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Articles 1 - 10 of 10
Full-Text Articles in Aerospace Engineering
Cooperative Uav Formation Flying With Obstacle/Collision Avoidance, Xiaohua Wang, Vivek Yadav, S. N. Balakrishnan
Cooperative Uav Formation Flying With Obstacle/Collision Avoidance, Xiaohua Wang, Vivek Yadav, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Navigation problems of unmanned air vehicles (UAVs) flying in a formation in a free and an obstacle-laden environment are investigated in this brief. when static obstacles popup during the flight, the UAVs are required to steer around them and also avoid collisions between each other. In order to achieve these goals, a new dual-mode control strategy is proposed: a “safe mode” is defined as an operation in an obstacle-free environment and a “danger mode” is activated when there is a chance of collision or when there are obstacles in the path. Safe mode achieves global optimization because the dynamics of …
Coupled-Mode Theory For Stimulated Raman Scattering In High-Q/Vm Silicon Photonic Band Gap Defect Cavity Lasers, Xiaodong Yang, C. W. Wong
Coupled-Mode Theory For Stimulated Raman Scattering In High-Q/Vm Silicon Photonic Band Gap Defect Cavity Lasers, Xiaodong Yang, C. W. Wong
Mechanical and Aerospace Engineering Faculty Research & Creative Works
We examine the dynamics of stimulated Raman scattering in designed high-Q/Vm silicon photonic band gap nanocavities through the coupled-mode theory framework towards optically-pumped silicon lasing. The interplay of other X(3) effects such as two-photon absorption and optical Kerr, related free-carrier dynamics, thermal effects, as well as linear losses such as cavity radiation and linear material absorption are included and investigated numerically. Our results clarify the relative contributions and evolution of the mechanisms, and demonstrate the lasing and shutdown thresholds. Our studies illustrate the conditions for continuous-wave and pulsed highly-efficient Raman frequency conversion for practical realization in monolithic silicon …
Efficient Sampling For Non-Intrusive Polynomial Chaos Applications With Multiple Uncertain Input Variables, Serhat Hosder, Robert W. Walters, Michael Balch
Efficient Sampling For Non-Intrusive Polynomial Chaos Applications With Multiple Uncertain Input Variables, Serhat Hosder, Robert W. Walters, Michael Balch
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The accuracy and the computational efficiency of a Point-Collocation Non-Intrusive Polynomial Chaos (NIPC) method applied to stochastic problems with multiple uncertain input variables has been investigated. Two stochastic model problems with multiple uniform random variables were studied to determine the effect of different sampling methods (Random, Latin Hypercube, and Hammersley) for the selection of the collocation points. The effect of the number of collocation points on the accuracy of polynomial chaos expansions were also investigated. The results of the stochastic model problems show that all three sampling methods exhibit a similar performance in terms of the the accuracy and the …
Multifrequency Eddy Current Inspection Of Corrosion In Clad Aluminum Riveted Lap Joints And Its Effect On Fatigue Life, Shridhar Natarajan, Anthony Chukwujekwu Okafor
Multifrequency Eddy Current Inspection Of Corrosion In Clad Aluminum Riveted Lap Joints And Its Effect On Fatigue Life, Shridhar Natarajan, Anthony Chukwujekwu Okafor
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency eddy current (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of eddy current inspection, corrosion product removal and fatigue testing are presented.
Product Family Design Knowledge Representation, Aggregation, Reuse, And Analysis, Jyotirmaya Nanda, Henri Thevenot, Timothy W. Simpson, Robert B. Stone, Matt R. Bohm, Steven B. Shooter
Product Family Design Knowledge Representation, Aggregation, Reuse, And Analysis, Jyotirmaya Nanda, Henri Thevenot, Timothy W. Simpson, Robert B. Stone, Matt R. Bohm, Steven B. Shooter
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A flexible information model for systematic development and deployment of product families during all phases of the product realization process is crucial for product-oriented organizations. In current practice, information captured while designing products in a family is often incomplete, unstructured, and is mostly proprietary in nature, making it difficult to index, search, refine, reuse, distribute, browse, aggregate, and analyze knowledge across heterogeneous organizational information systems. To this end, we propose a flexible knowledge management framework to capture, reorganize, and convert both linguistic and parametric product family design information into a unified network, which is called a networked bill of material …
Robust/Optimal Temperature Profile Control Of A High-Speed Aerospace Vehicle Using Neural Networks, Vivek Yadav, Radhakant Padhi, S. N. Balakrishnan
Robust/Optimal Temperature Profile Control Of A High-Speed Aerospace Vehicle Using Neural Networks, Vivek Yadav, Radhakant Padhi, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An approximate dynamic programming (ADP)-based suboptimal neurocontroller to obtain desired temperature for a high-speed aerospace vehicle is synthesized in this paper. a 1-D distributed parameter model of a fin is developed from basic thermal physics principles. ldquoSnapshotrdquo solutions of the dynamics are generated with a simple dynamic inversion-based feedback controller. Empirical basis functions are designed using the ldquoproper orthogonal decompositionrdquo (POD) technique and the snapshot solutions. a low-order nonlinear lumped parameter system to characterize the infinite dimensional system is obtained by carrying out a Galerkin projection. an ADP-based neurocontroller with a dual heuristic programming (DHP) formulation is obtained with a …
Determination Of Laser Absorption Coefficients Of Gas Mixtures Using An Ab Initio Md Model, Zhi Liang, Hai-Lung Tsai, Lan Jiang
Determination Of Laser Absorption Coefficients Of Gas Mixtures Using An Ab Initio Md Model, Zhi Liang, Hai-Lung Tsai, Lan Jiang
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In an Effort to Study the Laser Induced Dissociation of Gas Mixtures for an Ongoing Research Project on Diamond Thin Film Coating using Multiple Lasers, It is Necessary to Determine the Absorption Coefficient of Laser Energy by CO2 Gas. an Ab Initio Molecular Dynamics (AIMD) Model is Used to Determine the Laser Absorption Coefficient of CO2 Gas as a Function of Laser Wavelength and Gas Temperature. the Translational, Rotational, and Vibration Motions of Molecules Are All Taken into Account in Our Model. the Intra-Molecular Potential Energy is Obtained by Solving the Kohn-Sham Equation. the Projector-Augmented Wave (PAW) Exchange-Correlation Potential Function …
Optimal Neuro-Controller Synthesis For Impulse-Driven System, Xiaohua Wang, S. N. Balakrishnan
Optimal Neuro-Controller Synthesis For Impulse-Driven System, Xiaohua Wang, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper presents a new controller design technique for systems driven with impulse inputs. Necessary conditions for optimal impulse control are derived. A neural network structure to solve the resulting equations is presented. The solution concepts are illustrated with a few example problems that exhibit increasing levels of difficulty. Two linear problems-one scalar and one vector-and a benchmark nonlinear problem-Van Der Pol oscillator-are used as case studies. Numerical results show the efficacy of the new solution process for impulse driven systems. Since the theoretical development and the design technique are free from restrictive assumptions, this technique is applicable to many …
Simple Penning Ion Source For Laboratory Research And Development Applications, Joshua L. Rovey, Brandon P. Ruzic, Thomas J. Houlahan
Simple Penning Ion Source For Laboratory Research And Development Applications, Joshua L. Rovey, Brandon P. Ruzic, Thomas J. Houlahan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A simple Penning ion generator (PIG) that can be easily fabricated with simple machining skills and standard laboratory accessories is described. The PIG source uses an iron cathode body, samarium cobalt permanent magnet, stainless steel anode, and iron cathode faceplate to generate a plasma discharge that yields a continuous 1 mA beam of positively charged hydrogen ions at 1 mTorr of pressure. This operating condition requires 5.4 kV and 32.4 W of power. Operation with helium is similar to hydrogen. The ion source is being designed and investigated for use in a sealed-tube neutron generator; however, this ion source is …
Acoustic Emission Detection And Prediction Of Fatigue Crack Propagation In Composite Patch Repairs Using Neural Networks, Navdeep Singh, Navrag Singh, Anthony Chukwujekwu Okafor
Acoustic Emission Detection And Prediction Of Fatigue Crack Propagation In Composite Patch Repairs Using Neural Networks, Navdeep Singh, Navrag Singh, Anthony Chukwujekwu Okafor
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An aircraft is subjected to severe structural and aerodynamic loads during its service life. These loads can cause damage or weakening of the structure especially for aging military and civilian aircraft, thereby affecting its load carrying capabilities. Hence composite patch repairs are increasingly used to repair damaged aircraft metallic structures to restore its structural efficiency. This paper presents the results of Acoustic Emission (AE) monitoring of crack propagation in 2024-T3 Clad aluminum panels repaired with adhesively bonded octagonal, single sided boron/epoxy composite patch under tension-tension fatigue loading. Crack propagation gages were used to monitor crack initiation. The identified AE sensor …