bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Thermoplastics in a Short Pulsed Laser Welding Process
Authors: Whalen Richard A. , Kowalski Gregory J.
Published: April 2008

A numerical simulation code is developed and used to investigate the differences in thermal behavior and the size of the heat affected zone (HAZ) in a short pulsed transmission laser welding process (>0.5 ps (1/e2)). The numerical model uses both a Fourier and Hyperbolic thermal model. The welding process involves the lap welding of two thin layers of thermoplastic films. The investigated welding conditions are transparent material over a semi-transparent or opaque material. The results provide temperature profiles that illustrate the differences between the predicted temperatures of the two thermal models as well as the effects of laser intensity and material thermo-physical properties.
Distributed Component Development Risk Analysis
Authors: Leung Peter , Ishii Kosuke , Benson Jan , Abell Jeffrey
Published: April 2008

This paper describes a method to identify and to evaluate the risks associated with task transfer in a globally distributed engineering environment. Enterprises realize the importance of global worksharing to include diverse customer values into product, but this paradigm also introduces challenges in product development. Industry-wide interviews reveal workshare risks are at two levels: system and component. This paper presents a three-step risk analysis to 1.) characterize product development work tasks, 2.) define Distributed Component Development Risk based on historical rework data, and 3.) evaluate workshare scenarios for the task transfer plan. Three interior vehicle components illustrate the steps of the risk analysis, and the findings indicate most rework happens at the system-level design stage while the discovery of these errors occurs during validation and manufacturing. As a result, the transfer of these tasks leads to high likelihood of rework. Currently, this method is applying in actual global automotive programs for validations.
Characterization of a Tunable MEMS RF Filter
Authors: Hammad Bashar K. , Abdel-Rahman Elihab M. , Nayfeh Ali H.
Published: April 2008

We present a reduced-order analytical model to describe the response of a tunable MEMS RF filter to an input signal whose frequency is in the neighborhood of the passband. It extends our earlier model by allowing for the application of independent DC voltages in addition to an AC input signal. The model is obtained by discretizing the distributed-parameter system using a Galerkin procedure. It consists of two second-order nonlinearly coupled ordinary-differential equations. Using the method of multiple scales, we determine four first-order nonlinear ordinary-differential equations describing the amplitudes and phases of the modes. We found that mismatch between the natural frequencies of the resonators modifies the global modes significantly, leading to localization of the response in either the input or the output beam. We found that the filter can be tuned to operate linearly for a wide range of VAC by choosing a DC voltage that makes the effective nonlinearities vanish. Amplifying the input signal VAC to improve the filter performance creates multi-valued responses beyond a threshold in the case of non-zero effective nonlinearities.
Precise Measurement and Analysis of Heat Transfer to the Inlet Air Using Intake Port Model
Authors: Uchida Keisuke , Suzuki Takashi , Oguri Yasufumi , Yoshida Masatake
Published: April 2008

Temperature measurement experiments with an intake port model and analysis of heat transfer phenomena were carried out to obtain the fundamental information on constructing physical model that expressed heat transfer phenomena in an engine intake system. Temperature measurement experiments on steady air flow were done, and shape inside the intake port model, heating temperature of the intake port model, mass flow rate of air, and the development conditions of the velocity boundary layer and the thermal boundary layer were changed as experiment parameters. As the results, it was clear that the change of inside shape and heating temperature had little influence to the change of Nusselt number but the development condition of the velocity and thermal boundary layer had great influence. And the equations that expressed the Nusselt number with Reynolds number and Graetz number in each case that the velocity and thermal boundary layer were developed simultaneously and individually were obtained.
Programmable Separation for Biologically Active Molecules
Authors: Gutierrez Mauricio R. , Youcef-Toumi Kamal
Published: April 2008

Separation of biologically active molecules (BAMs) is a problem for the pharmaceutical and biotechnology industries. Current technologies addressing this problem require too many techniques, toxic additives, and time to filter the desired materials. As a result, a new technology is needed. The objective of this work is to contribute to the development of a device that can separate 0.5 nm to 500 nm sized BAMs. A diaphragm valve is proposed that can control a gap created by two parallel flat surfaces. Position control is achieved by means of a piezoelectric actuator and a capacitive sensor. Modularity was also part of design considerations to address issues of eventual biocompatibility breakdown. Preliminary experiments indicate that gap separation can be controlled to increments of 0.2 nm.
Laboratory Investigation of Seat Suspension Performance During Vibration Testing
Authors: Mayton Alan G. , DuCarme Joseph P. , Jobes Christopher C. , Matty Timothy J.
Published: April 2008

Mining injury statistics show that a significant number of back, neck, and head injuries are linked to exposure from vehicle vibration. Use of a suspension seat is a common way to isolate the vehicle operator from the adverse effects of vibration exposure. Thus, researchers at the National Institute for Occupational Safety and Health1 - Pittsburgh Research Laboratory (NIOSH - PRL) performed laboratory studies on four passive and two semi-active seat suspension designs. These are typical of seat suspensions commonly found on large off-road heavy surface mining, construction and agricultural vehicles as either replacement or original equipment manufacturer (OEM) systems. One included a pneumatic (air bladder) spring mechanism. The fifth and sixth suspensions were a NIOSH magnetorheological (MR) semi-active damper design based on the pneumatic (air bladder) and one of the coil spring suspensions above. These suspensions were modified with a commercially available MR damper substituted for the OEM damper. These six seat suspension systems were tested and analyzed, for vertical vibration only, using the ISO 5007 Standard [1]. This paper describes the laboratory vibration tests using a MTS® shaker table and discusses the results obtained for the different suspension designs and highlights the rheonetic technology studied. Implications of the seat suspension designs relative to their capabilities for isolating vehicle operators from vibration exposure are discussed. Results for suspensions 1 through 3 showed frequencies of isolation from 2.1 to 3.0 Hz using the 40-kg (88-lb) mass and from 1.65 Hz to 1.8 Hz using the 80-kg (176-lb) mass. Suspension #4, in tests with only the 80-kg (176-lb) mass, showed an isolation frequency of 3.7 Hz. With the MR damper added to seat suspension #4, the peak transmissibility was lowered from 1.3 to 0.95 and showed a corresponding downward shift in frequency from 2.25 Hz to 1.4 Hz. In fact, the results for suspension #5 (the MR damper added to seat suspension #4), using test #3 conditions of the programmed control algorithm, showed isolation (attenuation of transmitted vibration) throughout the test frequency range from 1.0 to 6.0 Hz.
On the Integration of Remote and Virtual Experiments Into a Comprehensive Student Laboratory Experience
Authors: Aziz El-Sayed S. , Chassapis Constantin , Esche Sven K.
Published: April 2008

Student laboratories have always played a key role in the engineering education at Stevens Institute of Technology (SIT). Recently, SIT has designed and implemented several innovative Web-based tools for engineering laboratory education and evaluated their learning effectiveness in pilot deployments in various engineering courses. These Web-based tools include both remotely operated experiments based on actual experimental devices as well as virtual experiments representing software simulations. These tools facilitate the development of learning environments, which - possibly in conjunction with traditional hands-on experiments - allow the expansion of the scope of the students' laboratory experience well beyond the confines of what would be feasible in the context of traditional laboratories. This becomes possible because of the scalability of resources that are shared through the Web and the flexibility of software simulations in varying the characteristic parameters of the experimental system under investigation. Further educational benefits of the proposed laboratory approach are that asynchronous learning modes are supported and discovery-based self-learning, of the students is promoted. This paper will present the details of the approach taken at SIT in integrating these Web-based tools into a comprehensive student laboratory experience. As an example for the implementation of such Web-based experiments, an Industrial-Emulator/Servo-Trainer System will be described, which is used at SIT in a junior-level course on mechanisms and machine dynamics.
Strategy for Integrated Use of the Industrial Waste Heat
Authors: Skop Helen , Chudnovsky Yaroslav
Published: April 2008

The domestic industrial sector uses over 32 quads of energy that represents one-third of the total energy consumed annually in United States of America. Energy consumption details can be found at www.eia.doe.gov/aer/. Obviously, that the efficient use of available energy has a substantial impact on the competitiveness of domestic manufacturers as well as on the environment. Efficient conversion of raw materials into usable products and usable work/energy strictly depends on the commercially available technologies and equipment. Energy efficiency significantly varies across multiple industries and different applications but one of the major energy losses is thermal energy loss, so-called waste heat. Sources of the waste heat comprise of variety of gaseous exhausts, waste process liquids, cooling media, chemical waste and environmental losses. Over 30 years the engineering community has been trying to develop cost-effective approaches for waste heat recovery and utilization. However, so far there is no universal and cost-effective solution or approach for the industrial waste heat recovery and utilization. In this paper authors discuss an integrated strategy of the industrial waste heat use through the consideration of the closest surrounding of the waste heat source and other types of waste (chemical, mechanical, acoustical, etc.) along with most promising heat exchanger design concepts to be appropriate for integrated waste heat recovery and utilization.
Optimization of Parison Thickness in Extrusion Blow Molding Using Fuzzy Iterative Learning Control Algorithm
Authors: Huang Geng-Qun , Huang Han-Xiong
Published: April 2008

Blow molded parts require a strict control of the part thickness distributions so as to achieve the required mechanical performance and to minimize the usage of material. In this paper, an optimization algorithm combining iterative learning control (ILC) with fuzzy logic was used to get the optimal parison thickness distributions for a part with uniform wall thickness distribution. Instead of using the pure numerical method, engineer knowledge and experience were combined in the optimization algorithm using fuzzy rules. It was shown that the fuzzy ILC algorithm is effective to obtain the optimal parison thickness distributions.
Modeling and Control of the pH Neutralization Process for a Recirculating Hydroponic Growth Chamber
Authors: Mukhtar Moeed , Chiu George T.-C. , Massa Gioia , Mitchell Cary A.
Published: April 2008

In this paper, a pH control system for an experimental recirculating hydroponic growth chamber for the NASA Mars exploration program has been modeled and implemented. The resulting model has a bilinear Weiner type structure. A novel approximation approach is presented to obtain a simplified plant model controller design. Perturbation analysis validates the applicability of the approximation for the specific pH control of a closed-loop hydroponic growth chamber. A modified PI controller that takes into account on-off nature of the solenoid valve actuator was designed to control the pH level. The closed-loop system is shown to be BIBO stable with respect to the original bilinear plant model. Experimental results for reference tracking and disturbance rejection in an operational hydroponic chamber with growing plants have demonstrated the effectiveness of the proposed approach.
Application of Improved Genetic Algorithms for Sensor and Actuator Placement of Active Flexible Structures
Authors: Zhang Jingjun , Zheng Ji , Gao Ruizhen
Published: April 2008

In order to reduce the vibration of flexible structures, this paper developed an effective procedure to determine the location of multi-piezoelectric elements in active flexible structures. The D-optimal design principle is an optimization method which chosen by the maximum determinant of Fisher Information Matrix Criteria. Study on the mode shapes and dynamic characteristics of structure, and the mode shapes of selected structural are converted into unitary mode. In order to approach higher level of vibration control, piezoelectric patches are placed on the maximum mode strain locations of the structure. The mode shapes of flexible structure are extracted and analysed using the Ansys software, and an interface is completed between the GAs and Ansys software.
Characterization of Mechanical Properties of Carbon Nanotubes in Copper-Matrix Nanocomposites
Authors: Baik Seunghyun , Lim Byeongsoo , Kim Bumjoon , Sim Untae , Oh Seyoung , Sung Byung-Ho , Choi Jee-Hoon , Kim Chul-Ju
Published: April 2008

Carbon nanotubes have received considerable attention because of their excellent mechanical properties. In this study, carbon nanotube - copper composites have been sintered by a mechanical mixing process. The interfacial bonding between nanotubes and the copper matrix was improved by coating nanotubes with nickel. Sintered pure copper samples were used as control materials. The displacement rate of nanotube-copper composites was found to increase at 200°C whereas that of nickel-coated nanotue-copper composites significantly decreased. The incorporation of carbon nanotubes and nickel-coated carbon nanotubes in the copper matrix decreased friction coefficients and increased the time up to the onset of scuffing compared with those of pure copper specimens.
Dynamic Analysis of an O2 Separating Membrane Reactor for CO2-Emission Free Power Processes
Authors: Selimovic Faruk , Eborn Jonas , Sunde´n Bengt , Tummescheit Hubertus
Published: April 2008

The need to reduce CO2 emissions from fossil-fuel based power production creates the need for new power plant solutions where the CO2 is captured and stored or reused. Oxygen Transfer Membrane (OTM) is the key component of oxy-fuel combustion processes as pure oxygen is usually required to process reactions (e.g. Natural Gas Combined cycle NGCC, Pulverised Coal-fired power plants PC-plants, Integrated Gasification Combined Cycle IGCC). The transfer of oxygen across such OTM is limited by a number of processes, such as surface exchange and ambipolar diffusion through mixed-conducting gas separation layer. This paper shows a mathematical model of an oxygen transfer membrane incorporated into OTM reactor (OTM reactor consists of High Temperature Heat Exchanger and OTM), where transient behavior takes place. The modeling of the OTM reactor has been carried out to show the importance of optimizing OTM parameters (temperatures, oxygen partial pressures, oxygen flux) and reactor design that enables a high oxygen transfer for optimum performance of future power cycles with CO2 capture. All modeling work was carried out in the modeling language Modelica, which is an open standard for equation-based, object-oriented modeling of physical systems. The OTM reactor model has been built using the CombiPlant Library, a modeling library for combined cycle power plants which is under development.
Streamwise and Spanwise Flow Structures Over Backward Facing Step in Low Reynolds Number
Authors: Yamada Shunsuke , Matsumoto Tatsuya , Nagumo Takashi , Honami Shinji
Published: April 2008

A study on the low Reynolds number flow such as the flow in or around the micro device is strongly required along with the development of the micro manufacturing technology. The low Reynolds number flow over a backward facing step is selected as one of the representative examples of the vortex dominant flows in the present study, because the mixing promotion is expected by an oscillatory motion of the vortex in the separating and reattaching shear layer over the step. It is important to clarify the flow fields in small channel or around the small device by flow visualization, since minimum disturbance in the measurement is achieved due to non-intrusive method. The objective of the present study is to clarify the flow behavior in the cross section in the spanwise, transverse and streamwise direction by the flow visualization using a high speed video camera. The Reynolds number based on the step height and the bulk velocity is set at 380 to 960. The visualization results in the cross section in the spanwise direction show that the separating shear layer from the step edge introduces a series of the primary vortices which have a rotation axis around the spanwise direction, and the main stream has a regularly whipping, wavy motion caused by the vortices moving toward the downstream direction along the upper and lower walls. The observation in the cross section in the transverse direction indicates that a scale of the vortex length in the streamwise direction is almost constant, but the primary vortex shows a periodic change in the spanwise direction, as the Reynolds number increases.
Realization of the Rapid Movements for the Entertainment Robots by Using Two New Actuators “Inertia Actuatror” and “CAM Charger”
Authors: Nassiraei Amir A. F. , Murata Masayuki , Ichikawa Koudai , Ishii Kazuo
Published: April 2008

In this paper, we describe the realization of rapid movements for the entertainment robots by using two new actuators "Inertia Actuator" and "Cam Charger". Inertia Actuator, as an internal torque generator, is a kind of potential actuator that can generate a small internal torque by changing the speed of the rotor and a big internal torque in short time by using a brake to stop the rotor at high speed. In order to realize the jumping capability, Cam Charger mechanism is introduced to fit to the foot shape. The key idea is to charge a series strong torsion spring by using a special design of a cam in shape. First, we describe the principle of Cam Charger and Inertia Actuator. Second, in a physical simulation, we investigate the feasibility of the approach. Next, we show experimentally that a prototype of our artistic robot "Jumping Joe" includes of these two new actuators can demonstrate several rapid movements such as fast wake up, jumping and somersault.
Evaluation for Static and Dynamic Characteristics of a Miniaturized Machine Tool According to Its Configuration
Authors: Lee J. H. , Yang S. H. , Kim Y. S.
Published: April 2008

Miniaturization for manufacturing system has been studied widely since the development of the smallest lathe in the world. Several prototypes are implemented, which are used to produce small parts with high precision. Accuracy and stiffness are the most important factors for design in the development of miniaturized systems. This study presents a method to evaluate static and dynamic characteristics of a miniaturized machine tool (mMT) according to its configuration before building the actual system. The proposed error estimation technique shows that volumetric error can be estimated indirectly at the design stage using error components of one axis and HTM (Homogeneous Transform Matrix), unlike the error modeling technique through direct measurement. Thus, accuracy of the system based on its configuration is analyzed at the design stage itself. The proposed analysis procedure is shown for the case of a 3 axis machine tool. In addition, dynamic characteristics of spindle unit affecting the spindle error are studied.
nSIR: A Novel Passive-Active Intelligent Moving Mechanism for Sewer Inspection Robots
Authors: Nassiraei Amir A. F. Forough , Mikuriya Yoshikazu , Ishii Kazuo
Published: April 2008

In the current sewer pipe inspection technology, all commercial sewer inspection robots have a poor mobility function to pass any kind of pipe-bends such as curves and junctions so that those robots are only capable to move into the straight pipes. In this paper, we describe the design, modeling, simulation and implementation of a compact and novel moving mechanism, called "nSIR mechanism", with capability of moving into the straight pipe and passing different kinds of pipe bends without need to any intelligence of the controller or sensor reading. The design is based on the concept of passive adaptation of robot wheels to the bends in the pipe. This is accomplished by proper wheels orientation and passive damping of springs. In addition, this moving mechanism has capability to pass the different size of pipes in diameter even from a bigger diameter pipe to smaller diameter and also can pass obstacle and go down step. After describing the principle of nSIR mechanism, this paper gives experimentally that a prototype of our robot "KANTARO" includes of this mechanism can realize all the above movement functions.
Prediction of Hydraulic Inertance Using Acoustic Measurements and CFD Modeling
Authors: Boyd Lewis J. , Roberts Andrew P. , Collett Andrew P. S. , Johnston D. Nigel , Tilley Derek G. , Edge Kevin A.
Published: April 2008

Fluid inertia within passageways of hydraulic components is known to have a significant impact on their dynamic response and fluid-borne noise characteristics. This inertance is often hard to quantify either theoretically or experimentally due to the complex nature of component geometries, and because it is related to dynamic, not steady-state behaviour. Previous studies have used the secondary source method to determine the impedance, of which the inertance is an important parameter, of components such as positive displacement pumps and valves. A simple acoustic test for predicting the inertance of a component is proposed. The component must have a direct connection between inlet and outlet, and as such is directly applicable to valves and accumulators. Results were compared to theory for known components, including uniform pipes, and with predictions made using the commercial computational fluid dynamics (CFD) package ANSYS CFX, using the analogy of steady state flow through a porous passageway of identical geometry. In general, good agreement between acoustic measurements and CFD predictions was obtained for a number of ball valves, gate valves and an accumulator poppet valve.
Application of Differential Evolution in System Identification of Servo-Hydraulic System With a Flexible Load
Authors: Yousefi H. , Handroos H.
Published: April 2008

Electro Hydraulic Servo Systems (EHSS) with an asymmetrical cylinder are commonly used in industry. These kinds of systems are nonlinear in nature and their dynamic equations have several unknown parameters. System identification is a prerequisite to analysis of a dynamic system and design of an appropriate controller for improving its performance. In conventional identification methods, a model structure is selected and the parameters of that model are calculated by optimizing an objective function. This process usually requires a large set of input/output data from the system. In addition, the obtained parameters may be only locally optimal. One of the most promising novel evolutionary algorithms is the Differential Evolution (DE) algorithm for solving global optimization problems with continuous parameters. In this article, the DE algorithm is proposed for handling nonlinear constraint functions with boundary limits of variables to find the best parameters of a nonlinear servo-hydraulic system with flexible load. The DE guarantees Fast speed convergence and accurate solutions regardless the initial conditions of parameters. The results suggest that, DE is useful, reliable and easy to use tools in many aspects of control engineering and especially in system identification.
PDMS Membrane Microactuator for Focal Tunable Microlens
Authors: Lee Seok Woo , Lee Seung S.
Published: April 2008

In this paper, PDMS membrane for a large displacement is fabricated by new fabrication process which can be integrated with electrical components on substrates fabricated by conventional microfabrication processes and the performance of the membrane using electromagnetism was evaluated. Rectangular PDMS membranes are designed as 2mm and 3mm in width, respectively and are actuated by Lorentz force induced by current paths spread on the membrane. The PDMS membrane is fabricated by reducing a viscosity of uncured PDMS with dilution and spin coating on the substrate on which electric components generating Lorentz force. Finally, PDMS membrane including electric components is opened by a bulk micromachining. The device is tested in magnetic field induced by Nd-Fe-B magnet whose magnetic flux density is 90G. When applied currents are 20, 25, and 30mA, the maximum deflections of membranes are 1.21, 3.07, and 20.2μm for 1.5mm width membrane and 3.34, 31.0, and 50.9μm for width 3mm membrane, respectively. The large displacement PDMS membrane actuator has potentially various applications such as fluidics, optics, acoustics, and electronics. Currently, we are planning to measure the optical performance of the actuator as a focal tunable liquid lens.
An Experimental Investigation of Flow Fields Within Miniature Scale Centrifugal Pumps
Authors: Kearney D. , Punch J. , Grimes R.
Published: April 2008

Thermal management has become a key point in the development of contemporary electronics systems. It is evident that heat fluxes are currently approaching the limits of conventional forced air cooling, and that liquid technologies are now under consideration. The objective of this paper is to investigate the flow fields within a miniature scale centrifugal pump in order to determine velocity profiles describing the flow. The experimental setup consisted of a hydrodynamic test bed constructed to measure the pressure-flow characteristic of a centrifugal pump with a rated volumetric flow of 9 l/min. The impeller diameter of the pump under consideration was 34.3mm, and the characterisation experiments were carried out at a constant impeller speed. Particle-Image Velocimetry (PIV) was used to measure velocity profiles within the volute section of the pump. Synchronised velocity profiles are illustrated for three operating points on the pump characteristic curve. A hydrodynamic analysis of the velocity vectors at the impeller tip is also included, and pump model verification is then discussed based on the comparison between the theoretical predictions and the PIV data.
Visualization of Motion Envelope of Parts and Assemblies Based on Simulation or Measurement Data
Authors: Lo¨o¨f Johan , Lindkvist Lars , So¨derberg Rikard
Published: April 2008

As the demand on productivity in the manufacturing industry increases, it's important with tools that shorten the time from concept to production. Visualization has become a popular tool for fast and easy verification regarding many aspects of products in the design phase. In this paper an algorithm is developed to calculate and visualize the total volume in space a part or assembly creates when it is affected by displacement or motion. The algorithm is general and works on all kinds of problem where there is variation or motion involved. The data used to create the total volume is either collected from simulation data or from real measurement data. This paper includes an introduction and background to the problem and a deep explanation of the suggested algorithm. Finally the algorithm is used to visualize the motion envelope of a car engine based on real measurement data. The data and engine is collected from a well known car manufacturer. The result shows that the suggested method for visualization is useful in early phases for design, packaging and tolerance analysis.
An Artificial Neural Network Model to Predict Material Characteristics From the Results of Miniature Circular Disk Bending Tests
Authors: Ghosh A. K. , Behera G. , Verma V.
Published: April 2008

Miniature disk bending test was developed to evaluate the mechanical behavior of irradiated materials - mainly to identify the ductility loss in steels. The analytical solution for large amplitude, elasto-plastic deformation with contact and friction becomes rather unwieldy. It is difficult to distinguish between the regimes of elastic and plastic deformation since local plastic deformation occurs for very small values of load when the magnitude of spatial average stress is well below the yield stress. Thus the inverse problem of evaluating properties from the experimentally observed values of the deflection of the specimen is rather difficult to solve analytically. The paper discusses some of the published work in this area and the difficulties associated with them. The approach in this work is to first generate a large database - by a finite element (FE) solution - of load-displacement (P-w) records for varying material properties viz. elastic modulus (E), yield stress (σy) and the constants (A0, m) appearing in the plastic stress-strain relation. An artificial neural network (ANN) is trained with the specified material properties and the corresponding load-displacement records. In the second phase, this network is tested with known data and then used with the experimentally observed (P-w) records to predict the abovementioned material properties. The paper presents the details of modeling (FE and ANN), a summary of the results obtained by the FE analysis (database) and the results obtained by the ANNs in the training and the testing phases. The errors in the various values of the parameters during testing were found to be within 5%.
Power Converters for Piezoelectric Energy Extraction
Authors: Ngo Khai D. T. , Phipps Alex , Nishida Toshikazu , Lin Jenshan , Xu Shengwen
Published: April 2008

Passive circuits and active circuits (i.e., switched-mode power converters) for vibration-energy harvesting are reviewed, focusing on power-extraction efficiency (PEE). Optimal battery voltage and resistance are given for maximal power extraction by passive circuits. Switched-mode converters are reviewed as means to match the actual battery voltage or load resistance to the optimal ones. To emulate the optimal battery voltage or load resistor, these converters could be controlled by pulse-width modulation (PWM) or by resonance, could operate in continuous or discontinuous conduction modes (CCM or DCM), and could leverage the piezoelectric (PZT) impedances in the energy extraction process. The large filter capacitor usually found after the bridge rectifier actually degrades the PEE. Resonance between the output capacitor of the PZT and the converter inductor improves the PEE at the expense of higher voltage and current stresses.
Senior Year Thermal Design Course: Elective or Mandatory Restricted Elective
Authors: Tari Ilker , Tari Sibel
Published: April 2008

According to the educational objectives of METU Mechanical Engineering Department, there should be two senior year design courses: a mechanical design course and a thermal or fluids design course. The department had a successful long running mandatory mechanical design course. Instead of preparing and offering a mandatory thermal or fluid design course, it is decided to change the status of three senior year elective courses in thermal or fluids field that were involving design elements. Among these, ME421 Heat Exchanger and Steam Generator design course is offered as restricted elective. The course had been offered as an elective course for a long time for a smaller group of interested students. In new restricted elective status, the number of students is increased but their overall interest level is dropped. The format changes made in the course to accommodate the change in status are presented. Some quantitative and qualitative examples are given to compare the previous and the current status in terms of student learning outcomes. Statistical significance of the observations is discussed along with the results of Bartlett's test.
Dynamic Modeling and Prototyping for Low-Frequency Piezoelectric MEMS Vibration Energy Scavenging: VibES
Authors: Mukherjee Rajib , O'Neal Chad B.
Published: April 2008

The advancement in the field of wireless electronics for use in embedded systems and control system technologies is limited by the availability of efficient and portable power generation system. Harvesting ambient energy provides an excellent option to energize these low power wireless electronic applications. Low frequency vibrational energy scavenging of microelectromechanical system (MEMS) utilizing piezoelectric power generation can effectively serve this purpose. Initial fabrication has been carried out in terms of PZT film characterization, initial testing to verify the piezoelectric nature of the as coated PZT film, optimization of 125 μm thick nickel electroplating, and innovative cantilever release process based on inductively coupled plasma etching (Bosch Process) to increase the yield of working cantilever arrays on a die. An optimized process flow for the prototype fabrication was proposed and lead zirconium titanate (PZT) thin film deposition by sol-gel was characterized on three different bottom electrodes. The net effective yield in terms of working cantilevers on a die was increased to about 80% of over 500 cantilevers on a die. X-ray diffraction results revealed the perovskite phase formation of the as-coated PZT film with a [111] predominant crystal orientation. The as-coated PZT film was poled and the initial testing confirmed the piezoelectric nature of the film. The desired cantilever configuration was modeled such that its natural frequency lies approximately in the 200 Hz range while ensuring that the maximum stress generated in the structure does not exceed the yield strength of the material both in the static stage and in the dynamic stage. It was observed that positioning of the mass was a significant factor influencing the natural frequency of the structure. The analysis was performed for cantilever configurations made of silica, PZT, and nickel in which the effect of the thinner layers (electrodes) has been ignored. It was found that this configuration yields a natural frequency of 255 Hz which lies in the desired range of frequency (100-500 Hz).
The Response of a Miniature Scale Cantilever Beam to High-G Impact Stimuli
Authors: Sheehy Michael , Punch Jeff , Rodgers Bryan , Goyal Suresh
Published: April 2008

Many contemporary innovations in MEMS devices result from the miniaturization of existing macro-scale systems, exploiting changes in physical phenomena with scale. In terms of a system subject to mechanical stimuli, the response of the system changes significantly as scale decreases: in particular, natural frequencies increase and the system can sustain higher acceleration levels without damage. The objective of this paper is to investigate the response of a miniature scale cantilever beam to high-G impact stimuli in order to gain an understanding of its response. The test model is a machined aluminium cantilever-beam simply supported at one end. The beam cross section is 400 × 200 microns and has lengths of 4mm, 10mm and 20mm. The test bed is an Instron Dynatup 9250HV drop table. The beam response under impact is monitored using an IDT X-Stream XS-4 high-speed camera fitted with a telecentric 10x lenses. Theoretical and computer simulated models using ANSYS and LS-DYNA software are developed and compared with experimentally measured data to verify the accuracy of the techniques used to analyse the structural behaviour of the cantilever beams. The use of high-speed imaging when testing devices for short duration events proves to be beneficial for obtaining several data sets not achievable by post processing techniques.
The Dynamics of a Small-Scale Portable Electronics Device Under Impact Stimuli
Authors: Kelly Gerard A. , Punch Jeff M. , Goyal Suresh
Published: April 2008

The reliability of portable electronic devices is of critical importance due to the consumer boom in mobile telephony in recent years. Impact is a key driver of failure in portable electronics and, in current design practice, extensive testing is used in conjunction with finite element simulations to ensure product reliability under impact stimuli. Testing is time-consuming and expensive – both free-drop and constrained drop tests are usually applied – and simulation techniques are very computationally intensive. The response of portable electronic devices to impact is currently not well understood, and there is clear need for investigation into the range of acceleration levels experienced by a representative model of a portable electronic device on impact. In this paper, free-drop testing was carried out on test vehicles representative of a typical mobile phone in order to acquire acceleration data from impact events. Drop test vehicles from Nylon and aluminium were used to provide a means of comparison for diverse material properties. The primary conclusion was that the dynamics of each drop event were highly sensitive to the initial conditions of the drop test, which was evident from wide variances in the acceleration data.
Squeeze Film Damping Models Compared With Tests on Microsystems
Authors: Sumali Hartono (Anton) , Epp David S.
Published: April 2008

This paper compares three models for computing forces caused by gas film squeezed between parallel plates. The models are used to calculate damping forces on an oscillating plate at different oscillation frequencies. The damping forces are then used to calculate nondimensional damping ratios. The damping ratios are used in making comparisons among the models and with experimental data. The experiment used an oscillating MEMS plate suspended by folded springs. The substrate (base) was shaken with a piezoelectric transducer. The plate vibrated as a result, especially at the resonant frequency. The velocities of the suspended plate and of the substrate were measured with a laser Doppler vibrometer and a microscope. Experimental modal analysis gave the damping ratio. To achieve a wide range of squeeze numbers, the experiment was repeated under several different pressures. The measurement was also repeated on an array of plates. Experimental data indicate that, for atmospheric and higher pressures, squeeze-film damping forces can be modeled accurately with a very simple model. For lower pressures in the continuum regime, a more complete model by Veijola (2004) predicts the damping ratio very well.
A Constant Delivery Micropump Using Surface Tension and Thermopneumatic Pressure
Authors: Jun Do Han , Sim Woo Young , Yang Sang-Sik , Pak James Jungho
Published: April 2008

This paper presents the fabrication and test of a constant delivery thermopneumatic micropump made of PDMS without any moving part. The driving force of the liquid discharge is the pneumatic pressure of heated air and the suction of liquid is accomplished by the surface tension. The proposed micropump consists of an inlet, an outlet, a pump chamber, two air chambers, two air discharge channels and two air suction channels. The air chambers have electric heaters on the Pyrex glass substrate. Each air chamber is connected the pump chamber through two different air channels which behaves like check valves. The micropump is fabricated through the spincoating process, the lithograph process, the PDMS molding process and etc. The total dimension of the micropump is 11.7 × 8.8 × 0.7 mm3. The discharge volume of the fabricated micropump was measured for various backward pressures ranging from 0 to 20 cmH2O. The micropump discharges 116 nanoliters in 4 seconds for zero discharge pressure when the input voltage is 3.5 V. As the discharge pressure increases, the discharge volume decreases gradually. The discharge volume deviation is less than 15 percent for the discharge pressure range between 5 and 15 cmH2O. This proposed micropump is feasible for disposable transdermal drug delivery systems.
Optimization of Working Ground Heat Storage With Seasonal Regeneration
Authors: Olszewski Pawel
Published: April 2008

The aim of the research was an optimization of long-term heat storage with seasonal regeneration. Energy consumption for central heating during wintertime, transfererred from ground energy storage using a heat exchange device, is the operating principle of such systems. Warmed working fluid is then used in a heat pump system. However, more accurate calculations showed that over time of usage, there is a trend toward cooling at deeper round layers. Such a situation leads to a lowering of ground potential when using heat pump systems. A possible solution to this problem is the application of summer regeneration: during summer months, the working fluid is firstly warmed in solar collectors, and then forced into the same boreholes. The numerical model of a vertical, ground heat exchange device (configured as a "pipe in pipe", known as a Fields' pipe) was specially developed. Temperature distribution of the working fluid along the pipe was one of the boundary conditions, for the co-axial, time-variable, heat conduction task, which described the heat flow in energy storage. The numerical simulation of solar collectors work was based on the Hottel - Whillier - Bliss equation, in which energy flow from the solar collector is calculated, dependant on external parameters such as: insulation or ambience temperature. The combination of three computational parts- the ground heat exchange device, energy storage area and solar collectors battery- allows the target function to be defined for task optimization. The subject of optimization was an energy quantity, which can be taken from energy underground storage, and then utilized by the heat pump system. In the summarized paper, a combination of the input data, which influenced the efficiency of energy storage, was chosen. Hypothetical data were: outside diameter and length of heat exchange device, distance between pipes, fluid flow through the pipe during charge and discharge processes or temperature of inlet working fluid. The influence of individual parameters on the target function, holding all input data constant, was analyzed. A developed evolutionary numerical code known as GENOCOP I (GEnetic algorithm for Numerical Optimization for COnstrained Problems) [3] was used for optimization. After preliminary correction of boundary values of the input data, nine attempts of optimization were taken up. The research results identified optimal values of input parameters for which maximum energy could be taken from ground storage.
Modeling and Experimental Verification of Torque Ripple in Permanent Magnetic DC Motors
Authors: Lovett Benjamin A. , Chiu George T.-C.
Published: April 2008

In this paper we have developed a simple parametric model based on motor geometries to estimate the torque ripple in permanent-magnet DC (PMDC) motors. Torque ripple is the combined results of many different motor design parameters such as magnetic material properties and geometry as well as rotor slot geometry. As the PMDC motors are being used in more precision applications while being produced at a lower price, the effect of torque ripple is becoming an important issued for precision motion control. The main objective of this study is to identify motor parameters that affect the magnitude of the torque ripples as well as developing a cost effective measuring device for motor vendors. The analytical model focused on the effect of air gap volume on effective magnetic flux and in terms impact the torque generation. The effectiveness of the proposed model was verified by experimental data collected with motors from four large volume motor vendors that meets the same design specification. Sensitivity analysis was also performed to identify the key motor parameters that impacted the magnitude of the torque ripple.
An Undergraduate Laboratory: The Effect of Nanoparticle Self Assembly on the Electrical and Mechanical Properties of Nanocomposites
Authors: Creasy T. S. , Grunlan J. C. , Griffin R. B.
Published: April 2008

Recent research into the effect of nanoparticle organization on the electrical properties of nanocomposite films was used to create a hands-on laboratory for undergraduate education in nanomanufacturing. Students created two composites using solvent-based solution and polymer emulsion to show that a non-random microstructure can produce the required electrical conductivity with less added nanoparticles. Students evaluated the materials by 4-point probe and scanning electron microscopy.
Structure and Tribological Properties of Ultra-Thin Tetrahedral Amorphous Carbon (ta-C) Films
Authors: Lu Xinchun , Wang Hui , Zhang Chenhui , Luo Jianbin
Published: April 2008

Ultra-thin tetrahedral amorphous carbon (ta-C) films were deposited by the filtered cathodic vacuum arc (FCVA) technique. The thickness, structure, and topography of the films were studied by various analysis methods, such as auger electron spectroscopy (AES) depth profile, high resolution transmission electron microscope (HRTEM), Raman spectroscopy, and atomic force microscopy (AFM). A tribometer was used to investigate the tribological properties of the ta-C films. The results indicate that ta-C film with thickness less than 2 nm can be obtained by the FCVA technique. As the film thickness increases the relative intensity ratio ID/IG decreases, which means that sp3 bond in the films increases. The oxide layer cleaning procedure of silicon substrate before deposition influences the growth mode and surface roughness of the films. The ultra-thin ta-C film has the lowest friction coefficient of 0.19 and excellent anti-wear properties.