bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Validation of a Roll Simulator for Recreational Off-Highway Vehicles
Authors: Zagorski Scott B. , Guenther Dennis A. , Heydinger Gary J. , Sidhu Anmol S. , Andreatta Dale A.
Published: August 2012

A model of a roll simulator for recreational off-highway vehicles (ROV) is presented. Models of each sub-system are described including the equations of motion, the braking, hydraulic and roll motor systems. Derivation of the equations of motion, obtained using Lagrange’s energy equation, demonstrates that they have three degrees-of-freedom (two dynamic, one static) and are coupled and highly non-linear. Results from the hydraulic sub-system illustrated that the amount of entrapped air in the system can significantly influence the response. Comparisons of the model with experimental data from the actual roll simulator showed close agreement. The greatest difference was with motor pressure. The acceleration levels and roll motions for both the model and experimental data showed excellent correlation.
A Study on the Automatic Welding System for a Curved Block in Vertical Direction
Authors: Kim J. J. , Lee Y. S. , Goo Y. B.
Published: August 2012

Automated equipment is used for the ship fabrication process for higher productivity. However, in final assembly stage of ship structures, automatic welding system has the constraints for application because of inclination and curvature of the hull block. In order to solve these problems, an automatic welding system which has special mechanism to travel on the flexible rail has been studied. This paper describes the essential characteristics of the new automatic welding system equipped with the proper mechanism for flexible rail and continuously adjustable welding torch slider.
Creep Force Characteristics of Wheel/Rail Contact Under Friction Control
Authors: Yamashita Shunpei , Sakamaki Akihiko , Sugiyama Hiroyuki
Published: August 2012

In this investigation, a creep force model for contact with friction modifiers is developed and validated by comparing with the experimental results. To this end, a creep force model is developed by introducing a concept of equivalent shear modulus of rigidity, and a two-roller test rig is developed and used for validating the proposed model. Furthermore, relationships between the model parameters and the amount of friction modifiers applied to the contact patch are discussed. It is demonstrated that good agreements are obtained for the creep force characteristics obtained using the proposed model and the two-roller test rig developed in this investigation. Furthermore, it is shown that the proposed model can be used as a semi-empirical model, in which one can define the model parameter as a curve-fitting parameter and, at the same time, physical interpretations regarding the lubrication state between the wheel and rail interface can be obtained using the identified parameters.
Thermal Radiation in Silica Aerogel and its Composite Insulation Materials
Authors: Wei Gaosheng , Liu Yusong , Zhang Xinxin , Du Xiaoze
Published: August 2012

This paper engages in experimental measurements on thermal radiative transfer in silica aerogel and its composite insulation materials (xonotlite-aerogel composite and ceramic fibre-aerogel composite). The samples of silica aerogel, xonotlite-type calcium silicate, and ceramic fibre insulation materials are all considered as a semi-transparent medium capable of absorbing, emitting and scattering thermal radiation. The spectral transmittances are then measured at different infrared wavelengths ranging from 2.5 to 25μm with a Fourier transform infrared spectrometer (FTIR), and subsequently used to determine the specific spectral extinction coefficient and the specific Rossland mean extinction coefficient of the sample. The radiative conductivities deduced from the overall thermal conductivities measured with the transient hot-strip (THS) method are compared with the predictions from the diffusion approximation by using the measured spectral extinction coefficient. The results show that the spectral extinction coefficients of the samples are strongly dependent on the wavelength, particularly in the short wavelength regime (<10μm). The total Rossland mean extinction coefficients of the samples are all decreasing with the temperature increasing. The radiative conductivities are found almost proportional to the cubic temperature, and decreases as the sample density increases.
Minimization of the Amplitude of the Entire Span of Beams Using Mass Dampers
Authors: Issa Jimmy S.
Published: August 2012

The aim of this work is the reduction of the steady state amplitude of harmonically forced simply supported beams using mass dampers. The considered system consists of a mass damper attached to a simply supported beam with a harmonic force applied at a given point along its span. Traditionally, passive vibration devices such as mass spring dampers or mass dampers were attached to beams and carefully designed to minimize the maximum amplitude at a given point along their span. Since minimizing the amplitude at one point of the beam might increase it at another point, in this work the maximum amplitude along the entire beam span is minimized. The problem is solved first using an approximate method. For a given mass ratio, the optimal location of the mass damper is determined first, and then the optimal damping constant is calculated. Fixed-lines of the amplitude of the entire span of the beam which are independent of the damping constant are determined. The optimal placement of the mass damper is chosen such that the maximum of these lines is minimized. Then, the optimal damping constant is obtained analytically from an average of two damping ratios corresponding each to one of the peaks of the amplitude of the entire beam span to coincide with one of the two equally leveled maxima of the fixed-lines. The optimal placement and damping constant are calculated for all possible positions of the point force on the beam. These results are compared to those obtained from an exact numerical optimization procedure. The results are written in dimensionless form and can be applied to a system with any material and geometric properties.
TrenSen: A New Way to Study the Unsteady Behaviour of Air Inside Tunnels—Application to High Speed Railway Lines
Authors: Ferna´ndez Manuel Rodri´guez , Torres Evangelino Garrido , Garci´a Ricardo Ortega
Published: August 2012

During the last decades, high speed railway traffic system has achieved a great development all over the world. Increasing speed in the train circulation implies the apparition of new aerodynamic phenomena that need to be studied. One of these problems has to do with the entrance and exit of high speed (HS) trains in tunnels. When this occurs, pressure waves propagate and reflect through the tunnel at sound speed, generating a non-stationary movement of the air which depends greatly on the speed of the train and the geometry between train and tunnel. A study has been carried on to determine the pressure and velocity fields of air inside the tunnel when the train passes through. As a result of this study, a new software, “TrenSen”, has been developed. This program solves numerically a particular case of the Navier-Stokes equations, a hyperbolic system of partial differential equations which describe the flow behaviour inside the tunnel. In the first section of the paper presented hereby a description of the algebra for the fluid dynamics equations is conducted. The second section will explain some features of the software, ending with some numerical results obtained from the program. To finish the paper, the software is validated by comparing the numeric results with available experimental data and with some other commercial software.
Dimensional Analysis for Bus Dynamic Performance Evaluation
Authors: Gauchi´a A. , Olmeda E. , Boada M. J. L. , Boada B. L. , Di´az V.
Published: August 2012

Current bus regulations, as R66, and engineering bus design require testing of bus structures prototypes in order to guarantee a certain level of strength and an appropriate dynamic behavior of the bus superstructure. Experimental testing of this type of vehicles requires of big installations and space, as well as specific sensors and, therefore, can be very expensive. However, if the experimental testing is done in a scale model the infrastructure and costs would be lower than using a real bus structure prototype. Therefore, a methodology, to evaluate the bus structure dynamic performance by means of dimensional analysis and scale modeling is proposed.
Support-Condition Analyses of Rotating Beams Under Distributed Imbalance Loading
Authors: Jokinen Kai , Keskinen Erno , Jorkama Marko , Seemann Wolfgang
Published: August 2012

In roll balancing the behaviour of the roll can be studied either experimentally with trial weights or, if the roll dimensions are known, analytically by forming a model of the roll to solve response to imbalance. Essential focus in roll balancing is to find the correct amount and placing for the balancing mass or masses. If this selection is done analytically the roll model used in calculations has significant effect to the balancing result. In this paper three different analytic methods are compared. In first method the mode shapes of the roll are defined piece wisely. The roll is divided in to five parts having different cross sections, two shafts, two roll ends and a shell tube of the roll. Two boundary conditions are found for both supports of the roll and four combining equations are written to the interfaces of different roll parts. Totally 20 equations are established to solve the natural frequencies and to form the mode shapes of the non-uniform roll. In second model the flexibility of shafts and the stiffness of the roll ends are added to the support stiffness as serial springs and the roll is modelled as a one flexibly supported beam having constant cross section. Finally the responses to imbalance of previous models are compared to finite element model using beam elements. Benefits and limitations of each three model are then discussed.
Performance Analysis of a Vacuum Desalination System
Authors: Saad M. , Ahmed M. , Morcos V. M.
Published: August 2012

A new desalination system has been proposed and designed for converting sea water into fresh water utilizing the waste heat of internal combustion engines. The desalination process is based on the evaporation of sea water under a very low pressure (vacuum). The low pressure is achieved by using the suction side of a compressor rather than a commonly used vacuum pump. The evaporated water is then condensed to obtain fresh water. The effects of operational variables such as evaporator temperature, condenser temperature, vacuum pressure, and flow rate of both evaporator and condenser on the yield of fresh water are experimentally investigated. It is found that decreasing the vacuum pressure causes a significant increase in the yield of fresh water. It is also found that decreasing the condenser temperature, or increasing the evaporator temperature both lead to an increase in the yield of fresh water. Moreover, increasing the condenser flow rate tends to increase the yield of fresh water. The same trend is attained by increasing the evaporator flow rate.
Finite Volume Method for Simulation of Creep in RF MEMS Devices
Authors: Das Shankhadeep , Koslowski Marisol , Mathur Sanjay R. , Murthy Jayathi Y.
Published: August 2012

Radio-frequency microelectromechanical systems (RF MEMS) are widely used in contact actuators and capacitative switches. In these devices, the membrane deforms under electrostatic actuation. With time, these devices undergo creep deformation that reduces the gap between the metallic membrane and the electrodes, and can result in self pull-in at lower applied voltages than for normal pull-in. It is important to accurately model creep in RF MEMS devices to understand their long-term behavior and to improve their reliability. In this paper, we extend a cell-centered finite volume approach previously developed to describe linear elastic solids to model visco-plastic and creep phenomena. The finite volume discretization produces a set of algebraic equations, which is solved using a biconjugate gradient stabilized (BCGSTAB) solver. Test cases are first presented verifying the accuracy of the method. Results are then presented in this paper for the long-term creep behavior of a fixed-fixed MEMS device.
Cryogenic Temperature Stabilization of the Daikin 308 Cryocooler
Authors: Smith Michael J. , Jennings Jeff
Published: August 2012

We report on a scheme developed at the Harvard-Smithsonian Center for Astrophysics to stabilize longer term cryogenic temperature variations in equipment used for high frequency radio telescope receivers. Cryogenic temperature variations of the 30 minute time scale are reduced an average of 55 percent by controlling the helium pressure flowing through the cryostat. Applications in the field of cryogenic radio astronomy will benefit from this resulting reduction of power fluctuations and corresponding reductions in observation time on source. An Equilibar® back pressure regulator was used to allow helium from the compressor to bypass the cryostat, thereby providing a very stable pressure control system. Manually set reference port pressure regulates the helium bypass and deviates less than 6.2 × 10^−4 MPa for the 30 minute time period while power output deviations of the heterodyne receiver are reduced as a result of the increase in pressure stability an average of 46%.
Large Eddy Simulation of the Flow Around a Diffuser-Equipped Bluff Body in Ground Effect
Authors: Puglisevich Lara Schembri , Page Gary
Published: August 2012

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers (1.01 × 106 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.
Cost Reduction Strategies for an Oxy-Fuel Power Plant With CO2 Capture: Application of an Advanced Exergoeconomic Analysis to an Advanced Zero Emission Plant
Authors: Petrakopoulou F. , Tsatsaronis G. , Morosuk T.
Published: August 2012

Although conventional exergy-based analyses uncover a path towards plant improvement, they suffer from some limitations, which are addressed by advanced exergy-based analyses. Advanced exergy-based methods identify interdependencies among plant components, and reveal the potential of improvement both at the component and plant level. Thus, data obtained from these methods pinpoint strengths and weaknesses of energy conversion systems and are of great importance when complex plants with a large number of interconnected components are considered. In this paper an advanced exergoeconomic analysis is applied to an advanced zero emission plant (AZEP). The most important components, in terms of the total avoidable costs, are the components constituting the main gas turbine system, while of particular importance are also the components of the mixed conducting membrane reactor incorporated in the plant. It has been found that for the most influential components of the plant, the largest part of investment cost rates and costs of exergy destruction are unavoidable. Additionally, for both the investment cost and the cost of exergy destruction, the interactions among the components are in most cases of lower importance, since for the majority of the components, the endogenous parts of the costs (related to the operation of the components themselves) are significantly larger than the corresponding exogenous parts (related to the operation of the remaining components). Nevertheless, strong interactions have been found among the components of the mixed conducting membrane reactor.
Handling and Primary Ride Comfort Development in Early Design Stage by Means of 1D Modeling Approach and Multi Attribute Optimization Process
Authors: Alneri Stefano , di Carlo Paolo , Toso Alessandro , Donders Stijn
Published: August 2012

Today the automotive market is ever more competitive and vehicles must satisfy the requirements of the customers in all respects: handling, comfort, acoustics, fuel economy, etc. Therefore OEMs have to launch innovative products in a short development timeline: the time to market (TTM) of new vehicles has continually decreased and nowadays the developing process of a new car is completed in less years than in the past. This scenario emphasizes the role of CAE in the vehicle design engineering design and the necessity of exploiting its potentialities, in order to shorten the TTM and to reduce the impact of experimental tests on it. In this context a step-by-step approach with multi-physics 1D environment such as LMS Imagine. Lab AMESim is proposed in order to monitor vehicle performances in all the design stages, thanks to the employment of models with increasing complexity. In addition the ultimate step can be employed for performing a multi attribute optimization on vehicle performance metrics in order to find the best attributes balancing and to pass the preliminary recommendations to the design with a considerable time-saving respect to 3D MBS models. This paper briefly describes the process for building 1D models with LMS Imagine.Lab AMESim and moreover it shows the definition of a multi attribute optimization algorithm in terms of handling performances with the most complex model.
Multibody System Modeling of Flexible Twist Beam Axles in Car Suspension Systems
Authors: Sinokrot Tariq Z. , Prescott William C. , Nembrini Maurizio , Toso Alessandro
Published: August 2012

Dynamic simulation techniques that are based on Multibody system approaches have become an important topic in studying the performance of various mechanical components that comprise an automotive system. One of the challenging issues in such studies is the ability to properly account for the flexibility of certain parts in the system. One example where this is important is the design of twist beam axles in car suspension systems where twisting deformations are present. These deformations are geometrically nonlinear and require a special handling. In this paper two multibody system approaches that are commonly used in overcoming such problem are examined. The first method is a sub-structuring technique that is based on the popular method of component mode synthesis. This method is based on dividing the flexible component into sub-structures, in which, the linear elastic structural theory is sufficient to describe the deformation of each sub-structure. Using this method the deformation of the beam is described using the mode shapes of vibration of each sub-structure. The equations of motion, in this case, are written in terms of the system’s generalized coordinates and modal participation factors. In the second method a Multibody System (MBS) solver and an external nonlinear Finite Element Analysis (FEA) solver are coupled together in a co-simulation manner. The nonlinear FEA solver, in this case, is used in modeling the deformation of the twist beam. The forces due to the nonlinear deformations of the flexible beam are communicated to the MBS solver at certain attachment points where the flexible body is attached to the rest of the multibody system. The displacements and velocities of these attachment points are calculated by the MBS solver and are communicated back to the nonlinear FEA solver to advance the simulation. The two methods described above will be reviewed in this paper and an example of a twist beam axle in a car suspension system model will be examined twice, once using the sub-structuring method, and once using the co-simulation method. The numerical results obtained using both methods will be analyzed and compared.
Advanced Exergoeconomic Analysis of a Refrigeration Machine: Part 1—Methodology and First Evaluation
Authors: Morosuk T. , Tsatsaronis G.
Published: August 2012

An exergoeconomic analysis identifies the location, magnitude and sources of thermodynamic inefficiencies and costs in an energy conversion system. This information is used for improving the thermodynamic and the economic performance and for comparing various systems. A conventional exergy-based analysis does not consider the interactions among the components of a system nor the real potential for improving the system. These shortcomings can be addressed and the quality of the conclusions obtained from an exergoeconomic evaluation is improved, when for each important system component the values of exergy destruction and costs are split into endogenous/exogenous and avoidable/unavoidable parts. We call the analyses resulting from such splittings advanced exergy-based analyses. The paper demonstrates how an advanced exergoeconomic analysis provides the user with information on the formation processes of thermodynamic inefficiencies and costs and with suggestions for their minimization. In the first part of the paper, the advanced exergy-based analyses are applied to an air refrigeration machine. In the second part of the paper, we demonstrate that the information obtained in the first part can be used to modify the values of the decision variables to reduce the cost of the final product (cold) of the overall system.
Influence of the Flow From an Axial Fan on the Performance of a Heat Exchanger
Authors: Moore James , Grimes Ronan , Walsh Ed
Published: August 2012

Limited water supplies in arid regions that have abundant solar resources eliminates the use of water as a feasible means of cooling condensers in a Concentrated Solar Power (CSP) plant condenser. This has triggered the need to optimise existing air-cooled condenser technology, which is currently extremely inefficient. This paper aims to investigate the influence of various fan parameters on the performance of a cross-flow heat exchanger. The study first focuses on the effect of varying the distance between the fan and the heat exchanger in order to establish if uniform airflow distributions can be achieved with acceptable axial spacing between the fan and the heat exchanger. This was achieved by mapping the velocity field at the outlet from the heat exchanger by means of a Particle Image Velocimetry (PIV) analysis. The analysis was carried out for two air flow scenarios; the fan mounted at the inlet to the heat exchanger (forced draught) and the fan mounted at the outlet of the heat exchanger (induced draught). An investigation into the effect of fan speed on velocity distribution was also carried out. The measurements which are presented show that uniform velocity distributions can be achieved with relatively small fan to heat exchanger spacing for the case of the induced draught, whilst for the forced draft, although increasing the fan to heat exchanger spacing resulted in increased flow uniformity, the flow was still highly non uniform at fan to heat exchanger spacing of up to 1.4 times the fan tip radius. The measurements also showed little effect of fan speed on normalised velocity distribution. Combining the fore mentioned measurements with an analytical calculation technique, the heat flux per unit area across the heat exchanger was calculated. The results highlight the limitations on heat transfer in various regions of the heat exchanger in both flow scenarios. These measurements and calculations will facilitate designers of air cooled heat exchangers in achieving the minimum fan to heat exchanger spacing which gives no further increase in total heat transfer.
Numerical Analysis on Nanofluid Forced Convection in Ducts With Triangular Cross Sections
Authors: Manca O. , Nardini S. , Ricci D. , Tamburrino S.
Published: August 2012

Heat transfer of fluids is very important to many industrial heating or cooling equipments. Convective heat transfer can be enhanced passively by changing flow geometry, boundary conditions or by enhancing the thermal conductivity of the working fluids. An innovative way of improving the fluid thermal conductivity is to introduce suspended small solid nanoparticles in the base fluids. In this paper a numerical investigation on laminar forced convection flow of a water–Al2O3 nanofluid in a duct having an equilateral triangular cross section is performed. The hydraulic diameter is set equal to 1.0×10−2 m. A constant and uniform heat flux on the external surfaces has been applied and the single-phase model approach has been employed. The analysis has been run in steady state regime for a nanoparticle size equal to 38 nm, considering different volume particle concentrations. The CFD code Fluent has been employed in order to solve the tri-dimensional numerical model. Results are presented in terms of temperature and velocity distributions, surface shear stress and heat transfer convective coefficient, Nusselt number and required pumping power profiles. Comparison with results related to the fluid dynamic and thermal behaviors in pure water are carried out in order to evaluate the enhancement due to the presence of nanoparticles in terms of volumetric concentration.
Uncertainty Enabled Design of an Acceleration Switch
Authors: Brake M. R. , Massad J. E. , Smith R. C. , Beheshti B. , Chowdhary K. , Davis J. , Wang S.
Published: August 2012

A mechanical acceleration switch has been developed to synchronize instrumentation during a destructive acceleration test. The tests are of short durations and involve very high velocities and accelerations, and a destructive impact. Therefore, accurately synchronized instrumentation is critical. When the switch detects a desired acceleration time history, the switch closes to complete a circuit for instrument activation. Preliminary tests on the proposed switch have shown that switch-to-switch variations exist due to fabrication and assembly tolerances, and that combinations of variations may lead to a switch that does not respond properly. If the switch does not close at the proper time, improper data may be collected; or, at worst, no data may be collected before destructive impact. In this paper, a nonlinear model of the switch closing dynamics is developed in order to investigate the effect of uncertainty on its operation. In particular, the propagation of uncertainty from the switch parameters to the switch dynamics is quantified, and then the design is optimized such that the operation of the switch is insensitive to the variation and uncertainty. The results of the analysis elucidate the parameters that significantly impact switch operation, quantify the reliability of the existing switch design, and ultimately are used to recommend a design that could significantly improve reliability.
CFD Analysis of Drug Carrying Magnetic Nanocomposite Carriers Under Magnetic Fields
Authors: Wamocha H. L. , Tandel R. , Lankarani H. , Asmatulu R.
Published: August 2012

Recently, magnetic targeted drug delivery has been focused on the efficiency of magnetic nanoparticles (MNP) encapsulated in polymeric materials and drug molecules. The MNP can be introduced into the blood stream intravenously and be guided to the target site by the use of a magnetic field. The ability of the therapeutic agents to access the target site effectively depends on physicochemical properties of the drug loaded MNP, field strength and geometry, depth of the target tissue, rate of blood flow and vascular supply. A computational fluid dynamics (CFD) approach is utilized in this study to understand the fluid flow mechanism of MNP introduced in the blood vessel in the presence of a magnetic field. The effect of magnetic capture on the flow characteristics of the blood was investigated. CFD technique may offer insight into the mechanism of time-varying fluid flow in human arteries. This knowledge can be harnessed to improve magnetic capture and drug efficiency. The focus of this study is on how the size of the blood vessels, the strength of the magnetic field, and the velocity of the fluid within the vessels affect the delivery of the therapeutic agents. The results would be useful for the biomedical and pharmaceutical industries.
Influences of Nitrogen Dilution in the Near Flow Field of Transition Regime Lifted Natural Gas Jet Flames
Authors: Hasan Tamir S. , Kribs James S. , Lyons Kevin M.
Published: August 2012

Flame liftoff height data were obtained on lifted methane jet flames diluted with nitrogen at transition regime Reynolds numbers. The data were analyzed to better understand and model natural gas combustion phenomena, in particular the effects of dilution in the near transition regime of methane jet flames. Images of the stable lifted flames were obtained at low Reynolds numbers from 2000 to 3800. This regime of Reynolds numbers was chosen due to the instability of laminar, lifted methane flames at these lower Reynolds numbers. Amongst other applications, lifted flames are often utilized in boilers and industrial burners to reduce thermal stresses, and are thus of importance in natural gas and low calorific fuel gas combustion. Radial and axial locations of the lowest flammable regions were observed. Since definitive models depicting lifted flames in the transition regime between laminar and turbulent flows have not yet been developed, the data was compared to the approximations of a turbulent flame model. The mass fraction model proposed by Tieszen et al (1996), which approximates the flammable regions based on mass fraction of fuel, was utilized in the analysis. For the conditions examined, turbulent lifted methane flames exist between mass fractions of 0.05 and 0.15. Applying this model showed that experimental results occurred outside of the leanest combustion zone predicted. At low Reynolds numbers, the model’s limit for radial location was the most pronounced factor which distinguished the predicted and observed values. These findings could be a result of the instabilities in the transition regime that result from lower stream velocities, such as unsteady vortical structures or small radial variance. It may also be a result of the data occurring at the lower limit of the model’s applicable regime. Some examination of the data also shows a correlation between mass flow rate of the diluent and the deviation of the experimental data from the theoretical data. Further investigations will continue to observe the effects of dilution into higher Reynolds number jet flames under dilution and co-flow, since they are important in understanding fundamental behavior seen in syngas and low calorific gas combustion.
Experimental Study of Effects of Interfacial Properties on Nucleate Pool Boiling in Water
Authors: Verma U. , Manglik R. M. , Jog M. A.
Published: August 2012

Saturated, nucleate pool boiling on a horizontal, cylindrical heater in aqueous solutions of a fluorosurfactant (FS-50) is experimentally investigated. FS-50 is a long chain molecule of fluorinated carbon atoms, and it produces very low dynamic surface tension (varying from 72.5 mN/m to 17.4 mN/m with surface age and concentration) in aqueous solutions. Boiling curves (given by the variation of heat flux with wall superheat) and photographic records of the ebullient behavior are presented, along with a detailed characterization of the interfacial tension of the solutions. It is seen that nucleate pool boiling behavior of water is significantly altered by the addition of FS-50, and the heat transfer is increased. The enhancement in boiling is seen to stem from the substantial changes in the interfacial properties. A rather complex interplay of dynamic interfacial tension and surface wetting due to varying surfactant concentrations is seen to affect the phase change ebullient dynamics and associated heat transfer.
Investigation for Toroidal Microfluidic Vortices Generated by a Laser Illumination Application in an Uniform Electric Field
Authors: Kwon Jae-Sung , Wereley Steven T.
Published: August 2012

Using micro particle image velocimetry (μPIV) [1], we visualize and analyze strong toroidal microfluidic vortices generated when a near-infrared (1064 nm) laser beam and an alternating current (AC) electric field is simultaneously applied to a chip. The vortices exhibit a source type behavior in the plane normal to the electric field and the flow vorticity is characterized as a function of the electric field potential, electrical AC frequency and laser power. At a constant AC frequency of 9 kHz, the flow vorticity increase as the square of the electric field strength. At constant electric field, the flow vorticity does not change appreciably in 10–100 kHz range and it decreases at larger frequencies (>500 kHz) until when Brownian motion dominates the movement of the 3μm tracer particles. At constant electrical frequency and voltage of 9 kHz and 20Vpp, the flow vorticity remarkably increases as the laser power increases from 20 to 100mW, due to the rapid change of the temperature gradient inside a fluid and its coupling effect with the applied electric field.
Graphene Based Nafion® Nanocomposite Membranes for Proton Exchange Membrane Fuel Cells
Authors: Adigoppula Vinay K. , Khan Waseem , Anwar Rajib , Argun Avni A. , Asmatulu R.
Published: August 2012

Nanocomposite proton-exchange membranes are fabricated by loading graphene nanoflakes into perfluoro sulfonic acid polymer (Nafion) solutions at controlled amounts (1–4 wt%) followed by electrical and thermal characterization of the resulting membranes. Electronic and ionic conductivity values of the nanocomposites, as well as their dielectric and thermal properties improve at increased graphene loadings. Owing to graphene’s exceptionally high surface area to volume ratio and excellent physical properties, these nanocomposite are promising candidates for proton-exchange membrane fuel cell applications.
Effects of Hydrophobic Barrier Films on the Mechanical Properties of Fiber Reinforced Composites Immersed in Water
Authors: Kececi E. , Asmatulu R.
Published: August 2012

Fiber reinforced composites are subjected to a wide range of mechanical loads and environmental conditions, such as wind, high/low temperature, moisture, UV light and aggressive solvents. Compared to other structural materials, polymers can absorb more moisture and UV light from outside environment and lose their material properties (e.g., mechanical, electrical, surface and thermal) and thus the service life. In this study, hydrophobic barrier films including polyvinylfluoride (PVF) and polyether ether ketone (PEEK) were applied on the carbon, Kevlar, and glass fiber reinforced epoxy resin composites (laminate and sandwich structures), and then the effects of moisture absorption on those films were investigated in detail. The coupons were immersed in water for a number of days in order to determine the changes in mechanical properties of the composites. Three point bending tests were applied to the laminate composites, while four point bending tests were conducted on the Nomex sandwich structured composites. We found that moisture absorption could be eliminated by using these hydrophobic films. We found that PEEK film could be an alternative barrier film for the aircraft industry.
Evaluation of Advanced Composites Using Destructive Testing Techniques
Authors: Asmatulu R. , Movva V.
Published: August 2012

A very basic problem in manufacturing advanced composites is the occurrence of defects, such as voids, delamination, resin rich areas, distorted fibers and foreign material inclusions. Of these defects, voids are the unavoidable defects mostly coming from a variety of reasons, including resin type, poor vacuum source, air entrapment, leakage of vacuum bag and by-products formed during the curing cycle of laminates. These voids seriously affect the mechanical properties of composite panels, and cause severe damages during the service. In the present study, various destructive testing techniques, such as visual, burn-out or ignition loss of cured composites, image analysis and matrix digestion or acid digestive were used on advanced composite panels at various porosity levels (e.g., 0–2%, 3–6% and greater than 7%), and the obtained results were compared each other. Also, testing parameters were optimized using the standard samples to achieve maximum possible error free data of voids, fiber volume, fiber wash, inter laminar and trans laminar cracks, miss-oriented fibers, lay-up orders and latent defects. Optimization of parameters was performed using the design of experiments. We determined that the test results were significantly changed based on the test techniques, composite samples, as well as testing time, operator skill, cost of experimentation, initial equipment cost, pre and post treatments and lack of standardized testing patterns.
Evaluating Performance of Composite Materials for MHK Applications
Authors: Miller David A. , Mandell John F. , Samborsky Daniel D.
Published: August 2012

Montana State University (MSU) has a compilation of material systems, environmental chambers, and mechanical testing equipment to determine composite materials performance and failure characteristics. Mechanical characterization of composite systems will provide direct quantification of the materials under consideration for Marine Hydro Kinetic (MHK) designs that were initially developed for the wind turbine industry. The work presented herein represents the testing protocol development and initial results to support investigations on the effect of sea water absorption on material strength. A testing protocol for environmental effects has been developed for the resin infused in-house fabricated laminates. Unidirectional ([0] and [90]) test samples of 2-mm and 6-mm thickness were be submerged for 1000 hours in synthetic sea water at 40°C with the weight recorded at time intervals over the entire period. After 1000 hours of conditioning, coupons were placed in the synthetic sea water at 20°C until testing. Static compressive and tensile strength properties at temperatures of 5°C, 20°C and 40°C were collected. These initial results show trends of reduced tensile and compressive strength with increasing moisture and temperature in the 0° (longitudinal) direction. In the 90° (transverse) direction, compression strength decreases but tensile strength is little affected as temperature and moisture increase. Elastic modulus (E) is little affected in the longitudinal direction but decreases in the transverse direction.
Characterisation of Air-Water Two-Phase Flow Using a Wire-Mesh Sensor
Authors: do Amaral Carlos E. F. , Scorsim O´liver B. S. , Santos Eduardo N. , da Silva Marco Jose´ , Conte Marco Germano , Morales Rigoberto E. M.
Published: August 2012

Two phase flow occurs in many industrial applications, mainly in the transport of mixtures. Many patterns can be produced according to the liquid and gas flow rates. The identification of these patterns is very important in the design of piping systems and equipments. This work proposes an experimental study to identify multiphase flow patterns of water and air in horizontal pipes. The study was developed using an experimental circuit of 26 mm diameter and 9.2 m length pipe, at Thermal Sciences Lab (LACIT) at the Federal University of Technology - Parana´. To characterize the flow patterns, an intrusive mesh electrodes sensor was used, which allows the detailed visualization of the phases distribution. Tests were made using several experimental settings of water and gas flow rates. Measurements were compared to images obtained by high speed camera and the temporal void fraction series which were analyzed with the use of PDF and PSD functions, showing the singularities for each two-phase flow pattern.
Analysis of the Hazards of Wood Chipper Accidents
Authors: Heist Ashley M. , Ziernicki Richard M. , Railsback Ben T.
Published: August 2012

It is well known in the tree care industry that operators can become caught or snagged by material entering a wood chipper. The consequences can be devastating. On commercial wood chippers with mechanical infeed systems, a caught operator can be pulled into the machine by the infeed system. Due to the speed of the infeed system, once an operator has been caught there is a limited window of time before serious injury or death can occur. Commercial wood chippers commonly pull in branches at speeds of 20 inches per second (50.8 centimeters per second) or faster. Therefore, caught operators may have no more than a few seconds to either free themselves from the branches or activate a device to stop the feeding mechanism. As an operator is being pulled into the chipper toward the chipping mechanism, various factors can limit the caught operator’s ability to access or activate a feed-stop device. Consequently, operators are sometimes unable to save themselves from catastrophic injury or death. This paper analyzes the hazards associated with wood chipper accidents and assesses the effectiveness of various safety devices intended to protect operators from this danger. The investigation includes a historical review of wood chipper safety devices and ultimately reveals the importance and effectiveness of feed-stop devices that can be passively activated by an operator who has become caught. The paper addresses commercial wood chippers with mechanical infeed systems.
Parametric Design Optimization of Uncertain Ordinary Differential Equation Systems
Authors: Hays Joe , Sandu Adrian , Sandu Corina , Hong Dennis
Published: August 2012

This work presents a novel optimal design framework that treats uncertain dynamical systems described by ordinary differential equations. Uncertainty in multibody dynamical systems comes from various sources, such as: system parameters, initial conditions, sensor and actuator noise, and external forcing. The inclusion of uncertainty in design is of paramount practical importance because all real-life systems are affected by it. Designs that ignore uncertainty often lead to poor robustness and suboptimal performance. In this work uncertainties are modeled using Generalized Polynomial Chaos and are solved quantitatively using a least-square collocation method. The uncertainty statistics are explicitly included in the optimization process. Systems that are nonlinear, have active constraints, or opposing design objectives are shown to benefit from the new framework. Specifically, using a constraint-based multi-objective formulation, the direct treatment of uncertainties during the optimization process is shown to shift, or off-set, the resulting Pareto optimal trade-off curve. A nonlinear vehicle suspension design problem, subject to parametric uncertainty, illustrates the capability of the new framework to produce an optimal design that accounts for the entire family of systems within the associated probability space.
Design, Fabrication of High-Throughput Microarray Microfluidic Device for Membrane Protein Polyhedra Formation
Authors: Wu Hsin-Jui , Yan Yiwei , Lee Y. C. , Stowell Michael
Published: August 2012

In this paper, we designed and fabricated High-throughput Microfluidic device for membrane protein polyhedral. Protein is the most important functional element in our human body and also it could be applied to the key application areas of drug bonding and drug delivery. However protein stucture is difficult to be analyzed due to the complex and variable geometry of protein stucture which can be randomly formed by 20 amino acids and also plused 3D folding of stucture possibly. Based on this, we could imagine it would be a huge variable number of protein stucture, let’s say billion possibilities. Therefore if we can successful discover protein stucture, then we can expect that will improve drug delivery of medical technology forward to a big step.
Robust Nanoscale Patterns for Thin Film Solar Cells Using Inverse Optimization of Nonuniformly Sampled Absorption Spectrum
Authors: Hajimirza Shima , Howell John R.
Published: August 2012

This paper outlines several techniques for systematic and efficient optimization as well as sensitivity assessment to fabrication tolerances of surface texturing patterns in thin film amorphous silicon (a-Si) solar cells. The aim is to achieve maximum absorption enhancement. We report the joint optimization of several geometrical parameters of a three dimensional lattice of periodic square silver nanoparticles, and an absorbing thin layer of a-Si, using constraint optimization tools and numerical FDTD simulations. Global and local optimization methods, such as the Broyden–Fletcher–Goldfarb–Shanno Quasi-Newton (BFGS-QN) and Simulated Annealing (SA) are employed concurrently for solving the inverse near field radiation problem. The design of the silver patterned solar panel is optimized to yield maximum average enhancement in photon absorption over the solar spectrum. The optimization techniques are expedited and improved by using a novel nonuniform adaptive spectral sampling technique. Furthermore, the sensitivity of the optimally designed parameters of the solar structure is analyzed by postulating a probabilistic model for the errors introduced in the fabrication process. Monte Carlo (MC) simulations and Unscented Transform (UT) techniques are used for this purpose.
Effect of a Symmetric Contraction on the Concentration Profiles of a Particle-Laden Slurry
Authors: Deshpande A. , Ramisetty K. , Chambers F. W. , McNally M. E. , Hoffman R. M.
Published: August 2012

In-line measurements and sample stream withdrawals for on-line and/or at-line measurements of slurries flowing in horizontal pipes can be complicated by nonuniform slurry profiles. More uniform profiles would improve measurements. Area contractions are a common means used to produce more uniform velocity fields for single phase flows. For example, contractions are used to condition the flow entering wind tunnel test sections and make velocity profiles more uniform at venturi throats. It was desired to determine whether area contractions could be used to make slurry concentration profiles more uniform in horizontal pipe flows. An ASME flow nozzle with a contraction diameter ratio of 0.5 was chosen as a well defined geometry to consider in a Computational Fluid Dynamic (CFD) study of the effects of a contraction on slurry concentration profiles. The pipe was 2.8 m long with a 50.8 mm diameter. The entrance of the contraction was placed at 35 pipe diameters from the inlet in fully developed flow. A length of 20 diameters followed the contraction. The slurry had a xylene liquid phase and an ADP solid phase with a density ratio of 1.7. The simulations were performed at primary phase velocities of 2 m/s and 4 m/s, corresponding to Reynolds numbers of 1.4E05 and 2.8E05. Spherical particle diameters of 38, 75, and 150 μm were used at concentrations of 0.05, 0.2, and 0.3. ANSYS FLUENT 12 software was used with the standard k-ε turbulence model and standard wall function. The mixture multi-phase model was used for the two-phase flow. An unstructured tetrahedral meshing scheme was used with 1.4 million elements. The grid was adjusted until the condition 30 < y+ <60 for the mesh point nearest the wall was satisfied. A grid refinement study was performed to insure grid independence. The computational scheme first was validated by comparing pipe flow velocity and concentration profiles to results in the literature. The computations performed with the contraction showed that in all cases the concentration profiles of the solid particles displayed greater uniformity than the profiles in the pipe upstream of the contraction. The effect of the contraction was more pronounced for the larger particles. As in the case of single phase flows, the contraction caused the axial turbulence intensity to decrease. The greater uniformity of the concentration profiles at the exit plane of the nozzle, suggest that the contraction can provide better conditions for performing measurements of a particle-laden slurry.