bluuebunny/crossref_metadata_2025 huggingface dataset:
Sizing Solar Energy Components for Level-Crossing Facilities
Authors: Sanz Bobi Juan de Dios , Reyes de la Pen˜a Pedro , Hidalgo Fiestas Jose Carlos , Garci´a de los A´ngeles Alberto , Loiero Roberto
Published: August 2009

Currently, there are a large number of level crossings on railway lines. These signaling facilities are necessary from the point of view of railway lines and also from the traffic of vehicles and people crossing them. This signaling system is built on a number of elements such as acoustic and lighting signals—barriers that prevent cars & pedestrians from accessing rail tracks. These level crossing facilities operate autonomously and they are not part of the security facilities (interlockings) when planning or building stages. Therefore, a major constraint for level crossings is the lack of a feasible electric supply primarily because of the high cost of cable running due to the great difficulty of transporting this energy to some areas. This high cost will make installation unprofitable where there is light traffic in trains and/or pedestrians and vehicles. This paper proposes that a solar photovoltaic supply system would make installation cost efficient instead of cable running. The research shows that the sizing method for this power supply and the measuring tool detailed below ease calculations. This proposed system provides both economical and environmental benefits. These benefits positively impact those areas where traditional cable supply is difficult to provide. In order to size the electrical feeding system for these level crossings facilities two calculations are necessary: 1) the calculation of the daily incident solar irradiation into a horizontal surface and, 2) the location where the facility is going to be set. The calculation of the theoretical energy consumption is determined by the integral of the instantaneous electrical power consumption of the system. Thus, the proposed solution in the paper provides a cost reduction to deploy level crossing facilities crossing existing railway lines. It allows the installation of level crossings with increased security features necessary for the correct signaling from the basic level crossing to configurations such as acoustic and light signals, or even protective barriers. These elements provide more information and safety to cars and pedestrians concerning train crossing, decreasing the risk of accidents. Additionally, this power supply system can be deployed easily and can be adapted to any topology minimizing costs. Furthermore these systems are environmentally friendly as they clear away the impact of the electrical consumption of the facility from the network and do not need cable running in order to transport this energy to the level crossing facility.
Optimization of Steel Monopod Offshore-Towers Under Probabilistic Constraints
Authors: Karadeniz H. , Togan V. , Vrouwenvelder T.
Published: August 2009

In this work, economical design implementation of a circular steel monopod-offshore-tower, which is subjected to the extreme wave loading, is presented. The mass of the tower is considered as the objective function. The thickness and radius of the cross-section of the tower are adopted as design variables of the optimization. Moreover, stress or buckling is specified as probabilistic constraints. The numerical strategy employed for performing the optimization uses the IMSL-Libraries routine that is based on the Sequential Quadratic Programming (SQP). The FORM is used for the reliability calculation from a specified limit state function based on the stress or buckling. A demonstration of an example monopod tower is presented.
Numerical Study of Heat and Mass Transfer by Laminar and Turbulent Natural Convection With Cross Diffusion Effects in Square Cavity
Authors: Geng Wenguang , Chen Baoming , Tian Maocheng , Liu Fang
Published: August 2009

Laminar and turbulent natural convection flow in a two-dimensional square cavity filled two component system with compensating horizontal thermal and solute concentration gradients is investigated in this paper. The temperature gradient and volatile organic compounds (VOCs) concentration gradient are kept uniform in horizontal direction, while horizontal surfaces are kept adiabatic and impermeable within a square cavity. According to the principle of irreversible thermodynamics, with thermal-diffusion (Soret) effect and diffusion-thermo (Dufour) effect, a commercial computational fluid dynamics (Fluent) code is used to simulate heat and mass transfer numerically in present work. After validation of the method with available measurements, the range of the cross diffusion coefficients are analyzed firstly. Furthermore, the thermal field and solute concentration fields are presented for various conditions. Finally, the average Nusselt number and Sherwood number at the vertical wall are presented graphically. The numerical results show that the present work would help to know about the convective diffusion and distribution of VOCs indoor environment accurately. Also, it gives the more accurate characteristics of heat and mass transfer in multi-component system with cross diffusion effects.
Shear Stress Measurement in Microfluidic Systems: Liquid Crystal Technique
Authors: Martel Joseph , Bruno Bradford A.
Published: August 2009

Preliminary work towards developing a liquid crystal based technique for direct shear stress measurements over solid surfaces in microfluidic systems is presented. The microfluidic slug flow study which motivated the development of this technique is presented, as is general background on microfluidics. The theory of shear sensitive liquid crystals is reviewed and then expanded upon in regards to the specific type of flow considered in this study; slug flow. A prototype apparatus is described which is capable of generating slugs, and has appropriate optical access to test the liquid crystal shear stress measurement technique. The microchannel (150μm × 250μm laser etched glass), auxiliary flow (Cole-Parmer Infusion 100 Syringe Pump), and optical data collection (Olympus BX51 microscope) subsystems are all described in detail. Procedures for applying the cholesteric liquid crystal mixtures obtained through Pressure Chemicals Ltd. to the microchannel and for collecting liquid crystal data are described as well. Finally, preliminary results are presented, the current status of the technique is stated along with proposed directions for future research work.
Molecular Dynamics Simulation of Homogeneous Nucleation in a Lennard Jones Liquid
Authors: Narendra Aneet D. , Mukherjee Abhijit
Published: August 2009

Examination of metastable states of fluids provides important information pertinent to cavitation and homogeneous nucleation. Homogeneous nucleation, in particular, is an important topic of research. Molecular Dynamics simulation is a well-endorsed method to simulate metastabilitites, as they are limited to mesoscopic scales of length and time and this life-time is essentially zero on a laboratory time scale. In the present study, a molecular dynamics code has been used in conjunction with MOLDY to investigate phase change in a Lennard-Jones liquid. The Lennard-Jones atoms were subjected to different temperatures at various number densities and the pressure was recorded for each case. The appearance of a change of phase is characterized by the formation of clusters or formation of voids as described by the radial distribution function.
Optimal Design of a Two-Stroke Diesel Engine for Aeronautical Applications Concerning Both Thermofluidynamic and Acoustic Issues
Authors: Siano Daniela , Costa Michela , Bozza Fabio
Published: August 2009

Some aspects concerning the development of a prototype of a diesel engine suitable for aeronautical applications are discussed. The engine aimed at achieving a weight to power ratio equal to one kg/kW (220 kg for 220 kW) is conceived in a two stroke Uniflow configuration and constituted by six cylinders distributed on two parallel banks. Basing on a first choice of some geometrical and operational data, a preliminary fluid-dynamic and acoustic analysis is carried out at the sea level. This includes the engine-turbocharger matching, the estimation of the scavenging process efficiency, and the simulation of the spray and combustion process, arising from a Common Rail injection system. Both 1D and 3D CFD models are employed. In-cylinder pressure cycles are utilized to numerically predict the combustion noise. The acoustic study is based on the integration of FEM/BEM codes. In order to improve the engine performance and vibro-acoustic behaviour, the 1D model, tuned with information derived from the 3D code, is linked to an external optimiziation code (ModeFRONTIER™). A constrained multi-objective optimization is performed to contemporary minimize the fuel consumption and the maximum in-cylinder temperature and pressure gradient. In this way a better selection of a number of engine parameters is carried out (exhaust valve opening, closing and lift, intake ports heights, start of injection, etc). The best found solution is finally compared to the initial one and some substantial design improvements are discussed.
Temperature Effect on the Measurement of Stresses in Pipelines Using Ultrasonic Lcr Waves
Authors: Fraga R. S. , Santos A. A. , Andrino M. H.
Published: August 2009

Stress measurement using ultrasonic techniques has emerging as one of the simplest, low cost, and fast technologies for integrity evaluation. The method consists of relating the ultrasonic wave speed with mechanical stress. Critically refracted longitudinal wave, also called Lcr wave, is the kind of wave which is most sensitive to strain and stress. Taking such technique to the field requires the knowledge about how non-controllable factors influence the measurement. Previous works identified the temperature as the main influence variable. This work deals with the magnitude of such influence. Samples of API 5L x70 steel, which is one of the most used materials for pipelines, were cut from an as-manufactured sheet and tested inside a room with controlled temperature. The magnitude of the temperature was allowed to change between 20 and 25°C. Care was taken to control the remaining influence factors. The measurement of the time-of-flight was performed using two ultrasonic transducers placed in a probe specially built for stress measuring with Lcr waves. For such probe, wave speed is proportional to time-of-flight. The same kind of transducers was used in all measurements, but their natural frequencies varied: 2.25, 3.5 and 5.0 MHz. The results showed that the time-of-flight is highly influenced by the temperature and that the coefficient of variation is between 14 and 18 ns/°C or equivalent to 50 MPa/°C. Considering that the method can measure stresses as low as 25 MPa, the temperature effect is very important and must be taken account for measurements in the field.
A Heat Transfer Comparison Between a Synthetic Jet and a Steady Jet at Low Reynolds Numbers
Authors: Farrelly Rayhaan , McGuinn Alan , Persoons Tim , Murray Darina B.
Published: August 2009

A study has been carried out to compare steady jet and synthetic jet heat transfer distributions at low Reynolds numbers. Both jets issued from a 5mm diameter orifice plate with air for the steady jet being supplied by a compressor via a plenum chamber. Tests were conducted for Reynolds numbers ranging from 1000 to 4000, and for non-dimensional surface to jet exit spacings (H/D) from 1 to 6. Dimensionless stroke length (Lo/D) for the synthetic jet was held constant at 8. A significant difference was observed between the steady and synthetic jet Nusselt numbers at low Reynolds numbers and low H/D. In comparison to steady jets, the stronger entrainment of surrounding fluid and the vigorous mixing near the impingement surface are characteristics of synthetic jets that are beneficial to heat transfer. Nonetheless, the steady jet yields higher Nusselt numbers for all test conditions.
Full Field ESPI Vibration Measurements to Predict Fatigue Behavior
Authors: Zanarini Alessandro
Published: August 2009

Durability of mechanical components is usually evaluated by means of virtual modelling, supported by accurate tests for validation. Besides, many structural parts easily exhibit high modal density with complex displacement patterns and strain fields, that might be difficult to estimate through tests on real samples. Electronic Speckle Pattern Interferometry (ESPI) gives nowadays the opportunity to measure 3D displacements with high spatial accuracy in a wide frequency range by means of optical techniques. Here is proposed an experiment-based procedure to exploit the full-field vibration ESPI measurements in the fatigue behaviour assessment of mechanical components. Starting from a brief description of dynamic ESPI technology, attention is here paid to the complex-valued nature of the fields that can be extracted from ESPI, as displacements and receptance FRF data. By means of a robust numerical differentiation approach and a constitutive model, complex-valued strain & stress fields are evaluated to assess fatigue life, accordingly with the durability model adopted. The whole experiment-based approach is applied on an aluminium isotropic rectangular plate and reported in detail.
A Nanostructured Thermosensitive Smart Surface With Integrated Microheater for Wettability Control
Authors: Londe Ghanashyam , Chunder Anindarupa , Zhai Lei , Cho Hyoung J.
Published: August 2009

This paper describes the design and fabrication of a switchable thermosensitive polymer with an integrated microheater as a smart surface platform for wettabilty control. The thermoresponsive surface is synthesized on a glass substrate using the polymer poly(N-isopropylacrylamide) (PNIPAAm) which can change its wettability when subjected to change in temperature. PNIPAAm is hydrophilic when the surface temperature is less than the lower critical solution temperature (LCST) range of about 28–33 °C and is hydrophobic above the LCST range. The PNIPAAm surface is heated by spiral gold microheaters which are fabricated on the lower side of the glass substrate. The contact angle change with change in temperature is tested using a standard goniometer. Time response analysis of the surface is presented. This smart surface can be used as an active or adaptive component for microflow regulation and can be potentially integrated into large scale lab-on-chip (LOC) systems.
Liquid Cooling for Thermal Management of Data Centers
Authors: Mulay Veerendra , Agonafer Dereje , Schmidt Roger
Published: August 2009

The power trend for Server systems continues to grow thereby making thermal management of Data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure than the thermal load of data center. Revised power trend projections by ASHRAE TC 9.9 predict heat load as high as 5000W per square feet of compute servers’ equipment footprint by year 2010. These trend charts also indicate that heat load per product footprint has doubled for storage servers during 2000–2004. For the same period, heat load per product footprint for compute servers has tripled. Amongst the systems that are currently available and being shipped, many racks exceed 20kW. Such high heat loads have raised concerns over limits of air cooling of data centers similar to air cooling of microprocessors. Thermal management of such dense data center clusters using liquid cooling is presented.
Surrogate Fuel Development: The Role of Droplet Burning
Authors: Avedisian C. Thomas
Published: August 2009

This paper examines the role which droplet combustion can play in the development of liquid surrogate fuels. The spherical droplet flame configuration is the canonical configuration of liquid fuel combustion with its one dimensional transport process and spherical soot cloud that surrounds the droplet during burning, thus making it a useful perspective from which to develop a surrogate fuel. The liquid fuel burning process includes a number of characteristic parameters which can serve as useful benchmarks against which to compare performance of a surrogate and real fuel. For sprays and droplets these include burning rate, droplet extinction diameter, droplet number density, mean droplet size and soot emissions. At the same time, not all performance metrics of a real fuel can be replicated by a surrogate. An example is given for the case of a highly sooting aviation fuel (JP8) mixed with an alcohol (hexanol). It is shown that on one hand the spherically symmetric droplet burning rate of the JP8+hexanol blend is almost the same as pure hexanol, thus suggesting hexanol as a surrogate for the mixture in terms of burning rate. On the other, sooting propensities are significantly different for hexanol and the mixture.
Visualization of Joule Heating in Micro-Electrophoretic Flow Using 2-Color Laser-Induced Fluorescence
Authors: Saeki Souichi , Funakoshi Junichi , Saito Takashi , Nakamura Kazuyuki
Published: August 2009

“2-Color laser-induced fluorescence” (2-C LIF) is a novel quantitative temperature measurement method. This can eliminate the undesirable spatio-temporal fluctuation of excitation intensity occurred by light source and channel configuration using a ratio-metric technique with two fluorescence images. Therefore, it can obtain quantitative temperature distribution, and thus simplify temperature calibration in micro channel. In this paper, we applied it to micro-electrokinetic flow. Consequently, the spatial intensity error could be reduced to about 95% as compared with 1-Color LIF image. The temperature distribution in microchannel was quantitatively visualized at the high resolution 0.12×0.12 μm, high sensitivity 1.98%/K and high accuracy ± 0.27 K.
Thin Film Superplastic Forming Model for Nanoscale Bulk Metallic Glass Forming
Authors: Mros Catherine , Rason Kavic , Kinsey Brad
Published: August 2009

Geometrically complex, high aspect ratio microstructures have been successfully formed in Bulk Metallic Glass (BMG) via superplastic forming against silicon dies [1–3]. Although nanoscale features have been created in a similar fashion, there exists a demand to develop these metallic nanofeatures into high aspect ratio nanostructures with controlled geometries. In past research a process model was created to predict the achievable nanoscale feature sizes and aspect ratios through a flow model [4]. The flow model assumes force equilibrium with a viscous term to account for the required force to produce flow and a capillary pressure term required to overcome surface effects which are significant at the nanoscale. In this paper, a thin film model to predict the pressure distribution across the BMG during the forming process when it is in the supercooled liquid state is presented. Silicon molds with various nanofeatures were produced using Deep Reactive Ion Etching to achieve high aspect ratio dies over a relatively large area in order to validate these models.
Assessment of the Performance of Alternative Aviation Fuel in a Modern Air-Spray Combustor (MAC)
Authors: Uryga-Bugajska I. , Pourkashanian M. , Borman D. , Catalanotti E. , Ma L. , Wilson C. W.
Published: August 2009

Recent concerns over energy security and environmental considerations have highlighted the importance of finding alternative aviation fuels. It is expected that coal and biomass derived fuels will fulfil a substantial part of these energy requirements. However, because of the physical and chemical difference in the composition of these fuels, there are potential problems associated with the efficiency and the emissions of the combustion process. Over the past 25 years Computational Fluid Dynamics (CFD) has become increasingly popular with the gas turbine industry as a design tool for establishing and optimising key parameters of systems prior to starting expensive trials. In this paper the performance of a typical aviation fuel, kerosene, an alternative aviation fuel, biofuel and a blend have been examined using CFD modelling. A comprehensive understanding of the kinetics of the reaction for bio aviation fuels at both high and low temperature is necessary to perform reliable simulations of ignition, combustion and emissions in an aero-engine. A novel detailed reaction mechanism was used to represent the aviation fuel oxidation mechanism. The fuel combustion is calculated using a 3D commercial solver using a mixture fraction/pdf approach. Firstly, the study demonstrates that CFD predictions compare favourably with experimental data obtained by QinetiQ for a Modern Airspray Combustor (MAC) when used with traditional jet fuel (kerosene). Furthermore, the 3D CFD model has been refined to use the laminar flamelet model (LFM) approach that incorporates recently developed chemical reaction mechanisms for the bio-aviation fuel. This has enabled predictions for the bio-aviation fuel to be made. The impact of using the blended fuel has been shown to be very similar in performance to that of the 100% kerosene, confirming that aircraft running on 20% blended fuel should have no significant reduction in performance. It was also found that for the given operating conditions there is a significant reduction in performance when 100% biofuel is used. Additionally, interesting predictions were obtained, related to NOx emissions for the blend and 100% biofuel.
Transient Thermal Response of Turbulent Compressible Boundary Layers
Authors: Li Hongwei , Nalim M. Razi , Merkle Charles L.
Published: August 2009

A general numerical method is developed with the capability to predict the transient thermal boundary layer response under various flow and thermal conditions. The transient thermal boundary layer variation due to a moving compressible turbulent fluid of varying temperature was numerically studied on a 2-D semi-infinite flat plate. The Reynolds-averaged boundary-layer equations are solved based on the compressible Falkner-Skan transformation. Turbulence is modeled using a two-layer eddy-viscosity model developed by Cebeci and Smith, and the turbulent Prandtl number formulation originally developed by Kays and Crawford. The governing differential equations are discretized with the Keller-box method. The numerical accuracy is validated through grid independence studies and comparison with the steady state solution. In turbulent flow as in laminar, heat transfer coefficient is initially very different from that obtained from quasi-steady analysis. It is found that, both the transient time scale and the magnitude of the transient heat transfer coefficients differ significantly between turbulent and laminar flow. The more complex variation of transient heat transfer rate in turbulent flow is evident, and needs further study.
Axially Compressed Cylindrical Shells Containing Asymmetric Random Imperfections: Fourier Series Technique and ASME Section VIII Division 1 and 2 Rules
Authors: Brar Gurinder Singh , Hari Yogeshwar , Williams Dennis K.
Published: August 2009

This paper presents the comparison of reliability technique that employ Fourier series representations of random asymmetric imperfections in axially compressed cylindrical shell with evaluations prescribed by ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 and 2. The ultimate goal of the reliability type technique is to predict the buckling load associated with the axially compressed cylindrical shell. Initial geometric imperfections have significant effect on the load carrying capacity of asymmetrical cylindrical shells. Fourier decomposition is used to interpret imperfections as structural features can be easily related to the different components of imperfections. The initial functional description of the imperfections consists of an axisymmetric portion and a deviant portion appearing as a double Fourier series. The representation of initial geometrical imperfections in the cylindrical shell requires the determination of appropriate Fourier coefficients. The mean vector and the variance-covariance matrix of Fourier coefficients are calculated from the simulated shell profiles. Multi-mode analysis are expanded to evaluate a large number of potential buckling modes for both predefined geometries and associated asymmetric imperfections as a function of position within a given cylindrical shell. Large number of shells thus created can be used to calculate buckling stress for each shell. The probability of the ultimate buckling stress exceeding a predefined threshold stress can also be calculated.
Design and Characterization of a Polymeric Photo-Thermal Microgripper for Micromanipulation
Authors: Elbuken Caglar , Gui Lin , Ren Carolyn L. , Yavuz Mustafa , Khamesee M. Behrad
Published: August 2009

Photo-thermally actuated polymer (SU-8) microgrippers were designed, simulated and characterized. The microgrippers were actuated by thermal expansion of compliant polymer parts. The required heat was transferred to the devices by laser absorption. The microgrippers were made of a single SU-8 layer and dyed before the experiments for enhanced laser absorption. Finite element simulation results were used to predict the working range of the grippers. It has been demonstrated that using a simple design 22 μm of deflection can be achieved for a micro-gripper of approximately 900 μm long. The gripping experiments have demonstrated the successful operation of polymeric photo-thermal microgrippers.
Multi-Step Dynamic Control for Enhanced Electrokinetic Transport Characteristics in Microchip Capillary Electrophoresis
Authors: Shao Zhanjie , Ren Carolyn L. , Schneider Gerry E.
Published: August 2009

A numerical model has been developed and is used to study the loading and dispensing processes in on-chip cross-linked microchannels. The electrokinetic transport characteristics and the roles of species’ electrophoretic mobilities and diffusion coefficients on the electrokinetic flow are revealed. A study is also performed on an implementation of multi-stage injection. The study of conventional one-step injection and separation is performed and helps construct a distinct understanding of the processes. Species movement and sample plug development with diffusion are examined; results include concentration profiles and contour plots over a range of injection and separation time. Real-time monitoring of different species’ movements is performed for injection guidance. Some limitations of the separation process are presented with potential solutions, such as the removable tail effect and exceptional quick diffusion. Using innovative dynamic control, efforts are made to control the flow and species transport for improved sample plugs, which is key to achieving excellent electrophoretic separation. Through a series of multi-step injection schemes, four typical sample plugs are produced with specific attributes such as reduced dispersion leakage, desirable sample plug size, enhanced shape, etc. Comparisons of conventional and the proposed methods are performed. Typical resulting sample plugs are evaluated using the two developed parameters of resolution and detectability for numerically simulated separation processes. Depending on requirements, one can generate some specific sample plugs through this multi-step dynamic injection method. The resulting understanding will assist in the design of microfluidic devices for separation by providing insight into the process influences and controls and by identifying areas for further research.
CFD Assisted Design of a Wearable Artificial Pump Lung Device
Authors: Taskin M. Ertan , Zhang Tao , Wu Changfu , Griffith Bartley P. , Wu Zhongjun J.
Published: August 2009

A wearable artificial pump lung (APL) device is being developed to provide ambulatory respiratory support for patients with acute or chronic lung diseases. The design objective of the APL is to create an assembly free, ultracompact, all-in-one system with an optimized blood flow path and minimized device-induced blood damage. This device will combine a magnetically levitated pump/rotor with a uniquely configured hollow fiber membrane (HFM). Computational fluid dynamics (CFD) based multidisciplinary modeling of the device functional performance and biocompatibility was utilized to acquire the precise knowledge of flow field, gas transfer and blood damage characteristics through the whole device. With this knowledge available, the device can be evaluated and optimized to obtain best performance, i.e., maximizing the gas exchange efficiency and minimizing blood damage. The HFM bundle was modeled as porous media with a constant porosity. Flow field was obtained by solving the Navier-Stokes equations, and oxygen transfer process was modeled as a scalar transport. The hemolysis was evaluated based on the shear stress and exposure time distributions which were obtained by post-processing the flow solution. According to the preliminary CFD results, among several designs, the satisfactory one was found regarding flow dynamics, overall biocompatibility and oxygen transfer performances. The average shear stress value was less than 10 Pa, and the outlet oxygen saturation was higher than 95% at standard operating condition. The impeller blade and diffuser angles were compatible to each other resulting in a smooth blood flow in the corresponding region.
Optimal Design of a Composite Scarf Repair Under Uni-Axial Tension Loading
Authors: Breitzman T. D. , Cook B. M. , Schoeppner G. A. , Iarve E. V.
Published: August 2009

Benchmark un-notched strength testing was used to characterize material properties for IM6/3501-6 composite material and to establish parameters for critical failure volume (CFV) (see [8]) analysis tools. Critical failure volume was used to predict the strength of scarfed composites, as well as composites having a scarf repair patch. Baseline repairs were created both without and with over-plies. Simplex optimization was performed on the analytical models to determine the repair stacking sequence that would result in the largest tensile strength for the repairs. The repair was optimized in the linear elastic regime, but strength predictions took into account both geometric nonlinearities of the respective materials and the material nonlinearities of the adhesive. Predicted strengths were in good agreement with experimental results, and the resultant optimal designs increased the strength of the repair under uni-axial tensile load by 10–20%.
Improving Rhodamine B Fluorescence Thermometry in PDMS Microchannels by Photobleaching Absorbed Dye
Authors: Glawdel Tomasz , Almutairi Zeyad , Wang Shuwen , Ren Carolyn
Published: August 2009

A number of microfluidic applications require precise thermal control where in-channel temperature measurements are necessary during the prototyping stage. Rhodamine B based laser induced fluorescence is a common technique used to obtain high resolution measurement of the fluid temperature field. However, PDMS has a tendency to absorb small hydrophobic dyes, such as Rhodamine B, which results in a steady increase in the overall fluorescent signal. This increase in light intensity causes a significant problem that must be overcome to obtain reliable temperature measurements. In this work a simple technique is described to remove the fluorescent signal originating from absorbed Rhodamine B dye particles that does not require surface modification or any significant alterations to the experimental setup. Instead a high power light source is used to photobleach the particles prior to taking images for thermometry analysis. Herein we demonstrate the technique with a conventional fluorescence microscope and a 100W mercury arc lamp and study the temperature field at the intersection of a Y-channel PDMS/glass chip where hot and cold streams merge.
Comparison of the Jordan Rollover System With an Over the Ground Rollover
Authors: Hutchinson John , Friedman Keith
Published: August 2009

The Jordan Rollover System (JRS) is a physical test apparatus which evaluates vehicle rollover protection performance by dropping a rotating vehicle with a stationary CG position onto a moving road bed. This test configuration permits control and monitoring of the rollover test conditions, and allows the rollover test to be conducted in a limited space. A finite element study was conducted to determine how well the JRS test replicates the impact environment of an equivalent over-the-ground rollover event. In particular, the effects of the finite mass of the test roadbed and the test apparatus constraints were examined. The finite element study showed that roof intrusion measures occurring during the JRS test do not vary significantly from those resulting from an unrestrained over-the-ground rollover impact with the same initial conditions.
An Experimentally Observed Link Between Roof Strength and Occupant Ejection
Authors: Bish Jack , Friedman Donald , Caplinger Justin , Rohde David
Published: August 2009

Occupant ejection is a leading cause of injury in rollover accidents. This accident mode has a much higher rate of fatalities and injuries than any other accident mode; front, side or rear. While restraint use is one way to prevent occupant ejection, occupant retention through the use of alternate types of glazing or protecting the existing glazing will greatly reduce the number of occupant ejections. If the roof is strong enough to prevent deformation loading of the glazing, then occupant ejection portal formation will decrease by reducing glazing failure. This effect has been seen in experimental testing such as dolly rollovers and drop tests with reinforced vehicles. A newer test fixture, the Jordan Rollover System (JRS), allows for examination of glazing failure as a function of roof deformation and roof strength for similar impacts for production vehicles of various strengths. This study illustrates that glazing failure, and hence occupant ejection portal creation, decreases with increasing roof strength and decreasing roof deformation.
Continuum Modeling and Analysis of the Frictional Interaction Between a CNT and a Substrate During Dragging
Authors: Adams George G. , Nagappan Palaniappan , McGruer Nicol E.
Published: August 2009

A simple method to determine the frictional interaction between a carbon nanotube (CNT) and a substrate is analyzed for feasibility. In this technique an atomic force microscope (AFM) tip is used to drag a CNT along a substrate. Then the deformed shape of the CNT can be viewed either with the AFM or in an SEM. An analysis of the deformed shape allows the determination of the frictional interactions which occurred during dragging. It is important to quantify these interactions in a variety of potential applications of nanotechnology. In one such example, a CNT based nanoswitch consists of a CNT bridging over a trench. Actuation of the CNT causes it to stretch and can lead to partial slip at the interface. This slip causes hysteresis which has been observed in the mechanical actuation of a CNT bridge. In this paper continuum level modeling of the frictional interaction is used to determine the relationship between the shape of the CNT and the frictional interaction which occurred between the CNT and substrate during dragging. The model and analysis indicate that this method should be feasible for CNTs with aspect ratios approximately in the 100–250 range.
Fabrication and Characterization of Nano-Structuring Polymeric Surfaces for MEMS Applications
Authors: Takahashi Yusuke , Teh Kwok Siong , Lu Yen-Wen
Published: August 2009

Using external stimuli to control surface properties, such as surface topology or wettability, has been of great interest. This paper presents the fabrication, mechanism, and analysis of an active method that modulates surface nano-topology and wettability of polymeric films. The polymeric film possesses the unique property of electrical potential-induced wettability conversion: when its doping level is electrically altered, the interstitial ions are incorporated or released, causing the polymer network to stretch and thereby changing its surface morphology.
Design of a Microscale Breather for Two-Phase Thermal Management Devices
Authors: Alexander B. R. , Wang E. N.
Published: August 2009

Two-phase microchannels promise an efficient method to dissipate heat from high performance electronic systems by utilizing the latent heat of vaporization during the phase-change process. However, phase-change in microchannel heat sinks leads to challenges that are not present in macroscale systems due to the increasing importance of surface tension and viscous forces. In particular, flow instabilities often occur during the boiling process, which lead to liquid dry-out in the microchannels and severely limits the heat removal capabilities of the system. We propose a microscale breather device consisting of an array of hydrophobic breather ports which allow vapor bubbles to escape from the microchannels to improve flow stability. In this study, we use the combination of microfabricated structures and surface chemistry to separate vapor from the liquid flow. We designed test devices that allow for cross-sectional optical visualization to better understand the governing parameters of a breather design with high vapor removal efficiencies and minimal liquid leakage. We examined breather devices with average liquid velocities ranging from 0.5 cm/s to 4 cm/s and breather vacuum levels between 1 kPa and 9 kPa on the maximum gas removal rate through the breather. We demonstrated successful breather performance. In addition, a model was developed that offers design guidelines for future integrated breathers in microchannel heat sinks. The breathers also have significant promise for other microscale systems, such as micro-fuel cells, where liquid-vapor separation can significantly enhance system performance.
Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air Mixtures in a Reciprocating Engine
Authors: Cordon Dan , Beyerlein Steve , Cherry Mark , Steciak Judi
Published: August 2009

Lean ethanol-water/air mixtures have potential for reducing NOx and CO emissions in internal combustion engines, with little well-to-wheels CO2 emissions. Conventional ignition systems have been unsuccessful at igniting such mixtures. An alternative catalytic ignition source is being developed to aid in the combustion of aqueous ethanol. The operating principle is homogeneous charge compression ignition inside a catalytic pre-chamber, which causes torch ignition and flame propagation in the combustion chamber. Ignition timing can be adjusted by changing the length of the catalytic core element, the length of the pre-chamber, the diameter of the pre-chamber, and the electrical power supplied to the catalytic core element. To study engine operation, a 1.0L 3-cylinder Yanmar diesel engine was converted for ethanol-water use, and compared with an unmodified engine. Comparing the converted Yanmar to the stock engine shows an increase in torque and power, with improvements in CO and NOx emissions. Hydrocarbon emissions from the converted engine increased significantly, but are largely due to piston geometry not well suited for homogeneous charge combustion. No exhaust after treatment was performed on either engine configuration. Applying this technology in an engine with a combustion chamber and piston design suited for homogeneous mixtures has the potential to lower emissions to current standards, with a simple reduction catalytic converter.
Numerical Modeling of Two-Phase Flow in a Bipolar Plate of a PEM Electrolyzer Cell
Authors: Nie Jianhu , Chen Yitung , Boehm Robert F.
Published: August 2009

Optimization of electrolysis cell for producing hydrogen is dependent of a set of complex physical and chemical processes simultaneously occurring within the electrolysis cell. Similar to fuel cells, it has been demonstrated that these processes are strongly dependent on the fluid dynamics inside the electrolysis & fuel cell. Bipolar plates are important components of PEM electrolysis cells because they are the first stage of the flow distribution system. Numerical simulations were performed for three-dimensional two-phase water/oxygen flow in the anode side of a bipolar plate with a diagonal flow design. The water flowrate was maintained as constant of 260 ml/min, while the oxygen bubble generation rate was assumed to change from 0–0.014 g/s. Numerical results reveal that a minimum of the peak values of mainstream velocity component in the channels develops in the middle of the plate. Pressure drop and volume fraction of oxygen at the exit become higher as the oxygen bubble generation flowrate increases. The irregular velocity profile (locally low velocity magnitude near the exit port section) is not observed when the oxygen bubble flowrate is relatively low.
Numerical Simulation on Solution Residence Time in Air-Agitated Seed Precipitation Tank in Industrial Production of Alumina
Authors: Yan Hongjie , Zhou Ping , Zhou Jiemin , Ge Shiheng
Published: August 2009

The residence time of solution has a significant influence on the process of reaction in industrial production of alumina. In this paper, the numerical calculation on residence time is adopted based on the simulation on flow flied of air-agitated seed precipitation tanks with different structure. The validity of mathematic model is proved by model experiment. The calculation result shows that the residence time of solution in the optimized tank is longer than that of in traditional tank, and it is helpful to prompt the alumina’s output in seed precipitation tank with new structure.
Multi-Degree-of-Freedom Simulation of Micro-Machined Sensors Under Mixed-Signal Control
Authors: Breit Stephen R. , Welham Christopher J. , Rouvillois Stephane , Kraft Michael , King David , Combes David , McNie Mark
Published: August 2009

A general method of modeling and simulating a micro-machined inertial sensor under closed-loop control by a sigma-delta modulator is presented. The model of the mechanical subsystem captures all 6 mechanical degrees of freedom and the complex electrostatic fields in electrostatic comb drives. A technique is presented that makes transient simulations of the sophisticated mechanical model in conjunction with a modulator more tractable. The benefits of the modeling and simulation approach are demonstrated on an example consisting of a single-axis accelerometer and a second-order sigma-delta modulator. The example shows that transient simulations of the complete system can be performed in relatively short time while capturing cross coupling between mechanical modes of the sensor.
An Improved Thermoregulatory Model for Cooling Garment Applications With Transient Metabolic Rates
Authors: Westin Johan K. , Kapat Jayanta S. , Chow Louis C.
Published: August 2009

Current state-of-the-art thermoregulatory models do not predict body temperatures with the accuracies that are required for the development of automatic cooling control in liquid cooling garment (LCG) systems. Automatic cooling control would be beneficial in a variety of space, aviation, military, and industrial environments for optimizing cooling efficiency, for making LCGs as portable and practical as possible, for alleviating the individual from manual cooling control, and for improving thermal comfort and cognitive performance. In this paper, we modify the blood flow dynamics of a state-of-the-art thermoregulatory model and identify a new signal, i.e. the rate of change of hypothalamus temperature weighted by the hypothalamus error signal, which governs the thermoregulatory response during conditions of simultaneously increasing core and decreasing skin temperatures. We compare temperature predictions with experimental data for a 700 W rectangular type activity schedule in an LCG environment. The new thermoregulatory model predicts rectal and mean skin temperatures with root mean square deviations of 0.09°C and 0.69°C, respectively, which results in a 44% reduction of the mean absolute body heat storage error. It appears that the new thermoregulatory model can, with some additional improvements outlined here, satisfy the very strict accuracy requirement that is needed for automatic cooling control development.
Complexity and Frailty: Multiscale Entropy of Balance Dynamics During Quiet Standing and Dual-Task: The Mobilize Boston Study
Authors: Kang Hyun Gu , Costa Madalena , Priplata Attila A. , Starobinets Olga V. , Goldberger Ary L. , Peng Chung-Kang , Kiely Dan K. , Cupples L. Adrienne , Lipsitz Lewis A.
Published: August 2009

Balance control during standing is attributable to the complex, nonlinear interactions of multiple postural control systems, manifested as the highly irregular displacements in center of pressure (COP) during standing. Aging and associated frailty may result in the degradation of these complex interactions and manifest as a loss of complexity in COP dynamics. Furthermore, frail individuals may not be able to adapt to a superimposed stress that challenges balance, leading to falls. To test these hypotheses, data were analyzed from the MOBILIZE Boston Study, an ongoing population-based study of community-dwelling older adults. Each participant’s frailty phenotype (not frail, pre-frail, frail) was determined using the Fried et al. 2001 definition. 551 participants (age 77.9±5.5) stood on a balance platform, with or without concurrently performing serial subtractions. Complexity of balance dynamics over multiple time scales was quantified using multiscale entropy (MSE), a more sensitive measure of physiologic health than variance. Of the participants, 39% were pre-frail and 6% were frail. Baseline MSE was lower with each successive frailty condition (p<0.002). When performing the cognitive task, MSE was lowered similarly in all groups (p<0.001). Frailty was associated with a loss of complexity in the dynamics of postural sway, which may be due to the degradation of integrated postural control networks that enable upright stance. Performance of a dual-task further reduced this complexity. Cognitive distractions during standing may further compromise balance control in frail individuals, which may explain their increased fall risk.
Investigation of the Holding Capability of a Single Dielectrophoretic Gate for the Front-End Device of a Bio-Detection System
Authors: Song Hongjun , Bennett Dawn J.
Published: August 2009

This paper will examine the holding capability of a single dielectric gate. Bennett et al. have previously developed a single dielectrophoretic (DEP) gate for the front-end device of a bio-detection system [12]. By applying a high frequency AC electric field on the top and bottom electrodes, particles which are negatively polarized are repelled from the high field gradient region near the electrodes, and the particles are held in place due to the balancing of the DEP force and the Stokes drag force. However, the particles will flush through the channel if the fluid flow force becomes larger than that the DEP force. Thus, there is a holding capability for the single dielectrophoretic gate which corresponds to the maximum flow rate at which particles can balanced by the DEP force. In this paper, we present a 3D numerical simulation to investigate the parameters that influence the DEP force such as the width of the electrodes, the applied electric field, the ratio of the width of top electrode to the bottom of electrode as well as the horizontal shift between the top electrode and bottom electrode. A select group of parameters is studied in order to achieve the optimal holding capability of the single dielectrophoretic gate. The influence of the phase variation of the AC electric field between the top electrode and bottom electrode is also analyzed.