bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Control Algorithms for Semi-Active Suspension Systems Based on a Full Vehicle Model
Authors: Ajaj M. A. , Sharaf A. M. , Hegazy S. A. , Hossamel-deen Y. H.
Published: August 2012

This paper presents a comprehensive investigation of automotive semi-active suspension control algorithms and compares their characteristics in terms of ride comfort and tire-road holding ability. Particular attention has been paid to the semi-active suspension systems fitted with a shock absorber of dual damping characteristics. Different mathematical models are presented to investigate the ride response considering both simplified and complex vehicle models. Numerical simulation has been carried out through the MATLAB/SIMULINK environment which aids the future development of controllable suspension systems to improve vehicle ride comfort. The results show a considerable improvement of the vehicle ride response using different schemes of semi-active suspension system in particular the modified groundhook control algorithm.
Link Between Function-Flow Failure Rates and Failure Modes for Early Design Stage Reliability Analysis
Authors: O’Halloran Bryan M. , Stone Robert B. , Tumer Irem Y.
Published: August 2012

This scope of this paper is to provide an extension to the Function Failure Design Method (FFDM). We first implement a more robust knowledge base using Failure Mode/Mechanism Distributions 1997 (FMD-97). Then failure rates from Nonelectric Parts Reliability Data (NPRD-95) are added to more effectively determine the likelihood that a failure mode will occur. The proposed Functional Failure Rate Design Method (FFRDM) uses functional inputs to effectively offer recommendations to mitigate failure modes that have a high likelihood of occurrence. This work uses a past example where FFDM and Failure Modes and Effects Analysis (FMEA) were compared to show that improvements have been made. A four step process is presented to show how the FFRDM is used during conceptual design.
The Rate (Time)–Dependent Mechanical Behavior of the PMR-15 Thermoset Polymer at Temperatures in the 274–316 °C Range: Experiments and Modeling
Authors: Ryther C. E. C. , Ruggles-Wrenn M. B.
Published: August 2012

The inelastic deformation behavior of the PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at temperatures in the 274–316 °C range. The experimental program was designed to explore the influence of strain rate on monotonic loading at various temperatures. In addition, the effects of prior strain rate on relaxation response and on creep behavior following strain controlled loading were examined at temperatures in the range of interest. Positive, nonlinear strain rate sensitivity is observed in monotonic loading at all temperatures investigated. Both relaxation behavior and creep are profoundly influenced by prior strain rate at all temperatures. The time-dependent mechanical behavior of the PMR-15 polymer is also strongly affected by temperature. The elastic modulus decreases and the departure from quasi-linear behavior is accelerated with increasing temperature. Stress levels in the region of inelastic flow decrease as the temperature increases. The relaxation behavior as well as the creep response is strongly influenced by temperature. The viscoplasticity theory based on overstress (VBO) is augmented to model the effects of temperature on the inelastic deformation behavior of PMR-15. VBO is a unified state variable theory with growth laws for three state variables: the equilibrium stress, the kinematic stress and the isotropic stress. Based on experimental findings several VBO model parameters are developed as functions of temperature. The augmented model is employed to predict the response of the material under both strain- and stress-controlled loading histories at temperatures in the range of interest. Comparison with experimental data demonstrates that the augmented VBO successfully predicts the inelastic deformation behavior of PMR-15 polymer under various loading histories at temperatures between 274 and 316 °C.
Risk Acceptance Criteria Formulation in Furniture Industry: The Portuguese Reality
Authors: Rodrigues Matilde A. , Arezes Pedro , Lea˜o Celina P.
Published: August 2012

The acceptance criteria are important to the decision on the risk, however, it is possible to recognize that there is a lack of guidelines to use in the acceptance criteria definition. Considering that previous publications concerning the acceptance criteria definition in the occupational area are scarce, this paper aims to analyze how risk acceptance criteria can be formulated, exemplifying with a specific case in a Portuguese furniture industry. It explores the problematic on the acceptance criteria and the used principles for its formulation. The metrics to be adopted were also analyzed. Faced with the lack of guidelines for the risk acceptance criteria formulation for traditional occupational accidents, the experience with major accident hazards may help to understand some features. The principle ALARP was seen as an interest approach to use in occupational accidents. The literature review allowed finding seven steps for the quantitative acceptance criteria formulation. These steps were applied on a small Portuguese furniture industry. The case study showed that the quantitative acceptance criteria formulation is not an easy process. The principle ALARP it was considered suitable to be applied. Regarding risk indexes or indicators, the LTI-rate was the one that was considered to be the more appropriate. The upper risk acceptance limits, defined for this company, were 0.450 and 0.225 for tolerability and acceptability, respectively. The manager and consultant considered the use for the quantitative acceptance criteria as an added value to support the risk decisions. This paper showed the importance of the risk acceptance criteria in risk decisions, and exemplified how that can be done. However, this work suggests that there is still much work to be done in this area, in order to get that the companies of this sector being able to define the acceptance criteria in an equity perspective. So, it is only the first step, needing to be continued and extended to other industries.
Clay Dispersion Effects on Excimer Laser Ablation of Polymer-Clay Nanocomposites
Authors: Chang I-Ta , Sancaktar Erol
Published: August 2012

The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this paper. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration.
Void Inspection in Lead-Free Solder Bumps on Ball Grid Array (BGA) Packages Using Laser Ultrasound Technique
Authors: Gong Jie , Ume I. Charles
Published: August 2012

Solder joint voids are usually formed by the entrapped gas bubbles during the reflow process, and are common in all surface mount applications. It is a controversial issue on the reliability of the solder joint, however the consensus is that voiding is acceptable at low contents, while excessive voiding affects mechanical properties, and decreases strength, ductility and fatigue life of the interconnections. X-ray is the most widely used technique to evaluate the voids, including the size and occurrence frequency. In this paper, a laser ultrasound and interferometer inspection system is used to inspect the voids in lead-free solder bumps in ball grid array (BGA) packages. This system uses a pulsed Nd:YAG laser to induce ultrasound in the chip packages in the thermoelastic regime; and laser interferometer is used to measure the transient out-of-plane displacement response of the package surface to the laser irradiation. The quality of solder bumps is evaluated by analyzing the transient responses. In this work, voids were intentionally created by adding the volatile flux during the assembly process. By controlling the volume of flux dip, three different levels of voiding were proposed: void-free, relatively low and relatively high. The presence of voids in the solder bumps was first verified using 2-D X-ray techniques. Meanwhile, the built-in image-processing software in X-ray tool measured the void fraction to quantify the level of voiding. Then the laser ultrasound inspection system was used to evaluate the voids in these samples. By comparing the vibration responses from voided samples and void-free samples, it was found that the laser ultrasound inspection system is capable to differentiate samples with relatively high voiding from void-free samples while the relatively low voiding was below the resolution of the inspection system. Lastly, a further comparison between the void-free and voided solder bumps was carried out by the destructive cross-section technique. The comparisons between these three solder bump evaluation methods will be presented in this paper.
Benefits of Lean Teaching
Authors: Kahlen Franz-Josef , Flumerfelt Shannon , Siribang-Manalang Anna Bella , Alves Anabela
Published: August 2012

Lean Engineering has matured into a credible and useful set of tools and philosophies to satisfy customer demand. Almost all applications of lean have been in commercial settings where increased value can easily be measured by increased sales, less defects and generally a higher output. The authors of this paper report on their experiences of teaching lean engineering to engineering students. The focus is on how these students were enabled to develop problem solving skills, to think in systems and to consider sustainability of their designs or engineering interventions. Further, the authors describe the metrics used to assess student learning, and what were the lessons learned for the course conveners in communicating Lean Principles. The authors will demonstrate that teaching Lean to engineering students enhance their understanding of engineering professional practice.
Temperature Synchronization, Phase Dynamics and Oscillation Death in a Ring of Thermally-Coupled Rooms
Authors: O’Brien Jeffrey , Sen Mihir
Published: August 2012

Synchronization of coupled, self-excited oscillators in complex systems is a common occurance. This report examines the effects of thermal coupling through the walls of a building on temperature oscillations due to hysteretic thermostatic control. The specific case of three rooms is studied. A system of differential equations models the dynamics of each room temperature, accounting for on-off heating, heat loss to the environment, and heat exchange between rooms. Three types of solutions are observed: one in which all room temperatures oscillate in phase, another with the oscillations equidistant in phase, and a third that is time-independent. The existence and linear stability of each solution type is investigated as a function of a parameter k that represents the thermal interaction between neighboring rooms. The in-phase behavior exists and is linearly stable for all k, the out-of-phase oscillations exist in a band of k and are stable in a smaller band, and the time-independent solution exists above a certain k where they are stable.
Effect of Mechanical Pulse Oscillations on Pre-Contracted Porcine Airway Smooth Muscle
Authors: Theodore S. , Al-Jumaily A. M. , Mbikou P.
Published: August 2012

This research focuses on investigating the effect of pulse oscillation rather than sinusoidal oscillation on contracted airway smooth muscle (ASM). Isolated ASM were tested using pulse oscillations with Frequency of 0.5 Hz, 1Hz and 2Hz; Amplitude of 2%, 4%, 6% and 8%, and duration of 1 min, 2 min and 3 min (n = 5). Results obtained from the experiments showed that pulse oscillation with short duration had significant effect on the relaxation of ASM compared to sinusoidal oscillations with longer duration.
Non-Linear Viscoelastic Mechanics of Native and Engineered Ligaments and Tendons
Authors: Ma Jinjin , Arruda Ellen M.
Published: August 2012

Patellar tendon (PT) autografts and allografts are the most common methods currently used to replace a torn anterior cruciate ligament (ACL). The PT is not only much stiffer than the ACL it replaces it also exhibits qualitatively and quantitatively different non-linear viscoelastic behavior from those of the ACL. These mis-matched biomechanics may be contributing to the high incidence of early onset osteoarthritis suffered by patients who have had ACL surgeries. Thus there is a need for an ACL graft that can reproduce normal ligament biomechanics and knee function. This talk examines the inhomogeneous, non-linear viscoelastic response of native ACL and of a tissue engineered ACL graft designed to rapidly grow and remodel in vivo to restore the proper biomechanical properties of native ligament. The results using this graft as an ACL replacement are compared against those using a PT autograft for the ACL replacement. Uniaxial loading reveals that after nine months as an ACL replacement, the tissue-engineered graft develops a strain contour pattern closely resembling that of native ACL whereas the PT graft fails to similarly remodel in vivo.
Effect of Wind on Air-Cooled Condenser Performance
Authors: Maulbetsch John S. , DiFilippo Michael N. , O’Hagan Joseph
Published: August 2012

This paper documents the results of a field tests to determine the effect of wind on the performance of air-cooled condensers (ACCs) at power plants. Continuous measurements of wind speed, wind direction, cell inlet temperature and air flow and plant operating variables were made for several days at the El Dorado Energy Center. ACC performance was shown to be affected both by hot air recirculation and by fan performance degradation. Average recirculation, defined as the difference between the average cell inlet temperature and the far-field inlet temperature, was usually less than 3 °F. Occasional excursions to 4 to 10 °F were noted. Fan performance degradation is more difficult to quantify or generalize. Under low wind conditions this was typically close to the design value. The reduction in air flow, estimated from inlet velocity measurements would sometimes exceed 60 to 70% of the average flow in cells near the edge of the ACC during high wind conditions. Fan performance degradation appears to be the more important mechanism. Comparisons with flow modeling results support design recommendations for suppressing unfavorable flow patterns under the ACC.
Finite Deformation Elastoplasticity for Rate and Temperature Dependent Polycrystalline Metals
Authors: Regueiro Richard A. , Bammann Douglas J. , Marin Esteban B. , Johnson George C.
Published: August 2012

An elastoplasticity model is formulated and demonstrated in one-dimension (1D) for modeling finite deformations in poly-crystalline metals. Quasi-static to high strain rate effects as well as temperature sensitivity are included. A multiplicative decomposition of the deformation gradient into elastic, plastic, and thermal parts, that includes a volumetric/isochoric split of the elastic stretching tensor is assumed. The kinematics and thermodynamic formulation lead to constitutive equations, stresses, and constraints on the evolution of the internal state variables. The model accounts for (i) dislocation drag effects on flow stress, and (ii) generation (hardening) and annihilation (recovery) of statistically-stored dislocations (SSDs). The resulting model is normalized to dimensionless form to allow dimensionless material parameters fit for one metal to approximate the behavior of another metal of similar lattice structure, if data are limited. One dimensional material parameter fitting is demonstrated for two refractory metals, body centered cubic (bcc) Tantalum and Tungsten.
An Explicit Integration Method for Analysis of Wave Propagation in Heterogeneous Materials
Authors: Park K. C. , Lim S. J. , Huh H.
Published: August 2012

An explicit integrator for wave propagation analysis of heterogeneous solids is presented, which is aimed at minimizing spurious oscillations when the wave fronts pass through several zones of different wave speeds. Hence, the present method can be applied to multi-physics and multi-scale problems in which discontinuous spatial and temporal discontinuities need to be accurately captured without incurring spurious oscillations. The essence of the present method is a combination of two wave capturing characteristics: post-shock oscillations of most existing explicit integrators and a new integration construction that is designed to triggers shock-front oscillations. It is shown that a judicious combination of these two characteristics substantially reduces both shock-front and post-shock oscillations. The performance of the new method is demonstrated as applied to one-dimensional wave propagation through a uniform bar with varying courant numbers, then to heterogeneous bars.
Numerical Study of Ventilation Flow Through a Two Dimensional Room Fitted With a Windcatcher
Authors: Niktash A. R. , Huynh B. P.
Published: August 2012

A windcatcher is a natural ventilation device fitted on the roof of a building and divided internally into two halves to deliver fresh outside air into the building’s interior, and induce the stale air to the outside, working by pressure difference between outside and inside of the building. In this work, air flow through a two-dimensional but real-sized room fitted with a windcatcher is investigated numerically, using a commercial computational fluid dynamics (CFD) software package. The standard K-ε turbulence model is used. Flow pattern and flow velocity are considered in terms of the windcatcher’s location, inlet velocity, the shape of the windcatcher’s bottom and the length of the windcatcher’s bottom. It is found that when inlet velocity is not too low, the windcatcher’s shape at its bottom strongly affects flow pattern and flow velocity in the room. This leads to a way of improving the windcatcher’s effectiveness in ventilating the living area (lower part) of a room.
Empirical Correlation of Cooling Efficiency and Transport Phenomena of Direct Evaporative Cooler
Authors: Sheng Chenguang , Nnanna A. G. Agwu
Published: August 2012

Direct evaporative cooling (DEC) uses evaporating water, combined with a wetted medium to cool the temperature of air as it passes through. Evaporative cooling devices can reduce the energy consumption of HVAC&R (Heating, Ventilating, Air Conditioning, and Refrigeration Equipment). Heat is absorbed whenever water is evaporated and converted to water vapor. By passing through or around a wetted surface, heat is removed from the surrounding air in the vaporization of the water. The process approximates the adiabatic-saturation process and the path lies on a constant wet-bulb temperature which is a constant enthalpy line. This paper suspects the relationship between system parameters and cooling efficiency. Effects of three system parameters on cooling performance were evaluated. The three parameters selected for focus were the speed of frontal air, the dry-bulb temperature of frontal air, and the temperature of the incoming water. Each parameter was varied while holding all other variables like air, water mass flow rates and so on constant respectively, and data was collected using several different levels of each parameter. The general relationship between each parameter and efficiency was determined by graphing the data collected and observing trends. The empirical correlation between supply frontal air velocity and cooling efficiency for DEC system in a typical applied environment was established and verified by experiment data. Within certain ranges, DEC cooling efficiency increases with frontal air dry-bulb temperature; decreases with frontal air velocity and incoming water temperature correspondingly.
Technique for the Measurement of Surgical Screw Deflection
Authors: Andrade Brendan A. , Saigal Anil , James Thomas P.
Published: August 2012

Cyclical loading of surgical plating constructs can lead to screw failure through bending loads. In this research, an analytical beam mechanics model was developed to describe the elastic deflection of a cortical screw under a statically applied load. To test the predictive ability of the analytical model, a synthetic bone substitute was used for experiments. The bone substitute was a composite sandwich, consisting of two 6 mm cortical walls separated by a cancellous region. A novel instrument was developed to measure the bending deflection of screws under a radial load applied by a surgical plate at the screw head. A dial indicator and dowel pin arrangement was utilized to measure screw deflection at the screw head and along the length of the screw in order to determine a deflection curve for the screw axis. The analytical model accurately predicted deflection of the screw head at the location of the applied force, but overestimated deflection of the screw body in the cancellous region of the composite bone. Analytical predictions of location of the maximum bending moment matched the location of observed screw fracture in a clinical setting.
Brain Response to Extracranial Acoustic Loads: Shear Wave Propagation Characterized by Vector Fields
Authors: Clayton Erik H. , Bayly Philip V.
Published: August 2012

Traumatic brain injuries (TBI) due to blast are common in modern combat situations, and often lead to permanent cognitive impairment. Despite the prevalence and severity of blast-induced TBI, the condition remains poorly understood. Computer simulations of blast and blast injury mechanics offer enormous potential; however, computer models require accurate descriptions of tissue mechanics and boundary conditions in vivo. To gain insight into the mechanisms of blast injury, we applied direct (light) oscillatory pressure loading to the skulls of human volunteers, and measured displacement and strain fields using the methodology of magnetic resonance elastography (MRE). MRE is a non-invasive imaging modality that provides quantitative spatial maps of tissue stiffness. MRE is performed by inducing micron-amplitude propagating shear waves into tissue and imaging the resulting harmonic motion with standard clinical MRI hardware. Shear waves are initiated by an MR-compatible actuator and detected by a specialized “motion-sensitive” MRI pulse sequence (software). Motion sensitized MR images provide displacement field data which can be inverted to estimate material stiffness by invoking a restricted form of Navier’s equation. Clinical interest in MRE has largely been driven by the empirical relationship between tissue stiffness and health. However, the “raw” MRE data (3-D displacement measurements) themselves can elucidate loading paths, anatomic boundaries and the dynamic response of the intact human head. In this study, we use the MRE imaging technique to measure in vivo displacement fields of brain motion as the cranium is exposed to acoustic frequency pressure excitation (45, 60, 80 Hz) and we calculate the resulting shear-strain fields (2-D). We estimate the Poynting vector (energy flux) field to illuminate the directions of internal wave propagation, and to identify the energy absorbing and reflecting regions within the brain.
The Load Factor and Permanent Set at the Bearing Surfaces in Hollow Cylindrical Bolted Joints Under External Axial Loads
Authors: Morozumi Yukio , Okumura Masahiko , Sawa Toshiyuki , Kuwaki Kengo
Published: August 2012

High strength bolts are utilized widely for high reliability and to reduce the weight of the bolted joints. The usage of the high strength bolts may increase the contact stress at the bearing surfaces. When a bolted joint is under external axial load W, the axial bolt force increases by Ft and the contact stress increases at the bearing surface. This may cause the plastic deformation and a decrease in the axial bolt force. Consequently, it is important to determine the initial axial bolt force (bolt preload) considering external load. In this paper, (load factor) Φ = (Ft/W) is investigated by axi-symmetrical theory of elasticity, FEM analysis and experiments. The results obtained from these methods showed in a fairly good agreement. Then the contact stress distributions and the plastic displacement distributions under external loads were studied for three different initial axial forces by elasto-plastic FEM analyses. The prediction for the reduction in axial bolt force, which is obtained by multiplying the setting factor by the mean plastic displacement, was compared with the experiment. As a result, it was found that a higher bolt preload shows a small reduction in axial bolt force.
The Effect of External Magnetic Field on the Plasma Induced by Laser Ablation in Vacuum
Authors: Wu Benxin , Tao Sha , Gao Yibo , Zhou Yun , Cheng Gary
Published: August 2012

During short-pulsed laser ablation (machining) process at sufficiently high intensities, a plasma plume may be generated above the target surface. In this paper, the effect of external magnetic fields on laser-induced plasma has been studied using a physics-based model. In the model, hydrodynamic equations coupled with wide-range equations of state are solved numerically using a finite-difference essentially non-oscillatory (ENO) method. The magnetic field affects the plasma evolution by inducing electric currents, and the associated electromagnetic force and Joule heating effect in the plasma. The study shows that the external magnetic field may decrease the plasma front expanding speed, and increase the plasma temperature. The study provides useful information for the fundamental study of laser-induced plasma, and for the practical applications of short-pulsed lasers in laser ablation (machining), laser-induced breakdown spectroscopy (LIBS), and other areas, where laser-induced plasma may play a very important role.
Hydraulic Balance Ring Study and Design Using Optical Techniques
Authors: Thompson-Salinas Alfonso , Ortega-Bren˜a Martin , De la Torre-Ibarra Manuel H. , Barrientos-Garci´a Bernardino , Gonzalez-Villela Victor J.
Published: August 2012

A new approach to understand factors that affect self-balancing devices is proposed. Experimentation was conducted to determine the influence of different factors on the performance of an automatic washing machine hydraulic balance ring fluid during transient and steady states. Two different optical techniques were used: one for visualization (high-speed photography) and another for velocity field measurement (Particle Image Velocimetry, PIV). Results were used to build a new balancer design and compared with previous findings. Important factors in balancer design were deducted.
A Nonlinear Automatic Landing Control System for a UAV
Authors: Atmeh Ghassan M. , Al-Taq Wahba I. , Hasan Zeaid
Published: August 2012

An automatic landing system for an unmanned aerial vehicle (UAV) is presented in the following paper. The nonlinear aircraft model with thrust, elevator, rudder and aileron deflections as control inputs is established using the appropriate aerodynamic data. The flight trajectory the airplane is expected to travel during landing is then defined. A nonlinear control law, using feedback linearization method, is designed to develop the automatic landing controller for the UAV aircraft. A linear state-feedback control law is also designed for means of comparison with the nonlinear controller. The elevator is employed for longitudinal control whereas the rudder and aileron aid in lateral control. Thrust is the control input for velocity control, which is held constant during landing. A nonlinear simulation, incorporating wind shear and ground effects, is run using MATLAB/Simulink to assess the controllers’ integrity. The auto-landing system designed in this paper is meant to increase the autonomy of the UAV to eventually reach a fully autonomous system. Simulation results show the importance of designing the controller considering such effects. Landing trajectory tracking performance by the nonlinear controller is of great tone.
Measurement of Hydrodynamic Frictional Drag on Superhydrophobic Flat Plates in High Reynolds Number Flows
Authors: Aljallis Elias , Sarshar Mohammad Amin , Datla Raju , Hunter Scott , Simpson John , Sikka Vinod , Jones Andrew , Choi Chang-Hwan
Published: August 2012

In this paper, we report the characterization of large-scale superhydrophobic surfaces for hydrodynamic drag reduction in boundary layer flows using a high-speed towing tank system. For making superhydrophobic surfaces, flat aluminum plates (4 ft × 2 ft × 3/8 in, with sharpened leading/trailing edges) were prepared and coated with nano-structured hydrophobic particles. The static and dynamic contact angle measurements indicate that the coated surfaces correspond to a de-wetting (Cassie) state with air retained on the nano-structured surfaces. Hydrodynamic drag of the large-area superhydrophobic plates was measured to cover turbulent flows (water flow speeds up to 30 ft/s, Reynolds number in the range of 105−107) and compared with that of an uncoated bare aluminum control plate. Results show that an acceptable drag reduction was obtained up to ∼30% in the early stage of the turbulent regime which is due to reduced shear forces on the plates because of the lubricating air layer on the surface. However, in a fully developed turbulent flow regime, an increase in drag was measured which is mainly attributed to the amplified surface roughness due to the protrusions of air bubbles formed on the surface. Meanwhile, a qualitative observation suggests that the air bubbles are prone to be depleted during several runs of the high shear-rate flows, as revealed by streak lines of depleted air bubbles. This suggests that the superhydrophobic coating is unstable in maintaining the de-wetted state under dynamic flow conditions and that the increased drag results from the inherent surface roughness of the coating layer where the de-wetted state collapses to a wetted (Wenzel) state due to the depletion of air bubbles. However, it was also observed that the air bubbles would reform on the surface, with the same properties as a dry surface immersed in water, while the plate was kept statically immersed in water for 12 hours, suggesting that the superhydrophobic coating retains static stability for a de-wetted state. The experimental results illustrate that drag reduction is not solely dependent on the superhydrophobicity of a surface (e.g., contact angle and air fraction), but the morphology and stability of the surface air layer are also critical for the design and use of superhydrophobic surfaces for large-scale hydrodynamic drag reduction, especially in turbulent flow regimes.
Hybrid Energy Storage System for Hybrid and Electric Vehicles: Review and a New Control Strategy
Authors: Zhang Xing , Dong Zuomin , Crawford Curran
Published: August 2012

Onboard energy storage system (ESS) plays a major role for vehicle electrification. The performance of hybrid electric vehicle (HEV), plug-in HEV (PHEV), extended range electric vehicle (EREV), fuel cell vehicle (FCV), and electric vehicles (EV) heavily depends upon their ESS technology. The ESS must be able to store sufficient energy for adequate pure electric range, provide adequate peak power for needed vehicle performance under various driving cycles, absorb energy efficiently during regenerative breaking, and have long operation life and low costs. At present, pure battery based ESS often cannot effectively meet all these requirements due to many trade-offs. In order to improve the overall performance of ESS, integration of two (or more) energy sources have been studied to best utilize the unique characteristics of each, leading to a hybrid energy storage system (HESS). Hybridization of high-energy batteries and ultracapacitors with complementary characteristics present a common choice today. In this paper, the necessity and superiority of a HESS are illustrated considering system performance, efficiency, costs, functional life, and temperature requirements. Three major types of battery-ultracapacitor HESS, passive, semi-active and fully active, are presented. Various HESS control strategies proposed in the past are then reviewed, including rules or reference curves and tables based control, fuzzy logic control, and closed-loop control. Building upon these review and analyses, a novel control strategy based on signal separation using sparse coding is proposed at the end.
Investigation of Two Analytical Wake Models Using Data From Wind Farms
Authors: Mittal Anshul , Taylor Lafayette K. , Sreenivas Kidambi , Arabshahi Abdollah
Published: August 2012

A code ‘Wind Farm Optimization using a Genetic Algorithm’ (referred as WFOG) was developed for optimizing the placement of wind turbines in large wind farms. It utilizes an analytical wake model (by Jensen et al.) to minimize the cost per unit power for the wind farm. In this study, a new wake model by Ishihara et al. is tested in WFOG. The wake model takes into account the effect of atmospheric turbulence and rotor generated turbulence on the wake recovery. Results of the two wake models are compared with data from Horns Rev and Nysted wind farm. The maximum error (Horns Rev wind farm) for Ishihara’s wake model was 7% as compared to 15% for Jensen’s wake model. The optimal results obtained in earlier studies (using Jensen’s wake model) are compared to wind farm configurations obtained for Ishihara’s wake model. The optimization is carried out for the simplest wind regime: Constant wind speed and fixed wind direction.
Experimental Investigations of Turbulent Gas Flow in a Micro-Channel
Authors: Matsushita Shinichi , Hong Chungpyo , Asako Yutaka , Ueno Ichiro
Published: August 2012

This paper presents experimental investigations on turbulent gas flow characteristics of nitrogen gas through a micro-channel. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter is 147.76 micro meters. The micro-channel was designed with a main flow channel and seven side channels, which lead to the pressure transducers. The stagnation pressure was designated in such a way that the flow is in turbulent flow regime. The outlet of the channel faced to the atmosphere. The pressures of the main channel at seven locations were measured by gauge pressure transducers to determine local values of Mach number. And the pressure differences of each pressure ports were measured by differential pressure transducers to obtain the pressure losses precisely. The pressure distribution of turbulent gas flow through a micro-channel falls steeply and Mach number increases near the outlet with increasing the inlet pressure due to flow acceleration. Both Darcy friction factor and Fanning friction factor were obtained for turbulent flow. The result shows that the obtained both friction factors were evaluated as a function of Reynolds number on the Moody chart. The values of Darcy friction factors differ from Blasius correlation for turbulent flow regime due to the compressibility effects, however the values of Fanning friction factors coincide with Blasius correlation.
Transmission Error in Synchronous Belt With Resonance Under Installation Tension
Authors: Kagotani Masanori , Ueda Hiroyuki
Published: August 2012

Synchronous belt drives are widely employed to transmit rotation accurately. The belt spans between the driving and driven pulleys generate resonance when the transverse natural frequency of the belt, as in string vibration, matches the meshing frequency of the belt tooth and the pulley tooth. The resonance of the belt spans affects the behavior of the transmission error. In the present study, the mechanisms generating the transmission error in synchronous belt drives under installation tension and a pulley speed ratio of 1:1 are investigated theoretically and experimentally for the case in which the belt spans generate first mode vibration due to resonance. The calculated and experimental transmission errors show good agreement, and so the validity of our analysis is confirmed. The transmission error has a period of 1/2 of one pitch of the pulley, and is generated by the difference in displacement between the upper and lower belt spans, the difference in the amount of belt climbing at the beginning and end of meshing, and the generation of torque due to the moment of inertia on the driven side.
Integration of Computational Fluids Dynamics and Virtual Reality Visualization for Constructing the Wind Field
Authors: Lu Lu , Wang Xiuling
Published: August 2012

3-D wind field models were developed for constructing 3-D wind fields in an urban wind condition and over irregular terrain. The virtual environment is used to visualize the simulation results. Simulation results based on statistical input data were obtained for 3-D urban wind flow over the Classroom and Office (CLO) building at Purdue University Calumet (PUC). The objective for this project was to construct the 3D wind field around the roof of the CLO building in order to analyze the wind condition and identify a suitable installation area which would have relatively more wind power but less turbulence for the wind turbine. By using the virtual reality (VR) technique, the simulation results can be clearly and vividly shown in a virtual environment that would not be as limited as traditional two-dimensional views. Statistical analysis was based on the wind data that was recorded by a sensor located on the roof of the CLO building. Specific wind conditions, which were obtained from the statistical analysis, were applied to simulation cases for the wind flow around a 3-D geometry model of the CLO building. In addition, different wind directions were applied in the Fluent program. After the CFD simulation results were exported, the virtual reality technique was used to visualize the simulation results, which can be observed intuitively. Visualization of simulation results are easier to be observed and be analyzed.
Characteristics of Planar Counter Current Shear Flow in Dump Geometry
Authors: Kalghatgi Prasad , Acharya Sumanta , Strykowski Paul , Anderson Matt
Published: August 2012

Countercurrent shear can be used in engineering applications to control flow structure and mixing. In the present paper a planar countercurrent shear flow is studied numerically using Large Eddy Simulation. Mean flow characteristics at a primary-jet Reynolds number of 14700 are studied for three values of a key parameter, the secondary to primary jet mass flow ratio (m˙s/m˙p), chosen to match reported measurements. The predicted flow results of time averaged flow field, Strouhal number and turbulence characteristics are compared with the experimentally available data. A change in instability modes is observed at mass flow ratios above m˙s/m˙p = 0.27 with more than 100% increase in the turbulence levels and distinct changes in spectral characteristics. Detailed spectral records along with landau modeling are used as evidence of existence of self excited global mode beyond a critical velocity ratio in the flow.
Review of Continuously Variable Transmission Powertrain System for Hybrid Electric Vehicles
Authors: Dong Jian , Dong Zuomin , Crawford Curran
Published: August 2012

In this paper, a review of the state-of-the-art of various CVT powertrain systems now used or being planned for future use in HEVs is presented. These CVT powertrain systems are classified into three main categories: mechanical CVT, electromechanical CVT (ECVT) and pure electrical CVT (EVT). The research development, system architecture, operation characteristics and the merits and drawbacks of each type are discussed.
Characterization of Irregular Stress Distributions Induced by Klippel Feil Syndrome
Authors: Leung Enoch , Sarigul-Klijn Nesrin , Roberto Rolando F.
Published: August 2012

Klippel Feil Syndrome (KFS) is a congenital disorder characterized by failure of segmentation of cervical vertebrae, resulting in “fusions” at any level of the cervical spine. Clinical diagnosis of KFS occurs at a mean age of 7.1 years, with children diagnosed with KFS often exhibiting reduced motion and function characterized by reduction of upward and downward motions of the head on the neck (flexion/extension), axial rotation, and tilting of the head side to side (lateral bending). More importantly, however, previous KFS studies have acknowledged possible compromises to the structural integrity and overall health of the cervical spine in the presence of abnormal fusion. Instances of instabilities such as fracture and large amounts of mobility at vertebral segments adjacent to fusion have been recorded, both posing significant neurological and physiological dangers to an individual afflicted with KFS. While fusion and instability appear to be interrelated, more intrinsic evaluation of KFS-related instabilities is needed. Current KFS studies, relying predominantly on static radiographic modalities, have been unsuccessful in identifying factors contributing to craniocervical (CC) destabilization in the presence of congenital vertebral fusion. It has been hypothesized that fusion of vertebral bodies induces abnormal stress distributions that catalyze instances of fracture along any KFS spine segment. Using Finite Element (FE) Modeling and Analysis to characterize motion alterations and irregular stress patterns associated with vertebral fusion, a high fidelity computational representation of a KFS affected cervical spine segment spanning the base of the occiput to C6 was constructed. Computer Tomography (CT) images were used for vertebral reconstruction with soft tissue components such as intervertebral discs (IVDs), articular cartilages (ACs), and the transverse ligament were modeled as homogenous solid components.
Vibration Effects on Heat Transfer During Solidification of Paraffin
Authors: Vadasz Johnathan , Meyer Josua , Govender Saneshan , Ziskind Gennady
Published: August 2012

Previous work looked at the solidification process of PCM (phase change material) paraffin wax. Experimental results were compared with numerical work done in CFD package FLUENT. In the current study, the effects of vibration on heat transfer during the solidification process of PCM in a sphere shell are investigated. Enhancement of heat transfer results in quicker solidification times and desirable mechanical properties of the solid. The amount of PCM used was kept constant during each experiment by using a digital scale to check the weight, and thermocouple to check consistent temperature. A small amount of air was present in the sphere so that the sphere was not filled completely. Commercially available paraffin wax, RT35, was used in the experiments. Experimentations were done on a sphere of 40 mm diameter, wall temperature 20°C below mean solidification temperature, and consistent initial temperature. A vibration frequency was varied from 10–300 Hz was applied to the set-up and results compared with that of no vibration. Samples were taken at different times during the solidification process and compared with respect to solid material present.
Modeling Tire Tread Block Dynamics by a Timoshenko Beam Model
Authors: Ripka Stefan , Zimmermann Martin , Wallaschek Jo¨rg
Published: August 2012

The development of winter tires becomes more and more important due to worldwide growing markets. In the present paper, siped tire tread blocks will be investigated. First the Timoshenko beam model to investigate such tread blocks will be introduced. Afterwards the focus is put on modelling stationary and transient dynamic processes. The computational results will be compared to experimental data, and the model will be validated systematically, including an evaluation of the relative importance of different modeling assumptions. It can be shown that the Timoshenko beam model allows an accurate description of tire tread block dynamics at low computational load.
Parametric Influence and Optimization of Wire EDM on Oil Hardened Non Shrinking Steel
Authors: Kuruvila Nixon , Ravindra H. V.
Published: August 2012

Wire-cut Electro Discharge Machining (WEDM) is a special form of conventional EDM process in which electrode is a continuously moving conductive wire. The present study aims at determining parametric influence and optimum process parameters of Wire-EDM using Taguchi’s Technique and Genetic algorithm. The variation of the performance parameters with machining parameters was mathematically modeled by Regression analysis method. The objective functions are Dimensional Accuracy (DA) and Volumetric Material Removal Rate (VMRR). Experiments were designed as per Taguchi’s L16 Orthogonal Array (OA) where in Pulse-on duration, Current, Pulse-off duration, Bed-speed and Flushing rate have been considered as the important input parameters. The matrix experiments were conducted for the material Oil Hardened Non Shrinking Steel (OHNS) having the thickness of 40 mm. The results of the study reveals that among the machining parameters it is preferable to go in for smaller pulse-off duration for achieving over all good performance. Regarding MRR, OHNS is to be eroded with medium pulse-off duration and higher flush rate. Finally, the validation exercise performed with the optimum levels of the process parameters. The results confirm the efficiency of the approach employed for optimization of process parameters in this study.
Surface Modifications for Improved Maneuverability and Performance of an Aircraft
Authors: Srivastav Deepanshu , Ponnani K. N.
Published: August 2012

The work describes a comparative study of aerodynamic characteristics of an aircraft wing model with and without surface modifications to it. The surface modifications that are considered here are outward dimples on the wing model. In the present study, results of computational fluid dynamics (CFD) analysis are presented showing variance in lift and drag of modified wing models at different angle of attacks. Dimples on the surface aircraft wing model doesn’t affect much the pressure drag since it’s already aerodynamic in shape but it can affect the angle of stall. This project verifies if the dimples that reduce a golf ball’s drag, can also increase an airplane’s critical angle of stall. Dimples delay the boundary layer separation by creating more turbulence over the surface. The airfoil profile considered here is NACA-0018 with uniform cross-section throughout the length of airfoil. Subsonic flows are considered for the study. The CAD model is prepared in CatiaV5 R18 and simulations are carried out in Comsol 3.4 and Comsol 4.0. The overall aim of the study is improved maneuverability and performance of an aircraft. The results justify the increase in the overall lift and reduction in drag of the aircraft, also change of stall angle with different surface modifications on the wing model is observed.