sempre più spinta di trasparenza e luminosità ha favorito la diffusione nell’edilizia del vetro come materiale da costruzione. Sebbene si tratti di un materiale ancora poco conosciuto rispetto ad altri materiali convenzionali, il vetro trova, infatti, ampia applicazione nelle realizzazioni strutturali più innovative. Anche se le soluzioni architettoniche proposte trovano ampio consenso, spesso la difficoltà principale consiste nel dimensionare adeguatamente tali elementi e nel preservarne l’integrità da eventuali fenomeni di instabilità. Con riferimento a questo tema, nella presente tesi vengono proposte alcune significative formulazioni analitiche per la verifica di stabilità di elementi in vetro monolitico, stratificato o vetro-camera, con particolare attenzione per il comportamento di travi compresse, travi inflesse, pannelli sottoposti a compressione nel piano o taglio nel piano. Allo stesso tempo, viene studiato il comportamento di facciate in vetro-acciaio sottoposte a carico da esplosione, con riferimento specifico a due tipologie di facciata note come facciate continue a lastre indipendenti, controventate da un sistema di cavi pretesi, e facciate a pannelli, nelle quali le lastre di vetro sono sostenute da un telaio metallico di supporto. Per ciascuna tipologia di facciata, vengono evidenziate le criticità dovute a carichi da esplosione di varia intensità mediante opportuni modelli numerici. Inoltre, viene analizzato l’effetto di eventuali dispositivi in grado di mitigarne le componenti principali assorbendo e/o dissipando parte dell’energia d’ingresso associata all’evento esplosivo.
Recently, due to aesthetic and architectural requirements of transparency and lightness, the use of glass as a structural material showed a strong increase. Although its load carrying behavior is actually not well-known, glass finds large application in modern and innovative buildings. Nevertheless, the main difficulties are related to the proper design of these structural elements and in the preservation of their integrity, avoiding possible buckling phenomena. In this context, this Doctoral Thesis proposes a series of interesting analytical formulations suitable for the buckling verification of monolithic, laminated, insulated structural glass element, with particular attention for the load carrying behavior of beams in compression or in bending, as well as for the buckling response of glass panels subjected to in-plane compression or shear. At the same time, the Thesis focuses also on the dynamic behavior of two different typologies of steel-glass façades subjected to air blast loads, whit particular attention to the analysis of cable-supported façades and conventional curtain walls, in which a metallic frame supports the glass panels. In both the circumstances, accurate numerical simulations are performed to highlight the criticalities of similar structural systems, in presence of high-level or medium / low-level air blast loads. Finally, the structural benefits of possible devices able to mitigate the effects of explosions in the main components of these façades, by partly storing / dissipating the incoming energy, are investigated numerically and analytically.
XXIV Ciclo
1983
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Pagani, V. "INTEGRATION OF COMPONENTS FOR THE SIMULATION OF BIOTIC AND ABIOTIC STRESSES IN MODEL-BASED YIELD FORECASTING SYSTEMS". Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/487500.
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The raising global demand for agricultural products and the exacerbated inter-annual fluctuations of food productions due to climate change are increasing world food price volatility and threatening food security in developing countries. In this context, the availability of reliable operational yield forecasting systems would allow policy makers to regulate agricultural markets. However, the reliability of the current approaches (the most sophisticated being based on crop models) is undermined by different sources of uncertainty. In particular, large area simulations can be affected by errors deriving from the uncertainty in input data (e.g., sowing dates, information on cultivar/hybrid grown, management practices) and upscaling assumptions, as well as from the incomplete adequacy of crop models to reproduce the effects of key factors affecting inter-annual yield fluctuations (e.g., extreme weather events, pests, diseases).
The aim of this Ph.D. project was to reduce the uncertainty affecting the existing model-based forecasting systems through: (i) the implementation of approaches for the estimation of the impact of biotic and abiotic stressors on crop yields (based on dynamic models and on dedicated agro-climatic indicators), and (ii) the integration of remote sensing information within crop models. Concerning the first objective, the approaches for the simulation of transplanting shock and cold-induced spikelet sterility in rice included in Oryza2000 and WARM models, respectively, were improved, by increasing the model adherence to the underlying systems. Moreover, generic approaches for the simulation of the impacts of extreme weather events on crop yields were developed and evaluated, as well as approaches specific for sugarcane. For the second objective, remote sensing information was used to derive rice-cropped areas and sowing dates varying with time and space, as well as for the assimilation of exogenous leaf area index data using both recalibration and updating techniques (to account for factors not explicitly reproduced by the model within large-area applications).
The application of the improved forecasting systems to different crops and agro-climatic contexts worldwide led to marked improvements compared to existing approaches. This was achieved through an increase in the percentage of inter-annual yield variability explained. On the one hand, the simulation of the impact of weather extremes (cold shocks, heat waves, water stress and frost) allowed to reduce the tendency of CGMS (the monitoring and forecasting system of the European Commission) to overestimate cereal yields in case of unfavorable seasons. Moreover, the integration of dynamic crop models and of agro-climatic indicators led to enhance the predicting capacity of available approaches. On the other hand, the integration of remote-sensing information within high resolution simulation chains allowed to decidedly reduce the uncertainty of the standard CGMS-WARM system when applied to the main European rice districts.
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Paleari, L. "IN SILICO IDEOTYPING: DEFINITION AND EVALUATION OF RICE IDEOTYPES IMPROVED FOR RESISTANCE/TOLERANCE TRAITS TO BIOTIC AND ABIOTIC STRESSORS UNDER CLIMATE CHANGE SCENARIOS". Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/483333.
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The development of new cultivars better adapted to specific growing conditions is a key strategy to meet an ever-increasing growing global food demand and search for more sustainable cropping systems. This is even more crucial in the context of a changing climate.
Ecophysiological models and advanced computational techniques (e.g., sensitivity analysis, SA) represent powerful tools to analyze genotype (G) by environment (E) interactions, thus supporting breeders in identifying key traits for specific agro-environmental contexts. However, limits for the effective use of mathematical models within breeding programs are represented by the uncertainty in the distribution of plant trait values, the lack of processes dealing with resistance/tolerance traits in most ideotyping studies, the partial suitability of current crop models for ideotyping purposes, and the absence of modelling tools directly usable by breeders.
The aim of this research was to address these issues improving methodologies already in use, proposing new paradigms for the development of crop models explicitly targeting ideotyping applications and developing tools that would encourage a deep interaction of the modelling and breeding communities. The focus was on rice, for its role as staple food for more than a half of world’s population, and on resistance/tolerance traits to biotic/abiotic stressors, for their central role in increasing crop adaptation. Moreover, current conditions and climate change projections were considered, to support the definition of strategies for breeding in the medium-long term.
A standard procedure to quantify − and manage − the impact of the uncertainty in the distribution of plant trait values was developed, using the WARM rice model and the Sobol’ method as case study. The approach is based on a SA (generating sample of parameter distributions) of a SA (generating samples of parameters for each generated distribution) using distributions of jackknife statistics calculated on literature values to reproduce the uncertainty in defining parameters distributions. As a practical implication, the procedure developed allows identifying plant traits whose uncertainty in distribution can alter ideotyping results, i.e., traits whose distributions could need to be refined.
Global SA was then used to identify rice traits putatively producing the largest yield benefits in five contrasting districts in the Philippines, India, China, Japan and Italy. The analysis involved phenotypic traits dealing with light interception, photosynthetic efficiency, tolerance to abiotic stressors, resistance to fungal pathogens and grain quality. Results suggested that breeding for traits involved with disease resistance and tolerance to cold- and heat-induced spikelet sterility could provide benefits similar to those obtained from improving traits affecting potential yield. Instead, advantages resulting from varying traits involved with grain quality were markedly frustrated by inter-annual weather variability. Since results highlighted strong G×E interactions, a new index to derive district-specific ideotypes was developed.
Given the key role of biotic/abiotic stressors in determining actual yield and the deep impact of related G×E interactions, a study was carried out by explicitly focusing on the definition of rice ideotypes improved for their resistance to fungal pathogens and tolerance to abiotic constraints (temperature shocks inducing sterility). The analysis was carried out at district level with a high spatial resolution (5 km × 5 km elementary simulation unit), targeting the improvement of the most representative 34 varieties in six Italian rice districts. Genetic improvement was simulated via the introgression of traits from donor varieties. Results clearly showed that breeders should focus on increasing resistance to blast disease, as this appears as a factor markedly limiting rice yields in Italy, regardless of the districts and climate scenarios, whereas benefits deriving from improving tolerance to cold-induced sterility could be markedly affected by G×E interactions.
To reduce the risk of discrepancies between in silico ideotypes and their in vivo realizations, both studies involved only model parameters with a close relationship with phenotypic traits breeders are working on. However, a long-term strategy to overcome limitations related with the partial suitability of available models would be building new ideotyping-specific models explicitly around traits involved in breeding programs. This proposal for a paradigm shift in model development was illustrated taking salt stress tolerance and rice as a case study. Dedicated growth chamber experiments were conducted to develop a new model explicitly accounting for tolerance traits modulating Na+ uptake and distribution in plant tissues, as well as the impact of the accumulated Na+ on photosynthesis, senescence and spikelet sterility. An ideotyping study was conducted at two sites (in Greece and California) characterized by different seasonal dynamics of salinity in field water. Results showed how, under different scenarios, traits assuring the largest contribution to the overall tolerance could refer to completely different physiological mechanisms: tissue tolerance in one case, sodium exclusion in the other. This encourages the development of explicit trait-based approaches to increase the integration of crop models within breeding programs.
A parallel path to achieve this goal is the development of modelling platforms targeting breeders as final users, who does not have necessarily in-depth skills in crop modelling and IT. The platform ISIde, derived from a close collaboration between target users, biophysical modelers and IT specialists, represents the first prototype of a platform specifically developed for being used directly by breeders to evaluate in silico improved varieties at district level.
This thesis demonstrated the usefulness of simulation models for the definition of ideotypes for specific agro-environmental conditions. Targeting ideotyping applications, new methodologies, paradigms for model development and modelling tools were developed, thus contributing to improve the potential of crop modelling to support breeding programs. Future developments will target researches aimed at overcoming the limits behind this study, i.e., (i) absence of explicit interactions between traits, (ii) no adaptation strategies considered, and (iii) lack of approaches for the simulation of the evolutionary potential of pathogens in response to long-term climate variations and increased host resistance.
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Samuelraj, I. Obed. "Experiments on Varying Intensity Air Blasts in Shock Tubes". Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4251.
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Abstract
In the recent past, with an increasing number of terrorist activities, blast related research has focused on conducting careful experiments to develop newer protection strategies. As field experiments using explosives themselves are very cumbersome and expensive, shock tubes are increasingly being employed to study these air-blast based phenomena as they can produce the instantaneous pressure rise that is associated with blast waves, minus the use of explosives. From the literature on shock tubes that are being used for blast loading, it was observed that no experiments have been reported in the sub-millisecond loading duration (near-field) regime as no extant facility has the capability to simulate the conditions in this regime. Even in reports on shock tubes being used to recreate far-field blast conditions (starting from _ 4 milliseconds), attention is not directed towards the shock tube experiment artefacts viz., repeated reflections inside the (closed) shock tube, and generation of a wave whose pressure remains steady for a time before dropping off like a blast wave. In this backdrop, shock tube experiments that pertain to the far-field conditions were first conducted and then quantified in terms of the equivalent TNT field explosion (’TNT equivalent’ in short). The decay time was brought down to 1:6 ms by using plastic diaphragms, and an insert to channel out the reflected shock pressure. Then, the role played by the artefacts of shock tube loading on plates was shown to erroneously increase the final deformation of metal plates by about 15%. While the effect of these artefacts on the micro-structure did not show a large difference, the frequency content of both pressure loadings (the artefact and the correct one), showed differences in the spectral content, which could potentially change the response of structures that are sensitive to the frequency content of the input pulse. These shock tube experiments were found to have a repeatability of 5.5% and the plate deformation experiments on this facility were in the dynamic regime of structural loading. Using a more repeatable diaphragm less shock tube (1%), experiments were then conducted with similar decay times but on a smaller shock tube to validate the digital image correlation (DIC) technique. This device was then used along with numerical computations on ABAQUS to try and explain a blast mitigation strategy that gave a reduction in deflection of up to 50% in the quasi-static regime. To generate even shorter decay times, experiments using a piston impacting a water column were conducted. While the blast pulses from this facility could be reported in terms of their TNT equivalent mass, a subsequent correlation with the explosion-based plate deflection data failed as the exact impulse that is imparted to the plate could not be correctly determined. A novel conical shock tube that can generate sub-millisecond decay times (the near field conditions) in air was then developed and experiments on different metal plates (mild steel, aluminium, copper) were conducted for the extreme case of structural loading, viz., impulsive loading. The plate deflection data from this facility compared very well with an empirical formula that is available for impulse loading of plates using explosives. Thus, the ability of this device to reproduce several features of a near-field air-blast loading - namely the elastic spring back, the impulsive loading of a plate, and a unique shape of the deformed plates - were all successfully demonstrated. The device was characterized at reduced pressures to have a repeatability of 5% and the spatial variation in the exit plane pressure was better than 7%. Using this device, a scaled equivalent of a possible explosion from an improvised explosive device (IED) was also administered to mice to explore the possibility of ultimately conducting controlled blast induced traumatic brain injury studies in the laboratory. Over the course of this work, the simulation capability of shock tubes over an extended range of air-blasts was demonstrated. In terms of TNT masses and stand-off distance, it is currently as follows: Far and mid-field range - using the diaphragm less shock tube (49 kg@5:3m –25 kg@8:4m), and using the vertical shock tube from (0:31 kg@0:86m–33 kg@6:4m); Near-field range: water shock tube (2 kg@0:63m) and the conical shock tube (0:04 kg@0:38m– 0:08 kg@0:56m).
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Ballantyne, Graeme. "Air-blast effects on structural shapes". 2007. http://proquest.umi.com/pqdweb?did=1397912771&sid=7&Fmt=2&clientId=39334&RQT=309&VName=PQD.
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Thesis (M.S.)--State University of New York at Buffalo, 2007.Title from PDF title page (viewed on Feb. 14, 2008) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Whittaker, Andrew. Includes bibliographical references.
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Thom, Christopher. "Soft Materials under Air Blast Loading and Their Effect on Primary Blast Injury". Thesis, 2009. http://hdl.handle.net/10012/4861.
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Injury from blast is significant in both military and civilian environments. Although injuries from blast are well-documented, the mechanisms of injury are not well understood. Developing better protection requires knowledge of injury mechanisms and material response to blast loading. The importance of understanding how soft materials such as foams and fabrics behave under blast loading is further apparent when one realizes the capacity for some of these materials, frequently used in protective ensembles, to increase the potential for injury under some conditions. The ability for material configurations to amplify blast pressure and injury has been shown experimentally by other researches, and numerically in this study.
Initially, 1-D finite element and mathematical models were developed to investigate a variety of soft materials commonly utilized in ballistic and blast protection. Foams, which have excellent characteristics in terms of energy absorption and density, can be used in conjunction with other materials to drastically reduce the amplitude of the transmitted pressure wave and corresponding injury.
Additionally, a more fundamental examination of single layers of fabric was undertaken to investigate to the effects of parameters such as fabric porosity and density. Shock tube models were developed and validated against experimental results from the literature. After the models were validated, individual fabric properties were varied independently to isolate the influence of parameters in ways not possible experimentally. Fabric permeability was found to have the greatest influence on pressure amplification. Kevlar, a ballistic fabric, was modelled due to its frequent use for fragmentation protection (either stand-alone or in conjunction with a hard ballistic plate).
The developed fabric and foam material models were then utilized in conjunction with a detailed torso model for the estimation of lung injury resulting from air blast. It was found that the torso model predicted both amplification and attenuation of injury, and all materials investigated as a part of the study had the capacity for both blast amplification and attenuation. The benefit of the models developed is that they allow for the evaluation of specific protection concepts.
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Li, Larry Kin Bong. "An experimental study on air-blast atomization of viscoelastic liquids". Thesis, 2006. http://hdl.handle.net/2429/18309.
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Motivated by the need to improve transfer efficiencies in spray coating, an experimental investigation into viscoelastic atomization using pre-formulated substitute test liquids is presented. These model liquids allowed for the decoupling of two common rheological phenomena: extension-thickening and shear-thinning. By maintaining similar values of surface tension, density, and rate-independent shear viscosity in the test liquids, and independently varying the extensional viscosity, the effect of elasticity was isolated and shown to act against the breakup of a spray issuing from a plain-jet air-blast atomizer operating at high aerodynamic Weber numbers (~1000). Flash photography revealed the presence of large-scale filamentary structures at breakup, which delayed discrete droplet formation until farther downstream of the atomizer where relative air-liquid velocities were reduced. Consequently, liquid elasticity led to an increase in the mean droplet size. This was confirmed by shadowgraphy measurements. Moreover, the hindering influence of elasticity on atomization was also supported by Particle Image Velocimetry measurements, which indicated that the elastic droplets, owing to their greater inertia, were better able to maintain their initial momentum.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
40
Huang, Chi-Fong, i 黃基峰. "Study on Air-cooled Blast Furnace Slag Used for Pervious Concrete". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/75562026721968897095.
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碩士國立屏東科技大學
土木工程系所
102
This study used China Steel Corporation (CSC) byproduced air-cooled blast furnace slag as aggregate material in the making of pervious concrete. The pervious concrete specimens were built according to respective water-cement ratios W/C ranged from 0.37 to 0.49, whilst aggregate particle size was between 4.8~19.1 mm. Tamping tools were two steel rods, one with 5 cm diameter round bottom, 2 cm thickness and the other with 5×5 cm square bottom, 2 cm thickness, were used to impact cylindrical and beam specimens respectively. The specimens were made by the same degree of impacting, and were performed the compressive strength, flexural strength, permeability coefficient, and porosity tests. Hopefully, the W/C of maximum strength concrete was found, and the requirements of permeability and water retention were satisfied as well. Test results showed that, both the 28 day maximum compressive strength fc and maximum modulus of rupture R occurred at W/C=0.48. The values were fc=171.4kgf/cm2 and R=41.1kgf/cm2. The mix for this specific W/C was 350 kg cement, 160 kg water, 3.5 kg curing agent and 1375 kg slag aggregate. The ratio of the 28 day compressive strength to modulus of rupture R/fc were between 0.18~0.27, averaged at 0.22, higher than that of normal concrete about 0.15. The permeability coefficient k values ranged between 0.66~2.41 cm/sec, larger than the criteria value 0.01 cm/sec proposed by Architecture and Building Research. The n values ranged between 18.5%~32.5%, also larger than the criteria value 15%.
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Jyun-YanWu i 吳俊諺. "Failure Analysis of the Reinforced Concrete Plate Subjected to Air Blast Loading". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/51019497936828577088.
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碩士國立成功大學
土木工程學系碩博士班
98
Blast can cause serious damage to building structure as well as heavy loss of live and property. It is increasingly necessary and in fact required to carry out extensive research in this field when increased terrorism and local conflicts become worse. The terrorist explosion activities are increasingly concerns which could harm the national security and the social stability. The blast effect on buildings is of widely interest to researchers and engineers all over the world. Accordingly, this study to the nonlinear finite element software LS-DYNA, by select adequacy the material parameters and equation of state (EOS) to perform numerical computation related to the explosive detonates in free air. And then to examine the dynamic characteristics of the reinforced concrete structures. The results of this study provide a valuable reference for engineering designers and researchers to precede the structural dynamic analysis.
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Alexander, Nicholas Anthony. "Controlled recirculation of mine ventilation air: its effect on blast contaminant dissipation". Thesis, 2014. http://hdl.handle.net/10539/15528.
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A series of tests was undertaken on a recirculation scheme in a deep
level gold mine to establish the effect of controlled recirculation of
the mine ventilation air on blast contaminant dissipation.
Clarification was needed as to whether the existing re-entry interval
of three hours would have to be extended with the introduction of
controlled recirculation. The re-entry interval is a time interval,
after blasting, stipulated by the Inspector of Mines during which the
workings are being cleared of blast contaminants and during which time
no persons are permitted tc enter the workings.
The fresh and recirculated air flow rates were varied and their effects
on blast contaminant dissipation measured. Gas concentrations of the
oxides of nitrogen (N0X ) and carbon monoxide were monitored
continuously in the return air. Dust levels were monitored in the
return air from two hours before the blast to four hours after the
blast.
Two gas models (mixed-volume and plug-flow) and residence time analysis
were used to analyse the data.
In all the tests, the critical blast contaminant for determining the
re-entry interval was found to be NO*. In addition, the following
parameters affected the re-entry interval; the amount of explosives
ignited daily, the volume of the workings into which the NO* is
dissipated by the ventilating air, the time taken for air to complete
one circuit (the cycle time), leakage and short circuiting of air, and
the fresh air flow rate. The recirculated air flow rate was found to
have negligible effect on the re-entry interval.
43
YAW, HWA LEOU, i 柳耀華. "Vibration Analysis of Rotating Blades Subjected to Sinusoidal Air Loading". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/45645977521840035731.
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44
Liu, Yang. "Linear and nonlinear analysis of a clamped plate subjected to air-blast loading". 2007. http://hdl.handle.net/1993/20550.
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45
Lin, Shih-Jie, i 林士傑. "Numerical Simulation and Analysis of Methanol Atomization and Reforming Employing an Air-blast Atomizer". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/12071070202633293685.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
航空太空工程學系碩博士班
97
A numerical simulation model for the analysis of methanol reformers is developed in the present study. It has been applied to the analysis of two cylindrical methanol reformers. One is an isothermal methanol reformer, employing the catalyst of Cu/ZnO, the other is an auto-thermal reformer with the catalyst of Pt/CeO_2-ZrO_2. The methanol conversion and the hydrogen generation rates are predicted by the present simulation model in good agreement with the experiments. It has also been found that for the isothermal methanol reformer, increasing the space velocity and the thermal conductivity of the catalyst enhances the conversion of methanol. For the auto-thermal reformer, it is found that the reaction rate of the partial oxidation is relatively lower than those of the methanol decomposition and the water-gas shift reaction. In the present study, it is also found that the trends of the temperature distribution and the methanol conversion rate are consistent with the experimental results. The present study further analyzes an ATR reactor installed with an air-blast atomizer for atomizing liquid methanol. The detailed distributions of the flow field, temperature, and species concentration are predicted. It is found that both enlarging the spray angle and reducing the spray nozzle size increase the Methanol conversion rate and the reaction temperature .
46
Lin, Cyun-Syuan, i 林群軒. "Study on Air-cooled Blast Furnace Slag Used for Pervious Concrete of Low Cement Amount". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/94544501454923624453.
Pełny tekst źródłaStreszczenie:
碩士國立屏東科技大學
土木工程系所
103
The thesis used the air-cooled blast furnace (ABF) slag by China Steel Corporation (CSC) as aggregate and added the inorganic ion curing agent by Johnson Corporation in the making of pervious concrete. The water-cement ratios W/C of pervious concrete specimens ranged from 0.62 to 0.76. Aggregate particle size was between 4.75~19.0 mm. Cement amount C in the mix is 150 kg. Tamping tools were two steel rods, one with 5 cm diameter round bottom, 2 cm thickness, and the other with 5#westeur024#5 cm square bottom, 2 cm thickness, were used to impact cylindrical and beam specimens respectively. The specimens were made by the same degree of impacting, and were performed the compressive strength, flexural strength, permeability coefficient, and porosity tests. The purpose of the tests is to find the W/C of maximum strength for the concrete, which also have to meet the permeability and water retention requirements. Test results showed that, both the W/C of the maximum strength of 28 day concrete were 0.72. The values of the compressive strength fc and modulus of rupture R were 41.3 kgf/cm2 and 16.3 kgf/cm2 respectively. Compared with the values 171 kgf/cm2 and R=41.1 kgf/cm2 of C=350 kg, the strengths were its 0.24 and 0.4 time. The mix for this specific W/C was 167 kg cement, 75.2 kg water, 1.7 kg curing agent and 1484 kg slag aggregate. The ratio of the 7 day to 28 day compressive strength fc7/fc28 were between 0.63~1.09, averaged at 0.87. The ratio of modulus of rupture Rc7/Rc28 were between 0.63~1.23, averaged at 0.99, higher than 0.70 of normal concrete or 0.85 and 0.92 of C=350 kg concrete. The ratio of the 28 day compressive strength to modulus of rupture R/fc were between 0.26~0.40, averaged at 0.31, higher than 0.15 of normal concrete or 0.22 of C=350 kg concrete. All the permeability coefficient k values exceeded 2.3 cm/sec, far beyond the criteria value 0.01 cm/sec proposed by Taiwan Architecture and Building Center. The porosity n values ranged between 37%~45%, were also larger than the criteria value 15%. The strengths fc＝41.3 kgf/cm2 and R＝16.3 kgf/cm2 of the tested C=150kg ABF slag previous concrete can be used in class B pavement proposed by Taiwan Architecture and Building Center for load layer of 6 cm depth, and can be used in class A pavement for load layer of 10 cm depth.
47
Feng-YuWu i 吳?宇. "Analyses of the Start-up and Steady Reactions of Methanol Reforming Employing an Air-blast Atomizer". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/30514842681952147908.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
航空太空工程學系專班
98
The start-up process, methanol conversion and hydrogen production of the auto-thermal reformer (ATR) have been investigated by numerical simulation in the present study. The employed catalyst is Pt/CeO2-ZrO2. For the start-up process of the investigated ATR, the sparking plug is employed to ignite methanol, providing thermal energy and heating up the catalyst. As the catalyst meets the self-sustained condition, the sparking plug is shut down and the reforming reaction proceeds to the stable condition. The simulation results show that the start-up process of ATR takes less than 2 minutes when the methanol atomizer is employed. Under steady operation, increasing the air-inlet temperature has no effect on the conversion rate while it slightly reduces the hydrogen production. The results of simulation indicate that employing the atomizer leads to shorter start-up time than that of the case by gaseous feeding. The feasibility of heating the catalyst by spark ignition has been observed. The technique of spark ignition has significant benefit on the reduction of energy loss for the start-up process of the methanol reformer.
48
Argod, Vikas Belegundu Ashok D. "MPI enabled shape optimization of solid isotropic plates to mitigate the effects of air blast loading". 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-3974/index.html.
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49
Deshpande, Sachin V. "Analysis Of Sulphur Hexafluoride Gas Blast Arc By A Mathematical Model". Thesis, 1997. https://etd.iisc.ac.in/handle/2005/1818.
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50
Deshpande, Sachin V. "Analysis Of Sulphur Hexafluoride Gas Blast Arc By A Mathematical Model". Thesis, 1997. http://etd.iisc.ernet.in/handle/2005/1818.
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