bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Control With Internal Model for High Precision Motion Control
Authors: Lin Chi-Ying , Tsao Tsu-Chin
Published: May 2009

This paper proposes an adaptive control scheme that minimizes the Least-Mean-Square value of the plant output while meeting the constraint of canceling deterministic exogenous signals generated by a priori known dynamics. This scheme may be applied to a broad range of application where the exogenous input signals to the plant contain both deterministic and stochastic components. The adaptive control includes both feedback and previewed feedforward actions. In both actions, the deterministic signal model is included as a constraint for the dynamics from the external input to the plant output by solutions of a Bezout identity. The proposed scheme is applied to a fast acting piezoelectric actuator to generate precise dynamic motion profiles. Experimental results are presented to demonstrate the effectiveness of the proposed adaptive control scheme.
Examining the Role of Free Carrier Concentration on the Phonon Lifetimes in GaN Using Raman Spectroscopy
Authors: Beechem Thomas , Graham Samuel
Published: May 2009

The lifetimes of polar optical phonons are known to affect the electrical and thermal performance of gallium nitride (GaN) based devices. Utilizing the energy-time uncertainty relation, this study investigates these lifetimes using Raman spectroscopy for a series of samples having free carrier concentrations ranging from 1.24e18 to 3e17 cm−3. By measuring across the typical operating temperatures of these devices, the mechanisms responsible for scattering of 5 separate optical modes are elucidated. It is found that phonon-carrier interaction directly determines the lifetime of the polar optical A1(LO) mode while indirectly influencing the modes into which this longitudinal phonon decays, namely, E1 and A1(TO). Thus understanding the entire phonon energy cascade is vital both for management of the so called “hot phonon” effect as well as modeling of carrier-phonon interactions.
Mechatronic Control Engineering: A Problem Oriented and Project Based Learning Curriculum in Mechatronic
Authors: Pedersen Henrik C. , Andersen Torben O. , Hansen Michael R.
Published: May 2009

Mechatronics is a field of multidisciplinary engineering that not only require knowledge about different technical areas, but also insight into how to combine technologies optimally, to design efficient products and systems. This paper addresses the group project based and problem-oriented learning approach in relation to a mechatronic education, which makes it possible for the student to get in-depth skills in the area of mechatronics very fast. The trends and applications of mechatronic engineering and research are illustrated. Control engineering plays a central role in this context, where the well established methods from control engineering form very powerful techniques in both analysis and synthesis of mechatronic systems. The necessary skills for mechatronic engineers are outlined followed up by a discussion on how problem oriented project based learning is implemented. A complete curriculum named Mechatronic Control Engineering is presented, which is started at Aalborg University, Denmark, and the content of the semesters and projects are described. The projects are all characterized by the use of simulation and control for the purpose of analyzing and designing complex commercial systems of a strongly dynamic nature.
On the Analysis of Experimental Data for External Gear Machines and Their Comparison With Simulation Results
Authors: Vacca Andrea , Franzoni Germano , Casoli Paolo
Published: May 2009

This paper deals with the simulation of hydraulic gear machines, focusing on the validation of simulation models and on the comparison between numerical results and experimental data, concerning both steady and unsteady conditions. First authors give a brief overview on the simulation tool HYGESim, which has been presented and discussed in several previous papers. Afterwards, the attention shifts on the analysis of the simulation results for the case of a stock gear pump. Regarding steady state characteristics, the paper shows how HYGESim is able to accurately reproduce the operation of the analyzed pump, in terms of flow, pressures and efficiency maps. Regarding unsteady simulations, namely the delivery pressure ripple, the paper highlights the significant effort done by the authors in order to achieve experimental data clear and suitable for the comparison with simulation results. In fact, the peculiarities of common measuring systems (in particular of the load apparatus and the sampling methods) are often difficult to reproduce numerically: frequently different acceptable assumptions in the numerical model lead to remarkable discrepancies in simulated results. For this purpose, the authors developed a measuring device mainly focused on the easy reproducibility in the simulation environment. Furthermore, an original technique for processing unsteady data (pressure and flow ripples) is proposed, allowing to achieve comparable data indifferently of the adopted sampling method and of the data origin (experimental or numerical). In the final part of the paper, pressure ripple simulations and test results (obtained with the described measuring system and analyzed with the described technique) are presented and compared.
Recent Developments in Single-Phase Transient Forced Convection in Channels: A State-of-Art-Review
Authors: Yener Yaman , Saran Salih
Published: May 2009

Many analytical and experimental studies, involving both liquids and gases, have been carried out to gain a better understanding of transient fluid flow and forced convection heat transfer phenomena in macro and micro channels over the last half century. Starting with the early contribution and including Professor S. Kakac¸’s seminal studies, a state-of-the-art review of the recent developments in the study of transient thermal response of channel flows is given. The parallel-plate channel and the circular tube, which are the two commonly encountered geometries in practice, are considered with both laminar and turbulent flows.
Solid-State Foaming of Polycaprolactone (PCL)
Authors: Wang Hai , Li Wei , Kumar Vipin
Published: May 2009

Polycaprolacton (PCL) is a synthetic biodegradable polymer that is widely used in tissue engineering related studies. It is a semi-crystalline polymer, and has a glass transition temperature (Tg) of −60°C and a melting temperature of 60°C. In this paper, we report on the progress in creating porous PCL foams using the solid-state foaming process. The objective of this study is to examine the foam-ability of PCL using room temperature saturation. PCL specimens were made using compression molding. A “quenching” process was introduced to manipulate the crystallinity of PCL samples. CO2 was used for gas saturation. The effects of saturation pressure and foaming temperature were studied. The created microstructures were characterized using scanning electron microscopy (SEM). The preliminary results have shown that microstructures with pores on the scale of hundreds of nanometers were generated.
Measurement of 3-D Orientation and 3-D Orientation Tensors in Polymer/Nanofiber Composites
Authors: Mahboob Monon , Bechtel Stephen E.
Published: May 2009

We present a novel method to compute the three dimensional orientation tensors of carbon nanofibers in CNF/polymer composites. Performance properties of nanofiber composites are significantly affected by fiber orientation patterns. So an accurate description of the fiber orientation is necessary to validate models relating processing technique and properties of the final composites. Orientation tensors and probability distribution functions (PDF) are commonly used to describe orientation patterns. But physical dimensions of nanofibers and the imaging technique (Transmission Electron Microscopy, TEM) make all currently available methods of image analysis useless to accurately computing these descriptions in 3-dimensions. In this study TEM sections are cut with specific thickness and angle that result in majority of the fibers being cut at both ends. Fiber projection dimensions measured from this special section provide the complete three dimensional orientation of each fiber. This method is benchmarked by using simulated 3D samples in AutoCAD.
Pressure Based Prediction of Spray Cooling Heat Transfer Coefficients
Authors: Some Thierry , Lehmann Eckhard , Sakamoto Hitoshi , Kim Jungho , Chung Jin Taek , Steinthorssen Erlendur
Published: May 2009

An important goal of spray cooling research is the ability to predict local heat transfer coefficient from the spray hydrodynamics. It is postulated in this work that the local pressure is the controlling parameter for local heat transfer coefficient. To test this hypothesis, local pressure and heat transfer data were obtained for a 1×1, 1×2, and 2×2 arrays of hollow cone sprays at two pressures and three standoff distances. A correlation between the pressure and heat transfer coefficient was determined, then used to “predict” the heat transfer coefficient from the pressure data. The local variations in heat transfer coefficient were captured well using this technique, and the area-averaged heat transfer coefficient could be predicted within 12.6%. The technique needs to be verified with different nozzles and fluids over a wider range of conditions.
The Impact of Liquid Properties of Edible-Oil Diesel Fuel on the In-Cylinder Combustion Process
Authors: Boulanger Joan , Neill W. Stuart , Liu Fengshan , Jiang Lei-Yong
Published: May 2009

Pure edible oils may be used as a diesel fuel. They are nevertheless likely to produce deposits harmful to the engine. The liquid properties have been identified as a major issue but the details of the physical process leading to deposits are not well understood. This paper deals with simulations of a single-cylinder research diesel engine using virtual fuels which show the effects of different liquid properties. The aim is to investigate the impact on the in-cylinder processes of each property change from a conventional alkane to a fatty acid. The critical temperature, which makes fatty acid much less volatile than conventional diesel, has the biggest impact. It strongly delays the release of fuel into the gas phase and extends the combustion time. The effects of droplet break-up, heating and density are marginal. Globally, a longer survival time of droplets tends to spread the combustion and rich mixture zones as well as increase the probability of wall wetting. The swirl motion is likely to expose the droplets to the cooler cylinder walls, which leads to further problems in vaporizing the fuel and completing the combustion process. The findings may be used to explain carbon deposits and lubricating oil contamination.
Computational Simulation of Non-Newtonian Blood Flow in Carotid Bifurcation for Investigating the Various Rheological Blood Models
Authors: Jahanyfard E. , Firoozabadi B. , Goodarzvand Chegini A.
Published: May 2009

One of the leading causes for death after heart diseases and cancer in all over the world is still stroke. Most strokes happen because an artery carrying blood from the heart to the brain is clogged. Most of the time, as with heart attacks, the problem is atherosclerosis, hardening of the arteries, calcified build up of fatty deposits on the vessel wall. The primary troublemaker is the carotid artery, one on each side of the neck, the main thoroughfare for blood to the brain. In this study, the fluid dynamic simulations were done in the carotid bifurcation artery for studying the formation of atherosclerosis, and shear thinning behavior of blood as well as Newtonian comportment was studied. Under the steady flow conditions, Reynolds numbers representing the steady flow were under 1700. A comparison between rheological models for investigation each non-Newtonian model was carried out, velocity and wall shear stress distributions and its effect on developing atherosclerosis was studied; also the effect of non-Newtonian entrance length through this problem was exhibited.
Multi-Pulse Chaotic Motion for a Non-Autonomous Buckled Plate by Using the Extended Melnikov Method
Authors: Zhang Wei , Zhang Jun-Hua , Yao Ming-Hui
Published: May 2009

The multi-pulse Shilnikov orbits and chaotic dynamics for a parametrically excited, simply supported rectangular buckled thin plate are studied by using the extended Melnikov method. Based on von Karman type equation and the Galerkin’s approach, two-degree-of-freedom nonlinear system is obtained for the rectangular thin plate. The extended Melnikov method is directly applied to the non-autonomous governing equations of the thin plate. The results obtained here show that the multipulse chaotic motions can occur in the thin plate.
Assessment of Thermoelectric Module With Nanofluid Heat Exchanger
Authors: Agwu Nnanna A. G. , Rutherford William , Elomar Wessam , Sankowski Brian
Published: May 2009

For applications such as cooling of electronic devices, it is a common practice to sandwich the thermoelectric module between an integrated chip and a heat exchanger, with the cold side of the module attached to the chip. This configuration results thermal contact resistances in series between the chip, module, and heat exchanger. In this paper, an appraisal of thermal augmentation of thermoelectric module using nanofluid-based heat exchanger is presented. The system under consideration uses commercially available thermoelectric module, 27nm Al2O3 - H2O nanofluid, and a heat source to replicate the chip. The volume fraction of nanofluid is varied between 0 to 2%. At optimum input current conditions, experimental simulations were performed to measure the transient and steady-state thermal response of the module to imposed isoflux conditions. Data collected from the nanofluid-based exchanger is compared with that of deionized water. Results show that there exist a lag-time in thermal response between the module and the heat exchanger. This is attributed to thermal contact resistance between the two components. A comparison of nanofluid and deionized water data reveals that the temperature difference between the hot- and cold-side, ΔT = Th − Tc ≈ 0, is almost zero for nanofluid whereas ΔT > 0 for water. When ΔT ≈ 0, the contribution of Fourier effect to the overall heating is approximately zero hence enhancing the module cooling capacity. Experimental evidence further shows that temperature gradient across the thermal paste that bonds the chip and heat exchanger is much lower for the nanofluid than for deionized water. Low temperature gradient results in low resistance to the flow of heat across the thermal paste. The average thermal contact resistance, R = ΔT/Q, is 0.18 and 0.12 °C/W, respectively for the deionized-water and nanofluid. For the range of optimum current, 1.2 ≤ current ≤ 4.1Amp, considered in this study, the COP ranges between 1.96 and 0.68.
Natural Convective Heat Transfer From an Isothermal Vertical Cylinder With an Exposed Upper Surface Mounted on a Flat Adiabatic Base
Authors: Oosthuizen Patrick H.
Published: May 2009

Natural convective heat transfer from an isothermal vertical cylinder which has an exposed horizontal top surface has been numerically studied. The exposed upper surface is maintained at the same temperature as the cylindrical vertical wall of the cylinder. The cylinder is mounted on a flat horizontal adiabatic base plate. In some circumstances the heat transfer rate from the exposed upper surface can be neglected compared to that from the curved surface of the cylinder and in some circumstances the heat transfer rate from the curved surface can be adequately predicted using vertical flat plate equations, i.e., by ignoring curvature effects. The flow has been assumed to be axisymetric about the vertical cylinder axis. The flow has also been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the governing equations, these equations being written in terms of dimensionless variables, the solution being obtained using a commercial finite element method based code, FIDAP. Because of the applications that motivated this study, results have only been obtained for Pr = 0.7. A wide range of the other governing parameters have been considered. The conditions under which the heat transfer from the exposed upper surface can be neglected compared to that from the cylindrical wall in the evaluation of the mean Nusselt number has been deduced and the conditions under which curvature effects can be ignored in evaluating the mean Nusselt number for the curved surface of the cylinder have been investigated.
Trajectory Control of an ASEA IRb-6 Manipulator With Singularity Configuration
Authors: Lang Haoxiang , Wang Ying , de Silva Clarence W.
Published: May 2009

In this paper, the trajectory control of an AESA RIb-6 manipulator is addressed. In order to solve the problem of singular inverse kinematics, the normal form approach is employed for computing the joint trajectories from the desired trajectory in the task space. The basic idea of the normal form approach is introduced, and the detailed algorithm is presented and verified. Based on the inverse kinematics results, a group of proportional-integral-derivative (PID) controllers are developed to control the manipulator trajectory. Simulation results are presented which show that the PID controllers are unable to track the desired trajectory if measurement noise exists. In order to overcome the noise problem, an LQG (Linear Quadratic Gaussian) controller is designed for the trajectory control of the manipulator. The simulation results show that the LQG controller exhibits excellent tracking performance and robustness in the presence of measurement noise.
Design of Manifold for Nanofluid Flow in Microchannel
Authors: Senta Manish , Agwu Nnanna A. G.
Published: May 2009

This paper presents a study of nanofluid flow through microchannel. Its focus is on the design and optimization of microchannel assembly with emphasis on the design of manifold or jacket. The test setup consists of ninety-nine 120μm×120μm×20mm channels, nanofluid flow loop, heat source, thermal sensors and pressure transducers. Flow of nanofluid through the channels is regulated using a peristaltic pump. Numerical iterations were performed to study the effect of inlet and exit flow locations and shape of the jacket on uniform distribution of nanofluid in the channels. Based on the numerical results, it is recommended that for uniform flow distribution in the microchannel, a trapezoidal shaped jacket should be used. The results obtained from this work provided an insight on the variation of the flow patterns within the channel. It reveals that flow uniformity among the channels largely depends on the shape of the manifolds, length and location of inlet and outlets, and the inlet flow rate.
The Effect of Time Delay of the Semi-Active Dampers on the Performance of On-Off Control Schemes
Authors: Eslaminasab N. , Golnaraghi M. F.
Published: May 2009

With the new advancement in the vibration control strategies and controllable actuator manufacturing, the semi-active actuators (dampers) are finding their way as an essential part of vibration isolators, particularly in vehicle suspension systems. The currently available semi-active damper technologies can be divided into two main groups. The first uses controllable electromagnetic valves. The second uses magnetorheological (MR) fluid to control the damping characteristics of the system. Despite different semi-active control methods and the type of actuators used, one important practical aspect of all hydro-mechanical computer controlled systems is the time response (delay). The longest time response (delay) is usually introduced by the actuator (in this case, controllable actuator) in the system. This paper investigates the effect of time response in an on-off controlled suspension system using semi-active dampers. Numerical simulations and analytical techniques are deployed to address the issue. The performance of the system due to the time response is then analyzed and discussed. Specifically, the effect of the time response on the performance of a quarter car suspension system controlled by conventional on-off control strategies such as Skyhook and Rakheja-Sankar (R-S) is studied. Finally, the test results measuring time response in a newly developed semi-active actuator (namely, an external solenoid valve damper) is presented. Based on the real data and numerical simulations, the performance of a one degree of freedom quarter car system using this actuator is presented.
Fracture Behavior of Polyurethane Foams
Authors: Jin Helena , Lu Wei-Yang , Hong Soonsung , Connelly Kevin , Korellis John
Published: May 2009

Due to their high energy absorption capabilities, polyurethane (PU) foams have been widely used in many applications. The mechanical behavior of Polyurethane (PU) foams has been attracting the attention from engineers and researchers. But most of work was to study the compressive behavior of PU foams. Very little knowledge is available about the fracture behavior of the PU foams. In this paper, single edge notch bend (SENB) and single edge notch tension (SENT) tests are conducted to study the mode-I fracture behavior of a rigid closed cell PU foam, PMDI 20, with a nominal density of 20 pcf (320 kg/m3). The stress intensity factor KIC is calculated from the loading curves. The displacement and strain field around the crack tip is obtained using digital image correlation (DIC) technique.
Sensor Networks for In-Situ Failure Identification in Woven Composites Throughout Impact
Authors: Garrett Ryan , Peters Kara , Zikry Mohammed A.
Published: May 2009

In this study, the development of embedded fiber Bragg grating (FBG) sensor networks within composite materials is investigated. Various densities of optical fibers were embedded within two-dimensional woven composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Cross sectional optical micrographs of the specimens were also used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Multiple FBG sensors were serially multiplexed together to create a single fiber sensing network capable of monitoring damage for each impact event. Residual strain information was gathered through strain distributions along the FBG sensors to map out the near-field and far-field regions with respect to the impact location. The resulting data will be used to better monitor and predict damage in the composite system when combined with global response data from the laminate itself.
Experimental Study of Solder Joint Reliability for External Heat Sink Installation on FCBGA
Authors: Kao Nicholas , Lai Jeng Yuan , Wang Yu Po , Hsiao C. S.
Published: May 2009

As the increasing power consumption for electronic devices, thermal management on board level becomes a challenge to manufacturers who are integrating more functionality and components into a board in order to the high performance products in this competitive market. To drive such high level products requires more power consumption and consequently arises a thermal risk of system malfunction because of overheating to chips. A common implement for thermal solution is a heat sink installed on package via clip mechanism that maintained a compressive force to clamp the heat sink and board to fulfill this thermal dissipation demand. But this compressive force along with operation temperature will arise solder joint risk and potentially induce the function failed due to the clamped force may potentially arise solder ball creep after long operating time and damage the connection failed of solder ball and PCB. This paper describes the experimental setup and test results to evaluate the solder joints creep behavior in the presence of clamped force and operation temperature. An External Heat Spreader Flip Chip BGA (EHS-FCBGA) was tested for several weeks under 85°C with a compressive force. The different levels of uniform compressive forces were applied with 25kg and 50kg metal blocks on EHS-FCBGA to simulate the clamped force. All test vehicles were placed in an oven at 85°C for several weeks to accelerate thermal aging condition and measured solder ball collapsed shapes and do open-short test at the end of every two weeks.
Equilibrium Structure of a 1-DOF Electrostatic MEMS Model With Parasitics
Authors: Maithripala D. H. S. , Kawade B. D. , Wickramasinghe I. P. M. , Berg J. M. , Dayawansa W. P.
Published: May 2009

Feedback control of electrostatic microelectromechanical systems (MEMS) is significantly complicated by the presence of parasitic surfaces. This note considers the stabilization of a one-degree-of-freedom (1-DOF) piston actuator with capacitively-coupled parasitics. Previous work by the authors has shown how, in the absence of parasitics, any feasible equilibrium point of this system may be made globally asymptotically stable using passivity-based control. However if parasitics are present this nominal closed-loop system may be destabilized by capacitive coupling, through a phenomenon called charge pull-in. This note shows how the nominal controller formulation may be modified to eliminate multiple equilibria. If the movable electrode is completely screened from the parasitic electrode by the control electrode, the unique equilibrium is globally asymptotically stable. Otherwise, though the desired equilibrium is still unique, its region of attraction may be finite and the equilibrium may lose stability through a Hopf bifurcation.
Comparison of Performance of Aluminum and Titanium Heat Pipes
Authors: Carbajal Gerardo , Peterson G. P. , Sobhan C. B.
Published: May 2009

An investigation of the effect of using aluminum and titanium as the case material in a flat heat pipe (FHP) configuration is presented. In the heat pipe analyzed, the working fluid and the wick material were water and nickel foam, respectively. Identical configurations, dimensions, boundary and initial conditions were assumed in the numerical analysis for the two case materials. The flat heat pipe was subjected to a non-uniform heat input in the evaporator for a short period of time, and the condenser was cooled by natural convection and radiation effects. In both cases, non-uniform temperature distributions with peak values at the center of the evaporator side were observed. The titanium heat pipe gave a comparatively higher temperature range. The low thermal conductivity of titanium was understood to be responsible for the elevated temperature at the evaporator side. Consequently, it was also verified that for a low temperature range of operation and a short period of transient heat input, the aluminum heat pipe presented a better performance than the one with titanium as the case material. Discussions of the selection of the working fluids for the heat pipes based on the dimensionless merit number and other quantitative and qualitative parameters are also presented.
Warpage Reduction Through Robust Engineering of a Thin-Walled Injection Molded Component
Authors: Sobolak Steven J. , Jawad Badih A.
Published: May 2009

An L18 Taguchi experiment was used to determine the robust processing control factor settings to maximize dimensional stability and reduce warpage for a 3-dimensional thin-walled injection molded component. The robust control factor settings were determined for seven control factor settings and also included three noise factors. The noise factors were: wall thickness, glass fiber content and production cycle pull point. A scientific molding technique where an on-line rheology study was performed to determine the relative viscosity versus effective shear rates was used to determine the injection speed settings. The proper shot size was also established for each experiment. A laser measuring system was used to analyze the entire component and to determine the shrinkage rates and warpage of the component. A warpage index was created to determine the entire warpage of the component.
Anisotropy Study of a Constrained Thin Walled Component Using a Range of Processing Control Factors
Authors: Sobolak Steven J. , Jawad Badih A.
Published: May 2009

An anisotropy study was performed on a constrained thin-walled injection molded component using measurements made from a laser measuring system. Wall thickness and material glass fiber concentration were varied to determine their effects on parallel and perpendicular shrinkage rates. Several ranges of the processing control factors were used in the study. The shrinkages were determined and were described as a function of glass fiber concentration and wall thickness. The shrinkage ratio (a ratio representing the parallel shrinkage rate divided by the correlative perpendicular shrinkage rate) was used to investigate the influence of wall thickness and glass fiber (G.F.) concentration on shrinkage.
Experiments on the Flow and Heat Transfer in Fine Pitch Parallel Plate Heat Sinks With Top Inlet Side Exit Flow
Authors: Ortega-Gutierrez Felipe E. , Ortega Alfonso
Published: May 2009

Detailed temperature and pressure measurements in high aspect ratio parallel plate fin heat sinks were made in a Top Inlet Side Exit (TISE) experiment configuration without top bypass flow. Air flow was supplied to the top of the heat sink using a rectangular jet nozzle with three different jet nozzle widths, Wj. The study covered five jet velocities and three different jet nozzle width to heat sink length ratios. Static pressure measurements were made along the spanwise centerline inside the heat sink and on the mounting plate outside the heat sink. The measurements were used to study the influence of the jet impinging on the top of the heat sink on the loss coefficient of the heat sink. It was found that the overall loss coefficient was dependent on Re, Wj, the fin spacing, b, and the jet nozzle width relative to the heat sink length, Wj/L. Temperature measurements were made to study the total thermal resistance with no base heat spreading. An ad hoc model was used to predict the total thermal resistance of the heat sink in this complicated flow. The model modifies the total cooled area of the fin as a function of jet width and heat sink geometry. Good agreement was found with the experimental data for the cases of Wj/L = 1.0 and 0.5. The model does not work well in the case of Wj/L = 0.25.
Chaos Control in Continuous Mode of T-AFM Systems Using Nonlinear Delayed Feedback via Sliding Mode Control
Authors: Sadeghian Hoda , Salarieh Hassan , Alasty Aria
Published: May 2009

The taping mode Atomic Force Microscopic (T-AFM) can be assumed as a cantilever beam which its base is excited by a sinusoidal force and nonlinear potential interaction with sample. Thus the cantilever may cause chaotic behavior which decreases the performance of the sample topography. In order to modeling, using the galerkin method, the PDE equation is reduced to a single ODE equation which properly describing the continuous beam. In this paper a nonlinear delayed feedback control is proposed to control chaos in T-AFM system. Assuming model parameters uncertainties, the first order Unstable Periodic Orbits (UPOs) of the system is stabilized using the sliding nonlinear delayed feedback control. The numerical results show the high quality and good performance of the proposed method.
Design and Analysis of Hydraulic Pumping Units
Authors: Li Guixi , Ma Rujian , Wang Jungang
Published: May 2009

The dynamic performance of hydraulic beam pumping units was analyzed in this paper by using the theory of mechanical vibrations. The house-head movement of the pumping unit is mainly uniform, except the alternation period of upper- and down-strokes. Under the action of the house-head movement, the vibration of the system, the sucker-rod and, furthermore, the dynamic stress will be induced. The results indicate that the movement of the downhole pump includes two parts. One is the movement following the horse-head. The other is the dynamic response excited by the support movement. When the parameters of the system are selected reasonably, over-stroke of the pump will appear. This is because the movement of the hydraulic piston obeys a particular law. The maximum displacement increases, and the maximum dynamic stress decreases with depth. The changing of maximum dynamic stress with depth obeys quadratic law.
Numerical Simulation of Air Entrainment Between Web and Spirally Grooved Roller Using Fluid-Structure Interaction Models
Authors: Si Bui Quang Tran , Byun Doyoung , Yoo Yong Hoon , Lee Jae Woo , Shin Ki Hyun , Byun Yong Hwan , Lee Chang Jin
Published: May 2009

This paper presents numerical quasi-static simulation results of air entrainment phenomenon between a web and a spirally grooved roller. The numerical result shows that during one circle rotation of spirally grooved roller, traction coefficient between the web and roller is changed according to time due to changing shape of groove in contact region and average traction coefficient of spirally grooved roller is higher than circumferential grooved roller. Using laser sensor, web deflection is measured and compared with the numerical results of web deflection at the entrance region. Furthermore, smoke wire experiment shows a clear view of air entrainment phenomenon at the entrance region between the web and roller.
Probabilistic Design of Networked Control Systems With Uncertain Time Delay
Authors: Lu Bei
Published: May 2009

Networked control systems (NCSs), where control loops are closed through a real-time network, have been adopted in many application areas. Examples include manufacturing plants, automobiles, aircraft, and spacecraft. However, the insertion of a real-time network introduces time delays due to time-sharing of the communication media. The network-induced delay can degrade the performance of an NCS, and can even destabilize the system. Due to its random nature, in this paper, we apply the promising probability robust control approach to handle the network-induced delay, which is modeled as an uncertainty governed by a probability distribution function. With considering both stability and performance of NCSs in the stage of control design, we propose the synthesis condition of ℋ∞ state-feedback control of NCSs. It is formulated as a set of linear matrix inequalities with uncertain parameter present in the the state-space data. The ellipsoid randomized algorithm is applied to solve the matrix variables and design a probabilistic robust controller. A numerical example is given to demonstrate the probabilistic design method for NCSs.
Compatibility Evaluation of BZ25-1 Crude Oils in Bohai Bay, China
Authors: Jing Jiaqiang , Niu Hongbin , Pan Lingbin , Xiong Xiaoqin , Tan Liwen
Published: May 2009

BZ25-1 oilfield is located in the southeast of Bohai bay which geographically lies between 119°00′ to 119°15′ east longitude and 38°10′ to 38°20′ north latitude. It has two oil blocks, including Shahejie (SHJ) waxy oil and Minghuazhen (MHZ) heavy oil, with six wellhead platforms WHPA∼WHPF and six submarine pipelines. Therein, the WHPC-WHPB and WHPB-SPM (Single Point Mooring) pipelines transport the mixture of the two produced crude oils. However, the mixing of the two oils will certainly bring out a change in their components and properties, which directly affects the safe operation of the submarine pipelines and offshore production facilities. Therefore, this paper compounds three kinds of MHZ/SHJ mixed oils with blending ratios of 1:1, 3:1 and 9:1, mainly studies how the components, rheological and thermophysical properties of the oil mixtures change with the blending ratio. The major objective of this study is to evaluate the compatibility of the two crude oils and provide a theoretical basis for the production optimization and risk elusion of the oilfield. The results of the study show that the components and properties of SHJ crude oil are quite different from those of MHZ oil, the flow behavior of SHJ oil is more sensitive to temperature. As MHZ oil in the compounds increases, the contents of asphaltene, resin, sulfur and carbon residue will increase except wax contents, their viscosities, densities and flash points will also increase, but their pour points, yield stresses, calorific values and other major thermophysical parameters will decrease. A blending ratio of 2∼7:1 for MHZ to SHJ crude oil can be concluded to make the properties of the compounds meet the safe and economic requirements of the subsea pipeline and offshore facility operations and ensure the compatibility of the mixed oils. In actuality, the field operations have confirmed that the recommended blending ratio is reasonable and practicable.
Simulation of a Methane-Air Jet Flame by LES and RANS Model
Authors: Wang F. , Zhou L. X. , Xu C. X. , Huang Y.
Published: May 2009

A piloted methane/air jet flame, measured in the Sandia National Laboratory, is simulated by both 3-D large eddy simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) modeling. In LES, an algebra second order moment sub-grid scale (ASOM-SGS) combustion model is applied, while the second order moment (SOM) transport equation combustion model is employed in RANS method. The LES predicted time-averaged and root mean square (RMS) fluctuation temperature and methane concentration are in good agreement with the experimental data, showing the feasibility of the ASOM-SGS combustion model. For time-averaged temperature and species concentration, the performance of the RANS SOM model is rather good. Considering the difference of nearly two orders of magnitude in the computation time between LES and RANS modeling, the latter is considered to be more appropriate for engineering application. The LES instantaneous results show the coherent structures in the flame. It is found that reaction enhances the coherent structures, and conversely the coherent structures intensify combustion, forming a wrinkled-flame surface.
Study of Time and Temperature Dependency of Bulk Modulus for Molding Compound by Transient Bulk Creep Experiments
Authors: Patel M. D. , Jansen K. M. B. , Ernst L. J. , Zhou J. , Bohm C.
Published: May 2009

Transient bulk creep experiments were performed to investigate the time and temperature dependency of the bulk modulus for epoxy molding compound. These, so called pressure jump volume relaxation experiments were done by applying positive and negative pressure jumps followed by a holding period at those pressure levels and the whole set of experiment was repeated at different temperatures. The observations are in the pressure range of 10 to 50 MPa and temperature range of 50 to 150° C. For negative pressure jumps (or expansion experiments) the bulk modulus was found to be almost independent of time. For positive pressure jumps (or compression experiments) time dependent volume decreases very slow. Compared to time and pressure, temperature dependency was of highest influence. A mathematical model has been proposed for the observed temperature and pressure dependency of the bulk modulus.
Vibration Analysis of a Composite Timoshenko Beam With Actuating Layers Under Motion of a Uniformly Traveling Partially Distributed Mass
Authors: Ahmadian M. T. , Paak M. , Pirbodaghi T. , Hassanpour S.
Published: May 2009

In this paper, a thorough investigation of response of a composite Timoshenko simply-supported beam with actuating layers, under the motion of a partially distributed mass is studied and a control system based on the feedback of beam’s deflection velocity is applied to alleviate and suppress the vibration of the beam in either case when the mass is still traveling on the beam or departed the beam. The actuating layers are made up of Terfenol-D smart material which are sensitive to magnetic field (magnetostrictive materials) and this trait makes them very suitable to be used for vibration control. They introduce damping to the system through which the energy of system dissipates. The response of the beam is analyzed in terms of lamination scheme, material properties, damping coefficient (i.e. gain of controller), velocity of motion and geometrical features of the moving mass (e.g. moving mass length and height). The governing equations of system are obtained using Hamilton’s principle and a solution is sought using Galerkin’s method, the resulting coupled system of ODEs are solved numerically by virtue of the Newmark method. The results are compared with those available in literatures along with discussion on agreements and disagreements.
Novel Processing of Structural Epoxy for Shielding and Structural Applications
Authors: Al-Haik M. S. , Trinkle S. , Momotyuk O. , Roeder B. T. , Kemper K. , Hussaini M. Y.
Published: May 2009

In this study we investigate the shielding effectiveness of a structural epoxy against high energy protons. To study the influence of material texture on its radiation shielding effectiveness we induced orientations in the epoxy using a high magnetic field of 15 T, and exposed it to proton beams of energy 6 MeV-15 MeV. The micro structures of the samples were characterized using ESEM microscopy. The effect of the radiation on the mechanical properties of the samples was measured using nanoindentation tests. The findings of this study can lead to an optimal processing path for multifunctional epoxy that can be utilized as structural and shielding component in future space missions.
Application of an Artificial Neural Network in Gas-Solid (Air-Solid) Fluidized Bed: Heat Transfer Predictions
Authors: Ravindranath G. , Prabhukumar G. P. , Channamalla Devaru B.
Published: May 2009

This paper presents heat transfer analysis of in-line arrangement of bare tube bundles in gas-solid (air-solid) fluidized bed and predictions are done by using Artificial Neural Network (ANN) based on the experimental data. Measurement of average heat transfer coefficient was made by local thermal simulation technique in a cold square bubbling air-fluidized bed of size 0.305m × 0.305m. Studies were conducted for bare tube bundles of in -line arrangement using beds of small (average particle diameter less than 1mm) silica sand particles and of large (average particle diameter greater than 1mm) particle (raagi and mustard). Within the range of experimental conditions influence of bed particle diameter (Dp), fluidizing velocity (U) were studied, which are significant parameters affecting heat transfer. Artificial neural networks (ANNs) have been receiving an increasing attention for simulating engineering systems due to some interesting characteristics such as learning capability, fault tolerance, and non-linearity. Here, feed-forward architecture and trained by back-propagation technique is adopted to predict heat transfer analysis found from experimental results. The ANN is designed to suit the present system which has 3 inputs and 2 outputs. The network predictions are found to be in very good agreement with the experimental observed values of bare tube heat transfer coefficient (hb) and Nusselt number of bare tube (Nub).
Novel Approach for Physical Modeling of Microfluidic Systems
Authors: Patrascu Mihai , Crego-Calama Mercedes , Brongersma Sywert H. , de Boeck Jo
Published: May 2009

The study of fluid flow in micro systems is still an open issue. Finite element models are generally used during prototyping. Such models are useful when the geometry has a large impact on device performance. Unfortunately, the nature of such methods and especially the mesh complexity limits simulation studies to non-transient or limited transient behavior. We present a different approach of microfluidic modeling, which is based on bond graph theory. Lumped component physics and power relations between the elements determine the dynamic behavior. In this way, dynamic simulations are ubiquitous and pave a way for control design. After introducing a number of basic microfluidic components, we concentrate on a case consisting of a three-valve micropump actuated peristaltically and connected to a thin, long tube. Input signals, device dimensions, electrical and mechanical material properties and fluid viscosity are explicitly present in the model and can be fitted for increased performance. Amongst others, simulations reveal the volume flow, pressure generation, and average fluid velocity throughout the model.
Recent Advances in Thermal Modeling of Micro-Evaporators for Cooling of Microprocessors
Authors: Thome John R. , Revellin Re´mi , Agostini Bruno , Park Jung Eung
Published: May 2009

Cooling of microprocessors using flow boiling of low pressure refrigerants in multi-microchannel evaporator cooling elements is a promising technique for dissipation of footprint heat fluxes of over 300 W/cm2 while maintaining the chip safely below its maximum working temperature, providing a nearly uniform chip base temperature and minimizing energy consumption. The present invited lecture focuses on our recent experimental work and modeling of two-phase flow and boiling in single and multi-microchannels, covering: bubble dynamics, bubble coalescence, flow pattern recognition, diabatic flow pattern map, critical heat flux, hot spots, flow boiling heat transfer and two-phase pressure drops.
Effect of Thermal and Stress Fields on the Microstructure of a Thin Wall Built Using Laser Solid Freeform Fabrication Process
Authors: Alimardani Masoud , Paul Christ P. , Toyserkani Ehsan
Published: May 2009

Temperature distribution and consequent rapid cooling determine the microstructure and final physical properties of a part fabricated using laser solid freeform fabrication (LSFF). As well, in this technique, thermal stresses are the main cause of any possible delamination and crack formation across deposited layers. In this paper, the temperature distribution and the stress field induced during the LSFF process are studied throughout the fabrication of a thin wall up to four layers. The thin wall is fabricated of stainless steel AISI 304L using a 1 kW Nd:YAG pulsed laser. Variations of the microstructure and geometry of the wall are studied. A 3D dynamic numerical model of the multilayer LSFF process is used to interpret the experimental results in terms of the temperature distribution, stress field and microstructure. The experimental results show that the stress concentrations at the end points of the wall, which are due to the higher temperature gradient at these regions, are the locations for possible delaminations and crack formations. Different types of microstructures are observed at the various locations within the same layer due to the different cooling rate. While numerical results confirm the experimental findings, they also show that it is possible to reduce the maximum stress by preheating the substrate.