bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Vibration Analysis and Design of an Adhesively Bonded Composite Single Lap Joint
Authors: Apalak M. Kemal , Ekici Recep , Yildirim Mustafa
Published: May 2009

In this study the three dimensional vibration analysis of an adhesively bonded cantilevered composite single lap joint was carried out. The first four bending natural frequencies and mode shapes were considered. The back-propagation Artificial Neural Network (ANN) method was used to determine the effects of the fiber angle, fiber volume fraction, overlap length and plate thickness on the bending natural frequencies and the mode shapes of the adhesive joint. The bending natural frequencies and modal strain energies of the composite adhesive lap joint were calculated using the finite element method for random values of the fiber angle, the fiber volume fraction, the overlap length and the plate thickness. Later, the proposed neural network models were trained and tested with the training and testing data. The fiber angle was more dominant parameter than the fiber volume fraction on the natural bending frequencies and corresponding bending mode shapes, and the plate thickness and the overlap length were also important geometrical design parameters whereas the adhesive thickness had a minor effect. In addition, the present ANN models were combined with Genetic Algorithm to search a joint design satisfying maximum natural frequency and minimum modal strain energy conditions for each natural bending frequency and mode shape.
Frost Growth CFD Model of an Integrated Active Desiccant Rooftop Unit
Authors: Geoghegan Patrick , Petrov Andrei , Vineyard Edward , Linkous Randall , Zaltash Abdolreza
Published: May 2009

A frost growth model is incorporated into a Computational Fluid Dynamics (CFD) simulation of a heat pump by means of a user-defined function in a commercial CFD code. The transient model is applied to the outdoor section of an Integrated Active Desiccant Rooftop (IADR) unit in heating mode. IADR is a hybrid vapor compression and active desiccant unit capable of handling 100% outdoor air (dedicated outdoor air system) or as a total conditioning system, handling both outdoor air and space cooling or heating loads. The predicted increase in flow resistance and loss in heat transfer capacity due to frost build-up are compared to experimental pressure drop readings and thermal imaging. The purpose of this work is to develop a CFD model that is capable of predicting frost growth, a potentially valuable tool in evaluating the effectiveness of defrost-on-demand cycles.
Using a 2D Laser Range Finder for Environment Monitoring by an Autonomous Mobile Robot
Authors: Marotta Claudio , Milella Annalisa , Cicirelli Grazia , Distante Arcangelo
Published: May 2009

In this paper, a novel approach to automated inspection is presented, which uses a mobile robot equipped with a 2D laser rangefinder. The main idea underlying the proposed method is that of comparing current laser readings with local range data of the environment stored in a database, to look for new or removed objects. First, the robot is guided to reach goals, fixed in critical areas where inspection is required. Range data of the region surrounding each goal are automatically acquired and stored in a database. Afterwards, the robot can begin its surveillance task. Each time it reaches a goal, comparison between the current readings and the stored local data is performed using an Iterative Closest Point (ICP)-based scan-matching algorithm. Then, a fuzzy logic inference system establishes whether a significant variation of the scene has occurred and an alarm signal must be produced. Experimental results show that the proposed approach is reliable in detecting either new or missing objects and can be effectively used in automated surveillance systems in dynamic environments.
Design/Development of a Stable U-10 Soccer Goal
Authors: Ferrone Christopher W.
Published: May 2009

All across the United States, all year round, children play with soccer goals. The average age of children who interact with goals ranges from 5 to 18 years of age; although many adults utilize soccer goals as well. In most instances the goal is located at a public park or school. This requires the goals to be moveable. The portability of the goal is to allow for storage, grounds keeping and game placement — to name a few. This requirement dictates that the goal be light weight enough to be moved by the people using it, or the entity which controls it. Therefore, an unrestrained, light-weight goal can easily become unstable and tip over. Many of these goals are unsafe because they are improperly designed, manufactured or installed (unstable and are either unanchored or not properly anchored or counter balanced). A U-10 soccer goal has been designed and built which is light weight, portable and is stable with or without anchors. This design is passive in nature. That is to say it is always working and does not rely on stakes or sandbags; however, stakes are part of this design.
Active Tuning of Variable Stiffness Structures Utilizing Fluidic Flexible Matrix Composites
Authors: Philen Michael
Published: May 2009

Active tuning of a variable stiffness structure utilizing fluidic flexible matrix composites (F2MC) through valve control is investigated in this research. Previous efforts have shown that significant changes in the effective modulus of elasticity can be achieved by simply opening and closing the inlet valve to the fluid filled F2MC tubes. Through integration of the F2MC tubes into supporting matrix materials, multicellular variable stiffness adaptive structures can be achieved. The new adaptive structures can be easily deformed when desired (open valve) and can be switched to a high modulus mode when deformation is not desired (closed valve – locked state). In this paper, active valve control is investigated for improving the performance of the variable modulus structure over the semi-active approach (on/off valve control). An analytical model of the fluid-filled F2MC tube is developed that captures the dynamics of the composite tube and the flow rate of the fluid through a variable orifice. A feedback controller for modulus tuning is determined. Analysis results indicate that the modulus of the structure can be accurately tuned by active valve control. Advantages over semi-active valve control are increased performance, greater control of modulus selection, increased applicability, and elimination of potentially damaging pressure spikes observed with on/off valve control.
Assessment of Cooling Enhancement of Synthetic Jet in Conjunction With Forced Convection
Authors: Utturkar Yogen , Arik Mehmet , Gursoy Mustafa
Published: May 2009

Synthetic jets are meso or micro fluidic devices, which operate on the “zero-net-mass-flux” principle. They impart a positive net momentum flux to the external environment, and are able to produce the cooling effect of a fan sans its ducting, reliability issues, and oversized dimensions. As a result, recently their application as electronics cooling devices is gaining momentum. Traditionally, synthetic jets have been sought as a replacement to the fan in many electronic devices. However, in certain large applications, complete replacement of the fan is not feasible, because it is necessary to provide the basic level of cooling over a large area of a printed assembly board. Such applications often pose a question whether synthetic jet would be able to locally provide reasonable enhancement over the forced convection of the fan flow. In the present study, we present the cooling performance of synthetic jets complementing forced convection from a fan. Both experiments and CFD computations are performed to investigate the interaction of the jet flowfield with a cross flow from fan. The inlet velocity, jet disk amplitude, and channel height are varied in the computational simulations to evaluate the impact of these changes on the cooling properties. Overall, both studies show that a synthetic jet is able to pulse and disrupt the boundary layer caused from fan flow, and improve heat transfer up to 4× over forced convection.
Wave Variable Based Force Control
Authors: Hart J. Scot , Niemeyer Gu¨nter
Published: May 2009

Wave variable controllers maintain passive communication across time delays in telerobotics. As passive elements, wave variable controllers interact well with other passive elements, such as P.D. controllers and masses, and use a combination of force and velocity signals to apply force feedback. Currently we are exploring the use of wave variable controllers with large non-backdrivable industrial-type slave devices where dynamics are dominated by inertial and frictional forces. The objective is to integrate force sensor measurements into wave variable controllers to provide low frequency force feedback and hide the slave’s friction and inertia from the user in the presence of a communication time delay. This paper presents and uses a wave variable based approach to design force control. The resulting wave variable based force controller is converted to power variables and shown to be similar to traditional force controllers. A 1-DOF telerobotic system is used to experimentally show the wave variable based force control combines with the enhanced stability properties of the wave communication channel to produce robust slave side force control. The resulting system is better able to maintain force control with rigid environments then a traditional controller both with and without communication time delay.
Design Optimization of an Actuation Mechanism for a Dual-Arm Robotic Manipulator
Authors: Krishnasamy Jay , Hosek Martin
Published: May 2009

The design optimization of an actuation mechanism for a dual-arm scara-type robotic manipulator is presented. The manipulator is to be used in a vacuum environment for wafer handling applications in the semi-conductor manufacturing industry. The actuation mechanism consists of a pivoting platform that serves as the common driver link for two four-bar mechanisms each of which drives a scara-type arm. Each of the scara-type arms has a substrate carrying end-effector to pick from or place substrates on a process module. When the pivoting platform is in its neutral position, both of the arms are retracted. When the platform swings to one side, the arm on that side extends while the arm on the other side remains close to retracted position. The actuation mechanism is unique in that it uses just one motor to control the extension of both arms in contrast to the conventional design where each arm requires a motor of its own. However, the design needs to be optimized in order to minimize the effects of kinematic coupling between the two arms and, at the same time, keep the motor torque requirements and encoder resolution requirements to within practical limits. In this article, the relationships between the link lengths of the actuation mechanism, the kinematic coupling between the two arms, maximum encoder resolution requirements and motor torque requirements are described. These relationships are presented in the context of motion profiles characterized by limits on substrate acceleration — a typical requirement in wafer handling applications in vacuum. A methodology for determining link lengths to minimize motor torques and kinematic coupling between arms is presented.
A Novel Method for Melt Flow Control and Inclusion Suppression in Optical Crystal Growth
Authors: Fang Haisheng , Zheng Lili , Zhang Hui , Hong Yong , Deng Qun
Published: May 2009

Optical and laser crystals grown by Czochralski technique from a solute-rich melt usually suffer defects of melt inclusion or bubble core, which severely affects optical, thermal and mechanical properties of the material. The main purpose of this paper is to study the inclusion mechanisms and to minimize such defects. Two types of mechanisms possibly responsible for inclusion defects are presented. In the current investigation, Czochralski grown optical single crystals are examined to recognize the effects of crystal rotation and natural convection on the melt flow pattern and solidification interface shape. It is established that increasing the rotation rate of crystal or reducing natural convection in the melt will cause the solid-liquid interface change from the convex shape to concave and high concentration of the species may be pushed away from the solidification interface. Simulations were performed to establish the relationships between Gr/Re2 and growth interface shape change, and between Gr/Re2 and stagnant point location were established. A disk submerged into the melt was used to reduce natural convection by reducing the melt height. The idea was similar to the submerged baffle or submerged heater used in Bridgeman crystal growth. The effect of submerged baffle on enhancement of crystal rotation effect was demonstrated. Simulation results showed that the melt flow near the solidification interface depended strongly on the baffle location, which was not surprised. The idea of submerged heater was also examined in Czochralski growth. Different from a constant temperature close to the melting temperature used in Bridgman growth, the submerged heater temperature should be selected on a higher temperature between the melting temperature and crucible temperature. The value depended strongly on the ratio between crystal and crucible diameters. It was proved that a constant temperature was not the best choice in Czochralski growth. In fact, an optimized temperature profile could be found in numerical simulations for melt flow control and inclusion suppression.
Energy and Exergy Performance of Building HVAC System With Cogeneration Plant in Subtropical Climate
Authors: Feng M. , Tao Y.-X.
Published: May 2009

This paper presents an efficiency analysis, from both first law and second law of thermodynamics point of view, of a building HVAC system with on-site natural gas driven co-generation energy system. The building used for the case study is a university teaching and research complex located in Miami, Florida. The building’s original service centrifugal chiller plant and natural gas boiler are compared with the proposed cogeneration system based on energy and exergy performance. Because of the complexity of the system configuration and control schemes, building energy simulation code EnergyPlus is used as the primary tool to solve the energy balance equations. Further mathematical model for individual process exergy destruction, i.e. space cooling, dehumidification, VAV box reheating, mechanical ventilation, cooling tower evaporation, etc. are developed. To address both the processes of space cooling and dehumidification, the reference state which is associated with ambient temperature and humidity ratio is used throughout the analysis. The simulation results meet well with on-site measurement of energy usage. It is found that at whole system level, exergy efficiency is generally much lower than that of energy. The performance of chiller plant, natural boiler, air handling unit is far from thermodynamic ideal operation. By comparing different chiller plant modification scenarios, the cogeneration energy system with centrifugal chillers demonstrate the ability to increase both energy and exergy efficiencies for the overall system. The system with single-effect absorption chiller exergy efficiency is the lowest among all the candidate scenarios. The implication between exergy efficiency and sustainable building is discussed. To further improve the exergy efficiency, low exergy resources such as geothermal and solar heating should be used.
Real-Time Process Quality Monitoring Using Wireless Sensor-Embedded Rotary Tools for Fastening Operations
Authors: Mohan Deepak T. , Birt Jeffrey , Saygin Can , Sarangapani Jaganathan
Published: May 2009

Fastening operations are extensively used in the aerospace industry and constitute for more than a quarter of the total cost. Inspection of fasteners is another factor that adds cost and complexity to the overall process. Inspection is usually carried out on a sampling-basis as a stand-alone process after the fastening process is completed. Lack of capability to inspect all fasteners in a cost effective manner and the need to remove non-value added activities, such as inspection by itself, in order to reduce the manufacturing lead time have been the motivation behind this study. This paper presents a novel diagnostics scheme based on Mahalanobis-Taguchi System (MTS) for monitoring the quality of rotary-type fastening operations in real-time. This approach encompasses (1) integrating a torque sensor, a pressure sensor, and an optical encoder on a hand-held rotary-type fastening tool; (2) obtaining process parameters via the embedded sensors and generating process signatures in real-time; and (3) detecting anomalies on the tool using a wireless mote that communicates the decision with a base station. The anomalies investigated in this study are the grip length variations as under grip and normal grip, and presence of re-used fasteners. The proposed scheme has been implemented on prototype rotary tool for bolt-nut type of fasteners and tested under a variety of experimental settings. The experimental results have shown that the proposed approach is successful, with an accuracy of over 95% in detecting grip lengths of fasteners in real-time during the process.
Verification and Validation Studies for a Piloted Methane-Air Jet Flame
Authors: Skudarnov Peter V. , Lin Cheng-Xian , Gokaltun Seckin
Published: May 2009

In this paper, verification and validation analysis for a turbulent jet flame is presented. The numerical simulations were performed for a piloted methane-air jet flame in an axisymmetric burner (jet Reynolds number of 22,400). Numerical results were obtained using the finite volume method on structured grids. The verification of the numerical solutions was performed by calculating the Grid Convergence Index (GCI). A set of three different grids is used to calculate the discretization uncertainty where each grid was generated by doubling the number of cells in each direction of the coarser grid. The value of GCI was used to calculate the observed order of convergence of the numerical method for local values of temperature, mass fraction of species and local velocity at various points along the centerline of the flow domain. A detailed chemical mechanism was used with 16 species and 41 reactions. Numerical simulations showed that the fine grid result was in the asymptotic range of convergence. The observed order of convergence was found to be between 1.8 and 4.5. The error band for the Richardson extrapolated value was found to be below 1.3%. The effect of k-ε turbulence parameter C2ε was investigated and a value of 1.8 was found to be appropriate to match the fine grid results with the experimental data. Finally the numerical results were validated with experimental data using the local measurements of temperature and species mass fractions. Comparison of the computational results with experimental data showed that simulations correctly predict the trends observed in the measurements. Good agreement between experiments and simulations was obtained with the finest grid, which predicted peak temperature within 3.0% of experiment. For the main reaction products of CO2 and H2O, the peak values are captured within 0.33% and 3% of experiment, respectively.
Determination of Pool Boiling Critical Heat Flux Enhancement in Nanofluids
Authors: Truong Bao H.
Published: May 2009

Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed a CHF enhancement up to 68% and there seems to be a monotonic relationship between the nanoparticle concentration and the magnitude of enhancement. Alumina nanofluids had a CHF enhancement up to 56% but the peak occurred at the intermediate concentration. The boiling curves in nanofluid were found to shift to the left of that of water and correspond to higher nucleate boiling heat transfer coefficients in the two-phase flow regime. Scanning Electron Microscopy (SEM) images show a porous coating layer of nanoparticles on wires subjected to nanofluid CHF tests. These coating layers change the morphology of the heater’s surface, and are responsible for the CHF enhancement. The thickness of the coating was estimated using SEM and was found ranging from 3.0 to 6.0 micrometers for Alumina, and 3.0 to 15.0 micrometers for Silica.
State Forecasting for Rotary Machine Based on Neural Network and Genetic Algorithm
Authors: Liu Hongmei , Wang Shaoping , Ouyang Pingchao
Published: May 2009

A state forecasting is a key technology to achieve the advanced predictive maintenance. A Prediction based on neural network is a new approach to realize the state predicting. The present neural networks predicting models are comparatively poor in adaptability to environment and in predicting accuracy, therefore, a new rotary machine online state forecasting method based on the genetic algorithm (GA) and neural network (NN) was presented. GA was used for dynamical optimizing the structure parameters of BP network to obtain the optimal network structure. A training algorithm combining GA with BP was adopted to avoid the local minimum and to heighten the learning precision. The state predicting results for hydraulic pump indicate that the predicting model purposed may dynamically optimize the structure parameters in accordance with different conditions, and gained satisfactory results.
Discharge of Granular Materials From Hoppers With Various Exit Geometries
Authors: Ahn Hojin , Yilmaz Erkan , Yilmaz Mustafa , Bugutekin Abdulcelil
Published: May 2009

The discharge of glass beads from axisymmetric hoppers was experimentally investigated. Two types of hoppers were employed: one was of conical hoppers with different angles and the other was nozzle-shaped. The result showed that, for a conical hopper with a hopper angle greater than 45°, the hopper angle had little effect on the discharge coefficient. On the other hand, for a hopper angle less than 45°, the discharge coefficient rapidly increased with decreasing hopper angle. The present data agreed well with other experimental data available in the literature. The discharge coefficient of the nozzle-shaped hopper was measured to be as considerably high as that of a conical hopper with the hopper angle of 10°. Preliminary investigation on velocity profiles at hopper exits was conducted by examining the traces of particles in digital photographs. Visual observation on the degree of spread of the jets of particles coming out of hoppers with different hopper angles indicated that the velocity profile at the exit for a narrow hopper was more uniform than that for a wide hopper.
Automated Assembly of Fibre Preforms for Economical Production of High Performance Composite Parts
Authors: Gebauer I. , Do¨rsch C. , Thoben K.-D. , Mu¨ller D. H.
Published: May 2009

The demand of the market and the application require innovative process technologies for fast, cost-effective and quality-driven manufacturing of components made of fibre reinforced plastics. The Bremen Institute for Engineering Design (BIK) is developing and improving machineries and process technologies for the automated handling of fabric parts. Beside resin infusion processes, the handling of angular flexible material has become an important task to improve part quality and process cycle times. As a result of the systematic development current handling devices and installed applications will be demonstrated in this paper. For the production of FRP-parts by resin infusion processes several handling strategies are possible. The prototypes of the effectors are implemented in a flexible manufacturing cell. The feasibility of the implemented handling systems is proven by experimental investigations.
A Collaborative Approach to Teach Modeling and Control of Smart Actuators in the Mechanical Engineering Curriculum
Authors: Leang Kam K. , Pannozzo Gina , Zou Qinze , Devasia Santosh
Published: May 2009

In this article, we describe a collaborative approach to develop, integrate, and assess a teaching module on smart actuators specifically designed to embed topics in nano/bio technology into the undergraduate mechanical engineering (ME) curriculum. The collaboration involves three universities, each focusing on one specific aspect of the module. The module consists of lectures and laboratory activities that cover modeling and control of smart actuators for courses such as system dynamics, controls, and mechatronics. The integration of smart actuators — such as piezoelectric, shape memory alloy (SMA), and magnetostrictive based devices — into the ME curriculum is important because these devices are the workhorse in a multitude of nano and bio technologies. Thus, these devices play a critical role in the emerging areas, analogous to the benefits of the electric motor at the macroscale. But contrast to the well established coverage of the electric motor in the ME curriculum, modeling and control of smart actuators has yet to be systematically presented in core ME courses. The contribution of this article is presenting the systematic development, integration, and assessment of a teaching module on smart actuators. We first describe the design of lecture components using the piezo actuator as an example. The lecture materials cover core concepts within the framework of dynamics and controls, such as electromechanical coupling, dynamic response, nonlinear input-output behavior, and PID feedback control technique for high-precision positioning. Afterwards, we describe the development of a hands-on laboratory experiment designed to expose students to the basics of experimental modeling of the piezo actuator. The platform is also suited for basic control applications, and an example is presented to illustrate the application of piezo actuator control for high-precision positioning. The paper concludes with a discussion on how the module will be implemented and assessed at the three participating universities.
Finite Element Analysis on the Behavior of Laminated Composite Shells With Embedded Shape Memory Alloy Wires
Authors: Cho H. K.
Published: May 2009

Motivated by needs such as those in the aerospace industry, this paper demonstrates the thermomechanical characteristics of static and dynamic (frequency) behaviors of laminated composite shells with embedded shape memory alloy (SMA) wire subjected to temperature environments. Numerical analysis for SMA fiber reinforced composite laminates is performed by synergizing finite element method with Brison’s model [1,2] of SMA constitutive law. A nonlinear finite element procedure with respect to shape memory alloy hybrid composite (SMAHC) shell has been developed which incorporates a thermodynamically derived constitutive law for SMA behavior. Present illustrative applications involve rectangular laminated panels clamped along one side, although the method is applicable to more complicated laminates, geometries and boundary conditions. Panel geometry is discretized into specially-developed 3D degenerated eight-node laminated composite shell elements. General shell theory, involving incremental nonlinear finite element equilibrium that includes large deformations with Green-Lagrange strains, is employed. Several test cases which depend on volume fraction of SMA, temperature and ply angles are presented to illustrate the thermomechanical behavior of SMAHC. The results of numerical analysis show the ability of the suggested procedure to compute the thermomechanical behavior of SMAHC due to SMA’s internal phase transformations with stress and temperature.
Gas Heater Availability Analysis and Consideration of Replacement Gas Heaters by Inline Heaters in the Pressure Reducing Stations of Natural Gas
Authors: Shokouhmand H. , Rezaei Barmi M. , Tavakoli B.
Published: May 2009

Natural gas is transferred in high pressure by piping system from refiners to city gate stations. For public consumption the gas pressure is reduced in gas pressure reducing stations. The pressure is reduced in regulators and leads to a sudden drop of temperature and consequently the formation of gas hydrates. Preventing hydrate formation, natural gas is heated by passing through water bath gas heaters. In this study, the thermodynamic efficiencies of water bath gas heaters were conducted. The effect of air-fuel ratio and the flow rate of the fuel on the efficiency of this instrument were studied. Also, the variations of efficiencies versus flame temperature have been considered and the optimum points in each state were obtained. From these comparisons, it can be concluded that, first law efficiency is suitable meanwhile second law efficiency is very low. The main reason of low second law efficiency is that high availability generation by fuel causes low enhancement in the availability of natural gas, passed through heaters. Also, one dimensional simulation has been employed to compute temperature distribution numerically in whole of a gas pressure reducing station with water bath gas heaters and with shell and tube heaters (inline heaters). Comparison between these two stations show that the gas pressure reducing station with inline heaters is more appropriate than the one with water bath gas heaters. Finally, water bath gas heaters and inline heaters have been studied economically by utilizing energy flow optimization model, EFOM. It is shown that the inline heaters have less cost of heat generation and they are more economical.
Propagation of Ultra-Short-Pulse Radiation in Participating Media: A Laguerre-Galerkin Solution
Authors: Okutucu Tuba , Yener Yaman
Published: May 2009

Transient analysis of the radiative transfer problem in participating media has become essential due to the recent applications involving extremely small time scales. In classical radiation problems, the time derivative term in the radiative transfer equation has a negligible order of magnitude compared to the others. Lasers of pico- to femtosecond pulse durations are now being used to investigate the properties of scattering and absorbing media in such applications as, optical tomography, combustion product analysis, and remote sensing. For such applications, the time derivative in the radiative transfer equation can no longer be neglected. Numerous approaches such as, integral formulation, direct numerical approach, discrete ordinates method, Monte Carlo simulations, and Galerkin technique have been introduced for the solution of transient radiative transfer problems in participating media. In the present work, Laguerre-Galerkin solutions for both rectangular and Gaussian incident pulse profiles are presented.
Distributed Control and Safety System for a Rehabilitation Arm Exoskeleton
Authors: Carignan Craig R. , Roderick Stephen N. , Naylor Michael P.
Published: May 2009

A modular control and safety architecture is described for a robotic arm exoskeleton designed for shoulder rehabilitation. The exoskeleton joints are partitioned into anthropomorphic sets based on the desired exercise protocol, which are then commanded using separate control modules. A composite control software architecture is used to enable simultaneous operation of joint sets in either impedance or admittance control modes. Preliminary hazard and fault tree analyses identified three major hazards, and a combination of redundant sensing, hardware limits and software safety checks were used to produce a single fail-safe design. A quantitative fault tree analysis was also performed to assess the risk of a hazard due to a failure. The application of this approach to the MGA Exoskeleton was shown to improve the safety of the overall system.
A Neural Network Model Based Approach to Detect Seal and Impeller Failures in Centrifugal Pumps
Authors: Thumati Balaje T. , Birt Jeffery , Bassi Neha , Sarangapani Jag
Published: May 2009

With the increased complexity of today’s industrial processes, maintaining equipment by preventing unscheduled downtime using monitoring hardware is a key challenge. Industrial statistics indicate that seal and impeller failures are predominant failure modes in centrifugal pumps and they are not adequately addressed in the literature. In this paper, a neural network (NN) based Nonlinear Autoregressive Moving Average with Exogenous input (NARMAX) model is used to develop fault detection scheme for detecting seal and impeller failures in centrifugal pumps. A rigorous methodology of detecting failures at the incipient stage is introduced. First a nonlinear relationship among the monitored parameters (inlet and outlet pressure, outlet flow, inlet and outlet temperature, and acceleration) where the previous values of the indicative parameters are used as inputs to the NARMAX model and the output being the value at the current instance is captured. The NARMAX modeled outputs are compared with the actual measured values in order to generate residuals. By choosing a suitable threshold, we could minimize false and missed alarms. Mathematical procedure for selection of threshold is derived in this paper. Along with the NARMAX model, an online approximator is used in the fault detection scheme for understanding the faults in the system. Experiments on the centrifugal pump seal and impeller failures were conducted by using a laboratory test bed. Experimental results show that the proposed fault detection scheme is able to successfully detect failures.
A Framework for Sharing Online Laboratory Resources
Authors: Li Yaoye , Esche Sven K. , Chassapis Constantin
Published: May 2009

Numerous online laboratory resources have been and continue to be developed by many educational institutions around the world. These resources include both remote laboratories, which are based on actual experimental devices accessed remotely, as well as virtual laboratories, which represent software simulations of experiments. In the vast majority of the cases, the remotely accessible online laboratories reported on in the literature represent stand-alone systems, which are typically difficult to share by large numbers of learners dispersed at various educational institutions. This has led to the existence of many functionally similar, but independently operating systems developed in many places. This paper will identify the common features of such online laboratory resources. Then, the framework for a network of interconnected resource managers, which facilitate the efficient implementation and deployment of as well as the subsequent search for and shared usage of online laboratory resources (e.g. remote experiments, virtual experiments, game-based environments, etc.), will be presented. A centralized resource repository is presented that enables the publishing of information on the existence and availability of specific resources through the network. Finally, an example is given that illustrates the issues relating to joining, publishing, searching for and accessing online laboratory resources in that framework.
Heat Transfer Analysis of Microgrooved Evaporator and Condenser Surfaces Utilized in a High Heat Flux Two-Phase Flow Loop
Authors: Cetegen Edvin , Baummer Thomas , Dessiatoun Serguei , Ohadi Michael
Published: May 2009

This paper investigates the heat transfer and pressure drop analysis of micro grooved surfaces utilized in evaporators and condensers of a two-phase flow cooling loop. These devices utilize the vapor-liquid phase change to transfer large amounts of heat, and they offer substantially higher heat flux performance with lower pumping power than most liquid cooling technologies. Microgrooved surfaces, combined with force-fed evaporation and condensation technology discussed in this paper yield high heat transfer coefficients with low pressure drops. Our most recent results, aiming to test the limits of the technology, demonstrated dissipation of almost 1kW/cm2 from silicon electronics using HFE 7100 as the working fluid. In a compact two phase system, the heat generated by the electronic components can be absorbed by microgrooved evaporators and rejected through the microgrooved surface condensers to liquid cooled slots with high heat transfer coefficients and low pressure drops on the refrigerant side. In the case of air-cooling, the same microgrooved surface heat exchanger can reject heat with a heat transfer coefficient of 3847 W/cm2 and a pressure drop of 4156 Pa. These heat transfer processes have the added capability of being combined and used together in a self-contained system cooled either by liquid or air.
On-Chip Preconcentration and Separation of Simple and Complex Analytes Using Isotachophoresis
Authors: Khurana Tarun K. , Persat Alexandre , Santiago Juan G.
Published: May 2009

We present a theoretical model and parametric study of isotachophoresis based preconcentration of trace analytes in microfluidic devices. We use a simple semi-analytical model to capture the self-sharpening effect of isotachophoretic boundaries and solve the unsteady problem of fluorescent analytes preconcentration inside these boundaries. We evaluate the influence of various experimental conditions to achieve rapid preconcentration of these simple analytes. We also experimentally demonstrate the non-ideal complexities exhibited by biological samples such as proteins and DNA. These higher molecular weight species, due to additional steric hindrance and wall interactions, exhibit more complicated electromigration behavior and preconcentration.
Effect of Defect on Elastic-Plastic and Creep Behavior of Cellular Materials
Authors: Ajdari Amin , Nayeb-Hashemi Hamid , Canavan Paul K.
Published: May 2009

Cellular solids, such as foams, are widely used in engineering applications. In these applications, it is important to know their mechanical properties and the variation of these properties with the presence of defects. Several models have been proposed to obtain the mechanical properties of cellular materials. However, some of these models are based on idealized unit cell structures, and are not suitable for finding the mechanical properties of cellular materials with defects. Furthermore, the creep response changes in cellular solids when the exposed temperature is higher than 1/3 of the material’s melting temperature. The objective of this work is to understand the effect of missing walls and filled cells on mechanical and creep behavior of both the regular hexagonal and non-periodic Voronoi structures using finite element analysis. The finite element analysis showed that on average the non periodic structures have inferior mechanical properties compared to that of the regular hexagonal structures with the same relative density. The yield stress of Voronoi structures had a mean of 27% lower compared to that of the hexagonal structure with the same relative densities. Defects, introduced by removing cell walls at random locations, caused a sharp decrease in the effective mechanical properties of both Voronoi and periodic hexagonal honeycombs. However, our results indicated that elastic properties of Voronoi Structures are more sensitive to missing walls when compared to those of regular honeycomb structures. The yield strength of Voronoi and regular honeycombs exhibited the similar sensitivity to cell wall removal. For creep analysis, the results suggest that removal of struts dramatically increases the creep rate. In the case of filled cells, regular honeycomb structures showed less sensitivity to the defect compared to Voronoi structures. The overall elastic modulus of the structure increased by 11% when 5% of cells were filled in regular hexagonal honeycombs while for Voronoi structure it had more significant effect (22% increase). The results also show that filled cell did not have a significant effect on yield strength of the regular and Voronoi structures.
Analytical and Experimental Investigation of Modal Disparity
Authors: Issa Jimmy , Mukherjee Ranjan , Diaz Alejandro , Shaw Steven
Published: May 2009

This paper describes an analytical and experimental investigation on the property of modal disparity in a vibrating structure. For a given structure, the concept of modal disparity describes its ability to generate significant changes in the mode shapes by some type of on-the-fly structural modification. In the present study we consider a vibrating beam that experiences a controlled stiffness change, induced by the activation and deactivation of an electromagnetic brake. The beam has two stiffness states corresponding to the two states of the brake. The mechanisms of braking and brake release are mathematically modeled using the principle of impulse and momentum and a finite element model of the beam that adequately describes both stiffness states is developed. The transformation matrix which maps the modal displacements and velocities between the two stiffness states is derived and it is shown that this matrix is a measure of modal disparity, i.e., how well energy can be redistributed between the modes. Experiments were conducted to validate energy redistribution between modes through stiffness variation. A clamped-clamped aluminum beam with a hinge and built-in electromagnetic brake was used for the experiments. A piezoelectric strain sensor was used for sensing and a pair of piezoelectric transducers were used for excitation. It is shown that significant amounts of energy can be shifted back and forth between different sets of modes in a systematic and predictable manner. This confirmation of modal disparity for a specific structural system opens the door for a number of potential applications in passive and active control of vibrating structures.
Fast-Response Smart Self-Assembling Biosensors for Biomarker Detection
Authors: Lai James C. K. , Schoen Marco P. , Ebrahimpour Arya , Bhushan Alok , Daniels Christopher K. , Leung Solomon W.
Published: May 2009

The development of biosensors has been astronomical with the advent of the rapid growth of nanomaterials and nanotechnology. Nanobiosensors are becoming ubiquitous in numerous biomedical applications. Thus, there is a great impetus to exploit smart nanoparticles and other nanomaterials for designing and fabricating smart nanobiosensors that are ultrasensitive and biocompatible. We are developing smart self-assembling biosensors that can detect specific biomolecules (e.g., enzymes, cofactors, metabolites, drugs, hormones, etc.) from micro- to nanomolar levels. Applications of the biosensors include detection of organ dysfunction and/or failure (e.g., liver malfunction, heart failure, etc.), early detection of malignant cancers, toxicant identification, and other biomarkers of diseases. Although nanobiosensors that possess high sensitivity and specificity have been designed and marketed, one fundamental issue remains to be resolved. This important issue is one concerning biocompatibility. Thus, in our development of smart biosensors using nanomaterials, we have adopted a dual purpose approach. (i) On the one hand, it is necessary to systematically and comprehensively evaluate the material properties, characterize and model the signal sensing ability, and determine the biocompatibility of materials to be employed for the design of nanobiosensors. (ii) On the other hand, it is imperative to identify the ideal criteria for the designs of fast-response smart self-assembling nanobiosensors for biomarker detection. Based on a critical review of the literature and consideration of the biocompatibility, functional characterization, and other related issues discussed above, we have identify a set of criteria for the design of fast-response smart self-assembling nanobiosensors for detection of multiple biomarkers. We have also identified many biomedical areas where such nanobiosensors can be applied to detect biomarkers for various diseases. Our dual purpose approach will ultimately lead to the design of much more biocompatible and highly sensitive nanobiosensors and diagnostic equipment (nanobiosensor arrays).
Characterization of Microfabricated Cantilever-to-Plane Electrostatic Fluid Accelerators for Cooling in Electronics
Authors: Hsu C. P. , Sticht C. , Jewell-Larsen N. E. , Fox Michael , Krichtafovitch I. A. , Mamishev A. V.
Published: May 2009

Existing thermal management methods for electronics do not meet technology needs and remain a major bottleneck in the evolution of computing, sensing, and information technology. The decreasing size of microelectronic components and the resulting increasing thermal output density require novel cooling solutions. Electrostatic fluid accelerators (EFAs), also known as electrohydrodynamic (EHD) ionic wind pumps, have the potential of becoming a critical element of electronic thermal management solutions. In our previous experiment, a proof-of-concept meso-scale microfabricated silicon EFA device was demonstrated for enhanced forced convection cooling, enabling a maximum surface temperature reduction of 25°C over an actively heated substrate. In order to further investigate its feasibility for cooling in electronics and enable further device optimization for cooling purposes, it is essential to analyze key characteristics of microfabricated silicon EFA devices. The EFA devices investigated in this study consist of a microfabricated silicon cantilever corona electrode, and a wide and flat collector electrode. Experimental setups include one for current vs. voltage (IV) measurement and one for the longevity test. IV measurements were conducted for cantilever structures with lengths of 5 mm and 8 mm for electrode separation distances of 5, 4, 3, and 2 mm. The tested devices include uncoated and TiW-coated silicon cantilever structures. In the longevity tests, only uncoated silicon cantilever structures were tested and an electrode separation distance of 5 mm was used.
Output Feedback RHC for Constrained Linear Systems
Authors: Chen Youhua , Wu Fen
Published: May 2009

In this paper, we address the problem of synthesizing output feedback control law for constrained linear systems. For lack of state information, the plant states will be estimated by an observer. Using the Lyapunov function of estimated plant and controller states, the constrained output feedback control problem will be formulated and solved in terms of linear matrix inequalities (LMIs). The quadratic cost function is minimized over control policies to yield an output feedback control strategy subject to input/output constraints. Both infinite-horizon and finitehorizon receding horizon control (RHC) are considered in the paper. Closed-loop stability and feasibility of RHC are guaranteed by off-line constrained control designs. The simulation results show that finite-horizon RHC provides better performance upper bound than infinite-horizon RHC.