bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of a Small Scale Pellet Boiler
Authors: Teixeira Jose´ Carlos , Ferreira Rui , Ferreira Manuel Eduardo
Published: May 2012

Environmental concerns and the drive to reduce the dependence on petroleum based fuels brought the use of renewable energies to the forefront. Biomass appears as a very interesting option for direct conversion into heat. In this context, densified forms of biomass such as pellets are of great relevance because of their easy of use, high efficiency and low emissions. Expected trends in the biomass market suggest that equipments should operate over a wide range of thermal loads and with fuels derived from lower quality raw materials; simultaneously, a high efficiency and low emissions are taken for granted. Currently, biomass domestic boilers prove to be very sensitive to fuel characteristics and load conditions. This work reports on the development of a 15 kW net pellet boiler. A prototype was built that enables the independent control of the air supply into various regions of the combustion chamber and an accurate supply of fuel. The test rig also includes: boiler and flue gases extraction system; feeding system; heat dissipation system; flue gas analyzer; data acquisition system and all sensors. In order to optimize the combustion conditions, pollutant emissions and their relation with feeding conditions, primary and secondary air flow rate and excess of air was analyzed. The results suggest that this burner is a promising for implementation in domestic boilers. The advantages are: CO emissions well below those observed in similar equipments and the capacity to maintain the emissions level constant under different loading conditions.
Cow Power to Horsepower: Building a Pilot Plant to Operate a Bus on Dairy Cow-Derived Biomethane
Authors: Leonhardt Eric , Vos Ben , Riels Richard
Published: May 2012

A pilot facility to capture, upgrade and compress biomethane from a dairy cow-based anaerobic digester is being constructed by the Western Washington University Vehicle Research Institute at the Vander Haak Dairy. A faculty and student team has designed the facility and undertaken its construction. The facility will provide fuel for an Airporter Shuttle/Bellair coach that will operate along the U. S. Interstate 5 corridor from near the U. S./Canadian border to the SeaTac Airport south of Seattle, Washington. The facility is designed to study and develop a renewable energy source for transportation in Whatcom County. This paper examines the benefits of the Biomethane for Transportation project, the challenges facing dairy-derived biomethane and an overview of the system design and construction.
Numerical Investigation of Aerodynamic Performance of a Three-Bladed Vertical Axis Wind Turbine
Authors: Untaroiu Alexandrina , Barker Lydia R. , Wood Houston G. , Ribando Robert J. , Allaire Paul E.
Published: May 2012

As a pollution free source of energy, wind is among the most popular and fastest growing forms of electricity generation in the world. Compared to their horizontal axis counterparts, vertical axis wind turbines have lagged considerably in development and implementation. The University of Virginia Rotating Machinery and Controls laboratory has undertaken a systematic review of vertical axis wind turbine design in order to address this research gap, starting with establishment of a methodology for vertical axis wind turbine simulation using ANSYS CFX. A 2D model of a recently published Durham University vertical axis wind turbine was generated. Full transient CFD simulations using the moving mesh capability available in ANSYS-CFX were run from turbine start-up to operating speed and compared with the experimental data in order to validate the technique. A scalable k-ε turbulence model transient CFD simulation has been demonstrated to accurately predict vertical axis wind turbine operating speed within 12% error using a two-dimensional structured mesh in conjunction with a carefully specified series of boundary conditions.
A Dielectric Liquid Contact Thermal Switch With Electrowetting Actuation
Authors: McLanahan Aric L. R. , Richards C. D. , Richards R. F.
Published: May 2012

In this paper we present the design, fabrication, and preliminary characterization of a MEMS thermal switch. The thermal switch operates by changing the conductive path between two silicon die by moving a dielectric liquid, such as glycerin or water, using electrowetting. The result is a bi-stable thermal switch that can change between a low thermal resistance state and a high thermal resistance state. Preliminary measurements show the switching time to be on the order of a second. Numerical modeling indicates a thermal resistance ratio of Roff/on > 25 is feasible with a power consumption in the low micro-watt range.
Heat Transfer Enhancement Induced by Cube- and Diamond-Shaped Block Arrays in Two-Pass High-Aspect Ratio Channels With a 180-Degree Turn
Authors: Ganmol Pavin , Chyu Minking K.
Published: May 2012

Described in this paper is an experimental investigation of the heat transfer and pressure characteristics in a high aspect ratio, (4.5:1 width-to-height), two-pass channel, with cube-shaped and diamond-shaped block arrays placed in both passes before and after a 180-degree sharp turn. Transient liquid crystal technique was applied to acquire detailed local heat transfer data on both the channel surfaces and the block elements. Reynolds number tested varies between 13000 and 28000. To further explore potential design alternatives for enhancement cooling, the effects of block height, ranging from 1/4, 1/2, 3/4 and full span of the channel height were also evaluated. Present results suggest that a staggered cube-array can enhance heat transfer rate up to 3.5 fold in the first pass and about 1.9 fold in the second pass, relative to the fully-developed smooth channel counterpart. For the corresponding diamond-shaped block array, the enhancement is 3.4 and 1.9 fold respectively. Even though the post-turn turbulence transport in the second pass is generally higher than that in the first pass, the effects of surface-block induced heat transfer enhancement in fact are less prominent in the post-turn region of the second pass. Pressure loss for diamond block arrays is generally higher than that of the corresponding cube-block arrays.
Soft Tissue Characterization Using One Dimensional Lumped Mass-Spring-Damper Model
Authors: Zahiri-Azar Reza , Baghani Ali , Salcudean Septimiu , Rohling Robert
Published: May 2012

The characterization of tissue mechanical properties, such as its elasticity and viscosity, has proven to be useful in numerous clinical applications. For this reason, several techniques have been suggested in the literature to provide non-invasive estimates of these properties. Common to all these technique, an external or internal source is used to deform the tissue. The response of the tissue to this deformation is then measured and used to estimate its mechanical properties.
Temperature-Weighted Assessment of Waste Heat Availability With Matched End-Use Applications for Optimal Primary Energy Usage in the USA
Authors: Rattner Alexander S. , Garimella Srinivas
Published: May 2012

Approximately two-thirds of all input energy used for power and electricity generation in the USA is lost as heat during conversion processes. Additionally, 12.5% of primary fuel and 20.3% of the electricity generated through these processes are employed for space heating, water heating, and refrigeration where low-grade heat could suffice. The potential for harnessing waste heat from power generation and thermal processes to perform these low-grade tasks is assessed here. By matching power plant outlet streams with applications at corresponding temperature ranges, this study identifies sufficient waste heat to satisfy all residential, building, and manufacturing space and water heating needs. Sufficient high temperature exhaust from power plants is identified to satisfy 27% of residential air conditioning demand with thermally activated refrigeration or all industrial low temperature (100–150°C) process heating and refrigeration needs. Exhaust from vehicle engines is sufficient to satisfy all in-vehicle air conditioning and 68% of electricity generation demand. Energy usage and waste heat availability and application information collected for this study is compiled in a thermodynamically informed database. By providing SQL queries, this database can answer detailed questions about energy sources and demands delineated by temperature, energy scale, process, and location. This capability can inform future infrastructure and development to effectively capture waste heat that would be lost today, substantially reducing the USA national energy intensity across all end uses.
Investigation of the Blood Flow and Mitral-Septal Opposition in the Left Ventricle With the Obstructive Hyperthrophic Cardiomyopathy During Systole Using Fluid-Structure Interaction Technique
Authors: Moghaddaszade Kermani Ahmad , Suleman Afzal
Published: May 2012

In this article, fluid-structure interaction methodology was used to analyze the blood flow and Mitral-Septal opposition in the Left ventricle with the Obstructive Hyperthrophic Cardiomyopathy (OHCM). The geometry of the computational model includes the diseased left ventricle with thickened septum and Mitral valve. A semi-ellipsoidal geometry was developed with the dimensions, extracted from MR images of the diseased left ventricle. Also, the geometry of the Mitral valve was created using anatomical data provided in literature [1]. The three element Windkessel model and atrial pressure [2, 3] were used to introduce mass flow and pressure boundary conditions to the aortic orifice and left atrium respectively. Effect of the fibers was taken into account by varying the Young’s modulus of the mitral valve tissue with circumferential and radial coordinates. The fluid-structure interaction algorithm started at the beginning of the systole (when the mitral valve is fully open with zero stress) by applying the left ventricular pressure on the left ventricular wall and aortic mass flow outlet on the aortic orifice. The Navier-Stokes equations were solved with SIMPLE algorithm and finite volume method to calculate the blood flow inside the diseased left ventricle. The calculated pressure was applied to the surface of the mitral valve and the structural model of the tissue was solved using non-linear finite element. The deformation of the mitral valve was transferred to the blood by moving the fluid mesh. In the next time step, the same procedure was repeated with the new mesh. This algorithm was followed up to the end of the systole. The thickened septum creates a narrow passage for the blood flowing out of the left ventricle, thus a jet of blood flow is developed in this narrow passage which applies high shear stress on the anterior leaflet of the mitral valve. The drag force deforms the anterior leaflet toward the septum, obstructing the blood flow rushing toward the aortic orifice.
Analysis of the X-Ray Imaged Solid Oxide Fuel Cell Anode Microstructure
Authors: Nelson George J. , Grew Kyle N. , Peracchio Aldo A. , Izzo John , Chiu Wilson K. S.
Published: May 2012

Solid oxide fuel cell (SOFC) anodes are comprised of heterogeneous functional materials that include a pore phase which supports gas transport and solid phases which support ionic and electronic charge transport. A more detailed understanding of the contributions each of these phases makes to overall anode performance is critical for the design and development of next generation SOFCs. In the present work, three dimensional tomographic reconstructions of SOFC anodes are addressed with consideration given to the characterization of distinct pore, ionic and electronic conducting phases. These reconstructions are produced from transmission x-ray microscope (TXM) images taken at 38 nm spatial resolutions. Elemental mapping enabled by the TXM is used to determine the distribution of pore and solid ionic and electronic conducting phases within the anode. The results presented provide key insights into the composition and morphology of SOFC microstructures. The application of x-ray computed tomography (XCT) to ex situ SOFC micrsostructural characterization is demonstrated, and further applications of this technique are discussed.
Lifecycle-Based Data Center Design
Authors: Meza Justin , Shih Rocky , Shah Amip , Ranganathan Parthasarathy , Chang Jichuan , Bash Cullen
Published: May 2012

Environmental sustainability is an increasingly important design constraint for next-generation servers and datacenters. Unlike prior studies that focus on operational energy use, we study the environmental impact of current designs across the entire lifecycle, including embedded impact factors related to material use and manufacturing. Based on the insights provided by this study, we propose a solution co-designed across system architecture and physical packaging, including (1) material-efficient physical organization, (2) environmentally-efficient cooling infrastructures, and (3) effective design of system architectures to reuse components — all working together to improve sustainability. We provide a detailed evaluation of our proposed solution in terms of sustainability, thermal manageability, and computational performance. Our results show that the proposed approach is effective in addressing the (often non-intuitive) tradeoffs between performance and different components of sustainability.
Signaling Pathways for Bone Resorption Predicted as a Hybrid Cellular Automaton Process
Authors: Penninger Charles L. , Tovar Andre´s , Niebur Glen L. , Renaud John E.
Published: May 2012

The bone remodeling process provides for various functions such as mineral homeostasis, damage repair, and adaptation to mechanical loading. At present, a clear link between the mechanical stimulation of bones and the biochemical response is not fully understood. Computational simulations can provide a means to test hypotheses and gain insight into processes that are difficult to examine experimentally. The objective of this work is to predict the effect of damage and strain as the stimulus for regulating the cellular signaling activity of remodeling. In this study, potential signaling pathways that mediate this cellular activity were incorporated in a hybrid cellular automaton (HCA) algorithm. Biological rules were implemented in this model to control recruitment, differentiation, and activation of osteoclasts. Prominent processes for describing recruitment and inhibition of the bone cells, as reported from experimental studies, are utilized. This work focuses on the resorption of a damaged site on a trabecular strut.
Mechanical Characterization of Preterm Neonate Pig Liver as a Function of High-Density Lipoprotein (HDL)
Authors: Roan Esra , Bada Alex , Buddington Randy
Published: May 2012

Elastography, a non-invasive imaging modality, utilizes mechanical properties of tissue as markers for disease diagnosis or staging. In the case of liver, there have been a number of studies focusing on the relationship between elastic mechanical properties and underlying disease, i.e. fibrosis and cirrhosis. In summary, these studies indicate the feasibility of elastographic tools in detecting liver diseases such as fibrosis and steatosis. There have not been any studies looking at the mechanical properties of the preterm neonate liver to date, which is important, because preterm neonates are at a greater risk for developing liver complications due to their aggressive dietary needs that are met with total parenteral nutrition (TPN). They use of elastography may be less from the use of elastographic tools since the concerns over noise levels in measurements resulting from abdominal wall thickness may be less influential. Therefore, it is necessary to establish basic preterm neonate liver mechanical properties. In this study, we measured the nonlinear (hyperelastic) mechanical properties of livers from preterm pigs that were fed common neaonatal diets, i.e. colostrum, total parenteral nutrition (TPN). 16 neonate pigs survived the feeding regime. Mechanical evaluation of 15 of these neonatal pigs was achieved with the use of uniaxial compression experiments at 0.01 s−1 strain rate. The livers averaging a weight of 34.7±7.0 (SD), were stored in phosphate buffered saline solution at 4°C until experimentation, which occurred within 30 minutes of the animal sacrifice. A minimum of three specimens from each liver was required for the computation of averaged mechanical properties. In addition to mechanical testing samples, blood serum was also obtained from these animals and common chemical parameters for liver health were measured (bilirubin, ALT, AST, HDL, LDL, etc.) Exponential form of the hyperelastic strain energy function, W = b1exp[b2(L2 + 2/L-3)], where bi are the material parameters and L is the stretch ratio, was utilized to describe the hyperelastic mechanical behavior of the preterm neonate pig livers. With the use of E = 6b1b2, a small-strain regime estimate of the elastic modulus of the neonate liver tissue was also computed. The mean b1 and b2 parameters are determined to be 97.00±44.15(SD) Pa and 1.90±0.28(SD) (n = 71). The mean elastic modulus exhibited an linear dependence on the HDL values obtained from chemical analysis of the blood serum. Moreover, although relatively weak, the ratio of the HDL over LDL also correlated with the elastic modulus. To our knowledge, this is the only study to date that has focused on the mechanical properties of preterm neonatal pigs and its correlation with liver lipid profile in neonates. Future work will focus on correlating this information with histology and then devising multi-scale material characterization approaches that link underlying neonatal liver structure to its overall mechanical properties.
Interfacial Improvement of Nanophased Jute-Based Green Composite by Surface Modification
Authors: Hossain Mohammad K. , Dewan Mohammad W. , Hossain Muhammad E. , Hosur Mahesh , Jeelani Shaik
Published: May 2012

The extensive research efforts are currently on progress all over the world to develop and characterize the green composites with high performance at an affordable cost due to the growing environmental awareness. Biodegradable nanophased jute composites were manufactured using chemically treated jute fabrics, Biopol, and nanoclay using compression molding techniques for this study. Nanoclay infusion into the thermoplastic is a challenging issue and was infused using solution intercalation technique. The surface modification of jute fibers was accomplished by performing subsequent chemical treatments such as detergent washing, dewaxing, alkali and acetic acid treatment. The morphology of the modified surface was studied using SEM and FTIR. Thermal performance of the treated fibers was studied using the TGA. The thermal, dynamic mechanical and mechanical properties of biodegradable nanophased jute composites were evaluated by TGA, DMA and flexure test respectively. Enhanced thermal and mechanical properties were observed in modified and nanophased jute biopol composites.
A Comparative Study to Measure Audible Release (Crepitus) From Human Joints
Authors: Grewal Parvind Kaur , Mansour Hossein , Arzanpour Siamak , Golnaraghi Farid
Published: May 2012

Non-impulse and Impulse based therapy approaches are often preferred over surgery because they are non-invasive. These techniques are often accompanied by audible release (crepitus) from the human joints. The sounds emitted by a damaged joint can be correlated with an ailment, which can provide more information to a practitioner and improve the success of the treatment. However, background noise is usually mixed with the captured sound, which can affect the quality of diagnosis. Cumbersome setup is another problem in widespread use of audio-based treatment methods. The goal of this study is to design a compact clinical tool to excite and capture crepitus, while eliminating the background noise. In this regard, three different sensors — an accelerometer, a condenser microphone, and a contact microphone — are utilized to record crepitus, and they are compared with one another based on their noise content, ease of use, and cost efficiency. The results of this study showed that contact microphone is the most suitable sensor for this purpose. Based on this selection, a compact design is suggested for the clinical tool, which includes a contact microphone.
Model-Based Adaptive Control for a Solenoid-Valve System
Authors: Nataraj C. ‘Nat’ , Lee DongBin
Published: May 2012

In this paper, a model-based control algorithm is developed for a solenoid-valve system. The electric-driven machinery system and its sophisticated control give high levels of automation on huge systems such as ships and submarines. It is known that the characteristics between the force versus displacement and fluid dynamics are strongly nonlinear. The system has uncertainties in multiple parameters in the model, which make the system difficult to adjust to the environment and consequently require adaptation for sustainability and capability. The novelty of this research is that the uncertain nonlinear dynamics of the solenoid-valve system is simplified by formulating in dimensionless form. The non-dimensional control approach of the unknown bounded parameters which is approximately twenty parameter groups used in general adaptive control of the solenoid-butterfly valve system dramatically reduced to just four lumped parameter groups. The control objective is to the set-point of the solenoid-valve and accordingly control the angle position of the butterfly valve in spite of the complications presented by the uncertainties in the dynamic model. The estimated parameters are updated by the adaptation laws using the projection algorithm. After combining the translational and rotational dynamic models, the control input is designed by substituting the electric signal such as current from the model of electromagnetic force. Error signals of the trajectory tracking are developed for the solenoid-valve system. A closed-loop stable controller is designed based on the above error dynamics of the nonlinear solenoid-valve system utilizing Lyapunov-type stability which yields a stable result while obtaining the set-point objective.
Applying a Design Process to Create a Reduction Platform of GHG in Industries
Authors: A´vila Javier , Gonza´lez Silvia , Borja Vicente , Rami´rez Alejandro C. , Lo´pez Parra Marcelo
Published: May 2012

This paper describes the final results of a project aiming at addressing climate change by creating a GHG reduction platform for businesses with carbon management needs in global markets. The project was carried out during a New Product Development course in a bi-national program between The University of California at Berkeley (UCB) and the National University of Mexico (Universidad Nacional Auto´noma de Me´xico, UNAM) in Mexico City. The program features collaboration between the Engineering and Design Schools at UNAM and Engineering and Business Schools at UCB and the College of Architecture CCA. The project, The Carbon Collaborative (TCC) is aimed at consolidating and managing the wide variety of policies and instruments created by governments and environmental organizations to mitigate climate change, and the anthropogenic gas emissions emitted by industry in particular in the US and Mexico. Based on a web platform TCC will provide companies with information on carbon legislation and a centralized location to find transparent and certified methodologies for carbon emission assessment. The differences between the US and Mexican markets lead to advantages for each part. The US market is full of developed consulting enterprises, which is not the case in the Mexican arena, giving to TCC the opportunity of being pioneers to regulate and manage large and small emitters, government environmental agencies and ERP (Enterprise Resource Planning) companies.
On Transverse Vibrations of Functionally Graded Rotating Hollow Disk
Authors: Liu Rui , Nayeb-Hashemi Hamid , Olia Masoud , Vaziri Ashkan
Published: May 2012

We studied the stress field and vibration characteristics of functionally graded rotating disks by solving the governing equation of motion using the finite difference scheme. The material was assumed to have a constant Poisson’s ratio with the elastic modulus varying as a power law function of the disk radius. Such a material could be developed by using particle reinforced composites with various reinforcements or reinforcement volume fraction. The results show that the first critical speed of the rotating disk could be increased by using FGMs. The first critical speed is greater for disks having higher elastic modulus at the outer radius. However, the disk may be unstable for certain distribution functions.
Virtual Lab Activities for a Distance Course in Fluid Power
Authors: Fuehne Joseph P.
Published: May 2012

Virtual lab activities utilizing simulation software are gaining in popularity and importance. Simulation software can be purchased in sufficient quantities to allow every student in a class to perform lab activities rather than doing physical labs with limited equipment and a team approach, providing uncertainty as to who is really doing the work. Another advantage would be using the software across several locations throughout a region and pairing it with software like Adobe Connect or two-way video in some distance education format. Students in multiple locations can connect via computer and can perform lab activities in synchronous or asynchronous sessions. Actual physical lab activities could be included in the course on a limited basis to accommodate students from several locations. This work will investigate simulation software available for use with fluid power and discuss strategies for incorporating into appropriate classes.
Fluid Structure Interaction Analysis of Stentless Bio-Prosthetic Aortic Heart Valve in Sinus of Valsalva
Authors: Kouhi Esfandyar , Morsi Yos
Published: May 2012

In this paper the fluid structure interaction in stentless aortic heart valve during acceleration phase was performed successfully using the commercial ANSYS/CFX package. The aim is to provide unidirectional coupling FSI analysis of physiological blood flow within an anatomically corrected numerical model of stentless aortic valve. Pulsatile, Newtonian, and turbulent blood flow rheology at aortic level was applied to fluid domain. The proposed structural prosthesis had a novel multi thickness leaflet design decreased from aortic root down to free age surface. An appropriate interpolation scheme used to import the fluid pressure on the structure at their interface. The prosthesis deformations over the acceleration time showed bending dominant characteristic at early stages of the cardiac cycle. More stretching and flattening observed in the rest of the times steps. The multi axial Von Mises stress data analysis was validated with experimental data which confirmed the initial design of the prosthesis.
Investigation of Nanofibrous Film Coating Effect on Surface Acoustic Wave Sensors
Authors: Liu Sai , Wang Pengtao , Song Minghao , Sun Hongwei
Published: May 2012

Electrospinning is reported in this paper as a new coating approach for surface acoustic wave (SAW) sensor in order to enhance its chemical detection capability. Ultrafine (100–300 nm) polyethylene oxide (PEO) fibrous film with controlled thickness and porosity were electrospun-coated on the surface of a ST-X quartz based SAW sensor. Compared to the conventional solid thin film coating techniques, the nanofiber-coated SAW sensor shows a higher sensitivity and faster response. A theoretical analysis was performed to characterize the SAW sensor response with nanofibrous film coating. The nanofibrous film provides a high surface area to volume ratio, which can not only offer more adsorption sites for vapor molecules, but also shortens the diffusion length of vapor molecules into polymer material. It is concluded that the nanofiber film holds a great potential in enhancing SAW sensor performance for trace level detection of chemical analytes.
Effect of Sample’s Diameter on Flow Properties of Open-Cell Metal Foam
Authors: Dukhan Nihad , Ali Mohamed
Published: May 2012

Many applications require fluid flow through the open-cell metal foam. The foam is usually treated as a porous medium for which the Darcy law and the Hazen-Dupuit-Darcy (or Forchheimer) equations are used to describe the pressure drop, and in obtaining the two important flow properties, i.e., the permeability and the form drag coefficient. Little or no attention is paid to the transverse size of the porous medium perpendicular to the flow direction. This paper establishes a minimum diameter necessary for the foam to have diameter-independent (or bulk) permeability and form drag coefficient. This minimum diameter is obtained experimentally for open-cell aluminum foam subjected to airflow in the Forchheimer regime. Below this thickness values of the two key flow properties are not constant, and they include wall effects, which may explain some the discrepancies in the reported values in the literature.
Thermal-Mechanical Analysis of Varying Boundary Conditions on a LEU Foil Based Molybdenum-99 Plate Processing Target
Authors: Turner Kyler K. , Solbrekken Gary L. , Allen Charlie W.
Published: May 2012

Technetium-99m is a diagnostic radio-pharmaceutical that is currently used in 85% of the United States diagnostic imaging procedures [1]. All supplies of technetium-99m’s parent isotope molybdenum-99 currently originate from the irradiation of high enriched uranium (HEU) in nuclear reactor facilities located outside the United States. In accordance with the Global Threat Reduction Initiative all uranium used in future molybdenum-99 production will use low enriched uranium (LEU). Conversion to LEU material effectively mandates using LEU in the form of a metal foil as opposed to current powder based dispersion designs for HEU. Using a foil requires a significant modification to the current target design. One design approach uses an LEU foil sandwiched between two nominally flat aluminum plates. The LEU is enclosed in the sandwiched structure by welding the aluminum plates together about their edges. The plate design is inspired by LEU fuel plates with the exception that the LEU is not bonded to the aluminum plates nor is it necessary to clamp the plate edges to prevent lateral translation. This paper will review the thermal-mechanical analysis of an LEU based molybdenum-99 target with plate geometry. This study describes the impact of boundary conditions on the thermally-induced stress and strain in the aluminum plates.
Combined FEA-Matlab Optimization of Capacitive Micromachined Ultrasound Transducer Cell
Authors: Najar Hadi , Assadsangabi Babak , Dahmardeh Masoud , Cretu Edmond
Published: May 2012

A novel approach to the design of a Capacitive Micromachined Ultrasound Transducer (CMUT) cells is presented, using a Genetic Algorithm (GA) based optimization that couples finite element simulations with parameter changes tuned through Matlab scripts. The optimization goal is a maximization of the CMUT efficiency in coupling the electrical, mechanical and acoustic energy domains. Global constraints are related to the pull-in actuation voltage, resonant frequency (set to 5–6MHz, suitable for biomedical applications) and limits on the achievable geometric dimensions. A CMUT is a relatively new MEMS device used to generate and sense ultrasound waves through electrical actuation. Our CMUT design aims to generate ultrasound waves in the 5–6 MHz range, suitable for breast tumor detection. The electro-mechano-acoustical nonlinear coupling makes the design and optimization process difficult, requiring several cycles of finite element analysis. Therefore, a genetic constrained optimization algorithm implemented in Matlab is coupled with finite element simulations of a parameterized structure modeled in COMSOL Multiphysics, in order to maximize the efficiency of the CMUT cell. The main goal is to achieve maximum transducer efficiency, reflected in a better operating device with lower power consumption. The Matlab-FEA optimization loop is driven by the transducer electro-mechanical efficiency, used as a main performance measure to vary the CMUT geometry parameters from one generation to another.
Effect of Release Holes on Micro-Scale Solid-Solid Phononic Crystals
Authors: Su Mehmet , Reinke Charles , Soliman Yasser , Leseman Zayd , Olsson Roy , El-Kady Ihab
Published: May 2012

Solid-solid phononic crystals (solid inclusions in a solid matrix) exhibit wider bandgaps than those observed with air-solid phononic crystals (air inclusions in a solid matrix). In a solid-solid phononic crystal operating in the low MHz range, it is essential to place release holes in the center of the inclusions to release devices from the substrate. It is necessary to release, and therefore suspend the phononic crystal to avoid propagation losses through the substrate. In this report we investigate the effect of release holes on phononic bandgaps and highlight the need for careful design to avoid compromising the phononic bandgap. Studying release issues for solid-solid phononic crystals is essential for the successful fabrication of such devices.
Design of Microscale Heat and Mass Exchangers for Absorption Space Conditioning Applications
Authors: Nagavarapu Ananda Krishna , Garimella Srinivas
Published: May 2012

This paper presents the development of a miniaturization technology for heat and mass exchangers used in absorption heat pumps. The exchanger consists of an array of parallel, aligned alternating shims with integral microscale features, enclosed between cover plates. These microscale features facilitate the flow of the various fluid streams and the associated heat and mass transfer. In an absorber application, effective vapor and solution contact and microscale features for the flow of both the solution and the coolant induce high heat and mass transfer rates without any active or passive surface enhancement. The geometry ensures even flow distribution with minimal overall pressure drops. A model of the coupled heat and mass transfer process for ammonia-water absorbers using this configuration under typical operating conditions demonstrates the potential for extremely small absorption components. The proposed concept is compact, modular, versatile, and in an eventual implementation, can be mass produced. Additionally the same concept can be extended to the other absorption heat pump components as well as for several other industries involved in multi-component fluid processes.
CFD Prediction of Particle Deposition in Large-Scale Human Lung Models
Authors: Walters D. Keith , Luke William H.
Published: May 2012

Computational fluid dynamics (CFD) has evolved as a useful tool for the prediction of airflow and particle transport within the human lung airway. A large number of published studies have demonstrated the use of CFD coupled with Lagrangian particle tracking methods to determine local and regional deposition rates in small subsections of the bronchopulmonary tree. However, simulation of particle transport and deposition in large-scale models encompassing more than a few generations is less common, due primarily to the sheer size and complexity of the human lung airway geometry. Fully coupled flowfield solution and particle tracking in the entire lung, for example, is currently an intractable problem and will remain so for the foreseeable future. This paper adopts a previously reported methodology for simulating large-scale regions of the lung airway [1], which was shown to produce results similar to fully resolved geometries using approximate, reduced geometry models. The methodology is here extended to particle transport and deposition simulations. Lagrangian particle-tracking simulations are performed in combination with Eulerian simulations of the air flow in an idealized representation of the human lung airway tree. Results using the reduced models are compared to fully resolved models for an eight-generation region of the conducting zone. Agreement between fully resolved and reduced geometry simulations indicates that the new method can provide an accurate alternative for large-scale CFD simulations while reducing the computational cost of these simulations by an order of magnitude or more.
Development and Validation of a 2D/3D Finite Element Model of a Composite Hemipelvis
Authors: Elenes Egleide Y. , Roan Esra , Marinescu Ruxandra C. , Janda Haden A.
Published: May 2012

The use of mechanical analogue composite bone models for a range of biomechanical analyses and testing procedures has grown rapidly since their introduction by Sawbones (Pacific Research Laboratories, Inc., Vashon, WA). The advantages of these composite bones over cadaveric human bones include less variability among specimens, ready availability, lower costs and ease of handling. The fourth generation of Sawbones is now commercially available, which include human femurs, tibiae, humeri and hemipelves. A number of these composite bone models have been mechanically evaluated, i.e. the femur and tibia models, but others such as the hemipelvis have been neglected. However, the composite hemipelvis has been used in several biomechanical research studies; therefore, mechanical validation of the hemipelvis is required. For this study, a robust finite element (FE) model was constructed to investigate the mechanical behavior of a composite left hemipelvis bone model. A computer tomography (CT) scan of the analogue was obtained to produce a computer aided volumetric model. This model was imported and discretized in ABAQUS (Simulia, Providence, RI). In order to reduce computational costs, two-dimensional (2D) shell elements were used to mesh the thin cortical bone layer, while the cancellous bone region was meshed with solid, three-dimensional (3D) tetrahedral elements. A series of FE tests were performed on various shell-solid element domains, to ensure the use of 2D shell elements to model the cortical layer. Once the shell-solid approach was confirmed, a FE model of the hemipelvis was constructed and validated against strain gauge data from quasi-static loading experiments. Three rosette strain gauges (Vishay Micro-Measurements, Raleigh, NC) were mounted on regions of interest along the pubic body, inferior ramus and ischium of the composite hemipelvis. The hemipelvis was fully restrained in a custom-built fixture while quasi-statically loaded using an MTS Mini Bionix II to control the application of 600 N (MTS Systems Corp, Eden Prairie, MN). Maximum and minimum principal strains were calculated from the strain gauge readings and compared to FE predictions of strain at the mounting location of the strain gauges.
Fuel Drop Spreading on a Flat Smooth Surface: Numerical Simulations With a VOF Method
Authors: Zhang Yan , Ratner Albert
Published: May 2012

With the current interest in bio-derived and blended transportation fuels, the impact of the variable viscosity in these fuels on spray and splash properties has become an area of concern. In this work, the dynamics of a liquid drop impacting and spreading on a flat, smooth surface was computationally investigated by employing the volume of fluid (VOF) approach with the commercial solver Fluent 12.0.16, and the results were base-lined with experimental measurements. Of particular interest was the degree of fidelity required of the contact angle model, with the present work proposing and testing a combined static contact angle-dynamic contact angle (SCA-DCA) model to describe drop spreading. This model was shown to reduce the behavior information required as compared with full dynamic contact angle (DCA) models while significantly improving over the accuracy of a pure static contact angle (SCA) model. Two different computational domains were tested and compared for the proposed SCA-DCA model, a quarter-drop versus a full-drop domain, with the results showing that the error was reduced when the full domain was employed.
Hydrogel Composite as a Nucleus Pulposus Replacement Designed to Resist Extrusion While Maintaining Functional Material Properties
Authors: Beattie William , Bay Brian
Published: May 2012

This study pursues the design of a nucleus pulposus replacement device which can be placed using minimally invasive surgical techniques, has the correct material properties, and resists extrusion. A composite of open-celled foam and agar was studied in both unconfined and confined compression, the latter with a simulated annular defect (radial tear simulation). It was found that by compositing the agar into the open-cell foam, there is an increase in the yield strength and stiffness in unconfined compression. In the radial tear simulator, the composite material exhibited linearly increasing stress to further extrusion after the initial yield compared to the agar, which exhibited no increase in stress for continued extrusion after the yield point.
Tensile Stress Relaxation of Thermosetting Polyurethane Solid and Foam
Authors: Barua Bipul , Saha Mrinal C.
Published: May 2012

Stress relaxation behavior of thermosetting polyurethane (PU) solid and foam were investigated in tensile mode using a dynamic mechanical analyzer (DMA). PU solid samples were manufactured in a closed mold under compression to avoid any foam formation, whilst the foam samples were manufactured inside a woven using a silicone mold. Effects of cure and the post-cure temperature were also investigated on the stress relaxation behavior. Samples in the form of rectangular cross-section were subjected to a predetermined amount tensile strain and the tensile force was recorded as a function of time. Relaxation modulus was determined for different temperatures up to near the glass transition temperature. It was found that the viscous part becomes dominant with increasing test temperature. The experimental data was precisely modeled using a generalized Maxwell’s model and the characteristic relaxation time was identified with the corresponding relaxation process. Although the stress relaxation behavior of PU solid and PU foams were found similar at room temperature, the relaxation behavior of the foam was found to be influenced by the cell morphology at higher temperature.
Dynamic System Optimization Using Higher-Order Runge-Kutta Discretization
Authors: Fabien Brian C.
Published: May 2012

This paper evaluates some numerical methods for the approximate solution dynamic system optimization problems. The paper considers the optimization of dynamic systems that are subject to equality and inequality constraints. These types of problems include optimal control and parameter identification optimization problems. The numerical solution technique is based on transforming the infinite dimensional dynamic system optimization problem into a finite dimensional nonlinear programming (NLP) problem. This solution method is realized by; (i) approximating the control input using a finite set of parameters; (ii) approximating the differential equations using an explicit Runge-Kutta method; and (iii) solving the resultant NLP problem using a sequential quadratic programming method. The paper evaluates the efficacy of approximating the control input using (I) piecewise constants, (II) piecewise linear polynomials, or (III) piecewise cubic polynomials. In addition, the paper compares the performance of various Runge-Kutta methods of order 3 through 9.
Numerical Evaluation of Single Fiber Motion for Short Fiber Composites Materials Processing
Authors: Zhang Dongdong , Smith Douglas E. , Jack David A. , Montgomery-Smith Stephen
Published: May 2012

This paper presents a numerical approach for calculating the single fiber motion in a viscous flow. This approach addresses such issues as the role of axis ratio and fiber shape on the dynamics of a single fiber, which was not addressed in Jeffery’s original work. We develop a Finite Element Method (FEM) for modeling the dynamics of a single rigid fiber suspended in a moving fluid. Low Reynolds number viscous flows are considered since these best represent the flow conditions for a polymer melt within a mold cavity. Our approach seeks the fiber angular velocities that zero the hydrodynamic torques acting on the fiber using the Newton-Raphson method. Fiber motion is then computed with a Runge-Kutta method to update the position, i.e. the angle of the fiber as a function of time. This method is quite general and allows for fiber shapes that include, but are not limited to, ellipsoidal fibers (such as that studied in Jeffery’s original work), cylindrical fibers and beads-chain fibers. The relationships between equivalent axis ratios and geometrical axis ratios for cylindrical and beads-chain fibers are derived in this paper.
Active Learning in Mechanical and Mechatronics Engineering, Case Study: Computer-Based Interactive Learning in Robotics Classroom
Authors: Alemohammad Hamid R. , Shahini Mohsen
Published: May 2012

This paper is concerned with the review of active learning methods implemented in Mechanical and Mechatronics Engineering courses. The active learning methods are categorized into two groups of in-class activities without the use of computers and computer-based classrooms. The strategies to encourage university instructors to adopt active learning methods are also discussed. The paper also addresses the pilot project for the implementation of a novel computer-based experiential learning in the course of “Robot Manipulators: Kinematics, Dynamics, Control” at the University of Waterloo, Canada. A Student Interactive Learning System (SILS) has been developed for in-class activities in this course. The SILS system has two components: students’ mobile devices and a front-end website in which the instructor has control to upload the demonstrations and quizzes and receive students’ responses. The students are connected to the website through the WiFi connection. Findings of an initial survey, which was conducted at the start of the semester, revealed that majority of the students find the conventional classroom passive and believe adding interactivity in the lecture enhances their in-class learning experiences.
A New Energy Frugal Paradigm for Data Centers
Authors: Little Adrienne B. , Garimella Srinivas
Published: May 2012

Of the total electricity consumption by the United States in 2006, more than 1% was used on data centers alone; a value that continues to rise rapidly. Of the total amount of electricity a data center consumes, at least 30% is used to cool server equipment. The present study conceptualizes and analyzes a novel paradigm consisting of integrated power, cooling, and waste heat recovery and upgrade systems that considerably lowers the energy footprint of data centers. Thus, on-site power generation equipment is used to supply primary electricity needs of the data center. The microturbine-derived waste heat is recovered to run an absorption chiller that supplies the entire cooling load of the data center, essentially providing the requisite cooling without any additional expenditure of primary energy. Furthermore, the waste heat rejected by the data center itself is boosted to a higher temperature with a heat transformer, with the upgraded thermal stream serving as an additional output of the data center with no additional electrical power input. Such upgraded heat can be used for district heating applications in neighboring residential buildings, or as process heat for commercial end uses such as laundries, hospitals and restaurants. With such a system, the primary energy usage of the data center as a whole can be reduced by about 23 percent while still addressing the high-flux cooling loads, in addition to providing a new income stream through the sales of upgraded thermal energy. Given the large and fast-escalating energy consumption patterns of data centers, this novel, integrated approach to electricity and cooling supply, and waste heat recovery and upgrade will substantially reduce primary energy consumption for this important end use worldwide.