Engineering Commons^™

Scalable Multiagent Planning Using Probabilistic Inference, Akshat Kumar, Shlomo Zilberstein, Marc Toussaint

Research Collection School Of Computing and Information Systems

Multiagent planning has seen much progress with the development of formal models such as Dec-POMDPs. However, the complexity of these models -- NEXP-Complete even for two agents -- has limited scalability. We identify certain mild conditions that are sufficient to make multiagent planning amenable to a scalable approximation w.r.t. the number of agents. This is achieved by constructing a graphical model in which likelihood maximization is equivalent to plan optimization. Using the Expectation-Maximization framework for likelihood maximization, we show that the necessary inference can be decomposed into processes that often involve a small subset of agents, thereby facilitating scalability. We …

Message-Passing Algorithms For Quadratic Programming Formulations Of Map Estimation, Akshat Kumar, Shlomo Zilberstein

Research Collection School Of Computing and Information Systems

Computing maximum a posteriori (MAP) estimation in graphical models is an important inference problem with many applications. We present message-passing algorithms for quadratic programming (QP) formulations of MAP estimation for pairwise Markov random fields. In particular, we use the concave-convex procedure (CCCP) to obtain a locally optimal algorithm for the non-convex QP formulation. A similar technique is used to derive a globally convergent algorithm for the convex QP relaxation of MAP. We also show that a recently developed expectation-maximization (EM) algorithm for the QP formulation of MAP can be derived from the CCCP perspective. Experiments on synthetic and real-world problems …

Corrosion Prevention Of Rebar In Concrete Due To Chloride, Y Srimahajariyaphong, S Niltawach

Journal of Metals, Materials and Minerals

In coastal and brackish areas, black rebar in concrete structures suffers from chloride corrosion which leads to spalling of the concrete. The Half Cell Potential Measurement technique has been applied to study the corrosion behavior of both black and galvanized deformed rebar in different concretes. Additives in the concretes vary from pozzolan, calcium nitrite, to pozzolan plus calcium nitrite. Rebar which has higher half cell potential possesses better corrosion resistance. It has been found that concrete cover thickness has no significant effect on the half cell potential of either rebar; that for both types of rebar, the half cell potential …

Separation Of Lycopene/Solvent Mixture By Chitosan Membranes, P Yodjun, K Soontarapa, C Eamchotchawalit

Journal of Metals, Materials and Minerals

Acetone in view of lower toxicity could be used as extracting solvent of lycopene in tomato paste instead of hexane. The studied chitosan membranes were uncrosslinked and crosslinked types. It was found that the membrane morphology could be changed from porous to dense structure by increasing evaporation temperature or time or by crosslinking. They showed hydrophilicity but not preferred to both acetone and lycopene. The lycopene/acetone mixture could be separated by using water swollen chitosan membrane in pervaporation process. It was found that all studied membranes; i.e., both uncrosslinked and ionically crosslinked membranes prepared at 40 to 60C for 2 …

Steel Angle Section Members Under Combined Axial Load And Unsymmetric Bending, Maheshchandra Rajasekharan Phanibhushan

Civil & Environmental Engineering Theses & Dissertations

This thesis presents the outcome of an investigation into the experimental and theoretical behavior of steel angle section members under combined axial load and unsymmetric bending. Tests are conducted on a series of six angle section members provided with biaxial pinned-end boundaries about the cross-sectional non-principal axes. The end bending moments and axial load are applied in a quasi-static manner until the member load-carrying capacity is reached. The experimental load-deflection and load-strain curves are recorded. The theoretical analysis is based on a system of both elastic as well as materially nonlinear differential equations. The equations were solved using an iterative …

Improving The Efficiency Of Organic Solar Cells By Varying The Material Concentration In The Photoactive Layer, Kevin Anthony Latimer

Electrical & Computer Engineering Theses & Dissertations

Polymer-fullerene bulk heterojunction solar cells have been a rapidly improving technology over the past decade. To further improve the relatively low energy conversion efficiencies of these solar cells, several modifications need to be made to the overall device structure. Emerging technologies include cells that are fabricated with interfacial layers to facilitate charge transport, and tandem structures are being introduced to harness the absorption spectrum of polymers with varying bandgap energies.

When new structures are implemented, each layer of the cell must be optimized in order for the entire device to function efficiently. The most volatile layer of these devices is …

Flexural Behavior Of Interlocking Compressed Earth Block Shear Walls Subjected To In-Plane Loading, Bradley James Stirling

Master's Theses

This thesis investigates the flexural behavior of interlocking compressed earth block (ICEB) shear walls. In-plane cyclic tests were conducted to evaluate the performance of three flexure dominant large scale ICEB specimens: a slim wall with a 2:1 height to width aspect ratio, a flanged wall, and a wall with an opening at the center. Following the experimental investigation, two types of analyses were conducted for calculating the ultimate strength of flexure dominant ICEB walls: a nonlinear static analysis model assuming lumped plasticity and a plastic analysis model. In addition, incremental dynamic analysis was conducted to address the seismic performance of …

Boundary Layer Measurements Related To Wind Tunnel Testing Of Riblets, Emrah Cinar

Mechanical & Aerospace Engineering Theses & Dissertations

With fuel economy being a significant factor in today's world of aviation, aircraft manufacturers have been looking into ways to decrease drag to save fuel. Drag reduction using riblets on wing and fuselage surfaces is . an area that has been studied extensively for the last two decades. In preparation for a larger project which will use several methods to simulate this phenomena, small scale research had to be done to find ways to generate similar conditions on scaled models in a low speed wind tunnel and examine boundary layer behavior.

In this project, boundary layer measurement techniques, such as …

Interface Circuit For A Multiple-Beam Tuning-Fork Gyroscope With High Quality Factors, Ren Wang

Mechanical & Aerospace Engineering Theses & Dissertations

This research work presents the design, theoretical analysis, fabrication, interface electronics, and experimental results of a Silicon-On-Insulator (SOI) based Multiple-Beam Tuning-Fork Gyroscope (MB-TFG). Based on a numerical model of Thermo-Elastic Damping (TED), a Multiple-Beam Tuning-Fork Structure (MB-TFS) is designed with high Quality factors (Qs) in its two operation modes. A comprehensive theoretical analysis of the MB-TFG design is conducted to relate the design parameters to its operation parameters and further performance parameters. In conjunction with a mask that defines the device through trenches to alleviate severe fabrication effect on anchor loss, a simple one-mask fabrication process is employed to implement …

A Methodology To Repair Or Deorbit Leo Satellite Constellations, Goksel Gurgenburan

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, mitigation of space debris is addressed by examining an approach for repair or de-orbit of a specific population of non-functional Low Earth Orbit (LEO) satellites. Basic orbital mechanics propagation of the orbits was used as the process for computing a solution to the time and intercept position for the targeted satellites. Optimal orbital maneuvers to reach the target satellites from a pre-established orbit were also considered. In this way minimum ΔV budget, rendezvous time and mass budgets were managed. The Clohessy-Wiltshire Equations and two-impulsive rendezvous maneuvers were used to determine the orbital path of a chase satellite …

A Variable Acceleration Calibration System, Thomas H. Johnson

Mechanical & Aerospace Engineering Theses & Dissertations

A variable acceleration calibration system that applies loads using gravitational and centripetal acceleration serves as an alternative, efficient and cost effective method for calibrating internal wind tunnel force balances. Two proof-of-concept variable acceleration calibration systems are designed, fabricated and tested. The NASA UT-36 force balance served as the test balance for the calibration experiments. The variable acceleration calibration systems are shown to be capable of performing three component calibration experiments with an approximate applied load error on the order of 1% of the full scale calibration loads. Sources of error are indentified using experimental design methods and a propagation of …

Novel Microelectromechanical Systems Image Reversal Fabrication Process Based On Robust Su-8 Masking Layers, Scott A. Ostrow Ii, Ronald A. Coutu Jr.

Electrical and Computer Engineering Faculty Research and Publications

This paper discusses a novel fabrication process that uses a combination of negative and positive photoresists with positive tone photomasks, resulting in masking layers suitable for bulk micromachining high-aspect ratio microelectromechanical systems (MEMS) devices. MicroChem's negative photoresist Nano™ SU-8 and Clariant's image reversal photoresist AZ 5214E are utilized, along with a barrier layer, to effectively convert a positive photomask into a negative image. This technique utilizes standard photolithography chemicals, equipment, and processes, and opens the door for creating complementary MEMS structures without added fabrication delay and cost. Furthermore, the SU-8 masking layer is robust enough to withstand aggressive etch chemistries …

Jet Propellant 8 Versus Alternative Jet Fuels, Peter Feng, Wayne C. Kinsel, Alfred E. Thal Jr., Charles A. Bleckmann

Faculty Publications

The Air Force is the largest user of jet fuel in the Department of Defense DOD, consuming 2.4 billion gallons per year. In light of environmental impacts associated with using nonrenewable fuel sources and national security concerns regarding dependency on foreign oil, it is no surprise that the United States is paying more attention to alternative fuels. Both DOD and Air Force energy strategies address the need to develop and produce such fuels. The DOD has made a commitment to energy security, establishing an energy initiative that strives to modernize infrastructure, increase utility and energy conservation, enhance demand reduction, and …

Achieving The Air Force’S Energy Vision, Frederick G. Harmon, Richard D. Branam, Doral E. Sandlin

Faculty Publications

The US Air Force is the largest consumer of energy in the federal government, spending 9 billion in 2008 to fuel aircraft and ground vehicles as well as provide energy to installations.¹ In that same year, the Air Force s fuel bill of 7 billion amounted to more than half of the US government s total fuel cost.² Because of the critical and central role that energy plays in completion of the Air Force’s mission, the secretary of the Air Force has developed an Air Force energy plan supported by three pillars Reduce Demand, Increase Supply, and Culture …

X-Hale: Designing The Atmospheric Surveillance Platforms Of The Future, Christopher M. Shearer

Faculty Publications

Imagine the benefits that battlefield commanders or intelligence analysts could derive from an airborne surveillance platform that would carry a 500-pound payload, operate above the range of small arms fire, remain on station for weeks or even years, cost much less than a satellite, and relocate around the globe to a new region of interest within a couple of weeks. Realizing this concept, known as a high-altitude, long-endurance HALE aircraft, is a 10-to-15-year goal of researchers at the Air Force Institute of Technology AFIT. In order to reach this goal, those researchers are following a developmental path similar to the …

Precision Position, Navigation, And Timing Without The Global Positioning System, Kenneth A. Fisher, John F. Raquet

Faculty Publications

The NAVSTAR Global Positioning System GPS has revolutionized modern warfare. Since 2005 almost all US precision-guided munitions have used GPS targeting data. Consequently, weapons delivery systems are able to strike enemy targets with precision, often resulting in little or no collateral damage. Furthermore, nearly all military assets, including aircraft, tanks, ships, missiles, mortar rounds, cargo boxes, and dismounted Soldiers rely on the accurate position determination that GPS provides. For military users of this system, two main limitations emerge. First, the system relies on line of sight that is, the satellites must be in view of the receiver s antenna so …

Unintended Consequences: Potential Downsides Of The Air Force's Conversion To Biofuels, Mark N. Goltz, Charles A. Bleckmann, Charles M. Mackay, Khai Vuong, Jerrod P. Mccomb

Faculty Publications

The desire to reduce US dependence on foreign energy, ongoing environmental concerns, and the rising cost of petroleum have sparked significant development of greener alternative and renewable energy sources such as alcohol-based biofuels. To address these issues, the Department of Defense DOD has moved to diminish its reliance on petroleum for fueling aircraft and ground equipment. The US Air Force, in alignment with DOD objectives, has initiated several goals for reducing its use of energy: (1) decrease the use of petroleum-based fuel by 2 percent annually for the vehicle fleet, (2) increase the use of alternative fuel in motor vehicles …

Using Nanotechnology To Detect Nerve Agents, Mark N. Goltz, Dong-Shik Kim, Leeann Racz

Faculty Publications

Nanotechnology has opened a wide range of opportunities having potential impacts in areas as diverse as medicine and consumer products. In collaboration with researchers at the University of Toledo UT, Air Force Institute of Technology AFIT scientists are exploring the possibility of using a nanoscale organic matrix to detect organophosphate OP nerve agents. Current techniques for detecting OP compounds are expensive and time consuming. Developing a nanoscale organic matrix sensor would allow for direct, real-time sensing under field conditions. This article describes the science behind such a sensor and its possible applications. High-performance sensors are needed to protect Soldiers and …

Aerospike Rockets For Increased Space Launch Capability, Carl R. Hartsfield, Richard D. Branam, Joshua N. Hall, Joseph R. Simmons Iii

Faculty Publications

The US Department of Defense (DOD) increasingly depends on space assets for everyday operations. Precision navigation; communications; and intelligence, surveillance, and reconnaissance satellites are highly leveraged space assets. The launch vehicles that place these satellites in orbit are a major limitation of current space systems. If higher-performing launch vehicles were available, many satellites could accommodate additional capabilities, whether in terms of more sensor channels, types of payloads, electrical power, or propellant for orbital maneuvering and station keeping.

A Simple Ultrasensitive Displacement Sensor Based On A High Bend Loss Single-Mode Fibre And A Ratiometric Measurement System, Pengfei Wang, Gilberto Brambilla, Yuliya Semenova, Qiang Wu, Gerald Farrell

Articles

An all-fibre displacement sensor with a simple configuration and capable of monitoring sub-50 nm displacements is proposed and investigated experimentally. The proposed fibre displacement sensor consists of a half-loop structure of bare high bend loss single-mode fibre 1060XP and a ratiometric power interrogation system. By measuring the change in transmission ratio in the ratiometric system, a change in displacement can be measured. The displacement sensor is sensitive to temperature and an experimental investigation of this sensitivity is presented. It is found that the peak shift response has a linear variation with temperature; therefore, temperature dependence can be mitigated by a …

Self-Crack Closing Ability Of Mortar With Different Additives, D Jaroenratanapirom, R Sahamitmongkol

Journal of Metals, Materials and Minerals

Self-crack closing ability of cementitious materials has been studied in various aspects. However, most studies focus mainly on the cementitious material with only cement as a binder (without mineral additives), although many additives are commonly used at present. This research thus aims to investigate the effect of additives on this self-crack closing ability by observing and measuring crack width on the mortar specimens. Cracks were created on mortar specimens by splitting method at the age of 3 and 28 days. As most reports show that the best self-crack closing performance was achieved when a plenty of water was supplied, the …

Determination Of Forming Limit Stress Diagram For Formability Prediction Of Spce 270 Steel Sheet, S Panich, V Uthaisangsuk, J Juntaratin, S Suranuntchai

Journal of Metals, Materials and Minerals

The aim of this research is to apply numerical Finite Element Method (FEM) for determining Forming Limit Stress Diagram (FLSD) of sheet steel of grade SPCE 270. As a failure criterion for formability prediction in sheet metal forming process, the conventional Forming Limit Diagram (FLD) is often used. The FLD is a strain based criterion, by which the principal strains at failure are evaluated. Many investigations showed that the FLD is dependent on forming history and strain path. However, the stress based criterion does not confirm this dependency. This criterion is more robust against any changes in the strain path …

The Change Of Surface Alloy Compositions And Corrosion Behavior After Wedm Machining Of Commercially Pure Titanium (Grade 4) And Ti-6al-4v (Grade 5), K Sriprasertying, S Rhaiphu

Journal of Metals, Materials and Minerals

Nowadays, titanium and its alloys are widely used in medical applications because of excellent corrosion resistance and a high strength-to-weight ratio. Nevertheless, titanium and its alloys are classified as difficult-to-machine metals by conventional machining methods. Therefore, unconventional machining processes are recommended. Wire-electrical discharge machining (WEDM) has become an important non-traditional machining process, as it provides an effective solution for machining components made from difficult-to-machine metals. However, WEDM could damage the surface layer and have an effect on the biocompatibility properties. This research was focused on the effect of WEDM on grade 4 commercially pure titanium and Ti-6Al-4V (Grade 5) after …

Modification Of Montmorillonite With A Cationic Softener For Finishing Cotton Fabric With Hand Builder Performance, S Kittinaovarat, N Jiratumnukul, N Koolpreechanan

Journal of Metals, Materials and Minerals

Montmorillonite (Mont) was modified by cationic exchange with the cationic softener TEGO 28 (Di-Palm carboxyethyl hydroxyethyl methyl ammonium methosulfate). XRD analysis suggested that intercalation occurred in the modified Mont (mMont). Softening finishing solutions composed of pure TEGO 28 with and without mMont were treated on cotton fabrics by the pad-dry method and then evaluated for stiffness, whiteness, tear strength and thermal stability. TEGO 28 treatment alone increased the stiffness property of the finished fabrics, and this was increased further by the co-inclusion of mMont at 3 and 5% (w/v), but higher or lower mMont concentrations led to a marked and …

Chitosan And Trimethyl Chitosan Particles As Oral Vaccine Delivery Systems: Comparison Of The Potential To Initiate Immune Responses, S Boontha, H Ej Unginger, N Waranuch, A Polnok, T Pitaksuteepong

Journal of Metals, Materials and Minerals

In this study, particles having low MW (Chi-L), high MW (Chi-H) and their respective trimethyl chitosan (TMC) with a degree of quaternization (DQ) of about 40% (TMC-L-40 and TMC-H-40), and prepared by using chitosan, were used to compare their potentials for provoking immune responses to ovalbumin (OVA) following oral administration. The results showed that the Chi-L particles gave higher serum immunoglobulin G (IgG) responses to OVA than those induced with Chi-H, TMC-L-40 and TMC-H-40 particles. However, Chi-L and Chi-H particles gave similar secretory immunoglobulin A (sIgA) to OVA, and sIgA titers obtained from mice immunized with OVA-loaded TMC were negligible. …

Purification Of An Industrial Aluminum Alloy By Melt Stirring During Ohno Continuous Casting Process, S Fashu, L Jianguo, H Q. Dan

Journal of Metals, Materials and Minerals

With the purpose of upgrading the purity of a dilute industrial aluminum alloy during Ohno Continuous Casting (OCC) process through the use of forced melt stirring; the critical stirring intensity required under a casting speed of 2 mm/min was numerically determined. The determined critical stirring intensity induces convective velocity magnitudes into the melt which are effective in transporting solutes from the solute boundary layer into the bulk melt. It was found that, with adequate melt stirring, production of substantially long and high purity ingots during OCC is possible before their purity diminishes to lower than the initial alloy purity.

Design And Construction Of Water Atomizer For Making Metal Powder, S Yenwiset, T Yenwiset

Journal of Metals, Materials and Minerals

Water Atomization for metal powder is an appropriate method for producing metal powder from different kinds of metal. Typically, a water atomizing machine is designed with a molten metal spraying chamber in a vertical or horizontal orientation depending on a nozzle design, a molten metal spraying chamber and related components. The main variables influencing the working condition of the water atomization process, which affect sizes, shapes and distribution of metal powder particles, are water pressure, water flow rate, a temperature higher than melting point of liquid metal and flow rate of liquid metal. The water atomizing machine in the study …

Effect Of Postweld Heat Treatment On Microstructures And Hardness Of Tig Weldment Between P22 And P91 Steels With Inconel 625 Filler Metal, N Tammasophon, W Homhrajai, G Lothongkum

Journal of Metals, Materials and Minerals

This research aims at searching for the optimal postweld heat treatment condition of the TIG weld joint between P22 (2.25Cr) and P91 (9Cr) steels using Inconel 625 as filler metal. The postweld heat treatment at 750C for 2, 4 and 6 hours was applied in order to reach the proper microstructure and hardness for high performance in mechanical properties at elevated temperatures. It is recommended that postweld heat treatment at 750C for 2 hours is the proper condition to reduce the hardness of heat affected zone (HAZ) of P91 steel.

Applying Computer Simulation In Improving Heat Treating Condition Of Thin High-Carbon Steel Parts, T Korad, M Polboon, N Chumchery, J Pearce

Journal of Metals, Materials and Minerals

The study was carried out using COSMOSFlowWorks to predict heat treatment conditions for AISI 1085 high-carbon steel sheet that is used to produce automotive parts that require wear resistance and stiffness resulting from controlled moderately high hardness levels. To achieve such properties, flat high-carbon steel parts need to be hardened to produce acicular matrix structures, and the most suitable heat treatment process to harden thin parts without distortion is austempering. In producing hard and stiff thin section parts in this company study the austempering process was performed by soaking at 830C and then quenching in a NaCl salt bath at …

Effect Of Nitrogen Partial Pressure On Characteristic And Mechanical Properties Of Hard Coating Tialn Film, C Chokwatvikul, S Larpkiattaworn, S Surinphong, C Busabok, P Termsuksawad

Journal of Metals, Materials and Minerals

(Ti,Al)N coating has been serving for the industry as cutting and forming tools. Compared with TiN film, TiAlN film significantly increases tool lifetime. Therefore, it reduces machine downtime and increases productivity. In this work, (Ti,Al)N film was deposited on cold-work tool steel (SKD 11) using PVD cathodic arc system. The sintered Ti-Al target with composition of (at%) 50 Ti and 50 Al was used as a cathode. The deposition bias voltage, bias arc current and deposition time were set at 100 V, 70 A and 90 minutes, respectively. Nitrogen gas was purged into the system with the applied pressure of …