bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Scheme and an Error Analysis for a Class of Fractional Optimal Control Problems
Authors: Agrawal Om P.
Published: July 2010

There has been a growing interest in recent years in the area of Fractional Optimal Control (FOC). In this paper, we present a formulation for a class of FOC problems, in which a performance index is defined as an integral of a quadratic function of the state and the control variables, and a dynamic constraint is defined as a Fractional Differential Equation (FDE) linear in both the state and the control variables. The fractional derivative is defined in the Caputo sense. In this formulation, the FOC problem is reduced to a Fractional Variational Problem (FVP), and the necessary differential equations for the problems are obtained using the recently developed theories for FVPs. For the numerical solutions of the problems, a direct approach is taken in which the solutions are approximated using a truncated Fractional Power Series (FPS). An error analysis is also performed. It is demonstrated that the solution converges from above in the sense that the value of the approximate performance index is always higher than the optimum performance index. An expression for the error in the performance index is also given. The application of a FPS and an optimality criterion reduces the FOC to a set of linear algebraic equations which are solved using a linear solver. It is demonstrated numerically that the solution converges as the number of terms in the series increases, and the approximate solution approaches to the analytical solution as the order of the fractional derivative approaches to an integer order derivative. Numerical results are presented to demonstrate the performance of the Formulation.
Fractional Integrative Operator and Its FPGA Implementation
Authors: Caponetto R. , Dongola G. , Gallo A.
Published: July 2010

In this paper the fractional order integrative operator s−m, where m is a real positive number, is approximated via a mathematical formula and then an hardware implementation of fractional integral operator is proposed using Field Programmable Gate Array (FPGA). Digital hardware implementation of fractional-order integral operator requires careful consideration of issue of system performance, hardware cost, and hardware speed. FPGA-based implementation are up to one hundred times faster than implementations based on micro-processors; this extra speed can be exploited to allow higher performance in terms of digital approximations of fractional-order systems.
A Corotational Approach for 3D Absolute Nodal Coordinate Elements
Authors: Gerstmayr Johannes
Published: July 2010

The present paper deals with the modeling of three dimensional (3D), nonlinear beam finite elements which do not employ rotational parameters. The beam elements are based on the so-called absolute nodal coordinate formulation (ANCF), which has been introduced in the late 1990’s. Early implementations of 3D ANCF beam finite elements incorporated problems regarding Poisson, thickness and shear locking. In the present paper, two alternative models for the work of elastic forces are presented. The first approach, which is intended to provide reference solutions, is close to the original approach. However, the effect of Poisson and thickness locking is eliminated by proper integration of the contributing terms in the virtual work of elastic forces. In the second approach, a corotationally linearized model is developed, which is based on a simple formulation for the elastic forces. The latter model only takes into account small deformations with respect to a corotating reference frame, but it is different from the conventional floating frame of reference formulation, because it has a constant mass matrix. The second approach is intended to be advantageous in practical applications where only small deformations with respect to large rigid body motions need to be taken into account, such as in robotics or machine dynamics. Numerical results are presented, which show that the new approaches agree with the solution of static and dynamic problems using classical finite elements or analytical methods.
Purely Analog Fractional Order PI Control Using Discrete Fractional Capacitors (Fractors): Synthesis and Experiments
Authors: Mukhopadhyay Shayok , Coopmans Calvin , Chen YangQuan
Published: July 2010

This paper presents the results of experiments related to analog fractional order PI control of a coupled tank system. A custom circuit board has been built to perform analog PID/FOPID control. Specialized circuit elements called ‘Fractors’ [1] are used to perform fractional order integration/differentiation of the error signals. The design of the board, subsequent experimentation and its comparison to similar digital control techniques have been presented. The benefits of purely analog control when dealing with non-linearities are also discussed. Further, methods of approximating a particular fractional order α* with any number of practically available orders α1, α2, ....αn has also been presented. The conclusion of this work examines the need for purely analog control as opposed to widespread digital methods and also lays down definite directions for future work.
Modeling Sustainability of Complex Systems: A Multi-Scale Framework Using SysML
Authors: Azevedo Kyle , Bras Bert , Doshi Siddharth , Guldberg Tina
Published: July 2010

In this paper, we propose a framework to design and analyze sustainability within complex multi-scale systems. Systems that have large variability in temporal and spatial resolution are common in lifecycle analyses and sustainability studies. Unlike traditional problems in systems engineering, these systems are composed of numerous interacting layers, each intricate enough to be a complete system on its own. In addition, the goal of achieving an economically and environmentally sustainable system introduces new elements to the problem domain. To manage this complexity, the suggested methodology focuses on integrating existing modeling constructs in a transparent manner, and capturing structural and functional relationships for efficient model reuse. The Systems Modeling Language (OMG SysML™) is used to formally implement the modeling framework. To demonstrate the method, we apply it to a large scale multi-modal transportation network. Analysis of key network parameters such as emissions output, well-to-wheel energy use, and system capacity are presented in a case study of the Atlanta, Georgia metropolitan area.
Integrated Cut Performance and Sample Inspection System for Microtome Setup Evaluation
Authors: Brisach Daniel , Alms Justin , Glancey James , Cloud Nate
Published: July 2010

Currently, blade manufacturers employ in-house histology testing to evaluate the performance of their blades. The following performance metrics are evaluated for a group of production blades: sample compression, cut-feel, and number of knife lines left on samples. In the research presented herein, an evaluation of the relationships between high quality samples and microtome knife configuration variables is explored through quantifying the cutting force and inspecting samples for knife induced defects. Several types of measurements correlating to the cutting force were made. Sound, vibration, and cutting force were tested for their adequacy in distinguishing different knife configurations. The most robust measurement was then focused on to derive relationships between blade types and microtome setup. An automated imaging system was explored for measurement of sample quality. The imaging system can improve the reliability and productivity of the measurement of knife quality metrics, for product-process quality control. The imaging system achieves this by detecting knife lines and performing simple measurements to quantify the degree of compression of the samples. This study aims to advance the science of histology and give insight to blade manufacturers through interfacing a microtome with a PC based user interface.
Vibration Isolation via Linear and Nonlinear Periodic Devices
Authors: Spadoni A. , Daraio C.
Published: July 2010

The current manuscripts deals with the design of passive mechanical filters for vibration attenuation a low frequencies. Traditionally, this has been addressed employing dissipation as the attenuation mechanism. While such strategy provides broad-frequency effectiveness, attenuation at any given frequency is modest. Mass and stiffness-modulated periodic systems, on the other hand, exploit dispersion as the attenuation mechanism and represent an alternative to dissipation-based devices. Attenuation due to dispersion may be significantly higher than what is afforded by dissipation-based systems within a design frequency rage. The proposed assemblies, however, are not easily tailored to filter lowe-frequency vibrations. To this end, embedding such periodic systems into an elastic matrix yields a high-pass mechanical filter with tunable stop bands were waves are not allowed to propagate. Significant improvements in performance moreover may be obtained if intrinsically nonlinear devices are adopted. Specifically, a strongly nonlinear medium such as ordered granular media supports a limited number of waveforms, resulting in an efficient mechanical filter. Results reported here, in fact, suggest matrix-embedded sphere chains as highly tunable mechanical filters for vibration attenuation.
Optimal Energy Harvesting From Low-Frequency Bistate Force Loadings
Authors: Scruggs Jeff T. , Behrens Sam
Published: July 2010

This paper considers techniques for harvesting energy from vibratory loadings that can be characterized by low-frequency alternations between a minimum and maximum force magnitude. In such cases, it is often impossible to tune the harvester to resonate in the frequency band of the excitation, due to constraints on the mass and transducer displacement. Here, we consider the case in which the harvester’s transient dynamics are characterized by a natural period which is orders of magnitude below the fundamental period of the disturbance, and which undergoes significant decay in between load alternations. In this case, the damped vibration of the harvester induced by each load alternation may be viewed as an isolated transient response. For such problems, we consider the optimization of generated power, through the use of an active power-electronic drive to explicitly regulate transducer current according to an optimized feedback law. The analysis accounts for both mechanical and electrical losses in the harvester, as well as dissipation in the electronics. It also accounts for the static power necessary to operate the control intelligence and gate the drive transistors. We show that the optimal feedback law is in general a time-varying linear controller. Further, we show that following the leading edge of each load alternation, there is an optimal time horizon over which to operate the electronic conversion system, beyond which the energy expended on static power exceeds the remaining energy recoverable from the dynamic response of the harvester. The analytical derivation of the controller is done generally, and is shown to simplify to easily-computable closed-form solutions in a number of simple cases. Analytical and simulation results are related to an experimental energy harvesting system involving a single degree-of-freedom electromagnetic transducer.
An Investigation of the Damping Effects of Various Gas Environments on a Vibratory MEMS Device
Authors: Kim Seong Jin , Dean Robert , Jackson Robert , Flowers George
Published: July 2010

An experimental investigation of the damping effects in several different gas chemistries on a vibrating micromachined structure was conducted. A corresponding numerical study using an analytical model was also performed and the results correlated with the experimental observations. Both the experimental setup/procedure and the analytical model are described in detail. A summary of the results is presented and conclusions/observations discussed.
The Error Incurred in Using the Caputo-Derivative Laplace-Transform
Authors: Hartley Tom T. , Lorenzo Carl F.
Published: July 2010

This paper considers the initialization of fractional-order differential equations. The initialization responses obtained using the Caputo derivative are compared with the exact initialization responses from the Riemann-Liouville definition of the fractional derivative. The error incurred in using the Caputo derivative for initialization problems in fractionalorder differential equations is presented.
Recursive Algorithms Using Local Constraint Embedding for Multibody System Dynamics
Authors: Jain Abhinandan
Published: July 2010

This paper describes a constraint embedding approach for handling of local closure constraints in multibody system dynamics. The approach uses spatial operator techniques to eliminate local-loop constraints from a system to effectively convert it into a tree-topology system. This conversion to a tree-topology allows the direct application of the host of available techniques including mass matrix factorization and inversion to be applied to the system dynamics. One application is the extension of the well-known recursive O(N) forward dynamics for solving the system dynamics of these systems. The algorithms are especially applicable to systems where the constraints are confined to small-subgraphs within the system topology. The paper provides background on the spatial operator approach, the extensions for handling embedded constraints, and concludes with examples of such constraints.
Real-Time Face Tracking System for Augmented Reality
Authors: Tu Yi-Ting , Smith Shana
Published: July 2010

In this paper, we apply augmented reality technology to make human computer interface more technically advanced and interesting. We present a real-time face tracking system for augmented reality, which will be used in electronic commerce, to help shoppers acquire a more direct interaction with the products they purchase. A real-time face tracking mechanism can enhance the realism of online shopping. In order to emphasize the convenience and practicability of our system, we used plug-in functions and Principal Component Analysis (PCA) to conduct real-time face tracking and Neural Networks (NN) to reduce training time and achieve valid recognition. Convenience and uniqueness are the other main parts of this system.
Adaptive Angular-Velocity Vold-Kalman Order Tracking Used in Characterizing Dynamic Signals Measured From Rotary Machines
Authors: Pan Min-Chun , Chu Wei-Chen
Published: July 2010

In this paper we propose and implement an order tracking (OT) technique evaluating in an adaptive manner for signal interpretation and diagnosis of rotary machinery during operation. The paper comprises theoretical derivation, numerical implementation and experimental justification. Comparisons of the adaptive Vold-Kalman filtering OT (VKFOT) scheme to its conventional form are made through synthetic signal processing. Parameters such as the weighting factor, Q1 parameter, sampling frequency and process noise, which influence tracking performance, are investigated. Moreover, this adaptive OT scheme can be computed on-line and implemented as a real-time processing application.
Perceptions of Innovation in Product Form and Function: A Comparison of Historical and Future Oriented Data Mining
Authors: Kim Taehyun , Okudan Gu¨l E.
Published: July 2010

When product functions and qualities are similar across products, customers make their purchasing decision upon aesthetic form. Form presents a significant competitive factor that improves the value of a product. Overall, the purpose of this study is to examine the most important product design factors that affect the market share trends in products. As a case study we center our analyses on mobile phones. Study uses product characteristics for 1,028 mobile phones released between 2003 and 2008 as a case study. Multiple linear regression analysis is used to mine the date to find highly correlated variables that influence the market share, and Mallow’s Cp method is used to determine the best-fitting model. The Partial Regression Coefficients are used to evaluate the relative importance of design criteria. The nine mobile phone design features that affect the market share were identified, and the block form style is determined as the most important design factor. Then, the results of our historical data mining are compared to a future oriented approach (survey analysis using Nominal Logistic Regression). We discuss the advantages and disadvantages of these approaches, and provide inferences about how investments should be directed in future mobile phone designs.
FEAsy: A Sketch-Based Interface Integrating Structural Analysis in Early Design
Authors: Murugappan Sundar , Ramani Karthik
Published: July 2010

The potential advantages of freehand sketches have been widely recognized and exploited in many fields especially in engineering design and analysis. This is mainly because the freehand sketches are an efficient and natural way for users to visually communicate ideas. However, due to a lack of fundamental techniques for understanding them, sketch-based interfaces have not yet evolved as the preferred computing platform over traditional menu-based tools. In this paper, we address the specific challenge of transforming informal and ambiguous freehand inputs to more formalized and structured representations. We present a domain-independent, multi-stroke, multi-primitive beautification method which detects and uses the spatial relationships implied in the sketches. Spatial relationships are represented as geometric constraints and satisfied by a geometric constraint solver. To demonstrate the utility of this technique and also to build a natural working environment for structural analysis in early design, we have developed FEAsy (acronym for Finite Element Analysis made easy) as shown in Fig. 1. This tool allows the users to transform, simulate and analyze their finite element models quickly and easily through freehand sketching, just as they would draw on paper. Further, we have also developed simple, domain specific rules-based algorithms for recognizing the commonly used symbols and for understanding the different contexts in finite element modeling. Finally, we illustrate the proposed approach with a few examples.
An Ontology Mapping Application Using a Shared Ontology Approach and a Bridge Ontology
Authors: Kim OkJoon , Jayaram Uma , Jayaram Sankar , Zhu Lijuan
Published: July 2010

This paper presents our continuing work to develop methods to exchange product knowledge in the semantic level in the CAD/CAE domains. We present an approach based on a shared ontology, in which a higher level of ontologies are shared among lower levels of ontologies. Key mapping strategies, such as Equivalency, Attribute Similarity, Composition Similarity, and Inheritance Similarity are defined to map concepts and properties defined in a product design domain and an assembly simulation domain. In addition, a Bridge Ontology is designed to store information obtained from mapping processes and construct a link between different knowledge repositories. An Ontology Mapping Application (OMA) which brings together all these elements has been designed and implemented. It is a Java-based application that allows the user to load source and target ontologies, calculate concept and property similarities between them, display the mapping results, and output a corresponding Bridge Ontology.
Fractional Order Universal Adaptive Stabilizer for Fractional Order Systems
Authors: Li Yan , Chen YangQuan
Published: July 2010

In this paper, the fractional order universal adaptive stabilization of fractional order SISO system is discussed. The fractional universal adaptive stabilizer is u(t) = −k(t)sgn{CB}y(t), where 0Dtβk(t) = ‖y(t)‖p, which guarantees the asymptotic stability of the equilibrium point of fractional order state space system with finite control effort. Moreover, the fractional order system with order α ∈ (0, 1/(1+p)) can be stabilized by the fractional controller but not for the integer order controller. Simulation results are provided as the proof of concepts.
Fuzzy Control of a Pneumatic Muscle Driven Parallel Robot for Ankle Rehabilitation
Authors: Jamwal Prashant K. , Xie Shane , Farrant Jack
Published: July 2010

A new wearable parallel robot has been designed and constructed for ankle joint rehabilitation treatments. The robot employs four pneumatic muscle actuators (PMA) together with cables to achieve three rotational degrees of freedom (dof) of its end platform. Parallel topology of the robot, unpredictable environment along with the time varying and non-linear behavior of actuators impose modeling and control challenges which are difficult to comprehend. In this paper an optimal fuzzy dynamic model of the pneumatic muscle has been developed to accurately predict the muscle behavior. The model is capable of mapping the complex relationship in length, force and pressure of the PMA with higher accuracy. This model has been further used to develop a fuzzy control scheme for the ankle robot. Experimental results are obtained to study and model the simultaneous actuation of all the actuators. Comparison with the previous dynamic modeling and control schemes demonstrates an improved performance of the proposed fuzzy controller.
Middleware Design for Energy Harvester of Wireless Sensor Nodes
Authors: Zhu Zhenhuan , Oyadiji S. Olutunde , Mekid Samir
Published: July 2010

The energy harvesting for wireless sensor nodes is one of the effective methods to extend the lifespan of wireless sensor networks. The paper firstly analyzes the power requirement of a sensor node, and surveys the energy output for typical energy transducers working indoor. In general, energy harvested from the indoor environment is not matched with the power requirement of wireless sensor nodes. The harvested energy indoor is generally less than the required energy. Therefore, we propose a solution to design a middleware for the dynamic power management of a wireless sensor node. The implementation and performance evaluation of the middleware are investigated. It is shown that the proposed middleware is an effective way of solving the challenge problem above.
Finite Element Modeling of Structures With L-Shaped Beams and Bolted Joints: Model Updating and Predictive Modeling Approaches
Authors: He K. , Zhu W. D.
Published: July 2010

Due to bending-torsion coupled vibrations of the L-shaped beams and numerous uncertainties associated with the bolted joints, modeling structures with L-shaped beams and bolted joints is a challenging task. With the recent development of the modeling techniques for L-shaped beams by the authors [1], this work focuses on developing new finite element (FE) models for bolted joints in these structures. While the complicated behavior of a single bolted connection can be analyzed using commercial FE software, it is computationally expensive and inefficient to directly simulate the global dynamic response of an assembled structure with bolted joints, and it is necessary to develop relatively simple and accurate models for bolted joints. Three new approaches, two model updating approaches and a predictive modeling approach, are developed in this work to capture the stiffness and mass effects of bolted joints on the global dynamic response of assembled structures. The unknown parameters of the models in the model updating approaches are determined by comparing the calculated and measured natural frequencies. In the predictive modeling approach, the effective area of a bolted connection is determined using contact FE models and an analytical beam model; its associated stiffnesses can also be determined. The models developed for the bolted joints have relatively small sizes and can be easily embedded into a FE model of an assembled structure. For the structures studied, including a three-bay space frame structure with L-shaped beams and bolted joints, and some of its components, the errors between the calculated and measured natural frequencies are within 2% for at least the first 13 elastic modes, and the associated modal assurance criterion values are all over 94%.
Natural Frequencies of Composite Cylindrical Helical Springs Manufactured Using Filament Winding
Authors: Sancaktar Erol , Gowrishankar Sunil
Published: July 2010

We devised a novel technique to fabricate composite cylindrical helical springs using glass, and carbon fibers and in hybrid form, embedded in a matrix of epoxy resin, thus introducing a novel approach to spring making by incorporating the versatility of the filament winder. Our method allows us to vary the dimensions of the spring with considerable ease. This is accomplished in three stages. The first stage involves the proper selection of the resin and hardener. In the next stage, the glass and carbon fibers are completely soaked in a resin bath and encased in PVC tubing of three different inner diameters, which determine the wire diameter of the composite spring. Using a filament winding technique, these fiber filled tubes are wound on PVC mandrels of three different diameters. The natural frequencies of the manufactured composite springs were measured experimentally to study the influence of dimensional parameters, i.e., diameter ratios (D/d) and number of active turns (N = 6 and 7) on the free vibration frequencies. The natural frequencies for glass and carbon fiber and hybrid springs were measured using an MTS fatigue tester, and the resonance of the springs were captured using a digital camera.
Analysis and Troubleshooting of Steam Induced Instability for an Industrial Turbomachinery
Authors: Lu Song-yuan , Wu Zheng-feng , Zhao Xu
Published: July 2010

This paper presents the whole process of vibration analysis and troubleshooting of a new commissioning T6530 unit, a steam extraction and backpressure turbomachinery, which exhibited steam-excited instability during load-up. Through vibration measurement, fault diagnosis, site fault handling and stability numerical analysis of bearing and shaft train, the unit was redesigned and manufactured to resolve vibration faults finally.
Vibration Characteristics, Analysis and Diagnosis for Rub Between Rotor and Stator of Turbomachine in the Field
Authors: Lu Song-yuan , Zhao Xu , Wu Zheng-feng
Published: July 2010

This paper presents the rub mechanism, causation, vibration characteristics and diagnosis methods based on data records of some cases of the rub fault when units started up and operated with working speed, which happened at large units. These contents can be the reference for analysis and identify for rub in the field.
Induction Motor Multi-Fault Analysis Based on Intrinsic Mode Functions in Hilbert-Huang Transform
Authors: Xue Xin , Sundararajan V.
Published: July 2010

This paper reports experimental studies to detect two faults in a 3-phase 1.5hp induction motor using intrinsic mode functions from Hilbert-Huang transform. The faults studied are the eccentricity of the air-gap between the rotor and stator and damage to the outer race of bearings. The experiments are conducted under four conditions: the normal no-fault condition, two single fault conditions and the multiple faults condition. Two microphones, one vibration sensor and one current sensor are used to collect sound, vibration and current data respectively. The data is analyzed using the Hilbert-Huang transform and Fast Fourier Transform. Features are extracted from the spectrum of intrinsic mode functions and the average value of their envelope. Three simple classifiers are used to classify these four experimental conditions. The results demonstrate that the multiple sensors do improve the classification rate and that the Intrinsic Mode Functions obtained by the Hilbert-Huang transform are more effective than FFT in classifying multiple faults.
One-Shot Balancing of Rigid Rotors: A Closed Form Solution
Authors: Gutie´rrez-Wing Enrique S. , Aguirre-Romano Jorge E.
Published: July 2010

This article presents a closed-form solution to the computation of unbalance correction masses for rigid rotors mounted on flexible bearings. The solution requires measurements of the response of the rotor-bearing system to the unbalance that is to be corrected, as well as knowledge of its total mass or other stiffness or damping parameters that are readily deducible from the mounting configuration. No detailed mathematical models or information from previous balancing runs are required. The computation is based on the relationships that exist between some spatial and modal parameters of rotor-bearing systems. Such relationships are derived in this article, and their use in the computation of balancing masses is presented and verified with results from an experimental test rig. This work demonstrates the feasibility of balancing rigid rotors without trial runs, detailed models or historical balancing records.
A New Deterministic Approach in Probabilistic Design Optimization
Authors: Golbayani Hami , Kazerounian Kazem
Published: July 2010

In this paper, a simple and powerful formulation is presented for probabilistic design of engineering systems. The challenging task of optimum allocation of errors to design variables is transformed into a simple zero degree of difficulty geometric programming problem. This method is based on a known state of the design (the design values as well as the linear mapping between the input and output of the system). Uncertainties of design variables are assumed to be independent, and normally distributed. Failure is defined as a constraint in the optimization process, and has the form of the probability of divergence of outputs from their allowable bounds. Then, this constraint is simplified into a deterministic bound within six sigma spread. Having a zero DOD problem, the optimal solutions are readily available for any system regardless of the complexity. Several numerical experiments are conducted to assess the efficiency of the proposed formulation. The results are compared with more exhaustive searches using Monte Carlo simulation. For higher order and complex systems, it is demonstrated that this formulation will be %20 more conservative than the exact Monte Carlo simulation.
Modeling the Impact Response of HDPE Fuel Tank Material
Authors: Xiao Xinran , Virupaksha Vinayshankar
Published: July 2010

As a part of the effort on modeling method development for crashworthiness prediction of vehicle structures, this paper examines the impact response of a multilayer high density polyethylene (HDPE) fuel tank material. The deformation behavior of HDPE under lateral impact was investigated by flexural experiment using three-point bending, and by driven dart impact with different velocities at ambient and −40°C. The large deformation and fracture behaviors of multilayer HDPE under impact loading at different rates and temperatures were simulated using LS-DYNA®.
Dynamic Pull-In Instability of Initially Curved Microbeams
Authors: Moghimi Zand M. , Ahmadian M. T. , Rashidian B.
Published: July 2010

In this study, dynamic pull-in instability and snap-through buckling of initially curved microbeams are investigated. The microbeams are actuated by suddenly applied electrostatic force. A finite element model is developed to discretize the governing equations and Newmark time discretization is employed to solve the discretized equations. The static pull-in behavior is investigated to validate the model. The results of the finite element model are compared with finite difference solutions and their convergence is examined. In addition, the influence of different parameters on dynamic pull-in instability and snap-through buckling is explored.
Viscoelastic Temperature Dependent Characterization Protocols Without the Use of Poisson’s Ratios
Authors: Shtark Abraham , Grossbein Hagay , Hilton Harry H.
Published: July 2010

The previously formulated analytical and experimental protocols for a single temperature conditions in [1] are extended to multi temperatures in order to develop shift factors and master relaxation curves. The system consist of unidirectional tensile creep or relaxation experiments performed on viscoelastic specimen. A combination of a photogrametric device and a tensile testing machine provides stress data in the loaded direction and strains in both longitudinal and transverse directions. The data is integrated through the use of the integral constitutive relations, and produce values for the creep compliance parameters. Subsequently, the viscoelastic Young’s, shear and bulk moduli are determined without the use of viscoelastic Poisson’s ratios (PR). Experimental results indicate strong time, temperature, stress and stress history dependencies of viscoelastic PRs.
Numerical Characterization of the Background Noise Generated by the ARL/Penn State Garfield Thomas Water Tunnel Impeller
Authors: Jonson Michael L. , Shepherd Micah R. , Myer Eric C. , Hambric Stephen A. , DeRoche Rachael J.
Published: July 2010

The Pennsylvania State University Applied Research Laboratory has a 1.22 meter (48 inches) diameter closed loop water tunnel. The flow is driven by an axial pump with three blade rows and powered by a 1.5 MW motor. The four blades of the impeller have the highest relative velocities of any lifting surface in the facility, and generate input acoustic power which acts as a background noise floor in tunnel measurements of turbomachinery and vehicle body performance. In this paper, we investigate the sound power radiated by the impeller and its propagation through the water tunnel. Trailing edge hydrodynamic forcing functions are computed for the impeller based on local relative velocities and turbulence properties. For lower frequencies, these forces are then applied to an experimentally validated structural finite element model (FEM) of the impeller. The input power to the water tunnel is determined using an acoustic boundary element model (BEM) of the impeller. A statistical energy (SEA) model of the water tunnel allows for an estimate of the rms pressure within the water tunnel test section to provide guidance on lowering background noise.
The Infrasound Network (ISNet) as an 88D Adjunct Tornado Detection Tool: The Status of Infrasonic Tornado Detection
Authors: Bedard Alfred J.
Published: July 2010

After a background of operation through three years (2003–2005), the purpose of this paper is to summarize the status of our efforts to evaluate the potential of NOAA’s Infrasonic Detection Network (ISNet) for tornado detection and warning. The network implementation has involved parallel efforts at hardware design, detection algorithm development, designing displays, application of a fully compressible numerical model to understand infrasound generation processes, and modeling propagation using a 3-D acoustic ray tracing program. In combination, these efforts are placing us in a position to realistically assess the potential of infrasound to help with tornado detection and warning. One of our initial expectations, (that a 3-station network separated by about 200Km would robustly triangulate on acoustic tornadic sources) was shattered. Only at longer ranges (typically > 200Km because of an upper atmospheric wave guide) did the 3 stations (at Boulder, CO, Pueblo, CO, and Goodland, KS) monitor the same source with clear detections. On the other hand, individual stations showed regional tornado detection skill with different stations at times simultaneously detecting different regional tornadoes. Ray trace simulations have explained these regional detection differences, indicating that there is a need for closer network station spacing. Examples of both good and failed detections of tornadic storms are presented and recommendations are made for optimum network spacing. The needs for further evaluation are reviewed; including implementation of a denser network, improved verification (network stations can contribute guidance to field programs), improved display options, and timeliness. An intriguing aspect of our observations is that storms often produce infrasound about 30 minutes prior to a first tornado report. Numerical simulations completed and in progress should help illuminate the infrasonic source processes. Figure 1 below indicates the important elements involved with infrasonic tornado detection.
Comparison of Contour Based and Feature Based Tracking Methods for Control of Microbiorobots
Authors: Kim Dal Hyung , Steager Edward , Kim Min Jun
Published: July 2010

Miniature robots should be precisely controlled because of a small workspace and size of their shapes. Small error of control could lead to failure of tasks such as an assembly. Tracking is one of the most important techniques because control of a small scale robot is hard to accomplish without object’s motion information. In this paper, we compare the feature based and the region based tracking methods with microbiorobot. Invariant features can be extracted using Scale Invariant Feature Transfrom (SIFT) algorithm because microbiorobot is a rigid body unlike a cell. We clearly showed that the feature based tracking method track exact positions of the objects than region based tracking method when objects are close contacted or overlapped. Also, the feature based tracking method allows tracking of objects even though partial object disappears or illumination is changed.
High Precision Method for Sequential Micro-Contact Printing of Multiple Aligned Patterns
Authors: Xu Li , Trinkle Christine A.
Published: July 2010

High quality surface patterns of macromolecules are a key component of many microfluidic and microstructured devices. The technique of microcontact printing uses an elastomeric stamp to selectively transfer molecules to a pretreated substrate, and it has emerged as one of the most ubiquitous and versatile ways of creating micropattnered surfaces. This technique is especially well suited for transferring a single chemical pattern, but many chemically and biologically relevant surfaces require multiple complementary molecular patterns. The research demonstrated here utilizes a high-precision passive alignment system to generate these patterns using sequential microcontact printing steps. The technique relies on mechanical alignment and does not require optical alignment of each stamp; the resulting data shows a placement variation of less than 5 μm.
Measuring the In-Situ Matrix Properties in Fiber Reinforced Composites
Authors: Heinrich Christian , Waas Anthony M.
Published: July 2010

A new methodology to extract viscoelactic-plastic material properties of a matrix material in a composite through Nanoindentation is discussed in this study. A material model is developed to account for viscoelastic-plastic effects and is incorporated in a parametric Finite Element (FE) analysis. The results from this analysis are used to construct a surrogate model to allow for fast evaluations of the simulated experiments, which in turn can be used to match calculations with real experiments. The surrogate model predicts the FE results within an average error of 2.9%. The viscoelastic properties are recovered with an error of 9.4% and 9.8% respectively, when comparing the surrogate model with FE simulations.
Stochastic Response Surface Method Based on Weighted Regression and Its Application to Fatigue Reliability Analysis of Crankshaft
Authors: Sun Yi Fei , Qiu Hao Bo , Gao Liang , Lin Ke , Chu Xue Zheng
Published: July 2010

Response surface method (RSM) is widely used in structural reliability analysis with implicit performance function (PF) which requires formidable computational effort. The ill conditioned coefficient matrix of normal equation in classical RSM prevents it from being used in high order conditions. The stochastic response surface method (SRSM), deriving from classical RSM, offers one alternative to solve this problem. Yet the regression method of conventional SRSM is based on normal least square method which ignores the different significance of each sample point through which the response surface function (RSF) is formed. To yield RSF close to the limit state which leads to better estimation of probability of failure, this paper introduces the weighted regression into SRSM and several examples with hypothetic explicit PF are given to test the performance of SRSM. In addition, we use this method in the fatigue reliability analysis of crankshaft with implicit PF. All these examples demonstrate the advantages of the proposed method.
Stability of Flows in a T-Junction Microfluidic Device
Authors: Gupta Amit , Kumar Ranganathan
Published: July 2010

In recent years, microfluidic devices that generate micron sized droplets/bubbles have found widespread applications in drug delivery, microanalysis, tumor destruction, as ultrasound agents and in chemical reactions at the micron level. In the current work, simulations results are being presented for a T-junction device for the formation of micron-sized droplets using the lattice Boltzmann method. Flow regimes obtained as a consequence of two immiscible fluids interacting at a T-junction are presented for a range of Capillary numbers and different flow rates of the continuous and dispersed phases. Through lattice Boltzmann based simulations, regime maps are presented that distinguish parallel flows from droplet flows. It is shown that as the Capillary number increases, the transition zone which separates parallel and droplet flows shrinks, and is influenced by the viscosity ratio as well.
Characterization and FEA Based Optimization of Elastomeric Components for Automotive Applications
Authors: Rizvi Reza R. , Czekanski Alex , Naguib Hani E.
Published: July 2010

This study aims to show the implementation of an optimization procedure by characterizing the material’s hyperelastic behavior in harsh environments experienced in facility testing and in real world automotive conditions. The procedure consists of conducting material tests under various simulated harsh environments, determining the co-efficients for hyperelastic material modeling and using FEA to predict and correlate the nature of failure observed in facility testing. Two commercially available and commonly employed thermoplastic elastomers (TPE), Santoprene (Ethylene-Propylene-Diene-Monomer rubber and Polypropylene blend) and Desmopan (Thermoplastic Polyurethane), were tested. The harsh environments simulated are fluid immersion tests in automobile grease. Material aging characteristics in controlled thermal conditions were also documented. Compression and tension tests were conducted in order to determine the co-oefficients of the Mooney Rivlin hyperelastic material model. Finite Element Analysis (FEA) simulations were conducted on LS-DYNA software, to determine the quasi-static stress distributions on an overslam bumper part, a typical application of automotive elastomers. Shape and topological variations were investigated in the FEA tests. It was found that certain shape and topological changes to the part result in minimizing the stress concentrations. It is hypothesized that such changes to the rubber component would result in a lower failure rate in facility testing.
In-Situ Active Noise Cancellation Applied to Magnetic Resonance Imaging
Authors: Rudd Brent W. , Lim Teik C. , Li Mingfeng , Lee Jing-Huei
Published: July 2010

Magnetic Resonance Imaging (MRI) is a powerful medical diagnostic tool. Unfortunately, the loud noise produced during scanning is unpleasant and potentially harmful to patients and may limit imaging protocol. A variety of approaches have been proposed to reduce noise exposure. Prior studies have been conducted in a sound quality chamber to aid in the development and implementation of hardware, algorithms, and procedures, which resulted in an active noise cancellation system tailored to conditions present during MRI. The active noise control system generates a secondary sound signal fed into a set of headphones worn by the patient. This system performs well during physical simulation of scanning conditions. In this study, the headphones are worn by a dummy during in-situ MRI scanning. Our specific effort is to take a selected successful experiment under simulated conditions and repeat it during live scanning to evaluate the real time performance of the system conducted in-situ. Evaluation of a common scanning sequence was conducted and the procedure adjusted to maximize the performance of the system. The sound pressure levels (SPLs) at the patient’s ear were measured with and without active control operational, and the results are compared to evaluate the active noise cancellation system’s performance during live scans.
Acoustic Band-Gap Formulation in Infinite Periodic Porous Media With a Multi-Layered Unit Cell: Multi-Scale Asymptotic Method
Authors: Lee Chang-Yong , Leamy Michael J. , Nadler Jason H.
Published: July 2010

This article introduces a numerical formulation for studying frequency band structure in multi-periodic acoustic composite structures. Herein, multi-periodic acoustic composite structures are defined as periodically-layered acoustic media wherein each layer is composed of periodically-repeated unit fluid cells, especially those arising from the study of rigid-frame porous materials. Hence, at least two periodic scales (microscopic and mesoscopic, respectively) comprise the macroscopic acoustic media. Under the Floquet-Bloch’s condition, exploitation of the multi-periodicity allows for efficient generation of dispersion curves via a multi-scale asymptotic method (for homogenizing the mesoscale) coupled to original acoustic transfer matrix methods (for the macroscale). The combined numerical formulation results in a general analysis procedure for evaluating complex dispersion relationships. The dispersion curves can be used to reveal frequency stop bands wherein the wave vector is highly imaginary—i.e., plane waves experience rapid attenuation. The formulation is applied to four infinite, multi-periodic acoustic composite structures in order to demonstrate the formulation’s utility and to reveal novel properties, particularly those which can be influenced by design of the mesoscopic unit cell.
Study of Synergistic Fire Retardancy of Nanoparticles in Polymer Matrix Composites
Authors: Zhuge Jinfeng , Tang Yong , Gou Jihua , Chen Ruey-Hung , Ibeh Christopher
Published: July 2010

In this study, three kinds of carbon nanofiber sheets were made through a high-pressure filtration system: pure carbon nanofiber, carbon nanofiber with polyhedral oligomeric silsequioxane (PCNS) and carbon nanofiber with Cloisite Na+ clay (CCNS). Then these sheets were incorporated onto the surface of glass fiber reinforced polyester composites through resin transfer molding process. The samples were analyzed with scanning electron microscopy (SEM), thermal gravimetric analyses (TGA). The fire retardant performance of the laminates was evaluated with cone calorimeter test at an external radiated heat flux of 50kw/m2. The results of laminates with PCNS indicated that the fire performance was impaired when comparing with the case of pure carbon nanofiber paper. However, in the case of CCNS, the primary results showed a pronounced improvement of the fire performance was observed. The possible mechanism was also discussed in the present study.