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Articles 1 - 9 of 9

Full-Text Articles in Mechanical Engineering

Effect Of Interfacial Mobility On Flexural Strength And Fracture Toughness Of Glass/Epoxy Laminates, T. W. H. Wang, Frank D. Blum, Lokeswarappa R. Dharani Oct 1999

Effect Of Interfacial Mobility On Flexural Strength And Fracture Toughness Of Glass/Epoxy Laminates, T. W. H. Wang, Frank D. Blum, Lokeswarappa R. Dharani

Chemistry Faculty Research & Creative Works

Mechanical testing and surface fractography were used to characterize the fracture of E-glass fiber reinforced epoxy composites as a function of the silane coupling agent used. gamma-Aminopropyltriethoxysilane (APS) and delta-aminobutyltriethoxysilane (ABS) were used because these have been shown to have different interfacial mobilities at multilayer coverage. The values of the properties studied generally increased from untreated c, as determined from a Mode I translaminar fracture toughness tests, for the untreated composites (10.5 ± 0.4 kJ/m2) was lower than that for the ABS-treated composites (14.3 ± 2.1 kJ/m2) which was lower than that for the APS-treated composites ...


Galnnas Resonant-Cavity-Enhanced Photodetector Operating At 1.3 Μm, J. B. Heroux, Xiaodong Yang, W. I. Wang Sep 1999

Galnnas Resonant-Cavity-Enhanced Photodetector Operating At 1.3 Μm, J. B. Heroux, Xiaodong Yang, W. I. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We demonstrate a GaAs-based p-i-n resonant-cavity-enhanced (RCE) GalnNAs photodetector operating near 1.3 µm. The device design was optimized using a transfer matrix method and experimental absorption spectra obtained from p-i-n structures grown without a resonant cavity. The RCE photodetector was fabricated in a single growth step by using GaAs/AlAs distributed Bragg reflectors for the top and bottom mirrors. A 72% quantum efficiency was obtained with a full width at half maximum of 11 nm.


Activated Carbon Produced From Agricultural Residues, Daniel W. Armstrong, V. J. Flanigan, William Joseph James, Jui-Lung Li, Kimber L. Rundlett Mar 1999

Activated Carbon Produced From Agricultural Residues, Daniel W. Armstrong, V. J. Flanigan, William Joseph James, Jui-Lung Li, Kimber L. Rundlett

Chemistry Faculty Research & Creative Works

A process for producing activated carbon from agricultural residues by heating the residues to a temperature in the range of about 250° C. to about 550° C. to volatilize organic compounds in the residues and to carbonize the residues and further heating to activate the carbonized residues. Activated carbon produced from agricultural residues.


Adaptive Critic Based Neural Networks For Control-Constrained Agile Missile Control, Dongchen Han, S. N. Balakrishnan Jan 1999

Adaptive Critic Based Neural Networks For Control-Constrained Agile Missile Control, Dongchen Han, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We investigate the use of an `adaptive critic' based controller to steer an agile missile with a constraint on the angle of attack from various initial Mach numbers to a given final Mach number in minimum time while completely reversing its flightpath angle. We use neural networks with a two-network structure called `adaptive critic' to carry out the optimization process. This structure obtains an optimal controller through solving Hamiltonian equations. This approach needs no external training; each network along with the optimality equations generates the output for the other network. When the outputs are mutually consistent, the controller output is ...


Stability Analysis Of Nonlinear Machining Force Controllers, Robert G. Landers, Yen-Wen Lu Jan 1999

Stability Analysis Of Nonlinear Machining Force Controllers, Robert G. Landers, Yen-Wen Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Model parameters vary significantly during a normal operation, thus, adaptive techniques have predominately been used. However, model-based techniques that carefully account for changes in the force process have again been examined due to the reduced complexity afforded by such techniques. In this paper, the effect of model parameter variations on the closed-loop stability for two model-based force controllers is examined. It was found that the stability boundary in the process parameter space can be exactly determined for force control systems designed for static force processes. For force control systems designed for first-order force processes, it was found that the stability ...


Environmental Performance Analysis Of Solid Freedom Fabrication Processes, Yanchun Luo, Zhiming Ji, Ming-Chuan Leu, R. J. Caudill Jan 1999

Environmental Performance Analysis Of Solid Freedom Fabrication Processes, Yanchun Luo, Zhiming Ji, Ming-Chuan Leu, R. J. Caudill

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a method for analyzing the environmental performance of solid freeform fabrication (SFF) processes. In this method, each process is divided into life phases. Environmental effects of every process phase are then analyzed and evaluated based on the environmental and resource management data. These effects are combined to obtain the environmental performance of the process. The analysis of the environmental performance of SFF processes considers the characteristics of SFF technology, includes material, energy consumption, processes wastes, and disposal. Case studies for three typical SFF processes: stereolithography (SL); selective laser sintering (SLS); and fused deposition modeling (FDM) are presented ...


Online Identification And Control Of Aerospace Vehicles Using Recurrent Networks, Zhenning Hu, S. N. Balakrishnan Jan 1999

Online Identification And Control Of Aerospace Vehicles Using Recurrent Networks, Zhenning Hu, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Methods for estimating the aerospace system parameters and controlling them through two neural networks are presented in this study. We equate the energy function of Hopfield neural network to integral square of errors in the system dynamics and extract the parameters of a system. Parameter convergence is proved. For control, we equate the equilibrium status of a "modified" Hopfield neural network to the steady state Riccati solution with the system parameters as inputs. Through these two networks, we present the online identification and control of an aircraft using its nonlinear dynamics.


Design, Optimization, And The Prototyping Of A Small Tuning-Fork Ultrasonic Piezoelectric Linear Motor, Daniel S. Stutts, James R. Friend Jan 1999

Design, Optimization, And The Prototyping Of A Small Tuning-Fork Ultrasonic Piezoelectric Linear Motor, Daniel S. Stutts, James R. Friend

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The design, optimization, and properties of a prototype small traveling-wave ultrasonic piezoelectric linear motor design are described. A method for optimizing the geometry of the motor to maximize its mechanical output for a given electrical input is described, as is the inherent properties of the design to maximize the motors durability and utilization of the piezoelectric material. Results from testing the motor demonstrate the design and indicate a maximum speed of 2.5 cm/s with a preload of 16 g due to an applied voltage of 80 V/RMS/ at an applied current of 15 mA.


Frequency Domain Robustness Analysis Of Hopfield And Modified Hopfield Neural Networks, Jie Shen, S. N. Balakrishnan Jan 1999

Frequency Domain Robustness Analysis Of Hopfield And Modified Hopfield Neural Networks, Jie Shen, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A variant of Hopfield neural network, called the modified Hopfield network, is formulated in this study. This class of networks consists of parallel recurrent networks which have variable dimensions that can be changed to fit the problem under consideration. It has a structure to implement an inverse transformation that is essential for embedding optimal control gain sequences. Equilibrium solutions of this network are discussed. The robustness of this network and the classical Hopfield network are carried out in the frequency domain using describing functions