bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Inlet Swirl on the Aerodynamics of a Model Turbofan Lobed Mixer
Authors: Lei Zhijun , Mahallati Ali , Cunningham Mark , Germain Patrick
Published: May 2012

This paper presents a detailed experimental investigation of the influence of core flow inlet swirl on the mixing and performance of a 12-lobe un-scalloped turbofan mixer. Measurements were made downstream of the mixer in a co-annular wind tunnel. The core-to-bypass velocity ratio was set to 2:1, temperature ratio to 1.0, and pressure ratio to 1.03, giving a Reynolds number of 5.2×105, based on the core flow inlet velocity and equivalent hydraulic diameter. In the core flow, the background turbulence intensity was raised to 5% and the swirl angle was varied using five vane geometries, with nominally uniform swirl angles of 0°, 5°, 10°, 20° and 30°. Flow measurements captured flow structures involved in the mixing process. Most of mixing took place immediately downstream of the exit nozzle. The vane wake slightly enhanced large scale mixing of streamwise vortices. At low swirl angles, mixing was found to be mainly due to the interaction between streamwise vortices and normal vortices. At high swirl angles, the lobed mixer acted similar to a guide vane and removed most of the inlet swirl between the crest and trough of the mixer. However, the upstream swirling flow persisted in the core region between the center-body and lobed mixer trough, causing a reverse flow zone downstream of the centre-body. As the reversed flow became larger with increasing swirl, the swirling flow in the core region moved radially outwards and further interacted with the outer region flow. The stronger interaction of streamwise vortices with normal vortex improved mixing from the trough to the crest of the lobed mixer. The balance between enhanced mixing and increased reversed flow downstream of the centre-body, resulted in increased overall total pressure losses with increasing inlet swirl angles.
Performance Enhancement by Dynamic Valve Timing of a Multistage Vacuum Micropump
Authors: Kumar Karthik , Bernal Luis P. , Najafi Khalil
Published: May 2012

This paper presents the results of a theoretical analysis of dynamic valve timing on the performance of a multistage peristaltic vacuum micropump. Prior work has shown that for optimum steady state performance a fixed valve timing which depends on the operating pressure can be found. However, the use of a fixed valve timing could hinder performance for transient operation when the pump is evacuating a fixed volume. At the beginning of the transient the pump operates at low pressure difference and a large flow rate would be desirable. As the pump reaches high vacuum the pressure difference is large and the flow rate is necessarily small. Astle and coworkers1–3 have shown using a reduced order model that for steady state operation short valve open time results in lower inlet pressure and flow-rate and conversely. Here we extend the model of Astle and coworkers to include transient operation, multiple coupled stages and non-ideal leaky valves, and show that dynamic valve timing (DVT) reduces the transient duration by 30% compared to high vacuum pressure valve timing. The results also show a significant reduction in resonant frequency of the pump at low pressures, and quantify the effect of valve leakage.
Miniature Stereo Imaging Converter With Translating Aperture
Authors: Choi Wook , Rubtsov Vladimir , Kim Chang-Jin “C. J.”
Published: May 2012

Depth information from an image can greatly increase the work efficiency when observing or inspecting objects, because the size, distance, and relative locations can be estimated. Various stereo imaging methods are being used to find depth information in a wide range of application fields, typically by placing multiple optical systems side-by-side to create multiple shifted images. In this study, we develop a miniature stereo image generating device, which can augment an existing single optical system (i.e., a two-dimensional images capturer) with three-dimensional capability. Developed with MEMS technology, the device consists of a single translating aperture, which shifts laterally between two positions (up to 100 μm apart demonstrated) by means of electrostatic comb actuators. Attached at the objective end of conventional (i.e., nonstereo) optical systems, this stereo converter with an aperture 900 μm in diameter is shown to successfully generate slightly different viewing angles, providing stereo images. Being miniaturized, this device is suitable for microscopic or endoscopic applications, where the size of the system is limited or axial depth of focus is relatively large.
Developing a System Approach for the Engineering Technology Classroom
Authors: Fuehne Joseph P. , Sto¨ckmann Martin , Webb David
Published: May 2012

Traditional Engineering Technology classes treat various topics in isolation without ever considering a complete system. Students may learn about electrical components such as switches, fuses, solenoids, and other components in a class that never discusses how they are used in real devices and systems. Not knowing how these components connect to real systems, students have a difficult time knowing how these components fail and how that failure is manifested in the system. The system approach begins by looking at the complete system and understanding its objective. Using a solenoid as an example, students can see what the function of the solenoid is to the function of the system. They also will see what happens to the system if the solenoid doesn’t function and how the entire process is affected. At this point, the operation, functionality, properties and characteristics of solenoids are investigated. Students learn how a solenoid works, how to make measurements that would assist in troubleshooting a solenoid, and which individual parts of the solenoid could be responsible for a failure. The system approach is ideally modeled as a circle which starts and ends by looking at the system and features the details in between. Some might argue that there isn’t time in a class plan for this extra work but after doing this once or twice, the process goes rather quickly as students become familiar with it. This work will provide details of implementing this in the classroom and will provide more examples.
Implementation of a Laboratory for the Study of Robot Manipulators
Authors: Correa Julio C. , Rami´rez Juan A. , Taborda Elkin A. , Cock Jorge A. , Go´mez Manuel A. , Escobar Gustavo A.
Published: May 2012

This paper presents the process followed in the Department of Mechanical Engineering at Universidad Pontificia Bolivariana in Medellin, Colombia to implement a laboratory for the study of robot manipulators. The lab includes the following components: an industrial serial manipulator and the software developed for its integration to a graduate course, a parallel manipulator, a Cartesian robot, an inverted pendulum and a small serial manipulator. Except for the industrial robot, all the other devices were manufactured at the University. For all prototypes, specific software to control them has been developed.
Three Dimensional Simulation of Dynamics and Deformation of Red Blood Cells in Capillary Flow
Authors: Yamada Toru , Kumar Anurag , Asako Yutaka , Faghri Mohammad
Published: May 2012

A three-dimensional computational model using dissipative particle dynamics (DPD) is developed to simulate dynamics and deformation of red cells (RBC) in capillaries. DPD is able to produce correct hydrodynamics of the flow and incorporate microscopic detail of various segments of the cell. RBC is constructed using DPD particles, which are connected by a spring network to represent the membrane. The total energy of the RBC is associated with the bending energy, in-plane shear energy and the constraints of fixed area and volume. Shape optimization of swollen RBC due to continuous deflation based on the minimum energy principle is conducted to obtain the biconcave shape in equilibrium. Then, an external force is applied to the cell to study the large deformation in axial and lateral direction and compared with the experimental results. Also, RBC is placed inside a 10 μm capillary flow to study the dynamics and deformation of the cell. The cell undergoes steady deformation and acquires parachute type shape as observed in experiments.
Analytical Method to Determine the Tertiary Creep Damage Constants of the Kachanov-Rabotnov Constitutive Model
Authors: Stewart Calvin M. , Gordon Ali P.
Published: May 2012

The classic Kachanov-Rabotnov isotropic creep damage constitutive model has been used in many situations to predict the creep deformation of high temperature components. Typically, the secondary creep behavior is determined by analytical methods; however, the tertiary creep damage constants are found using a mixture of trial and error and numerical optimization. These methods require substantial hand calculations and computational time to determine the tertiary creep damage constants. In this paper, a novel analytical method is developed to determine the tertiary creep damage constants. Comparisons between numerical optimized constants and those found using the analytical method are given for a Ni-based superalloy. Creep deformation, damage evolution, and rupture time predictions are compared. A detailed discussion of the analytical method is given.
Thermoeconomic Approach to the Analysis of Energy System Control Strategies
Authors: Verda Vittorio , Baccino Giorgia
Published: May 2012

In this paper a thermoeconomic approach is applied to the dynamic model of a Power System in order to investigate the effects of the control system on the primary energy consumption. To achieve this objective, various control strategies are compared when variations of the operation condition, due to some internal or external causes, are produced. Those variations causes the intervention of the control system, which rearranges the operating condition in order to have the controlled quantities within acceptable ranges. Generally the plant efficiency changes, depending on the selected strategy. A microturbine is considered as the case study. The analysis here proposed allows one to quantify the effect of the control on the performance variation of the components. The approach associates an exergetic cost and a thermoeconomic cost to the control system operation, which expresses the additional resource (primary energy and economic resources) consumptions that may be associated to the control. The impact on the initial and final steady states as well as the transient evolution are considered.
An Experimental Study of Mechanical Behavior of Resistance Spot Welded Aluminum 6061-T6 Joints
Authors: Florea R. S. , Solanki K. N. , Hammi Y. , Bammann D. J. , Castanier M. P.
Published: May 2012

In this study, the mechanical behavior, joint characterization and process sensitivity of aluminum 6061-T6 alloy Resistance Spot Welded (RSW) joints are investigated. Tensile tests were conducted on single weld lap-shear coupons until failure in order to determine the optimum welding parameters. Welding currents, forces and times have been investigated to establish the correlation between failure loads and nugget sizes. The experimental and preliminary finite element analysis (FEA) results indicate that failure loads and nugget sizes are strongly dependent upon welding parameters and the material anisotropy.
Characterization of a Macrofiber Piezoelectric Composite for Lunar Exploration Actuator
Authors: Henslee Isaac A. , Miller David A.
Published: May 2012

Understanding the nature and locations of water and other resources on Earth’s Moon is an essential component to the National Aeronautics and Space Administration’s (NASA) space exploration efforts. To aid in these exploration efforts, an investigation into lightweight and reliable materials for a lunar actuator design has lead to characterizing the lifetime performance of the piezoelectric fiber composite, macro fiber composite (MFC). MFC’s are thin rectangular patches made of polyimide film, epoxy and a single layer of rectangular lead zirconium titanate fibers and are commercially available. As a basis for this consideration, the useful life of the MFC is being characterized to determine the effect of temperature on the performance of the material as it is fatigued by piezoelectric excitation. The patch is laminated to a cantilevered stainless steel beam and actuated at the first resonant frequency of the beam and patch laminate. Strain and beam tip displacement measurements are used as a basis for determining the performance of the MFC whichis cyclically actuated under various operating temperatures. The temperature of the beam and patch laminate is held constant during cyclic actuation, to determine the useful life of the piezoelectric patch over a temperature range from −15°C to 145°C. The experimentation efforts show a strong temperature dependence on operational life for the MFC; however, no significant degradation in operational performance was identified before ultimate failure of the MFC, regardless of temperature or actuation cycle. The results of the experimental testing can be used to design actuators using MFC in environments where operational temperatures differ from standard laboratory temperatures.
A Spring-Loaded Pole Design for Calibration of Force Platforms
Authors: Wernke Matthew M. , Lura Derek J. , Dubey Rajiv V. , Carey Stephanie L.
Published: May 2012

Gait analysis is an important tool in the diagnosis of movement disorders as well as analysis of prosthetic design and function 3D motion analysis systems frequently use a combination of motion capture cameras and force platforms (FP). Inverse dynamics can be applied to calculate various kinetic outcomes from the data these systems provide. In order for these outcomes to be accurate, it is essential these systems are calibrated properly in order to provide accurate raw data. This paper reports on a new spring-loaded pole used to determine and minimize the error in force and center of pressure (CoP) data. The spring-loaded pole consists of two short segments of Polyvinylchloride (PVC), a universal joint, two springs, a rubber tip and a handle. This spring-loaded pole improves previous instrumented pole designs by replacing expensive force transducers with an inexpensive spring, allowing for a quick analysis of a systems performance and calibration.
Design and Development of a New Valve Geometry for Spacer Devices
Authors: Oliveira Ricardo F. , Teixeira Senhorinha F. C. F. , Silva Lui´s F. , Carlos Teixeira Jose´ , Antunes Henedina
Published: May 2012

Nebulizers such as, Dry Powder Inhalers (DPI’s) and pressurized Metered-Dose Inhalers (pMDI’s), are all equally used in the treatment of asthma. For children, where the asthma incidence is high and where a good coordination between the device actuation and the respiration is needed to use the pMDI, a solution was found with the introduction of an add-on spacer to the pMDI. Because spacers attached to the pMDI are the cheapest and most efficient way to treat asthma in children, it is of the greatest relevance to improve its efficiency. This project, which concerns the study of the spacer geometry, is focused in the study, design and development of new valve geometries to enable a better delivery of the drug to the patient. This study was carried out using the Fluent™ software, from ANSYS. Once the input parameters and models were defined in order to get a realistic computational model, the geometry was optimized. This optimal solution was tested, compared and analyzed against Volumatic® valve, the spacer most widely used in the world. All the models, as well as the results obtained will be analyzed and discussed throughout the paper. It was concluded that some simple modifications, introduced on the shape of the cross-section of the valve geometry, yields radical changes in the air flow behavior. Optimizing the airflow by changing the geometry, reducing the vortex areas, will lower the waste of drug in the spacer, increasing the amount of delivery to the lung.
Guided Inquiry Learning in a Thermodynamics Class
Authors: Field Brandon S.
Published: May 2012

This paper describes guided inquiry investigations of thermodynamic properties and cycles that was used in a sophomore thermodynamics class. A partially-complete computer model of a Carnot cycle was provided to students that was written in Engineering Equation Solver (EES). The students were led through a investigation in pairs or groups using the model designed to familiarize the students with the software as well as the cycle. As part of the investigation, the students were required to modify the model to add features. Following the in-class exercise with the Carnot cycle, students were required to model a Stirling cycle and later a Brayton cycle using the same EES software for a take-home project. In previous classes, the same (and similar) take-home projects were assigned, but this was the first time that these computer projects were preceded by a guided inquiry investigation. The advantages of using such a guided inquiry investigation to introduce the software were primarily evident from the questions that were avoided on the take-home projects, but also evident from the student performance on the projects themselves. A discussion of the investigation is included, as well as critique of what will be changed for the next time the class is taught.
A Coupled-Constitutive Model for Ductile Fracture: Void Nucleation to Coalescence
Authors: Butcher Cliff , Chen Zengtao
Published: May 2012

A novel framework and integration scheme has been developed to implement a secant-based homogenization theory for particle-reinforced plasticity into an existing damage-based constitutive model, the well known Gurson-Tvergaard (GT) model. In this approach, the material is treated as a three-phase composite composed of voids and particles embedded in a ductile matrix. Two successive homogenization theories (damage- and particle-based) are then applied to determine the macro-mechanical response of the material as well as the average stress state within the constituents as a function of the particle shape, composition, and volume fraction. By identifying the stress state within the particles and the matrix, void nucleation can be accurately represented and the void growth and coalescence models are improved through knowledge of the stress state within the matrix. The performance of the coupled model is evaluated using a model aluminum alloy. A parametric study is performed to elucidate the influence of the second-phase particles and their shape on damage evolution and ductile fracture.
Numerical Optimization of Generative Network Parameters
Authors: Hummel Robert A. , Taylor Joshua A. , Hover Franz S.
Published: May 2012

We address the early design of complex, large-scale systems by viewing them as random networks and optimizing structure over their generative parameters. In this approach, we do not seek specific topologies, but rather classes of near-optimal networks which correspond to desirable statistical behavior, while also allowing flexibility to accommodate unmodeled constraints. Functionally, we perform the optimization of generative parameters on small networks (e.g., one hundred nodes) and use the results to design large networks (e.g., one thousand or more nodes). This approach is a computationally feasible forward design path for large-scale systems. A numerical example is given in which a network’s degree distribution is optimized for combined robustness and cost in a cascading failure scenario; the work has direct application to distributed communication systems.
Biomechanical, Perceptual, and Cognitive Factors Involved in Maintaining Postural Control While Standing or Walking on Non-Moving and Moving Surfaces: A Literature Review
Authors: Allen Rodowicz Kathleen , Muhammad Rahmat , Heller Michelle , Sala Joseph , Mkandawire Chimba
Published: May 2012

Postural control has been defined as “regulating the body’s position in space for the dual purposes of stability and orientation.” How the body achieves postural control depends, in part, on the environment. A person navigating a non-moving surface (e.g. hallway, stairway, or step ladder) will process information and will employ different strategies to maintain postural control than someone who is standing or walking on a moving surface (e.g., forklifts, personal transportation systems, escalators, and moving walkways). In both environments, sensory, cognitive, and motor control systems contribute to postural control. The musculoskeletal system uses muscle activation and joint positioning to control the body’s alignment and muscle tone. The biomechanics of postural control rely on information that the musculoskeletal system receives from sensory systems including the vestibular system, which is generally implicated in behaviors requiring balance control, as well as the somatosensory and visual systems. Furthermore, sensory information from these and other systems can be enhanced by cognitive processes, such as attention. The ability to maintain postural control while standing or walking is critical in preventing falls on both non-moving and moving surfaces. This review focuses on moving surfaces and includes a discussion of the biomechanical, perceptual, and cognitive factors responsible for postural control.
Experimental Technique for Sensing Droplet Position in Digital Microfluidic Systems Using Capacitance Measurement
Authors: Martin Heather , Murran Miguel , L’Orsa Rachael , Najjaran Homayoun
Published: May 2012

Capacitance measurement has been identified as an effective technique for droplet position sensing in digital microfluidic systems mainly due to its non-intrusive nature. In essence, this technique relies on the correlation between the capacitance of two top-bottom electrodes with the amount of droplet overlap on the electrode. This paper describes an experimental setup used to gather capacitance data from a set of electrodes with varying droplet overlap to determine the droplet position. A prototype closed digital microfluidic (DMF) system consisting of an array of electrodes in the form of a 2 × 2 matrix was fabricated. A circular droplet was positioned on the DMF system, and capacitance measurements for each of the four electrodes were taken using a fast data acquisition device. A sufficiently accurate approximation of the droplet position was made using the four capacitance measurements. The paper presents the experimental results and also discusses the sources of error, viability of the experimental setup and manufacturing procedure for use in the development of capacitance measurement droplet position sensing techniques.
Reliable Design of Electroplated Copper Through Silicon Vias
Authors: Liu Xi , Chen Qiao , Sundaram Venkatesh , Muthukumar Sriram , Tummala Rao R. , Sitaraman Suresh K.
Published: May 2012

Through-silicon vias (TSVs), being one of the key enabling technologies for 3D system integration, are being used in various 3D vertically stacked devices. As TSVs are relatively new, there is not enough information in available literature on the thermo-mechanical reliability of TSVs. Due to the high coefficient of thermal expansion (CTE) mismatch between Si and the Cu vias, “Cu pumping” will occur at high temperature and “Cu sinking” will occur at low temperature, which may induce large stress in SiO2, interfacial stress at Cu/SiO2 interface and plastic deformation in Cu core. The thermal-mechanical stress can potentially cause interfacial debonding, cohesive cracking in dielectric layers or Cu core, causing some reliability issues. Thus, in this paper, three-dimensional thermo-mechanical finite-element models have been built to analyze the stress/strain distribution in the TSV structures. A comparative analysis of different via designs, such as circular, square, and annular vias has been performed. In addition, defects due to fabrication such as voids in the Cu core during electroplating and Cu pad undercutting due to over-etching are considered in the models, and it is seen that these fabrication defects are detrimental to TSV reliability.
Biomechanical, Perceptual, and Cognitive Factors Involved in Balance Recovery Following Unexpected Perturbations: A Literature Review
Authors: Muhammad Rahmat , Allen Rodowicz Kathleen , Heller Michelle , Sala Joseph , Mkandawire Chimba
Published: May 2012

For an individual standing or walking on a moving or non-moving surface, perturbations can result in postural instability and sudden loss of balance. When unexpected perturbations occur, specific mechanisms involving the sensory, cognitive, and motor systems activate in order to regain postural control. For example, specific muscle synergies can result in compensatory limb movements (e.g. stepping or reaching towards a fixed object) that are prevalent mechanical responses to sudden loss of balance and play a crucial role in preventing falls. These movements require the interaction of multiple sensory systems including the visual, somatosensory, and vestibular systems. If sensory information is unavailable or incomplete, there may be a greater reliance on cognitive processes such as memory and attention in order to execute a balance-recovering mechanical response; however, if cognitive processes are tasked, compensatory responses may be negatively affected. The ability to recover from sudden loss of balance is critical in preventing falls on both non-moving and moving surfaces. This review includes a discussion of the biomechanical, perceptual, and cognitive factors responsible for the control of balance recovery on moving surfaces.
Application of Digital Imaging Techniques in Detection of Defects in Thin Plywood
Authors: Mojtahed Masoud , Mourillon Joslin , Riley Adam
Published: May 2012

The detection of flaws and cavities in thin plywood boards saves money for manufactures of a variety of products. Flaws in the boundaries of pieces cut from plywood makes them useless. Therefore, it is essential to detect and locate knots and flaws in plywood boards before the cutting process. A detection and locating system was developed to detect knots and cavities in thin plywood boards using Digital Image Processing and light enhancement methods. The system comprises of three major components: a light source, a digital camera and a computer. The intense light source is used to brighten and reveal flaws and defects in the plywood board in an apparatus. The digital camera captures a digitized picture of the lighted board and stores it on the computer. Finally, a program written in Matlab™ code analyzes the captured image of the board, compares it to a template, and indicates whether flaws are located on the template’s cut lines. The advantage of using these methods is that it allows for the examination and analysis of the plywood without compromising its integrity. When a flaw is detected, the system repositions the plywood image in search of finding an orientation that will allow all defects to avoid cut lines. The process is repeated against several templates until the correct match is found. Once the match and usable orientation is found, a prompt will appear on the computer screen telling the system operator the template name and the orientation of the plywood board.
Design of a Micro-Scale Magnetostrictive Asymmetric Thin Film Bimorph (µMAB) Microrobot
Authors: Jing Wuming , Chen Xi , Lyttle Sean , Fu Zhenbo , Shi Yong , Cappelleri David J.
Published: May 2012

This paper presents the design, analysis, and performance results for a mobile microrobot that was designed for competing in the 2010 NIST Mobile Microrobot Challenge. Inspired by a crab-like microrobot driven by pulsating cardiomyocyte cells, an asymmetrically dimensioned magnetostrictive thin film bimorph microrobot has been designed. Utilizing the magnetostrictive principle, different bending and blocking forces occur under the robot’s feet due to the in-plane strain generated in the bimorphs by the application of external magnetic fields in the workspace of the microrobot. The differences in the resulting frictional forces drive the movement of the robot body. To calculate and simulate whether the feet of the robot can generate enough force for locomotion, the design was abstracted and translated into a piezoelectric cantilever FEM model. The results are consistent with the magnetostrictive theoretical equations. Microrobot fabrication and test-bed development based on this analysis is shown along with experimental results validating this approach. Finally, a discussion of the performance results and recommendations for future improvements are provided.
Mechanoevolution: The Possibility of Deeper Connections Between Information Theory and the Second Law
Authors: Layton Bradley E.
Published: May 2012

Entropy, S is an extensive physical property with dimensions of energy per Kelvin. Information, I is an extensive mathematical metric with units of bits. If we consider discrete living systems such as individual organisms as well as discrete technological systems such as hand tools, automobiles, and computers as systems that maintain both a quantifiable specific energy throughput, φ and a quantifiable information throughput, I˙m at the expense of entropy production, S˙, we can then begin to build a formal relationship among these three variables within organic, synthetic and hybrid systems. The combination of mass-specific energy and information throughput within a system results in a local partitioning of entropy: local entropy diminution causes global entropy acceleration. In general, as the symbioses between humans and machines become more tightly bound through a process termed “mechanoevolution,” the respective rates of information throughput, energy throughput, and thus entropy production accelerate towards a yet unknown limit.
Design Construction and Test of a Subscale Ammonia Borane Reactor
Authors: Deshpande Kedaresh A. , Voskuilen Tyler G. , Basu Sumit , Zheng Yuan , Pourpoint Timothe´e L. , Gore Jay P.
Published: May 2012

Two ammonia borane (AB or NH3BH3) dehydrogenation routes, namely hydrolysis and thermolysis, have been described in the literature. The work done on design, construction and testing of a subscale AB reactor is reported herein along with a discussion on the results. In this work, an AB dehydrogenation reactor system capable of handling two grams of AB per batch was designed. Operational safety, material compatibility and manufacturability were the major design requirements. The reactor system consisted of a high pressure feeder, a cylindrical stainless steel reactor vessel, an evolved gas heat exchanger and an ammonia filter, and a hydrogen flow meter. The reactor was operated in a temperature range of 430 K to 445 K for a nominal batch reaction time of 30 minutes. Measurements of hydrogen yield rates, system storage capacity and analysis of the reaction kinetics were completed. Overall repeatability of hydrogen yields was confirmed. A few practical problems associated with byproduct formation and removal are discussed in this paper.
Evidence of Coulomb Friction Damping in Graphene Nanocomposites
Authors: Scarton H. A. , Kahn I. , Rafiee M. A. , Rafiee J. , Wilt K. , Koratkar N.
Published: May 2012

Polymer nanocomposites reinforced by carbon nanotubes, fullerene and nanoparticles have been broadly studied within the last two decades. However, it was recently observed that polymer nanocomposites filled with graphene sheets showed exceptional mechanical and electrical properties. The advantage of graphene sheets over carbon nanotubes in nanocomposites may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface as well as the two-dimensional geometry of graphene sheets. We have compared the vibration damping properties of epoxy nanocomposite filled with single-walled carbon nanotubes (SWNT), multi-walled nanotubes (MWNT), and graphene platelet (GPL) fillers. Our results show the evidence of Coulomb friction damping in nanocomposites comparing with the pure epoxy.
Optimal Viscous Damper Placement Using Level Set Topology Optimization Method
Authors: Ansari Masoud , Khajepour Amir , Esmailzadeh Ebrahim
Published: May 2012

Vibration control has always been of great interest for many researchers in different fields, especially mechanical and civil engineering. One of the key elements in control of vibration is damper. One way of optimally suppressing unwanted vibrations is to find the best locations of the dampers in the structure, such that the highest dampening effect is achieved. This paper proposes a new approach that turns the conventional discrete optimization problem of optimal damper placement to a continuous topology optimization. In fact, instead of considering a few dampers and run the discrete optimization problem to find their best locations, the whole structure is considered to be connected to infinite numbers of dampers and level set topology optimization will be performed to determine the optimal damping set, while certain number of dampers are used, and the minimum energy for the system is achieved. This method has a few major advantages over the conventional methods, and can handle damper placement problem for complicated structures (systems) more accurately. The results, obtained in this research are very promising and show the capability of this method in finding the best damper location is structures.
Fast Solutions for the Fiber Orientation of Concentrated Suspensions of Short-Fiber Composites Using the Exact Closure Method
Authors: Montgomery-Smith Stephen , Jack David A. , Smith Douglas
Published: May 2012

The kinetics of the fiber orientation during processing of short-fiber composites governs both the processing characteristics and the cured part performance. The flow kinetics of the polymer melt dictates the fiber orientation kinetics, and in turn the underlying fiber orientation dictates the bulk flow characteristics. It is beyond computational comprehension to model the equation of motion of the full fiber orientation probability distribution function. Instead, typical industrial simulations rely on the computationally efficient equation of motion of the second-order orientation tensor (also known as the second-order moment of the orientation distribution function) to model the characteristics of the fiber orientation within a polymer suspension. Unfortunately, typical implementation forms of any order orientation tensor equation of motion requires the next higher, even ordered, orientation tensor, thus necessitating a closure of the higher order expression. The recently developed Fast Exact Closure avoids the classical closure problem by solving a set of related second-order tensor equations of motion, and yields the exact solution for pure Jeffery’s motion as the diffusion goes to zero. Typical closures are obtained through a fitting process, and are often obtained by fitting for orientation states obtained from solutions of the full orientation distribution function, thus tying the closure to the flows from which it was fit. With the recent understandings of the limitations of the Folgar and Tucker (1984) model of fiber interactions during processing, it has become clear the importance of developing a closure that is independent of any choice of fitting data. The Fast Exact Closure presents an alternative in that it is constructed independent of any fitting process. Results demonstrate that when diffusion exists, the solution is not only physical, but solutions for flows experiencing Folgar-Tucker diffusion are shown to exhibit an equal to or greater accuracy than solutions relying on closures developed via a curve fitting approach.
Effective Modelling of Sticking Motions in Vibro-Impacting Continuous Systems
Authors: Vyasarayani Chandrika P. , Sandhu Sukhpreet Singh , McPhee John
Published: May 2012

In this work we propose a new methodology to simulate sticking motions occurring in vibro-impacting continuous systems. We have developed this method in the framework of the coefficient of restitution approach. During the sticking phase, the sticking constraints are imposed exactly using a Lagrange multiplier, which represents the reaction between the continuous system and the obstacle. The expression for the Lagrange multiplier is developed in closed form. The proposed method does not require the mode-shapes during the sticking phase, unlike the mode-switching method. The developed methodology is supported by illustrative numerical simulations.
Human Aorta Buckling Related to Dissection
Authors: Karagiozis Kostas , Amabili Marco , Mongrain Rosaire , Cartier Raymond , Pai¨doussis Michael P.
Published: May 2012

Human aortas are subjected to large mechanical stresses and loads due to blood flow pressurization and through contact with the surrounding tissue and muscle. It is essential that the aorta does not lose stability for proper functioning. The present work investigates the buckling of human aorta relating it to dissection by means of an analytical model. A full bifurcation analysis is used employing a nonlinear model to investigate the nonlinear stability of the aorta conveying blood flow. The artery is modeled as a shell by means of Donnell’s nonlinear shell theory retaining in-plane inertia, while the fluid is modelled by a Newtonian inviscid flow theory but taking into account viscous stresses via the time-averaged Navier-Stokes equation. The three shell displacements are expanded using trigonometric series that satisfy the boundary conditions exactly. A parametric study is undertaken to determine the effect of aorta length, thickness, Young’s modulus, and transmural pressure on the nonlinear stability of the aorta. As a first attempt to study dissection, a quasi-steady approach is taken, in which the flow is not pulsatile but steady. The effect of increasing flow velocity is studied, particularly where the system loses stability, exhibiting static collapse. Regions of large mechanical stresses on the artery surface are identified for collapsed arteries indicating possible ways for dissection to be initiated.
Exploratory Analysis of Aggregate Power Metrics in Data Centers
Authors: Marwah Manish , Arlitt Martin , Hoover Christopher , Bash Cullen , Sharma Ratnesh K.
Published: May 2012

In recent years, climate change, depletion of conventional energy sources and rising energy costs have led to an increased focus on sustainability. Within the Information Technology (IT) sector, data centers are significant energy consumers. The first steps towards reducing power consumption in data centers are to monitor it and to determine the heavy hitters. Unfortunately, fine-grain power information is often not readily available within data center environments. In this paper, we conduct an exploratory analysis of aggregate power data in a data center. We collect data from the power infrastructure of a data center in Palo Alto, CA, as well as from a data center in Bangalore, India. We examine the data in increasing detail, and reveal the opportunities and challenges for disaggregating data center power consumption data.
Second Law Based Optimization of Micro Gas Turbine (MGT) Cycle for Residental Application Using a Genetic Algorithm
Authors: Enadi N. , Ahmadi P. , Atabi F. , Heibati M. R.
Published: May 2012

Exergoeconomic analysis helps designers to find ways to improve the performance of a system in a cost effective way. Most of the conventional exergoeconomic optimization methods are iterative in nature and require the interpretation of the designer at each iteration. In this work, a cogeneration system that produces 50MW of electricity and 33.3 kg/s of saturated steam at 13 bars is optimized using exergoeconomic principles and evolutionary programming such as Genetic algorithm. The optimization program is developed in Matlab Software programming. The plant is comprised of a gas turbine, air compressor, combustion chamber, and air pre-heater as well as a heat recovery steam generator (HRSG).The design Parameters of the plant, were chosen as: compressor pressure ratio (rc), compressor isentropic efficiency (ηac), gas turbine isentropic efficiency (ηgt), combustion chamber inlet temperature (T3), and turbine inlet temperature (T4). In order to optimally find the design parameters a thermoeconomic approach has been followed. An objective function, representing the total cost of the plant in terms of dollar per second, was defined as the sum of the operating cost, related to the fuel consumption. Subsequently, different pars of objective function have been expressed in terms of decision variables. Finally, the optimal values of decision variables were obtained by minimizing the objective function using Evolutionary algorithm such as Genetic Algorithm. The influence of changes in the demanded power on the design parameters has been also studied for 50, 60, 70 MW of net power output.
Effect of Core-Shell Structure of Hydrogel Beads on the Threshold Concentration of Water for Swelling and its pH Sensitivity
Authors: Bhadra Jolly , Nampoothiri Pramod K. , Suthar Kamlesh J. , Roy Mahapatra D.
Published: May 2012

In this paper we investigate the effect of core-shell structure of Sodium Alginate based hydrogel beads and their size on certain activation threshold concentration of water for applications in swelling and pH sensing. This type of hydrogel experiences diffusive pressure due to transport of certain free charges across its interface with a solvent or electrolyte. This process is essentially a dynamic equilibrium of the electric force field, stress in the polymeric network with cage like structure and molecular diffusion including phase transformation due to pressure imbalance between the hydrogel and its surroundings. The effect of pH of the solvant on the swelling rate of these beads has been studied experimentally. A mathematical model of the swelling process has been developed by considering Nernst–Planck equation representing the migration of mobile ions and H+ ions, Poisson equation representing the equilibrium of the electric field and mechanical field equation representing swelling of the gel. An attempt has been made to predict the experimentally observed phenomena using these numerical simulations. It is observed experimentally that certain minimum concentration called activation threshold concentration of the water molecules must be present in the hydrogel in order to activate the swelling process. For the required activation threshold concentration of water in the beads, the pH induced change in the rate of swelling is also investigated. This effect is analyzed for various different core-shell structures of the beads.
Initial Results From an Interdisciplinary Review of Trust Research
Authors: Hall Simin , McQuay William , Ball Kenneth S.
Published: May 2012

In the days of modern engineering, a complex system can be designed and built using numerous sources of information, knowledge, hardware, and software. A factor that impacts the success of a complex system is trust. In designing a framework that allows for a unified trust model or trusting picture and defining a reliable metric for measuring trustworthiness, we are examining definitions and methodologies from social sciences and engineering. This paper uses a combination of publication analysis of research literature including psychological, sociological, economic, automation, and cyberspace perspectives of trust and technical dialogues with the subject matter experts at the Air Force Research Laboratory, to illuminate the interdisciplinary approach undertaken in hardware centric design with human interface. We review past work to highlight trustworthiness characteristics and trust measurements that conceptually could apply across fields under examination. We expect to create a more rigorous definition of trust and trustworthiness that leads to finding the appropriate metrics to measure trust and trustworthiness dynamically.
Enhanced Output Voltage and Power From Conductive Inclusions in a 0-3-0 Piezoelectric Composite
Authors: Cook-Chennault K. A. , Cosaboon D. , Eigbe D. , Pitcavage B. , Whitzer M. , Castley D.
Published: May 2012

The results for a feasibility study on the inclusion of aluminum particles within cement/PZT composites are presented. The influence of aluminum on output voltage and power is investigated, which has not been done for piezoelectric-cement composites before. In the experiments, the amount of PZT was held constant at 50% (by volume), while the aluminum content was varied, 0%, 5% and 10% volume. The samples were subjected to g-loads that ranged from 0.5–2.0 g’s and frequencies between 200 and 250 Hz, while a resistive load of 1 ohm was applied to determine output power. The output power from samples containing 5% and 10% aluminum, produced ∼3.5 and ∼5.8 times more output power than samples containing only PZT and cement. We have also demonstrated that aluminum/PZT/Cement composites can be fabricated using a mix and cold-compression method.
Methodology for Estimation of Life Cycle Orientated Optimizatation Measures of Investment Goods
Authors: Nass Susanne , Sprenger Andre , Anderl Reiner
Published: May 2012

A manufacturer of any kind of product has to be in contrast to competitive to survive on market. A major point to win a customer over is the arrangements of costs. In investment goods industry asset cost are just the tip of the iceberg. Most of their costs accrue by use. Because of that it is important to overview the whole costs of the product life cycle. Product life cycle costs describe the cost of a product over its whole life. This includes all expenses from development, production and use to recycling and refers to manufacturer and customer equally. The majority of costs are determined in the stages of product development. As a manufacturer of complex investment goods (e.g. machine for production) the question of new development investments has to be answered. There are three important dimensions to consider. These dimensions concern the right part of product for improvement, the right kinds of costs and the owner of these costs. In detail they have to decide which part of product should be improved to get the main effect concerning reduction of life cycle costs. But in that case it is also important to know what kinds of costs of the chosen part have to be reduced (for example energy cost, cost for maintenance or repair). The third dimension in case of product life cycle costs aims at the owner of the cost, manufacturer or customer. This is a problem when new developments cause savings on one side but expenses for the other. In that context the best leverage of these combinations is searched for which means that exactly this kind of costs has to be identified, whose savings get the biggest benefit in relation to necessary expenses. This paper presents an approach to address this problem. For the pre-selection of possible functions established methods derived from product development are used in this context. Afterwards a procedure of quantification is presented. Calculation and rating of new defined management ratios provide the biggest leverage in order to reduce the product life cycle costs. This approach represents an instrument for manufacturer’s business of investment goods to make decisions about their future investments in the field of product development.
Concept Design for a Composite Manufacturing Robot
Authors: Tadros Michael M.
Published: May 2012

Manufacturing of advanced composite test specimens and small parts in a research lab environment is often done by hand lay-up. Associated drawbacks include errors in stacking sequence, ply angles, geometry and material waste. The manufactured specimens are often used for testing and concept validation and as such should be representative of parts manufactured using fully automated processes resulting in a finished part with significantly higher quality and geometric tolerances. To this end, a concept design for a manufacturing robot has been developed and constructed. The robot suits the needs of a research lab environment size wise and rate and number of manufactured parts from pre-impregnated tape materials. Details of the concept design, manufacturing, control and operation are provided. An assessment of the robot versatility, portability versus cost is presented.