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Mechanical and Aerospace Engineering Faculty Research & Creative Works

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Articles 571 - 600 of 1144

Full-Text Articles in Mechanical Engineering

Thermographic Investigation Of Laser Metal Deposition, Sreekar Karnati, Todd E. Sparks, Frank W. Liou Aug 2014

Thermographic Investigation Of Laser Metal Deposition, Sreekar Karnati, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Primitive stages of studies on and with additive manufacturing techniques popularly involve thin wall geometry. In the current effort attempts were made to capture various thermal aspects during deposition of a thin wall geometry. The thermo-graphic data was captured using a FLIR A615 infrared camera. Post processing using edge detection algorithms and image processing techniques, the geometric and thermal aspects of meltpool and tail of the meltpool were obtained. The effect of geometry and power on shape of the meltpool and its tail were obtained. The depositions of SS 316 with varying power. These observations were discussed and analyzed in …

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Stereo Vision Based Hybrid Manufacturing Of Ti-6al-4v In Component Repair Process, Renwei Liu, Zhiyuang Wang, Todd E. Sparks, Frank W. Liou Aug 2014

Stereo Vision Based Hybrid Manufacturing Of Ti-6al-4v In Component Repair Process, Renwei Liu, Zhiyuang Wang, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Parts or products from high performance metal are very expensive, partly due to the processing complexities during manufacturing. Recent studies have indicated that hybrid processes of additive manufacturing and machining process can be used to repair titanium parts, thus extending the service life. In order to implement these methods automatically, it is necessary to obtain the spatial geometry information of component with defects to generate the tool path. The purpose of this paper is to summarize the research on hybrid manufacturing with stereo vision function which can be applied to the component repair process. Stereo vision is adopted to detect …

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Investigation Of Sparse-Build Rapid Tooling By Fused Deposition Modeling, Osman Iyibilgin, Ming-Chuan Leu, Gregory Taylor, H. Li, K. Chandrashekhara Aug 2014

Investigation Of Sparse-Build Rapid Tooling By Fused Deposition Modeling, Osman Iyibilgin, Ming-Chuan Leu, Gregory Taylor, H. Li, K. Chandrashekhara

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper describes the investigation of sparse-build tooling by Fused Deposition Modeling (FDM®) aimed at rapid tooling with reduction in the amount of material. Sparse-build test coupons having ULTEM as the material and varying air gap (sparse spacing), wall thickness, and cap thickness were fabricated using the sparse and sparse-double dense build styles of the Stratasys Fortus machine. The strengths and moduli of these coupons were measured in compression and flexure tests. The strength/mass ratio and modulus/mass ratio were compared among the various coupons, as well as with solid coupons, to investigate the effects of the two build styles and …

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In Vitro Assessment Of Laser Sintered Bioactive Glass Scaffolds With Different Pore Geometries, Krishna C. R. Kolan, Albin Thomas, Ming-Chuan Leu, Greg Hilmas Aug 2014

In Vitro Assessment Of Laser Sintered Bioactive Glass Scaffolds With Different Pore Geometries, Krishna C. R. Kolan, Albin Thomas, Ming-Chuan Leu, Greg Hilmas

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The pore geometry of bioactive glass scaffolds intended for use in bone repair or replacement is one of the most important parameters that could determine the rate of bone regeneration. The pore geometry would also affect the mechanical properties of the scaffolds and their rate of degradation. Scaffolds with five different architectures, having ~50% porosity, were fabricated with silicate (13–93) and borate (13–93B3) based bioactive glasses using a laser sintering process. An established, late-osteoblasts/early-osteocytes cell line was used to perform cell proliferation tests on the scaffolds. The results indicated that the cells proliferate significantly more on the scaffolds which mimic …

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Effects Of Local Ph On The Formation And Regulation Of Cristae Morphologies, Dong Hoon Song, Jonghyun Park, Martin A. Philbert, Ann Marie Sastry, Wei Lu Aug 2014

Effects Of Local Ph On The Formation And Regulation Of Cristae Morphologies, Dong Hoon Song, Jonghyun Park, Martin A. Philbert, Ann Marie Sastry, Wei Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Cristae, folded subcompartments of the inner mitochondrial membrane (IMM), have complex and dynamic morphologies. Since cristae are the major site of adenosine triphosphate synthesis, morphological changes of cristae have been studied in relation to functional states of mitochondria. In this sense, investigating the functional and structural significance of cristae may be critical for understanding progressive mitochondrial dysfunction. However, the detailed mechanisms of the formation and regulation of these cristae structures have not been fully elucidated. Among the hypotheses concerning the regulation of cristae morphologies, we exclusively investigate the effects of the local pH gradient on the cristae morphologies by using …

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Thermal Resistance At An Interface Between A Crystal And Its Melt, Zhi Liang, William J. Evans, Pawel Keblinski Jul 2014

Thermal Resistance At An Interface Between A Crystal And Its Melt, Zhi Liang, William J. Evans, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Non-Equilibrium Molecular Dynamics Simulations Are Used to Determine Interfacial Thermal Resistance (Kapitza Resistance) between a Crystal and its Melt for Three Materials Including Ar, H2O, and C8H 18 (Octane). the Simulation Results Show that the Kapitza Resistance at a Crystal-Melt Interface is Very Small and Thus Has a Negligible Effect on Thermal Transport Across the Crystal-Melt Interface. the Underlying Origins of This Behavior Are the Very Good Vibrational Property Match between the Two Materials Forming the Interface and Good Interfacial Bonding. the Result Also Indicates that the Commonly-Used Assumption that Temperature Profile is Continuous at the Crystal-Melt Interface is Valid …

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Curvature Induced Phase Stability Of An Intensely Heated Liquid, Kiran Sasikumar, Zhi Liang, David G. Cahill, Pawel Keblinski Jun 2014

Curvature Induced Phase Stability Of An Intensely Heated Liquid, Kiran Sasikumar, Zhi Liang, David G. Cahill, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We Use Non-Equilibrium Molecular Dynamics Simulations to Study the Heat Transfer Around Intensely Heated Solid Nanoparticles Immersed in a Model Lennard-Jones Fluid. We Focus Our Studies on the Role of the Nanoparticle Curvature on the Liquid Phase Stability under Steady-State Heating. for Small Nanoparticles We Observe a Stable Liquid Phase Near the Nanoparticle Surface, Which Can Be at a Temperature Well above the Boiling Point. Furthermore, for Particles with Radius Smaller Than a Critical Radius of 2 Nm We Do Not Observe Formation of Vapor Even above the Critical Temperature. Instead, We Report the Existence of a Stable Fluid Region …

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Flow-Controlling Header, David J. Bayless, Morgan Lefay Vis-Chiasson, Gregory G. Kremer, Ben J. Stuart Apr 2014

Flow-Controlling Header, David J. Bayless, Morgan Lefay Vis-Chiasson, Gregory G. Kremer, Ben J. Stuart

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An apparatus and method for holding a membrane, screen or other flexible planar body in tension, while providing a conduit for water or other liquid to flow to the membrane being held. The membrane extends from inside a manifold body that carries the liquid, and the manifold body supports the membrane at one edge while the membrane is pulled in tension. Liquid pressure builds up inside the manifold body, preferably by entering a pressure chamber at the top of the manifold body. At a feeding pressure in the pressure chamber the liquid is distributed to the membrane for microbe growth. …

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Bi-Harmonic Cantilever Design For Improved Measurement Sensitivity In Tapping-Mode Atomic Force Microscopy, M. Loganathan, Douglas A. Bristow Apr 2014

Bi-Harmonic Cantilever Design For Improved Measurement Sensitivity In Tapping-Mode Atomic Force Microscopy, M. Loganathan, Douglas A. Bristow

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

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Frequency-Limited Adaptive Control Of A Generic Transport Model In The Presence Of System Uncertainty And Losses In Control Effectiveness, Gerardo De La Torre, Tansel Yucelen, Wassim M. Haddad, Eric N. Johnson Feb 2014

Frequency-Limited Adaptive Control Of A Generic Transport Model In The Presence Of System Uncertainty And Losses In Control Effectiveness, Gerardo De La Torre, Tansel Yucelen, Wassim M. Haddad, Eric N. Johnson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

While adaptive control has been used in numerous applications to achieve system performance without excessive reliance on dynamical system models, the necessity of high-gain learning rates for safety-critical systems to achieve fast adaptation can be a serious limitation of most adaptive controllers. In order to address this problem, two novel adaptive control approaches developed recently aim to limit the bandwidth of the closed-loop adaptive control system in order to suppress the high-frequency content contained in the system error dynamics and adaptation algorithms. Specifically, this key feature of these frameworks allows for robust and fast adaptation by utilizing high-gain learning rates …

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The Origin Of Interferometric Effect Involving Surface Plasmon Polariton In Scattering Near-Field Scanning Optical Microscopy, Yan Li, Nan Zhou, Edward C. Kinzel, Xifeng Ren, Xianfan Xu Feb 2014

The Origin Of Interferometric Effect Involving Surface Plasmon Polariton In Scattering Near-Field Scanning Optical Microscopy, Yan Li, Nan Zhou, Edward C. Kinzel, Xifeng Ren, Xianfan Xu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Scattering near-field scanning optical microscopy (s-NSOM) has been developed to characterize optical near field with spatial resolution on the order of 10 nm. In this work we report investigation of the interferometric patterns commonly occurred in s-NSOM measurements. To reveal the origin of such interference patterns, a simple nano slit is used. Comparing the measured result with a simplified analytical model as well as full-field numerical simulations, it is shown that the interference pattern is predominantly formed by the in-plane component of incidence light and surface plasmon polariton (SPP) launched by the nano slit. This result helps to understand the …

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Femtosecond And Nanosecond Dual-Laser Optical Emission Spectroscopy Of Gas Mixtures, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai Feb 2014

Femtosecond And Nanosecond Dual-Laser Optical Emission Spectroscopy Of Gas Mixtures, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Method Employing an Integrated Femtosecond (Fs) and Nanosecond (Ns) Dual-Laser System Was Developed to Generate Plasma with Desired Radical Species from Gas Mixtures Via a Fs Laser Pulse and Then to Excite Selected Radical Species to Higher Electronic States using a Wavelength-Tunable Ns Laser Pulse. an Optical Spectrometer Was Used to Measure the Emission Spectra and Identify the Transition from the Excited Electronic State to the Ground State. the Proposed Technique Has Been Demonstrated for an N2-CO2 Mixture with Various Time Delays between the Two Fs and Ns Pulses. the Results Have Indicated that the Population of Selected Radical …

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Nonlinear Development And Secondary Instability Of Traveling Crossflow Vortices, Fei Li, Meelan M. Choudhari, Lian Duan, Chau-Lyan Chang Jan 2014

Nonlinear Development And Secondary Instability Of Traveling Crossflow Vortices, Fei Li, Meelan M. Choudhari, Lian Duan, Chau-Lyan Chang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Building upon the prior research targeting the laminar breakdown mechanisms associated with stationary crossflow instability over a swept-wing configuration, this paper investigates the secondary instability of traveling crossflow modes as an alternate scenario for transition. For the parameter range investigated herein, this alternate scenario is shown to be viable unless the initial amplitudes of the traveling crossflow instability are lower than those of the stationary modes by considerably more than one order of magnitude. The linear growth predictions based on the secondary instability theory are found to agree well with both parabolized stability equations and direct numerical simulation, and the …

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Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos Jan 2014

Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect.

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Active-Passive Networked Multiagent Systems, Tansel Yucelen, John Daniel Peterson Jan 2014

Active-Passive Networked Multiagent Systems, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper introduces an active-passive networked multiagent system framework, which consists of agents subject to exogenous inputs (active agents) and agents without any inputs (passive agents) and analyze its convergence using Lyapunov stability. Apart from the existing relevant literature, where either none of the agents are subject to exogenous inputs (i.e., average consensus problem) or all agents are subject to these inputs (i.e., dynamic average consensus problem), the key feature of our approach is that the states of all agents converge to the average of the exogenous inputs applied only to the active agents, where these inputs may or may …

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Thermomechanical Modeling Of Cone Sample Of Zrb2-Sic Ceramic Under Arc-Jet Conditions, Lokeswarappa R. Dharani, Jun Wei Jan 2014

Thermomechanical Modeling Of Cone Sample Of Zrb2-Sic Ceramic Under Arc-Jet Conditions, Lokeswarappa R. Dharani, Jun Wei

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effects of oxidation on mechanical behavior of a cone sample of ZrB2-SiC ceramic under arc-jet test conditions is studied by a finite element (FE) model. First a steady-state heat transfer FE method was employed to conduct the thermal analysis and obtain the temperature distribution in the inner body of the cone. Then, resulting temperature distribution is applied to the thermomechanical finite element analysis to calculate the thermal stress distribution in the cone body. Due to the mismatch of material properties between the bulk ZrB2-SiC and its new products after oxidation, the outer oxide layers constrain the thermal deformation of …

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Proper Orthogonal Decomposition Technique For Sub-Optimal Control Of Flexible Aircraft Wings Using Discrete Actuators, M. Kumar, S. N. Balakrishnan Jan 2014

Proper Orthogonal Decomposition Technique For Sub-Optimal Control Of Flexible Aircraft Wings Using Discrete Actuators, M. Kumar, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Distributed parameter systems are, generally, described by a set of partial differential equations. Control design of these systems is a very complex task as compared to that of the lumped parameter systems that are defined by a set of ordinary differential equations. In this paper, we present a stabilizing state-feedback control design approach for a class of second order system, where the system can be controlled by discrete actuators in the spatial domain. The control methodology is developed by combining the technique of 'Proper Orthogonal Decomposition' and Approximate Dynamic Programming. The Proper Orthogonal Decomposition technique is utilized to obtain a …

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Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models And Constrained Control Inputs, Mehrdad Pakmehr, Tansel Yucelen Jan 2014

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models And Constrained Control Inputs, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new state feedback model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting with constrained control inputs. A single Lyapunov matrix is computed for multiple linearization of the nonlinear closed loop gain scheduled reference system, using convex optimization tools. This approach guarantees stability of the closed loop gain scheduled reference model. Adaptive state feedback control architecture is then developed, and its stability is proven for the case with constrained control inputs. The resulting closed-loop system is shown to have bounded solutions with bounded tracking error, with the …

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Decentralized Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen Jan 2014

Decentralized Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control theoretic concepts for decentralized adaptive control of uncertain systems with gain scheduled reference model is developed. For each subsystem a single Lyapunov matrix is computed, using convex optimization tools, for multiple linearization near equilibrium and non-equilibrium points of the nonlinear closed loop gain scheduled reference subsystem. This approach guarantees stability of the closed loop gain scheduled reference model. Then, decentralized adaptive state feedback control architecture is developed and its stability is proved. Specifically, the resulting closed-loop system is shown to have bounded solutions with bounded tracking error for all the subsystems. Simulation results for two different models of a …

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Resilient Networked Multiagent Systems: A Distributed Adaptive Control Approachy, Gerardo De La Torre, Tansel Yucelen, John Daniel Peterson Jan 2014

Resilient Networked Multiagent Systems: A Distributed Adaptive Control Approachy, Gerardo De La Torre, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control algorithms of networked multiagent systems are generally computed distributivity without having a centralized entity monitoring the activity of agents; and therefore, adverse events such as attacks to the communication network and/or failure of agent-wise components can easily result in system instability and prohibit the accomplishment of system-level objectives. This paper studies resilient coordination of networked multiagent systems in the presence of misbehaving agents, i.e., agents that are subject to such adverse events. In particular, we consider a class of adverse conditions consisting of exogenous disturbances and interagent uncertainties and present a distributed adaptive control architecture to retrieve the nominal …

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Decomposition Of Ionic Liquid Ferrofluids For Multi-Mode Spacecraft Propulsion, Steven P. Berg, Brynne Coleman, Joshua L. Rovey Jan 2014

Decomposition Of Ionic Liquid Ferrofluids For Multi-Mode Spacecraft Propulsion, Steven P. Berg, Brynne Coleman, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ionic liquid ferrofluids based on mixtures of [Emim][EtSO4] and [Bmim][NO3] fuels and hydroxylammonium nitrate oxidizer were synthesized by adding iron oxide nanoparticles. The resulting propellants were then tested for decomposition capability. Spot plate testing indicated that the temperature required to initiate rapid decomposition dropped from 115 °C to 75 °C with a 30% by weight addition of iron oxide for the [Bmim][NO3] propellant. Adding more iron oxide resulted in an increase in onset temperature. The [Emim][EtSO4] propellant had a much lower decrease in onset temperature, bottoming out at 90 °C. Batch reactor tests under vacuum showed that 10% addition of …

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Reference Control Architecture In The Presence Of Measurement Noise And Actuator Dynamics, Gerardo De La Torre, Tansel Yucelen, Eric Johnson Jan 2014

Reference Control Architecture In The Presence Of Measurement Noise And Actuator Dynamics, Gerardo De La Torre, Tansel Yucelen, Eric Johnson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper the command governor-based model reference control architecture is developed and analyzed for uncertain dynamical systems in the presence measurement noise and actuator dynamics. Specifically, the command governor is a dynamical system that adjusts the trajectory of a given command in order to enable an uncertain system to be able to follow an ideal reference system capturing a desired closed-loop dynamical system behavior both in transient-time and steady-state. In this paper, we present modifications to the original command governor approach in order to increase its robustness properties against measurement noise and actuator dynamics. In particular, the modified architecture …

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Control-Oriented Modeling For Open-Cathode Fuel Cell Systems, Joseph Ishaku, Nima Lotfi, Hesam Zomorodi, Robert G. Landers Jan 2014

Control-Oriented Modeling For Open-Cathode Fuel Cell Systems, Joseph Ishaku, Nima Lotfi, Hesam Zomorodi, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Due to numerous advantages of Polymer Electrolyte Fuel Cells (PEMFCs), they are becoming the mainstream fuel cell of choice for different applications. Open-cathode PEMFCs, in particular, are gaining increased popularity in low to medium power applications due to their simple structure and low parasitic losses. However, in order to achieve safe operation, increased durability and optimal performance, advanced control algorithms, which typically require control-oriented models, need to be implemented on open-cathode fuel cell systems. The open-cathode fuel cell system includes the fuel cell stack and all of the auxiliary components that are vital for its operation. In this paper, control-oriented …

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Verifiable Frequency-Limited Adaptive Control Performance Based On Linear Matrix Inequalities, Mario Luca Fravolini, Tansel Yucelen, Daniel Wagner, Ali Albattat, Paolo Valigi Jan 2014

Verifiable Frequency-Limited Adaptive Control Performance Based On Linear Matrix Inequalities, Mario Luca Fravolini, Tansel Yucelen, Daniel Wagner, Ali Albattat, Paolo Valigi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive controllers are often criticized for the lack of clear and easy verification procedures that relate design parameters to time domain performance especially during transients. For this reason, it is a challenge to rigorously certify existing adaptive control algorithms. To that end, we propose a validation framework where stability and performance requirements are formulated in terms of Linear Matrix Inequalities. This brings the advantage that adaptive controller design and verification can be analyzed and optimized via the solution of a convex optimization whose objective is to guarantee the evolution of the error components within an a-priori specified domain. This approach …

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Radical Species Generation And Their Lifetime Extension By A Femtosecond And Nanosecond Dual-Laser System, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai Jan 2014

Radical Species Generation And Their Lifetime Extension By A Femtosecond And Nanosecond Dual-Laser System, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

For Many Material Processes, Desired Radical Species at Excited States Are Produced Which Interact with a Given Substrate for a Certain Period of Time Allowing Chemical Reactions between Them to Occur and Complete. Hence, It is Important to Maintain the Population of the Excited Radical Species for an Extended Period of Time, I.e., their Lifetime, Which is Defined as the Time for Emission Intensity to Decay to 1/e of the Initial Intensity. in This Study, a Femtosecond-Nanosecond (Fs-Ns) Dual-Laser System Was Employed to Generate Desired Radical Species Via the Fs Laser And, Then, to Extend the Lifetime of the Radical …

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Association Between Vitamin D Receptor Gene Polymorphisms (Fok1 And Bsm1) And Osteoporosis: A Systematic Review, Zahra Mohammadi, Fateme Fayyazbakhsh, Mehdi Ebrahimi, Mahsa M. Amoli, Patricia Khashayar, Mahboubeh Dini, Reza Nezam Zadeh, Abbasali Keshtkar, Hamid Reza Barikani Jan 2014

Association Between Vitamin D Receptor Gene Polymorphisms (Fok1 And Bsm1) And Osteoporosis: A Systematic Review, Zahra Mohammadi, Fateme Fayyazbakhsh, Mehdi Ebrahimi, Mahsa M. Amoli, Patricia Khashayar, Mahboubeh Dini, Reza Nezam Zadeh, Abbasali Keshtkar, Hamid Reza Barikani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Osteoporosis is a Health Concern Characterized by Reduced Bone Mineral Density (BMD) and Increased Risk of Fragility Fractures. Many Studies Have Investigated the Association between Genetic Variants and Osteoporosis. Polymorphism and Allelic Variations in the Vitamin D Receptor Gene (VDR) Have Been Found to Be Associated with Bone Mineral Density. However, Many Studies Have Not Been Able to Find This Association. Literature Review Was Conducted in Several Databases, Including MEDLINE/Pubmed, Scopus, EMBASE, Ebsco, Science Citation Index Expanded, Ovid, Google Scholar, Iran Medex, Magiran and Scientific Information Database (SID) for Papers Published between 2000 and 2013 Describing the Association between Fok1 …

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The Effect Of Different Rollover Conditions Of The Vibrator On Human Injury, Qin Li, Hang Liu, Zhiqiang Huang, Yaping Ding, Xiaoping Du Jan 2014

The Effect Of Different Rollover Conditions Of The Vibrator On Human Injury, Qin Li, Hang Liu, Zhiqiang Huang, Yaping Ding, Xiaoping Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Vibrator, as a crucial vehicle of oil and gas exploration, is challenged by the complex terrains. The probability of rollover accident is therefore high in bumpy terrain in which the drivers' life is seriously threatened. Finite element numerical analysis was used to study the injury of the driver's head, neck and chest in the rollover accidents of domestic KZ-28 type vibrator on different conditions. The injuries of three parts were evaluated based on the human injury criteria. Driver's safety on different rollover conditions was comparatively analyzed. The results indicated that the injury degree of human head caused by vibrator rollover …

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Assessment Of Multi-Mode Spacecraft Micropropulsion Systems, Steven P. Berg, Joshua L. Rovey Jan 2014

Assessment Of Multi-Mode Spacecraft Micropropulsion Systems, Steven P. Berg, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multi-mode spacecraft micro propulsion systems which include a high-thrust chemical mode and high-specific impulse electric mode are assessed with specific reference to cube sat-sized satellite applications. Both cold gas Freon-14 propellant and ionic liquid chemical monopropellant modes were investigated alongside pulsed plasma, electrospray, and helicon electric thruster modes. Systems involving chemical monopropellants have the highest payload mass fractions for a reference mission of a 500 m/s delta-V and 6U sized cube sat for electric propulsion usage below 55% of total delta-V. For higher electric propulsion usage, cold gas thrusters delivered a higher payload mass fraction due to lower system inert …

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Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen Jan 2014

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting. Specifically, adaptive state feedback for output tracking control problem of MIMO nonlinear systems is studied and gain scheduled reference model system is used for generating desired state trajectories. Using convex optimization tools, a single Lyapunov matrix is computed for multiple linearization's near equilibrium and non-equilibrium points of the nonlinear closed loop gain scheduled reference system. This approach guarantees stability of the closed loop gain scheduled system. Adaptive state feedback control scheme is then developed, and its …

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Adaptive Architectures For Distributed Control Of Modular Systems, Tansel Yucelen, Jeff S. Shamma Jan 2014

Adaptive Architectures For Distributed Control Of Modular Systems, Tansel Yucelen, Jeff S. Shamma

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We consider the distributed control of large-scale modular systems, i.e., systems consist of physically interconnected (and possibly heterogeneous) submodules that use local information to achieve a given set of global objectives. A graph-theoretic approach is used to model the unknown physical interactions between submodules and utilize an adaptive control algorithm to learn and cancel the effect of such interactions as well as the submodule-level modeling uncertainties asymptotically by allowing submodules to locally communicate with each other through the graph. The key feature of our framework is to bound the mismatch error between the actual and desired closed-loop modular system performance …

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