bluuebunny/crossref_metadata_2025 huggingface dataset:
Measured and Predicted Air Flow in a Small Classroom
Authors: Emery A. F. , Lee Chung-Lin
Published: April 2014

Local/State building codes mandate the supply of fresh air to classrooms. Most designs adhere to these requirements through mechanical HVAC systems. For buildings that depend upon natural ventilation in which fresh air is supplied through windows, care must be taken to account for ambient conditions, i.e., air temperature, humidity, and wind velocity and direction, that can strongly affect the amount of fresh air. For classroom with multiple windows the question is which windows to open at any given time. This paper describes the measurement of air flow in a simple classroom and the use of CFD simulation to predict the circulation of air with an aim of determining if such a simulation may be used to define optimal window opening schedules.
Direct Adaptive Individual Blade Pitch Control for Large Wind Turbines
Authors: Thapa Magar Kaman S. , Balas Mark J. , Frost Susan A.
Published: April 2014

In this paper a theory of Adaptive Disturbance Rejection Control is used to design an individual blade pitch controller for a utility scale wind turbine. The goal of the Adaptive Disturbance Rejection Control is to regulate the blade pitch angle individually to reduce the asymmetrical loading in blade due to vertical wind shear and also to reject the unnecessary disturbance introduced by the wind turbulence. The applicability of the theory is illustrated by implementing the controller in the National Renewable Energy Laboratory (NREL)s 5 MW wind turbine model and simulating it in MATLAB/Simulink.
An AC Dielectrophoretic Trap for Cellular Assembly
Authors: Hossan Mohammad Robiul , Dillon Robert , Dutta Prashanta
Published: April 2014

A mathematical model and numerical techniques are proposed to study AC electric field induced cellular assembly in a microfluidic device. In the mathematical model, the Maxwell stress tensor is used to calculate the dielectrophoretic force acting on particles by considering the physical effect of particles in the computational domain. Thus, the proposed model eliminates the approximations used in point dipole methods for calculating dielectrophoretic force. The numerical method is based on hybrid immersed boundary-immersed interface methods. An immersed boundary method is used for the fluid equations and particle transport, while an immersed interface method is employed to obtain the AC electric field in a fluid media with suspended particles. For the immersed interface method, an iterative algorithm is developed to solve the complex Poisson equation using a real variable formulation. The decoupled algorithm for solving complex differential equations converges rapidly. The hybrid method is used to investigate the physics of AC dielectrophoresis in a cross-channel junction. The numerical results show that with proper design and appropriate selection of applied potential and frequency, global electric field minima can be obtained to facilitate multiple particle trapping by exploiting the mechanism of negative dielectrophoresis.
Melting in Vertical Cylinders During Thermal Energy Storage
Authors: Sridharan Prashanth , Ramos Archibold Antonio , Rahman Muhammad M. , Goswami D. Yogi , Stefanakos Elias L.
Published: April 2014

The present study numerically investigates the process of melting in a hollow vertical cylinder, filled with a phase change material (PCM). The PCM used is sodium nitrate, which expands upon melting. Therefore, the cylindrical shell is partially filled with the PCM and the remaining volume is occupied by air. The influence of cylinder shape on the melting and heat transfer rate is analyzed. The numerical model takes both conductive and convective heat transfer into account during the melting process. For the problem being considered here, the dimensionless numbers that characterized the process are the Grashof, Stefan, and Prandtl numbers. The Aspect Ratio (AR) is used to characterize the shape of the cylinder, which is defined as the ratio of the height to the diameter of the cylinder. In this study, a range of AR values from 0.25 to 10 are investigated. Cylinders with small AR, corresponding to high Grashof numbers, lead to lower melting times compared with cylinders with high AR. The partially melted PCM shape differed between the high and low AR cases. The molten PCM stream function was also influenced greatly by the variation in solid PCM shape.
The Influence of Neck Kinematics on Brain Pressures and Strains Under Blast Loading
Authors: Roberts J. C. , Harrigan T. P. , Ward E. E. , Nicolella D. , Francis L. , Eliason T. , Merkle A. C.
Published: April 2014

Strains and pressures in the brain are known to be influenced by rotation of the head in response to loading. This brain rotation is governed by the motion of the head, as permitted by the neck, due to loading conditions. In order to better understand the effect neck characteristics have on pressures and strains in the brain, a human head finite element model (HHFEM) was attached to two neck FEMs: a standard, well characterized Hybrid III Anthropometric Test Device neck FEM; and a high fidelity parametric probabilistic human FEM neck that has been hierarchically validated. The Hybrid III neck is well-established in automotive injury prevention studies, but is known to be much stiffer than in vivo human necks. The parametric FEM is based on CT scans and anatomic data, and the components of the model are validated against biomechanical tests at the component and system level. Both integrated head-neck models were loaded using pressure histories based on shock tube exposures. The shock tube loading applied to these head models were obtained using a computational fluid dynamics (CFD) model of the HHFEM surface in front of a 6 inch diameter shock tube. The calculated pressure-time histories were then applied to the head-neck models. The global head rotations, pressures, brain displacements, and brain strains of both head-neck models were compared for shock tube driver pressures from 517 to 862 kPa. The intracranial pressure response occurred in the first 1 to 5 msec, after blast impact, prior to a significant kinematic response, and was very similar between the two models. The global head rotations and the strains in the brain occurred at 20 to 100 msec after blast impact, and both were approximately two times higher in the model using the head parametric probabilistic neck FEM (H2PN), as compared to the model using the head Hybrid III neck FEM (H3N). It was also discovered that the H2PN exhibited an initial backward and small downward motion in the first 10 ms not seen in the H3N. The increased displacements and strains were the primary difference between the two combined models, indicating that neck constraints are a significant factor in the strains induced by blast loading to the head. Therefore neck constraints should be carefully controlled in studies of brain strain due to blast, but neck constraints are less important if pressure response is the only response parameter of primary interest.
The Influence of a Harmonic Motion on a Melting Process With Natural Convection
Authors: Avila Ruben , Ramos Eduardo
Published: April 2014

We study the heat transfer rate in an oscillatory, two dimensional solid-liquid system which is melted from below. As the phase change process takes place, the height of the fluid layer in the lower part of the cavity is continuously enlarged. The influence of the angular frequency of the motion (Taylor number) and the melting rate (Stefan number) on: (i) the heat transfer in the liquid (Nusselt number), (ii) the temperature field and (iii) the shape of the interface, is analyzed. The governing equations together with the Stefan condition at the interface are solved by using a spectral element method. It is observed that as the height of the liquid layer increases, a non-steady unicellular flow appears, and it leads to an oscillatory behaviour of the Nusselt number. As the height of the liquid layer increases further, the onset of the thermal convection and its instabilities modify the shape of the interface, and the heat transfer rate in the molten material. We find that (i) for large Stefan numbers, the heat is transported mostly along the inclined walls, while for low Stefan numbers, a Rayleigh-Bénard type convection is dominant, and (ii) for large Taylor numbers, the motion induced by the oscillation is small, resulting in a Nusselt number that decreases monotonously as a function of time, in contrast, for small Taylor numbers, an oscillatory Nusselt number is displayed.
The Influence of Geometry, Wall Thickness, and Material on the Acoustic Resonance Predictions in Closed-Ended Water-Filled Piping
Authors: Mokhtari Alireza , Chatoorgoon Vijay
Published: April 2014

Acoustic pressure resonances in liquid-transporting pipe systems affect performance and safety. Accurate predictions of acoustic pressure resonances are a necessary requirement for any practical piping system undergoing some acoustic excitations. Thus, understanding the nature of acoustic wave propagation in water filled piping systems needs to be established based on fundamental experiments and analysis. To investigate acoustic resonance, no flow experiments with different configurations, wall thicknesses and materials were compared with theoretical and numerical calculations.

This paper presents an experimental study showing that how linear wave theory, based on a transmission matrix method, and ABAQUS as commercial software do predict the acoustic resonance frequency peaks from 20 to 500 Hz, and discusses the resonant frequency shifts. Study of tube wall thickness, material (stainless steel and Aluminum), some equal and unequal branch configurations and combination of all investigated parameters for “Closed-end” tubes are discussed.
Monitoring of Polymer Plastication in the Injection Moulding Process
Authors: Pham Thuy Linh , Balcaen Jean , Chhay Sambor , Bereaux Yves , Charmeau Jean-Yves
Published: April 2014

In injection moulding or in extrusion, plastication is the step during which polymer pellets are melted by the means of mechanical dissipation provided by a rotating screw and by thermal conduction coming from a heated metallic barrel. This step is crucial for melt thermal homogeneity, charge dispersion and fibre length preservation. Although there have been a large number of theoretical and experimental studies of plastication during the past decades, mostly on extrusion and mostly using the screw extraction technique, extremely few of them have dealt with trying to visualise plastication, let alone measuring the plastication profile in real-time. As a matter of fact, designing such an equipment is an arduous task. We designed an industry-sized metallic barrel, featuring 3 optical glass windows; each window possessing 3 plane faces itself to allow for visualisation and record by synchronised cameras and lightening by lasers. The images recorded can be further analysed by digital image processing. Preliminary results confirm the plastication theory and show a compacted solid bed and a melt pool side by side. The total plastication length is a direct function of screw rotation frequency as it is obvious from results on the melt pool width, which increases when the screw rotation frequency decreases. However, some evidence of solid bed breakage has been recorded, whereby the solid bed does not diminish continuously along the screw but is fractured in the compression zone.
Spectral-Domain Based Impact Force Identification for Rod Structures
Authors: Ghaderi Pooya , Rich Steven I. , Dick Andrew J.
Published: April 2014

Indirect impact force identification has attracted researchers due to the simplicity of indirect methods for calculating the applied force during the impact incident. In this paper, an impact force identification method for rod structures is proposed. The proposed method uses the spectral finite element method. The spectral finite element method is a frequency-based finite element method that takes advantage of the benefits of spectral methods and the simplicity of the finite element method. Using the frequency domain method for impact force identification simplifies the calculations and allows for the identification of impact forces with high frequency content, including MHz and above. The impact force identification method uses the collected data of the response of a section of the structure and utilizes the spectral finite element model of the structure to calculate the impact force. The results of the numerical study display strong agreement between the simulated impact force and the identified force. The performance of the force identification method is verified by applying it to experimental data collected from an impacted rod structure.
Do American Football Helmets Protect Players Against Concussions?
Authors: Honarmandi Peyman , Sadegh Ali M. , Cavallaro Paul V.
Published: April 2014

In recent years, reported concussions among American football players have attracted investigators attention as to the safety of the football helmet. This study investigates the effects of concussive impact forces on the brain of football players and the shock absorbing performance of actual football helmets. Initially, a lumped-mass analysis of the helmet and the head was carried out and then more detailed finite element models of the head and the helmet were analyzed. The results indicate that the acceleration and strain of the brain are both above the threshold of the concussion and that the current design of football helmet may not protect players against concussion.
Measuring the Temperature Coefficient of Resistance for Nanospring Combustion Catalysts
Authors: Quinn C. , Steciak J. , Budwig R. , McIlroy D. , Beyerlein S.
Published: April 2014

Platinum has been recognized as a viable combustion catalyst. Its change in electrical resistance with temperature has been used to measure light-off temperatures and rates of heat generation for various fuel-oxygen mixtures at the University of Idaho. In an attempt to maximize the surface area for these reactions to occur, platinum-coated nanosprings have been manufactured. A reliable method of determining an effective temperature-dependent temperature coefficient of resistance (α(T)) for the nanosprings assembly has been developed and verified using pure platinum. Measured values of α(T) for platinum were matched against literature data at 373 and 1100 K. A linear fit was assumed for the gap between these temperatures; measurements made with platinum at intermediate temperatures were in good agreement. Using the same methodology, α(T) for the nanosprings assembly will be determined, which will allow for further research of the nanosprings in catalytic combustion.
Application of Creativity Tools to Gas Turbine Engine Compressor Clearance Control
Authors: Ekong Godwin I. , Long Christopher A. , Childs Peter R. N.
Published: April 2014

Creativity tools are methods that can be used to promote innovative products and creative actions. There is a wide range of tools available for idea generation, employing divergent and convergent thinking for problem definition, exploration of problem features, generation of solution options, evaluation and implementation of ideas. Fundamental to their effective operation is to make use of a suitable creativity tool for a particular application and individual or team, to aid in the process of problem-solving, the refinement of old ideas, and the generation and implementation of new ideas. The principal creativity tool described in this paper is TRIZ which is the Russian acronym for Teoriya Resheniya Izobretatelskikh Zadatch meaning Theory of Inventive Problem Solving. This paper emphasizes the processes and specific TRIZ tools used in the implementation of TRIZ in the exploration of concepts for tip clearance control in gas turbine high pressure compressors in aircraft engines. The TRIZ process was used to categorize ideas generated through divergent thinking thus reducing the number of ideas carried forward for further engineering analysis.
On the Time Dependence of Size Effect in Polydimethylsiloxane
Authors: Alisafaei F. , Sanei Seyed Hamid Reza , Smith E. J. , Han Chung-Souk
Published: April 2014

Nanoindentation tests at the nano-micrometer scales are conducted to investigate the depth and time dependent deformation mechanisms of polydimethylsiloxane (PDMS). Astonishing indentation size effects observed in these experiments are analyzed with an existing theoretical hardness model, and the effects of loading time on the hardness and indentation stiffness of PDMS are studied. The change in the indentation recovery with respect to indentation depth and loading time are analyzed. Furthermore, it is shown that the stiffness of PDMS obtained at the maximum applied force can be efficiently applied to validate the applied theoretical hardness model with the experimental results.
An Inverse Radiation Model for Optical Determination of Temperature and CO2 Concentration: Development and Validation
Authors: Ren Tao , Reeder Todd A. , Modest Michael F.
Published: April 2014

By minimizing the differences between measured and predicted transmissivity spectra, an inverse radiation model was developed to reconstruct temperature and species concentration from homogeneous gas media. The model was validated by retrieving temperatures and concentrations from experimental medium-resolution CO2 transmissivity data obtained by Bharadwaj and Modest [1, 2]. Optimal wavenumber ranges for CO2 transmissivity measured across a wide range of temperatures and concentrations were determined according to the performance of inverse calculations. Results indicate that the inverse radiation model works well and the inverse radiation technique is superior to thermocouples and flow meters for measurements of temperature and gas concentration.
Fracture Toughness Variation Induced by Geometric Confinement in Nanostructures
Authors: Cheng Shao-Huan , Sun C. T.
Published: April 2014

The multiscale process of material failure from the interatomic bond breaking to the visible crack propagation leads us to explore the validity of linear elastic fracture mechanics (LEFM), particularly for fracture toughness as a constant from nanoscale to macroscale. In the current study, by considering the local virial stress averaged within one lattice, we overcome the barrier of ambiguous crack-tip stress field in molecular dynamics (MD) and perform direct estimation of fracture toughness not through remote stresses. By changing the specimen geometry, i.e., either the crack length or the specimen height (the dimension perpendicular to the crack line), the MD and corresponding finite element method (FEM) solutions show that fracture toughness decreases as the crack length or specimen height decreases. Consequently, fracture toughness cannot be treated as a material constant for nanostructures. The size of the singular stress zone (K-dominance zone) is used to explain the size-dependent behavior of fracture toughness. While the crack length or specimen height decreases, the decreasing K-dominance zone makes the singular part around the crack tip stress not capable of accounting for the full fracture driving force.
Analysis of a Permselective Membrane-Free Alkaline Direct Ethanol Fuel Cell
Authors: Huang Jing , Bahrami Hafez , Faghri Amir
Published: April 2014

A physical model is developed to study the coupled mass and charge transport in a permselective membrane-free alkaline direct ethanol fuel cell. This type of fuel cell is not only free of expensive ion exchange membranes and platinum based catalysts, but also features a facile oxygen reduction reaction due to the presence of alkaline electrolyte. The proposed model is first validated by comparing its predictions to the experimental results from literature and then used to predict the overall performance of the cell and reveal the details of ion transport, distribution of electrolyte potential and current density. It is found that: (i) KOH concentration lower than 1 M notably impairs cell performance due to low electrolyte conductivity; (ii) the concentration gradient and electrical field are equally important in driving ion transport in the electrolyte; (iii) the current density distributions in the anode and cathode catalyst layers keep non-uniform due to different reasons. In the anode, it is caused by the ethanol concentration gradient, while in the cathode it is because of the electrolyte potential gradient; and (iv) at low cell voltage, current density distribution in the catalyst layer shows stronger non-linearity in the anode than in the cathode.
Cerebral Blood Pressure Rise During Blast Exposure in a Rat Model of Blast-Induced Traumatic Brain Injury
Authors: Assari Soroush , Laksari Kaveh , Barbe Mary , Darvish Kurosh
Published: April 2014

Blast-induced traumatic brain injury (bTBI) has been called the signature wound of war in the past decade. The mechanisms of such injuries are not yet completely understood. One of the proposed hypotheses is the transfer of pressure wave from large torso blood vessels to the cerebrovasculature as a major contributing factor to bTBI. The aim of this study was to investigate this hypothesis by measuring cerebral blood pressure rise during blast exposure and comparing two scenarios of head-only or chest-only exposures to the blast wave. The results showed that the cerebral blood pressure rise was significantly higher in chest-only exposure, and caused infiltration of blood-borne macrophages into the brain. It is concluded that a significantly high pressure wave transfers from torso to cerebrovasculature during exposure of the chest to a blast wave. This wave may lead to blood-brain barrier disruption and consequently trigger secondary neuronal damage.
Collapse of Rectangular Granular Piles in Air and Water
Authors: Babaei M. H.
Published: April 2014

Granular materials are processed in many industries including agricultural, pharmaceutical, mining, and oil-sand and several geophysical processes such as landslides and avalanches. There are few models capable of predicting the flow of granular materials and particularly their collapse. Theoretical studies of the topic usually encounter difficulties in accurately predicting the collapse dynamics and final stable heaps. The two-dimensional gravitational collapse of cohesionless rectangular granular piles is numerically investigated in this paper. Piles surrounded by either air (dry case) or an oil-water mixture (wet case) undergo a dam-break collapse onto a horizontal base. The granular material is modeled as a perfectly plastic substance based on the Mohr-Coulomb law. The constitutive relations represent the granular material as a fluid, with a shear viscosity as a function of solids pressure, the second invariant of the deviatoric strain-rate tensor, and the internal angle of friction of the granular material. This two-phase flow problem (grains and liquid or air) is then formulated accordingly and solved by the mixture model method for the wet collapse and the level-set method for the dry collapse using COMSOL finite-element software. In both air and the liquid, stable heaps are achieved. The results are compared with experimental measurements of Balmforth & Kerswell [1] and Rondon et al. [2]. The model can closely predict the final shape of the collapsed dry pile. The final shape of the collapsed wet pile is also well-predicted when its initial packing concentration is relatively low. Further developments are needed to model the wet collapse of high-initial-concentration piles.
Investigating the Rheological Properties of Chopped Corn Stover Biomass in Bulk
Authors: Özdemir Ozan Ç. , Suess Taylor N. , Letcher Todd M. , Gent Stephen P.
Published: April 2014

Flow parameters of chopped biomass, namely corn stover, are analyzed applying material testing techniques. The bulk fluid motion of the chopped biomass corn stover is examined using a custom made direct shear cell and a universal testing machine. The goal of this analysis is to test the bulk solid shear stress, internal friction, internal angle of friction and cohesion. The results of the stated tests are statistically analyzed and compared with literature. The measured properties of the biomass have the potential to be used in computer simulations for bulk solid flow analysis. The bulk fluid motion of the pulverized/chopped biomass can be simulated in storage and transportation equipment, including auguring screws and pneumatic conveyance systems, as well as devices for feeding biomass into thermochemical and biochemical reactors. Traditional biochemical and thermochemical reactors operate as batch systems because of the difficulty of feeding the biomass feedstock in a continuous manner. Having a clearer background about the structural and rheological properties of biomass feedstock will help simulate bulk-solid flows computationally and design efficient storage and continuous feeding systems.
External Disturbance Compensation for Humanoid Robots via a Configuration Control Approach
Authors: Nolen Chris , Fahimi Farbod
Published: April 2014

A redundancy resolution scheme to maintain a desired support force on the stance foot of a redundant humanoid robot is considered. The proposed motion planner will mitigate the effect of unknown external disturbances on the robot. For the first time, the proposed approach considers not only the position of the Zero-Moment-Point (ZMP), but also the reaction forces in the plane of the foot and the reaction moment normal to the plane of the foot. So, not only possible tipping of the robot due to an external disturbance, but also possible sliding of the foot, is addressed. An acceleration level configuration control approach is used to find the optimum solution for joint accelerations of the robot to reproduce both the desired gait and support reactions as close as possible. These joint accelerations are then integrated to develop joint positions to be implemented by the robot. The motion planner is demonstrated by simulating a planar humanoid robot. It is shown the proposed approach is effective in mitigating external disturbances while maintaining the desired body trajectory.
Using Open Ended Undergraduate Robotics Projects to Teach Innovation to Today’s Engineering Students
Authors: Richter Donald C. , Saad Hani S. , Weiser Martin W.
Published: April 2014

Engineering and Engineering Technology students need to learn to innovate and embrace new technologies as they develop and progress through their careers. The undergraduate degree program needs to provide this first opportunity at innovation allowing the student to gain experience and confidence at solving technological problems. This paper describes the learning experiences in innovation using an undergraduate course in robotics and automation. The course is composed of Mechanical Engineering and Mechanical Engineering Technology students. The paper relates the successful attempt the students had in developing and using innovation through the creation opened-ended industrial robot system projects. The undergraduate student project teams in the course are self-directed and have to use innovation to develop a robotic project of their own design. This breaks the cycle of students just doing the same preset experiments that others have done before them. Although doing preset experiments can reinforce theory given in classroom, it does little to develop skills in innovation, which will be the key to success in the global economy. The course provides an excellent framework for the student teams to demonstrate their ability to innovate using new technology to solve a complex problem while having the mentorship from instructors as they take their first steps in actually doing innovation. The confidence and process used to solve these problems will provide a basis upon which they can formulate new strategies to incorporate new technologies throughout their career.
Building a Community - How to Enrich an Engineering Technology Program With an Identity, Presence and Pride
Authors: Miller Amy L. , Samples Jerry
Published: April 2014

Potential students and their parents are looking at schools differently than in the past: an out cropping of the new generation of parents and students. Academics are still the prime concern but more frequently than in past years families are concerned about the organization. Does the program have an identity that will assist in getting jobs? Is there a presence within the community? Do the faculty and students take pride in what is being accomplished and are graduates proud of their education and their school? The best way to answer these questions is to allow the families a chance to interact with students, see their products, read the posters of their work and show where graduates work.

This paper will discuss the process needed to cultivate an engineering or engineering technology program into one with an identity, presence and ultimately pride. The paper will describe leadership steps that can be taken to generate pride and distinctiveness, first to the faculty, and then to the student body. Resulting in a close nit and enviable community where education can flourish, and the students’ academic related clubs are active and involved on campus. Where alumni look forward to visiting and helping with student projects. Where they take pride in their alma mater and often seek new hires from the program. Where faculty members win teaching awards and enjoy their time in the classroom and advising students.

A case study will be presented and, detailed examples will be cited demonstrating how the students “caught on” and took pride to a new level based on the successful implementation at a university. It will show that leadership lessons learned by students while in school, continued to be used after they graduated. The case study will further demonstrate why everyone associated with the program feels that the engineering technology program is a great place to learn and work.
Structural Health Monitoring of Composite Wind Turbine Blades Using Coherent Guided Waves From Diffuse Fields
Authors: Tippmann J. D. , Lanza di Scalea F.
Published: April 2014

Diffused acoustic fields exist during the operation in wind turbine blades because of consistent and stochastic loads and the aerodynamic noise generated from turbulent pressure fields. The Green’s function can be extracted from an ensemble average of the cross-correlations of signals recorded from two passive sensors within the diffused acoustic field. Here the wave fields reconstructed are multimodal and dispersive, which makes their extraction challenging. The causal and anti-causal Green’s function is estimated by taking the derivative of the ensemble average of cross correlation.

This method was studied experimentally using a wind turbine test blade (CX-100) located at the UCSD’s Powell Structural Laboratories. A diffuse field was approximated by exciting the skin of the blade with a random signal at several locations using an electrodynamic shaker. The reconstructed Green’s function estimate is compared to experimentally measured impulse response functions. The use of various features of the reconstructed Green’s function for potential applications to structural health monitoring of wind turbine blades is discussed.
Development of a Virtual Reality Simulation Testbed for Collaborative UGV and UAV Research Using MATLAB
Authors: Brech Dale E. , Hoover Randy C.
Published: April 2014

This paper presents a virtual reality simulation testbed for evaluation of collaborative control efforts using unmanned ground vehicles (UGV) and unmanned aerial vehicles (UAV). The UGVs are governed by differential drive vehicle kinematics, while the nonlinear dynamics of a quadrotor UAV are implemented. In addition, the system is built with modularity in mind so as to allow for easy expansion of multiple UGVs and UAVs working in collaboration. Such a simulation system allows for research in vehicle control, path planning, formation structures, and centralized/distributed control topologies to be easily and cost effectively explored. As a bonus, virtual cameras are mounted on each vehicle allowing exploration into control using visual feedback mechanisms. This paper describes the simulation testbed architecture, implementation of the dynamics and extended Kalman filter observers, and base-line control laws developed for stabilization and tracking.
Vibration Control of H-Shaped Planar Frames Based on the Classical Euler-Bernoulli and the Advanced Timoshenko Bending Theories
Authors: Mei C.
Published: April 2014

Coupled bending and longitudinal vibrations in H-shaped planar frames are controlled from a wave standpoint, in which vibrations are described as waves traveling along uniform structural waveguides, and being reflected and transmitted at structural discontinuities. Active discontinuities are created using active control forces/moments both along structural elements and at structural joints to control vibration waves. The bending vibrations are modeled and controlled using the classical Euler-Bernoulli as well as the advanced Timoshenko theories. Numerical examples are presented. Comparisons are made between the results obtained using the classical Euler-Bernoulli model and the advanced Timoshenko model. Good agreements have been reached at low frequencies. However, discrepancies are significant at higher frequencies, typically when the transverse dimensions are not negligible with respect to the wavelength. This study addresses the importance of taking into account the effects of rotary inertia and shear distortion at high frequencies.
3D Core-Shell Simulation of Hydrogel Swelling Behavior for Controlled Drug Delivery
Authors: Wang Jilong , Qiu Jenny , Wang Shiren
Published: April 2014

In this paper, a three-dimensional dynamic model describing drug delivery and swelling behavior of polyelectrolyte gels was developed based on the Maxwell-Stefan equation and Bio-heat equation. COMSOL software was employed to simulate hydrogel swelling and the transportation of created automatically by COMSOL, and it had 78035 elements, which was unconcerned with the results. The results showed that Maxwell-Stefan equation and Bio-heat equation were suitable for modeling hydrogel behavior of swelling with temperature change. In addition, when temperature increased, the hydrogel swelling increased which also intensified drug release.
Computational Studies on the Flow Field of Various Shapes-Bladed Vertical Axis Savonius Turbine in Static Condition
Authors: Khan Jobaidur , Bashar Mohammad Mohibbul , Rahman Mosfequr
Published: April 2014

Vertical Axis Wind Turbine (VAWT) is the least efficient conventional wind energy generator. But the inherent advantage of facing the wind direction and capability to operate in low wind speed and non-smooth wind flow regions are two main reasons to research on it and to find more efficient design. The simplest form of VAWT is known as Savonius turbine and difference of the drag force on its blades is the operating principal. The main objective of this study is to analyze the performance data (numerically obtained) Savonius turbine blades. This study is in preliminary stage; experiment will be performed in near future. A Computational Fluid Dynamics (CFD) analysis has been used. Effect of changing the inlet velocity and mesh dependency is observed in this study. These models are simulated with CFD software ANSYS/FLUENT. Comparing previous models it has been found that, airfoil shaped three bladed rotor produces better result than regular semi-circular wind turbines. Changing the airfoil shape may show more interesting result in future.
On the Trabecular Morphologies and Load Transfer to the Brain
Authors: Hashemi Siavash , Saboori Parisa , Mansoor-Baghaei Shahab , Sadegh Ali M.
Published: April 2014

The human brain trabeculae contain strands of collagen tissues connecting the arachnoid to the pia mater. In this paper the mechanotransductions of the external loads to the head passing through different trabecular architectures of the subarachnoid space were investigated. This has been accomplished by creating several local 2-D models consist of skull, dura mater, arachnoid, trabecular architecture and the brain. Different orientations of several architectures of the trabeculae were also analyzed. All models were subjected to the same loading and constraints. The strains in the brain for each model of the architecture and morphology were determined and compared to other corresponding models. It is concluded that the strain in the brain is less where the tree-shape trabeculae are upright, where the branches are attached to the arachnoid mater and the stems are attached to the pia mater. In addition, in the case of other morphologies the strain in the brain is less when the ratio of the trabecular area to the CSF space is less.
Acoustic Wave Propagation Simulation in Double-Layered Composite Cylindrical Structures
Authors: Du Jikai
Published: April 2014

Ultrasound guided waves have been recognized as an effective tool for the rapid and long-range inspection of composite cylindrical structures, but its application is still limited due to the complex nature of guided waves and their interactions with material geometry and material properties. This paper uses finite element technique to simulate the ultrasound guided wave propagation in layered composite cylinders. Ultrasound guided wave propagation was analyzed in a double-layered cylinder composed of an anisotropic unidirectional carbon fiber/epoxy resin composite layer wrapped on an isotropic aluminum cylinder. The carbon fiber orientation is either along the cylinder circumferential direction or axial direction. Ultrasound wave is excited from a PZT-4 transducer which is placed on the top of a Plexiglas wedge to adjust the ultrasound incident angle into the cylinder. Low ultrasound frequencies at 0.5 and 1.0 MHz were selected to improve the effect of attenuation and simulation efficiency. Wave propagation velocities and wave structures were analyzed at various positions of the cylinder. This study helped to examine the effect of fiber orientation on wave dispersion characteristics and to assess the feasibility of applying ultrasound guided wave technique for the evaluation of composite cylindrical structures.
Second Law Analysis of Tree-Shaped Fins for the Heat Transfer Enhancement in a PCM Thermal Storage System
Authors: Sciacovelli Adriano , Guelpa Elisa , Verda Vittorio
Published: April 2014

Latent heat thermal energy storage (LHTES) systems based on phase change materials (PCMs) are a promising option to be employed as effective energy storage devices. PCM allows one to achieve high energy storage density and almost constant temperature energy retrieval, however LHTES systems performance is limited by poor thermal conductivity of the PCMs which leads to unacceptably low melting and solidification rates. Thus, heat transfer enhancement techniques are required in order to obtain acceptable melting and solidification rates.

The preliminary design of a shell-and-tube LHTES unit is investigated by means of computational fluid-dynamics (CFD). Three different fin designs are considered: a conventional radial fin, a constructal Y-shaped fin design and a non-constructal Y-shaped configuration previously investigated by the authors. The performances of each fin configuration are evaluated by means of a Second-law analysis. Moreover, local and global entropy generation rates are analyzed in order to show the main source of thermodynamic irreversibilities occurring in the system.

The analysis indicates that solidification rate is significantly enhanced when Y-shaped fins are adopted in the LHTES unit, however the constructal Y-shaped geometry is not optimal since further improvements can be achieved by means of a Y-shaped fins with elongated secondary branches.
Implications of Thermal Discharge Limits on Future Power Generation in Texas
Authors: Cook Margaret A. , King Carey W. , Webber Michael E.
Published: April 2014

The recent drought in Texas revealed the vulnerability of curtailment for some power plants due to cooling water supplies being too hot. Assessing the risk of reduced operations at thermoelectric power plants associated with thermal discharge limits, as well the potential for cooperation between power plants, can increase the resiliency of the electricity grid in Texas and aid future planning. This evaluation compares the observed effluent discharge water temperatures from thermoelectric power plants in the Electric Reliability Council of Texas (ERCOT) interconnection with Environmental Protection Agency (EPA) discharge temperature limits. Results indicate that at least two major power plants representing over 3,000 MW of cumulative generation capacity have operated at or near these temperature limits in the past. Predicted warming from heat waves, droughts, or climate change might increase ambient air temperature (one of the primary factors affecting effluent temperature) causing even higher derating in the future.

We modeled current and future average monthly cooling water effluent temperature for open loop and recirculating cooling pond systems in ERCOT using current climate data and predictions of ambient air temperature, electricity generation, dew point, and wind speed for 2027–2032. While there are some power plants that are projected to be exposed to thermal effluent-related curtailment, we estimate that there is six times as much electricity generation potential available from other existing generators that can meet demand without reaching thermal effluent temperature limits. That is, this work’s analysis indicates that other existing power plants could generate additional electricity to offset the curtailment of the particular power plants at greatest risk from derating to maintain grid reliability.
An Experimental Setup for API Assessment of a Valved Holding Chamber Device
Authors: Oliveira Ricardo F. , Teixeira José Carlos , Marques Helena Maria C. , Teixeira Senhorinha F.
Published: April 2014

Typically for young children and elders, the asthma treatment procedure using pMDI devices bring some usage coordination difficulties. Therefore, and accordingly to several asthma treatment guidelines, the prescription of a VHC, as an add-on device for the pMDI, is advisable. These devices consist of an expansion chamber where the air slows down, as well as, the pMDI spray plume. Allowing the patient to breathe whenever he wants, independently from the moment of the pMDI actuation, also reduces the “cold-freon” effect and allows a more effective evaporation of the propellant. The effectiveness evaluation of VHC and pMDI devices is made through the quantification of drug delivered to the patient lungs. A simple collection filter is not enough for an accurate assessment of the device. Since the size of the particles delivered matter the most, the use of an impaction apparatus is essential. Accordingly to the Canadian normative for VHC assessment (CAN/CSA/Z264.1-02:2008), the experimental testing shall be done by using a breath simulator instead of a constant flow pump. The evolution of these tests shall move towards more realistic testing conditions. This work reports the project and construction an experimental setup for a correct assessment of the VHC devices effectiveness. The experimental setup is based in the work of Foss & Keppel (1999) and the contribution of Finlay (1998) and Miller (2002). The project and optimization of the major components, such as, breath cycle simulator by means of a cam-follower mechanism, a mixing cone and the vacuum pump used, are herein described and discussed.
Characterization of Metal Oxide Sensor Thin Films Deposited by Spray Pyrolysis
Authors: Khatami S. M. Navid , Kuruppumullage D. Nadun , Ilegbusi Olusegun J.
Published: April 2014

Chemical Spray Pyrolysis (CSP) of ZnO and SnO2 is of interest for gas sensor applications. The structural properties of the deposited film can be strongly influenced by deposition conditions. In this work, two solutions consisting of Tin Chloride and Zinc Chloride was sprayed on a heated substrate, where temperature was varied from 400° C to 450° C for ZnO, and from 350° C to 500° C for SnO2. X-ray diffraction and scanning electron microscopy, indicating a non-homogenous-structured film formed at low temperature for both oxides. At 450° C, a porous structure is observed for SnO2. This structure becomes homogenous at higher temperature. It was also found that at temperatures lower than 450° C, substrate temperature has significant impact on the composition of the synthesized films.
Effects of Attached Body on Biomechanical Response of the Helmeted Human Head Under Blast
Authors: Salimi Jazi M. , Rezaei A. , Karami G. , Azarmi F. , Ziejewski M.
Published: April 2014

The results of a computational study on the effect of the body on biomechanical responses of a helmeted human head under various blast load orientations are presented in this work. The focus of the work is to study the effects of the human head model boundary conditions on mechanical responses of the head such as variations of intracranial pressure (ICP). In this work, finite element models of the helmet, padding system, and head components are used for a dynamic nonlinear analysis. Appropriate contacts and conditions are applied between different components of the head, pads and helmet. Blast is modeled in a free space. Two different blast wave orientations with respect to head position are set, so that, blast waves tackle the front and back of the head. Standard trinitrotoluene is selected as the high explosive (HE) material. The standoff distance in all cases is one meter from the explosion site and the mass of HE is 200 grams. To study the effect of the body, three different boundary conditions are considered; the head-neck model is free; the base of the neck is completely fixed; and the head-neck model is attached to the body. Comparing the results shows that the level of ICP and shear stress on the brain are similar during the first five milliseconds after the head is hit by the blast waves. It explains the fact that the rest of the body does not have any contribution to the response of the head during the first 5 milliseconds. However, the conclusion is just reasonable for the presented blast situations and different blast wave incidents as well as more directions must be considered.