bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Laser Microjoints in Rat Brain
Authors: Mian Ahsan , Sultana Taslema , Newaz Golam
Published: August 2009

The stability of the laser bonded titanium coated glass/polyimide microjoints were studied in-vivo (by implanting on the rat brain surface for 10 days) and were compared with the earlier in-vitro (by soaking in artificial cerebrospinal fluid, CSF at 37°C for one week) data. In the current state, the strength of the joints were measured by a specially designed instrument called “pressure test” equipment where the samples were subjected to a variable pressure load (using high pressure nitrogen) controlled by a pressure regulator. The strength of the joints seems to degrade as a result of soaking in rat brain. The bond degradation in rat brain implants is similar compared to those soaked in CSF solution. Polyimide uptakes water through existing pores in it and also water gets in the joint region through the edges of the samples. Water might have caused oxidation of the chemical bonds which are thought to have formed by the laser fabrication process. Water availability at the joint region in implanted samples is less than that of the CSF soaked samples — which explains the better retention of the joint strength of the vivo samples. The average failure load from pressure test was found to be 1.4 N/mm, which is below the average tensile strength of the joint (7.3 N/mm) as published elsewhere by the authors. The difference between the joint strengths results from the difference in applied mechanical (joint peeling in pressure testing and joint shearing in tensile testing) loads and loading rates by the experiments.
Simulations of Magnetoviscosity of Dilute Suspensions of Magnetic Ellipsoids
Authors: Sa´nchez J. H. , Rinaldi C.
Published: August 2009

We studied the rotational Brownian motion of magnetic triaxial ellipsoidal particles (orthotropic particles) suspended in a Newtonian fluid, in the dilute suspension limit, under applied shear and magnetic fields. The algorithm describing the change in the particle magnetization has been derived from the stochastic angular momentum equation using the fluctuation-dissipation theorem and a quaternion formulation of orientation space. Results are presented for the response of dilute suspensions of ellipsoidal particles to constant magnetic and shear flow fields.
Suspension Kinematics: A Method for Determining Steer Induced Angles and Displacements
Authors: Parsons D. , Jazar G. Nakhaie , Mahinfalah M.
Published: August 2009

The lateral force created by a tire necessary for a vehicle to change direction is generated by slip and camber angles. Camber angle may be defined as the angle between a vertical line passing through a wheels’ center and the horizontal projection of this line onto the wheel. If the axis which the tire turns about is not parallel to the vertical axis, a change in camber will be induced as a result of the change in steer angle. This axis is called the steering axis and can be determined by the caster and lean angles relative to the wheel position in a body coordinate frame. The relation between the steer and camber angles may favor or detract from the lateral force being generated by the tire. This paper describes a method for determining the induced camber angle with respect to steer angle. In this method the wheel is defined throughout the steering range as a circle. The lowest point of the circle with respect to the global coordinate frame may then be defined via a method for determining maxima and minima. This point is then used to determine camber angle with respect to steer angle throughout the steering range. The lowest point of the tire may also be used in finding ride height and body roll due to change in steer angle. A sensitivity analysis reflects the suspension behavior for a variety of different suspension parameters. The relative difference between the induced steer angle about the steering axis and the actual steer angle with respect to the body coordinate frame are relevant in developing more accurate vehicle dynamics models.
An Analytical Solution to the Thermal Stress and Thermal Strain in a Cylindrical Laser Rod With Longitudinal Temperature Rise
Authors: Li Zhigang , Huai Xiulan , Wang Li , Tao Yujia
Published: August 2009

In this paper, a mathematical model of the thermal stress and thermal strain in the laser medium was presented. An analytical solution was further derived for the thermal stress and thermal strain in the laser rod through the method of Thermoelastic Displacement Potential and the method of Love Displacement Function. The analytical solution results show that under the traction free boundary conditions, the longitudinal rise of fluid temperature has little effect on the thermal stress profile in the laser rod. However, the thermal strain field caused by both the temperature and the thermal stress fields has an evident variation in the longitudinal direction, which will affect the laser transmission characteristics and the beam quality.
Effect of Nano-Size Oxide Based Reinforcement on the Tensile Properties of Sn-Ag-Cu Solder
Authors: Nai S. M. L. , Wei J. , Gupta M.
Published: August 2009

In the present study, using powder metallurgy route, varying volume fraction of ZrO2 stabilized with 8 mol.% of Y2O3 particulates were incorporated into Sn-3.5Ag-0.7Cu solder to develop nanocomposite solders. The samples were extruded and characterized in terms of microstructural and tensile properties. With the addition of nano length scale reinforcement, the results revealed an improvement in 0.2% yield strength (upto ∼ 39%) and ultimate tensile strength (upto ∼ 43%), when compared with that of monolithic Sn-Ag-Cu solder. An attempt is made in this study to interrelate the tensile behavior of Sn-Ag-Cu with the presence of nano-size reinforcement.
Theoretical Investigation of the Factors Affecting the Performance of a High Speed DI Diesel Engine Fuelled With Natural Gas
Authors: Papagiannakis Roussos G. , Yfantis Elias A. , Hountalas Dimitrios T. , Zannis Theodoros C.
Published: August 2009

Reduction of exhaust emissions is a major research task in diesel engine development in view of increasing concern regarding environmental protection and stringent exhaust gas regulations. Simultaneous reduction of NOx emissions and particulate matter is quite difficult due to the soot/NOx trade-off and is often accompanied by fuel consumption penalties. Towards this aim, automotive engineers have proposed various solutions, one of which is the use of alternative gaseous fuels as a supplement for the commercial liquid diesel fuel. This type of engine, which operates fuelled simultaneously with conventional diesel oil and gaseous fuel, is called “dual fuel” diesel engine. Among alternative gaseous fuels, natural gas is considered to be quite promising due to its low cost and its higher auto-ignition temperature compared to other gaseous fuels facilitating thus its use on existing diesel engines. Previous research studies revealed that natural gas/diesel engine operation results in deterioration of brake engine efficiency, CO and HC emissions compared to conventional diesel fuel operation. In attempt to curtail these negative effects, various theoretical and experimental studies were carried out examining the influence of various parameters such as pilot fuel quantity, diesel fuel injection timing advance and intake charge conditions on “dual fuel” engine performance characteristics and pollutant emissions. However, there are more to know about the proper combination of these engine parameters to attain the optimum results regarding reduction of CO and HC emissions without further deteriorating, if not improving, brake engine efficiency. Hence, in the present study, a theoretical investigation is conducted using an engine simulation model to examine the effect of the aforementioned parameters on performance and exhaust emissions of a natural gas/diesel engine. Predictions are produced for a high-speed natural gas/diesel engine performance characteristics and NO, CO and Soot emissions at diverse engine speeds and loads using a comprehensive two-zone combustion model. The main objective of this comparative assessment is to elaborate the relative impact of each one of the above mentioned parameters on engine performance characteristics and exhaust emissions. Furthermore, an endeavor is made to determine the optimum combinations of these engine operational parameters. The conclusions of this study may be proven to be considerably valuable for the application of this technology on existing DI diesel engines.
Transient Thermal Response of Skin Tissue
Authors: Pirtini Cetingul Muge , Herman Cila
Published: August 2009

Recent improvements in infrared sensor and computer technology led to the resurgence of the infrared imaging in medicine. The technique has many advantages such as being noninvasive and relatively less expensive than MRI or ultrasound. These imaging techniques are based on the following principle: when a surface is heated or cooled, variations in the thermal properties of a structure result in identifiable temperature contours on it. These contours are characteristic of the structure’s shape, depth, and its thermal properties.
An Emerging O(N) Model and Algorithm for Virtual Prototyping of Dynamics of Molecular Conformation
Authors: Ries Andrew , Duan Shanzhong Shawn
Published: August 2009

Molecular dynamics is effective for nano-scale phenomenon analysis. There are two major computational steps associated with computer simulation of dynamics of molecular conformation and they are the calculation of the interatomic forces and the formation and solution of the equations of motion. Currently, these two computational steps are treated separately, but in this paper an O(N) (order N) procedure is presented for an integration between these computational steps. For computational costs associated with calculating the interatomic forces, an internal coordinate method (ICM) approach is used for determining potentials due to both the bonding and non-bonding interactions. Thus, the potential gradients can be expressed as a combination of the potential in absolute and relative coordinates. For computational costs associated with the formation and solution of the equations of motion for the system, a constraint method that is used in computational multibody dynamics is utilized. This frees some degrees of freedom so that Kane’s method can be applied for the recursive formation and solution of equations of motion for the atomistic molecular system. Because the inclusion of lightly excited high frequency degrees of freedom, such as inter-atomic oscillations and rotation about double bonds would force the use of very small integration step sizes, holonomic constraints are introduced to freeze these “uninteresting” degrees of freedom. By introducing these hard constraints the time scale can be appropriately sized for to provide a less computationally intensive dynamic simulation of molecular conformation. The algorithm developed improves computational speed significantly when compared with any traditional O(N3) procedure.
An Investigation Into the Upper Arm Deformation Under Inflatable Cuff
Authors: Lan H. , Al-Jumaily A. M. , Lowe A.
Published: August 2009

The human upper arm is simulated using a nonlinear geometrical and physical model. To create a more realistic simulation, the geometry of the model is based on the visible human body dataset. The model consists of four parts, humerus, brachial artery, muscle, and other soft tissues. All the materials used in this model are assumed to be incompressible and hyperelastic. The unique properties of each material are specified and described. Incorporating all of these facts, a finite element model is developed using the commercial programme ABAQUS®. The upper arm tissues’ deformations and artery collapse process under compression are simulated in this model. The proposed model has the potential to simulate the tissue deformations under inflatable cuffs exposed to arm movements.
Fuzzy Logic Approach to Wireless Diagnostic Alarms in Anesthesia
Authors: Benjamin D. , Gholam Hosseini H. , Al-Jumaily A. , Harrison M. J.
Published: August 2009

This paper explores the use of a fuzzy logic system to continuously monitor a patient’s vital signs during an operation under anesthesia and evaluate the patient’s physiological state. The proposed systems aims to employ statistical-based alarms, principal component analysis (PCA) together with respiratory associated arterial pressure variation (Pulse Pressure Variation-PPV and Systolic Pressure Variation-SPV) and a new fuzzy logic model to estimate the physiological state of the patient under anesthesia. The fuzzy approach will include the recursive fuzzy inference system (RFIS) which combines the current patient status data with the previous output of the inference system thereby reinforcing the current finding based on previous sequential outputs. In addition to this, work is also aimed at the creation of a wireless module that will provide patient information directly to the system.
Enhancement of Gripping Efficiency of Miniature Gripper Applying Elastic Buckling Phenomenon by Constraining Deformation
Authors: Ando H. , Takami Y. , Muramatsu N.
Published: August 2009

This paper discusses the enhancement of gripping efficiency of a gripping mechanism for miniature grippers. This gripping mechanism employs a displacement enlarging mechanism utilizing an elastic buckling of the flexible gripping fingers. Miniature grippers have been realized by the flexible gripping fingers acting as the displacement enlarging mechanism. However, there is a trade-off relation between the enlarged displacement and gripping force of the gripping mechanism. For this reason, the enhancement of gripping efficiency of the gripping mechanism has been experimentally attempted by constraining an elastic deformation of the flexible gripping fingers. The flexible gripping fingers are largely deformed due to elastic buckling after gripping an object. This elastic deformation is constrained by supports. Experiments have been conducted for some different cases of placement of the supports. The driving force, driving displacement and gripping force of the gripping mechanism have been measured. From experimental results, it has been confirmed that the enhancement of gripping efficiency of the gripping mechanism is feasible by controlling deformation of the flexible fingers passively.
Analysis of Temperature and Plastic Flow During Friction Stir Spot Welding Using Particle Method With Elastic-Plastic Model
Authors: Hirasawa Shigeki , Badarinarayan Harsha , Okamoto Kazutaka , Tomimura Toshio
Published: August 2009

Friction stir spot welding (FSSW) is a new metal-joining process, and a numerical simulation code to calculate optimal welding conditions is desired. In this paper, we analyzed temperature distribution and plastic flow during FSSW process by solving the elastic-plastic deformation equations using the particle method. Calculation results indicate that, temperature distribution is circler patterns and the temperature below the rotation tool is 300 °C at 0.7 s when the diameter of the tool is 8 mm and the rotation speed is 2500 rpm. The material of the metal plate near the outside of the tool protrudes to cause the burr. The calculation result is similar to our experimental result. Plastic flow pattern of material in the metal plate is obtained. The obtained complex flow pattern is important to mix metal material and the weld strength of FSSW. The length of the pin of the tool, the tool diameter, the tool rotation speed, and the tool plunge speed are important parameters for mixing of metal material. The mixing of metal material below the concave shoulder is strong.
Numerical Procedure for Assessment of Centrifugal Pump Cavitation Erosion
Authors: Timushev Sergey F. , Knyazev Vladimir A. , Panaiotti Sergey S. , Soldatov Vladimir A. , Rohatgi Upendra Singh
Published: August 2009

Currently the cavitation erosion damage becomes a critical issue that limits the centrifugal pump life cycle extension. Despite of a long history of studying the cavitation erosion phenomenon in centrifugal pumps there are still no reliable assessment methods except semi-empirical formula having rather limited application and accuracy. The paper is presenting a novel method for assessment of centrifugal pump cavitation erosion combining 3D unsteady flow CFD modeling and numerical analysis of cavitation bubbles behavior. The Navier-Stokes equations are solved by a splitting method with the implicit algorithm and high-order numerical scheme for convective transfer terms. The 3D numerical procedure is based on non-staggered Cartesian grid with adaptive local refinement and a sub-grid geometry resolution method for description of curvilinear complex boundaries like blade surfaces. Rotation is accounted with implementation of “sliding-grid” technology. The method considers evolution of the bubble in 3D flow from initial conditions until the disruption moment with determination of the erosion jet power impact. Validation of the method on model feed centrifugal pump stages is completed for two model centrifugal impellers Centrifugal impeller #1 is designed with a goal of through-passed shaft pump flow modeling. There are completed computations of cavitating bubbles’ evolution under non-uniform pressure field that show the non-uniform pressure distribution near the blade surface causes an essential influence on cavitation erosion. Computational prediction of the impeller #1 cavitation erosion damage is confirmed experimentally.
Optimization of a Coal-Fired Furnace for Oxy Fuel Combustion
Authors: Saravanan V. , Jayanti Sreenivas , Seetharamu Subramanyam
Published: August 2009

Oxy-fuel combustion, in which a conventional hydrocarbon fuel is burned in presence of oxygen diluted with carbon dioxide (called henceforth as oxy-fuel), is an emerging technology that accommodates CO2 sequestration while offering the prospect of low emissions. Dilution by CO2 (from flue gas recirculation) prevents high peak temperatures thereby reducing material damage, high NOx formation etc. Studies [1] reveal that CO2-diluted flames are unstable as compared to N2-diluted flames and that a higher molar fraction of oxygen, 30% by volume, is necessary to ensure stable combustion. Nevertheless, as the heat transfer properties of CO2/O2–70:30 mixtures are different to that of normal air, the flow profiles and heat flux distributions might vary within the furnace. While considering the retrofit of existing normal air operated coal fired furnaces with oxy-fuel mode, it is imperative to investigate these flow variations in detail. In the present study, Computational Fluid Dynamics (CFD) based simulations have been done for a typical 210 MW Indian pulverized coal fired furnace under normal air combustion and under oxy-fuel combustion (CO2/O2-70:30 volume %) mode and the results in terms of CO2 concentration, temperature distribution, velocity of flue gas, particle trajectories and devolatilisation characteristics have been compared.
Dynamic Anti-Plane Behaviors of Interacting Circular Cavities in an Infinite Piezoelectric Medium
Authors: Song Tianshu , Li Dong , Sun Lili
Published: August 2009

In this article, dynamic interaction is investigated theoretically between several circular cavities in an infinite piezoelectric medium under time-harmonic incident anti-plane shear wave load. The theoretical formulations are based upon the use of complex variable and multi-coordinates. Dynamic stress concentration factors at the edges of the circular cavities are obtained by solving boundary value problems with the method of orthogonal function expansion. As examples, some calculating results of two interacting circular cavities in an infinite piezoelectric medium are plotted to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the structural geometries influence on the dynamic stress concentration factors.
MYMOSA: Towards the Simulation of Realistic Motorcycle Manoeuvres by Coupling Multibody and Control Techniques
Authors: Moreno Giner David , Brenna Claudio , Symeonidis Ioannis , Kavadarlic Gueven
Published: August 2009

Multibody dynamics simulation technology can provide a great help to understand and analyze motorcycle dynamics. In fact, its application in this field has grown very fast in the last years. However, apart from the mathematical model of the vehicle, a virtual rider is essential in order to properly simulate a motorcycle. This is due to the unstable nature of two-wheeled vehicles, which makes them very difficult to simulate by using open-loop maneuvers. The problem of developing a virtual rider for motorcycles has already been covered in literature but most of the proposed control algorithms achieved their purpose without considering the physiological limits of the rider. The objective of the research activities presented here are the preliminary development of a realistic virtual rider based on an experimental campaign and its subsequent simulation together with a detailed multibody model of a motorcycle. Special emphasis was put on making the rider model as simple as possible to facilitate the posterior design of the controller. Real rider movements were measured under laboratory conditions by means of the Motion Analysis technique. Several volunteers with different riding experiences, gender and anthropometry were involved in the experiments in order to provide a valid dataset for the analysis. For the present research, the virtual rider controls the direction of the motorcycle by means of both a torque on the handlebars and the movement of his body. The upper part of the rider’s body was modeled as an inverted pendulum. With regard to the longitudinal dynamics, the motorcycle is controlled by means of the brake torques and by the engine torque, which is transmitted to the rear wheel by means of a simplified model of the chain. First results of the developed virtual rider are presented at the end of this paper.
Tracking Physiological Fatigue in Prolonged Load Carriage Walking Using Phase Space Warping and Smooth Orthogonal Decomposition
Authors: Segala David B. , Chelidze David , Adams Albert , Schiffman Jeffrey M. , Hasselquist Leif
Published: August 2009

The ability to track and predict the onset of physiologic fatigue using easily measurable variables is of great importance to both civilian and military activities. In this paper, biomechanical gait variables are used to reconstruct fatigue evolution in subjects walking with a 40 kg load on a level treadmill for two hours. Fatigue is reconstructed in two steps: (1) phase space warping based feature vectors are estimated from gait variable time series; and (2) smooth orthogonal decomposition is used to extract fatigue related trends from these features. These results are verified using independently obtained measures of fatigue from breath-by-breath oxygen consumption (V˙O2) and surface electromyography (EMG) from a set of leg muscles. V˙O2 based measures for some subjects show no discernable trends. However, for a subject showing monotonically increasing oxygen consumption, the reconstructed dominant fatigue variable closely track V˙O2 measure reflecting global systemic fatigue. For the muscles showing variation in EMG-based fatigue measures, the reconstructed fatigue variables also closely track these local muscle trends. The results show that kinematic angles, which are easier quantities to measure in the field, can be used to track and predict the onset of fatigue.
Development of a Low-Cost, Rapid-Cycle Hot Embossing System for Microscale Parts
Authors: Hale Melinda , Hardt David E.
Published: August 2009

Hot embossing is an effective technology for reproducing micro-scale features in polymeric materials, especially micron scale patterning. The equipment used for hot embossing to date is often research oriented, (intended to be flexible and provide a wide range of processing conditions), and a dedicated equipment industry has yet to develop. This paper details a hot embossing machine design strategy suitable for large-scale manufacturing. The design is motivated by capital cost reduction, right-size machine design, system simplicity, and production flexibility and scalability. Toward this end, a minimal number of components were used, commercially available off-the-shelf components were chosen where possible, system layout was designed to be modular, and system size was scaled for the intended products (in this case microfluidic devices). Innovative design aspects include the use of new ceramic substrate heaters for electrical heating, choice of a moveable heat sink to minimize heat load during the heating cycle, and the careful design of the thermal elements to minimize cycle time. The capital cost and the cost per part produced with this machine are estimated to be an order of magnitude less than currently available options. This design has a minimum cycle time of two minutes, and replicates microstructures within a 25mm by 75mm area.
A Control-Oriented Model of Hydrostatic Transmission With Application on Torque Vectoring Differential Modeling
Authors: Deur Josˇko , Ivanovic´ Vladimir , Petric´ Josˇko , Hancock Matthew , Assadian Francis
Published: August 2009

The paper presents a control-oriented model of a closed circuit hydrostatic transmission. The model includes the pump speed, motor speed, and pressure difference state variables, and nonlinear static maps for the flow loss resistance and pump and motor torque losses. The model maps are obtained by experimental identification conducted on a hydrostatic transmission setup. The model is validated against the experimental data for a wide range of operating conditions. The validated model is used for bond graph modeling and analysis of a hydrostatic transmission-based torque vectoring differential. The torque vectoring features are illustrated by computer simulation.
PIV Measurements in the Wake of a Cactus Shaped Cylinder
Authors: Karaki W. , Abboud J. , Daher N. , Osman M. , Oweis G.
Published: August 2009

The flow field past a cylindrical model with a cactus-shaped cross section is investigated in a wind tunnel. The velocity field in the immediate wake just aft of the cylinder and the surface pressure distribution are measured. The data from the cactus model are compared to a similar model with a circular section. The mean flow patterns have generally a similar form for the two geometries. However, there are differences in the surface pressure distribution and the turbulent velocity levels in the wake.
Focusing of Proteins in a Horseshoe Microchannel
Authors: Shim Jaesool , Dutta Prashanta , Ivory Cornelius F.
Published: August 2009

Ampholyte based isoelectric focusing (IEF) simulation was conducted to study dispersion of proteins in a horseshoe microchannel. Four model proteins (pls = 6.49, 7.1, 7.93 and 8.6) are focused in a 1 cm long horseshoe channel under an electric field of 300 V/cm. The pH gradient is formed in the presence of 25 biprotic carrier ampholytes (ΔpK = 3.0) within a pH range of 6 to 9. The proteins are focused at 380 sec in a nominal electric field of 300 V/cm. Our numerical results show that the band dispersions of a protein are large during the marching stage, but the dispersions are significantly reduced when the double peaks start to merge. This rearrangement of spreading band is very unique compared to linear electrokinetic phenomena (capillary electrophoresis, zone electrophoresis or electroosmosis) and is independent of channel position and channel shape. Hence, one can perform IEF in complex geometries without incorporating hyperturns.
Invariant Manifold Detection From Phase Space Trajectories
Authors: Kuehl Joseph , Chelidze David
Published: August 2009

Invariant manifolds provide important information about the structure of flows. When basins of attraction are present, the stable invariant manifold serves as the boundary between these basins. Thus, in experimental applications such as vibrations problems, knowledge of these manifolds is essential to understanding the evolution of phase space trajectories. Most existing methods for identifying invariant manifolds of a flow rely on knowledge of the flow field. However, in experimental applications only knowledge of phase space trajectories is available. We provide modifications to several existing invariant manifold detection methods which enables them to deal with trajectory only data, as well as introduce a new method based on the concept of phase space warping. The method of Stochastic Interrogation applied to the damped, driven Duffing equation is used to generate our data set. The result is a set of trajectory data which randomly populates a phase space. Manifolds are detected from this data set using several different methods. First is a variation on manifold “growing,” and is based on distance of closest approach to a hyperbolic trajectory with “saddle like behavior.” Second, three stretching based schemes are considered. One considers the divergence of trajectory pairs, another quantifies the deformation of a nearest neighbor cloud, and the last uses flow fields calculated from the trajectory data. Finally, the new phase space warping method is introduced. This method takes advantage of the shifting (warping) experienced by a phase space as the parameters of the system are slightly varied. This results in a shift of the invariant manifolds. The region spanned by this shift, provides a means to identify the invariant manifolds. Results show that this method gives superior detection and is robust with respect to the amount of data.
Flow Inside Microchannels With Liquid-Walls
Authors: Malik Tarun , Fang Nicholas X.
Published: August 2009

We demonstrate the ability to create ‘liquid-walls’ in hydrophilic microfluidic channels, without the need for hydrophobic patterning. This is achieved by stopping the liquid using sudden expansion in cross-section perpendicular to the flow direction. Further, these walls can be switched off dynamically either manually or by using simple microfluidic logic. The maximum break pressure for these walls is determined by the surface free energy of the liquid, the advancing contact angle of the liquid on substrate and the channel geometry. This system can be used in liquid-gas chemical reactors, passive microfluidic valves, microfluidic pressure switches and in eliminating air entrapment issues.
Thermal and Electrical Transport in Carbon Nanofiber Interconnects
Authors: Saito Tsutomu , Kitsuki Hirohiko , Suzuki Makoto , Yamada Toshishige , Fabris Drazen , Yang Cary Y.
Published: August 2009

We study reliability of carbon nanofibers (CNFs) under high-current stress by examining CNF breakdown on four different configurations, suspended or supported, with/without tungsten deposition. The suspended results are consistently explained with a heat transport model taking into account Joule heating and heat dissipation along the CNF, while supported cases show a consistently larger current density just before breakdown, reflecting effective heat dissipation to the substrate.
Development of a Passive Cooling Panel for Residential Buildings, Integrated Into a Novel “Magnetic/PCM” Ground Coupled Flat Heat Pipe
Authors: Gutierrez Gustavo , Aponte Josean
Published: August 2009

New perspectives for reducing heat and electricity consumption in building are emerging with innovative techniques such as highly insulating glazing and super insulated structures, utilization of solar energy, solar cells, hybrid ventilation solutions, energy efficient and demand-controlled ventilation, as well as integration of solutions, energy production in building. A relatively new innovation is the use of ground-source heat pumps that have become popular for both residential and commercial heating and cooling applications because of their higher energy efficiency compared to conventional systems. In this study, a flat heat pipe is proposed for using the enormous heat capacity of the soil as a heat sink to remove heat from the ambient, integrated the principal idea of a linear reluctance motor for the recirculation of the working fluid. Linear oscillating motors have a long history as rotary motors; but the complexity in the design and difficulties on their control limited the use of them. The motor consists of an iron bar, moving inside a coil. During the path of the iron bar an incremental force appears opposing the movement of the bar. For that reason, it is important to control the system and take advantage of that behavior. Reluctance motors can have high power density at a low cost, making them ideal for many applications. In this study, an implementation of the reluctance motor is proposed for using in a recirculation process of a passive cooling panel for residential buildings. Parametric studies are carried out to optimize the design parameters.
Comparison Between Time-Frequency Techniques to Predict Ball Bearing Faults in Drives Executing Arbitrary Motion Profiles
Authors: Cocconcelli Marco , Secchi Cristian , Rubini Riccardo , Fantuzzi Cesare , Bassi Luca
Published: August 2009

In this paper Wavelet Transform (WT) and Hilbert-Huang Transform (HHT) are used as bearing diagnostics tools in drives executing arbitrary motion profiles. This field is increasingly drawing the attention of the industries because the modern electric motors work as electric cams inducing the shaft to move with a cyclic variable-velocity profile. The literature papers take into account only a constant velocity profile and they are not suitable for such applications. In fact literature methods analyse the signal only in the frequency domain, while in variable-velocity condition the bearing diagnostics should be performed in time domain. Both WT and HHT are time-frequency techniques which describe an input signal as a sum of specific functions. These functions are compared with a signal which simulates the expected vibrations of a bearing with a given fault, e.g. on the outer race. The comparison is done through a cross-correlation between the expected signal and the time-frequency techniques output. WT and HHT are used separately in an industrial case, which consists in bearing fault prediction in an automated packaging machine. In the end of the paper the WT and HHT results are discussed to analyse the different responses.
Phase Averaged Velocity Fields for Bluff Bodies Using a PIV System
Authors: Koc Ilteris , Britcher Colin P. , Yalcin Sinan Eren
Published: August 2009

Two phase-averaging methods are presented for the investigation of periodic flows. First, an implementation of an angular triggering technique, the Predictive Angular Triggering Technique (PATT), uses the flow frequency and phase information to predict a future trigger point to record for PIV images. Second, the Tracking Triggering Technique (TTT) uses the detection of the PIV laser signal’s pulse occurrence, then tags each PIV image with the angular position at its measurement time, allowing grouping into angular slots or bins. These two methods have been applied first on a spinning plate where the physical location of the plate could be measured. Results proved that the phase averaging system worked effectively. Later a circular cylinder at Re 105000 is used to observe the wake vortex structure. Here, the phase information was derived from flow measurements, specifically a hot wire in the wake. Evolution of the classical vortex street for the cylinder was successfully observed.
Fabrication and Applications of Long-Range Ordered Au Nanodisk Arrays
Authors: Zheng Yue Bing , Juluri Bala Krishna , Huang Tony Jun
Published: August 2009

Large-scale nanostructure arrays with spatial coherence are useful for many applications. Conventional nanofabrication techniques such as electron beam lithography and focused ion beam lithography are expensive and time-consuming. In this paper, long-range ordered Au nanodisk arrays were fabricated on glass substrates using nanosphere lithography (NSL) combined with reactive ion etching (RIE) techniques. The morphology and size distribution of the Au nanodisks were examined with scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sensitivity of the localized surface plasmon resonance (LSPR) of the Au nanodisk arrays to change in the surroundings’ refractive index was evaluated by integrating the Au nanodisk arrays into microfluidic channels. The measured sensitivity was supported by discrete dipole approximation (DDA) calculations. Further, we designed and fabricated an all-optical plasmonic switch based on the Au nanodisk arrays and photoresponsive liquid crystals (LCs). The high-quality optical properties and high-degree spatial uniformity of the nanodisk arrays, together with simple, low-cost fabrication and easy integration with microfluidic system, suggest tremendous potential in using these nanostructures in many other applications, including biosensing and imaging, surface-enhanced Raman spectroscopy (SERS), and plasmonic tweezers.
Turbulent Flow in a Channel Containing a Moving Saturated Permeable Medium
Authors: de Lemos Marcelo J. S.
Published: August 2009

Moving beds are present in a number of engineering equipment. Their analyses contribute to improvement of many energy and material production processes. Here, transport equations for flow in a moving bed reactor are presented. Such device is modeled as a saturated porous matrix with a steady speed. Transport equations are time-and-volume averaged and additional form and viscous drags, due to the porous structure, are assumed to be a function of the relative velocity between phases. Turbulence equations reflect their dependence on the speed of the solid substrate. Results show the decay of turbulent kinetic energy levels as the solid speed approaches the speed of the moving fluid.
Comparison of Two-Dimensional Models for Predicting Turbulent Combustion in Inert Porous Media
Authors: de Lemos Marcelo J. S.
Published: August 2009

The objective of this paper is to simulate turbulent flow and heat transfer in industrial porous burners. Transport equations are written in their time-and-volume-averaged form and a volume-based statistical turbulence model is applied to simulate the intra-porous turbulence generation. Combustion is modeled via a simple closure. Preliminary testing results indicate that a substantially different flow pattern is obtained depending on the model used. In addition, for high inlet flow rates or high excess air, the flame front moves towards the exit of the chamber.
Laminar Channel Flow With Hydrodynamic Slip
Authors: Parthasarathy Ramkumar N. , Ranganathan Kapil , Lam Vu
Published: August 2009

A theoretical and experimental investigation of slip flow over an ultrahydrophobic surface in a rectangular cross-sectional channel was conducted. The experiments consisted of the flow of water over a LOTUS-paint coated surface in a rectangular channel. The tests included flows at three different Reynolds numbers, Re = 129.6, Re = 103.6, Re = 69.1. Velocity measurements were made using a Laser Doppler Velocimeter (LDV). Velocity measurements for the no-slip conditions were also made for a flow rate of Re = 129.6 and compared with the slip profile. An uncoated surface was used for these measurements. The velocity profile and the flow rate for fully-developed channel flow were derived as a function of the slip length and slip velocity. The experimental data was used to determine the slip velocities and slip lengths for different Reynolds numbers from the theoretical equation. These quantities, used in the theoretical equation generated the necessary theoretical profiles for comparison with experiments. The slip velocities and slip lengths were evaluated by considering two locations, y = h and y = h/3. The profiles drawn from the theoretical equation evaluated from the slip velocities and lengths using the locations y = h and y = h/3 compared reasonably well with the experimental measurements. The volumetric flow rates computed theoretically using the slip lengths and slip velocities also compared well with the experimental values. The measurements highlight the effects of slip on one surface of the channel.
Switch-Mode Continuously Variable Transmission With Flywheel Energy Storage
Authors: Forbes Tyler D. , Van de Ven James D.
Published: August 2009

A hybrid drive train significantly improves energy efficiency of ground vehicles. While numerous auxiliary hybrid power sources have been researched, few are capable of the energy and power density of a flywheel coupled with a continuously variable mechanical transmission. The primary challenge of a flywheel hybrid system is a transmission capable of coupling a high speed flywheel to the drive train of the vehicle. A novel solution to this challenge is a switch-mode continuously variable transmission that utilizes a rapidly switching clutch to transmit power. This system, the mechanical analog of a DC-DC boost converter circuit, utilizes a flywheel, a high frequency clutch, an anti-reversing ratchet, and a spring to vary the output torque. The switch-mode continuously variable transmission is demonstrated through an idealized finite difference model, created from the dynamic system of equations. The model is used to demonstrate the system behavior in a passenger car subjected to road loads in various conditions. The output of the model demonstrates pulses in the output torque as a result of the rapidly switching clutch. This output ripple in is smoothed to an acceptable level by the torsion spring. From this preliminary analysis the on-off continuously variable transmission offers an efficient, energy dense, and power dense hybrid vehicle drive train alternative.
Experimental Investigation of a Hydromechanical Scale Model of the Gerbil Cochlea
Authors: Liu Shuangqin , Gauthier Douglas A. , Mandelup Ethan , White Robert D.
Published: August 2009

In this research, an uncoiled scale gerbil cochlea is designed and fabricated. The cochlea model is an uncoiled, 16 times scale model of the real gerbil cochlea and has only one duct. Both the basilar membrane width and the duct size vary along the length of the device, in analogy to the physiology. The cochlea duct is filled with silicone oil and driven by a modal exciter (shaker) at different frequencies. The movement of the basilar membrane is measured using laser vibrometry at different locations along the basilar membrane. The ratio of the basilar membrane velocity to drive velocity is computed and plotted. The characteristic frequency of the model varies from 7000 Hz at 2 cm from the base of the cochlea to 350 Hz at the 15 cm from the base. Two different viscosities silicone oil, 20 cSt and 500 cSt are used for the basilar membrane movement measurements. A WKB method is applied to the calculation of the basilar membrane movement of the scale cochlea model, in which the fluid motion is fully three dimensional.
Design and Evaluation of a Modulator Circuit for a Self-Energized Wireless Sensor
Authors: Fan Zhaoyan , Gao Robert X. , Kazmer David O.
Published: August 2009

This paper presents the design, simulation, and experimental verification of an electronic modulator circuit, which is a critical functional component for an acoustic wireless sensor that can simultaneously measure temperature and pressure within an injection mold. Through a stack of piezoceramic rings, the sensor is powered by energy harvested from the mold pressure differential. Based on the concept of nonlinear network theory, the amount of energy for pressure and temperature modulation is quantitatively defined by calculating the current and voltage thresholds of the modulator circuit. Results from the analytical model have shown that by optimizing the parameters of the circuit, the sensor can be properly powered by energy harvested from the molding process for data acquisition and transmission. The simulation result was then experimentally verified using a prototyped circuit. Pressure measurement resolution of 0.12% of the full scale (100 MPa) and temperature sensitivity of 4.8 kHz/°C were obtained from the experiments.
Dynamic Lumbar Tracking With Occupational Whole-Body Vibration Exposure
Authors: Channamallu Raghu Ram , Jorgensen Michael J. , Wilson Sara E.
Published: August 2009

Low back pain is one of the most costly and common musculoskeletal disorders, affecting up to 80% of the adults in their lifetime [1]. Whole body vibration (WBV) has been found to be a major risk factor in the etiology of low back pain with WBV increasing low back disorder risk from 1.2 to 39.5 fold depending on the occupational exposure duration and magnitude [2–3]. Recent research has demonstrated that exposure to sinusoidal whole body vibration of 5 Hz leads to increased propriceptive errors and delayed neuromotor response to external perturbation [4]. These results suggest a potential mechanism for low back injuries, namely that vibration may alter neuromotor control leading to poor stabilization and control of low back motion, increasing the risk of injury. However, the methods used to assess these changes in proprioception are static measures, require a good deal of equipment and setup time, and have a high variance, particularly with removal of electrodes and sensors, that make them impractical for the industrial setting. In addition, previous studies have only examined the effect of pure sinusoidal vibration exposure rather than the mixture of frequencies seen in occupational settings. Therefore, the goal of this project was to develop a dynamic measure of lumbar sensory accuracy and neuromotor control that could be used easily in the workplace and to examine the effects of WBV vibration on the measure using an occupationally-relevant vibration exposure.
Temperature-Insensitive Miniaturized Fiber Inline Fabry-Perot Interferometer Fabricated by Femtosecond Laser
Authors: Han Yukun , Lin Cheng-Hsiang , Tsai Hai-Lung , Wei Tao , Xiao Hai
Published: August 2009

This article presents a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step femtosecond (fs) laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90°C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1×10−6 RIU/°C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing.