bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Direct Deformation Measurement System to Enhance Positioning Accuracy of Machine Tools
Authors: Bosetti Paolo , Biral Francesco , Bertolazzi Enrico , De Cecco Mariolino
Published: April 2008

The positioning accuracy of computer numerical control machines tools and manufacturing systems is affected by structural deformations, especially for large sized systems. Heat induced deformations, long-period deformation of foundations, and the manufacturing process itself, cause time-dependent structural deformations of the machine body, which are difficult to model and predict. In fact, the feasibility of a model-based error prediction is often limited by the complexity of the problem from both the geometrical and the physical point of view. As a consequence, only limited success has been achieved in active error compensation based on the modeling of the relationship between the generalized dynamic loads and the structural deformation field. This paper illustrates a different approach in active error compensation, which exploits a new measurement system, currently in the patenting process, able to measure, in real time, the machine structural displacement field, without any model for the dynamic structural behavior. The first part of the paper illustrates the working principle of the measurement system, which can be described as coupled hardware and software subsystems. The hardware subsystem is basically a triangular mesh of struts, whose nodes are rigidly connected to the underlying structure under measurement. The struts are instrumented with Fibre-optic Bragg Gratings providing their longitudinal strain values. The software part is an algorithm, which evaluates the discrete displacement field by computing the node positions on the basis of the strut longitudinal deformations. The second part of the work focuses on the performance, in terms of accuracy, resolution, and time stability, of a prototype of the above described measurement system. Finally, the third part illustrates two major enhancements on the system design: the design of a monolithic variant of the reticular structure (with higher performances and reduced cost), and a different computation algorithm providing increased accuracy and limited error propagation.
Effect of Centrifugal Force on Frequency Characteristic of Rotating Hollow Cylinders Using a Newly Designed Cylindrical Super Element
Authors: Bonakdar M. , Ahmadian M. T.
Published: April 2008

A sixteen node cylindrical super element is presented for evaluating the free vibration characteristics of a rotating laminated cylinder with conventional boundary conditions. It is shown that the natural frequencies are affected considerably when the centrifugal force is also taken into account. The vibration frequencies of rotating finite cylinder, obtained by conventional finite element are used to evaluate the accuracy of this approach. The special case of a stationary cylinder with zero spinning velocity is also considered as a check on this method. Results indicate only few number of cylindrical super elements are capable of predicting the natural frequency of the rotating cylinder within the same limit as many elements used in the conventional finite element method.
Modeling and Testing of a New Polymer-Based Impact Tool Design to Reduce Noise, Vibration and Biomechanical Injuries
Authors: Konchar Janelle , Popper Peter , Griffith Matthew , Glancey James
Published: April 2008

A new power impact tool design has been developed and tested using advanced engineering polymers to replace traditional metal components. The new polymer-metal impact mechanism generates less noise, lower vibrations, and potentially reduces biomechanical injuries. Power tools are known to cause several medical ailments including Hand-Arm Vibration Syndrome (HAV), Raynaud's phenomenon, and Vibration White Finger unless the daily exposure and/or dosage is limited. To evaluate the effects of a polymer-metal impact mechanism on tool performance, a non-linear model describing the equations of motion and resulting output forces were developed. In addition, a number of experiments with a high frequency Instron test machine and prototype tools were performed to validate the model and compare performance of conventional power tools to the new polymer based design. The results show that although adding a polymer does reduce noise and vibration, the reduction in impact force is relatively small and statistically insignificant. Various polymer materials and shapes were evaluated and results show that for durability and performance, the optimum appears to be a plug inserted in a cavity in either the piston or the cutting tool, thus creating a state of confined compression on the polymer. The polymer used in this research was Minlon® (mineral reinforced Nylon66), and durability was improved when the polymer inserts were cycled with compressive loads before use in the power tool.
High Thermal Conductivity of Diamond Nanofluids and its Effect on the Heat Transport Capability in an Oscillating Heat Pipe
Authors: Wilson Corey , Ma Hongbin , Park K.
Published: April 2008

In heat exchangers and liquid cooling devices the thermal conductivity of the liquid is an important factor in their design. Recently it has been shown that adding small amounts of nanoparticles to the liquid can significantly increase the thermal conductivity of the fluid [1]. This study investigates the thermal conductivity of diamond nanofluid. The nanofluid is HPLC grade water with 1% by volume diamond nanoparticles that are 5-50 nm in diameter. The thermal conductivity was measured by the transient hot-wire method. In order to verify the experimental measurement, the thermal conductivity of pure water (HPLC grade) was conducted and the measurement error is 3.6%. The experimental results show that the diamond nanoparticles can enhance the thermal conductivity of nanofluid. At an ambient temperature of 21 °C, the thermal conductivity for nanofluid was determined to be 1.00 W/m-K comparing with the thermal conductivity of 0.60 W/m-K for pure water (HPLC grade). Therefore, the nanofluid provides a significant increase in thermal conductivity. Utilizing this nanofluid, an oscillating heat pipe was developed and tested. Experimental results showed that when the oscillating heat pipe is charged with diamond nanofluids, the increase in heat transport capability can be significant and highly dependent on the operating temperatures.
A Port Injection Process for Improved Resin Delivery and Flow Control in Vacuum-Assisted Resin Transfer Molding
Authors: Fuqua Michael , Glancey James L.
Published: April 2008

Vacuum Assisted Resin Transfer Molding (VARTM) is used to produce high quality composite parts at lower cost than other manufacturing methods. However, traditional VARTM injection methods are incapable of accounting for variations in preform permeability within a mold. As a result, creating complex components is a labor intensive and expensive process often requiring a trial and error approach to insure complete infusion of the preform fibers. To address this limitation, a new system for delivering resin to a VARTM mold using a series of ports in the tooling surface rather than traditional injection lines has been developed. A port injection process has been designed that utilizes a closed loop control system of ports and sensors built into the mold. Finite element models of this new process indicate complete infusion can consistently be achieved, even for mold lay-ups with large variations in permeability. Results indicate the system is capable of identifying and accounting for preform variability, and correctly delivering resin to low permeability regions usually unfilled with conventional VARTM. In addition, this new technique significantly reduces lay-up time and total time to infuse a part. Experiments with a prototype lab-scale mold have been used to validate the performance of this new injection process. Unlike a conventional VARTM setup, the innovative port injection process can deliver resin to any location within the mold, thus reducing the potential for dry regions and improving part quality and consistency.
Transient Behavior of Hydrogen Permeation Through Pd/Ag Alloy Micro/Nano Membranes
Authors: McLeod Logan S. , Degertekin Levent F. , Fedorov Andrei G.
Published: April 2008

Separation of hydrogen from the reaction products stream leaving a fuel processor is an essential step prior to its introduction to the fuel cell. To this end, we are developing micromachined Palladium-Silver alloy micro/nano membranes for in-situ hydrogen separation suitable for integration with catalytic fuel reforming microreactors. Although achieving the maximum steady-state hydrogen flux across these membranes is the most important design goal, a detailed understanding and control of the transient process from the starting (no permeation) conditions to the nominal steady-state are critical for effective utilization of H2-separating membranes in a distributed power scheme. In our previous work (McLeod et al., Proceedings of ASME 2005 Summer Heat Transfer Conference, San Francisco, CA) a steady-state model was developed which divides the hydrogen permeation sequence into seven distinct regimes: gas phase mass transport to the surface, adsorption onto the surface, transition into the bulk material, solid-phase diffusion through the bulk material, transition to the effluent surface, desorption into the gas phase and diffusion away from the surface. This presentation investigates the kinetics of each permeation step in order to understand and predict the transient behavior of thin Pd/Ag alloy membranes exposed to varying hydrogen concentration gradients and to establish the rate-limiting step(s). Possible explanations for observed long-term transient behavior, on the order of several hours, will also be discussed. In addition to transient behavior of the Pd/Ag membranes, the design and effects of critical geometric parameters for the membrane test fixture will also be discussed. In order to accurately measure the true performance of a gas permeable membrane, it is critical to minimize changes in partial pressure and the effects of gas-phase mass diffusion across the membrane surface. To quantify these effects three time scales have been defined; flow time, chemical time and diffusion time. The importance of the relative values of these time scales will be discussed for the ideal membrane test fixture.
Computational and Experimental Comparison of Tube Wall Heat Transfer Augmented by Winglets in Louvered Fin Heat Exchangers
Authors: Lawson Michael J. , Sanders Paul , Thole Karen A.
Published: April 2008

Louvered fins are used in compact heat exchangers to increase heat transfer by interrupting thermal boundary layer growth thereby increasing the convective heat transfer coefficients and reducing the air side resistance. Recently, it has been experimentally shown that heat transfer along the tube wall can be augmented by the placement of delta winglets on the louvers at an angle to the flow. The focus of this combined experimental and computational study is to determine the effect of realistic winglets on tube wall heat transfer. Comparisons of the computational simulations were made to the experimental results, which were obtained using a twenty times scaled model. Winglet performance characteristics were studied on solid louvers and pierced louvers whereby the latter simulates what would occur for a manufactured louver having a winglet. For a solid louver having a winglet, the tube wall heat transfer augmentation was found to be as high as 5.4%. Pierced louver cases were observed to produce slightly higher heat transfer augmentations than solid louver cases. Computational results suggest that the mechanism behind tube wall heat transfer augmentation is flow redirection and not winglet induced vortices.
Femtosecond Laser Micromachining as a Rapid Prototyping Environment: System Development and Initial Results
Authors: Uppal Nitin , Shiakolas Panos S. , Belligundu Sunil
Published: April 2008

Femtosecond laser micromachining (FLM) is a fairly new and novel technology for 3-D processing of engineering materials without the constraints associated with traditional micromachining based on Si technologies. FLM has shown great promise in rapidly fabricating components at a microscale and that it can also be used to machine on an array of engineering materials both metals and non-metals for variety of applications. This work presents the development of a FLM environment equivalent to a 3 DOF CNC machine with the laser beam acting as the machine tool. The environment includes a Ti:Sapphire laser (800 nm wavelength and 120 fs pulsewidth), various optics for beam guidance and power control and three mutually perpendicular motorized stages (8 in travel with 0.05 μm resolution of motion and capable of executing industry standard G-codes). A postprocessor for generating the G-codes using CAD/CAM software is successfully customized. Subsequently, the results of an ablation study for common engineering materials and its usage in defining machining parameters for rapid prototyping of various thermal actuators will be presented along with examples of microcomponent fabrication.
A Numerical Investigation of NOx Formation in Counterflow CH4/H2/Air Diffusion Flames
Authors: Guo Hongsheng , Neill Stuart W. , Smallwood Gregory J.
Published: April 2008

A detailed numerical study was carried out for the effect of hydrogen enrichment on flame structure and NOx formation in counterflow CH4/air diffusion flames. Detailed chemistry and complex thermal and transport properties were employed. The enrichment fraction was changed from 0 (pure CH4) to 1.0 (pure H2). The result indicates that for flames with low to moderate stretch rates, with the increase of the enrichment fraction from 0 to 0.5~0.6, NO emission index keeps almost constant or only slightly increases. When the enrichment fraction is increased from 0.5~0.6 to about 0.9, NO emission index quickly increases, and finally NO formation decreases again when pure hydrogen flame condition is approached. However, for flames with higher stretch rates, with the increase of hydrogen enrichment fraction from 0 to 1.0, the formation of NO first quickly increases, then slightly decreases and finally increases again. Detailed analysis suggests that the variation of the characteristics in NO formation in stretched CH4/air diffusion flames is caused by the change of flame structure and NO formation mechanism, when the enrichment fraction and stretch rate are changed.
Enabling Variation of Manufacturing Process Parameters in Early Stages of Product Development
Authors: Boart Patrik , Isaksson Ola
Published: April 2008

Currently, mechanical design of aero engine structural components is defined by dimensioning of Design Parameters (DP's) to meet Functional Requirements (FR's). FR's are typically loads, geometrical interfaces and other boundary conditions. Parameters from downstream processes are seldom actually seen as DP's. This paper proposes that downstream process parameters are treated as DP's which calls for engineering methods that can define and evaluate these extended set of DP's. Using the proposed approach manufacturing process alternatives can be used as DP's in early stages of product development. Both the capability to quantitatively assess impact of varying manufacturing DP's, and the availability of these design methods are needed to succeed as an early phase design method. One bottleneck is the preparation time to define and generate these advanced simulation models. This paper presents how these manufacturing process simulations can be made available by automating the weld simulation preparation stages of the engineering work. The approach is based on a modular approach where the methods are defined with knowledge based engineering techniques-operating close to the CAD system. Each method can be reused and used independently of each other and adopted to new geometries. A key advantage is the extended applicability to new products, which comes with a new set of DP's. On a local level the lead time to generate such manufacturing simulation models is reduced with more than 99% allowing manufacturing process alternatives to be used as DP's in early stages of product development.
CBR-DFMA: A Case-Based System Used to Assembly Part Design in the Early Design Stage
Authors: Chang Guanghsu A. , Su Cheng-Chung , Priest John W.
Published: April 2008

Many conflicting issues exist between product design and manufacturing department. In the early design stage, designers often do not have enough expertise to successfully address all these issues. This results in a product design with a low level of assemblability and manufacturability. Hence, an intelligent decision support system is needed for early design stages to improve a design. This paper proposed a web-based intelligent decision support system, CBR-DFMA, connecting with a case base, database and knowledge base. Early experimental results indicate that potential design problems can be detected in advance, design expertise can be effectively disseminated and effective training is offered to designer by employing this system.
Measurements of the Mechanical Properties of Freestanding Nanoscale Membranes
Authors: Leseman Zayd C. , Jeong Hae-Kwon , Mackin Thomas J. , Masel Richard I. , Begley Matthew
Published: April 2008

We present experimental measurements of the mechanical properties of nanoscale-thick materials using a recently developed free-standing membrane test. Freestanding membranes of gold and a nano-porous silicate were centrally deflected using a spherical indenter attached to a microfabricated fixed-fixed beam device. Experiments of this type allow us to extract mechanical properties of the thin films without the complicating effects of the substrate, enabling accurate study of length scale effects. These experiments differ from previous work by testing freestanding films and by including the finite contact size of the indenter tip.
Cure Optimization in Pultrusion Process by a Heuristic-Analytical Approach
Authors: Palazzo Gaetano S. , Carlone Pierpaolo
Published: April 2008

This paper deals with a hybrid optimization of the degree of cure and temperature field into the work piece during the pultrusion manufacturing process. The procedure is based on the consecutive application of a heuristic technique (Genetic Algorithms), with an analytical method (simplex technique), to minimize an opportunely defined fitness function. The objective function measures the uniformity of the degree of cure, with a satisfactory mean value, in the exit cross section of the forming die, taking into account constraints related to the degradation of the processing resin system, due to an exothermic peak temperature major than the carbonisation temperature of the polymeric matrix. Optimal values of the temperatures of the die heating platens have been evaluated by applying the proposed procedure to a three dimensional thermo-chemical numerical model, solved using a finite difference scheme. The robustness of the developed optimization procedure has been tested using several combinations of process parameters, such as temperature of the resin bath, temperature of the die cooler, and composite material pull speed. A finite element model is used to analyze temperature field and degree of cure profiles after the optimization of the temperatures of the heating platens. The proposed procedure can be used as a good tool to optimize part quality or productivity, for the conventional pultrusion process, as well as, for post die shaping pultrusion, in which the processing part is completely formed out of the heating die and material cure is then completed using U.V. rays or other heating sources.
Direct Simulation Monte Carlo Analysis of Microscale Field Emission and Ionization of Atmospheric Air
Authors: Go David B. , Fisher Timothy S. , Garimella Suresh V.
Published: April 2008

Ionic winds are formed when air ions are drawn through the atmosphere by applied electric and/or magnetic fields. The ions collide with neutral air molecules, exchanging momentum, causing the neutral molecules to move. Continued collisions and momentum exchanges generate a net flow called an ionic wind [1]. Ionic winds formed near flat plates can produce local boundary layer distortion in the presence of a bulk flow. This concept has been studied experimentally at the macroscale as a method for drag reduction [2] and has been suggested at the microscale for convective cooling enhancement [3]. Specifically, microfabricated ion wind engines can be integrated onto electronic chips to provide additional local cooling at "hot-spot" locations. In our previous work, continuum modeling of the ionic wind phenomena showed an approximately 50% increase in the local heat transfer coefficient at the location of the ion wind engine [3]. However, in that work, ionization physics were not modeled, rather assumptions for ion current and concentrations were used as a basis for modeling ion transport. At the microscale, ionization occurs when field-emitted electrons from closely spaced electrodes collide with neutral air molecules, stripping away electrons and forming molecular ions. Geometric enhancement of the electrodes using nanostructured materials enables low ionization voltages conducive to microelectronic devices. Understanding the microscale ionization process is necessary to accurately predict the ensuing ionic wind and cooling. Direct Simulation Monte Carlo (DSMC) is used in the present work to predict field emission between two planar electrodes and the consequent ionization of the interstitial air.
Performance and Emission Characteristics of a Diesel Engine Using Catalysts With Exhaust Gas Ricirculation
Authors: Walke P. V. , Deshpande N. V. , Mahalle A. K.
Published: April 2008

Testing of catalytic converter with exhaust gas recirculation system for diesel engine to reduce pollute gases is chosen for present work. The emphasis is given on hydrocarbon (HC), carbon monoxide (CO) and oxides of nitrogen. The catalytic converter was developed with variations of catalyst plates. Perforated plates of copper and combination of copper oxide and cerium oxide (CeO2 +CuO) were used as the catalyst. Copper spacer was used in between plates to vary the distance. Secondary air was injected into the converter to aid oxidization of HC and CO. Experimental study was carried out on computerized kirloskar single cylinder four stroke (10 B.H.P, 7.4 KW) diesel engine test rig with an eddy current dynamometer. The converter was tested with various combination with exhaust gas re-circulation (EGR) system. There are some improvements in the reduction and conversion efficiency of HC & CO. Exhaust gas re-circulation has proved to be effective in reducing NOx.
Quantitative and Qualitative Comparison of Low-Temperature, Heat-Activated Cooling Systems
Authors: Gupta Y. , Metchop L. , Frantzis T. , Phelan P. E.
Published: April 2008

This paper compares the quantitative and qualitative performances of three different heat-activated cooling systems, e.g. a silica-gel water adsorption system, a LiBr-H2O absorption system, and a desiccant air system. Each of these systems can be utilized at relatively low heat source temperatures, but it is unclear which of these systems is best suited to what range of heat source temperature. Our study explores answers to this question by generating quantitative results comparing their relative thermal performance, i.e. COP and refrigeration capacity, and a qualitative comparison based on the size, maturity of technology, safe operation, etc. Each of these systems is assumed to work under the following operating conditions: a condensing temperature of 29 °C, an evaporating temperature of 19 °C, a hot water temperature range of 40-120 °C, and a hot water mass flow rate of 0.4 kg/sec. Individual mathematical models are developed for each system and numerically solved using different techniques. In order to provide a fair comparison between the fundamentally different systems, a UA (overall heat transfer coefficient multiplied by the heat transfer area) value of 1.0 kW/ °C is considered for the heat exchanger that transfers heat from the supplied hot water. Furthermore, to compare systems of similar size, the mass of silica gel in adsorption and desiccant system and mass of LiBr-H2O solution in absorption system were specified such that each system provides the same amount of refrigeration (8.0 kW) at a source temperature of 90 °C. It is found that the absorption and adsorption cooling systems have a higher refrigeration capacity at heat source temperatures below 90 °C, while the desiccant air system outperforms the others at temperatures above 90 °C.
External Heating Effects on te Effectiveness-NTU Relationship of a Counterflow Microchannel Heat Exchanger
Authors: Mathew B. , Hegab H.
Published: April 2008

The effect of external heating on the effectiveness of microchannel heat exchangers is experimentally studied in this paper. Two stream symmetric, indirect-contact counterflow microchannel heat exchangers were fabricated that provided a range of NTU values from 0.35 to 1.44. Results are presented as a plot between two nondimensional terms (effectiveness and NTU), there by generalizing the results for application to any coolant and microchannel heat exchangers. The heat exchangers were tested for balanced flow condition by supplying external heating at rates of 0%, 15% and 25% with respect to the maximum heat transfer rate thermodynamically possible between the two fluid streams. The heat exchanger effectiveness was reduced by 11-16% and 16-27% by the applied 15% and 25% external heating rates, respectively.
A Standard Approach for Measuring Adhesion Energies in Stiction-Failed Microdevices
Authors: Leseman Zayd C. , Carlson Steven , Xue Xiaojie , Mackin Thomas J.
Published: April 2008

We present results from a new procedure developed to quantify the pull-off force and strain energy release rates associated with stiction-failure in microdevices. The method is analogous to a standard, macro-scale peel test, but carried out using micro-scale devices. Adhesion is initiated by lowering an array of microcantilevers that protrude from a substrate into contact with a separate substrate. Displacement is controlled by a piezo-actuator with sub-nm resolution while alignment is controlled using linear and tilt stages. An interferometric microscope is used to align the array and the substrate and to record deflection profiles and adhesion lengths during peel-off. This geometry is accurately modeled using linear elastic fracture mechanics, creating a robust, reliable, standard method for measuring adhesion energies in stiction-failed microdevices.
Virtual Instrumentation and Virtual Experimentation
Authors: Fakheri Ahmad , Abou-Zaid Wael , Abou-Hanna Jeries
Published: April 2008

A Virtual Instrument (VI) that is developed to acquire and analyze data from a physical system can be disconnected from the system and modified into a Virtual Experiment (VE). This can be achieved by replacing the input to the sensors with values that are arrived at by modeling the system. To be able to develop virtual experiments in thermodynamics, fluids or heat transfer, VIs are needed for the determination of thermodynamic and transport properties of different substances. The code REFPROP by NIST is used to develop the needed VIs for determining the thermodynamic and transport properties. The enhancement of the experimentation with virtual experiments is developed for an experimentation course where students perform experiments virtually and then make the transition to the actual lab and conduct experiments that mirror the virtual one.
Model-Based Fault Detection and Isolation in Automotive Electrical Systems
Authors: Scacchioli Annalisa , Rizzoni Giorgio , Pisu Pierluigi
Published: April 2008

This paper deals with the design and validation, through simulation in a Matlab/Simulink and SABER environment, of model-based diagnostic algorithms for an automotive electric power generation system (EPGS). The EPGS includes alternator with rectifier, a battery, and a voltage regulator. The mathematic models of these subsystems, based on the physics of the processes involved, consist of time-varying nonlinear ODEs. The diagnostic problem focuses on the detection and isolation of a specific set of alternator faults, including belt slipping, rectifier fault and voltage regulator fault. An in-depth analysis of the models is conducted in order to understand the effects of different failure modes on system performance; subsequently, an equivalent input-output model of the alternator is formulated and parameterized. The equivalent model permits considerable simplification of the algorithms. The proposed diagnostic approach is based on the generation of residuals obtained using system models and comparing the predicted and measured value of selected variables, including alternator output current, field voltage, battery current, battery voltage and battery temperature. This paper presents the models, diagnostic algorithms and simulation results.
A Study Toward Minimum Spatial Discretization of a Fuel Cell Dynamics Model
Authors: McCain B. A. , Stefanopoulou A. G. , Butts K. R.
Published: April 2008

The 24-state fuel cell water dynamics model from [1] is cast into a Dymola™ icon-based formulation, with flexible library sub-models specific for this application. Through and across (flow and effort in bond graph terminology) variables are identified and analyzed for all relevant energy-using components. The objective is to establish the necessary model order for the fuel cell model using an energy-based measure called activity [2]. Additionally, we analyze the effect that input variation (duration, initial/final time) has on calculation and implementation of the activity. Explanation of the importance of accurate water vapor concentration gradient modeling is covered. Finally, we show that the minimum degree of discretization for each constituent within the model should be determined separately in order to generate the simplest model representation, and that the optimal discretization can be different for each species.
Polaritons in a Piezoelectric Superlattice Plate
Authors: Chou Yuan-Fang , Yang Ming-Yi
Published: April 2008

A periodic structure is formed in a piezoelectric plate by intervallic polarizing oppositely along one direction. Wave propagation in this structure are studied with plane-wave expansion method. The polariton behavior in the plate is observed by solving Newton's equations of motion and Maxwell's equations simultaneously. Significant coupling between phonon and photon occurs in the vicinity of the center of the first Brillouin zone. By studying the band structure and field patterns, the resonance phenomenon can be explained. Adjusting the periodicity and thickness of the superlattice, the polariton behavior can exist in the frequency range of RF band. Since the polariton in the piezoelectric superlattice can be excited by electromagnetic waves, it can be applied to transducers and filters.
Study of Single Pixel Evaluation for Experimental Measurements in a Microchannel
Authors: Chuang Han-Sheng , Wereley Steve T. , Gui Lichuan
Published: April 2008

A newly proposed algorithm named single pixel evaluation (SPE) has been developed to increase the resolution of micro-PIV to its physical limit of one pixel. Despite the SPE is able to improve the resolution significantly in comparison with conventional cross-correlation, some phenomenon are still unknown due to its infancy, resulting in discrepancies between the analytic predictions and the experimental measurements. To provide reliable rules as applying the SPE, an overall inspection of the algorithm's behaviors is essential. This paper investigated five general factors, determining their performances via synthetic particle images subjected to a parabolic flow profile. The factors include particle image quality, particle image density, search radius (SR), particle image displacement, and particle image diameter. The results indicate that the particle image quality behaves the most significantly among the factors. Moreover, the SPE was also compared with the fast Fourier transform based cross-correlation (FFT-CC) under the equivalent signal-to-noise ratio (SNR). The tendencies of optimal values with respect to different factors are revealed in the following text. To complete the study, experiments on a straight microchannel were implemented to verify the observations from the simulations. The measured images which followed the suggested rules show better results than the other ones.
Utilization of Immersive Collaborative Student Laboratory Simulations Developed Using a Game Engine
Authors: Chang Chenghung P. , Arango Felipe , Kodman Dror , Esche Sven K. , Chassapis Constantin
Published: April 2008

Recently, commercial game engines and the associated software development kits have reached a level of maturity where it becomes feasible to rapidly and efficiently develop and deploy software for generating virtual environments. This paper will discuss the various possible ways of developing interactive multiplayer simulations for student laboratory instruction and professional training. Instead of developing software from the ground up, an existing commercial game engine and its corresponding software development kit (SDK) can be used as development tools for building such educational content. In doing so, the developers can take advantage of the game engines' advanced methods for generating animated graphics, simulating physical interactions between 3D objects, as well as facilitating multiplayer dynamics. Based on this approach, various usage scenarios can be developed cost-effectively. These can then be explored by the students or trainees in an inherently safe and immersive manner. Furthermore, the educational content can be tailored to address the students' different learning modalities. A number of predefined scenarios can be constructed, which exercise the students' problem solving skills by mimicking typical problems that might occur when carrying out actual hands-on experiments. In addition, the experimental scripts imbedded within the system allow one to monitor - and possibly even enforce - active participation and collaboration by all students of a laboratory group, which are considered two crucial factors in improving learning. This multi-disciplinary research is being carried out at Stevens Institute of Technology (SIT) with funding from a multi-year grant by the National Science Foundation's Information Technology Research program.
Development of Process for Wafer Scale Encapsulation of Devices With Very Wide Trenches
Authors: Ayanoor-Vitikkate Vipin , Chen Kuan-Lin , Park Kuan-Tae , Kenny Thomas W.
Published: April 2008

A Wafer scale encapsulation process has been developed for devices that require wide gaps. In this experiment, we focus on devices that have gaps or trenches 10-20μm wide. This process can also be applied to larger gaps of the order of 50-100μm. The chief focus of the process development is to achieve a wafer scale encapsulation technique, which can avoid deposition of very thick LPVCD oxide. Once the processing and encapsulation is carried out, SEM images are taken to ensure that the device is completely released and no sacrificial material is left behind.
A Viscoplastic Constitutive Model for Polyurethane Foams
Authors: Neilsen Mike , Lu Wei-Yang , Olsson Bill , Hinnerichs Terry
Published: April 2008

A series of experiments was recently performed to characterize the mechanical response of several different rigid polyurethane foams to large deformation. In these experiments, the effects of load path, loading rate, and temperature were investigated. Results from these experiments indicated that rigid polyurethane foams exhibit significant volumetric and deviatoric plasticity when they are compressed. Based on these experiments, a foam plasticity model that captures volumetric and deviatoric plasticity was developed. This model has a yield surface that is an ellipsoid about the hydrostat. These polymeric foams were also found to be very strain-rate and temperature dependent. Thus, a new viscoplastic foam model was developed to describe the mechanical response of these foams to large deformation at a variety of temperatures and strain rates. This paper includes a description of recent experiments and experimental findings. Next, development of a foam plasticity model and a viscoplastic foam model is described. Finite element simulations with the new models are compared with experimental results to show behavior that can and cannot be captured with these models.
Experimental Study on Cancelling Self-Excited Vibrations by Parametric Excitation
Authors: Dohnal Fadi , Paradeiser Wolfgang , Ecker Horst
Published: April 2008

This article reports on the experimental verification of an anti-resonance effect obtained by parametric stiffness excitation. From theoretical studies it is known that parametric excitation at non-resonant parametric resonances can improve the damping behavior of a mechanical system and even stabilize an otherwise unstable system. To demonstrate this effect, a test setup was designed, based on a two-mass vibration system, gliding on an air track. Parametric stiffness excitation (PSE) was realized by a mechanical device that creates a time-periodic stiffness by modulating the tension in an elastic rubber band. With this device it was possible to demonstrate the improved damping behavior of the system when the PSE device is operating at or near the first parametric combination resonance of difference type. Also, a simple electro-magnetic device was used to create self-exciting forces. It could be shown for the first time that it is indeed possible to stabilize the unstable system by introducing parametric stiffness excitation.
Emission Characteristics of Syngas Flames
Authors: Som Sibendu , Ramirez Anita I. , Aggarwal Suresh
Published: April 2008

Synthesis gas or "Syngas" is being recognized as a viable energy source worldwide, particularly for stationary power generation due to its wide flexibility in fuel sources and superior pollutants characteristics. Although its composition may vary significantly, it generally contains CO and H2 as the dominant fuel components with varying amount of methane and diluents. There are, however, gaps in the fundamental understanding of syngas combustion and emissions, as most previous research has focused on flames burning individual fuel components such as H2 and CH4, rather than syngas mixtures. To ensure the environmental feasibility of syngas, the harmful emission, especially NOx, must comply with current and future regulations. In addition, the combustion of syngas occurs at elevated pressures and inlet temperatures. Most published research has considered the combustion of syngas constituents at atmospheric conditions. This paper presents a numerical investigation to gain fundamental understanding of combustion and emission characteristics of syngas with varying composition, pressure and inlet temperatures. Two representative syngas fuel mixtures, 50% H2/50% CO and 5% H2 / 95% CO (% vol.), are chosen based on fuel composition data from multiple power generation plants worldwide. Three detailed chemical kinetic models are used namely, GRI 3.0, Davis and Dryer mechanisms. Results indicate that for both representative mixtures an increase in reactant temperature leads to a significant increase in NOx due to increase in flame temperature caused by an increase in inlet temperature. As the pressure is increased from 1 to 6 atm, the peak NO increases rapidly, and then becomes nearly independent of pressure. This can be attributed to a similar trend in radical species responsible for NO production such as HCN and OH which both show the most significant increase at low pressures. The emission index for these flames is also found to follow a similar behavior with pressure.
Numerical Simulation of Gas-Liquid Two Phase Flow in the Annular Gap Scrubber
Authors: Li Longjian , Cui Wenzhi , Chen Qinghua , Jen Tien-Chien , Liao Quan
Published: April 2008

The pressure drop characteristics of the annular gap scrubber of the blast furnace gas are key elements for inner furnace pressure control. In the annular gap scrubber, there exists complicated interactions between three-dimensional compressible flow with two phase flow and heat transfer between gas and water particle. In the paper, the gas-liquid two-phase flow and heat transfer process in the annular gap scrubber are analyzed and the corresponding physical and mathematical models are proposed. The computational model is discretized with hybrid meshes into multi-block zones, and solved numerically by employing the Fluent solver. The motion of the water particles in the annular gap scrubber is simulated by the Lagrangian discrete phase model, meanwhile the interaction between two phases is taken into consideration. The numerical computations of the two-phase flow and heat transfer in the annular gap scrubber are performed under different mass flow rates, displacements of AGE (Annual Gap Element), and water-gas ratios. Based on the computed results under different conditions, the flow and pressure drop characteristics of the annular gap scrubber are illustrated and analyzed. The results can be used as the basis for the pressure control policy of the blast furnace.
Thermodynamic Model for the Sensing Behavior in Ferromagnetic Shape Memory Ni-Mn-Ga
Authors: Sarawate Neelesh N. , Dapino Marcelo J.
Published: April 2008

A magnetomechanical model for the sensing effect in the ferromagnetic shape memory alloy (FSMA) Ni-Mn-Ga is presented. The model is based on continuum thermodynamics with the constitutive response being derived from the total (magnetic and mechanical) free energy. The model predicts the stress-strain and induction-strain response at various bias fields. Only two experiments are required to obtain the model parameters.
Flow Boiling in a Silicon Microchannel Array
Authors: Lee Poh-Seng , Garimella Suresh V.
Published: April 2008

Flow boiling in arrays of parallel silicon microchannels is investigated using a test piece with distributed heat sources and integrated local temperature sensors. The microchannels considered are 400 μm wide and 398 μm deep. Each test chip has a footprint of 1.27 cm by 1.27 cm with parallel microchannels diced onto the back side. Twenty-five microsensor arrays integrated into the microchannel heat sinks allow for accurate local temperature measurements over the entire chip. The experiments were conducted with deionized water which enters the channels in a subcooled state. Results are presented in terms of temperatures and pressure drops as a function of imposed heat flux. The experimental results aid in the assessment of the applicability of existing models and correlations in predicting the heat transfer rates in microchannels.
Effect of Shearing on the Crystallization Behavior of Poly (Butylene Terephthalate) and PBT Nanocomposites
Authors: Mago Gaurav , Fisher Frank T. , Kalyon Dilhan M.
Published: April 2008

Poly (butylene terephthalate) (PBT) is an engineering thermoplastic polyester with excellent mechanical properties and a fast crystallization rate widely processed via extrusion and injection molding. Such processes require very complex deformation histories, which can influence the ultimate properties of the processed material and parts. For such systems, flow-induced structural changes in the material as a function of processing are of increasing interest in the field of polymer processing. Linear viscoelastic material functions, including the storage and loss moduli and magnitude of complex viscosity, are very sensitive to the structural changes occurring in the polymer melt. This initial study focuses on the shear-induced crystallization of PBT and PBT nanocomposites with multi-walled carbon nanotubes (MWNTs). (Shear-induced crystallization is a subset of the more general flow-induced crystallization behavior which is the long-term goal of this research.) The effects of shear history on the isothermal crystallization behavior of these materials were investigated. Time sweep experiments at constant frequency, temperature and strain amplitude were carried out employing small-amplitude oscillatory shear within a parallel-plate geometry. Samples obtained upon quiescent crystallization suggested that the rate of crystallization and crystallization temperatures were modestly affected by the presence and concentration of the nanotubes, consistent with the findings of the earlier reports. However, the characterized shear-induced crystallization behavior of the nanocomposites presented here indicate more significant changes in the crystallization temperature and the rate of crystallization occur as a result of the incorporation of the carbon nanotubes. The shear-induced crystallization behavior was affected by the deformation rate, temperature, and the concentration of the carbon nanotubes. These findings indicate that shear-induced crystallization of polymer nanocomposites (and in general flowinduced crystallization effects due to arbitrary flow fields in the melt state during processing) should be an integral part of attempts to generate a comprehensive understanding of the development of the microstructural distributions and the coupled ultimate properties of polymer nanocomposites.
Applying Statics to Community Examples
Authors: Dues Joseph Francis
Published: April 2008

Most statics courses begin with a considerable amount of abstract discussion of forces and vectors. Since the mechanical engineering technology department's goal is to focus on practical, concrete instruction methods, the faculty has been working to expose students to more exercises that involve the practical application of statics to daily life. For the statics curriculum, a laboratory was developed that investigates the use of trusses in the surrounding community. Each truss is examined to determine its primary purpose, its type and any unique design features. Small groups discuss each example qualitatively (quantitative analysis of the forces in the truss is not performed) and then the whole class meets to compare the results. The trusses include the following: • Sherman Minton Bridge - Double arch truss. • K&I Railroad Bridge - Parker and Warren through trusses with a swing section and a cantilevered road deck parallel with the tracks. • Pedestrian Bridge - Pratt truss. • Pennsylvania Railroad Bridge - Combination of Parker through trusses over shipping lanes with Warren deck trusses. • Clark Memorial Bridge - Cantilever truss. Since each truss serves a similar transportation purpose, each truss is compared to the others to determine why its particular design was chosen. This paper describes each example and the effects the exercise had on student learning. This includes discussion of: increased interest by relating statics to daily experiences, experience with reverse engineering, practice identifying members in tension and compression, comparison of a standard truss with a cantilever truss bridge and recognition of changing design practices as technology changes over the years. Lastly is a description of the assessment, evaluation and planned improvements to the truss laboratory.