bluuebunny/crossref_metadata_2025 huggingface dataset:
The Experimental Determination of a Condition Indicator for Condition Based Maintenance
Authors: Farrington Seth E. , Buttram M. Paul , Boyles Charles
Published: August 2012

The objective of this paper is to present the investigation of a condition indicator to be used for a bearing. Reliability centered maintenance is implemented from the findings of reliability failure analysis. Reliability centered maintenance is implemented through either condition based maintenance or time-directed maintenance. Reliability failure analysis is performed through the inspection of a failed component either from failures in the system in use or from controlled laboratory experiments. This paper details the design and set up of a mechanical test bed used to demonstrate reliability failure analysis for the determination of condition based maintenance. The test bed consists of an electric motor driving a loaded shaft with a bearing as the test article. The load on the shaft is supplied by a screw jack and monitored by a load cell. A two factor, two level experiment with three replications is run. The two factors are load and rpm. The test is run above and below the load ratings for the bearing at high and low rpm. Each of the tests was run for twenty four hours or until bearing failure. The temperature and vibration of the test bearing was monitored throughout the duration of each test, and the bearings are characterized for wear at the completion of the test. A failure model with hazard function is presented and evaluated.
Deformation and Stress Analysis of the Fullerene by Super Element
Authors: Sarvi Masoud Nasiri , Ahmadian M. T. , Barari Ahmad
Published: August 2012

Accurate prediction of static and dynamic response of nano structures is one of the important interests of scientists in the last decade. Nano bearing as an important part of nano machines has been extensively implemented in recognizing and disassembling cancerous cells and building molecular support structures for strengthening bones. For this reason, Molecular Dynamic Method and some experimental methods are implemented in this area. As nano ball bearing is one of the most important components of nano machines, a large number of studies are concentrated to analyze it statically and dynamically. In this paper, a Fullerene is simulated by a spherical super element whose stress, deformation and natural frequency are calculated. The Fullerene is considered to be the C60 which is properly similar with a 66 surface-node spherical super element. In this study the mechanical properties of the fullerene and boundary conditions of the nano ball bearing under loading are introduced and stress and natural frequency of a fullerene under concentrated load is presented with two different strategies, super element and conventional elements. Compatible findings of these two methods validate and confirm the results. Findings indicate that applying 1 super element for the simulation of the fullerene leads to same results as implementing 154764 conventional elements.
F-22 MECSIP Lessons Learned: Risk Based Fatigue Scatter Factors High Durability Margin Analysis Using Miner’s Rule and Weibull Analysis
Authors: Glista Stefan M. , Postema Weibe , Arcusa Lily , Clark Brad
Published: August 2012

A top-level safety requirement for aircraft is that the probability of structural failure, resulting in the loss of aircraft, shall be less than 1 × 10−7 per flight hour. A reasonable approach to justify fatigue scatter factors is to derive them from this top-level safety requirement. The minimum scatter factor that can be justified using Weibull analysis is a function of the material data and stress level. Typical results at realistic stress levels range from 8 to 16 lifetime analytical margin to the characteristic life of the S-N data set. Weibull analysis results demonstrate that a 4-life time test provides high probability of detecting a design margin shortfall. Scatter Factors are also derived for design loads and life tracking loads. The analysis discussion addresses single-point-failure safety critical structure; however, a Weibull based probability analysis for multiple-load-path structure with dependent failure mechanisms is also included. Graphical and statistical proofs justify the material scatter factors. The F-22 program uses Weibull based probability analysis for design margins, testing, certification and life management. We call the risk based scatter factor approach High Durability Margin Analysis (HDMA).
ALD Enabled Nickel MEMS Switches for Digital Logic
Authors: Hall Harris J. , Davidson Bradley D. , George Steven M. , Bright Victor M.
Published: August 2012

CMOS transistor based digital logic technology has delivered spectacular levels of device integration and processing capability since its advent. However, traditional CMOS device performance remains limited in harsh environments, such as high temperature or irradiated environments. Electrostatically actuated MEMS/NEMS switches offer improved performance in these environments. In this work, out-of-plane three terminal microswitches suitable for digital logic are presented. Each switch consists of a suspended fixed-fixed bowtie shaped electroplated nickel beam (300μm × 250μm × ∼2μm) buckled out-of-plane over a 10μm wide gold electrode on a LPCVD nitride coated low resistance Si substrate, which acts as a common gate electrode. Atomic layer deposited (ALD) alumina (100nm thick) is incorporated as a sacrificial layer to keep the fabrication processing low temperature and provide precise gap uniformity across chip. Steady-state I-V performance results are presented showing contact voltages between 17–36V. Mechanical modeling of the beam deformation is performed using commercial FEA software and compared to the actual measured beam response. These devices offer a valid approach for simple MEMS based logic circuitry with proper film stress management and geometry scaling.
Application of Tornado-Flow Fundamental Hydrodynamic Theory to the Study of Blood Flow in the Heart: Further Development of Tornado-Like Jet Technology
Authors: Bockeria L. A. , Kiknadze G. I. , Gachechiladze I. A. , Gorodkov A. Y.
Published: August 2012

It has been proved previously that the Tornado-like swirling flows have strictly ordered hydrodynamic structure which can be exhaustively described by using the exact solution of non-stationary Navier-Stokes and continuity equations for this class of flows [1]. Analysis of the geometry of the flowing channel of the left ventricle (LV) and aorta has shown close correlation between the shape of the cavities and intraventricular trabeculae orientation with the streamlines of Tornado-like flows. LV casts morphometry, MRI tomography and 4D velocimetry of the flow velocity field in the aorta, allowed to prove that the blood flow in the LV and aorta corresponds to this class of flows and may be described using the exact solution [7,8,10]. The current study proposes a method of measurement and calculation of the flow structural parameters derived from the exact solution, using LV cavity casts morphometry in humans and dogs and Multislice computed tomography (MSCT) of LV in two patients without severe cardiac pathology. It has been shown that the dynamic expression of intracardiac trabeculae and instant shape of LV cavity within a complete cardiac cycle correspond closely to the stages of single Tornado-like jet evolution. Since the intraventricular trabeculae profile is streamlined continuously by the blood flow, it should determine the hydrodynamic flow structure as an ensemble of guiding vanes. Therefore it has been concluded that the intraventricular flow dynamics can be analyzed and quantified using the exact solution. Application of this analysis to the MSCT visualization of LV cavity dynamics has shown the validity of this approach, which may be used for clinical diagnostic purpose. A realistic mathematical model of intraventricular blood flow has been proposed and evaluated. The results showed a good agreement between the model and known cardiac anatomy and function.
Standardized Calculation of Bolted Joints for Future Requirements
Authors: Friedrich C. , Hubbertz H. , Dinger G.
Published: August 2012

The title of this paper covers two questions: a) Which items have to be considered for ‘Standardized Calculation’? b) Which ‘requirements’ have to be focused in future? The contribution starts with the fundamental approach of bolted joint mechanics, looks to the focus of present design standards and lists the main risks for bolted joints today. From this the future requirements are derived. Examples are given to selected aspects. Conclusions are drawn to overcome the future challenges for bolted joint design with five needs.
Sports Engineering Program at UCD
Authors: Jenkins Peter E.
Published: August 2012

The University of Colorado Denver (UCD) has taken the leadership role with the first Sports Engineering Program in the United States. Sports Engineering is an exciting new area of emphasis for graduate degrees in engineering. This educational program is offered through cooperation between the downtown Denver College of Engineering and Applied Science and the Anschutz Medical Campus, both part of the University of Colorado Denver. This program is showing great promise for high enrollments and exciting research opportunities working with the sports equipment manufacturers, the athletes, and the sports medicine community.
Analytical Solution for Temperature Distribution in Microwave Heating of Rectangular Objects
Authors: Hossan Mohammad Robiul , Dutta Prashanta
Published: August 2012

Microwave heating is extremely popular as a household method for warming up foodstuffs quickly. However the industrial application of this convenient, pollution free heating technique is very limited because of its non-uniform temperature distribution with hot and cold spots. The temperature distribution in microwave heating depends on the electromagnetic frequency, processing time, size and shape, and dielectric properties of the object being heated. In this paper, we present a close form analytic solution for temperature distribution in a three dimensional rectangular block under microwave processing. With the knowledge of electric field distribution from Maxwell’s equation, a three dimensional, unsteady, non-homogenous energy equation containing a microwave source term is solved by the integral transform technique. The effects of various parameters such as sample thickness, electromagnetic frequencies, dielectric properties, and processing time are studied for a salmon fillet. The results indicate that the proper integration of incident frequencies, dielectric properties, sample thickness and processing time could provide homogenous temperature distribution in a salmon fillet under microwave heating.
Separate Parameters Identification of the Miso Time Delay Model Applied to the Heat Transfer Process
Authors: Simeunovic´ G. V. , Zi´tek P. , Vyhli´dal T. , Debeljkovic´ D. Lj.
Published: August 2012

The paper presents the identification issues and the parameters identification algorithm that separates the system parameters from the time delays for a class of multi-input single-output (MISO) linear time delay systems (LTDS). The presence of the unknown time delay greatly complicates the parameter estimation problem, because the parameters of the model are not linear with respect to the time-delay in terms of the identification. This problem for SISO systems is solved in the papers [6] and [7]. Solution presented in the previous mentioned paper is based on the nonlinear least square problem developed in the paper [1]. In this paper, the approach worked out in the papers [6] and [7] is extended to the class of MISO systems. The multipoint search method based on the Quasi-Newton technique is used for the minimization of variable projection functional. The special Quasi-Newton algorithm, which involves the several initial conditions treated at the same time, developed in [5], is applied here. This approach is illustrated by a particular application in the field of the heat transfer, on the time-delay model of the heat exchanger in the laboratory environment.
Numerical Simulation of Flow Boiling of Binary Mixtures Using Multi-Fluid Modeling Approach
Authors: Srinivasan Vedanth
Published: August 2012

In this paper, the development of a new mass transfer model to simulate the thermal and phase change characteristics encountered by binary mixtures during flow boiling process is discussed. A new boiling mass transfer model based on detailed bubble dynamic effects, inclusive of local bubble shear, drag and buoyancy dynamics, has been developed and full implemented within the commercial CFD code AVL FIRE v2010. In the present study the phasic mass, momentum and energy equations are solved in a segregated fashion in conjunction with an interfacial area transport and a number density equation to study the heat and mass transfer characteristics of binary flow boiling inside a rectangular duct. Turbulence in the fluidic system and those generated by the bubbly flow are treated using an advanced k-ζ-f model. The simulation results comprising of flow variables such as volume fraction, fluidic velocities and temperature and the resultant heat flux generated on the heated wall section clearly monitors the suppression in heat transfer coefficients with enhancement in flow convection. Competing mechanisms such as phase change process and turbulent convection are identified to influence the heat transfer characteristics. In particular, the varying influence of the mass transfer effects on the heat flux characteristics with alteration in wall temperature is well demonstrated. Comparisons of the predicted heat transfer coefficients for varying wall superheat and varying fluidic velocity indicates a very good agreement with experimental data, wherever available. Description of the flow field inclusive of interfacial area and number density distribution is provided. The current model can be easily extended to simulate multiphase flow in complex systems such as a cooling water jacket for automotive applications.
Design and Analysis of a Car-Truck Stand
Authors: Clark John , Echempati Raghu
Published: August 2012

In this paper application of an example FEA/CAE tool (Finite Element Analysis/Computer Aid Engineering (Cosmos®) to the design and analysis of a typical car-truck stand used by the railways is discussed. The car-truck stand consisted of several pieces of A-500 steel tube and A36 steel welded together and is used to support one end of a freight car during maintenance operations. Design of experiments via Taguchi method approach was attempted to evaluate the car-truck stand currently used by the rail industry. Experiments were conducted to validate some of the simulation results. In this study, three parameters were evaluated (overall stand height, material thickness, and stand geometry). The Taguchi method consisted of nine experiments. Each of the nine experiments for each structure was evaluated using the CAE tool. Real experiments were also done on the current design of the stand and a static load test was conducted to validate some of the CAE results. The static test was done by fixing strain gages to the car stand and vertically loading the car stand. The output response which was measured is the safety factor determined from the CAE analyses. All resulted are presented in the form of tables and discussed.
Demonstration of an Integrated Micro Cryogenic Cooler and Miniature Compressor for Cooling to 200 K
Authors: Lewis Ryan , Lin M.-H. , Wang Yunda , Cooper Jill , Bradley Peter , Radebaugh Ray , Huber Marcia , Lee Y. C.
Published: August 2012

Joule-Thompson (J-T) based micro cryogenic coolers (MCCs) are attractive because they can provide the cryogenic temperatures needed for small electronic devices while having a low cost and small volumetric footprint. A compressor is a major part of a cryogenic system, but so far J-T based MCCs have not used miniature or micro scale compressors. This work demonstrates a J-T based MCC coupled with a miniature compressor for cooling to 200 K, using a custom hydrocarbon mixture as refrigerant. The compressor is formed by coupling a miniature piston oscillator built for Stirling coolers with a micromachined check valve assembly. The MCC is formed by glass fibers within a capillary forming a counter flow heat exchanger, and a silicon and glass chip forming a J-T valve. Minimum temperatures of 166 K have been observed in transient, and stable temperatures of 200 ±1 K have been observed for >1 hour. Some insight is given into the unstable performance in terms of intermittent liquid accumulation. The coefficient of performance is analyzed for the system, and it is found that most of the inefficiencies arise at the compressor.
Microscale Electrokinetics: Dielectrophoretic Manipulation of Particles
Authors: Lapizco-Encinas Blanca H.
Published: August 2012

Miniaturization is a rapidly growing field, with great potential for many applications, from cell and clinical analysis, medical diagnostics, food and water safety, and environmental monitoring. Working on the microscale offers significant advantages, such as shorter time, reduced sample requirement, higher resolution and sensitivity. There are important research efforts devoted to the development of separation and analytical techniques that can be employed on the microscale. Dielectrophoresis (DEP) is the motion of particles due to polarization effects when exposed to nonuniform electric fields; this electrokinetic transport mechanism has a great potential for the manipulation of a wide array of particles. DEP offers great flexibility, since it can be carried out employing DC and AC electric fields, and neutral and charged particles can be manipulated. Insulator-based dielectrophoresis (iDEP) is novel technique where insulating structures, instead of electrodes, are used to create nonuniform electric fields. This presentation is focused on the use of AC-iDEP and DC-iDEP for the manipulation, concentration y separation of different types of particles. Experimental and modeling results obtained with COMSOL will be presented and discussed, demonstrating the versatility and great potential of iDEP as a microscale technique for effective and highly controlled particle manipulation.
Investigation of Microcantilever Sensor for Explosive Detection
Authors: Kang Seok-Won , Banerjee Debjyoti
Published: August 2012

In this study we investigate the use of microcantilever sensors for explosives detection. An array of microcantilevers consisting of gold (Au) and silicon nitride (Si3N4) thin-films of sub-micron thickness acts as a thermal bimorph. A microheater is fabricated in-situ at the base of each microcantilever in the array. When the microheaters are addressed individually using different actuation currents, each microcantilever undergoes thermo-mechanical deformation by different amounts which are then tracked individually by monitoring each reflected ray from a laser illuminating the array of microcantilevers. The threshold current values for the differential actuation of the microcantilevers are correlated with the auto-ignition temperature of a particular explosive (or combustible vapor) and its corresponding vapor pressure. In this study numerical simulations are also performed to study the variation of temperature, species concentration and deflection of individual microcantilevers as a function of actuation current.
From Component to Macro Energy Systems: A Common Design and Off-Design Modeling Approach
Authors: Rech S. , Lazzaretto A.
Published: August 2012

A common approach for simulation of energy systems at design and off-design conditions is presented, which uses the same concepts and terminology independently of system dimension, complexity and detail. The paper shows that the higher the dimension of the system, the simpler is the model of each part of the system, but concepts and approach to built the model remain the same, being those commonly used in the literature. The approach consists in organizing energy systems models according to some criteria, which help enhance system models comprehension, and build them more easily. For any dimension and level of detail of the system these criteria consist in identifying the design specification from the environment surrounding the system, choosing the independent variables depending on the nature of the model, organizing them into categories, defining performance curves (characteristic maps) of each part of the system and organizing mass and energy balances into categories. Particular emphasis is given on modeling of system units behavior, which is generally described by the mathematical functions (characteristic maps) linking outflow to inflow variables. Examples of characteristic maps of the system units at each level of detail are shown, and models are then completed by mass, energy and momentum balances linking the behavior of all system units.
An Optofluidic Photobioreactor Strategy for Bioenergy
Authors: Ooms Matthew D. , Sieben Vincent J. , Erickson D. , Sinton D.
Published: August 2012

A novel approach to cultivating cyanobacteria is presented which utilizes near-field evanescent waves on the surface of waveguides to excite the photocenters in the thylakoid membranes of cyanobacteria. This approach to light delivery when applied to photobioreactor design may provide an opportunity to significantly increase yield and make biofuels an economically competitive alternative to traditional fossil fuels.
Rainwater Harvesting in a Common Pool Resource: An Engineering Perspective
Authors: Whear John H.
Published: August 2012

Water scarcity is a common problem throughout the Southwestern United States. Rainwater Harvesting (RWH), in urban and suburban environments, has potential to conserve existing water resources and reduce flash flooding. Currently, little is understood on how to effectively access this untapped resource. However, participants of a Common Pool Resource (CPR) can achieve resource efficiencies greater than 90 percent. An exhaustive search of published materials was conducted, coupled with communications with the Texas Water Development Board, Edwards Aquifer Authority, San Antonio Water System, and other municipal water utilities. Analysis of CPRs and their design principals reveals that only the Edwards Aquifer Authority and its associated Groundwater Districts constitutes a functioning groundwater CPR in Texas. Of the CPR design principals, only effective monitoring requires engineering. Under the correct circumstances, it would be more appropriate to view RWH as a nested enterprise inside a functioning CPR. This paper explores the possibilities and difficulties of engineering associated with RWH as a nested enterprise in a CPR, specifically RWH in the Edwards Aquifer. A CPR success depends on management rather than engineering. Success of a CPR and its nested enterprises depends on participant behavior. Economic models, based on the mathematics of game theory, help understand how participants of a CPR respond to issues of fairness and communication. A cost effective device can provide effective monitoring of RWH performance. Once monitoring is provided, RWH can be integrated into existing cooperative CPR institutions.
Optimizing the Mechanical Properties of Wood Plastic Composites Using Fiber-Glass
Authors: Ashrafi Mahdi , Olia Masoud , Vaziri Ashkan , Nayeb-Hashemi Hamid
Published: August 2012

Wood plastic composites (WPC) are widely used in the industry due to its durability, low cost, and anti-moisture properties in comparison with the natural wood. Recently, WPC are also being considered in musical instrument industry. In this research, we have produced flout shaped WPC samples using African black wood powder and Phenolic resin in a hot compression molding set-up. Initial WPC composites were produced by systematically changing the wood volume fraction. The results showed cracks developed in composites with more than 70% wood. This was related to formation of gas in the system during manufacturing and lack of fluidity in the system to flush the gases. Based on these results the optimum temperature, pressure and wood volume fraction for developing WPC in a form of a flute is developed. A series of experimental procedures were performed to improve mechanical properties of WPC samples by studying the effect short fiber-glass addition to the wood matrix prior to hot pressing. The results showed that the addition of short fiber did not improve the strength of WPC but rather than it reduced its strength compared to unreinforced composite. This was attributed to lack of bonding between short fibers and wood matrix. In contrast encapsulated wood particle composite in an E-glass/epoxy composite sheet before hot pressing showed the mechanical properties of wood composite are enhanced. A two layer unidirectional composite was sufficient for producing flute with desirable mechanical properties. On the basis of the experimental results, a very simple method to enhance the load-bearing capability of WPC which may allow producing reinforced WPC in the form of flout shape is developed.
Concurrent Type and Dimensional Synthesis of Planar Mechanisms Using Graph-Theoretic Enumeration, Automatic Loop Closure Equation Generation, and Descent-Based Optimization
Authors: Nelson Carl A.
Published: August 2012

An approach to concurrent type and dimensional synthesis of planar mechanisms is presented. Using graph-theoretic enumeration of mechanisms and determination of loops, automatic loop closure equations are generated. Using constrained optimization routines based on descent methods, and given an appropriate goal function, optimal mechanism designs can be determined. These are not limited to traditional problems such as rigid-body guidance and path generation, but can be more flexibly expressed according to designer needs. This method can be effective at finding mechanism solutions when topology has not been determined a priori and may also be extensible to synthesis of spatial mechanisms. This paper presents the data flow and algorithm outline, simulation results, and examples of nonstandard synthesis problems solvable with this method.
Thermal Characterization of Carbon-Carbon Composites
Authors: Saad Messiha , Baker Darryl , Reaves Rhys
Published: August 2012

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.
Novel, Gasketless, Interconnect Using Parallel Superhydrophobic Surfaces for Modular Microfluidic Systems
Authors: Brown Christopher R. , Farshchian Bahador , Chen Pin-Chuan , Park Taehyun , Park Sunggook , Murphy Michael C.
Published: August 2012

A novel, modular, microfluidic interconnect was developed using parallel superhydrophobic interfaces to facilitate the transport of fluids between component chips in modular microfluidic systems. A static analytical model, derived from the Laplace equation [1], approximates the maximum steady-state pressure of the liquid at the liquid bridge which forms across the gap between the chips. Preliminary experiments using parallel superhydrophobic surfaces on PMMA validated the concept. Additional experiments controlled the gap distance, measured contact angles of the superhydrophobic surfaces, gradually increased the pressure of the novel, gasketless, interconnect until rupture to find the maximum pressure across the liquid bridge and verify the model. The measured pressures were on the same order of magnitude (1–10 kPa) as estimated using the model for gap distances of 25 μm and 100 μm.
Nanoscale Structural and Mechanical Characterization of Nanowire-Reinforced Polymer Composites
Authors: Leininger Wyatt , Wang Xinnan , Tangpong X. W. , McNea Marshall
Published: August 2012

In this study, the mechanical properties of multi-walled carbon nanotube (MWCNT) reinforced epoxy composites were characterized using an in-house designed micro/nano tensile load stage in conjunction with an atomic force microscope (AFM). The surface of the nanocomposite was scanned by the AFM during intermittent tensile testing. Micro/nano deformation was observed, and the reinforcing mechanisms were discussed in conjunction with architecture and elastic modulus. Results show that the MWCNT reinforced nanocomposite has an increased elastic modulus. The Halpin-Tsai and Hui-Shia models were compared to the experimental results, and the Halpin-Tsai was found to correlate when only the load bearing outer layer of the MWCNTs were considered. Additionally, it is concluded that the combination of the load stage and AFM is capable of capturing insitu deformation progress for small strain increments.
CFD Analysis of Hydro Turbine Performance for Multi-Rotor Configurations
Authors: Zhang Ning , He Anpeng , Ballard Brent , Li Puxuan
Published: August 2012

Flow in a special designed multi-rotor hydro turbine was simulated using the immersed-boundary method. Thanks to the immersed-boundary method, the complicated flow-driven motion of the turbine components can be simulated. The Smagorinski-Lilly turbulence model was implemented in order to simulate the practical high-Reynolds-number cases. The rotor rotating speeds (RPM’s) of cases with different multirotor configurations were compared to obtain the optimal designs. The configurations studied include the size and position of the flow blocker, as well as the number of rotors. Detailed flow characteristics around the turbine was revealed from the simulation results.
An Admittance Type Haptic Device: RML Glove
Authors: Ma Zhou , Ben-Tzvi Pinhas
Published: August 2012

This paper presents the design and control of a newly developed five-fingered admittance haptic interface named RML-glove. This haptic device is a lightweight and portable actuator system that fits on a hand and adds a sense of touch to each finger of the user. With this system, the operator is able to feel the shape and size of virtual 3D objects or to control robots through force feedback. Each finger has a miniature linear actuator that can be individually controlled to provide the force feedback. An embedded lead screw mechanism makes it possible to provide force feedback from almost zero and up to 40 N to each finger. The interface consists of micro-motors, force sensitive sensors, lithium-ion battery, wireless RF module, and an ARM7 micro-controller board. Wireless communication with a robot or host PC is established via unlicensed bands of 2.4 GHz. This haptic device may be worn on the back of bare hand without any other intrusive hardware, which otherwise constrain the movement of the fingers.
Plate Damage Detection Using Vibration-Based and Static Deformation-Based Approaches
Authors: Shi Jing , Tangpong X. W.
Published: August 2012

Damage detection is important for sensing and analyzing the degradation of structures, and can effectively avoid potential catastrophic failures. Among the numerous studies in literature, most emphasis was given to the damage detection based on vibration response signals for simple beam structures. In this paper, the feasibility of roughness method for plates was investigated using both vibration-based data and static deformation data. Two detection methods, namely, roughness method and fractal dimension method, were used to analyze the data. Both types of data were obtained for aluminum plates using finite element simulation. It was found that both methods were able to detect the damage and locate its position precisely with the two types of signals. The effectiveness of damage detection using static deformation data was further demonstrated by experimenting with a cracked cantilever beam. A computer vision camera efficiently and automatically collected the static deformation data, and this approach showed great potential compared with the expensive and time-consuming collection process for vibration response data such as mode shapes.
Ultrasonic Vibration-Assisted Pelleting in Manufacturing of Cellulosic Biofuels: An Investigation on Biomass Particle Size
Authors: Zhang Pengfei , Zhang Qi , Pei Z. J. , Pei Linda
Published: August 2012

Biofuels made from cellulosic biomass are an alternative to petroleum-based liquid transportation fuels. However, several technical barriers have hindered cost-effective manufacturing of cellulosic biofuels, such as low density of cellulosic feedstocks (causing high transportation and storage costs) and low sugar yield in enzymatic hydrolysis. Ultrasonic vibration-assisted (UV-A) pelleting can increase the density of cellulosic feedstocks and the sugar yield in enzymatic hydrolysis. A hypothesis for UV-A pelleting to increase sugar yield is that UV-A pelleting reduces the particle size of cellulosic biomass. This paper reports an experimental investigation on effects of UV-A pelleting on biomass particle size. Particle sizes before and after UV-A pelleting are measured and compared. The results show that there is no significant difference between particle sizes before and after UV-A pelleting. Therefore, the hypothesis is rejected.
Bio-Inspired Robotic Cownose Ray Propelled by Electroactive Polymer Pectoral Fin
Authors: Chen Zheng , Um Tae I. , Zhu Jianzhong , Bart-Smith Hilary
Published: August 2012

The cownose ray (Rhinoptera bonasus) demonstrates excellent swimming capabilities; generating highly efficient thrust via flapping of dorsally flattened pectoral fins. In this paper, we present a bio-inspired and free swimming robot that mimics the swimming behavior of the cownose ray. The robot has two artificial pectoral fins to generate thrust through a twisted flapping motion. Each artificial pectoral fin consists of one ionic polymer-metal composite (IPMC) as artificial muscle in the leading edge and a passive PDMS membrane in the trailing edge. By applying voltage signal to the IPMC, the passive PDMS membrane follows the bending of IPMC with a phase delay, which leads to a twist angle on the fin. The characterization results have shown that the pectoral fin was able to generate up to 40% tip deflection and 10° twist angle with less than 1 Watt power consumption. A bio-inspired rigid body was designed using Computerized Axial Tomography (CT Scan) data of the cownose ray body and printed using a 3-dimensional printer. A light and compact on-board control unit with a lithium ion polymer battery has been developed for the free swimming robot. Experimental results have shown that the robot swam at 0.034 BL/S.
Performance and Reliability Analysis of an Off-Grid Hybrid Power System
Authors: Iverson Zachariah , Achuthan Ajit , Marzocca Pier , Aidun Daryush , Caird Ken
Published: August 2012

Small villages in remote locations of developing countries rarely have access to electricity and are highly dependent on burning fossil fuels for energy. In an effort to provide these villages with a quality power supply and to replace their current emissions-producing energy generation, we propose a Hybrid Power System (HPS) that uses small wind turbines and solar panels for power generation. The system manages the intermittency of the renewable power by storing excess energy during periods of low user demand (such as night time) and releasing that energy at demand peaks (times when people are using demanding appliances). The proposed storage method uses electrolysis, which is the separation of water molecules into hydrogen and oxygen by excess DC currents produced by the wind and solar. The hydrogen is then compressed and stored in metal hydride tanks and when demand exceeds wind and solar generation, power is provided using a Proton Exchange Membrane Fuel Cell (PEMFC), which is highly responsive in peak demand periods compared to other types of hydrogen fuel cells. A physics-based model of the HPS is constructed in order to improve its efficiency, and statistics-based reliability models are formed to evaluate its potential for loss of load. Efficiency of a HPS can be viewed as balancing the energy production with user consumption. For this purpose, accurate models of the subsystems (wind turbines, solar panels, an electrolyzer using metal hydride tanks for hydrogen storage, fuel cell stack) are created. Realistic models of the AC loads are also required; this includes models of a performance optimized data center (POD) and the power demanded by a small community. As to optimize the energy management of the entire system, a model of a main controller that utilizes closed-loop control systems to maintain power stability is designed. On the reliability side, analysis is performed to assess the system’s response to various failures over time. This work is aimed at examining the reliability of the power system; not the examination of failure data in order to improve the reliability of various components. Models for testing of performance are created on a MATLAB Simulink and SimPowerSystems platform.
The Mathematical Analysis of a Novel Approach to Maximize Waste Recovery in a Life Support System
Authors: McKellar Michael G. , Wood Rick A. , Stoots Carl M. , Mulloth Lila , Luna Bernadette
Published: August 2012

NASA has been evaluating closed-loop atmosphere revitalization architectures that include carbon dioxide (CO2) reduction technologies. The CO2 and steam (H2O) co-electrolysis process is one of the reduction options that NASA has investigated. Utilizing recent advances in the fuel cell technology sector, the Idaho National Laboratory, INL, has developed a CO2 and H2O co-electrolysis process to produce oxygen and syngas (carbon monoxide (CO) and hydrogen (H2) mixture) for terrestrial (energy production) application. The technology is a combined process that involves steam electrolysis, CO2 electrolysis, and the reverse water gas shift (RWGS) reaction. Two process models were developed to evaluate novel approaches for energy storage and resource recovery in a life support system. In the first model, products from the INL co-electrolysis process are combined to produce methanol fuel. In the second co-electrolysis, products are separated with a pressure swing adsorption (PSA) process. In both models the fuels are burned with added oxygen to produce H2O and CO2, the original reactants. For both processes, the overall power increases as the syngas ratio, H2/CO, increases because more water is needed to produce more hydrogen at a set CO2 incoming flow rate. The power for the methanol cases is less than pressure swing adsorption, PSA, because heat is available from the methanol reactor to preheat the water and carbon dioxide entering the co-electrolysis process.
Cavitation at Sharp Edge Multi-Hole Baffle Plates
Authors: Holt G. J. , Maynes D. , Blotter J.
Published: August 2012

This paper reports results of an experimental investigation of cavitation caused by water flow through sharp edge multi-hole baffle plates at high speeds and large pressure drops. Such cavitation can be destructive to industrial systems due to the induced pipe wall vibrations that result. Incipient and critical cavitation numbers are design limits that are frequently needed in the design of systems implementing baffle plate type geometries to prevent adverse cavitation effects. The overall baffle plate loss coefficient, point of cavitation inception, and point where critical cavitation occurs are functions of baffle hole size, number of holes, and plate thickness. Sixteen total baffle plates were considered in the study with hole sizes ranging from 0.16 cm to 2.54 cm, total through area ranging between 11% and 60%, plate thickness ranging from 0.32–0.635 cm, and number of holes ranging from 4 to 1800. The plates were mounted in the test section of a 10.2 cm diameter schedule 40 pipe closed water flow loop. The focus of this paper is on how the influencing parameters affect the loss coefficient and the point of cavitation inception. The results show a complex dependency between the baffle plate loss coefficient with total through area ratio and the thickness to baffle hole diameter ratio. In general the loss coefficient decreases with increasing openness and increasing thickness to hole diameter ratio. A model based on the data is proposed to predict the loss coefficient for multi-holed baffle plates. Further, the data show that the cavitation number at the point of cavitation inception increases with increasing openness. However, with regard to the thickness to hole diameter ratio, the cavitation number at inception exhibits a local maximum at a ratio between 0.5 and 1.0. Models to allow prediction of the point of cavitation inception and the point where critical cavitation begins are presented in the paper.
A Nonlocal Approach to Modeling Crack Nucleation in AA 7075-T651
Authors: Littlewood David J.
Published: August 2012

A critical stage in microstructurally small fatigue crack growth in AA 7075-T651 is the nucleation of cracks originating in constituent particles into the matrix material. Previous work has focused on a geometric approach to modeling microstructurally small fatigue crack growth in which damage metrics derived from an elastic-viscoplastic constitutive model are used to predict the nucleation event [1, 2]. While a geometric approach based on classical finite elements was successful in explicitly modeling the polycrystalline grain structure, singularities at the crack tip necessitated the use of a nonlocal sampling approach to remove mesh size dependence. This study is an initial investigation of the peridynamic formulation of continuum mechanics as an alternative approach to modeling microstructurally small fatigue crack growth. Peridynamics, a nonlocal extension of continuum mechanics, is based on an integral formulation that remains valid in the presence of material discontinuities. To capture accurately the material response at the grain scale, a crystal elastic-viscoplastic constitutive model is adapted for use in non-ordinary state-based peridynamics through the use of a regularized deformation gradient. The peridynamic approach is demonstrated on a baseline model consisting of a hard elastic inclusion in a single crystal. Coupling the elastic-viscoplastic material model with peridynamics successfully facilitates the modeling of plastic deformation and damage accumulation in the vicinity of the particle inclusion. Lattice orientation is shown to have a strong influence on material response.
Drying Kinetics of Solid Biomass
Authors: Barreiros Martins Luis A. , Reis Marco Andre´ , Ferreira Manuel Eduardo , Teixeira Jose´ Carlos
Published: August 2012

The growing costs of conventional energy resources has significantly changed the economies and led to an increased demand for biomass. Biomass in its natural state has a high moisture content, which reduces the combustion efficiency and may cause problems in its processing. One of the most widely used forms of solid biomass concerns pellets that are often manufactured from saw dust. The manufacturing process requires that the raw material should be supplied in controllable conditions of humidity (in the order of 10%, dry basis); otherwise the final product will have poor mechanical properties. So it is essential to do the drying process to reduce the moisture content to acceptable values and to improve the efficiency of using of this product. In this way becomes necessary to study the various parameters that influence the drying process of biomass. For this purpose a drying wind tunnel was built. The facility consists of a ventilator, an electrical heating system and settling chamber and a testing chamber. This facility allows the study of the influence of moisture content and initial grain size of samples and the temperature and air velocity in the drying process of biomass. Air is supplied into a sample of biomass and its temperature and humidity are monitored along time. The humidity is measured by weighting the sample at regular intervals. Measurements were carried out on pine sawdust that was sieved into samples of various particle size. The temperature and air velocity was varied for each sample and the drying kinetics were used to derive working correlations from the experimental data. The results have shown that the gas temperature is the most important parameter in the drying of sawdust. The data was also correlated with dimensionless parameters.
Controller Design to Reduce Mechanical Fatigue in Offshore Wind Turbines Affected by Ice and Tide
Authors: Faley Katherine , Garcia-Sanz Mario
Published: August 2012

This paper presents a novel control structure to mitigate the mechanical fatigue in towers of onshore and offshore wind turbines. A general wind turbine dynamic model for both, (1) onshore and (2) offshore systems with the effects of ice and tide is included. These weather conditions further contribute to the uncertainties in the model, most importantly, in the values of tower equivalent mass, stiffness, and damping and increase the amplitude of the velocity of tip-tower vibrations at some particular frequencies, which creates greater mechanical fatigue. A novel control technique to attenuate such a mechanical fatigue is presented in the paper. It is based on the variation of the generator torque in the above rated wind speed region. The control strategy, designed by using Quantitative Feedback Theory (QFT), decreases the velocity of the nacelle movement due to the wind turbulences, thus reducing the associated mechanical fatigue. The new strategy is validated with a realistic nonlinear simulator under a set of different input scenarios and a Monte Carlo method for the uncertainty selection.
Adaptive Supervisory Control of Superheat Temperature for a Supermarket Refrigeration System
Authors: Kianfar Kaveh , Izadi-Zamanabadi Roozbeh , Saif Mehrdad
Published: August 2012

In this paper an adaptive supervisory controller is designed to control the superheat temperature of a supermarket refrigeration system. The adaptive controller utilizes a switching algorithm with a forgetting factor. At each time step, the switching algorithm selects the best model among multi models using a supervisory monitoring signal. Each model corresponds to a controller; hence the corresponding controller to the selected model generates the required signal to determine the opening degree of an expansion valve. Simulations results of the proposed controller on a model of superheat of a supermarket refrigeration system for different operating point, show very satisfactory performance.