bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of BCAM/Lu and ICAM-4 Expression on Red Blood Cell Membranes in Physiological Stress Conditions
Authors: Maciaszek Jamie L. , Andemariam Biree , Lykotrafitis George
Published: August 2012

Using single-molecule atomic force microscopy (AFM) experiments, we report that epinephrine, a hormone secreted during stress and strenuous exercise, increases both the frequency and strength of adhesion events of sickle cell trait erythrocytes to the endothelial extracellular matrix (ECM). The specific interactions quantified include Lutheran (BCAM/Lu) and intercellular adhesion molecule-4 (ICAM-4) on the RBC surface with ECM laminin and endothelial αvβ3, respectively. These data present significant evidence of the role of epinephrine in BCAM/Lu-laminin and ICAM-4-αvβ3 bonding, and suggest mechanisms of vaso-occlusion during physical exertion in SCT.
Transition Prediction in Low Pressure Turbine (LPT) Using Gamma Theta Model and Passive Control of Separation
Authors: Chishty Muhammad Aqib , Parvez Khalid , Ahmed Sijal , Hamdani Hossein Raza , Mushtaq Ammar
Published: August 2012

The boundary layer of low-pressure turbine blades has received a great deal of attention due to advent of high lift and ultra high lift LP turbines. At cruising condition, Reynolds number is very low in engine and LP turbine performance suffers mainly from losses due to the laminar separation bubble on suction surface. In this paper, T106A low pressure turbine profile has been used to study the behavior of boundary layer and subsequently, flow is controlled using the passive technique. Unsteady Reynolds Averaged Navier Stokes equations were solved using SST Gamma-Theta transition model for turbulence closure. Hybrid mesh topology has been used to discretize the computational domain, with highly resolved structured mesh in boundary layer (Y+ < 1) and unstructured mesh in the rest of domain. Simulations were performed using commercial CFD code ANSYS FLUENT ® at Reynolds number 91000 (based on inlet velocity and chord length) and turbulence intensity of 0.4%. To study the effect of dimple on the flow separation, dimple has been positioned at different axial location on the suction side. It was found that shifting the dimple downstream results in controlled flow and reduced loss coefficient as compared to the case when no dimple is applied.
Further Validation of the Head in the Ford Human Body FE Model
Authors: El-Jawahri Raed E. , Laituri Tony R. , Ruan Jesse
Published: August 2012

The head in the Ford human body model (FHBM) was previously validated against impact test data involving post mortem human subjects (PMHS). The objective of the current study was to further validate the head model against more PMHS tests. The data included the following published tests: rigid bar impact to the forehead, zygoma, and maxilla (2.5–4.2 m/s), lateral pendulum impact (5.7 m/s), and front pendulum impact to the frontal bone, nasal bone, and maxilla (2.2 m/s). The responses from the model were compared to available published cadaveric response corridors and to various cadaveric responses. When compared to the cadaveric response corridors, the responses from the model were within those corridors. In addition, the model responses demonstrated acceptable fidelity with respect to the test data. The head injury criterion (HIC15), strain, and stress values from the model were also reported.
Detrended Fluctuation Analysis of Arrhythmia: Scaling Exponent as an Index of Heart Wellness
Authors: Yazawa Toru , Hutapea Albert M. , Katsuyama Tomoo , Shimoda Yukio
Published: August 2012

Well-established technologies to analyze biological signals including rhythmic heartbeat are available and accessible to scholars. However, stronger empirical evidence is required to justify the use of these technologies as practical tools in the field of biomedicine. Here we conducted analyses of heartbeat interval time series using an analytical technology developed across three decades—detrended fluctuation analysis (DFA)—to verify the power-law/scaling characteristics of signals that fluctuate in a regular, irregular, or erratic manner. We believe that DFA is a useful tool because it can quantify the heart condition by a scaling exponent, with a value of one (1) set as the default for a healthy state. This baseline value can be compared to a clinical thermometer, where the baseline is 37 °C for a physiologically healthy condition. Our study aimed to ascertain and confirm the utility of DFA in evaluating heart wellness, specifically in the context of studying arrhythmic heartbeat. We present case studies to confirm that DFA is a beneficial tool that quantifies the scaling exponent of a heart’s condition as “nonstationarily” beating and dynamically controlled. From an engineering perspective, we show that the heart condition can be classified into two typical categories: a healthy rhythm with a scaling exponent of one (1.0), and arrhythmia with a lower scaling exponent (0.7 or less).
Performance Analysis of Rice Bran Oil [Non-Edible] as Alternative Fuel for D I Engines
Authors: Rampure Prasad Baburao , Reddy C. Venkataramana
Published: August 2012

The economic growth of any country is determined by the natural resources it possesses and the fuel that it has. The rate of growth of any country is mostly directly proportional to the amount of fuel it possesses. Fossil fuels are important resources those have helped in the rapid industrialization of the world and thus to the increase in the quality of life. However, due to the threat of supply instabilities and the effect of green house gases caused by internal combustion engines have received more and more interests in the use of alternative fuel. The study deals with the experimental investigation and the performance analysis of rice bran oil (non edible) a straight vegetable oil (SVO] and its blends with diesel for different injector opening pressure by using DI diesel engines. Most of the published work using rice bran oil in diesel engine was carried out without changing injector opening pressure and static injection timing. The observations of the investigation are of the following performance parameters: 1. Specific Fuel Consumption - Diesel vs rice bran oil. 2. Optimum Air Fuel ratios. 3. Study of exhaust gases in line with the specifications of Indian pollution norms. 4.Techno-Commercial considerations in the modification of engine if required. Experiments were conducted by blending diesel with rice bran oil in various proportions and with varying loads. Studies have found that the use of blends of more viscous rice bran oil and Diesel in various percentages result in the decrease of the Specific fuel consumption (SFC) while the use of 100% rice bran oil results in the marginally higher Specific fuel consumption than Diesel. Further studies are on for other parameters.
CAPSULE: An Innovative Capstone-Based Pedagogical Approach to Engage High School Students in STEM Learning
Authors: Zeid Abe , Kamarthi Sagar , Duggan Claire , Chin Jessica
Published: August 2012

School children in general and high school students, in particular more often than not lose interest in STEM (science, technology, engineering, and math) education. Underrepresented and female students are even more discouraged by STEM courses. Our investigation and interviews with high school teachers cite that the main reason for such disinterest is the disconnect between school and reality. Students cannot relate the abstract concepts they learn in physics, biology, chemistry, or math to their surroundings. This paper discusses a new capstone project-based approach that closes this gap. This work is an outcome of an NSF funded project called CAPSULE (Capstone Unique Learning Experience). We use the top-down pedagogical approach instead of the traditional bottom-up approach. The top-down approach relates the abstract concepts to exciting open-ended capstone projects where students are engaged in designing solutions, like products to solve open-ended problems. This top-down approach is modeled after the college-level capstone design courses. The paper presents the model, its details, and implementation. It also presents the formative and summative evaluation of the model after deploying it in the Boston Public Schools, a system heavily populated by the targeted student groups.
On Determination of Sample Size to Evaluate Reliability Growth Plans
Authors: Jin X. , Woytowitz P. , Tan T.
Published: August 2012

The reliability performance of Semiconductor Manufacturing Equipments (SME) is very important for both equipment manufacturers and customers. However, the response variables are random in nature and can significantly change due to many factors. In order to track the equipment reliability performance with certain confidence, this paper proposes an efficient methodology to calculate the number of samples needed to measure the reliability performance of the SME tools. This paper presents a frequency-based Statistics methodology to calculate the number of sampled tools to evaluate the SME reliability field performance based on certain confidence levels and error margins. One example case has been investigated to demonstrate the method. We demonstrate that the multiple weeks accumulated average reliability metrics of multiple tools do not equal the average of the multiple weeks accumulated average reliability metrics of these tools. We show how the number of required sampled tools increases when the reliability performance is improved and quantify the larger number of sampled tools required when a tighter margin of error or higher confidence level is needed.
Methane-Based Flame Fuel Cell Using Anode Supported Solid Oxide Fuel Cells
Authors: Wang Kang , Zeng Pingying , Schwartz James , Ahn Jeongmin
Published: August 2012

This work presents the performance of the flame fuel cell based on the anode-supported solid oxide fuel cell (AS-SOFC) with a methane flame, which serves not only as a fuel reformer but also as a heat source to sustain the fuel cell operation. The anode-supported SOFC showed an extraordinary fuel cell performance of 475 mW.cm−2 by using a methane flame. The fuel cell performance was determined by fuel cell temperature and fuel concentration which varied with the equivalent ratio and methane flow rate.
Optimization of Stiffness and Damping in Modeling of Voluntary Elbow Flexions
Authors: Chen Kai , Foulds Richard
Published: August 2012

A subsequent study of obstructed voluntary arm movement extended the relative damping concept, and incorporated the influential factors of the mechanical behavior of the neural, muscular and skeletal system in the control and coordination of arm posture and movement. A significant problem of the study is how this information should be used to modify control signals to achieve desired performance. This study used an Equilibrium Point Hypothesis (EPH) model to examine changes of controlling signals for arm movements in the context of adding perturbation/load in the form of forces/torques. The mechanical properties and reflex actions of muscles of the elbow joint were examined. Brief unexpected torque/force pulses of identical magnitude and time duration were introduced at different stages of the movement in a random order by a pre-programmed 3 degree of freedom (DOF) robotic arm (MOOG FCS HapticMaster). Key to this research is the optimization of B and K for each subject based on their HM only experimental data. The results shown in each of sections confirm that those parameters. Along with an EMG determined VT can be used successfully to model the perturbed trials. The results also show that the subjects may maintain the same control parameters (virtual trajectory, stiffness and damping) regardless of added perturbations that cause substantial changes in EMG activity and kinematics.
Algae-Based Biodiesel for Household Applications
Authors: Allameh Seyed , Sarowa Sharon , Kannan Miriam
Published: August 2012

This paper presents the preliminary results of a research and developmental work on biodiesel production. An algae-based biofuel extraction system was developed for household applications. It consists of three modules: algae growth media preparation, biofuel-bearing algae growth chamber, and biodiesel extraction system. The details of the design and fabrication of these systems will be discussed. Further, the results of experiments on the selection of algae specimens and the influence of environmental variables on the growth process will be elucidated.
Effect of Apex Angle on the Flow and Heat Transfer in Triangular Porous Ducts With Iso-Flux Boundary Conditions
Authors: Mortazavi S. Negin , Hassanipour Fatemeh
Published: August 2012

This study presents an analysis of fully developed laminar flow in a porous triangular channel. The flow is assumed to have constant properties and the porous channel is an isotropic matrix. Very accurate analytical solutions are presented by Galerkin Integral method for iso-flux boundary conditions. In this paper, the effect of apex angle in the triangular channel is shown on the velocity and temperature distributions along with the friction factor fRe, and the Nusselt number NuH.
Breaking Down Classroom Walls: Fostering Improved Communication and Relations Between Engineers and Tradesmen Through a Joint Semester Project
Authors: Martin Michael W. , Polkinghorne Cale T.
Published: August 2012

Recent engineering education research has suggested that most engineering curricula does not promote attainment of many characteristics desired in practicing engineers [1][2]. One such characteristic is effective communication with workers in other disciplines. A method to attain improved communication is simulation of workplace situations in the educational environment [3][4]. In an effort to improve communication between trades and to foster a higher appreciation for the other field, a project simulating the working relationship between engineers and machinists was implemented via a joint semester project coupling a Computer Numerical Control (CNC) machining course and an engineering design course. A significant body of knowledge exists regarding multidisciplinary education for engineering students. Nearly all of the multidisciplinary projects involve one discipline of engineering working with another engineering discipline (i.e. mechanical engineering students working with electrical engineering students). The multidisciplinary work between different disciplines of engineering students has documented benefits; however, the two groups of students are on a similar communication level. By coupling junior and senior level bachelor degree-seeking engineering students with students primarily pursuing a 1 year CNC machining certificate, many communication barriers are encountered that are not seen in typical university multidisciplinary projects. The students from the engineering class were tasked with designing a simple assembly that performs a specified function. The engineering student was responsible for generating a complete set of manufacturing prints. Each engineering student was matched with a group of two or three CNC machining students, who were responsible for manufacturing the parts designed by the engineering student. This type of collaboration closely simulates the design engineer working with the manufacturing shop floor employee in determining how a part is best produced and taking the project to completion by manufacturing and assembly of that part. Data collection methods included student surveys and instructor observations. Primary student outcomes appeared to be; 1) an appreciation for the importance of communication and, 2) greater understanding of the complete process needed to produce a product. The primary difficulties the students encountered were due to communication issues and project management breakdowns. Efforts to address these issues and other lessons learned will be discussed.
Electrical Power Grid Delivery Dynamic Analysis: Using Prime Mover Engines to Balance Dynamic Wind Turbine Output
Authors: Grauer Diana K. , Reed Michael E.
Published: August 2012

This paper presents an investigation into integrated wind + combustion engine high penetration electrical generation systems. Renewable generation systems are now a reality of electrical transmission. Unfortunately, many of these renewable energy supplies are stochastic and highly dynamic. Conversely, the existing national grid has been designed for steady state operation. The research team has developed an algorithm to investigate the feasibility and relative capability of a reciprocating internal combustion engine to directly integrate with wind generation in a tightly coupled Hybrid Energy System. Utilizing the Idaho National Laboratory developed Phoenix Model Integration Platform, the research team has coupled demand data with wind turbine generation data and the Aspen Custom Modeler reciprocating engine electrical generator model to investigate the capability of reciprocating engine electrical generation to balance stochastic renewable energy.
On Design of a Buoyancy-Driven Solar Combi-System for Simultaneous Production of Drinking Water and Hot Water
Authors: Panthalookaran Varghese , Nair Neeraj
Published: August 2012

The nexus between availability of solar energy and nonavailability of drinking water is well known. Drinking water scarcity is prevalent in regions where sun shines heavily, which provides an ideal condition for exploiting available solar insolation to produce potable water. When combined with the production of hot water, it could lead to the optimum use of solar energy. The same system can be preferentially used to produce drinking water during hot and dry summer and hot water in cold and wet winter. The current paper describes a work in progress to design a solar combi-system that meets the drinking water and hot water needs of small households in coastal India. The solar distillation operates based on an open humidification-dehumidification cycle. Efficient solar combi-collectors are used to produce hot and dry air and hot water simultaneously. The hot air blasts into the evaporation chamber, which consists of structures to optimize evaporation of the hot water. This allows enhanced humidification of dry air. The condensation chamber efficiently dehumidifies or condenses the saturated air to yield distilled water. The water thus produced is made potable with proper mineralization. A hot water heat store preserves hot water to be fed into the evaporator as well as to the hot water pipeline. The combi-system planned for a small household with approximately 10 liters of drinking water requirement per day and proportionate hot water requirement. The complete system is designed to be driven entirely by the buoyancy forces, without any moving parts.
Multivariable Monte Carlo Analysis Methods in Traffic Accident Reconstruction Using Python
Authors: Knox Michael A.
Published: August 2012

The analysis involved in reconstructing a traffic crash often deals with multiple, codependent, stochastic variables such as departure angle measurements, coefficient of friction measurements, vehicle stiffness coefficients, and acceleration rates. The resulting analysis should appropriately lead to a range of possible vehicle speeds rather than a single speed output value. All too often, this speed range is reported as a continuous uniform distribution in which lower- and upper-bound values are just as probable as any value in between. In reality, vehicle speed ranges are more complex than can properly be represented by a range of equally-probable values. By using repeated iterations drawing on pseudo-random number generation algorithms, Monte Carlo methods have long held the key to performing such statistical analyses. Monte Carlo methods allow for the output of values that are, in most cases, normally distributed and can be used to approximate the probability density function associated with the particular output variable. While Monte Carlo analysis in traffic accident reconstruction has been addressed in a number of other papers, the issue of dealing with codependent variables and the propagation of variable values across multiple calculations has been less apparent in the literature. Understanding not only the application of Monte Carlo methods to multi-variable problems but also the codependent nature of the output distributions and the appropriate selection of input values is essential to the successful application of Monte Carlo algorithms. This paper will address the appropriate methods for implementing multi-variable Monte Carlo solutions for traffic accident reconstruction problems and provide a practical platform for developing algorithms using the Python programming language. Appropriate selection of input values and the use of pseudo-random number generators will be addressed, along with methods for handling the propagation of values through the course of multiple, codependent calculations. While this paper focuses on the implementation of algorithms using Python, these methods can just as readily by implemented using MATLAB, C/C++, FORTRAN, or a variety of other capable programming languages.
Evolution of Mechanical Properties and Microstructural Characterization of Aluminum AA-6061 Butt-Welded Joints
Authors: Kardak Ajay A. , Wahab M. A.
Published: August 2012

Aluminum alloys because of their high strength to weight ratio have various applications as structural material in railways, ship building, aeronautics, construction, and consumer appliances. This increased use of aluminum alloys calls for more efficient and reliable welding processes which has always represented a great challenge for designers and technologists. AA-6061 Aluminum Alloy (Al-Mg-Si) is widely used in the aircraft industry and has gathered wider acceptance in the fabrication of light weight structures. The preferred welding process for this alloy is Tungsten Inert Gas (TIG) process due to their comparatively easier applicability, high yield, and better economy. Major difficulties are associated with this type of welding process, such as, the presence of tenacious oxide layer, high coefficient of thermal expansion, solidification shrinkage, solubility of hydrogen, and other gases in the molten state. Furthermore, problems such as decay of mechanical properties due to phase transformation and softening can occur in the heat-affected-zone (HAZ). Post weld heat treatment can be used to improve the strength of the HAZ for heat-treatable alloys like AA-6061. Hence, the major objectives of this work was to conduct a systematic study and gain an in-depth understanding of the effect of post-weld heat treatment (PWHT) of these joints on tensile properties, micro hardness, microstructure, and fracture surface morphology of butt-welded joints. It was found that of all the PWHT processes, Age-hardening (AH) resulted in superior mechanical properties and hardness. The reason for this enhanced strength has also been studied from metallurgical point of view. Microstructure and fracture surface of the tensile tested specimens were studied using light microscope and scanning electron microscope, respectively. Correlation has been drawn between the tensile test results, microhardness and the metallurgical results. It was found that the uniformly dense precipitation of fine Mg2Si, and the lack of precipitate-free zone could be the reason for the superior results found.
Modeling of Aerosol Spray Characteristics for Synthesis of Mixed-Oxide Nanocomposite Sensor Film
Authors: Khatami S. M. Navid , Ilegbusi Olusegun J.
Published: August 2012

A model is developed of aerosol synthesis of mixed metal oxide nanocomposite film for sensor applications. The synthesis technique involves atomization of a solution of mixed salts in water, spraying of solution droplets, droplet deposition on a heated substrate, evaporation and chemical reaction to produce the mixed oxides, and film growth. The precise control of oxide nanoparticle size distribution and inter-particle spacing in the film is crucial to achieving high sensitivity. These in turn largely depend on the droplet characteristics prior to impingement on the substrate. This paper focuses on development of a model to describe the atomization and spray processes before the film growth. Specifically, a mathematical model is developed utilizing Computational Fluid Dynamics solution of the equations governing the transport of atomized droplets from the nozzle to predict droplet characteristics in flight. The predictions include spatial distribution of droplet size and concentration, and the effect on these characteristics of swirling inlet flow at the spray nozzle.
Hybrid Wound Devices for Spatiotemporally Controlled Release Kinetics
Authors: Ozbolat Ibrahim T. , Koc Bahattin
Published: August 2012

This research presents hybrid full thickness wound devices for improved wound healing process. Firstly, a 3D wound bed surface is extracted using imaging study. Then, a 3D lofting process from our previous work [1] is applied to discretize the device geometry into a number of healing regions based on linear wound margin healing fashion. Next, CAD models are developed and inputted into a multi-nozzle rapid prototyping system for biofabrication purposes. Hybrid devices are finally fabricated with varying concentration of biological modifiers and biomaterials to control the release kinetics spatiotemporally. The proposed methodology is implemented and an illustrative hybrid wound device is presented.
Free Vibration Analysis of Rotating Laminated Composite Panels Using Finite Strip Method With Modified Shape Functions
Authors: Sadr Mohammad Homayoun , Ghashochi Bargh Hadi , Nejadi Mostafa Khorram , Pourzand Hoofar
Published: August 2012

In this paper, free vibration analysis of rotating laminated composite panels is investigated. The formulation is based on the classical laminated plate theory (CLPT), and the method of analysis is the semi-analytical finite strip approach which has been developed on the basis of full energy method with modified shape functions. In the longitudinal direction, the combinations of trigonometric and polynomial functions are used for the out-of-plane displacements, and the trigonometric functions are utilized to estimate the in-plane displacements, to satisfy the kinematic conditions prescribed at the two ends of the strip. Also in the transverse direction, the Hermite cubic shape functions are used for the out-of-plane displacements and the first-order Lagrange shape functions are applied for the in-plane displacements. The panel is considered to be clamped at the rim of a central hub and is free along the other three edges. The effects of different parameters including length/width ratio, number of layers, fiber orientation angles, rotation speed on dimensionless natural frequencies are investigated and discussed in the paper. To check the validity, the results generated by the finite strip procedure are compared with the results of previous studies and finite element code, wherever possible.
A Hybrid Propulsion System for a High-Endurance UAV: Configuration Selection and Aerodynamic Study
Authors: Capata Roberto , Marino Luca , Sciubba Enrico
Published: August 2012

In recent years, a renewed interest in the development of unmanned air vehicles (UAVs) led to a wide range of interesting applications in the fields of reconnaissance and surveillance. In these types of mission, the noise produced by propeller driven UAVs is a major drawback, which can be partially solved by installing an electric motor to drive the propeller. The evolution of high performance brushless motors makes electric propulsion particularly appealing, at least for small and medium size UAVs. All electric propulsion systems developed to date are though penalized by the limited range/endurance that can be provided by a reasonably sized battery pack. In this paper we propose a hybrid propulsion system based on a recently developed, high efficiency microturbine which can be used to power an electric generator, thus providing a significant range/mission time extension. The UMTG is undergoing operational testing in our Laboratory, to identify its most suitable configuration and to improve its performance: a new compact regenerative combustion chamber was developed and several tests were performed to reduce its weight and size so as to increase the vehicle payload. In a high range/endurance mission the ultramicro turbine drives the electrical motor that powers the propeller only during the cruise phase (the so-called “transfer to target”), while in the final approach, in which a quiet flight attitude is mandatory, a (smaller) battery pack drives the motor directly and the UMTG is turned off. The mission requirements considered for the preliminary design of the UAV consist of a long endurance (> 12 hours) step, with a cruise speed of 33.3 m/s and a dash speed of 45 m/s at an altitude of 5000 meters. The maximum take-off weight is 500 N, with a payload of 80 N. Under the above assumptions, a flying wing configuration for the UAV was defined, with a length of 1.6 meters and a span of 2.5 meters. A system of elevons assures the pitch and roll motion while a double vertical tail, in which a pusher propeller is lodged, guarantees the yaw stability and control.
Workforce Development for Global Aircraft Design
Authors: Koster Jean , Kraemer Ewald , Munz Claus-Dieter , Verstraete Dries , Wong K. C. , Velazco Alec
Published: August 2012

A delocalized international team of Graduate and Undergraduate students conceive, design, implement, and operate a 3 meter wingspan aircraft with the intent to investigate numerous new ‘green’ aircraft technologies. The project, known as Hyperion, teaches essential systems engineering skills through long-distance design collaborations with multidisciplinary teams of engineering students located around the world. Project partners are the University of Colorado at Boulder, USA, the University of Sydney, Australia, and the University of Stuttgart, Germany. The teams on three continents are distributed 8 hours apart; students can relay select work daily so that progress can “Follow The Sun (FTS).” As a result three workdays are packaged in one 24 hour period. The student teams operate as a single, independent entity; structuring themselves as a simulated industry operation. Thus, project management and systems engineering principles are learned through a real-world design and deliver experience. The project also teaches delocalized manufacturing: select components are manufactured by each team and integrated both in Stuttgart and Colorado, giving the students an opportunity to learn multifaceted design for manufacturing. The project incubated many problems which lead to mitigation techniques for global collaboration as well as generating a better educated workforce to enter modern industry.
A Numerical Investigation of the Effects of Flow Pulsations on the Vortex Shedding, Drag and Lift Forces Over a Cylinder
Authors: D’herde Eric , Guessous Laila
Published: August 2012

Flow over a cylinder is a fundamental fluid mechanics problem that involves a simple geometry, yet increasingly complex flow patterns as the Reynolds number is increased, most notably the development of a Karman vortex with a natural vortex shedding frequency when the Reynolds number exceeds a value of about 40. The goal of this ongoing study is to numerically investigate the effect of an incoming free-stream velocity pulsation with a mean Reynolds number of 100 on the drag and lift forces over and vorticity dynamics behind a circular cylinder. This paper reports on initial results involving unsteady, laminar and incompressible flows over a circular cylinder. Sinusoidal free-stream pulsations with amplitudes Av varying between 25% and 75% of the mean free-stream velocity and frequencies varying between 0.25 and 5 times the natural shedding frequency fs were considered. Of particular interest to us is the interaction between the pulsating frequency and natural vortex shedding frequency and the resulting effects on drag. Interestingly, at frequencies close to the natural frequency, and to twice the natural frequency, a sudden drop in the mean value of the drag coefficient is observed. The first drop in the drag coefficient, i.e. near f = fs, is also accompanied by a change in the flow and vortex shedding patterns observed behind the cylinder. This change in vortex shedding pattern manifests itself as a departure from symmetrical shedding, and in a non-zero mean lift coefficient value. The second drop, i.e. near f = 2 fs, has similar characteristics, except that the mean lift coefficient remains at zero.
Burning Speeds and Autoignition of Jet Fuel and JP-8/Air Mixtures
Authors: Moghaddas Ali , Bennett Casey , Eisazadeh-Far Kian , Metghalchi Hameed
Published: August 2012

In this paper, the laminar burning speed of Jet Fuel (Jet-A) and three different samples of JP-8 are investigated. The autoignition properties of JP-8 fuels are also explored. These experiments have been done in a spherical vessel at high temperatures and pressures with different equivalence ratios. The pressure data were recorded by a Kistler pressure transducer, and intense fluctuations of pressure data were observed during the explosion of the unburned gas zone. It is observed that Jet Fuel and JP-8/air mixtures have very similar burning speed. Also, autoignition of these fuels is very sensitive to a specific range of temperature rather than pressure.
In-Flight Deployable Micro Devices in Noise Control: Design and Evaluation
Authors: Sarigul-Klijn Nesrin , Kuo Brian C.
Published: August 2012

In this paper, time-accurate RANS simulations and FWH acoustic analogy were carried to study the three-dimensional unsteady flowfield and acoustic components around a three-element high-lift wing with and without micro devices. Micro devices are designed to be attached to the pressure side of the high lift surface near its trailing-edge to help reduce the noise generated. The analysis revealed that with the deployment of the micro device, along with reduced high-lift device setting angles, an overall airframe noise reduction of 2–5 dB is obtained over the entire frequency range. Noise reduction in the mid-frequency range, where human hearing is the most sensitive to, was particularly evident. As seen in an earlier 2D study by the authors, the application of the micro device caused strong aerodynamic force oscillations, resulting in a tone spike at a very low frequency. However, looking at the A-weighted scale sound pressure level spectrum, noise sources from the high-lift devices still dominated and it was the slat noise which dominated the overall 1/3 octave band sound pressure level. Through the reduced high-lift setting angles and the micro device application, an overall 2.3 dB noise reduction was achieved. Based on the current three-dimensional and the previous two-dimensional acoustic study results, micro devices designed by the authors demonstrated its potential to be applied onto commercial airliners as well as any aerial platforms for the use in airframe noise reduction during approach to landing phase of flight.
Noninvasive In Vivo Characterization of Pediatric Human Spine: 3-D Finite Element Study
Authors: Doughty Elizabeth S. , Sarigul-Klijn Nesrin
Published: August 2012

There are no full three-dimensional computational models of the pediatric spine to study the many diseases and disorders that afflict the immature spine using finite element analysis. To fully characterize the pediatric spine, we created a pediatric specific computational model of C1-L5 using noninvasive in vivo techniques to incorporate the differences between the adult and pediatric spines: un-fused vertebrae, lax ligaments, and higher water content in the intervertebral discs. Muscle follower loads were included in the model to simulate muscle activation for five muscles involved in spine stabilization. This paper is the first pediatric three-dimensional model developed to date. Due to a lack of experimental pediatric spinal studies, this 3-D computational model has the potential to become a surgical tool to ensure that the most appropriate technique is chosen for treating pediatric spinal dysfunctions such as congenital abnormalities, idiopathic scoliosis, and vertebral fractures.
Energy Intensity of Water: Literature Suggests Increasing Interest Despite Limited and Inconsistent Data
Authors: Hallett Kathleen C.
Published: August 2012

Water agencies use energy to pump, treat, and distribute potable water. Wastewater treatment plants use energy to collect, treat, and discharge wastewater. The energy intensity of water—the energy embedded in a unit of water delivered—varies considerably depending on the water source, the location and size of the agency’s service area, and the treatment technology employed. The frequency at which agencies collect energy use data also varies, as does the degree to which those data are available. Available estimates of the energy intensity of water also vary greatly. There is a growing recognition within the water and energy communities that new water supplies will likely be increasingly energy intensive and that water conservation efforts will thus result in energy savings. As a result, there is increasing interest in understanding baseline energy use, projected energy use, and opportunities for reducing energy consumption by water and wastewater agencies. The collection of additional, more consistent and more granular data is essential to gaining this understanding.”
Numerical Investigation on Air Side Performance of Fin-and-Tube Heat Exchangers With Large Diameter Tubes and Large Number of Tube Rows
Authors: Zhou Feng , Geb David , Catton Ivan
Published: August 2012

In the present study, air-side turbulent heat transfer and friction characteristics of fin-and-tube heat exchangers with a large number of tube rows and large diameter of tubes are investigated numerically. Finite Volume Method based CFD software, Ansys CFX, was used as the 3-D Reynolds-averaged Navier-Stokes Solver. A k-ω based Shear-Stress-Transport (SST) model was used to predict the turbulent flow and heat transfer through the fin-and-tube heat exchanger coil. The effects of parameters such as Reynolds number, the number of tube rows, tube diameter, tube pitches and fin pitch are examined. In the end, correlations for the Nusselt number and friction factor which applicable to fin-and-tube heat exchangers with large number of large-diameter tube rows are proposed.
Exploring the MEMS Enabled Water Preservation in Micro-Scale Direct Methanol Fuel Cells
Authors: Alyousef Yousef , Yao Shi-chune
Published: August 2012

To ensure the Direct Methanol Fuel Cells (DMFC) achieve a high power density, it is necessary to use high concentration methanol in the storage. However, it is still necessary to supply the needed water in the PEM process. Thus, it becomes necessary to preserve the water from losing at the cathode side. In this exploration, hydrophobic Teflon membrane, with micro-size pores, is applied at the outside of the cathode to prevent water exits to the air stream but still allowing the oxygen to diffuse through. Gold film is sputtered at the inner face of the Teflon membrane to provide electric conductivity. Water tests indicate that this membrane is able to hold significant pressure and allowing the water to be pushed back through PEM to the anode. This modified cathode has been assembled into a micro fuel cell. Electrochemical tests indicated that this fuel cell operates well at various temperatures. Compare with a same fuel cell but using carbon paper instead, it appears that the sputtered gold film has the potential to provide sufficient conductivity. Although the water preservation capability has not been fully validated due to the present micro-scale measurement limitation, this exploration has indicated a promising method to improve the energy density of micro-DMFC.
Pulse Tube Cryocooler Dynamics and Simulation
Authors: Davis Christopher , Sarigul-Klijn Nesrin
Published: August 2012

The Pulse Tube cryocooler is a relatively new device with a promising future in space grade cryogenics. Unlike many active cryocoolers, the pulse tube is a regenerative type cooler with no cold end moving parts. The lack of cold end moving parts permits it to be used in application with mechanically sensitive or high fidelity components. The pulse tube currently lacks adequate scientific literature and understandings that other space qualified cryocoolers have. A systematic approach to understand, model, and study is provided in this work. Further, the importance of a standardized convention of the dynamically complex pulse tube is elucidated to clarify conflicting accounts found in literature. Flow solutions of the pulse tube demands great conceptual understanding and are carried out though numerical simulation. A 2-D pulse tube is modeled in detail assuming axisymmetric conditions. It is found that flow initialization periods are substantially long in comparison to cycle time due to the great inertial resistance found in pulse tubes along with the large volume associated to the reservoir. During this period, the pulse tube section temperature profile is found to significantly rise prior to a refrigeration permitting profile. It is also found that porous medium (inertial) resistance coefficients can be utilized to sufficiently model long spans of inertance tubing without the need for increased computationally-demanding mesh size.
Effect of Viscosity and Reynolds Number for Flow in Converging Microchannels
Authors: Macken Nelson , Boutelle Christopher , Osgood-Jacobs Logan
Published: August 2012

The interface between intersecting microfluidic flows is investigated experimentally. Two microchannel configurations are studied. Each configuration has a main channel and an intersecting daughter channel. The channel cross sections are equal and square with the intersection either at 90 or 45 degrees. Flow visualization is achieved using confocal fluorescence microscopy. The flow interface is examined for equal and unequal viscosities and a range of Reynolds numbers. Viscosity differences and Reynolds numbers influence the three-dimensional nature of the interface. As the Reynolds number increases, the increased flow inertia produces curvature in the interface surface perpendicular to the flow. Curvature is also evident in flows with unequal viscosities. The interface location at fixed flow ratios is independent of the Reynolds number, but varies significantly with unequal viscosity ratios. Viscosity and Reynolds number effects are similar in both the 45 and 90 degree configurations.
Simulation of Residual Stress in Lens Deposited H13 Tool Steel on Copper Substrate
Authors: Talukdar Tushar K. , Wang Liang , Felicelli Sergio D.
Published: August 2012

Solidification cracking represents a significant scientific and technical challenge in the rapid fabrication of bimetallic parts involving Cu and H13 tool steel. The main cause of the cracking formation is attributed to the residual stress accumulation, which depends on the thermal history and phase transformation during the deposition. In this research, a thermomechanical three-dimensional finite element model is developed to determine the temperature history and residual stress in Cu-H13 samples deposited by the Laser Engineered Net Shaping (LENS) process. The development of the model was carried out using the SYSWELD software package. The metallurgical transformations are taken into account using the temperature dependent material properties and the continuous cooling transformation diagram. Two different scanning strategies — alternative and unidirectional — are studied. The same model is also applied to a H13-H13 sample to compare the results. The input laser power is optimized for each layer and three different scanning speeds to maintain a steady molten pool size. It is observed that for a constant scanning speed the required laser power decreases with addition of more layers, and with the increase of scanning speed the laser power needs to be increased. The residual stress is found to be compressive near the center of the deposited wall and tensile at the free edges, which is consistent with the published experimental results in the literature. Similar stress distributions are obtained for both scanning strategies with higher stress concentration at the free edges of the interface between the substrate and the first layer. In these regions, the use of H13 substrate results in a higher stress accumulation than the Cu substrate.
Effects of Crown Fuel Bulk Density Distribution and Thermophoresis of Soot Particles on Wildland Fires
Authors: Dahale Ambarish R. , Dover Selina , Shotorban Babak , Mahalingam Shankar
Published: August 2012

The roles of two physical effects in wildfire are explored through simulations in this study. They are the spatial variation of the bulk density of crown fuel and the thermophoresis forces acting on the produced soot particles. The spatial variation of crown fuel bulk density is modeled as a function of shrub height. This function is available from experimental measurements carried out on Chamise, as crown fuel, in a previous study. In the current study, it is shown that flame spread rate and crown fire initiation are two global parameters considerably affected when the spatial variation of the bulk density is taken into account. Also, it is indicated that thermophoresis forces on soot particles have a significant impact on the evolution of solid- and gas-phase temperature in the upper region of crown fuel; however, other fire propagation characteristics are not considerably affected by these forces. In the simulations, turbulence is modeled with the large eddy simulation and radiation is modeled with the discrete ordinate method. Mass, momentum, and energy transfer between gas and solid-fuel phases are modeled through coupling terms.
Cylinder-Slider Parallel Manipulators for Singularity-Free Path Generation
Authors: Zhou Hong , Mallampati Phani Kumar , Perivilli Venkata Krishna
Published: August 2012

A challenge for cylinder-slider parallel manipulators is their limited workspace and singularity-free path generation. In this paper, the linkage feasibility conditions are derived based on the elimination of dead point position within the workspace. The workspace is generated using the curve-enveloping theory. The singularity-free path generation capability is analyzed. The performance index contours within the workspace are produced using the condition number of the manipulator Jacobian matrix. This paper shows that five-bar cylinder-slider parallel manipulators can be used as effective singularity-free path generators if properly designed. The results of this paper provide a useful map for designing this type of parallel manipulator.
Numerical Analysis of Airside Characteristics in Plain and Wavy Heat Exchangers in the Turbulent Flow Regime
Authors: Amin M. Ruhul , Ramachandran Santhosh K.
Published: August 2012

Numerical investigation has been performed to study the heat transfer and pressure drop characteristics of plain-fin-tube and wavy-fin tube heat exchangers. Performance results are presented in terms of non-dimensional parameters, friction factor and Colburn factor. The flow rate is varied over the range of 2000 ≤ ReH ≤ 7000 in the turbulent regime. The analysis was performed using a finite volume method. Comparisons with experimental data are performed to validate the code. Parametric study is performed to investigate the effects of transverse pitch and wavy angle. It is observed that an increase in transverse pitch results in a decrease in thermal and hydraulic characteristics. On the other hand with the increase of wavy angle, resulting in the increase of the number of corrugations, both the friction factor and Colburn factor increased. The critical balance between high heat transfer and pressure drop is analyzed using the efficiency index. The tube layout in the staggered form is seen to have better heat transfer characteristics than the in-lined layout for both the configurations.