bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Control of Underwater Pan/Tilt Camera Tracking System: Geometry Modeling and Tracking Control
Authors: Ji Yingfeng , Perez Ronald A. , Amano Ryoichi S.
Published: July 2010

Biologists study on the biological behavior of various marine creatures in situ using underwater observation systems. The darkness in an underwater environment is always one of the most difficult problems to overcome in order to clearly monitor the life cycle of underwater creatures. This illumination would be solved employing the Master-Slave (camera-light platform) coordination tracking structure. The control of underwater platform is a challenging issue due to the complex external forces in the underwater environment. Comparing of tracking control between linear proportional-derivative (PD) and nonlinear PD for the Pan/Tilt camera platform were conducted. The variable structure control (VSC), i.e., sliding mode control (SMC), was employed to the tracking control of the underwater Pan/Tilt camera platform. The disadvantage of SMC is that the discontinuous control signal would excite the high frequency unmodeled dynamic which produces the chattering. One of the methods which eliminate the chattering is to use the boundary layer (BL). However, the width of BL can introduce a trade off between the tracking performance and chattering elimination. Large width of BL can much more eliminate the chattering, but lead to less accurate control results versa. A simple, easily implemented method to vary the width of BL according to the value of tracking error is illustrated and verified in this paper.
Geometric Optimization of Concentrating Solar Collectors Using Monte Carlo Simulation
Authors: Marston A. J. , Daun K. J. , Collins M. R.
Published: July 2010

This paper presents an optimization methodology for designing linear concentrating solar collectors. The proposed algorithm makes intelligent design updates to the collector surface geometry according to specialized numerical algorithms. The process is much more efficient than traditional “trial-and-error” methods, producing a final solution that is near-optimal. A Monte Carlo technique is used to quantify the performance of the collector design in terms of an objective function, which is then minimized using a modified Kiefer-Wolfowitz algorithm that uses sample size and step size controls. The methodology is applied to the design of a linear parabolic concentrating collector, successfully arriving at the known optimal solution.
Flow Characterization of a Three-Dimensional Separated Annular Diffuser
Authors: Dunn Jason J. , Ricklick Mark , Kapat J. S.
Published: July 2010

Experiments were performed on two annular diffusers to characterize the flow separation along the outer wall. Both diffusers had the same fully developed inlet flow condition, however, the expansion of the two diffusers differed such that one diffuser replicated a typical compressor discharge diffuser found in a real machine while the other would create a natural separated flow along the outer wall. Both diffusers were tested at two Reynolds numbers, 5×104 and 1×105, with and without a vertical wall downstream of the exit to replicate the dump diffuser that re-directs the flow from the compressor outlet to the combustor. It was shown that the separation happens quite quickly within the diffuser after which the pressure recovery remains fairly constant. The results also further validate claims that CFD models can not accurately predict flows with high adverse pressure gradients.
An Aerodynamic Study and Design Methodology for the 2009 Supermileage Body
Authors: Pathak Joy , Sobiesiak Andrzej
Published: July 2010

Computational Fluid Dynamics (CFD) has gained recognition as a valuable simulation tool for many industrial applications, creating immense opportunities for introducing CFD into standard undergraduate curriculum. This paper is focused on an extensive aerodynamic CFD study related to the 2009 Supermileage Vehicle. Supermileage Competition is a trademark competition conducted by the Society of Automotive Engineers (SAE). This paper provides an aid for future undergraduate students and young researchers interested in designing low drag vehicles. The major part of this study includes airfoil selections and three dimensional CFD iterations to optimize the body design. The methodology focuses on an inside-out approach to optimization of body shape through computation of aerodynamic forces on a low mass vehicle. The 2008 Supermileage car, after four design iterations, had a drag coefficient of 0.16. The 2009 body, in its final full body design, has a drag coefficient equal to 0.12, which is the lowest drag coefficient ever calculated for a University of Windsor Supermileage car. Due to the current economic state and reduced funding, an additional low budget vehicle was also designed and extensive aerodynamic studies were conducted to validate the design. The new low budget design includes a scoop at the leading edge of the vehicle and the CFD model included a driver model for accuracy. After several design iterations the low budget design yielded a drag coefficient of 0.14. Due to the weight savings, conforming to SAE rules, and considering the current economic conditions, the low budget design was finalized for the 2009 Supermileage Vehicle.
Effect on Slates by Wind Over Roof of Japanese Residence
Authors: Okamoto Satoru
Published: July 2010

A series of wind tunnel tests was conducted on the vibration and scattering behavior of full-sized model of roof tiles, which were used widely for roofings of Japanese wooden dwellings. This study has investigated the nature and source of the vibrating and scattering behavior of roof tiles with the aim of providing a better insight to the mechanism. The roof tiles were set up on the pitched roof in the downstream of the flow from the wind tunnel. The vibrations for the roof tiles were measured by the Laser Doppler Vibrometry and the accelerometer, and the practical natural frequencies of the roof tiles were analyzed by the impulse force hammer test method. The motions of the vibration and scattering were observed by the high-speed video camera. Based on the consideration on the results of the measurements, there is a basic mechanism which can lead to flow-induced vibrations of the roof tiles. This mechanism is similar to that of the so-called fluttering instability, which appears as the self-excited oscillation in the natural mode of the structure at the certain critical flow speed. The values of the frequencies for the oscillating relate to the values of natural frequencies of the vibration.
Rheology of Selected Honeys
Authors: Ashrafi Nariman
Published: July 2010

In this study, rheological properties of five honey samples (Acacia, Citrus Blossom, Fynbos, Bluegum and Raw) were measured. Steady shear and dynamic rheological tests confirmed almost Newtonian behavior for all samples examined over the temperature range of 0–60° C. The water contents of honeys were between 15% and 23%. Fitting of the data in the temperature experiment, showed that primarily expected Arrhenius model is not the best model. Excluding the Raw honey that was possible to be fitted to the said model, the other honey samples were best fitted to a Hyperbolic Tangent model. For the fitted Raw honey however, the activation energy was evaluated to be 95783 J/kg mole. While some rather exceptional viscoelastic properties were observed for the samples, the thixotropic effects were virtually nonexistent. These findings can provide insight into the microstructural, physiological and sensory changes. Also, the study completes a series of studies on rheology of honeys conducted worldwide.
Effects of Temperature on Rheology of Olive Oils
Authors: Ashrafi Nariman
Published: July 2010

In this study, the rheological properties of different samples of olive oils, from the same producer were obtained in a wide range of temperature. At constant temperatures, the shear rate was also varied to obtain heating effects. It was found that all the samples reach a minimum viscosity in the temperature range of 120°C–150°C before thickening to higher viscosities. The viscosity remained almost unchanged in high shear rates regardless of temperature, indicating no shear thinning effects. No thixotropic effects were observed for the olive oils. These findings can provide insight into the microstructural, physiological and sensory changes at frying (high) temperatures.
Computational Analysis of a High-Lift and Low Reynolds Number Airfoil at Turbulent Atmospheric Conditions
Authors: Islam Mazharul , Amin M. Ruhul , Shariff Yasir M.
Published: July 2010

Selection of airfoil is crucial for better aerodynamic performance and design of aerodynamic applications such as wind turbine and aircrafts. In this paper, a high-lift and low-Reynolds number airfoil has been selected and investigated through computational analysis for applying it for small-sized wind turbines as blades. The S1223 airfoil, designed by the University of Illinois at Urbana-Champaign, was chosen for its high-lift characteristics at low Reynolds number typically encountered by the small wind turbines. CFD work is performed with S1223 airfoil profile over a wide range of conditions of interest to analyze the performance of the airfoil using the Spalart-Allmaras turbulence model. The results obtained from the simulation works have been compared with experimental data for validation purpose. It has been found that the Spalart-Allmaras model conforms well with the experimental results, though the values of lift coefficients (Cl) are slightly less than the experimental results. In the present analysis, velocity distributions are analyzed at different angle of attacks for different turbulence intensities. It has been observed that there is vortex shedding around the trailing edge of the airfoil for both turbulence levels. It has been observed in the present study that due to increase in turbulence intensity, both the maximum lift coefficient and the stall angle increases significantly. It has been found after investigating the effect of turbulence intensity over lift-to-drag coefficient ratio that it drastically decreases due to increase in turbulence intensity up to certain value (about 3.5%), then it starts decreasing in gradual manner.
Design of a Cyclic Robot for the Lower Limb
Authors: DeJong Brian P. , Colgate J. Edward , Peshkin Michael A.
Published: July 2010

This paper presents the design and simulation of a novel lower-limb exercise robot designed specifically for cyclic motions and the high power nature of lower-limb interaction. In doing so, it breaks from traditional robotics wisdom by intentionally traveling through singularities and incorporating large inertia. Such attributes help define the understudied class of lower-limb exercise robots, and lead to some explicit design considerations. Results from a simulation show that the specific design requires only a reasonably sized damper and motor.
Investigation of a Novel Process for Wet Milling a Pharmaceutical Tablet in a Dynamically Rotating Water-Filled Dosage Cup
Authors: Balawajder Peter , Steward Jeffrey , Ortega Alfonso , D’Silva Joe , Moore Anne , Silva Luis
Published: July 2010

The most common commercial pharmaceutical dosage forms are tablets and capsules, but unfortunately these forms may not be suitable for sub-groups, such as very ill children and elderly patients and those experiencing trauma and involved in surgery. Many of these patients have difficulty in swallowing a solid dosage form. For these groups, the general practice is to use equipment such as the age-old mortar and pestle to pulverize the tablet, transfer the powder to a container and then make a liquid suspension by addition of water. This process consists of two unit processes: dry grinding followed by creation of a water suspension. This paper reports on the evaluation of a novel wet milling method for performing these unit operations in a single water-filled dosage cup. The basic concept is that the partially water-filled cup is rotated or spun about its axis to produce relative motion between the tablet and the cup surfaces. The cup surfaces are textured so that material is abraded from the tablet when it strikes the cup walls. The complex water motion assists in “softening” the tablet, abrading particulates from its surface, and producing a fine aqueous suspension. Experimental investigations were performed on two concepts. The first method utilized intermittent single axis cup rotation to produce relative motion between the tablet and cup surfaces. The second concept involved rotating the spinning cup on a rotating arm and also about its own axis. The centrifugal force of the arm rotation pressed the tablet against the spinning cup wall, thereby increasing the shearing force. The efficiency of both methods was investigated analytically and experimentally. The effects of rotation rates, intermittent duty cycles, and water fill volumes were examined and compared.
Investigation on Flow Patterns and Transition Characteristics in a Tube-Bundle Channel
Authors: Lu Guangyao , Zhao Guisheng , Ren Junsheng , Xiang Wenyuan , Ai Huaning
Published: July 2010

Tube-bundle channels have been widely used in condenser-evaporator and other industrial heat-exchange equipments. The characteristics of two-phase flow patterns and their transitions for refrigerant R-113 through a vertical tube-bundle channel are experimentally investigated using high-speed camera. Experiments show that there are four main flow patterns in the tube-bundle channel, which are bubbly flow, bubbly-churn flow, churn flow and annular flow. And in the same cross-section of tube-bundle channels, it is shown that there might be different flow patterns in different sub-channels. The flow pattern transitions exhibit unsynchronized in different sub-channels. On the basis of experimental research, the flow pattern map is drawn and analyses are made on the comparison of differences between boiling flow patterns in circular tubes and those in tube-bundle channels.
Analysis of Machining Disturbance and Development of a Support System for the Finishing Process
Authors: Sakito Daiki , Yasuda Yasushi , Osada Tsuginobu , Yano Ken’ichi
Published: July 2010

In this paper we address the development of a finish machining support system that can operate without machining mistakes for the limited production of diversified products. The machining is supported by a haptic device. One challenge is that it is necessary to separate the force sensor output that exists in the operation force from the machining influence force. We propose a control method to remove the influence of the rotation tool disturbance force from the operation force by using adaptive modeling, which estimates the force of rotation tool friction torque in the tangential direction of the machining side from the contact force in the normal direction of the machining side. The effectiveness of this research is shown by a machining experiment.
Identification of Optimal Architecture for Efficient Simple-Cycle Gas Turbine Engines
Authors: Ramakrishnan Sankaran , Teh Kwee-Yan , Edwards Christopher F.
Published: July 2010

Increasing efficiency of gas turbine engines by way of irreversibility minimization has been the underlying objective in the development of a variety of simple, regenerative, and combined cycles. The approach thus far has been to conceptualize new cycles, or choose existing cycles, perform exergy analyses, and make modifications to minimize irreversibility. In this paper we take a fundamentally different approach by developing a thermodynamic framework that defines the principles governing the minimization of irreversibility and uses these principles to deduce an optimal architecture for simple-cycle gas turbine engines. No engine cycle/design is assumed in the beginning. The benefit of this approach is two-fold. First, it explains the factors affecting irreversibility in gas turbine engines. Second, it defines an optimal architecture for simple-cycle engines based on the chosen constraints (e.g., polytropic efficiency of compression and expansion processes, blade temperature limits, etc.) having an efficiency greater than any preconceived cycle/architecture with the same constraints.
A Nonlinear Signal Analysis Scheme for Localization of a Moving Acoustic Source
Authors: Xiros Nikolaos I.
Published: July 2010

The synthesis of coupled systems including linear propagation media and nonlinear lumped subsystems is investigated. The resulting coupled system is expected to exhibit improved dynamic behavior. Such improvements are sought after by designing exclusively the lumped nonlinear subsystem and not by modifying the propagation medium. The lumped subsystem can be static or dynamic as well as passive or active. The design method is based on the Volterra-Wiener theory of nonlinear systems combined with the Linear Fractional Transformation employed for the analysis of uncertain linear systems. Although the techniques are applicable to a variety of practical engineering and physical systems, this work addresses acoustic source localization. Indeed, a moving acoustic source can be considered to nonlinearly modify the characteristics of a carrier acoustic wave. Such an acoustic carrier might be a monochromatic or polychromatic tone as well as other broadband signals such as band-limited white or colored noise. The sound source position signal is propagated through a nonlinear operator and then, under noise-free environment assumptions, determines the sound pressure level at the receiver location. In this paper, the proposed method is applied to the simplified case of a one-dimensional acoustic cavity defined by totally reflective barriers. Furthermore, the lossless wave equation is assumed to govern the sound pressure level in the homogeneous domain of interest. However, even in this simple scenario, only the additional assumptions of negligible source velocity and acceleration allow the derivation of an expression for the sound pressure level containing exclusively source displacement. In this context, simulation data series or analytical solutions, approximate or exact, are post-processed in order to determine the Volterra kernels, which effectively are a convenient extension of the impulse response concept in the nonlinear case, of the operator connecting source displacement to sound pressure level at the receiver. The outcome is Linear Time Invariant models depicting the dominant sound propagation dynamics. Then the synthesis stage is based on the properties of interconnected nonlinear systems that are described in the Volterra-Wiener framework. By using such properties, the signal processing algorithm for the estimation of the acoustic source position based on the received sound pressure level is finally developed.
Dynamics-Based Design of a Soft Robot
Authors: McHugh Steven E. , Saunders Frank J. , Rife Jason H.
Published: July 2010

This paper develops a methodology for converting the results of coarse dynamic simulations into fully realized designs. In particular, we demonstrate how to convert a caterpillar-like soft-bodied robot from a lumped-parameter form into a CAD model that could be easily manufactured. To simplify this design problem, we propose a decomposition method involving three steps. The first step groups the elements of the lumped model into segments. This segmentation simplifies the second step, where rough CAD models are automatically synthesized for each segment from the union of many prisms. In the third step, a human designer combines and smoothes these segment models to create a full-body CAD model. This approach simplifies the development of a high degree-of-freedom soft robot by guiding the designer to a final model with an almost fully automated process.
Heat Transfer From Protuberances and Simulated Ice Accretion Roughness Elements
Authors: Mart Steven R. , McClain Stephen T.
Published: July 2010

The heat transfer phenomena occurring during the initial phases of in-flight ice formation and accumulation on aircraft surfaces are not completely understood. The aim of this investigation was to quantify the local apparent heat transfer enhancement on surface roughness elements intended to mimic the early stages of ice accretion. In order to achieve this objective, a new technique for mounting gold-deposition Mylar film in a gold-side down orientation was developed and tested. Gold deposited Mylar film is commonly used to establish a constant heat flux convective boundary condition for wind-tunnel test surfaces. However, the accepted mounting technique causes problems if the films are used to explore convective heat transfer from surfaces with high thermal conductivity protuberances and surface roughness. To overcome the problems with roughness-element attachment, a new technique for mounting gold-deposition Mylar film in a gold-side down orientation was developed and tested. After validating the new mounting procedure, a large test plate was created following the same technique and was mounted in a wind tunnel. Using infrared thermometry to acquire temperature profiles of a gold Mylar heated flat plat prepared with three hemi-spherical roughness elements of varying thermal conductivity, the apparent enhancement of the elements was evaluated for varying tunnel velocities. Flow characteristics at and behind the roughness elements were also examined using the infrared images. This study presents the results of the new Mylar film mounting procedure and the apparent enhancement and flow results.
Dynamic Characteristics Analysis of Hybrid Photovoltaic/Thermal (PV/T) Solar Energy System
Authors: Cui Wenzhi , Liao Quan , Li Longjian , Yu Songqiang
Published: July 2010

A dynamic model is developed to analysis the transient characteristics of hybrid photovoltaic/thermal solar energy system. Two typical climatic conditions, clear day and hazy day, are considered in the present study. The daily and annual variation of hot water temperature, electrical output, thermal efficiency and electrical efficiency are calculated and analyzed. The results show that the solar irradiance is the critical factor that affects the variation of the water temperature, electrical output and electrical efficiency of the PV/T system. The thermal efficiency of the system has also a certain relation to the daily fluctuation of solar radiation.
Towards Meso and Macro Scale Energy Harvesting of Vibration
Authors: Tang Xiudong , Zuo Lei
Published: July 2010

The ambient environment is full of energy of different forms such as sun light, wind, heat, hydraulic energy, and mechanical motion including vibration. People have been seeking ways to convert the ambient energy into useful forms since ancient time. With the global concern of energy and environmental issue, energy harvesting provides one attractive solution and becomes a new research frontier. However, the majority of current research on energy harvesting from mechanical vibration obtains 10μW to 100mW energy, which has only limited applications like self-powered wireless sensors. More than ten review articles appeared in the past five years on vibration energy harvesting, whereas, the majority of which focuses on the applications in microelectronics and wireless sensors. The objective of this review is to survey the research and applications of meso and marco scale energy harvesting from vibration, and discuss the particular challenges and future research directions. Topics include piezoelectric materials and electromagnetic transducers, relevant motion and magnification mechanisms, and power electronics and control, with applications on energy harvesting from human motions, vehicle suspensions and civil structures.
Calibration of Rugged, Renewable and Fast Response Temperature Probes in a Hypersonic Flow Facility
Authors: Mohammed H. , Salleh H. , Yusoff M. Z.
Published: July 2010

This paper presents a dynamic calibration technique of rugged, renewable and fast response temperature probes (TP) in a hypersonic testing facility. Two types of scratch were used, mainly abrasive papers with different grit sizes and scalpel blades with different thicknesses to form the probe junction. The effect of scratch technique on probe’s thermal product is investigated. The probes were tested and calibrated in the test section and in the end wall of UNITEN shock tube facility at different axial and radial locations. It was observed that the thermal product of a particular TP depends on the Mach number, surface junction scratch technique, junction location as well as on the enthalpy conditions. It was also noticed that using scalpel blade technique with a particular blade size gives consistent thermal product values. Thus, it does not require an individual calibration. However, for TP whose junction created using abrasive paper technique with different grit sizes, a calibration for each TP is likely to be needed. The results from shock tube tests have shown that, these probes have a response time on the order of microseconds (50 μs) with a rise time less than (0.5 μs), and were suitable for making the heat transfer measurements in highly transient conditions.
Imperfection Sensitivity of Compressed Circular Cylindrical Shells Under Periodic Axial Loads
Authors: Pellicano Francesco
Published: July 2010

In the present paper the dynamic stability of circular cylindrical shells is investigated; the combined effect of compressive static and periodic axial loads is considered. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration; Lagrange equations are used to reduce the nonlinear partial differential equations to a set of ordinary differential equations. The dynamic stability is investigated using direct numerical simulation and a dichotomic algorithm to find the instability boundaries as the excitation frequency is varied; the effect of geometric imperfections is investigated in detail. The accuracy of the approach is checked by means of comparisons with the literature.
Quasi-2D Monte Carlo Simulations of Phase Transitions and Internal Aggregate Structures in a Highly Dense Suspension Composed of Magnetic Plate-Like Particles
Authors: Sakuda Yasuhiro , Satoh Akira
Published: July 2010

We have investigated phase transitions and internal aggregate structures of a highly dense suspension composed of magnetic plate-like particles with a magnetic moment normal to the particle axis, by means of the Monte Carlo method. In the present study, we have considered a quasi-2D system in order to clarify the influences of volumetric fraction of particles and magnetic field strength on particle aggregations and phase transitions. Internal structures of particle aggregates have been discussed quantitatively in terms of pair correlation and orientational pair correlation functions. The main results obtained here are summarised as follows. When the influence of magnetic interactions between particles is of the same order of the magnetic field strength, the particles form column-like clusters, and the internal structure of a suspension shows solid-like structures. For the case of strong applied magnetic field, the internal structure is transformed from solid-like structures into isotropic ones. However, as the volumetric fraction increases, the particles form brick wall-like structures under circumstances of a strong applied magnetic field, and the internal structure exhibits solid-like ones.
Experimental Study of Gas Cooler in Trans-Critical CO2 Refrigeration System
Authors: Xie Yingbai , Liu Yingfu , Tang Jiancheng , Sun Ganglei
Published: July 2010

In this paper, the gas cooler in trans-critical CO2 refrigeration cycle system is studied experimentally. Research shows that: the temperature different between the inlet CO2 and the cooling water changes in a wide range as the heat rejection pressure changes, but the outlet CO2 temperature of the gas cooler is almost unchanged; the relative pressure drop is only about 1% when the heat rejection pressure is 9MPa in the system; with the increase of gas cooler exit temperature, the refrigerating capacity decreases linearly first, and the latter becoming more and more stable, but the compression work is linearly increased; on the experimental conditions, the COP decreased about 25% when the outlet temperature of the gas cooler ranged from 30°C to 37°C.
Anode Gas and Steam Recycling for Internal Methane Reforming SOFCs: Analysis of Carbon Deposition
Authors: Eveloy Vale´rie
Published: July 2010

The development of solid oxide fuel cell (SOFCs) systems capable of direct internal reforming (DIR) of methane and higher hydrocarbons is being actively pursued. However, a major challenge with current state-of-the-art nickel-based anodes is their propensity to form deteriorous carbon deposits in DIR, unless excess steam is introduced in the fuel. Reduced fuel humidification levels are desirable from the viewpoints of cell performance, reliability and plant economics. This study explores the use of anodic fuel and steam recycling schemes as possible mitigation strategies against carbon deposits at fuel steam-to-carbon (S:C) ratios less than unity. Using a detailed computational fluid dynamics (CFD) model which couples momentum, heat, mass and charge transport with electrochemical and chemical reactions, the operation of a an internal reforming SOFC and spatial extent of carbon deposition within the anode are analyzed based on a thermodynamic analysis accounting for both the cracking and Boudouard reactions, for several fuel humidification and recycling conditions. 50% (mass %) fuel recycling is shown to be an effective mitigation strategy against carbon deposition at inlet xH2O/xCH4 ratios of 0.5 to 1, with only a minor portion of the cell inlet region affected by coking. For lower recycling ratios at the same fuel compositions, fuel recycling reduces the risk of coking, but does not eliminate it. For the SOFC configuration studied, at a S:C of 0.5, steam recycling is found to reduce the extent of carbon deposits by a magnitude comparable to that obtained using fuel recycling, providing that steam recycling ratios on order 25% higher than the fuel recycling ratios are applied. Steam recycling may therefore be considered advantageous, in terms of reduced overall mass flow. For a S:C = 0.5, the mitigating effect of steam recycling on the susceptibility to coking is through the directions of the cracking and Boudouard reactions, while fuel recycling has a positive impact on the cracking reaction only. The anodic gas recycling strategies considered could help extend the operational range of DIR-SOFCs to lower fuel humidification levels than typically considered, with reduced thermal stresses and risks of carbon deposits, while reducing system cost and complexity in terms of steam production.
Transient Thermal Analysis of Electrical Machine
Authors: Sleiti Ahmad K.
Published: July 2010

Transient thermal analysis of electric machine under realistic operation conditions and thermal losses is studied. A symmetrical portion of the stator and rotor is modeled and all thermal losses and cooling boundary conditions are applied according to operational duty cycle. It is found that there is a temperature gradient across the stator of more than 30 °C, across the rotor of more than 70 °C and across the whole machine of more than 100 °C. These temperature gradients could cause high thermal stresses and lead to severe reduction in the machine life. It is extremely important in future designs to consider reducing the temperature gradients by optimizing the design of the electric machines through advanced cooling techniques and strategies.
Effects of Natural Adhesive “Nibe” for Drawing Kyoto Bow
Authors: Shibata Kanjuro , Nasu Shinichi , Kume Masashi , Nakai Asami , Hamada Hiroyuki
Published: July 2010

In Kyoto bow fabrication, in order to bond each material, the glue which is made from the skin of the deer (Nibe) has been traditionally used. Recently, the synthetic adhesive is used instead of Nibe. The purpose of this study is to clarify the effects of the type of adhesive on the performance for the archer to draw Kyoto bow (Nibe bow and Synthetic bow). The measurement of motion was performed using MAC 3D system, and in order to clarify the relationships between the deformation and the load required to draw of the Kyoto bow, the motion analysis of the archer during the drawing motion of the Kyoto bows was performed by attaching markers and load cell onto the bows. In addition, the velocity of the arrow was calculated by the image processing. The loads and the maximum velocities of arrow with both bows were similar, however the arrow of Nibe bow drastically accelerates rather than that of Synthetic bow at the some point. Additionally, the time required to draw the bow of Nibe bow was significant shorter than that of Synthetic bow.
Conducting Properties of a Contact Between Open-End Carbon Nanotube and Various Electrodes
Authors: Gao Feng , Qu Jianmin , Yao Matthew
Published: July 2010

The carbon nanotube (CNT) is becoming a promising candidate as electrical interconnects in nanoscale electronics. This paper reports the electronic structure and the electrical conducting properties at the interface between an open-end single wall CNT (SWCNT) and various metal electrodes, such as Al, Au, Cu, and Pd. A simulation cell consisting of an SWCNT with each end connected to the metal electrode was constructed. A voltage bias is prescribed between the left- and right-electrodes to compute the electronic conductance. Due to the electronic structure, the electron density and local density of states (LDOS) are calculated to reveal the interaction behavior at the interfaces. The first-principle quantum mechanical density functional and non-equilibrium Green’s function (NEGF) approaches are adopted to compute the transport coefficient. After that, the voltage-current relation is calculated using the Landauer-Buttiker formalism. The results show that electrons are conducted through the electrode/CNT/electrode two-probe system. The contact electronic resistance is calculated by averaging the values in the low voltage bias regime (0.0–0.1 V), in which the voltage–current relationship is found to be linear. And the electrical contact conductance of electrode/CNT/electrode system show the electrode-type dependent, however, the amplitude for different electrodes is of the same order.
Simulation of Multi-Mode Film Boiling Using Level Set Method
Authors: Gada Vinesh H. , Sharma Atul
Published: July 2010

2D transient multi-mode film boiling simulation of water near critical pressure (p = 0.99pc = 21.9 MPa) on a heated horizontal surface is carried out using an in-house Level Set (LS) method based semi-explicit finite volume method code. The influence of initial vapor film thickness (yo) on the dominant instability mode is evaluated by carrying out simulations on domain having width greater than most dangerous Taylor wavelength i.e. LX = 4λd with y0 = 0.0425λd and 0.125λd at low wall superheat (ΔT = 2K). For lower initial film thickness, the viscous force dominated Rayleigh-Taylor instability is captured and the average bubble spacing is found close to the prediction made using lubrication theory i.e. λP = 2λc = 0.816λd. However, for higher initial film thickness, the inertia force dominated Taylor-Helmholtz mode of instability is found with the average bubble spacing close to λd. Simulations are carried out to check the existence of Rayleigh-Taylor instability on various domain width LX = 2λd, 3λd, 4λd and 6λd at yo = 0.0425λd and ΔT = 2K. The average bubble spacing for all domain widths is found to be less than 2λc indicating that the Rayleigh-Taylor instability is dominant.
Enhancing the Learning of Two-Phase Flow Measurement Techniques in a Modern Mechanical Engineering Program
Authors: Goharzadeh Afshin , Molki Arman , Rodgers Peter , Bojanampati Shrinivas
Published: July 2010

This paper outlines a proposed low-cost experimental setup for the measurement of two-phase liquid-gas flows in a vertical column. The objective of the test facility is to familiarize students with the challenges in applying measurement techniques to characterize such flows. The test facility incorporates two complementary intrusive and non-intrusive measurement techniques for detecting and studying the dynamics of air bubbles transported in water. The intrusive measurement method uses conductivity probes, while the non-intrusive technique is laser based. For both measurement techniques, details of the data acquisition system and the characteristics of sensors employed are presented. In addition, the teaching strategy is discussed for implementing the use of the proposed two-phase flow experimental setup in a Mechanical Engineering curriculum.
Geometrical Effects in Optimal Performance of Energy Dissipation of Pin Fin Heat Sinks
Authors: Zu´n˜iga-Cerroblanco J. L. , Herna´ndez-Guerrero A. , Kowalski G. J. , Rubio-Arana J. C.
Published: July 2010

This work describes the hydraulic and thermal behavior of pin-fin heat sinks when subjected to a constant heat flux with values equivalent to those generated incurrent electronic devices. The fin geometries analyzed are rectangular, circular and elliptical. The experimental analysis is performed for pin-fin in-line arrangement. The heat sink arrangement is also analyzed numerically for pin-fin in-line and staggered arrangements; and the results are compared. The thermal resistance and pressure drop is reported for all arrangements for different air velocities. The experimental and numerical results are compared and validated with recent technical literature. The Entropy Generation Minimization (EGM) is used to obtain an optimization of the heat sink pin fin arrangement. Analytical and empirical correlations for heat transfer coefficients and friction factors are used in the optimization model. This optimization model considers all relevant design parameters for pin-fin heat sinks, including geometric parameters, material properties and flow.
Incompresible Periodically Reversing Flow in a Conical Pipeline of Finite Length
Authors: Luviano-Ortiz J. Luis , Ramos Eduardo , Hernandez-Guerrero Abel , Luna Jose-Manuel
Published: July 2010

A numerical three-dimensional study has been carried out to analyze the hydrodynamic behavior of an incompressible periodically-reversing flow in a conical pipeline of finite length. In order to generate the oscillatory flow, a two pistons-driven pipe flow was established (the pistons were placed at the ends of the pipeline.) In the smaller piston the Womersley number was set to 16 while the axial displacement/diameter ratio was set to 1. The hydrodynamic flow behavior is considered and discussed for the accelerating and decelerating phases of the cycle. The numerical results show the generation of vortices for different penetration lengths. One of the most representative results is that in the position of 183.25°, after the pistons reach their maximum displacement, the flow pattern loses the axial symmetry that had appeared for previous phases of the cycle.
Computational Study of Frequency and Amplitude Effects on Separation Flow Control With the Synthetic Jet
Authors: Okada Koichi , Fujii Kozo , Miyaji Koji
Published: July 2010

In order to investigate the frequency and amplitude effects of the synthetic jet on the flow field, numerical simulation is carried out. Even though the final objective of this study is to understand mechanism of separation control for various objects, streamline and bluff bodies, the configuration of backward-facing step is chosen as the first step because of the simplicity. Three-dimensional Navier-Stokes equations are solved. Implicit large eddy simulation using high-order compact difference scheme is applied. The present analysis is addressed on the frequency characteristics of the synthetic jet for understanding frequency characteristics and flow-filed. Three cases are selected, No-control, F+h = 0.2 and F+h = 2.0, where non-dimensional frequency F+h is normalized with the height of backward-facing step and the free stream velocity. The present computation shows that at F+h = 2.0, separation length is 20 percent shorter than the No-control case. Strong two-dimensional vortices generated from the synthetic jet interact with the shear layer, which results in the increase of the Reynolds stress in the shear layer region. These vortices are deformed into three-dimensional structures, which make Reynolds stress stronger in the recirculation region. At F+h = 2.0, size of the separation length is almost same as the No-control case because the mixing between the synthetic jet and the shear layer is not enhanced. Weak and short periodic vortices induced from the synthetic jet do not interacts with the shear layer very much and diffuse in the recirculation region.
Time Averaged and Fluctuating Heat Transfer Measurements in an Atomising Mist Jet Nozzle
Authors: Lyons Oisn F. P. , Murray Darina B. , Byrne Gerard , Persoons Tim
Published: July 2010

Much is already known about the heat transfer characteristics of impinging air jets, and they are widely used in many engineering applications. There currently exist many correlations describing such characteristics. However, the complex internal structure of many nozzles can lead these to produce results which deviate from those predicted by correlations. One such nozzle is currently used in this research group to produce a water mist flow and this paper describes the experimental characteristics of its single phase behaviour.
Adjustable Tensegrity Robot Based on Assur Graph Principle
Authors: Shai Offer , Tehori Itay , Bronfeld Avner , Slavutin Michael , Ben-Hanan Uri
Published: July 2010

The paper introduces a tensegrity robot consisting of cables and actuators. Although this robot has zero degrees of freedom, it is both mobile, and capable of sustaining massive external loads. This outcome is achieved by constantly maintaining the configuration of the robot at a singular position. The underlying theoretical foundation of this work is originated from the concept of Assur Trusses (also known as Assur Groups), which are long known in the field of kinematics. During the last three years, the latter concept has been reformulated by mathematicians from rigidity theory community, and new theorems and algorithms have been developed. Since the topology of the robot is an Assur Truss, the work reported in the paper relies on Assur Trusses theorems that have been developed this year resulting in an efficient algorithm to constantly keep the robot at the singular position. In order to get an efficient characterization of the desired configurations, known techniques from projective geometry were employed. The main idea of the control system of the device, that was also mathematically proved, is that changing the length of only one element, causes the robot to be at the singular position. Therefore, the system measures the force in only one cable, and its length is modified accordingly by the control system. The topology of the device is an Assur Truss — a 3D triad, but the principles introduced in the paper are applicable to any robot whose topology is an Assur Truss, such as: tetrad, pentad, double triad and so forth. The paper includes several photos of the device and the output data of the control system indicating its promising application.
Numerical Investigation of a Liquid Droplet Impinging on a Heated Surface
Authors: Diaz Andres , Ortega Alfonso , Anderson Ryan
Published: July 2010

Previous studies, most of them experimental, reveal that the cooling effectiveness of a water drop impinging on a heated surface depends on the wall temperature, droplet shape and velocity. All previous studies focus on the behavior of a droplet falling in a quiescent environment, such as still air. Evidence in the literature also shows that gas assisted droplet sprays, in which a gas phase propels the droplets, are more efficient in heat removal than sprays consisting of droplets alone. It is conjectured that this is due to an increase in the maximum droplet spreading diameter upon impact, a thinner film, and consequently an increase in the overall heat transfer coefficient. Recent experiments in the author’s group [1, 2] show that the carrier gas jet strongly influences droplet spreading dynamics by imposing normal and shear forces on the liquid surface. The heat transfer is greatly augmented in the process, compared to a free falling droplet. To date, there has been no fundamental investigation of the physics of gas assisted spray cooling. To begin to understand the complicated process, this paper reports on a fundamental problem of a single liquid droplet that impinges on a heated surface. This paper contributes a numerical investigation of the problem using the volume of fluid (VOF) technique to capture droplet spreading dynamics and heat transfer in a single drop event. The fluid mechanics is investigated and compared to the experimental data. The greatest uncertainty in the simulation is in the specification of the contact angle of the advancing or receding liquid front, and in capturing the onset of the three-dimensional fingering phenomena.
Caster-Camber Relationship in Vehicles
Authors: Jazar Reza N. , Khazaei A. , Mahinfalah M. , Nazari G. H.
Published: July 2010

Lateral force of a tire depends on the sideslip and camber angles. Camber angle is the roll angle of a tire with respect to the road surface and may be a function of the vehicle roll angle. However, the camber angle may also be generated by a steer angle because of suspension and steering mechanisms. A steerable tire turns about a steering axis which can be determined by the caster and lean angles. The steered tire will gain a camber angle because of caster and lean angles. This camber-steering might be in favor or opposite to the direction the vehicle is supposed to turn. A few negative degrees caster angle is required for directional stability. Although the lean angle can be set to be zero, it is usually set to a few degrees positive value to help steering. Therefore, the camber angle of a steerable tire is a function of steering, caster, and lean angles in a nonlinear manner. In this investigation, we employ the screw theory to model the rotation of a tire about the steering axis kinematically. A set of equations will be found to determine the camber angle as a function of caster, lean, and steer angles. Determination of the associated camber trust due to steering would be the application of this study.
Dynamic Analysis to Confirm Lead Failure of a 352-Pin CQFP Under Shock
Authors: Feng Michael , Kwok Peter , Pryputniewicz Dariusz , Marinis Ryan , Pryputniewicz Ryszard
Published: July 2010

During qualification testing of an electronics module, several leads in one corner of a 352 pin ceramic quad flat pack (CQFP) component failed. The module was exposed to several different environments including sine vibration, thermal cycling, random vibration, and shock. The last test environment applied was seven consecutive shocks normal to the printed wiring board. Given the severity of the shock response spectrum, it was believed that the shocks normal to the board were the culprit. Therefore, a finite element model (FEM) was created of the module to diagnose the cause of the failure. The FEM modeled all 352 CQFP leads using quadratic beam elements. Besides the CQFP, the FEM also included the aluminum frame, the printed wiring board, and several adjacent components. It was validated by comparing the board’s mode frequencies and shapes computed in ANSYS to those imaged by optoelectronic holography on the test hardware. ANSYS was also used to rule out sine vibration, random vibration, and thermal cycling as causes of the failure. To evaluate the stress levels in the leads during the shock pulse, the actual acceleration experienced by the hardware during a shock pulse was recorded and used in an explicit dynamic analysis in LS-DYNA. In addition, a bilinear elastic-plastic material model was used for the kovar leads. The analysis showed that the suspect leads reached their ultimate tensile strength by the fourth consecutive shock. These results confirmed that the leads failed due to the consecutive shock pulses. The FEM was subsequently used to evaluate a redesign of the module to mitigate the risk to mechanical shock.