bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigations of Droplet Deposition and Coalescense in Curved Pipes
Authors: Nguyen Hung , Wang Shoubo , Mohan Ram S. , Shoham Ovadia , Kouba Gene
Published: October 2013

Even though there have been several studies conducted by the industry on the use of different inlet devices for gas-liquid separation there have been limited laboratory and field evaluations on the use of external piping configurations as flow conditioning devices upstream of a separator inlet. The results of a systematic study of droplet deposition and coalescence in curved pipe and pipe fittings are reported in this paper. A facility has been designed consisting of two main test sections: a fixed horizontal straight pipe section and an interchangeable 180° return pipe section (or curved pipe section) of the same length. Both inlet and outlet to the 180° return are horizontal, but the plane of the 180° return pipe section can pivot about the axis of the inlet horizontal pipe to an angle as much as 10° downwards allowing downward flow in the return section. Various pipe fittings of different radius of curvature can be installed for comparison in the 180° return. Fittings evaluated in this study included: 180° pipe bend, 2 standard radius elbows (with radius of curvature of 1.5D), 2 long radius elbows (with radius of curvature of 6D), 2 target tee bend, and 2 cushion tee bend. Experiments have been carried out using water and air and varying gas velocities and liquid loadings. In order to compare the performance of geometries, Droplet Deposition Fractions (DDF) were measured in the horizontal straight pipe section and in the 180° return pipe section as a measure of coalescence efficiency. The results demonstrate that higher DDF occurs for curved fittings as compared to the straight pipe section. Two standard (short) radius elbows bend have approximately 10% DDF higher, whereas two long radius elbows along with 180° pipe bend perform better (by 15–20% DDF) than straight pipe. Additionally, no significant differences between DDF’s in three different inclination angles of a curved pipe were observed. It was found that the cushion tees and target tees can coalesce droplets at lower gas velocities but break up droplets at higher gas velocities. It can be concluded that 180° pipe bend or two 6D long radii elbows can serve as a droplet coalescer, a pair of cushion tees or target tee can also work as coalescer at low kinetic energy but as atomizers at high kinetic energy.
Responsible Conduct of Research in Computational Modeling
Authors: Wilson Sara E. , Keefer Matthew W. , Dankowicz Harry , Loui Michael C.
Published: October 2013

Computational modeling is a growing area of mechanical engineering that focuses on the use of numerical simulation to examine complex phenomena. Computational modeling includes work in finite element analysis, computational fluid dynamics, and multi-body dynamics modeling. Intrinsic to most of these modeling efforts are common elements including:

1. Assumptions that are made to reduce a problem to a solvable mathematical problem,

2. Formulation of a mathematical representation based on scientific principles,

3. Reduction of the mathematical representation through the removal of terms of small effect (neglected terms)

4. Collection and use of input data,

5. Algorithm development using numerical methods and discretization of the mathematical problem,

6. Implementation of the algorithm in computer code,

7. Creating representations of the model results,

8. External validation of the model, and

9. Dissemination of the model and model computer code.
Performance and Economic Analysis of Biomass/Coal Co-Gasification IGCC Systems With Supercritical Steam Bottom Cycle: Part 2 — Pre-Combustion Carbon Capture
Authors: Wang Ting , Long Henry A.
Published: October 2013

One of the main advantages of IGCC technology is that it is the only form of power generation that is compatible with pre-combustion carbon capture. Part 2 of this paper will thus focus on analyzing pre-combustion CCS, utilizing both sour-shift and sweet-shift processes and comparing them to each other and to the results of post-combustion CCS from Part 1. Pre-combustion CCS plants are smaller than post-combustion ones, and usually require 25% less energy for CCS due to their compact size for processing fuel flow only under higher pressure (450 psi), versus processing the combusted gases at near-atmospheric pressure. For pre-combustion CCS, sour-shift appears to be superior both economically and thermally to sweet-shift in the current study. Sour-shift is always cheaper, (by a difference of about $600/kW and $0.02-$0.03/kW-hr), easier to implement, and also 2–3 percentage points more efficient.

Adding biomass to the system always reduces the emissions and can even make a plant carbon-negative with as little as 10% biomass by weight. In addition, the efficiency will improve (0.7 points) and power output will also improve (∼1%–3% more) for up to 10% biomass ratio (BMR) for the right kind of biomass that has been properly pretreated. Beyond 10% BMR, however, the efficiency begins to drop due to the rising pretreatment costs, but the system itself still remains more efficient than from using coal alone (between 0.2–0.3 points on average). The economic difference is fairly marginal, but the trend is inversely proportional to the efficiency, with CoE decreasing by 0.5 cents/kW-hr from 0%–10% BMR and rising 2.5 cents/kW-hr from 10%–50% BMR. Finally, the CO2 removal cost for sour-shift is around $20/ton, whereas sweet-shift’s cost is around $30/ton, which is much cheaper than that of post-combustion CCS from Part 1: about $60-$70/ton.
Thermoeconomic Model for the Energy Optimization of Industrial Air Compressed Supply Network Under Transient Condition
Authors: Corredor M. Lesme , Guillen Diego , Prada José , Contreras Alisson
Published: October 2013

Air compression represents around 20% of industrial total electric power demand, especially in chemicals and process companies. Few technical studies related with energy optimization of air compressed networks are reported in the specialized literature, in contrast, in natural gas and steam networks have been widely analyzed. Pressure, temperature and flow monitoring of air compression is not enough for implementation of energy optimization models, for this reason authors have developed a transit conditions model which takes into account air supply equipments and air compressed process requirements. This paper presents a decision support system for the scheduling selection of a set of air compressors in an industrial plant based on energy demand minimization.

Several constraints must be taken in consideration during the optimization process, this can be desegregate in two types, the first set of constrains was used for simulate the operation of scroll, screw and centrifuges compressors, the second based in graph an node theory and contain the mathematical transit conditions model of supply air network topology, for the complexity of the problem the use of a genetic algorithm to search an optimal combination was necessary.
An Active Heat Sink System With Piezoelectric Translational Agitators and Micro Pin Fin Arrays
Authors: Yeom Taiho , Simon Terrence W. , Yu Youmin , Zhang Min , Agrawal Smita , Huang Longzhong , Zhang Tao , North Mark T. , Cui Tianhong
Published: October 2013

Conventional heat sink systems with blowers or fans are approaching maximum thermal management capability due to dramatically increased heat dissipation from the chips of high power electronics. In order to increase thermal performance of air-cooled heat sink systems, more active or passive cooling components are continually being considered. One technique is to agitate of the flow in the heat sinks to replace or aid conventional blowers. In the present study, an active heat sink system that is coupled with a piezoelectric translational agitator and micro pin fin arrays on the heat sink surfaces is considered. The piezoelectric translational agitator generates high frequency and large displacement motion to a blade. It is driven by an oval loop shell that amplifies the small displacement of the piezo stack actuator to the several-millimeter range. The blade, made of carbon fiber composite, is easily extended to a multiple-blade system without adding much mass. The micro pin fin arrays were created with the LIGA photolithography technique. The cooling performance of the heat sink system was demonstrated in single-channel and multiple-channel test facilities. The singlechannel test results show that the active heat sink with the agitator operating at a frequency of 686 Hz and peak-to-peak displacement of 1.4 mm achieved a low thermal resistance of 0.053 C/W in a channel with a 7.9 m/sec flow velocity. Different configurations of the translational agitator with multiple blades were fabricated and tested in a 26-channel, full-size heat sink. Vibrational characteristics are also provided.
Cultivating Photosynthetic Bacteria in a Planar-Stack Optofluidic Photobioreactor
Authors: Pierobon Scott C. , Ooms Matthew D. , Samsonoff Nathan G. , Sinton David
Published: October 2013

Our current work on planar optofluidic photobioreactors will be presented including spatial characterization of the evanescent field as well as biofilm growth results. A reactor design which constitutes the smallest repeating unit of a stacked photobioreactor configuration is presented for the purpose of biofilm density studies.
Shape Comparison for Solar Thermal Parabolic Collector
Authors: Hernandez Kristian , King Ryan , Lauth Joseph , Sharp Joshua , Wittman Eric , Depcik Christopher
Published: October 2013

The KU EcoHawks are a mechanical engineering, undergraduate, senior design group at the University of Kansas that focuses on projects emphasizing a sustainable approach to automobiles and energy infrastructure. Much of the EcoHawks construction work is completed at a barn on campus that does not currently contain a heating or air conditioning system. Due to the temperature extremes reached in Kansas during the summer and winter months, thermal comfort is problematic for students working within the barn. This past academic year, one design group implemented a heating system for the barn utilizing a solar thermal parabolic collector. During the design phase, research of the literature found relatively little information in regards to the optimized depth of the parabolic curve. As a result, a prototype solar thermal parabolic trough was built in order to test three different parabolic shapes with varied depths. Static testing of a 50-50 mix of ethylene glycol and water found that the parabolic shape with the smallest focal length had the greatest solar collection efficiency. From this assessment, a final parabolic trough design was created. The assumptions, testing procedure, and results of static testing for the optimum parabolic shape of a solar trough collector will be addressed herein.
Effective Dynamic Properties of Microstructured Heterogeneous Materials
Authors: Srivastava Ankit , Nemat-Nasser Sia
Published: October 2013

Central to the idea of metamaterials is the concept of dynamic homogenization which seeks to define frequency dependent effective properties for Bloch wave propagation. While the theory of static effective property calculations goes back about 60 years, progress in the actual calculation of dynamic effective properties for periodic composites has been made only very recently. Here we discuss the explicit form of the effective dynamic constitutive equations. We elaborate upon the existence and emergence of coupling in the dynamic constitutive relation and further symmetries of the effective tensors.
Fabrication of Polyurethane Based Fabric Composite Shaft and its Experimental Study Under Triple Point Bending
Authors: Mitra Aniruddha , Salekeen Sirajus , Rahman Mosfequr
Published: October 2013

Semi-rigid urethane based fiber composite shafts are fabricated by high pressure injection molding process. The samples are made in Georgia Southern University’s laboratory where compressed air pressure is effectively used for this purpose. A special manufacturing process is suggested which can be used for mass production of these composites. This unique manufacturing technique creates a composite shaft with a core made of matrix material which is completely wrapped around by a woven fiber cloth with a very strong bonding between core and fibers. Three different types of woven fibers: fiber glass, Kevlar 49, and carbon fibers, are used. Triple point bending tests are carried out to test these three different types of composite samples and also samples made of only base or core material. During the test as the applied load is increased, a linear trend is observed between the load and mid-point deflection of the specimens up to a certain level. Higher load causes separation of fibers and core matrix and followed by local buckling of the separated fibers that are under compression region. This phenomenon brings down the bending stiffness of the composite significantly and it is quite pronounced in the load deflection curve diagram. Failure modes are observed to differ for each of these three types of composite and are discussed in details here. Composites with fiber glass wrapping are found to be the strongest among the three. Future work will involve determining the torsional and fatigue properties, and also the effect of fiber orientations on the mechanical properties of these composites.
Photon Monte Carlo Model for High-Pressure Reacting Laminar Flows
Authors: Lei Shenghui , Cai Jian , Dasgupta Adhiraj , Modest Michael F. , Haworth Daniel
Published: October 2013

In this paper, laminar H2-air flames at elevated pressures up to 10 bar are numerically studied. To capture the influence of radiation on high-pressure flames, a photon Monte Carlo (PMC) scheme combined with a spectral line-by-line (LBL) method previously developed by the authors is employed. In the present problem, the only radiating species is H2O. The importance of radiation in high-pressure flames is demonstrated by comparing differences of temperature and concentration fields for the cases with and without radiation.
Strain-Rate Sensitive Constitutive Modeling of Anisotropic Visco-Hyperelastic Materials
Authors: Ahsanizadeh Sahand , Li LePing
Published: October 2013

Integral-based formulations of viscoelasticity have been widely used to describe the mechanical behavior of soft biological tissues and polymers. However, it is suggested that they are not suitable to be used under high strain rates. On the other hand, strain-rate sensitive models with an explicit dependence on the strain-rate have been developed for a certain class of materials. They predict the viscoelastic behavior during ramp loading more accurately while fail to account for the relaxation response. In order to overcome these drawbacks, a viscoelastic constitutive model has been proposed in this study based on the concept of internal variables. While the behavior of elastic materials is uniquely determined by the current state of deformation or external variables, the mechanical response of inelastic materials are regulated also by internal variables. The internal variables are associated with the dissipative mechanisms in the material and along with the evolution equations introduce the effect of history of the deformation to the current configuration. The current study employs short-term and long-term internal variables to account for the viscoelastic response during loading and relaxation respectively.
Cohesive Fracture Mechanics Based Finite Element Analysis to the Performance of Lead Free Solders in BGA Packaging Under Drop Impact
Authors: Yao Yao
Published: October 2013

Lead free solders are replacing lead rich solders in the electronic industry, the performance and safety of lead free solder joints in electric packaging under drop impact becomes a critical concern of semiconductor and electronic product manufacturers. Compared with the lead rich solder alloy, lead free solder alloy typically has higher rigidity and lower ductility. The presence of the Intermetallic Compound (IMC) layer can also affect the drop impact response of the solder interconnect, which may lead to quasi-brittle solder/IMC interfacial fracture. The traditional drop test is expensive and time consuming, and it is quite difficult to observe the full dynamic responses during the drop impact. In the present study, numerical analysis is performed to investigate drop impact effect on ball grid array (BGA) electronic packaging with the intention of predicting the performance of solders under drop impact and providing the fundamental understanding required to design a reliable electric packaging. A three dimensional finite element model is developed to simulate the solder interconnect and electronic packaging failure under board-level drop impact. An impact analysis procedure coupled with sub-modeling technique is established. The Cu6Sn5 and Cu3Sn IMC layers are incorporated in the solder interconnects model; cohesive fracture mechanics based method is applied to predict the crack initiation and propagation near the IMC/solder interface. A lead-free solder alloy constitutive relationship comprising elastic and rate dependent plastic effects is incorporated in the computational model. The mechanical shock is the main failure mechanism of solder joint during drop impact. The susceptible failure location is concluded at the interface between the solder and intermetallic compound based on the stress criteria. The developed model can be used to compare the drop impact performance of different components and solder alloys, which can guide the proper selection of component and optimize the layout of BGA electric packing. The behavior of electric packaging and different types of solder interconnects under drop impact can be predicted with corresponding material parameters determined from experiment.
Effect of Anode Surface Roughness on Power Generation in Microbial Fuel Cells
Authors: Ye Zhou , Hou Junbo , Ellis Michael W. , Behkam Bahareh
Published: October 2013

A three-electrode system was used to study the effect of anode surface roughness on the performance of microbial fuel cells (MFCs). Two glassy carbon plates were polished to uniform roughness of the orders of magnitude of 10s of nm and 100s of nm. Atomic force microscopy (AFM) was used to quantify the roughness as well as the 3D topography of the surfaces. Multiple electrochemical methods including potentiostatic tests, potentiodynamic tests, and electrochemical impedance spectroscopy (EIS) were utilized to monitor the performance of the glassy carbon electrodes. After 275 hours of experimentation, the current density generated by the rough electrode was much higher than that generated by the smooth one. Furthermore, the charge-transfer resistance of the rough electrode was lower than that of the smooth one. The better electrochemical performance of the rough surface may be due to denser biofilm grown on the surface, which was observed by scanning electron microscopy (SEM).
A Study of Thermal Effectiveness of Laminar Forced Convection of Nanofluids
Authors: Yu Leyuan , Liu Dong
Published: October 2013

Recent theoretical studies show that the convective thermal performance of nanofluids in cooling applications depends crucially on the effective thermophysical properties and, if the performance comparisons are made under different flow constraints, contradictory conclusions can be drawn regarding the effectiveness of the same nanofluid. In this work, an experimental study was reported on the laminar forced convection of Al2O3-water and Al2O3-Polyalphaolefin (PAO) nanofluids through a circular minichannel. Based on the experimental data, the thermal effectivenesses of the nanofluids were evaluated critically using various figures of merit (FOM) under three typical flow constraints, i.e., constant flow rate, constant Reynolds number and constant pumping power. Although the nanofluids enhance convective heat transfer, the results show their overall thermal effectiveness is adversely affected by the combined effects of higher viscosity and lower specific heat. In particular, when the cooling application is constrained by the constant pumping power condition, there is virtually no difference in the thermal performances between the base fluid and the nanofluids.
The Complementary Nature of CO2-Plume Geothermal (CPG) Energy Production and Electrical Power Demand
Authors: Adams Benjamin M. , Kuehn Thomas H.
Published: October 2013

CO2 Plume Geothermal (CPG) energy generation is a renewable technology that uses CO2 as the geologic working fluid within naturally permeable, sedimentary thermal reservoirs. In this paper, we compare the ability for CPG geothermal technology to meet electrical demand requirements, compared with other renewable technologies, for a 10MW, northern climate town near Minot, North Dakota. Wind and solar are both supply-driven technologies, capturing energy when it is available; However CPG is demand-driven—the rate at which energy is removed from within the earth is chosen to meet electrical demand. Using meteorological data, we compare estimated system performance with actual 2010 electrical load to gage each system’s ability to meet demand.

CPG is found to most closely match system demand during the three-season (fall, winter, spring) year, where solar production is inversely related to demand. At the same time, wind does not track demand during any portion of the year, consistently having a large variability. None of these renewable technologies was found to track demand all year. Ultimately we show that CPG may be used to reliably track hourly demand during 95% of the year—an unattainable result for wind and solar.
Energy Use Comparison of Air Distribution Systems Serving a Section of a School Building
Authors: Jordan Stillman , Manteufel Randall D.
Published: October 2013

An optimal air distribution design accomplishes both comfort and ventilation requirements while consuming as little energy as possible. This paper analyzes four different air distribution systems and technologies including single duct variable air volume air handlers, chilled beam cooling systems, total energy recovery wheels, displacement ventilation, and dedicated outside air systems; in an effort to determine the best air distribution system for a representative section of a school in hot and humid climate. The effectiveness of the air distribution systems is evaluated by analyzing how the different technologies take advantage of the natural convective properties of air to create a comfortable environment for the occupied region of the space. Distribution effectiveness and energy consumption must be weighed against considerations such as system complexity and ease of operation.

This paper compares several alternative air distribution systems to a baseline single inlet VAV system that is commonly used in new schools designed today. Calculations show that the total energy recovery wheels result in a 16% energy savings over the baseline air distribution system because of the large amount of outside air required in school buildings. Chilled beams are not well suited for schools because of the large amount of outside air required by the space and the sophisticated design and operation needed to prevent condensation from occurring at the chilled beam. The results show that the air distribution system that consumes the least amount of energy is a displacement ventilation system. The system also inherently promotes better indoor air quality as it allows air to naturally rise out and return out of the space with minimal mixing of contaminates that may be recirculated within the room for others to breath. The displacement ventilation system’s overall energy savings of 20% over the baseline is mainly attributed to its total energy recovery wheel and the system’s ability to drastically reduce the cooling load seen by the air cooled chiller by effectively ventilating spaces using less outside air.
Measurement of Thermal Conductivity and Interface Thermal Resistance of Multilayered Thin-Films Using Variable Pulse-Width Transient Thermoreflectance
Authors: Burzo Mihai G.
Published: October 2013

This work discusses the use of a non-contact, non-invasive and in-situ measurement approach for determining the thermal conductivity of thin films used in the microelectronics industry, along with the interface thermal resistance between the films. The approach is based on the thermoreflectance method, where the change in the surface temperature is measured by detecting the change in the reflectivity of the sample. The results presented in this paper show that by using different pulse-widths for the heating laser, as well as a variable wavelength for the probing laser, the proposed method enables the measurement of several unknown parameters in a multi layered sample, which is representative of modern devices developed by the microelectronics industry. In addition, it is shown that the method can be further improved to minimize the measurement uncertainties by estimating a-priori the optimum thickness of the metal absorption layer that needs to be used. A property called responsivity is described, and it is shown that maximizing its value is indeed producing the lowest measurement uncertainties. An objective of this work is to provide guidance to investigators building similar systems and help others improve existing systems.
Design of a Multiple-Actuation Shape Memory Alloy Pipe Coupler: Material Development and Characterization
Authors: Tabesh Majid , Rohmer John , Boyd James G. , Lagoudas Dimitris C. , Atli Kadri C. , Franco Brian E. , Karaman Ibrahim
Published: October 2013

Shape memory alloy (SMA) pipe couplers use the shape memory effect to apply a contact pressure onto the surface of the pipes to be coupled. In the current research, an SMA pipe coupler is designed, fabricated and tested. The thermally induced contact pressure depends on several factors such as the dimensions and properties of the coupler-pipe system. An in-house developed NiTi alloy system is considered for the coupler. The coupling pressure is measured using strain gages mounted on the internal surface of an elastic steel ring. Thermal actuation response of the coupler is determined under both stressed and stress-free conditions. In addition, the state of anisotropy is investigated in the coupler by characterizing samples in the longitudinal and transverse directions. Unlike the commercially available NiTiNb couplers, the NiTi coupler demonstrates a multiple actuation response and higher contact pressure. The state of anisotropy is investigated in the couplers by characterizing samples in the longitudinal and transverse directions. The results show no change in transformation temperatures with respect to two perpendicular transverse and longitudinal directions, however, the material can undergo higher transformation strains in the longitudinal direction.
Learning Outcomes From Design of Wind Turbines Carried Out by Underserved High School Mentees Participating in DREAM
Authors: Valley Kyle J. , Nguyen Leslie Q. , Rodela Alejandro , Houchens Brent C.
Published: October 2013

The fall 2011 DREAM design project required teams to design and build a working wind turbine. The turbines were tested at three wind speeds, with the most points awarded for power production at the lowest speed, forcing mentees to optimize their blade designs. The Pre-engineering Concept Inventory (PCI) and Intuition Inventory (II), which focus on wind energy, were used to measure pre- and post-content knowledge of high school mentees. The use of mini-lectures to convey content simultaneously with design is discussed.

The Inventories show that participation in DREAM generally increases mentees’ understanding of wind energy concepts. However, insufficient mathematics foundations hamper their ability to understand algebraic representations and evaluate numerical predictions. Results provide feedback on current practices and help pinpoint specific areas for improvement to increase the efficacy of DREAM in future years.
Airfoil Optimization for Small Wind Turbines Using Multi Objective Genetic Algorithm
Authors: Ram Krishnil R. , Lal Sunil , Ahmed M. Rafiuddin
Published: October 2013

Small wind turbines are gaining popularity due to their ability to meet community or domestic needs in isolated areas with relatively easier installation and lower cost than large wind turbines. This study looks at optimizing airfoils for use in small horizontal axis wind turbines. The optimization looks to maximize the lift coefficient (Cl) while minimizing or fixing the drag coefficient (Cd). To satisfy these two objectives a multi–objective genetic algorithm is used. The airfoil is parameterized using a composite Bezier curve with two Bezier segments and 11 control points. Appropriate curvature conditions are implemented at the leading and trailing edge of the airfoil and geometric constraints are applied to maintain the maximum thickness between 8% to 14% of the chord for structural reasons. An existing genetic algorithm (GA) code is modified in C++ to generate suitable airfoils using the 13 control points and pass the coordinates to a solver for analysis. As a result four new airfoils are generated for application in low Reynolds number (Re) flow. The characteristics and suitability of the four airfoils are discussed while comparing them to the popular SG6043 airfoil.
Optimization of Cell Configuration for Maximizing Performance of a Cu/Cu2+ Aqueous Thermogalvanic Cell
Authors: Lin Chao-Han , Gunawan Andrey , Phelan Patrick E. , Buttry Daniel A. , Mujica Vladimiro , Taylor Robert A. , Prasher Ravi
Published: October 2013

This paper presents experimental results and analysis of a new high-power Cu/Cu2+ thermogalvanic cell and its comparison with previous results. Past researches were mostly focused on finding the best redox couples and electrode materials [1, 2], however, they generally lacked a comparison of power conversion efficiency (η) dependence on cell geometry. This inspired our interest in exploring the relation of η, internal resistance, maximum power, and cell geometry. Based on previous results [3], a low internal resistance, variable orientation thermogalvanic cell was designed to achieve the highest power output. Experimental results of the Seebeck coefficient (α = ∂E/∂T), power density, and η of Cu/Cu2+ electrolytes in various molar concentrations showed that 0.7M CuSO4 electrolyte has maximum α and power output of 0.7196 mV/°C and 3.17 μW/cm2, respectively. Power output of the new cell has significant improvement which is 219 times greater than previous research. This paper also presents economical aspects of Cu/Cu2+ thermogalvanic cells relative to ferri/ferrocyanide cells.
Electric Field Gradients in Micro/Nanofluidic Devices
Authors: Kazemlou Shokufeh , Nazemifard Neda
Published: October 2013

Electrokinetic is one of the most common tools used to control the transport phenomena in micro/nanofluidic devices. To design a successful process, it is important to have a precise knowledge of parameters affecting electrokinetic transport. One of these parameters is the applied electric field. When the local values of the electric field deviate significantly from the nominal values, the assumption of a homogeneous field is an oversimplification resulting in failed or low efficiency processes. In this manuscript, the sources of inducing field gradients and their implications were investigated. Of particular interests are micro-fabricated arrays used extensively in microfluidic devices either as sieving matrices or mixing enhancers. A comprehensive parametric study was conducted to understand how the posts arrangements (hexagonal and square), distance and size, and surface charge change the field gradients. Our results provide criteria at which the assumption of uniform field is valid, which can have important implications in designing microfluidic units where either a high field gradient is favored (mixing) or not (separation).
A Petri-Net Model for Machine Structure Configuration Approach
Authors: Hasan S. Maaz , Baqai Aamer Ahmed , Azam M. Nadeem
Published: October 2013

Machine Structure configuration approach is used to find the machine configuration required for the machining operations of any given part. This paper presents a Petri-net model for the approach. This model not only simplifies the approach, the Petri-net model of the given part remains simplified even if the number of machining features is high. A case study is taken as an example, the model is applied on it and the results are then compared with the available data. Conclusions are drawn after the application of both the conventional and the Petri-net model on the part. After that the applicability of the Petri-net model of machine structure configuration approach on different part families is discussed. In the end the suggestions for future trend are presented.
Thermal Convection in an Enclosure With Sinusoidal Bottom Wall Temperature: Effect of Vibrating Side Wall
Authors: Aktas Murat K.
Published: October 2013

The effects of a vibrating side wall on flow structure and heat transport in an air-filled two dimensional rectangular shallow enclosure with sinusoidal spatial bottom wall temperature distribution is studied numerically. The vibrating side wall induces an oscillating flow having nonzero mean component in the enclosure. The side walls of the enclosure are adiabatic. The top wall is isothermal and kept at initial temperature. The fully compressible form of the Navier–Stokes equations are considered to predict the oscillatory and time averaged mean flow fields. A control-volume method based, explicit computational scheme is used to simulate the convective transport in the enclosure. The simulation results of a test case for an unheated enclosure are compared with the existing literature for code validation. The sinusoidal temperature gradient of the bottom wall strongly affects the flow structures and velocities. The mean fluid motion significantly alters the overall heat transfer from the bottom wall.
Stakeholder-Driven Design Evolution of the Leveraged Freedom Chair Developing World Wheelchair
Authors: Winter Amos G. , Bollini Mario A. , Judge Benjamin M. , Scolnik Natasha K. , O’Hanley Harrison F. , Dorsch Daniel S. , Mukherjee Sudipto , Frey Daniel D.
Published: October 2013

The Leveraged Freedom Chair (LFC) is a low-cost, all-terrain, variable mechanical advantage, lever-propelled wheelchair designed for use in developing countries. The user effectively changes gear by shifting his hands along the levers; grasping near the ends increases torque delivered to the drive-train, while grasping near the pivots enables a larger angular displacement with every stroke, which increases angular velocity in the drivetrain and makes the chair go faster. This paper chronicles the design evolution of the LFC through three user trials in East Africa, Guatemala, and India. Feedback from test subjects was used to refine the chair between trials, resulting in a device 9.1 kg (20 lbs) lighter, 8.9 cm (3.5 in) narrower, and with a center of gravity 12.7 cm (5 in) lower than the first iteration. Survey data substantiated increases in performance after successive iterations. Quantitative biomechanical performance data were also measured during the Guatemala and India trials, which showed the LFC to be 76 percent faster and 41 percent more efficient during a common daily commute and able to produce 51 percent higher peak propulsion force compared to conventional, pushrim-propelled wheelchairs.
Enhancement of Forced Convection in Ribbed Channels by Nanofluids
Authors: Manca O. , Nardini S. , Ricci D.
Published: October 2013

The enhancement technologies in convection heat transfer allow the effectiveness improvement of heat exchangers. The employment of rough surfaces could be taken into account. In fact, in a ribbed channel, turbulators break the laminar sub-layer and create local turbulence in order to reduce the thermal resistance and augment heat transfer rates. Another available technique is represented by the introduction of nanoparticles in the base fluids in order to improve the fluid thermal conductivity. However, both the methods provide increasing pressure drops.

In this paper a numerical investigation is carried out on water-Al2O3 nanofluid forced convection in a two-dimensional ribbed channel, heated by a constant heat flux. Ribs have trapezoidal shapes and different geometric arrangements were analyzed. The mixture model was employed in order to describe the nanofluid behaviour and different nanoparticle volume fractions were considered. The aim consists into describe the thermal and fluid-dynamic performances of ribbed channels filled with Al2O3/water based nanofluids in the turbulent regime. Results show increasing heat transfer rates as particle concentrations and Reynolds numbers increase but higher required pumping powers.
Cyclic Breathing Simulations in Large Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles
Authors: Walters D. Keith , Burgreen Greg W. , Hester Robert L. , Thompson David S. , Lavallee David M. , Pruett William A. , Ford-Green Jason
Published: October 2013

Computational fluid dynamics (CFD) simulations were performed for unsteady periodic breathing conditions, using large-scale models of the human lung airway. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to G16) obtained from a stochastically generated airway tree with statistically realistic geometrical characteristics. A reduced-order geometry was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to G16. The inlet and outlet flow boundaries corresponded to the oronasal opening (superior), the inlet/outlet planes in terminal bronchioles (distal), and the unresolved airway boundaries arising from the truncation procedure (intermediate). The cyclic flow was specified according to the predicted ventilation patterns for a healthy adult male at three different activity levels, supplied by the whole-body modeling software HumMod. The CFD simulations were performed using Ansys FLUENT. The mass flow distribution at the distal boundaries was prescribed using a previously documented methodology, in which the percentage of the total flow for each boundary was first determined from a steady-state simulation with an applied flow rate equal to the average during the inhalation phase of the breathing cycle. The distal pressure boundary conditions for the steady-state simulation were set using a stochastic coupling procedure to ensure physiologically realistic flow conditions. The results show that: 1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; 2) the predicted alveolar pressure is in good agreement with previously documented values; and 3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.
Large Deflection 3DOF Piezoelectric Microrobotic Manipulator With Positional Sensing and Self-Calibration
Authors: Jin Xing , Clark Jason V.
Published: October 2013

In this paper, we propose a large deflection piezoelectric microrobotic manipulator with the ability to self-calibrate displacement and sense its position. Such a manipulator should be applicable to scanning probe microscopy, nanolithography, data storage, biological probing in murky aqueous environments, and the like. Previous devices for such applications are limited in dexterity, range of motion, frequency response, positional calibration, or require environmental cleanliness. Our device has a three novel attributes, which are: an ability to achieve large deflections with greater than one degree of freedom (DOF); an ability to self-calibrate it displacement; and an ability to sense its position after actuation or prescribed displacement. Through simulation we demonstrate independent 3 DOF motional control (validated experimentally), positional sensing and self-calibration, and dynamic response.
An Inverse Fire Modeling Methodology for the Determination of Fire Size, Fire Location, and Soot Deposition in a Compartment
Authors: Overholt Kristopher J. , Ezekoye Ofodike A.
Published: October 2013

Fire models are routinely used in life safety design projects and are being used more often in fire and arson investigations as well as reconstructions of firefighter line-of-duty deaths (LODDs) and injuries. In all of these applications, the fire heat release rate (HRR), location of a fire in a compartment, gas-phase soot concentration, and solid-phase soot accumulation are important parameters that govern the evolution of thermal conditions within the fire compartment. These input parameters can be a large source of uncertainty in fire models, especially in scenarios in which experimental data or detailed information on fire behavior are not available, such as fire investigations and LODD reconstructions. Various methods have been reported in literature to determine the size and location of a fire in a compartment using ceiling-mounted detectors [1–4]. A previous study by the authors developed an inverse fire modeling technique to determine the time-varying HRR of fire in a compartment using measured thermocouple data [5]. The work presented in this paper extends the inverse HRR methodology by developing a technique to determine the location of a fire using wall-mounted heat flux sensors or a surrogate such as degradation characteristics of enclosure boundaries that can be collected during post-fire assessments. Additionally, the presence of soot modifies the radiative transfer field in the hot gas layer (gas phase) as well as radiative heat transfer to surfaces (condensed phase). As a detailed history of compartment conditions becomes less available, there is a need for an inversion methodology to accurately recover governing input parameters such as fire size, fire location, and fire burning properties while maintaining an adequate level of accuracy. As an intermediate step using measured fire test data, we can begin to construct an approach to use rich data to invert for fire intensity, fire location, and fire properties such as the amount of soot produced by the fire.
Thermal-Mechanical Response of Non-Uniformly Heated Nominally Flat and Curved LEU Foil Based Target
Authors: Turner Kyler K. , Solbrekken Gary L. , Allen Charlie W.
Published: October 2013

Technetium-99m is a radiopharmaceutical currently used in 85% of all diagnostic imaging procedures. The relative long lived parent isotope of technetium-99m is molybdenum-99, which is commonly produced by irradiating highly enriched uranium. In accordance with the Department of Energy: National Nuclear Security Administration’s Global Threat Reduction Initiative an effort is underway to develop low enriched uranium based molybdenum-99 production concepts. Achieving comparable molybdenum-99 yields in a low enriched uranium target effectively mandates the use of a high density metal low enriched uranium foil. Using a foil requires a significant modification to the current highly enriched uranium dispersion target designs. One design concept uses a low enriched uranium foil sandwiched between either two flat or curved aluminum plates. The low enriched uranium is enclosed in the sandwiched structure by welding the aluminum plates together about their edges. The plate design is inspired by low enriched uranium fuel plates with the exception that the low enriched uranium is not bonded to the aluminum plates nor is it necessary to clamp the plate edges to prevent lateral translation. The lack of bonding between the low enriched uranium foil and the plates allows easy removal of the foil after irradiation for chemically processing and separation. The un-heated edges of the plate target produce three-dimensional temperature gradients inducing deformations and stress. This paper will review the thermal mechanical response of a low enriched uranium foil based molybdenum-99 production target. This study describes the effect of various curvatures, thermal loads, and heat transfer coefficients on the thermal-induced deflection and stress.
Dynamic Response Analysis for Cracked Beam With Considering the Effect of Reinforced Constraints
Authors: Chan Deliang , Wang Wenting , Dai Liming , Liu Feng
Published: October 2013

Based on the theory of elasticity mechanics and fracture mechanics, the cracked concrete beam with the effect of reinforced constraints is modelled and analyzed by the energy angle, and the governing equation is established using Reissner variation principle. Then in numerical calculation, the effects of geometry nonlinear, structural damping, crack parameters, as well as the reinforced constraints on dynamic response of beam under the rectangular pulse load is investigated. The motion laws of cracked beam are discussed and summarized.
FEM Analysis of the Effects of Cooling Techniques on the Microstructure of Aluminum 7075 Friction Stir Welded Joints
Authors: Kheireddine A. H. , Ammouri A. H. , Hamade R. F. , Kridli G. T.
Published: October 2013

Friction stir welding (FSW) is a proven solid-state technique for joining metal alloys. Given the low melting temperatures of light alloys, excessive heat build-up in such joints may have undesirable consequences such as melting and/or undesired grain growth. It is widely recognized that the resulting mechanical properties of a welded joint depends to a great extent on microstructure development.

The aim of this paper is to improve the microstructure of friction stir welded aluminum alloy joints by utilizing two different cooling techniques. To this end, a 3D FEM model is developed to simulate the friction stir welding plunging and advancing phases. The parameters used in the FEM model were optimized for minimum simulation time and resulting in accurate simulations as compared with experimental results previously published by other workers. The work material was modeled as a visco-plastic material and dynamic recrystallization was implemented and added to the material model. Two main cooling techniques were compared: temperature controlled backing plate and another via cryogenic CO2 direct nozzle. The monitored output parameters were: temperature, stress, strain, and strain rate. Consequently, values of the Zener-Hollomon parameter, Z, were calculated and the resulting grain size distribution in the joint was found. Due to dynamic recrystallization, nano-sized grains were predicted to be generated in the cryogenically cooled weld line when compared to non-cooled one.
Estimation of Modulus of Elasticity for Closed-Cell Aluminum Foam
Authors: Ahmadian M. T. , Gobal A. , Alkhani R.
Published: October 2013

Monodisperse closed cell aluminum foam was analyzed numerically to determine the relationship between its elastic modulus, porosity and pore diameter. It was found a nonlinear relationship exists between porosity, pore diameter and modulus of elasticity. In this regard, an empirical equation is developed and implemented for the prediction of modulus of elasticity versus porosity and pore diameter. Comparing experimental and analytical approaches by other researchers with those obtained in this research shows agreement exists within 1 to 3 percent.