11 research outputs found
The effects of irradiation on the creep and hardening behavior of crystalline and amorphous materials
Get PDFUnderstanding the mechanical behavior of nanostructured and amorphous materials under harsh environments such as high irradiation dose and temperature is one of the major constraints in the development of novel materials for nuclear applications. This thesis explores the effects of irradiation on the mechanical properties of several model alloys in the context of irradiation induced creep and irradiation induced hardening. Three different systems were studied to elucidate the creep behavior under energetic particle irradiation; single crystal Ag, nanocrystalline high entropy alloys, and amorphous alloys. 1) In the Ag nanopillars, the ion irradiation induced creep rate increases linearly at lower stresses, i.e. below ≈ 2/3 the high temperature yield stress and parabolically with pillar diameter for diameters less than ≈ 300 nm. The size dependence results from a competition between the relative flux of point defects to surfaces versus internal sinks; i.e. dislocations. 2) In nanocrystalline high entropy alloys, the measured ion beam induced creep compliance varies directly with the inverse grain size. The activation energy for vacancy migration in the recombination regime is measured to be ~ 0.7 eV. The sluggish diffusion behavior often cited as a novel feature of these alloys has very limited effect on the observed creep behavior. 3) A low (200 keV or 80 keV) energy electron beam is used to induce creep in SiO2, Fe79B16Si5, CuTi and CuTa metallic glasses. In SiO2 and Fe79B16Si5 irradiation induced creep rates are sufficiently high to suggest that recoils as low as ≈ 1 eV should contribute to creep.
The distinct microstructure resulting from irradiation induced self-organization of highly immiscible Cu-W alloys system is used to understand the relative importance of composition, solubility, precipitate distribution, morphology on hardening mechanisms. 1) During room temperature irradiation, a nanograin solid-solution strengthening mechanism with a linear compositional dependence is observed for the as-grown alloys and for the alloy samples irradiated to 0.5 dpa. Solid solution strengthening is the major strengthening mechanism for Cu99.5W0.5 at all irradiation doses. Irradiation induces precipitation in samples with W concentrations greater than or equal to 1 at% W at doses above > 0.5 dpa. The growth of 1-4 nm precipitates enhances the hardness of these alloys, and the degree of strengthening is determined by the interparticle spacing. While the alloys exhibit steady-state properties after relatively low dose (≈1 dpa), the different time scales associated with detwinning and damage accumulation in pure Cu lead to transients at higher doses (>5 dpa). 2) High temperature irradiation and annealing following room temperature irradiation results in the formation of precipitate denuded zones, distinct areas around grain boundaries that are devoid of W precipitates The PDZs in the irradiated samples are a result of self-organization and the hardness scales linearly with the width of the PDZs.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-08-01The student, Gowtham Sriram Jawaharram, accepted the attached license on 2019-05-21 at 13:55.The student, Gowtham Sriram Jawaharram, submitted this Dissertation for approval on 2019-05-21 at 14:13.This Dissertation was approved for publication on 2019-05-28 at 11:46.DSpace SAF Submission Ingestion Package generated from Vireo submission #13986 on 2019-11-26 at 13:59:26Made available in DSpace on 2019-11-26T20:56:44Z (GMT). No. of bitstreams: 7
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THE EFFECTS OF IRRADIATION ON THE CREEP AND HARDENING BEHAVIOR OF CRYSTALLINE AND AMORPHOUS MATERIALS.docx: 14045474 bytes, checksum: 8d92ffcc19d7162716108a90a3cec610 (MD5)
Chapter 4.pdf: 101947 bytes, checksum: 228d5bc53b688265325dde167a4fa681 (MD5)
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Previous issue date: 2019-05-28Embargo set by: Seth Robbins for item 112998
Lift date: 2021-11-26T20:56:50Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 112998
Lift date: 2021-11-26T20:58:03Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 112998
Lift date: 2021-11-26T20:58:44Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 112998
Lift date: 2021-11-26T20:59:54Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 112998 on 2021-11-27T10:15:27Z
Revision Control System (RCS) in computational sciences and engineering curriculum
No full textThe Revision Control System (RCS) is an essential aspect of software development process and software configuration management. While continuing to be an integral component of the real world, it is often left out of the main stream curriculum in most academic institutions. Instead, students are expected to learn it on their own, as a hobby or as an independent study, out of personal interest. The author describes the experiences gained from attempting to implement a distributed Revision Control System, Git, as part of the computational sciences and engineering curriculum at the undergraduate and graduate levels. The author also describes the advantages for both parties involved: improving the competency of students and preparing them for the real world expectations while providing the teacher an opportunity to provide timely feedback to the students and monitor their progress. The availability of free and open source tools used to analyze and visualize the commit history to the repository helps teachers and students observe submission and feedback patterns respectively
Setting up Z-scan experiment to study nonlinear optical properties of polymer composites: Characterization of ADP doped PVA/PVP polymer films
No full textZ-scan experiment to study polymer composites was setup by following the technique stated by Sheik-Bahae etal. ADP doped PVA/PVP polymer composites were synthesized by solution casting method. Optical properties were studied using UV Vis and open aperture Z-scan techniques. The third order nonlinear optical properties were investigated using 9ns pulsed Q-switch Nd:YAG laser at 1064nm with a repetition rate of 10Hz. The nonlinear absorption coefficient β, the molecular two photon absorption cross sections σ2, σ′2 and the imaginary part of third order optical nonlinearity χ(3) were calculated. Results indicate that these composites are potential nonlinear optical material for device application
Performance Analysis of a Low Power High Speed Hybrid Full Adder Circuit and Full Subtractor Circuit
No full textIn this paper, a hybrid 1-bit adder and 1-bit Subtractor designs are implemented. The hybrid adder circuit is constructed using CMOS (complementary metal oxide semiconductor) logic along with pass transistor logic. The design can be extended 16 and 32 bits lately. The proposed full adder circuit is compared with the existing conventional adders in terms of power, delay and area in order to obtain a better circuit that serves the present day needs of people. The existing 1-bit hybrid adder uses EXNOR logic combined with the transmission gate logic. For a supply voltage of 1.8V the average power consumption (4.1563 µW) which is extremely low with moderately low delay (224 ps) resulting because of the deliberate incorporation of very weak CMOS inverters coupled with strong transmission gates. At 1.2V supply the power and delay were recorded to be 1.17664 µW and 91.3 ps. The design was implemented using 1-bit which can also be extended into a 32-bit design later. The designed implementation offers a better performance in terms of power and speed compared to the existing full adder design styles. The circuits were implemented in DSCH2 and Microwind tools respectively. The parameters such as power, delay, layout area and speed of the proposed circuit design is compared with pass transistor logic, adiabatic logic, transmission gate adder and so on. The circuit is also designed with a decrease in transistors in order to get the better results. Full Subtractor, a combinational digital circuit which performs 1-bit subtraction with borrow in is designed as a part of this project. The main aim behind this part of the project is to design a 1-bit full Subtractor using CMOS technology with reduced number of transistors and hence the efficiency in terms of area, power and speed have been calculated is designed using 8,10,15and 16 transistors. The parameters were calculated in each case and the results have been tabulated
Superior mesenteric vein thrombosis as a complication of cecal diverticulitis: A case report
No full textAbstractPylephlebitis is an uncommon complication of uncontrolled intra-abdominal infection that is associated with high morbidity and mortality. We present our experience with a unique case of cecal diverticulitis and septic thrombophlebitis of the superior mesenteric vein that was promptly diagnosed with high-resolution imaging and blood cultures. Antibiotic and anticoagulation therapy was instituted on confirming the diagnosis with magnetic resonance imaging (MRI) to control the infection and prevent propagation of the thrombus. Our case report raises awareness about a rare and potentially fatal condition and provides appropriate imaging supplementation to aid in timely diagnosis
Influence of Sloping Ground and Pile Group on Sand Reliquefaction Behavior using Centrifuge Modelling
Get PDFIn the present study free field and pile group models were experimented in a sloping ground using centrifuge modelling. A 2 × 2 pile group model was inserted in Toyoura sand and results were compared with that of free field model ground. Tapered sinusoidal waveform was inputted at a constant 1 Hz shaking frequency, whereas acceleration amplitude and shaking duration for the mainshocks were considered twice that of foreshocks and aftershocks. Two different seismic sequences with six shaking events were imparted to the model grounds to investigate the influence of slope and presence of pile group on sand reliquefaction behavior. The time history responses were recorded in the form of acceleration, excess pore pressure (EPP), bending moment, and lateral displacement and presented. The response indicates that sloping ground was stable under the action of foreshocks, whereas it collapsed during mainshocks, primarily due to liquefaction. The mainshock has transformed the gently inclined sloping ground to levelled ground model. Presence of slope has resulted in higher EPP response and bending moment values compared to levelled ground. GeoPIV analysis and visualization show the flow of sand particles from upside to downside due to lateral spreading at shallow depths that initiated the slope failure.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Authoring Consistent Landscapes with Flora and Fauna
Get PDFInternational audienceWe present a novel method for authoring landscapes with flora and fauna while considering their mutual interactions. Our algorithm outputs a steadystate ecosystem in the form of density maps for each species, their daily circuits, and a modified terrain with eroded trails from a terrain, climatic conditions, and species with related biological information. We introduce the Resource Access Graph, a new data structure that encodes both interactions between food chain levels and animals traveling between resources over the terrain. A novel competition algorithm operating on this data progressively computes a steady-state solution up the food chain, from plants to carnivores. The user can explore the resulting landscape, where plants and animals are instantiated on the fly, and interactively edit it by over-painting the maps. Our results show that our system enables the authoring of consistent landscapes where the impact of wildlife is visible through animated animals, clearings in the vegetation, and eroded trails. We provide quantitative validation with existing ecosystems and a user-study with expert paleontologist end-users, showing that our system enables them to author and compare different ecosystems illustrating climate changes over the same terrain while enabling relevant visual immersion into consistent landscapes
The theoretical prediction of the boundary-layer-blockage and external flow choking at moving aircraft in ground effects
No full textThe theoretical discoveries of the Sanal flow choking [V. R. Sanal Kumar et al., "Sanal flow choking: A paradigm shift in computational fluid dynamics code verification and diagnosing detonation and hemorrhage in real-world fluid-flow systems,"Global Challenges 4, 2000012 (2020)] and streamtube flow choking [V. R. Sanal Kumar et al., "Deflagration to detonation transition in chemical rockets with sudden expansion/divergence regions,"AIAA Paper No. 2020-3520, 2020] achieved significant contemplation in all branches of science and engineering for resolving various unanswered scientific questions brought onward from the beginning of this era [V. R. Sanal Kumar et al., "A closed-form analytical model for predicting 3D boundary layer displacement thickness for the validation of viscous flow solvers,"AIP Adv. 8, 025315 (2018)]. The applications of these flow choking phenomena are more significant in aerospace industries [V. R. Sanal Kumar et al., "Nanoscale flow choking and spaceflight effects on cardiovascular risk of astronauts - A new perspective,"AIAA Paper No. 2021-0357, 2021] and medical sciences [V. R. Sanal Kumar et al., "Lopsided blood-thinning drug increases the risk of internal flow choking leading to shock wave generation causing asymptomatic cardiovascular disease,"Global Challenges 2021, 2000076]. Herein, as an offshoot of the Sanal flow choking phenomena, the proof of the concept of boundary-layer-blockage (BLB) persuaded external-flow-choking (EFC) at aircraft-in-ground (AIG)-effect is presented. When the aircraft's ground clearance is relatively low, the evolving BLB factor from both planes (the bottom surface of the aircraft and the ground) creates a transient fluid-throat, leading to the Sanal flow choking and supersonic flow development in the duct flow region. In this physical situation, the pressure ratio (Ptotal/Pstatic) at the external flow choking region is exclusively a function of the specific heat ratio of the fluid. The EFC is more prone for the low wing aircraft flying in the near vicinity to the ground and/or sea with relatively high subsonic Mach number and low angle of attack. At this flying condition, the underside of the aircraft (fuselage and/or wing) and the ground creates the convergent-divergent duct flow effect leading to the EFC at the critical total-to-static pressure ratio. The accurate estimation of the BLB factor at the location of the EFC at AIG effect is presented in this manuscript as a universal yardstick for two-dimensional (2D) in silico simulation. For establishing the proof of the concept of external flow choking and supersonic flow development and shock wave generation, the 2D in silico results are presented for both stationary and moving airfoils in ground effect. In silico results show that the airfoil at stationary position exhibits relatively higher BLB factor and an immediate occurrence of the EFC than the same airfoil moving with the identical inflow Mach number and Reynolds number. We could establish herein that the moving vehicle simulation is inevitable for capturing actual flow physics and further precise examination of the BLB factor and the possibilities of the occurrence of the EFC for credible trajectory optimization of high-speed ground-effect vehicles. © 2021 Author(s).12 month embargo; published online: 11 March 2021This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Contributions of the international plant science community to the fight against human infectious diseases - part 1: epidemic and pandemic diseases.
Get PDFInfectious diseases, also known as transmissible or communicable diseases, are caused by pathogens or parasites that spread in communities by direct contact with infected individuals or contaminated materials, through droplets and aerosols, or via vectors such as insects. Such diseases cause ~17% of all human deaths and their management and control places an immense burden on healthcare systems worldwide. Traditional approaches for the prevention and control of infectious diseases include vaccination programmes, hygiene measures and drugs that suppress the pathogen, treat the disease symptoms or attenuate aggressive reactions of the host immune system. The provision of vaccines and biologic drugs such as antibodies is hampered by the high cost and limited scalability of traditional manufacturing platforms based on microbial and animal cells, particularly in developing countries where infectious diseases are prevalent and poorly controlled. Molecular farming, which uses plants for protein expression, is a promising strategy to address the drawbacks of current manufacturing platforms. In this review article, we consider the potential of molecular farming to address healthcare demands for the most prevalent and important epidemic and pandemic diseases, focussing on recent outbreaks of high-mortality coronavirus infections and diseases that disproportionately affect the developing world
Contributions of the international plant science community to the fight against infectious diseases in humans-part 2: Affordable drugs in edible plants for endemic and re-emerging diseases.
Get PDFThe fight against infectious diseases often focuses on epidemics and pandemics, which demand urgent resources and command attention from the health authorities and media. However, the vast majority of deaths caused by infectious diseases occur in endemic zones, particularly in developing countries, placing a disproportionate burden on underfunded health systems and often requiring international interventions. The provision of vaccines and other biologics is hampered not only by the high cost and limited scalability of traditional manufacturing platforms based on microbial and animal cells, but also by challenges caused by distribution and storage, particularly in regions without a complete cold chain. In this review article, we consider the potential of molecular farming to address the challenges of endemic and re-emerging diseases, focusing on edible plants for the development of oral drugs. Key recent developments in this field include successful clinical trials based on orally delivered dried leaves of Artemisia annua against malarial parasite strains resistant to artemisinin combination therapy, the ability to produce clinical-grade protein drugs in leaves to treat infectious diseases and the long-term storage of protein drugs in dried leaves at ambient temperatures. Recent FDA approval of the first orally delivered protein drug encapsulated in plant cells to treat peanut allergy has opened the door for the development of affordable oral drugs that can be manufactured and distributed in remote areas without cold storage infrastructure and that eliminate the need for expensive purification steps and sterile delivery by injection
