bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Pulse Propagation in Pure Sodium Fluoride at Low Temperatures From Ballistic to Diffusive Conduction
Authors: Ma Yanbao
Published: August 2012

In this paper, heat pulse propagation in pure NaF at low temperature is studied by using hydrodynamic equations of a weakly interacting phonon gas. The observed longitudinal waves, transverse waves, second sound waves, and diffusive waveforms from the experiments conducted in early 1970s are numerically reconstructed. In the numerical simulations, the phase velocities of the longitudinal waves and the transverse waves are based on the experimental results, while two relaxation times for normal scattering process (τN) and resistive scattering process (τR) respectively are adjusted to fit the arrival time of second sound or to fit the observed waveforms observed in the experiments. The waveforms based on numerical results can fit the observed waveforms quite well. It is elucidated how heat pulse is transmitted by different waves in the dielectric crystal from ballistic to diffusive regions.
Development and Performance Evaluation of High Temperature Concrete for Thermal Energy Storage for Solar Power Generation
Authors: John Emerson E. , Hale W. Micah , Selvam R. Panneer , Brown Bradley
Published: August 2012

This paper proposes concrete bricks as the main energy storage medium to replace aggregates in the thermocline thermal energy storage system. By developing a feasible concrete mixture, the root cause of thermal ratcheting which is the settlement of the aggregates is immediately eliminated. Fourteen concrete mixtures were submerged in molten salt at 585°C for 500 hours and were also subjected to 30 thermal cycles from 300 to 600°C in a heating furnace. The results show that 5 of the 14 mixtures exhibited adequate mechanical properties after being subjected to the thermal cycling testing regimen. All mixtures exhibited an increase in compressive strength after 500 hours of exposure in molten salt at 585°C. This illustrates that concrete as an alternative to the use of quartzite rock and silica sand is feasible.
High-Resolution, Non-Contact Angular Measurement System for PSA/RSA
Authors: Sloat Ronald , Pan Jianbiao
Published: August 2012

A non-contact angular measurement system for Pitch Static Attitude (PSA) and Roll Static Attitude (RSA) of hard disk drive sliders is designed and built. Real-time sampling at over 15 KHz is achieved with accuracy of +/−0.05 degrees over a range of approximately 2–3 degrees. Measuring the PSA and RSA is critical for hard drive manufacturers to control and improve the quality and reliability of hard drives. Although the hard drive industry is able to measure the PSA and RSA at the subassembly level at this time, there is no system available that is able to measure PSA/RSA at the final assembly level. This project has successfully demonstrated a methodology that the PSA/RSA can be reliably measured in-situ using a laser and position sensitive detector (PSD) technology. A prototype of the measurement system has been built. This device will allow a continuous measurement between the parked position on the ramp and the loading position just off of the disk surface. This measured data can be used to verify manufacturing processes and reliability data.
Evaluation of Two-Phase Cold Plate for Cooling Electric Vehicle Power Electronics
Authors: Wang Peng , McCluskey Patrick , Bar-Cohen Avram
Published: August 2012

Rapid increases in the power ratings and continued miniaturization of semiconductor devices have pushed the heat flux of power electronics well beyond the range of conventional thermal management techniques, and thus maintaining the IGBT temperature below a specified limit has become a critical issue for thermal management of electric vehicle power electronics. Although two-phase cold plates have been identified as a very promising high flux cooling solution, they have received little attention for cooling of power electronics. In this work, a first-order analytical model and a system-level thermal simulation are used to compare single-phase and two-phase cold plate cooling for Toyota Prius motor inverter, consisting of 12 pairs of IGBT’s and diodes. Our results demonstrate that with the same cold plate geometry, R134a two-phase cooling can substantially reduce the maximum IGBT temperature, operate all the IGBT’s at very uniform temperatures, and lower the pumping power and flow rate in comparison to single-phase cold plate cooling. These results suggest that two-phase cold plate can be developed as a low-cost, small-volume, and high-performance cooling solution to improve system reliability and conversion efficiency for electric vehicle power electronics.
Thermal Performance Comparison for Five Liquid Heat Sink Designs
Authors: Greene Christopher , Manteufel Randall D. , Karimi Amir
Published: August 2012

Five high-flow liquid-cooled heat sink designs are compared for the cooling of a single chip CPU. Five distinctive design configurations are considered with regard to the introduction, passage, and extraction of cooling fluid. The typical water flow rate is about 3.8 liters per minute (lpm) with flow passages in the primary heat transfer area ranging from 2 to 0.1mm. The design configurations are summarized and compared, considering: the primary convective heat transfer area, flow passage streamlining, acceleration mechanisms, and nominal fluid velocity in the primary heat transfer area. Overall pressure drop and thermal resistance are compared for varying flow rates of water. At the nominal flow, the pressure drops ranged from 1 kPa to 20 kPa. In the restrictive designs, such as nozzles, flow acceleration accounts for the largest source of pressure drop. In some designs, a large fraction of the overall pressure drop is due to circuitous flow associated with the introduction and/or extraction of flow which contributes little to heat removal. At the nominal flow, the overall thermal resistance varied from 0.14 to 0.18 C/W. As flow rate increases the overall thermal resistance decreases. Results indicated that 80 to 85% of the total thermal resistance is due to conduction and about 15 to 20% attributed to convection at the nominal flow rate. There is minimal thermal benefit for flow rates beyond twice the nominal while this substantially increases fluid pumping requirements. This study highlights design features which yield above average heat transfer performance with minimal pressure drop for high-flow liquid-cooled heat sinks.
A Mathematical Model of a Modified Voice Coil Energy Harvester
Authors: Hekmati Alireza , Arzanpour Siamak
Published: August 2012

This paper presents a mathematical modeling of a modified voice coil generator, which consists of a moving coil within a fixed magnetic circuit. The simulation has been done with Comsol Multiphysics software, which is a powerful tool to demonstrate the pattern of magnetic field and calculate the induced current in the coil. In our simulations, the magnetic circuit consists of the magnetic conductor and the air gap. In this analysis, the magnetic flux density and the magnetic field intensity are calculated. Moreover, through calculation of the total reluctance of the magnetic circuit and employing the ohm’s law for magnetic circuits, the effect of the length and cross section of the total circuit on the magnetic flux are investigated. Finally, a pattern for the magnetic flux density are demonstrated and the simulation result indicates that the magnetic field is well concentrated on the coil area, therefore this prototype can capture and convert most of the kinetic energy to electricity. A prototype has been fabricated and tested on the shaker. The experimental results indicate that this setup is able to produce the maximum voltage of 0.326 V and the peak power equal to 2.605 mW in 35 Hz frequency and 1 mm peak to peak amplitude.
Theoretical Analysis on Film Thickness of Intertube Falling-Film Flow With a Countercurrent Gas Flow
Authors: Ruan Binglu , Li Huan , Wang Qiuwang
Published: August 2012

In falling–film type of heat exchangers, gas/vapor usually exists, and its effect on falling-film mode transitions and heat transfer could not be neglected. It could impact the film thickness, which is an important parameter to determine the thin-film heat transfer performance, or even destroy falling-film modes and significantly deteriorate the heat transfer. However, there have been very few studies of countercurrent gas flow effects on the film thickness. In this paper, the falling-film film thickness with and without liquid-gas interfacial shear stress due to the countercurrent gas flow was studied. A two-phase empirical correlation is used to solve the momentum equation. Calculation results were compared with available experimental data in literatures for validation. Reasonable agreement was achieved. Thus, the two-phase correlation for predicting shear stress of a thin film flow inside a vertical rectangular channel has been extended to a new type of flow. Effects of film Reynolds number, gas velocity, and gas-channel equivalent hydraulic diameter on the film thickness were studied. It is shown that the countercurrent gas flow thickened the falling film. The increased film thickness can shift the mode transitional Reynolds number and reduce the heat transfer coefficient, corroborating the conjecture in our earlier work.
Robust Tremor Attenuation for Single DOF Model of Human Elbow Joint With Parametric Uncertainties
Authors: Taheri Behzad , Case David , Richer Edmond
Published: August 2012

In this article, a tremor attenuation algorithm is designed based on the backstepping method. A high-pass filter was designed in frequency domain and its state space realization was derived to be used as an estimator for the tremorous motion. Using the pole placement method an appropriate state feedback control law was designed to stabilize its output. The dynamics of the human arm was considered and a backstepping controller was derived for the applied torque to the arm. The global asymptotic stability of the resulting closed-loop system was proved using Lyapunov method. The controller is robust against parametric uncertainty and unmodeled nonlinear terms of the arm dynamical model. Simulation results shows the successful suppression of tremor in the presence of parametric uncertainty.
The Thermophysical Properties of the NaNO3-KNO3, LiNO3-NaNO3, and LiNO3-KNO3 Systems
Authors: Coscia Kevin , Neti Sudhakar , Oztekin Alparslan , Nelle Spencer , Mohapatra Satish , Elliott Tucker
Published: August 2012

The present work comprises of thermophysical properties of nitrate-based binary heat transfer fluids of various compositions. For various nitrate mixtures, specific heat, latent heat of fusion, and viscosity as a function of shear rate are reported at various temperatures. Phase diagrams have also been constructed for these binary mixtures using differential scanning calorimetry. It was found that the contribution of the lithium nitrate on the binary mixtures had the largest increase in specific heat. As with most fluids, viscosity significantly decreases with temperature. The latent heat of the binary mixtures cannot be determined by using simple mass-averaging. The results presented in this work are expected to make a significant impact on the development of economical and industrially viable nitrate mixtures for solar power applications.
Mechanical Characterization and Modeling of Corrugated Metal Foams for SOFC Applications
Authors: Berke Ryan B. , Walter Mark E.
Published: August 2012

Planar solid oxide fuel cells (SOFCs) are made up of repeating sequences of thin layers of cermet electrodes, ceramic electrolytes, seals, and current-collectors. For electro-chemical reasons it is best to keep the electrolyte layers as thin as possible. However, for electrolyte-supported cells, the thin electrolytes are more susceptible to damage during production, assembly, and operation. The latest-generation electrolyte-supported SOFCs feature metallic foam current-collectors which relay current between the energy-producing materials and the rest of the circuit. These foams are stamped into a corrugated shape which is intended to reduce the compressive loads which are transferred through the stack onto the brittle electrolyte, but the mechanical behavior of the foams remain to be fully understood. Characterization of the corrugated metal foams consists of comparison of load-vs.-displacement behavior between experimentally measured compression data and a single-component finite element model which isolates the foam from the rest of the stack. Mechanical properties of the foam are found using an iterative approach, in which the material properties used as inputs to the model are changed until the load-displacement data best agrees with experiments. The model explores the influence of elastic and plastic properties in combination with and without friction. Thus obtained, the properties can then be used in a stack model to determine which parameters can best reduce the demands on the electrolyte without sacrificing electrochemical performance.
Investigation of Surface Tension Effects of a Water-Hexadecane Interface on Silicon Microparts
Authors: Liberti Caroline E. , Crane Nathan B.
Published: August 2012

Assembly at sub-millimeter dimensions is a challenging process that is often not economically feasible. This limits many systems to in-situ fabrication from compatible materials. If freed from these limitations on processes and materials, it might be possible to improve microsystem performance. One critical application of recent interest is in the assembly of small crystalline photovoltaic cells onto low-cost and possibly flexible modules [1].
Flexoelectric Materials and Structures for M/NEMS
Authors: Huang Wenbin , Kim Kyungrim , Zhang Shujun , Yuan Fuh-Gwo , Jiang Xiaoning
Published: August 2012

Recent research progress on flexoelectricity suggests that dramatic enhancement of effective piezoelectric properties desirable for advanced M/NEMS, in principle, is attainable through flexoelectric (FE) effect and scale effect. In this paper, the transverse flexoelectric coefficient μ12 of barium strontium titanate (BST) microcantilevers with thicknesses ranging from 1.4 mm down to 30 μm was measured at room temperature. It was found that μ12 remains to be constant (8.5 μC/m) for all fabricated microcantilevers. Effective piezoelectric coefficients of these microcantilevers were also calculated, indicating that significantly increased effective piezoelectric coefficients can be obtained from microcantilevers with thickness of microns and nanometers, which is promising for micro/nano electromechanical systems (M/NEMS).
Fatigue Behavior of Natural Fiber Reinforced Thermoplastic Composites in Dry and Wet Environments
Authors: Fotouh Ahmed , Wolodko John
Published: August 2012

Over the past decade, there has been an increased demand for products manufactured using sustainable materials. Natural fiber composites are seen as an excellent replacement for synthetic fiber composites due to their low density, good mechanical properties (stiffness), good thermal/acoustic insulation properties and environmental benefits (waste stream utilization and low carbon footprint). While there has been a considerable number of studies examining the short-term behavior of natural fiber composites, very limited work has been done to characterize their long-term durability under cyclic loading. In this study, the fatigue behavior of a natural fiber reinforced thermoplastic composite material was investigated. Cyclic fatigue experiments were conducted on hemp fiber reinforced high density polyethylene (HDPE) at various fiber volume fractions, and under both dry and wet ambient conditions. Using a stress level concept, a generalized model was developed to predict the fatigue life of the various composite formulations tested. The concept of pseudo-plastic flow was incorporated in the fatigue model to form a new model, which is capable of simulating fatigue behavior at different frequencies, fatigue stress ratios and volume fractions.
An Experimental Study on the Effects of Agitation on Forced-Convection Heat Transfer
Authors: Agrawal Smita , Simon Terrence W. , North Mark , Cui Tianhong
Published: August 2012

Most active electronics cooling modules are cooled by forced flow driven by a rotating fan. Recently, a piezoelectrically-driven plate driven in a flapping mode has been proposed as a replacement. This fan gives both flow movement and agitation. To raise effectiveness, reduce size, and otherwise meet the demands of future electronics cooling devices, better methods are continually being sought. The present research explores the possibility of using a piezoelectric stack to oscillate blades in a translational mode to agitate the flow in a heat sink channel, thus enhancing heat transfer on the channel walls. The aim is to disrupt the thermal boundary layer while introducing strong pressure gradients and channel vorticity. In the present cooling module design, this agitation is used in conjunction with a rotating fan which provides through-flow. The dimensions of actual heat sink channels are small, making detailed heat transfer measurements difficult and inaccurate. Only global averages can be measured. Thus, a Large Scale Mock-Up (LSMU) heat sink channel was created to document agitation enhancement of heat transfer. The LSMU is a single channel arrangement which simulates one channel of a 26-channel heat sink being developed. Results from it complement actual-scale experiments in single and multiple channels. With the LSMU, the effect of frequency and amplitude of agitation on heat transfer along different sections of the channel are assessed. At lower velocities of agitation, the heat transfer coefficient is mainly governed by the velocity of agitation (frequency times amplitude) irrespective of the value of frequency or amplitude. However, at higher velocities, amplitude seems to be somewhat more important than frequency in enhancing heat transfer. The results of the present study show strong effectiveness of plate agitators.
Testing Shape Memory of Porous Polymer Tissue Engineering Scaffolds in Compression
Authors: Lippincott Hugh , Schmidt Daniel F.
Published: August 2012

Shape recovery from memory by porous scaffolds for tissue engineering offers easier insertion and self-retention following placement by minimally invasive surgery. Shape memory testing of porous polymer xerogels focuses on the compression cycle and the special aspects of the cycle and equipment used. This contrasts with normal tensile shape memory (SM) testing. In this work a dynamic mechanical analyzer (DMA) was used on small samples to quickly yield measurement of the SM restoration at various stress levels to emulate the forces exerted on the body by a tissue engineering (TE) scaffold returning to its permanent shape. The DMA testing of a hexamethyl diisocyanate trimer crosslinked castor oil (CO) / polycaprolactone (PCL) blend yielded repeated SM with no creep. The porous CO/PCL showed repeated compressive SM at 50% strain with a SM stress-free recovery ratio of 100%. The peak SM recovery work of 6.4 KJ/m3 was measured at 0.5 MPa stress and 6% to 12% strain. In addition to the potential utility of these materials in a tissue engineering setting, the test methods described here are relevant to a broad range of shape memory applications, from medical devices to morphing airframes to self-deploying structures.
Studying the Effect of Number of Blades on the Aerodynamic Performance of a Venturi Effect Fluid Turbine (VEFT) by Numerical Simulation
Authors: Izadi M. , Bahrami A. , Aidun D. K. , Marzocca P. , Ghebreselassie B. , Williams M.
Published: August 2012

Vertical-axis wind turbines (VAWTs) are a type of wind turbine where the main rotor shaft is set vertically. A commercial VAWT with two different designs, i.e., 4-blade and 8-blade is numerically simulated and the effect of number of blades on the aerodynamic characteristics is investigated. Commercial software (ANSYS FLUENT™ 12.1.4) is used for simulations. The simulations are performed with stationary blades as well as rotating blades with different rotation speeds up to 10 rad/s while the k-ε model is used for simulation of turbulent air flow around VAWT. The location and magnitude of the maximum air velocity and dynamic pressure are determined from the relevant contours and the results are compared. The fundamentals of the flow physics in the close proximity of the rotor and the wake are investigated by numerical simulations. The magnitude of the net torque generated by VAWT is also calculated and the results are compared. The results show that increasing the number of blades increases the magnitude of the torque generated by VAWT and, therefore, increases the efficiency of the wind turbine. However, a VAWT with a higher number of blades is more expensive due to higher design and manufacturing costs. Accordingly, there is an optimum design with respect to efficiency and capital investment. The current study offers a practical and inexpensive method to find such an optimum design and can be applied to both horizontal-axis and vertical-axis turbines.
Investigation of Layered and Periodic Pattern Material Structures for Automotive Vibro-Acoustic Abatement
Authors: Al-Zubi Mohammad , Ayorinde Emmanuel , Witus Gary , Dundar Akif
Published: August 2012

The reduction of vibration and noise in and across several components and modules of the automotive, such as the panels, doors, engine covers, seats, and others, is of primary importance. The NVH performance may be a crucial factor in the purchase decisions of numerous buyers. In this work, experimental and other investigations are made on monolayer, composite and periodic material constructions to assess their suitability for minimal transmission of noise and vibration. The results give some suggestions for design directions to follow in order to achieve better performances.
Control of Wall Thickness of Blood Vessel Biomodel Made of Poly (Vinyl Alcohol) Hydrogel by a Three-Dimensional-Rotating Spin Dip-Coating Method
Authors: Kosukegawa Hiroyuki , Kiyomitsu Chihaya , Ohta Makoto
Published: August 2012

To control the thickness of a PVA-H biomodel of human arteries and veins (150 to 800 μm in thickness), a three-dimensional-rotating spin dip-coating apparatus was fabricated. A straight aluminum cylinder (Ra = 0.16 μm) was employed as substrate. Spin dip-coating was carried out in a cooling chamber at 10°C for 1 hour, and then the substrate was quenched at −30°C for gelation of PVA. The thickness of the deposited PVA-H was measured by using a confocal laser displacement meter. Under the experimental conditions employed, PVA-H with a thickness over 30 μm was obtained. The thickness linearly increased with repeated dippings. The thickness of PVA-H depends on the dipping withdrawal speed, the viscosity of the PVA solution, and the diameter of the substrate. Furthermore, the thickness of PVA-H was found to be almost the same when the viscosity of the PVA solution was constant, regardless of the concentrations of PVA. These results indicate that a tube-shaped PVA-H biomodel with desired thickness and physical properties can be obtained by using a spin dip-coating technique and that PVA-H can mimic the wall thickness of various arteries and veins.
Flow Through Coated Coronary Stented Arteries: A Review
Authors: Gogineni Aneesha , Ravigururajan T. S.
Published: August 2012

This paper reviews the recent literature on the stent applications and their recent advancements due to some controversies. The paper consists of two parts flow modeling of stents and a comparison between normal and stenosed artery. It also includes a comparison of stent geometries to determine hemodynamically favorable stents. In spite of many advantages bare metal stents are found to be unfavorable. However the study of stents based on flow and design recommend stent coatings. In comparison with bare metal stents, metal coated stents proved to be more efficient in terms of restenosis. Most of the metal coatings have less fluoroscopic visibility and low tensile strengths and hence drug eluting stents were studied. Although drug eluting stents were proved to be efficient in controlling restenosis, they have issues in patients with co-morbidities. For this reason, polymer and carbon coatings were studied in detail which showed better results than drug eluting stents. Biodegradable stents on the other hand inhibit smooth muscle cell proliferation and a decrease in neointimal proliferation. At present research on polymer, carbon and biodegradable stents are actively pursued for stent therapy applications.
Investigation of Lightweight Space Radiator Design for Low and No Gravity Environments
Authors: Bieger Virginia , Ma Jian
Published: August 2012

Space heat rejection is heavily relying on radiator subsystem, which is only depended on pure radiation heat transfer and typical convection is not available. Increased efficiency coupled with reduced mass is of strategic importance in space thermal system. This paper reviews the existing individual aspects of lightweight space radiator subsystem designs under low and no gravity environments, i.e. working fluids, fin design, or optimization, based on standard construction materials. In addition, new concept approaches using latest technologies and their challenges are also investigated in this study. Common designs include heat pipe, liquid sheet, and liquid droplet radiators, the latter two being more conceptual than functional. Most technological advances have been made in the materials of construction and optimization areas while using the traditional heat pipe design since 1960s. Carbon composites are the most promising material for construction, as they possess a good heat transfer rate while minimizing the weight of the system. Working fluids selection has more to do with the operational temperature range than the system design, though construction materials must be taken into account when selecting a working fluid. Fin design is the least reported on, but the general consensus is triangular fins are the best option for minimizing weight while increasing surface area for radiation. Based on the review of current research, the most promising design would be a carbon composite heat pipe with a working fluid of liquid water or ammonia and triangular fins.
Spherical Indentation of Nickel Thin Film on Steel-4340 Substrate
Authors: Prakash Raghu V. , Arunkumar S. , Ramesh Ajith
Published: August 2012

In this paper, finite element simulations of spherical indentation of Nickel thin film on Steel-4340 are studied for single and multiple cycle of indentation as well. The objective was to understand the mechanics of coated systems, from load-displacement (P-h) curves, stress distribution in the film and the effect of substrate yield strength on the indentation response. The loading portion of P-h curve showed displacement bursts and the reason for this is investigated. A transition in the deformation behavior of the film from Hertz-type to flexure was observed for a normalized indentation depth of h/tf≈0.2. The influence of coating–substrate properties on P-h curve is also investigated for different h/tf ratios and yield strains. Attempts are also made to explore the possibility of understanding the creep-fatigue behavior of coated specimen subjected to cyclic indentation at room temperature from Indentation depth v/s time, Indentation depth v/s number of cycles and Plastic dissipation energy v/s number of cycles curve.
Study of Alkane Thiols as a Blocking Mechanism for Specific Adsorption for Application of Charge Selective Membrane Transport
Authors: Agonafer Damena D. , Chainani Edward , Oruc Muhammed E. , Lee Ki Sung , Shannon Mark A.
Published: August 2012

Electrodialysis (ED) is an electrochemical process used for separation of ions across perm-selective membranes. ED uses a DC bias to selectively transport ions across membranes for applications ranging from desalination of water to demineralization of fruit juice. The energy cost of ED is due to accumulation of hydroxide and hydronium ions from the electrochemical process of water; additionally there is the cost of using platinum electrodes. This paper addresses the idea of using polycarbonate track etched membrane (PCTE) coated with gold between the membranes to reduce the energy cost and to explore a wider selection of electrode materials. This paper aims to show how thiol monolayers on gold can be used as ideal polarizable electrodes (electrode behaves like a capacitor with only charging current and no faradaic current) for application of potential to the membrane surface double layer. We report the characterization of such monolayers on gold-coated microscope slides. The goal is to control the diffuse layer potential at each membrane-solution interface while at the same time prevent adsorption on the electrode surface and minimize Faradaic activity due to electrolyte and redox species in solution. This lays the groundwork for the application of thiol-modified polycarbonate track-etched membranes for ion-selective transport. The paper proposes the use of electrochemical impedance spectroscopy (EIS) to measure characteristics of gold (Au)-coated membranes and their inherent limitations. In this work, the fabrication of a membrane permeate flow cell is described with the aim of subsequently studying the transport of ions through conductive polycarbonate track etched membrane (PCTE) by interrogating the system using EIS and CV measurements. In particular, we would like to ascertain the voltage range that can be applied to the Au-coated membrane without getting a considerable faradaic activity; the difference between platinum and Au electrode; the effects of different electrolyte concentrations and various applied DC potentials.
A Study on the Motion of Micro-Parts on a Saw-Tooth Surface by the PTV Method
Authors: Le Phuong Hoai , Dinh Thien Xuan , Mitani Atsushi , Hirai Shinichi
Published: August 2012

This study investigates the motion of micro parts on several vibratory plates with saw-tooth surface profile driven by a piezoelectric actuator. The surfaces are made of carbide, brass, and zirconia with the same profiles as a saw-tooth. The velocity and position of micro-parts are time-dependently measured by the particle tracking velocimetry (PTV) method where the Canny edge detection technique is used. In the present experiment, 2012-type micro-parts whose dimensions are 2.0 × 1.2 × 0.6 mm3 in length, width, and depth, respectively, are employed. The mass of each micro-part is 7.5 mg. Using a high-speed camera, the tracked longitudinal displacement resolution is found to be about 0.01 mm, which is small in comparison with the length of each micro-part. The obtained results show that unidirectional motion can be attained by the present feeder system. For the same oscillating frequencies and amplitudes applied to the sawtooth surfaces, the motion behavior of micro-parts varies for different experiments and surfaces. This implies that the motion of micro-parts is affected by uncertain causes. However, the probability distribution of the micro-parts’ velocity can be approached by a Gaussian distribution.
Normalisation of Test Results in Air Screw Compressor Measurements as a Basis for Performance Estimation of Refrigeration and Process Gas Compressors
Authors: Stosic Nikola
Published: August 2012

Common use of screw compressors is in compression of air. However, application of screw compressors in refrigeration and air conditioning, as well as in process gas compression is increasing rapidly in recent years. The existing experimental data basis for air compressors may conveniently serve as a source for performance estimation of these compressors. A procedure was derived in this work to find scale factors which connect compressors operating with different fluids and it was applied for performance estimation of refrigeration and process gas screw compressors on the basis of measurements obtained for air compressors. Refprop 8 by NIST was used for calculation of thermodynamic properties of real fluids and ideal gas relation was used for air.
Electrothermal Pumping With Thin Film Resistive Heaters
Authors: Sunding Jacob , Williams Stuart J.
Published: August 2012

The ability to manipulate small amounts of fluid is important for a variety of lab-on-a-chip applications. Electrokinetic microfluidic actuation methods, such as electrothermal pumping, are popular due to their simple implementation and reliability from no moving parts. Electrothermal motion in aqueous solutions results from the electric field acting upon dielectric inhomogeneities in the liquid induced by temperature gradients. The most traditional method of inducing temperature gradients is through direct Joule heating of the fluid itself, which is a function of the electrical conductivity of the liquid. In this case, the microelectrode geometry controls both the location of the Joule heating and the nature of the electric field. Therefore, it is impossible to independently control temperature and electric field with a single set of electrodes. A novel electrothermal microfluidic pump is demonstrated herein. The distinguishing feature of this electrothermal pump is an independent heating source using resistive heating of microfabricated metal traces. A second set of electrodes for electrothermal pumping have been layered on top of the electrically isolated heating elements. An arrangement of coplanar electrode strips with an additional resistive heating electrode was used to demonstrate electrothermal pumping. Fluid motion results were compared to established theory.
Nanofluidics of Mammalian Hearing
Authors: Smith Sonya T. , Chadwick Richard
Published: August 2012

The inner hair cell stereocilia bundle performs the role of transducer in mammalian hearing. Acoustic stimuli deflect the hair bundle to open ion channels, resulting in cation influx and the subsequent release of a neurotransmitter at the base of the cell. Hypotheses for this transduction include fluid shear-driven motion between the tectorial membrane and the reticular lamina to deflect the bundle. It is presumed that ‘molecular gates’ sense tension in tip-links that connect adjacent stepped rows of stereocilia to open the channels. However, almost nothing is known about the endolymphatic flow in the micron-sized gap surrounding the bundle and the nanoscale sized gaps between individual stereocilia rows and between individual bundles. Here we show with nanometer resolution, how each row of stereocilia, their associated tip links and gates and the corresponding flow patterns move in response to acoustical input.
A Numerical Study of Unsteady Laminar Flow and Heat Transfer Through an Array of Rotating Rectangular Microchannels
Authors: Roy Pratanu , Anand N. K. , Banerjee Debjyoti
Published: August 2012

Centrifugal microfluidics plays an important role for enabling many novel applications in life sciences. By controlling the rotating frequency, fluids can be handled and controlled without any actual pumps, actuators or active valves, resulting in cost effective and miniaturized techniques for fluid transport, valving, metering, switching, splitting and separation of fluids. In order to get a vivid picture of the underlying physics of centrifugal microfluidics, we have modeled and simulated fluid flow and heat transfer for water flowing through an array of rotating rectangular microchannels. A finite volume technique based on semi implicit pressure based equation (SIMPLE) algorithm has been developed to solve the Naiver-Stokes equations for unsteady laminar flow. The energy equation has been solved by applying repeated thermal boundary conditions at the wall in cross stream direction. The simulations show significant deviation of velocity and temperature profiles for rotating flow than those of non-rotating case. The results are presented for different flow Reynolds number and rotational Reynolds number.
Model-Based Passivity Control for Teleoperation of Robots With Force Display
Authors: Li Hongbing , Kawashima Kenji , Tadano Kotaro , Fofana Mustapha S.
Published: August 2012

Time delay is a long standing impediment of bilateral control and can destabilize the system evidently. We have already proposed a model-based approach for bilateral control of master-slave robot using time-domain passivity control. This method consists of a virtual slave environment model on the master side and the slave feedback force is modified. However, the chattering phenomena of force can be observed when the model based approach is activated or inactivated. In this paper, the viscosity of the master manipulator is modified according to the output of passivity observer rather than slave feedback force. The energy of the system is discussed using the proposed method and experiments about hard and soft environment contact have been carried out for verification of the proposed approach.
Radial, Two-Phase Heat Transport Device Driven by Electrohydrodynamic Conduction Pumping
Authors: Pearson Matthew R. , Seyed-Yagoobi Jamal
Published: August 2012

Electrohydrodynamic (EHD) conduction pumping can be readily used to pump a thin film of a dielectric liquid along a surface, using electrodes that are embedded into the surface. This effect has been demonstrated under adiabatic conditions and has also been used to create a two-phase heat transport device that is similar to a heat pipe, but with the wicking structure replaced by an EHD conduction pump. In this study, a circular two-phase heat transport device is created. The device features circular electrodes that are arranged concentrically on the bottom surface and that pump a liquid film towards a heat source located at the center of the device. This heat source evaporates the liquid, and a large annular condenser at the periphery of the bottom surface provides a continuous supply of fresh liquid. This radial pumping configuration provides several advantages. Most notably, the heat source is wetted with fresh liquid from all 360 degrees, thereby reducing the amount of distance that must be travelled compared to a linear device. Consequently, the heat flux that can be removed from the central heat source far exceeds the normal critical heat flux of the working fluid. Electrodes are embedded in the condenser, adiabatic, and evaporator sections to maximize the amount of pumping head that can be generated and thereby maximize the heat flux removal.
Study on Nitridation of Silicon Added With Amorphous Silicon Nitride
Authors: Li Yanhui , Wang Li , Yin Shaowu , Yang Fuming , Liu Chuanping , Tong Lige , Wu Ping
Published: August 2012

The direct nitridation process of silicon added with amorphous silicon nitride powder at atmospheric pressure was investigated and the product was analyzed by XRD and SEM. Based on the relationship between the conversion ratio of silicon and the reaction time at different temperatures, a physical and mathematical model was derived to describe the nitridation process of silicon particles. The results showed that the conversion ratio of silicon increased rapidly at the early stage of reaction. And the reaction would be accelerated by reducing the size of silicon particle and increasing the pressure of N2. At the range of experimental temperature, the conversion ratio of silicon increases with improving temperature.
Investigation of a Cell Mechanosensing System by Measuring Cytoskeletal Deformation and Intracellular Calcium Ion Concentration
Authors: Shiraishi Toshihiko , Sakata Kazuhiro , Morishita Shin , Takeuchi Ryohei
Published: August 2012

This paper describes a method to investigate the relationship between cytoskeletal deformation by mechanical stimulation and its corresponding intracellular signals for identifying mechanosensors of cells. Gene transfection of green fluorescent protein to osteoblasts enabled visualization of actin in cells. When local deformation was applied to a cell by a micropipette, the distribution of cytoskeletal actin deformation in the whole cell was automatically obtained from the two images of the cell before and after deformation by using KLT method. Calcium ion signaling response to the same mechanical stimulation was measured as the spatial and temporal changes of fluorescent intensity of fluo-4 loaded to osteoblasts. As a result, we obtained the relationship between the deformation and the biochemical signals in cells.
Investigation of Mechanism of Proliferation Promotion of Cultured Osteoblasts by Mechanical Vibration
Authors: Shiraishi Toshihiko , Ohashi Kazutaka , Morishita Shin , Takeuchi Ryohei
Published: August 2012

This paper describes effects of mechanical vibration on osteoblasts. Their cell proliferation was investigated when sinusoidal inertia force was applied to the cells. After the cells were cultured in culture plates in a CO2 incubator for one day and adhered on the cultured plane, vibration group of the culture plates was set on an aluminum plate attached to a exciter and cultured under sinusoidal excitation of 0.5 G and 12.5 Hz for 24 hours a day in another incubator separated from non-vibration group during 21 days of culture. The time evolution of cell density was obtained by counting the number of cells with a hemocytometer. The phase contrast microscopic images and the cross-sectional confocal microscopic images of cells were captured under an inverted microscope system. As a result, it is found that the mechanical vibration elongated the pseudopods of cells to enhance their mobility resulting in promoting multilayer of the cells.
Reduced Order Model of MEMS Sensors Near Natural Frequency
Authors: Caruntu Dumitru I. , Solis Silva Jose C.
Published: August 2012

The nonlinear response of an electrostatically actuated cantilever beam microresonator sensor for mass detection is investigated. The excitation is near the natural frequency. A first order fringe correction of the electrostatic force, viscous damping, and Casimir effect are included in the model. The dynamics of the resonator is investigated using the Reduced Order Model (ROM) method, based on Galerkin procedure. Steady-state motions are found. Numerical results for uniform microresonators with mass deposition and without are reported.
Exploring the Water/Energy Nexus: Developing a Unified Approach to Water and Energy Issues in California
Authors: Rojas Michael J. , Vrsalovich John P.
Published: August 2012

Metropolitan Water District (Metropolitan) is a public agency charged with providing its service area with adequate and sufficient supplies of high quality water. Metropolitan was incorporated in 1928 by an Act of the California Legislature to serve its 13 original founding Member Agencies. Today, Metropolitan provides water to 26 cities and water agencies serving more than 19 million people in six counties in Southern California. On average Metropolitan delivers 1.7 billion gallons of water per day. California, the third-largest state in the U.S. by land area, has a diverse geography including foggy coastal areas, alpine mountain ranges, hot and arid deserts, and a fertile central valley. California is also the most populous state, exceeding 37 million people in 2010. California’s large population drives the interlinked demands for water and energy in the state. The water-energy nexus in California is highlighted by the fact that two-thirds of the population resides in Southern California while two-thirds of the state’s precipitation occurs in Northern California. Separating Southern California from the rest of the state is a series of east-west trending mountain ranges. Water conveyance projects have been constructed to address this north-south water imbalance and to also import supplies from the Colorado River, hundreds of miles east of Southern California population centers. The movement of water on this scale requires significant energy resources. The California Energy Commission (CEC) estimates that water-related energy use consumes 19% of the state’s electricity and 30% of its natural gas usage every year, and demand is growing. Energy management is a critical concern to Metropolitan and other California water agencies. These issues drive water and energy leaders to jointly manage energy and water use to ensure long-term mutual benefits.
Enhancing Flow Boiling Heat Transfer in Microchannels Using Monolithically-Coated Silicon Nanowires
Authors: Li Dan , Wu Gensheng , Wang Wei , Wang Yunda , Yang Ronggui
Published: August 2012

Flow boiling in microchannels has been attractive for cooling of high power electronics. However, the flow instability hinders the heat transfer performance such as the premature initiation of the critical heat flux (CHF) and could result in device burnout. Numerous methods have been implemented to suppress the instability of flow boiling, including integrating micro pin fins in the channels [1] and inlet restrictors [2], as well as fabricating microchannels with variable cross-sectional areas [3]. Recently, Li et al [4] and Chen et al [5] explored the pool boiling enhancement using nanowires, which shows much more uniform bubble generation and a higher heat transfer coefficient and critical heat flux compared to plain surfaces. The work presented here is the very first effort to explor the impacts of nanowire coating on the flow boiling performance in parallel microchannels. We present here a monolithic integration process to fabricate silicon micro-channels coated with silicon nanowires and the flow boiling characterization of the microchannels. By comparing the flow boiling curves in the microchannels with and without nanowire coating, we show significant performance enhancement for a nanowire-coated microchannel, such as earlier ONB (onset of nucleate boiling), delayed OFO (onset of flow oscillation), enhanced HTC (heat transfer coefficient) and suppressed flow instability.
Large-Scale Deposition of Graphene With Dielectrophoresis
Authors: Li Pengfei , Lei Nan , Xu Jie , Xue Wei
Published: August 2012

Graphene research has attracted enormous attention in the past few years. The handling of graphene sheets, however, has become one of the major bottlenecks in this field, especially in the development of practical devices. Here we report the investigation of large-scale deposition of graphene sheets with dielectrophoresis, a simple electrical approach using alternating current (AC) signals. For comparison purposes, we also perform the deposition of semiconducting single-walled carbon nanotubes (s-SWNTs) with the same technique. Images from scanning electron microscopy (SEM) show that the graphene flakes are successfully deposited over the “teeth”-shaped electrodes. However, the graphene deposition has a lower yield compared with the s-SWNT deposition. Both the graphene and s-SWNT based devices are subject to water rinsing after the deposition process. The current-voltage (I-V) plots before and after the rinsing steps for both devices demonstrate that the surfactants wrapping the nanomaterials can be removed by the running de-ionized water; and better electrical contacts can be formed at the interfaces of nanomaterials and electrodes. In order to further study the electrical characteristics of the deposited graphene and s-SWNTs, a standard Ag/AgCl electrode is introduced to both devices, serving as a top liquidgate terminal. The output characteristics of both devices exhibit p-type field-effect transistor behavior. The s-SWNT based device possesses better field-effect characteristics, whereas the graphene based device has higher conductivity and more apparent metallic properties. The reported research presents an effective approach in large-scale deposition of graphene and it has great potential of paving the way for future graphene-related research and applications, especially in nanoelectronics and sensors.