bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical Modeling for Mechanical Responses of an Axially Loaded Three-Phase Active Fiber Composite
Authors: Askari Davood , Ghasemi-Nejhad Mehrdad N.
Published: May 2009

Structural integrity and stability are among the key requirements for any mechanical component used in structural applications when subjected to external or internal loads. For example, Active Fiber Composites (AFCs) or micro fiber composites (MFCs) used as sensors and actuator for vibration damping, structural control, and health monitoring in intelligent structures can be subjected to both external and internal loading. Furthermore, demands from industry for better performing sensors and actuators for the use in adaptive structures have led the researchers to investigate and design AFC/MFC systems with optimal configurations to enhance their performances. Therefore, it is essential to understand and be able to predict the mechanical behaviour of the individual AFCs/MFCs that exist in different geometrical configurations composed of various constituent materials. In this work, an analytical approach based on elasticity equations is introduced to derive exact solutions for mechanical responses (i.e., displacements, strains, and stresses) of an axially loaded threephase composite cylinder, representing an individual AFC/MFC tube. Materials of the constituents are considered to be orthotropic for no loss of generality. To validate the exact analytical solutions, finite element analysis is performed and then the results obtained from both techniques are compared where excellent agreements are achieved.
Reconstruction Method for Complex Groove of Milling Insert Using Local Rule of Cellular Automata
Authors: Tan Guangyu , Liu Guangjun , Li Guanghui , Rong Yiming , Song Hui
Published: May 2009

This paper presents a groove reconstruction method based on the local rule of Cellular Automata (CA). A local rule for groove reconstruction is proposed to design and optimize the groove of milling insert. The insert is firstly divided into a large number of cells that typically form a regular grid over the domain. The domain consists of regular square cells with discrete variables and the discrete CA model is built. As the cells in the CA domain only interact with their neighboring cells when performing local computations, the governing equation for the whole domain is not necessary. Then the states of cells are modified according to the local rule applied. The state of the entire system is updated based on the state of the cell and its neighboring cells. Collectively, these cells’ states define the state of the entire domain, and the groove can be reconstructed according to the state of the domain. The reconstructed groove is tested by a FEM simulation. The simulation results show that the reconstructed groove has a satisfied performance on the stress field.
Flow/Acoustic Mechanisms in Three-Dimensional Vortices Undergoing Sinusoidal-Wave Instabilities
Authors: Li Wenhua , Zheng Z. C. , Xu Ying
Published: May 2009

It has been identified that vorticity in a vortex core directly relates to the frequency of a significant sound peak from an aircraft wake vortex pair where each of the vortices is modeled as an elliptic core Kirchhoff vortex. In three-dimensional vortices, sinusoidal instabilities at various length scales result in significant flow structure changes in these vortices, and thus influence their radiated acoustic signals. In this study, a three-dimensional vortex particle method is used to simulate the incompressible vortical flow. The flow field, in the form of vorticity, is employed as the source in the far-field acoustic calculation using a vortex sound formula that enables computation of acoustic signals radiated from an approximated incompressible flow field. Cases of vortex rings and a pair of counter-rotating vortices are studied when they are undergoing both long- and short-wave instabilities. Both inviscid and viscous interactions are considered and effects of turbulence are simulated using sub-grid-scale models.
Effect of Geometry on the Performance of Miniature Heat Pipe
Authors: Uddin Ahmed Imtiaz , Atiqul Islam A. S. M. , Feroz Chowdhury Md.
Published: May 2009

An experimental study is performed to investigate the effect of geometry on the performance of miniature heat pipe (MHP). The experiment is conducted with circular and square MHPs having the same hydraulic diameter of 5 mm and length of 150 mm with acetone as the working fluid. The major findings in the investigation are as follows. At a constant heat flux, coolant flow rate and inclination angle, wall temperatures of evaporator section of circular MHP are higher than that of the square MHP. With the decrease in both inclination angle and coolant flow rate, the rate of increase in wall temperature of the evaporator section for circular MHP is higher than that of square MHP. Thermal resistance of the circular MHP is almost independent of coolant flow rate but for square MHP, thermal resistance decreases with the increase in coolant flow rate. Again at a constant coolant flow rate, heat flux and inclination angle, the thermal resistance for square MHP shows much smaller value than that of circular MHP. Overall heat transfer coefficient for square MHP is maximed at vertical orientation.
Deployable Micro-Tabs in Aircraft Noise Control Near Airports: Scaled Experimental Apparatus and Computational Results
Authors: Sarigul-Klijn Nesrin , Kuo Brian C. , Karnopp Dean C.
Published: May 2009

Reducing acoustic noise emission of commercial aircraft is of great interest to communities near airport. It is well recognized that the aircraft noise during the landing approach is mostly due to use of high lift devices. In this paper, in-flight deployable micro-tab devices are investigated for their suitability in aircraft landing nose control. This is accomplished with the use of the virtual-reality after scaled testing-simulation-validations approach. A scaled testing apparatus had to be designed to capture non-propulsive noise from aircraft during approach to validate the results of computational scaled simulation. This apparatus now serves as an anechoic wind tunnel at low Mach numbers and its design is detailed. We proposed use of lift generating micro-tab device that will allow reduced slat and/or flap settings during the approach thereby causing a reduction in airframe noise. Simulations based on a 1/3rd scaled B737 wing resulted in promising noise reductions for the case with deployed micro-tab.
Harmonic Resonance Frequency Factor of Spur Gear System and Oscillation Reduction Approaches
Authors: Wang Jianping , Li Pengfei , Wu Ziying , Zhang Minghong
Published: May 2009

In this study, a non-linear time-varying dynamic model of a spur gear pair system is used to investigate the dynamic behavior of the system by means of multiple scale approach. Both time-varying stiffness, transmission error and tooth backlash clearance of the system are taken into account in the model. The mesh stiffness fluctuation is developed as high order Fourier series and tooth backlash clearance is fitted by high order polynomial function. The frequency factors of the system are investigated and the frequency-response equations at the case of internal and external excitation, parametric excitation and combined excitation are obtained. The peak value of the amplitude of the primary resonance, super and sub harmonic resonance and combination harmonic under internal, external and parametric excitation are researched. The approaches of vibration reduction are investigated. Finally an example is investigated using the presented process and the results indicate the sensitivity and correctness of the presented analysis approaches.
Nonlinear Dynamics of a Gear Transmission System: Part II — Periodic Impacting Chatter and Stick
Authors: Luo Albert C. J. , O’Connor Dennis
Published: May 2009

In Part I, the motion mechanism of impacting chatter and stick motion in the gear transmission dynamical system was discussed. This paper focuses on periodic motions relative to the impacting chatter and stick in order to find the origin of noise and vibration in such a gear transmission system. Such periodic motions are predicted analytically through mapping structures, and the corresponding local stability and bifurcation analysis are carried out. The grazing and stick conditions presented in Part I are adopted to determine the existence of periodic motions, which cannot be achieved from the local stability analysis. Numerical simulations are performed to illustrate periodic motions and stick motion criteria. Such an investigation may provide some clues to reduce the noise in gear transmission systems.
The Design and Experimental Study of a Multi- Diaphragm Piezoelectric Synthetic Jet Actuator
Authors: Xu Jinglei , Li Chao , Sha Jiang , Zhang Kunyuan
Published: May 2009

Considering the shortcoming and inability of the conventional piezoelectric synthetic jet actuator (PE-SJA), a novel multi-diaphragm PE-SJA was designed and made in this paper, and some detailed experimental study was carried out upon it. Using the hotwire anemometry, the optimum resonance frequency of the actuator was obtained. Then, under this special frequency, velocity magnitude was measured at different positions along the axis of the orifice. And then the orifice exit velocity of different numbers of diaphragm was measured, analysized and compared, which showed that the mean and peak axis velocity of one diaphragm PE-SJA were only the half of those of the five diaphragms PE-SJA., while the performance of three diaphragms PE-SJA was almost the same as that of the five diaphragms., which meant that although the performance of the PE-SJA increased with the number of the piezoelectric diaphragm, it was not in linearly ways. From the experimental result it was also shown that: For frequency f = 560Hz, the optimum diameter and depth of the orifice was 2.5mm and 2mm, respectively. Therefore, the optimum depth/diameter ratio was 0.8 for the present actuator and frequency. And then the performance of the multi-diaphragm PE-SJA with taper-jet exit orifice was much better than that of the straight orifice. Finally, the PIV was used to measure the structure of vortex of the flowfield.
Comparative Investigation of N-Heptane Droplet Ignition in High Temperature Convective Environments
Authors: Chen J. , Peng X. F. , Ju Y. G. , Wang B. X.
Published: May 2009

A 2-D numerical model was proposed to investigate the ignition of liquid fuel droplets in convective environments at high temperature. This model employed a skeletal mechanism consisting of 34 reactive species and 56 elementary reactions, rather than one-step overall reaction as in normal 2-D droplet ignition models, because the skeletal mechanism for n-heptane reproduces ignition delay times at various temperatures and pressures reasonably well. In present investigation an emphasis was addressed on the comparative analysis of suitability of the model, particularly numerical simulations were compared with experiments available in the literature, or for N-heptane droplets ignition in the convective air at temperature in a range of 1100K∼1400K and velocity of 2m/s. The ignition delay time and ignition position were obtained using an ignition criterion based on OH radical mass fraction. The flame behavior after ignition was also studied comparatively. The agreement between numerical simulation and experiments is reasonably good.
Hunting Stability Analysis of a New High-Speed Railway Vehicle Model Moving on Curved Tracks
Authors: Cheng Yung-Chang , Lee Sen-Yung
Published: May 2009

A new dynamic model of railway vehicle moving on curved tracks is proposed. In this new model, the motion of the car body is considered and the motion of the tuck frame is not restricted by a virtual boundary. Based on the heuristic nonlinear creep model, the nonlinear coupled differential equations of the motion of a fourteen degrees of freedom car system, considering the lateral displacement and the yaw angle of the each wheelset, the truck frame and the car body, moving on curved tracks are derived in completeness. To illustrate the accuracy of the analysis, the limiting cases are examined. In addition, the influences of the suspension parameters on the critical hunting speeds evaluated via the linear and the nonlinear creep models respectively are studied. Furthermore, the influences of the suspension parameters on the critical hunting speeds evaluated via the fourteen degrees of freedom car system and the six degrees of freedom truck system, which the motion of the tuck frame is restricted by a virtual boundary, are compared.
Design of an Electromagnetic Shock Absorber
Authors: Ebrahimi Babak , Khamesee Mir Behrad , Golnaraghi M. Farid
Published: May 2009

This paper presents the design, modeling, and Finite Element (FE) analysis of a novel Electromagnetic Damper (ED). This cost-effective, regenerative ED is based on the concept of the tubular, linear, brushless dc motor. The structure of the proposed passive ED is straightforward, and it does not require an external power supply. An analytical model of the system is obtained using the magnetic circuit method and used to optimize the non-dimensional geometry factors and to estimate the electromagnetic forces and flux induced in the system. The model can be used to design high-performance dampers for various applications. To confirm the design, dynamic FE simulations were conducted and compared with the analytical and experimental results.
Lattice Boltzmann Simulation to Study Multiple Bubble Dynamics
Authors: Gupta Amit , Kumar Ranganathan
Published: May 2009

Lattice Boltzmann method (LBM) has been used in this study to understand the behavior of bubble motion and bubble coalescence in liquids. For a fully periodic domain, bubble dynamics and shape for a single bubble and multiple bubbles are dependent on Eotvos number, Reynolds number and Morton number. Drag coefficient for single bubble motion under buoyancy has been computed and compared with existing correlations provided in terms of the flow parameters. For multiple bubbles, the bubble dynamics is dictated by vortex pattern of the leading bubble, which allows the bubbles to coalesce. Such simulations have also been run for different configurations of the initial bubble distribution for both in-line and staggered bubble configuration to show the effect of vortex shedding on the oscillatory motion of the bubbles.
Exact Solution of Time History Response for Dynamic Systems With Arbitrary Viscous Damping Using Complex Modal Analysis
Authors: Thompson Lonny L. , Chinnakonda Manoj Kumar M.
Published: May 2009

A solution method for general, non-proportional damping time history response for piecewise linear loading is generalized to exact solutions which include piecewise quadratic loading. Comparisons are made to Trapezoidal and Simpson’s quadrature rules for approximating the time integral of the weighted generalized forcing function in the exact solution to the decoupled modal equations arising from state-space modal analysis of linear dynamic systems. Closed-form expressions for the weighting parameters in the quadrature formulas in terms of time-step size and complex eigenvalues are derived. The solution is obtained step-by-step from update formulas derived from the piecewise linear and quadratic interpolatory quadrature rules starting from the initial condition. An examination of error estimates for the different force interpolation methods shows convergence rates depend explicitly on the amount of damping in the system as measured by the real-part of the complex eigenvalues of the state-space modal equations and time-step size. Numerical results for a system with general, non-proportional damping, and driven by a continuous loading shows that for systems with light damping, update formulas for standard Trapezoidal and Simpson’s rule integration have comparable accuracy to the weighted piecewise linear and quadratic force interpolation update formulas, while for heavy damping, the update formulas from the weighted force interpolation quadrature rules are more accurate. Using a simple model representing a stiff system with general damping, we show that a two-step modal analysis using real-valued modal reduction followed by state-space modal analysis is shown to be an effective approach for rejecting spurious modes in the spatial discretization of a continuous system.
Nanoscale Vibrational Behavior of Single-Layered Graphene Sheets
Authors: Sakhaee-Pour A. , Ahmadian M. T. , Vafai A.
Published: May 2009

Molecular structural mechanics approach is implemented to investigate vibrational behavior of single-layered graphene sheets. By using the atomistic modeling, mode shapes and natural frequencies are obtained. Vibration analysis is performed under different chirality and boundary conditions. Numerical results from the finite element technique are applied to develop empirical equations via a statistical multiple nonlinear regression model. With the proposed empirical equations, fundamental frequencies of single-layered graphene sheets under considered boundary conditions can be predicted within 3 percent accuracy.
Modeling and Optimization of Planar Electret-Based Electrostatic Energy Harvester
Authors: Mahmoud M. A. E. , El-Saadany E. F. , Mansour R. R.
Published: May 2009

Development of a planar electret based electrostatic micro-generator for vibration energy harvesting is presented. The new harvester has the advantage of possible low cost fabrication and low power losses operation. Moreover, the new harvester uses a slabbed periodic structure allowing the decoupling between the energy conversion cycle and the vibration source frequency. In this paper, the details of this implementation are revealed. Modeling equations of the resulting structure are illustrated and solved numerically. Simulation results are given showing more than 78% improvement in the average output power of the optimized structure compared to previous implementation.
Modeling and Excitation Torque Estimation of an Engine Cold-Test Stand for Evaluating Driveline Design and Fault Diagnostics
Authors: Gul Kamran A. , Adams Douglas E.
Published: May 2009

The fault detection process becomes difficult in engine cold-testing when the test stands undergo torsional vibrations excited by various engine harmonics. In the context of vibration suppression and assembly faults diagnostics, this paper focuses on three main aspects: cold-test stand modeling and validation, estimation of cold-engine excitation torque, and evaluation of a fuel injector pulse diagnostic test. To analyze the vibratory torque of the cold-test stand driveline, an engine excitation model comprising of inertia torque and unfired gas pressure torque is needed. The gas pressure torque cannot be determined in the absence of engine gas pressure measurements. It is shown that this excitation torque can be estimated by assuming that the net torque during the unfired engine cycle is zero and by utilizing the firing engine gas pressure torque in the combustion stroke. The estimated excitation torque is employed to validate models of different cold-test stands and also to examine various driveline design alternatives. Using embedded sensitivity functions, it is found that by changing the inertia and stiffness of the rubber coupling, the torsional vibrations can be suppressed. Finally, the modified design is evaluated for an injector pulse diagnostic test. It is shown that the design modifications can also enhance sensitivity to faults if the injector pulse test is carried out at higher speeds.
Thermodynamics From a Few Dynamic Particles Raises Questions as to How Temperature and Entropy Should Be Perceived and Defined
Authors: Dartnall W. John , Reizes John
Published: May 2009

In a recently developed simple particle mechanics model, in which a single particle represents the working fluid, (gas) in a heat engine, (exemplified by a piston engine) a new approach was outlined for the teaching of concepts to thermodynamic students. By mechanics reasoning, a model was developed that demonstrates the connection between the Carnot efficiency limitation of heat engines, and the Kelvin-Planck statement of Second Law, requiring only the truth of the Clausius statement. In a second paper the model was extended to introduce entropy. The particle’s entropy was defined as a function of its kinetic energy, and the space that it occupies, that is analogous to that normally found in classical macroscopic analyses. In this paper, questions are raised and addressed: How should temperature and entropy be perceived and defined? Should temperature be proportional to average (molecular) translational kinetic energy and should entropy be dimensionless?
Functionalized Single Walled and Double Walled Carbon Nanotubes for Thermal Enhancement
Authors: Milanova Denitsa , Kumar Ranganathan
Published: May 2009

Our investigation in this study focuses on the chemical and thermal characteristics of Single Walled Nanotubes (SWNTs) in comparison with Double Walled Nanotubes (DWNTs) for their potential to extend the heat flux in the boiling regime. SWNTs and DWNTs were successfully dispersed in an aqueous medium by reducing the surface tension, i.e. adsorption of anionic surfactant (NaDDBS). Two mechanisms of stabilization have been adopted: electrosteric and steric stabilization, and the suspensions were seen to be stable for longer periods. DWNTs have better heat transfer performance in the pool boiling experiment due to their unique structure. Functionalization and surfactant coating of SWNTs may reduce the heat flow because of modification of the structure. The burnout heat flux of the immersed Nichrome wire in water under pool boiling conditions was increased by up to 170% over that for the pure base liquid for DWNT nanofluid. In contrast, SWNT nanofluid enhanced burnout heat flux by 30%. The nature of the deposition on the heating element affects the surface wetting and therefore the pool boiling curve. DWNT coating on the wire is much thinner than SWNT coating; however, it is more porous and enhances CHF.
A Variational Asymptotic Model for Predicting Initial Yielding Surface and Elastoplastic Behavior of Metal Matrix Composite Materials
Authors: Tang Tian , Yu Wenbin
Published: May 2009

The focus of this paper is to develop a micromechanics model based on the variational asymptotic method for unit cell homogenization (VAMUCH) for predicting of the initial yielding surface, overall instantaneous moduli, and elastoplastic behavior of metal matrix composites. Considering the size of the microstructure as a small parameter, we can formulate a variational statement of the unit cell through an asymptotic expansion of the energy functional. To handle realistic microstructures, we implement this new model using the finite element method. For model validation, we used a few examples to demonstrate the application and accuracy of this theory and the companion code.
An Alternative Approach for Teaching Turbulent Flow
Authors: Fakheri Ahmad
Published: May 2009

Teaching of turbulence in undergraduate and early graduate level fluid mechanics and heat transfer courses is a difficult undertaking. The approach taken in typical texts requires the students to accept a number of basic concepts without much quantitative justifications. This paper presents an alternative approach, one in which most of the salient features of the turbulent flow are derived by using numerical solutions and experimental results, as opposed to simply having them presented. In this approach, Prandtl’s mixing length model is used to obtain the velocity distribution for fully developed pipe flow. By comparing the numerical calculations with the experimental results, students determine the value of κ that best fits the experimental data on their own. In addition, deficiency of the mixing length in the transition region is shown. It is also shown that other models like Van Driest’s do a better job. The Logarithmic Law of the wall as well as 7th power law are also proven. The different models are used to determine the friction factor for pipe flow and the results are compared with the values obtained from the Moody diagram.
Investigation of Dynamics and Vibration of PIG in Oil and Gas Pipelines
Authors: Durali Mohammad , Fazeli Amir , Nabi Ali
Published: May 2009

In this paper, the transient motion of an intelligent Pipe Inspection Gauge (PIG) while moving across anomalies inside a typical gas/oil pipeline has been investigated. The pipeline fluid has been considered as isothermal and compressible. In addition, the pipeline itself has also been considered to be flexible. The fluid continuity and momentum equations along with the 3D dynamic equations of motion of the pig comprise a system of coupled dynamic differential equations which have been solved numerically. Pig’s position, orientation and velocity profiles as well as upstream and downstream fluid’s pressure waves are presented as simulation results which provide a better understanding of the complex behavior of pig motion through pipelines. This study has been conducted as a part of the design procedure for the Pig which is currently under construction.
Recognition of Human Intentions Using Bayesian Artificial Intelligence
Authors: Tse R. , Seet G. , Sim S. K.
Published: May 2009

Controlling a robot to perform a task is more difficult than commanding a human. A robot needs to be preprogrammed to perform a task. This is achieved by providing the robot with a complete set of step-by-step commands from the beginning till the end. In contrast, to a human, recalling an experience when he was instructed with the same command in a similar situation, a human would be able to guess what intention behind such a command is and could then behave cooperatively. Our objective is to equip the robot with such a capability of recognizing some simple human intentions required of a robot, such as: moving around a corner, moving parallel to the wall, or moving towards an object. The cues used by the robot to make an inference were: the odometer and laser sensor readings, and the human operator’s commands given. Using the Maximum-Likelihood (ML) parameter learning on Dynamic Bayesian Networks, the correlations between these cues and the intentions were modeled and used to infer the human intentions in controlling the robot. From the experiments, the robot was able to learn and infer the above mentioned intentions of the human user with a satisfying success rate.
Geometric Prediction of Curvature Extrusion for Aluminum Alloy Sections
Authors: Joe Y. J. , Lee S. K. , Kim B. M. , Kang C. G. , Oh K. H. , Park S. W.
Published: May 2009

Bent profiles are used in the manufacture of many kinds of products such as transport apparatus and mechanical parts for reduction of production cost and weight. The conventional processes for bent profiles involve a successive extrusion, stretching, and bending of the profiles. Conventional bending methods can not meet demands for precision and cost-effective production in some cases, due to cross sectional deformation, irregular decrease of tube wall thickness and a complication of the process design. There are some researches regarding bending of extruded aluminum profiles during the extrusion process. However, there is no study about the exact prediction of the final various curved profiles. This paper presents the achievements of control of bending tool in the curvature extrusion for a bent profile with various radii. A geometric model, which is the relationship between the bending tool velocity and the extrusion velocity, is proposed to predict the exact geometry of the various curved profile using FE simulation. Experiments were conducted to verify the effectiveness of the proposed geometric model for a vehicle bumper with the various outline radii from 1900mm to 2200mm. The overall correlation between experiments and theoretical results is good. It is, therefore, concluded that the present method provides an efficient means for the variable curvature extrusion process.
Fundamental Wave Process in Narrow Tubes for Micro Wave Rotor Application
Authors: Okamoto K. , Nagashima T.
Published: May 2009

In the miniaturization of wave rotors, one of the important points in its design is how to decide the passage length. Longer passage allows slower rotor speed, while it will yield larger wall friction effect. In the present study, shock wave propagation process in narrow tubes was carefully observed and discussed experimentally and numerically. Shock wave visualization, velocity measurement and stagnation pressure measurements were carried out with two test sections of different lengths in this experiment. In the visualization, the whole propagation process of shock waves was observed clearly in both test sections, so that it was confirmed that the dissipation effect of shock waves or the interaction between shock waves and boundary layer apparently are not dominant. It was also confirmed by Laser Doppler Anemometry measurement that the flow velocity induced by the shock wave traveling shows a good agreement with numerical results.
A Stochastic Analysis on the Effects of Restraint Component Characteristics on Injury Numbers at Frontal Crash Tests
Authors: Kim Taewung , Kim Hyungho , Jeong Hyun-Yong , Jin Wook
Published: May 2009

In general, crash test data have a comparatively large variation because of the complexity of the tests. However, only limited numbers of crash tests are usually conducted to assess the safety performance of a vehicle due to monetary and time limitation. Thus, it is necessary to control factors which cause the variation in the test data to have consistent crash test results and to correctly assess the safety performance of a vehicle under development. In this study, a MADYMO (MAthematical DYnamic MOdeling; an engineering software tool developed by TNO that allows users to design and optimize occupant safety systems) model was validated deterministically to result in similar head, chest, pelvis deceleration pulses and belt load pulses to those from tests, and it was also validated stochastically to result in similar mean and standard deviation values of HIC15 and 3 msec clip. By reducing the standard deviation of major factors which might cause the variation in the injury numbers, the reduced standard deviation of the injury numbers could be determined by conducting a stochastic analysis using the validated MADYMO model. The sensitivity of the standard deviation of the injury numbers to that of the major factors was calculated in order to determine the major factors which may cause the variation of the injury numbers the most. The sensitivity of the injury numbers implies that the variation in the air bag permeability and the critical load of the loadlimiter should be well controlled in order to reduce the variation in HIC15 and 3 msec clip, respectively.
Thermo Electrical Characterization of Pyrolyzed Polyfurfuryl Alcohol Nanowires
Authors: Samuel B. A. , Haque M. A.
Published: May 2009

We present experimental results on the electrical characteristics of carbonaceous nanowires using micro-fabricated two point electrodes. The nanowires (diameter varying from 150 nm to 250 nm, and tens of microns in length) are synthesized by the pyrolysis of polyfurfuryl alcohol (PFA) nanowire precursors. The microstructure of the pyrolyzed nanowire shows predominantly amorphous carbon structure with an increasing degree of graphitization reported in literature at higher pyrolysis temperatures. The effect of the nanowire surface temperature on its resistivity is also characterized. We observe temperature dependence in resistivity and decreasing resistance with increasing temperature which is evidence of semiconducting nature of these carbonaceous nanowires.
Relationship Between Rheological Properties and Microstructure of Polypropylene/Organic Montmorillonite Nanocomposite Compounded by Twin Screw Extruder
Authors: Jiang Guo , Huang Han-Xiong
Published: May 2009

Polypropylene (PP)/organic montmorillonite (OMMT) nanocomposite was compounded in a twin-screw extruder. The objective is to investigate the relationship between rheological properties and microstructure of the nanocompsite. The samples were taken along the screws. Effect of feeding rate on the dynamical rheological property development and microstructure of samples was investigated. The yield stress of nanocomposite was obtained using steady-state shear sweep. The intercalated structure was probed by wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Rheological results showed that the complex viscosity of samples increased along the twin-screw extruder. In addition, with the decrease of feeding rate, the yield stress of nanocomposite increased and MMT was dispersed better in PP matrix. Finally, the relationship between dynamical rheological properties and the dispersed state of MMT was analyzed.
Run-Time Integration of Robotic Manipulators and Their Controllers
Authors: Proctor Fredrerick M. , Scrapper Christopher J. , Balaguer Benjamin
Published: May 2009

This paper describes an information model and interface by which a general purpose robotic manipulator can publish its kinematic- and dynamic parameters to enable real-time trajectory control. The motivation for the work was the control of various robotic manipulators in USARSim, an urban search and rescue simulation environment, wherein manipulators are dynamically introduced. The objective was to avoid a static description, such as a configuration file, in favor of real-time communication channels. Although the interface originated with simulations, it has been applied to real robotic manipulators, including serial- and parallel kinematics. The interface is being used as the basis for robot competitions in the RoboCup Rescue Simulation league, which provides a plug-and-play software environment for robots and the competing controllers.
Experimental Research of Combustion Chamber With Hybrid Burner and Variable Regulation of Primary Air
Authors: Vesely´ S. , Pary´zek S. , Vinogradov E. , Zakharov Y. , Soudarev A.
Published: May 2009

The environmentally friendly modification of gas turbine combustion chambers is a process for altering the structure of combustion, mainly in the primary zone in order to reduce the emission of NOx, CO, and solids into the atmosphere. The ecological modernization of gas turbines that are currently in operation is a continually topical subject because there are several thousand turbine units in Europe that do not meet current emission limits. At the same time, it can be expected that the emission limits for these turbines operating in the European Union will be reduced to NOx≤75 mg/m3, CO≤100 mg/m3 in working range of 40–100% of the gas turbine output after the year 2010. The authors have developed a new construction of a hybrid low-emission natural gas burner. Developmental work was performed both on one burner and also in a burner group consisting of seven hybrid burners. Results will be presented in this paper for model conditions for the atmospheric test rig and their re-calculation to the operational parameters on the real gas turbine. A conception with variable primary section combustion chamber geometry has been used to achieve low emissions in a wide range of gas turbine output allowing the organization of the combustion process with a constant gas/air mixing ratio coefficient. A prototype of a combustion chamber with a hybrid burner group with control of the primary air mass flow has been manufactured and tested in a 6 MW gas turbine operating in a gas pipeline compressor plant. The achieved emission characteristics will be presented and compared with precalculations. The experiments made on the real gas turbine have proven the possibility of meeting the target emission limit performance of NOx≤50 mg/m3, CO≤50 mg/m3. Other possibilities how to reduce harmful emissions for this burner type will be presented in this paper.
In-Situ Nanoscale Single Fiber Fragmentation Using Fluorescence Microscopy
Authors: Samuel B. A. , Haque M. A.
Published: May 2009

We use fluorescence microscopy to perform real time single fiber fragmentation experiments on individual PolyFurfuryl Alcohol (PFA) nanofibers embedded within a Poly DiMethyl Siloxane (PDMS) matrix. By using fluorescent nanofibers in an optically transparent matrix, fragmentation of the nanoscale fibers (even less than 400 nm) can also be easily visualized using fluorescence emission from the nanowires. When the composite specimen was loaded to saturation strain the fragment lengths distribution was observed to follow a two parameter Weibull frequency distribution. In addition, we also present a digital image correlation based technique to obtain localized strain (and hence stress) data based on the use of fluorescent nanoscale spatial markers.
Variation Analysis Toolbox for Non-Nominal Path Planning for Industrial Robots
Authors: Lindkvist Lars , So¨derberg Rikard , Carlson Johan S.
Published: May 2009

Industrial robots are frequently used in the manufacturing process. One important aspect in the manufacturing process design is to assure that there exists a collision-free assembly path for each part and subassembly including the assembly equipment, e.g. a robot. In order to reduce the need of physical verification the automotive industry uses digital mock-up tools with collision checking for this kind of geometrical assembly analysis. However, in real production, all equipment, parts and subassemblies are affected by geometrical variation, often resulting in conflicts and on-line adjustments of off-line generated assembly paths. This paper presents a variation analysis toolbox for path planning for industrial robots. This toolbox can help to avoid problems with on-line adjustments. The variation analysis includes the variation in joints and actuators in the robot and can also be used by robot manufacturers when designing new robots. A new tool for variation analysis of a robot path is presented. Also, variation analysis of the product at the assembly line is used to enhance the off-line generated assembly paths. With better knowledge of the variation in the robot and product we can allow the assembly path to reach closer to areas of low variation, while avoiding areas of high variation. The proposed approach is illustrated with test cases.
Asymptotic Construction of a Generalized Reissner-Mindlin Model for Multilayer Piezoelectric Plates
Authors: Liao Lin , Yu Wenbin
Published: May 2009

The variational asymptotic method is used to construct a generalized Reissner-Mindlin model for multilayer piezoelectric plates with faces surfaces or other surfaces parallel to the reference surface coated with electrodes. Without invoking a priori kinematic assumptions, we asymptotically split the original three-dimensional electromechanical problem into a one-dimensional through-the-thickness analysis and a two-dimensional plate analysis. The through-the-thickness analysis is implemented using the finite element method into the computer program VAPAS (Variational Asymptotic Plate and Shell Analysis). The resulting model is as simple as an equivalent single-layer, first-order shear deformation theory with accuracy comparable to higher-order layerwise theories. Numerical results of cylindrical bending problems for piezoelectric plates have been compared with 3D exact solutions to validate the present model.
Structural Vibration Reduction Optimization by Switch Shunting of Piezoelectric Elements
Authors: Ducarne J. , Thomas O. , Deu¨ J.-F.
Published: May 2009

This work deals with the damping of structural vibrations by means of Synchronized Switch Damping (SSD) techniques on piezoelectric elements. Piezoelectric patches are attached to the vibrating structure and connected to an electrical circuit that includes a switch. The latter allows to continuously switch the piezoelectric elements from an open-circuit state to a specific electric impedance, synchronously with the mechanical oscillations. The present study focuses on two goals: (i) the quantification of the added damping (ii) the optimization of the electric circuit parameters. The free and forced responses of one mode of the mechanical structure are studied in detail. The precise time response of the system is obtained with semi-analytical models for the two cases where the electrical impedance is a simple resistance or a resistance and an inductance. The added damping of the oscillations is estimated analytically. In all cases, it is found that the piezoelectric coupling coefficient has to be maximized in order to maximize the added damping. In the case of SSDI, an optimal value of the electric circuit quality factor is obtained.
Controller Development for an Automotive Shape Memory Alloy Actuator
Authors: Williams Eric A. , Elahinia Mohammad , Seigler Thomas M.
Published: May 2009

Shape memory alloy actuators are inherently nonlinear and require a robust control scheme to guarantee rapid tracking and sufficient position control performance. In this paper, a control scheme is developed for an automotive shape memory alloy actuator that is used to orient an external rear view mirror to match desired set-points. The formulation of appropriate models and control laws are presented. Experiments of the controller in a real-time environment are performed and results are presented.
Analysis of Optical Absorption in Silicon Nanowire Solar Cells
Authors: Hu Lu , Chen Gang
Published: May 2009

Nanowires and nanotubes can serve as electrodes for polymer and electrochemical photovoltaic cells [1,2] and building blocks in other novel optical devices [3,4]. Recently photovoltaic cells based on silicon nanowire arrays have been suggested as a promising candidate for solar energy harvesting [5]. The advantage of the silicon-nanowire photovoltaic cell lies in its short collection length for excited carriers, resulting in significant improvement in carrier collection efficiency. The optical absorption characteristics of nanowire arrays in the solar spectrum, one of the key factors that determine the efficiency of solar cells, remain unclear. A detailed analysis of the optical absorption will help the design and optimization processes of the silicon nanowire solar cells. In this letter, we numerically analyze the effects of wire diameter, length and filling ratio on the optical absorption of periodic nanowire arrays, and compare the cases with the results of silicon thin films. We found that, in comparison to thin films, nanowire array based solar cells have an intrinsic antireflection effect that increases absorption in short wavelength range.
Control of a Digital Micromirror Device Using Input Shaping
Authors: Jammoussi H. , Choura S. , Abdel-Rahman E. M. , Arafat H. , Nayfeh A. , Chaabane G.
Published: May 2009

In this paper, an open-loop control strategy is proposed for maneuvering the angular motion of a Digital Micromirror Device (DMD). The control law is based on a micromirror model that accounts for both bending and torsion motions. The model characterizes two DMD configurations: with and without contact with the substrate. The device is actuated using an electrostatic field which is a nonlinear function of the states and input voltage. The proposed control strategy is a Zero Vibration (ZV) shaper. It overshoots the DMD to its desired final angle by appropriately varying two independent input voltages. Actuating voltages and switching times are determined to maneuver the DMD from −10° to +10° tilt angles while reducing the residual vibrations.
Analysis of Multiple Rigid-Line Inclusions for Application to Bio-Materials
Authors: Pingle Pawan S. , Gorbatikh Larissa , Sherwood James A.
Published: May 2009

Hard biological materials such as nacre and enamel employ strong interactions between building blocks (mineral crystals) to achieve superior mechanical properties. The interactions are especially profound if building blocks have high aspect ratios and their bulk properties differ from properties of the matrix by several orders of magnitude. In the present work, a method is proposed to study interactions between multiple rigid-line inclusions with the goal to predict stress intensity factors. Rigid-line inclusions provide a good approximation of building blocks in hard biomaterials as they possess the above properties. The approach is based on the analytical method of analysis of multiple interacting cracks (Kachanov, 1987) and the duality existing between solutions for cracks and rigid-line inclusions (Ni and Nasser, 1996). Kachanov’s method is an approximate method that focuses on physical effects produced by crack interactions on stress intensity factors and material effective elastic properties. It is based on the superposition technique and the assumption that only average tractions on individual cracks contribute to the interaction effect. The duality principle states that displacement vector field for cracks and stress vector-potential field for anticracks are each other’s dual, in the sense that solution to the crack problem with prescribed tractions provides solution to the corresponding dual inclusion problem with prescribed displacement gradients. The latter allows us to modify the method for multiple cracks (that is based on approximation of tractions) into the method for multiple rigid-line inclusions (that is based on approximation of displacement gradients). This paper presents an analytical derivation of the proposed method and is applied to the special case of two collinear inclusions.
Modeling of a Hydraulic Hybrid Pump Motor for Evaluation of Vibration Characteristics
Authors: Schroeder Christopher C. , Motlagh Amin Mohaghegh , Nguyen The M. , Elahinia Mohammad H.
Published: May 2009

This paper presents a simulation model of a hybrid hydraulic circuit including a swash plate pump motor (PM) applicable for mid-sized passenger vehicles. The model is developed using AMESim with a co-simulation of MATLAB/Simulink®. The AMESim model is used to extract the forces and moments induced by the hydraulic circuit that are transmitted to the chassis of the vehicle. Various mounts modeled as simple spring-dashpot systems in MATLAB/Simulink® are employed to dynamically link the hydraulic circuit to the vehicle chassis. The focus of this research is to study and evaluate the levels of vibration associated with the hybrid hydraulic circuit. This information will be used to provide a means of evaluating different isolation techniques to attenuate the forces caused by the hydraulic system. Preliminary results of the model are presented and will be validated in a developing research effort.
Controlling Nanoparticle Delivery in Hyperthermia for Cancer Treatment: In Vitro Experimental Study
Authors: Salloum M. , Ma R. , Zhu L.
Published: May 2009

Magnetic nanoparticle hyperthermia attracts growing research interest aiming to develop a localized heating approach for malignant tumors treatment. In this method, magnetic nanoparticles delivered to the tissue or blood vessels induce localized heating when exposed to alternating magnetic field, leading to irreversible thermal damage to the tumor. Controlling the heat distribution and temperature elevation in such treatment is still an immense challenge in clinical applications. In this study, we inject nanofluid into agarose gel to study nanofluid transport in the extracellular space of biological tissue. Nanofluid distribution in the gel is examined via digital images of the nanofluid spreading in the gel. By adjusting gel concentrations and injection flow rates, we expect to identify an idealized particle delivery strategy for achieving spherical shaped nanoparticle dispersion. Thermocouples are then inserted into the gel to measure the initial temperature rises at various locations in the gel to obtain the specific absorption rate (SAR). The preliminary results have demonstrated that a spherical shaped particle deposition is possible with a relatively low injection rate of the nanofluid and a technique that minimizes the air gap surrounding the injection needle. The distribution of energy absorption (SAR) implies that the nanoparticle distribution in the gel is not uniform. High concentration of nanoparticles is observed close to the center of the injection site. Based on the particle deposition pattern, a theoretical model will be developed in the future to simulate the temperature distribution in tissue during nanoparticle hyperthermia treatment. The simulated results will help provide guidance for designing a better treatment protocol in future clinical application.