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Studies On Stable Crack Growth, Mohammed Juma Humaid Al-Ghafri 2017 United Arab Emirates University

Studies On Stable Crack Growth, Mohammed Juma Humaid Al-Ghafri

Theses

The goal of this work is to experimentally investigate the stable crack growth (SCG) fracture behavior of AISI 4340 alloy steel. A series of mode I and mixed mode SCG fracture tests were carried out on 8 mm thick compact tension (CT) specimens subjected to quasistatic loading. The wire cutting technique was used to introduce a pre-notch/ pre-crack of 0.05 mm root radius to the specimen. Five different loading angles Ψ between the loading axis and the crack surface were employed; 90° (mode I), 75°, 65°, 60° and 50°. Five different ratios of original crack length to specimen width ...


52nd Rocky Mountain Conference On Analytical Chemistry, 2017 University of Denver

52nd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 52nd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Snowmass, Colorado, August 1-5, 2010.


53rd Rocky Mountain Conference On Analytical Chemistry, 2017 University of Denver

53rd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 53rd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Snowmass, Colorado, July 24-28, 2011.


55th Annual Rocky Mountain Conference On Magnetic Resonance, 2017 University of Denver

55th Annual Rocky Mountain Conference On Magnetic Resonance

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 55th annual meeting of the Rocky Mountain Conference on Magnetic Resonance, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Denver, Colorado, July 28 - August 1, 2013.


Effective Mechanical Properties Of Multilayer Nano-Heterostructures, T Mukhopadhyay, A Mahata, S Adhikari, Mohsen Asle Zaeem 2017 Missouri University of Science and Technology

Effective Mechanical Properties Of Multilayer Nano-Heterostructures, T Mukhopadhyay, A Mahata, S Adhikari, Mohsen Asle Zaeem

Materials Science and Engineering Faculty Research & Creative Works

Two-dimensional and quasi-two-dimensional materials are important nanostructures because of their exciting electronic, optical, thermal, chemical and mechanical properties. However, a single-layer nanomaterial may not possess a particular property adequately, or multiple desired properties simultaneously. Recently a new trend has emerged to develop nano-heterostructures by assembling multiple monolayers of different nanostructures to achieve various tunable desired properties simultaneously. For example, transition metal dichalcogenides such as MoS2 show promising electronic and piezoelectric properties, but their low mechanical strength is a constraint for practical applications. This barrier can be mitigated by considering graphene-MoS2 heterostructure, as graphene possesses strong mechanical properties. We ...


Limitations Of Poole–Frenkel Conduction In Bilayer Hfo2/Sio2 Mos Devices, Richard G. Southwick III, Justin Reed, Christopher Buu, Ross Butler, Gennadi Bersuker, William B. Knowlton 2017 Boise State University

Limitations Of Poole–Frenkel Conduction In Bilayer Hfo2/Sio2 Mos Devices, Richard G. Southwick Iii, Justin Reed, Christopher Buu, Ross Butler, Gennadi Bersuker, William B. Knowlton

William B. Knowlton

The gate leakage current of metal–oxide– semiconductors (MOSs) composed of hafnium oxide (HfO2) exhibits temperature dependence, which is usually attributed to the standard Poole–Frenkel (P–F) transport model. However, the reported magnitudes of the trap barrier height vary significantly. This paper explores the fundamental challenges associated with applying the P–F model to describe transport in HfO2/SiO2 bilayers in n/p MOS field-effect transistors composed of 3- and 5-nm HfO2 on 1.1-nm SiO2 dielectric stacks. The extracted P–F trap barrier height is shown to be dependent on several variables including ...


Influence Of Lignocellulose Fillers On Properties Natural Rubber Composites, Przemyslaw Rybiński, Bartłomiej Syrek, Marcin Masłowski, Justyna Miedzianowska, Krzysztof Strzelec, Witold Zukowski, Dariusz Bradło 2017 Cracow University of Technology

Influence Of Lignocellulose Fillers On Properties Natural Rubber Composites, Przemyslaw Rybiński, Bartłomiej Syrek, Marcin Masłowski, Justyna Miedzianowska, Krzysztof Strzelec, Witold Zukowski, Dariusz Bradło

Witold Zukowski

The present article presents unreported yet in the subject literature examinations of the effect of a lignocellulose filler obtained from an alkalized wheat straw treated with di-potassium phosphate on the properties of natural rubber composites. The thermal and mechanical properties as well as the fire hazard of the composites obtained were tested also in the presence of an additive flame-retardant compound (poly(ammonium phosphate)), exploiting the synergism of its action with pentaerythritol, antimony trioxide, aluminum hydroxide and zinc borate. Based on the results obtained by the methods of thermal and mechanical analyses, micro-calorimetry and cone calorimetry, it has been found ...


Control Of Columnar To Equiaxed Transition In Solidification Macrostructure Of Austenitic Stainless Steel Castings, Semen Naumovich Lekakh, Ronald J. O'Malley, Mark Emmendorfer, Brenton Hrebec 2017 Missouri University of Science and Technology

Control Of Columnar To Equiaxed Transition In Solidification Macrostructure Of Austenitic Stainless Steel Castings, Semen Naumovich Lekakh, Ronald J. O'Malley, Mark Emmendorfer, Brenton Hrebec

Ronald J. O'Malley

Solidification macrostructure is of great importance for the properties and the quality of castings made from austenitic grade stainless steels (ASS) because there are limited options to change as-cast macrostructure in the solid condition. A typical cast macrostructure of ASS has a fine surface chilled zone followed by an elongated dendrite zone, columnar to equiaxed transition (CET) zone, and centrally located equiaxed crystals. Several castings from ASS were produced to determine the effects of casting geometry, chilling, and grain refinement on CET. The transient thermal field in solidified heavy castings was simulated and used to determine an isotherm velocity (V ...


Computational Fluid Dynamics Study Of Molten Steel Flow Patterns And Particle-Wall Interactions Inside A Slide-Gate Nozzle By A Hybrid Turbulent Model, Mahdi Mohammadi-Ghaleni, Mohsen Asle Zaeem, Jeffrey D. Smith, Ronald J. O'Malley 2017 Missouri University of Science and Technology

Computational Fluid Dynamics Study Of Molten Steel Flow Patterns And Particle-Wall Interactions Inside A Slide-Gate Nozzle By A Hybrid Turbulent Model, Mahdi Mohammadi-Ghaleni, Mohsen Asle Zaeem, Jeffrey D. Smith, Ronald J. O'Malley

Ronald J. O'Malley

Melt flow patterns and turbulence inside a slide-gate throttled submerged entry nozzle (SEN) were studied using Detached–Eddy Simulation (DES) model, which is a combination of Reynolds–Averaged Navier–Stokes (RANS) and Large–Eddy Simulation (LES) models. The DES switching criterion between RANS and LES was investigated to closely reproduce the flow structures of low and high turbulence regions similar to RANS and LES simulations, respectively. The melt flow patterns inside the nozzle were determined by k–ε (a RANS model), LES, and DES turbulent models, and convergence studies were performed to ensure reliability of the results. Results showed that ...


Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh 2017 Missouri University of Science and Technology

Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh

Ronald J. O'Malley

The evolution of nonmetallic inclusions was examined for 4320 steel at an industrial steel foundry. The steel was followed from electric arc furnace melting through ladle refining to final casting. Timed sampling was performed at all stages of the process. Samples were analyzed using an automated SEM/EDS system. The overall evolution of oxide inclusions in terms of nucleation, growth, and flotation during liquid processing was studied using area fraction and average diameter. Chemical composition evolution was observed using a joint ternary plotting tool developed under this program. It was found that the use of zirconium as an addition for ...


Effect Of Zinc Galvanization On The Microstructure And Fracture Behavior Of Low And Medium Carbon Structural Steels, Ignatius C. Okafor, Ronald J. O'Malley, Kaushal R. Prayakarao, Heshmat A. Aglan 2017 Missouri University of Science and Technology

Effect Of Zinc Galvanization On The Microstructure And Fracture Behavior Of Low And Medium Carbon Structural Steels, Ignatius C. Okafor, Ronald J. O'Malley, Kaushal R. Prayakarao, Heshmat A. Aglan

Ronald J. O'Malley

Microstructure and fracture behavior of ASTM 572 Grade 65 steels used for wind tower applications have been studied. Steels of two carbon level chemistries designed for this grade were used in the study. Fracture toughness of the steels was studied using 3-point bend test on samples coated with zinc and not coated with zinc. Lower carbon steel showed higher resistance to fracture than medium carbon steel after zinc galvanization. SEM study suggests that zinc and zinc bath additives that migrated to crack tips are responsible for the loss in ductility. The phenomenon of Liquid Metal Embrittlement (LME) is suggested to ...


Development Of A Neural Network Simulator For Studying The Constitutive Behavior Of Structural Composite Materials, Hyuntae Na, Seung-Yub Lee, Ersan Ustundag, Sarah L. Ross, Halil Ceylan, Kasthurirangan Gopalakrishnan 2017 Iowa State University

Development Of A Neural Network Simulator For Studying The Constitutive Behavior Of Structural Composite Materials, Hyuntae Na, Seung-Yub Lee, Ersan Ustundag, Sarah L. Ross, Halil Ceylan, Kasthurirangan Gopalakrishnan

Halil Ceylan

This paper introduces a recent development and application of a noncommercial artificial neural network (ANN) simulator with graphical user interface (GUI) to assist in rapid data modeling and analysis in the engineering diffraction field. The real-time network training/simulation monitoring tool has been customized for the study of constitutive behavior of engineering materials, and it has improved data mining and forecasting capabilities of neural networks. This software has been used to train and simulate the finite element modeling (FEM) data for a fiber composite system, both forward and inverse. The forward neural network simulation precisely reduplicates FEM results several orders ...


Rigid Pavement Backcalculation Using Differential Evolution, Kasthurirangan Gopalakrishnan, Halil Ceylan 2017 Iowa State University

Rigid Pavement Backcalculation Using Differential Evolution, Kasthurirangan Gopalakrishnan, Halil Ceylan

Halil Ceylan

The backcalculation of pavement layer moduli from Falling Weight Deflectometer (FWD) measured surface deflections is a challenging task. It can also be formulated as a global optimization problem with the objective of finding the optimal pavement layer moduli values that minimize the error between measured and computed surface deflections. Over the years, several backcalculation methodologies have been developed including the use of soft computing techniques such as Neural Networks (NNs), Genetic Algorithms (GAs), etc. In this paper, Differential Evolution (DE), a stochastic parallel direct search evolution strategy optimization method is integrated with rapid surrogate mapping of Finite Element (FE) solutions ...


Effect Of Pcc Material Properties On Mepdg Jointed Plain Concrete Pavement (Jpcp) Performance Prediction, Halil Ceylan, Sunghwan Kim, Charles W. Schwartz, Rui Li, Kasthurirangan Gopalakrishnan 2017 Iowa State University

Effect Of Pcc Material Properties On Mepdg Jointed Plain Concrete Pavement (Jpcp) Performance Prediction, Halil Ceylan, Sunghwan Kim, Charles W. Schwartz, Rui Li, Kasthurirangan Gopalakrishnan

Halil Ceylan

This paper focuses on comprehensive sensitivity analyses of various rigid pavement scenarios. Jointed Plain Concrete Pavement (JPCP) sections designed for three traffic levels in each of five climate zones are evaluated in the sensitivity analyses. One-at-a-time (OAT) local sensitivity analysis was implemented using a design limit normalized sensitivity index (NSI) to provide both quantitative and qualitative sensitivity information. All portland cement concrete (PCC) material properties examined showed sensitivity to at least one rigid pavement performance measure. The highest ranked sensitive inputs for JPCP analysis include the PCC strength and stiffness properties and the curling and warping related properties. The findings ...


Corrosion Resistance Of A Sand Particle-Modified Enamel Coating Applied To Smooth Steel Bars, Fujian Tang, Genda Chen, Richard K. Brow, Michael L. Koenigstein 2017 Missouri University of Science and Technology

Corrosion Resistance Of A Sand Particle-Modified Enamel Coating Applied To Smooth Steel Bars, Fujian Tang, Genda Chen, Richard K. Brow, Michael L. Koenigstein

Genda Chen

The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The phase composition of the enamel coating and sand particles were determined with the X-ray diffraction (XRD) technique. The surface and cross-sectional morphologies of the sand particle-modified enamel coating were characterized using scanning electron microscopy (SEM). XRD tests revealed three phases of sand particles: SiO2, CaCO3 and MgCO3. SEM images demonstrated that the enamel coating wetted well ...


Gamma-Radiation Induced Corrosion Of Alloy 800, Mojtaba Momeni 2017 The University of Western Ontario

Gamma-Radiation Induced Corrosion Of Alloy 800, Mojtaba Momeni

Electronic Thesis and Dissertation Repository

This thesis presents a newly developed mechanism and predictive model for the corrosion of Alloy 800. The Fe-Cr-Ni Alloy (Incoloy 800) is mainly used for steam generator (SG) tubing in CANDU and PWR reactors and is a candidate material for the proposed Canadian Supercritical Water Reactor (SCWR) in which it will be exposed to extreme conditions of high radiation flux and large temperature gradients. The influence of gamma radiation and water chemistry conditions on the corrosion behaviour of Alloy 800 are studied in this work. Ionizing radiation creates reducing (•eaq, •H, •O2-) and oxidizing radiolysis (•OH, H2 ...


Study Design Of A Cluster-Randomized Controlled Trial To Evaluate A Large-Scale Distribution Of Cook Stoves And Water Filters In Western Province, Rwanda, Corey L. Nagel, Miles Kirby, Laura D. Zambrano, Ghislaine Rosa, Christina K. Barstow, Evan A. Thomas, Thomas Clasen 2017 Oregon Health & Science University

Study Design Of A Cluster-Randomized Controlled Trial To Evaluate A Large-Scale Distribution Of Cook Stoves And Water Filters In Western Province, Rwanda, Corey L. Nagel, Miles Kirby, Laura D. Zambrano, Ghislaine Rosa, Christina K. Barstow, Evan A. Thomas, Thomas Clasen

Evan A. Thomas

Background: In Rwanda, pneumonia and diarrhea are the first and second leading causes of death, respectively, among children under five. Household air pollution (HAP) resultant from cooking indoors with biomass fuels on traditional stoves is a significant risk factor for pneumonia, while consumption of contaminated drinking water is a primary cause of diarrheal disease. To date, there have been no largescale effectiveness trials of programmatic efforts to provide either improved cookstoves or household water filters at scale in a low-income country. In this paper we describe the design of a clusterrandomized trial to evaluate the impact of a national-level program ...


Development Of Novel N-Isopropylacrylamide (Nipaam) Based Hydrogels With Varying Content Of Chrysin Multiacrylate, Shuo Tang, Martha Floy, Rohit Bhandari, Thomas D. Dziubla, J. Zach Hilt 2017 University of Kentucky

Development Of Novel N-Isopropylacrylamide (Nipaam) Based Hydrogels With Varying Content Of Chrysin Multiacrylate, Shuo Tang, Martha Floy, Rohit Bhandari, Thomas D. Dziubla, J. Zach Hilt

Chemical and Materials Engineering Faculty Publications

A series of novel temperature responsive hydrogels were synthesized by free radical polymerization with varying content of chrysin multiacrylate (ChryMA). The goal was to study the impact of this novel polyphenolic-based multiacrylate on the properties of N-isopropylacrylamide (NIPAAm) hydrogels. The temperature responsive behavior of the copolymerized gels was characterized by swelling studies, and their lower critical solution temperature (LCST) was characterized through differential scanning calorimetry (DSC). It was shown that the incorporation of ChryMA decreased the swelling ratios of the hydrogels and shifted their LCSTs to a lower temperature. Gels with different ChryMA content showed different levels of response to ...


Development Of Nanomaterials For Lithium-Ion Batteries By Atomic Layer Deposition, Biqiong Wang 2017 The University of Western Ontario

Development Of Nanomaterials For Lithium-Ion Batteries By Atomic Layer Deposition, Biqiong Wang

Electronic Thesis and Dissertation Repository

Lithium ion batteries (LIBs) have been the dominant candidate in the field of energy storage. The ever-growing demand of high energy and power density, longer battery life, and more assured safety level has geared the development of LIBs towards all-solid-state batteries (ASSBs). The solid-state nature allows more flexibility in battery design and higher area capacity to be obtained within limited space. Moreover, replacing liquid electrolytes with solid-state electrolytes (SSEs) is a most effective approach to achieve safer battery system. In addition, ASSBs hold great promise in the actual fabrication of microbatteries for microelectronics. Therefore, a technique which can synthesize materials ...


Nucleation And Growth Kinetics For Intercalated Islands During Deposition On Layered Materials With Isolated Point-Like Surface Defects, Yong Han, Ann Lii-Rosales, Y. Zhou, C.-J. Wang, M. Kim, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel, James W. Evans 2017 Iowa State University and Ames Laboratory

Nucleation And Growth Kinetics For Intercalated Islands During Deposition On Layered Materials With Isolated Point-Like Surface Defects, Yong Han, Ann Lii-Rosales, Y. Zhou, C.-J. Wang, M. Kim, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel, James W. Evans

Ames Laboratory Accepted Manuscripts

Theory and stochastic lattice-gas modeling is developed for the formation of intercalated metal islands in the gallery between the top layer and the underlying layer at the surface of layered materials. Our model for this process involves deposition of atoms, some fraction of which then enter the gallery through well-separated point-like defects in the top layer. Subsequently, these atoms diffuse within the subsurface gallery leading to nucleation and growth of intercalated islands nearby the defect point source. For the case of a single point defect, continuum diffusion equation analysis provides insight into the nucleation kinetics. However, complementary tailored lattice-gas modeling ...


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