bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Insight of Physical Adsorption for a Single Component Adsorbent+Adsorbate System
Authors: Chakraborty Anutosh , Saha Bidyut Baran , Koyama Shigeru , El-Sharkawy Ibrahim Ibrahim , Ng Kim Choon
Published: May 2009

The thermodynamic property surfaces for a single-component adsorbent + adsorbate system have been derived and developed from the view point of classical thermodynamics. These thermodynamic frameworks enable us to compute the specific heat capacity, partial enthalpy and entropy for the analyses of adsorption processes thoroughly. A theoretical framework for the estimation of the isosteric heat of adsorption between an adsorbate (vapor) and an adsorbent (solid) is also derived for the thermodynamic requirements of chemical equilibrium, Maxwell relations and the entropy of the adsorbed phase. Conventionally, the specific heat capacity of the adsorbate is assumed to correspond to its liquid phase specific heat capacity and more recently to that of its gas phase. We have shown here that the derived specific heat capacity fills up the information gap with respect to the state of adsorbed phase to dispel the confusion as to what is the actual state of the adsorbed phase.
Control of a Nonlinear Boiler-Turbine Unit Using Two Methods: Gain Scheduling and Feedback Linearization
Authors: Moradi H. , Alasty A. , Bakhtiari-Nejad F.
Published: May 2009

To achieve a good performance of a boiler-turbine unit, dynamic variables such as steam pressure, water level of drum and electric output of turbine must be controlled. In this paper a nonlinear model of the boiler-turbine unit is considered in which the inputs are the valve positions of fuel flow, steam control, and feed-water flow. Using two control methods, feedback linearization and gain scheduling, a PI controller is designed. It is shown that by applying both methods, system goes from one operating point to another with an appropriate specification of time response. Results show that system with a controller designed based on gain scheduling method has a better time response from a nominal operating point to a far operating point. In addition, applying any of these control approaches guarantees robustness of the system against the uncertainties associated with dynamic model.
Development and Application of a Two-Scale Non-Linear Reynolds Stress Turbulence Model
Authors: Jaw S. Y. , Hwang R. R.
Published: May 2009

To improve the prediction of turbulent flows, a two-scale, non-linear Reynolds stress turbulence model is proposed in this study. It is known that for the near-wall low-Reynolds number turbulent flows, the Kolmogorov turbulence scale, based on the fluid kinematic viscosity and dissipation rate of turbulent kinetic energy (ν,ε), is the dominant turbulence scale, hence it is adopted to address the viscous effects and the rapid increase of dissipation rate in the near wall region. As a wall is approached, the turbulence scale transits smoothly from turbulent kinetic energy based (k, ε) scale to (ν,ε) scale. The damping functions of the low-Reynolds number models can thus be simplified and the near-wall turbulence characteristics, such as the ε distribution, are correctly reproduced. Furthermore, to improve the prediction of the anisotropic Reynolds stresses for complex flows, a nonlinear algebraic Reynolds stress model is incorporated. The same turbulence scales are adopted in the nonlinear algebraic Reynolds stress model. The developed two-scale non-linear Reynolds stress model is first calibrated with the DNS budgets of two-dimensional channel flows, and then applied to predict the separation flow behind a backward facing step. It is found that the proposed two-scale nonlinear Reynolds stress turbulence model is capable of providing satisfactory results without increasing much computation efforts or causing numerical stability problems.
Transient Forced Convective Heat Transfer: A Review
Authors: Padet Jacques
Published: May 2009

Transient convection is of fundamental interest in many industrial and environmental situations such as air conditioning systems, human comfort in buildings, atmospheric flows, motors, thermal regulation process, cooling of electronic devices, security of energy systems… Many works reported in literature deal with stationary velocity and temperature fields, but only a small number deal with time-variable boundary conditions [1, 2, 3, 4], either in forced, natural or mixed convection.
Hybrid Solution for Developing Laminar Flow in Wavy-Wall Channels via Integral Transforms
Authors: Silva Roseane L. , Santos Carlos A. C. , Quaresma Joa˜o N. N. , Cotta Renato M.
Published: May 2009

The analysis of two-dimensional laminar flow in the entrance region of arbitrarily shaped ducts is undertaken by application of the Generalized Integral Transform Technique (GITT) in the solution of the steady Navier-Stokes equations for incompressible flow. The streamfunction-only formulation is adopted, and a general filtering solution that adapts to the irregular contour is proposed to enhance the convergence behavior of the eigenfunction expansion. The case of a wavy-wall channel is then considered more closely in order to report some numerical results illustrating the expansions convergence behavior. In addition to reporting results of streamfunction, the product of friction factor-Reynolds number is also calculated and compared against results from discrete methods available in the literature for different Reynolds numbers and amplitudes of the wavy channel.
Novel Graphitic Structures by Design
Authors: Phillips Jonathon , Leseman Zayd C. , Cordaro Joseph , Luhrs Claudia , Al-Haik Marwan
Published: May 2009

Graphitic Structures by Design (GSD) is a novel technology for growing graphite in precise patterns from the nano to the macroscale, rapidly (>1 layer/sec), at low temperatures (ca. 500°C), and in a single step using ordinary laboratory equipment. The GSD process consists of exposing particular metals (Ni, Pd, Pt, Co), which act as ‘templates’, to a fuel rich combustion environment. As an example, we have thoroughly characterized graphite growth on nickel in a mixture of ethylene and oxygen (O2/C2H4 ratio<3), and found that it grows in a geometry remarkably consistent with the shape of the metal template at a rate of the order one graphene layer/second at temperatures between about 500 and 700°C. Graphite structures created with GSD to date include two dimensional ‘screens’ that are inches in extent, yet are composed of micron scale squares graphite foam, hollow nanoparticles, and micron scale particles. All alternative technologies for graphite growth require specialty equipment, such as 2000 °C + ovens, and multiple steps. The alternatives are also not suited for a wide variety of pattern growth in either two or three dimensions. We propose to change focus from demonstrating GSD to determination of the mechanism of graphite growth. GSD could meet a number of recognized technological needs for future generation integrated circuits (IC). Precise patterns of oriented graphite are envisioned as: i) replacements of carbon fibers as structural elements in some aerospace and transport applications, ii) as heat conductive pathways aiding thermal management in ICs iii) as electrical conduits in ICs, iv) as the basic elements of nano-scale logic circuits. GSD graphite is arguably superior to the older and more broadly studied carbon nanotubes technology for all these IC applications for many reasons: only GSD be grown in any pattern on any surface, GSD is far cleaner (no metal residue in the graphite structure, in contrast to nanotubes), GSD structures can be formed consistently and cheaply, at low temperature, and only GSD can be readily grown into large designed macrostructures required for some heat transfer applications.
Sensitivity of the Exergy Costs Due to Changes in the Most Relevant Variables of a Diesel Cycle- Based Cogeneration Power Plant
Authors: Betancourth Jairo A. , Rangel Victor H. , Pacheco J. Jesu´s , Herna´ndez Abel , Rubio Jose´ C.
Published: May 2009

This work analyzes the sensitivity of the exergy costs due to variations in the independent variables of a Diesel Cycle-Based Cogeneration Power Plant (DCBCPP). From a diagnosis standpoint, this type of analysis is quite important since it will evaluate the variations of the exergy costs with respect to slight modifications in the inlet operational data. Many papers related to thermoeconomic analysis could be cited, however, there are few articles related to the use of exergy cost theory applied to a DCBCPP. The power plant has 8 internal combustion engines each one generating 11.340 MW. Only three of the engines have a boiler installed which uses the exhaust gases of combustion for steam generation. The other five engines emit the exhaust gases to the environment. In this paper only the exergy costs of the products (electricity and steam) are dealt with, since from a practical point of view they are part of the most important variables of the system.
On Numerical Resolution Requirements in Combustion Modeling
Authors: Al-Khateeb Ashraf N. , Powers Joseph M. , Paolucci Samuel
Published: May 2009

We discuss one-dimensional steady laminar premixed flames in a mixture of calorically imperfect ideal gases described by detailed kinetics and multi-component transport. The required spatial discretization to capture all detailed continuum physics in the reaction zone is determined through use of a robust method developed to rigorously calculate the finest length scale a posteriori. This is accomplished by reformulating the governing equations as a nonlinear system of differential algebraic equations. Then, the solution of the steady reaction zone structure is obtained, and the generalized eigenvalues of the locally linearized system are calculated at each point in the reaction zone. Their reciprocals provide all local length scales. Application of the method to laminar flames reveals that the finest length scale is on the order of 10−4cm. Independent estimates from grid convergence studies on the continuum equations as well as from the underlying molecular collision theory verify the result. This finest length scale is orders of magnitude smaller than common engineering geometric scales, the discretization scales employed in nearly all multi-dimensional and/or unsteady laminar premixed flame simulations in the literature, and the flame thickness.
Strength Assessment of a Pressurized Thick-Walled Cylinder Using Structural-Thermal Coupled Finite Element Analysis
Authors: Feldhacker John , Hu Zhong , Delfanian Fereidoon
Published: May 2009

Upon analysis, thick wall cylinders designed for use in cannon barrel applications experience thermal and mechanical loading very near their fatigue limit. Chief factors in determining the lifetime of a cannon barrel involve internal thermal and mechanical damage caused by projectile firing. The most significant damage experienced in the cannon barrel is surface crack propagation which aids in surface erosion and fatigue failure. Adequate knowledge of these failure phenomena and the ability to predict the lifetime of gun barrels will greatly increase the successful application of their designs. This study will investigate three-dimensional stress of a pressurized thick cylinder using computer simulation based on structural-thermal coupled finite element analysis. The effects of high temperature and high pressure, as well as nonlinear material behavior, on stress-strain distribution during the firing process will be evaluated. This computer-based stress analysis will prove to be a valuable tool for assessing strength and forecasting the lifetime of cannon barrels.
Adaptive H∞ Optimal Control Strategy Based on Nonminimal State Space Realization
Authors: Yucelen Tansel , Pourboghrat Farzad
Published: May 2009

This paper presents a new adaptive H∞ optimal control algorithm for multiple–input multiple–output (MIMO) continuous–time linear systems, based on a new nonminimal state space realization (NSSR), using measured inputs and outputs, without differentation. The proposed methodology combines a recursive Kalman filter (RKF) parameter estimation algorithm, and a gradient-type neural network algorithm to approximate the solution to the algebraic Riccati-Matrix equation (ARME), which is essential to design the H∞ optimal control. Actual hardware experiments using a DSP have been carried out in order to verify the applicability and the performance of the proposed integrated modeling–control method for vibration control of a flexible plate system.
Human Operator Learning on Double-Pendulum Bridge Cranes
Authors: Kim Dooroo , Singhose William
Published: May 2009

Oscillation of crane payloads makes it challenging to manipulate payloads quickly, accurately, and safely. The problem is compounded when the payload creates a double-pendulum effect. This paper evaluates an input-shaping control method for reducing double-pendulum oscillations. Human operator performance testing on a 10-ton industrial bridge crane is used to verify the effectiveness and robustness of the method. The tests required the operators to drive the crane numerous times over a period of eight days. Data from these experiments show that human operators perform manipulation tasks much faster and safer with the proposed control scheme. Furthermore, considerably less operator effort is required when input shaping is used to limit the oscillation. These experiments also show that significant learning occurred when operators did not have the aid of input shaping. However, the performance never approached that achieved with input shaping without any training. With input shaping enabled, only moderate learning occurred because operators were able to drive the crane near its theoretical limit during their first tests.
On the Assembly of Experimental Setups in Virtual Laboratory Environments
Authors: Chang Chenghung P. , Arango Felipe , Esche Sven K. , Chassapis Constantin
Published: May 2009

Recently, the prospects of virtual laboratory environments developed using commercial multi-player computer game engines and their associated software development kits for providing undergraduate engineering and science students with engaging and interactive laboratory experiences have started to be explored. There is a strong potential for such virtual laboratory environments to be readily accepted by today’s students who are accustomed to using advanced communication and entertainment technologies. While online laboratories based on either remotely operated hardware or pure software simulations are often criticized for lacking student interactivity and for being limited to the data collection and result analysis aspects of traditional hands-on laboratories, these shortcomings can be overcome with virtual laboratory environments implemented based on multi-player computer game engines. For instance, game engines allow one to include into the experimental procedure the assembly process of the experimental setups before carrying out any data collection. Furthermore, such virtual laboratory environments can facilitate and even force certain interactions by the students of a laboratory group. This paper discusses recent developments at Stevens Institute of Technology (SIT) that enable students to assemble laboratory equipment inside a virtual laboratory environment implemented using the “Source” game engine (1) and “Source” software development kit (2). In this environment, the students can interactively select and assemble components of laboratory hardware into complete experimental setups, which are subsequently used in experimental procedures. This assembly process can be performed in a cooperative fashion with multiple students collaboratively interacting with each other as well as with the experimental equipment. Such game-based educational tools are expected to find applications for teaching and training in a wide array of fields.
Agent-Based Approach in Roadway Traffic and Transportation Systems: State of the Art
Authors: Chen Bo , Cheng Harry H. , Palen Joe
Published: May 2009

Agent technology is rapidly emerging as one of the powerful technologies for the development of large-scale distributed systems to deal with the uncertainty in a dynamic environment. The domain of traffic and transportation systems is well suited for an agent-based approach because systems are usually geographically distributed in dynamic changing environments. Our literature survey shows that the techniques and methods resulted from the field of agent and multi-agent systems have been applied to many aspects of traffic and transportation systems, including modeling and simulation, dynamic routing and congestion management, intelligent traffic management, and urban traffic signal control. This paper examines agent-based approach and its applications in roadway traffic and transportation systems, and discusses several future research directions towards successful deployment of agent technology in traffic and transportation systems.
Vortex Detection and Characterization in Low Reynolds Number Separation
Authors: Morse Daniel R. , Liburdy James A.
Published: May 2009

This study focuses on the detection and characterization of vortices in low Reynolds number separation flow over the elliptical leading edge of a flat plate airfoil. Velocity fields were obtained using Time Resolved Particle Image Velocimetry (TRPIV). The Reynolds number based on chord length ranged from 14,700 to 66,700. Experiments were performed for velocities of 1.1, 2.0 and 5.0 m/s and angles of attack of 14°, 16°, 18° and 20°. These velocities correspond to chord length Reynolds numbers of 1.47×104, 2.68×104, and 6.70×104, respectively. A local swirl calculation was used to determine regions of high circulation, and the convection of the centers of these regions was used to determine convective velocities of these vortical structures. The streamwise convective velocity normalized by the freestream velocity is observed to range from approximately 0.4 to 0.65 over the range of angles of attack, with slightly increasing values as the angle of attack increases.
Incorporating Rapid Prototyping Machine in Teaching Mechanical Engineering Design
Authors: Trabia Mohamed B. , Nelson Kevin
Published: May 2009

There is a trend toward increasing exposure of students to hands-on experience in mechanical engineering design courses as these courses are usually limited to generating calculations and drawings of mechanical designs. Students in these courses may lack the ability to visualize and create the physical objects that correspond to their calculations. This limitation may negatively affect students, especially those with limited hands-on experience. To address this issue, the Department of Mechanical Engineering, University of Nevada, Las Vegas (UNLV) started requiring students to create their design using a rapid prototyping machine as a part of the Mechanical Engineering Design Course (ME 440). Students in this course work in teams to create projects starting from abstract statements. They are required to use their calculations as a means to create solid models of the components of their designs and print them on the rapid prototyping machine. Such an approach results in a better understanding of the functionalities of components as well as fit and tolerance issues. Student feedback is used as well as future venues for improving the course.
Using MATLAB to Enhance Engineering Students’ Analytical Problem-Solving Skills
Authors: Cai Liang-Wu
Published: May 2009

Symbolic analysis is one of the most feared tasks for many undergraduate students in engineering disciplines. Students argue that, without numerical values, it is difficult to make a sense out of a long expression. Instructors have experienced that students are diffident in such analyses; and they quickly lose interest in the topic. This trend has been enhanced with more prevalent use of computers in engineering curricula in recent years. In the senior level Mechanical Vibrations course, this author has experimented with an innovative procedure of using mathematical software such as MATLAB to enhance the students’ learning experience with extensive symbolic calculations. In this experiment, MATLAB is used as a rudimentary plotting device that allows students to plot curves. The procedure provides students a systematical approach to produce parametric plots from an analytical expression, and to validate the expression on physical grounds. This innovative procedure has changed students’ perception about long expressions, decreased their fear, and boosted their confidence in their analytical skills. All these help student to develop a more positive altitude towards symbolic analyses.
An Evaluation of Encapsulated Oil Flooded Screw Compressor Systems
Authors: Stosic Nikola , Kovacevic Ahmed , Smith Ian K. , Mujic Elvedin
Published: May 2009

A study was carried out on oil injected compressors, to assess the value of compressor encapsulation in optimization of the compressor system and eliminating the need for an external oil separator. The analysis was performed using a proprietary software suite for estimating the performance and optimising the design of a screw compressor, when it is subjected to a higher environment temperature, due to its containment in the oil separator. Several features were further investigated by use of 3-D computational fluid dynamics. It was found that full encapsulation seriously worsens compressor performance. Accordingly it should be adopted only when justified by special circumstances. However, the semi-encapsulated compressors behave similarly to bare air ends. Thus, where they are cost effective, their adoption is to be encouraged.
Sliding Mode Control of the Turning Process for Eliminating Regenerative Chatter in the Presence of Paremetric Uncertainties
Authors: Moradi H. , Movahhedy M. R. , Vosoughi G. R.
Published: May 2009

Chatter suppression is an important topic in any type of machining process. In this paper, orthogonal cutting process is modeled as a single degree of freedom dynamic system. A nonlinear delay differential equation is presented that models flank wear of the tool. Uncertainties in cutting velocity, tool wear size and parameters of the dynamic model are included in the model of cutting process. The force provided by a piezo-actuator is taken as the control input of the system. A sliding mode control scheme is used and an effective control law is derived which suppresses the chatter vibration. Results for two distinct cases of a sharp tool and a worn tool are presented and compared which shows the effectiveness of approach.
Ultra Low Cycle Fatigue of Axisymmetric Freestanding Nanoscale Gold Films
Authors: Abbas Khawar , Leseman Zayd C. , Mackin Thomas J.
Published: May 2009

We present ultra low-cycle fatigue experiments of axisymmetric nano-crystalline gold films of nano-thickness deformed by a spherical indenter using a recently developed freestanding membrane test. Freestanding membranes of gold were centrally deflected using a spherical indenter attached to a MEMS load cell. Fabrication of the films for these experiments yielded films 100 nm thick and 500 μm in diameter. We observed that the plastically deformed thin films recover completely in time at room temperature. One particular film was loaded 4 consecutive times, with the fourth loading leading to its fracture after full recovery from the three prior loadings. Observation of this phenomenon directed us to term this behavior “Ultra Low cycle fatigue”.
Fractional Optimal Control of Distributed Systems
Authors: Tangpong X. W. , Agrawal Om P.
Published: May 2009

This paper presents a formulation and a numerical scheme for Fractional Optimal Control (FOC) for a class of distributed systems. The fractional derivative is defined in the Caputo sense. The performance index of a Fractional Optimal Control Problem (FOCP) is considered as a function of both the state and the control variables, and the dynamic constraints are expressed by a Partial Fractional Differential Equation (PFDE). The scheme presented rely on reducing the equations for distributed system into a set of equations that have no space parameter. Several strategies are pointed out for this task, and one of them is discussed in detail. This involves discretizing the space domain into several segments, and writing the spatial derivatives in terms of variables at space node points. The Calculus of Variations, the Lagrange multiplier, and the formula for fractional integration by parts are used to obtain Euler-Lagrange equations for the problem. The numerical technique presented in [1] for scalar case is extended for the vector case. In this technique, the FOC equations are reduced to Volterra type integral equations. The time domain is also descretized into several segments. For the linear case, the numerical technique results into a set of algebraic equations which can be solved using a direct or an iterative scheme. The problem is solved for various order of fractional derivatives and various order of space and time discretizations. Numerical results show that for the problem considered, only a few space grid points are sufficient to obtain good results, and the solutions converge as the size of the time step is reduced. The formulation presented is simple and can be extended to FOC of other distributed systems.
A New Active Hydrodynamic Bearing for Controlling Flow-Induced Instability
Authors: Gao F. , de Queiroz M. S. , Cai Z.
Published: May 2009

Fluid-film bearings can suffer from flow-induced instabilities known as ‘whirl’ and ‘whip.’ This phenomenon can lead to large rotor vibration and eventually result in rotor-bearing failure. In this paper, we introduce a new active hydrodynamic bearing to mitigate such instabilities. The system contains a rotating bushing, actuated by a motor, that serves as the control input. This input is used to control the mean flow velocity in the bearing and thereby the journal vibration. A simple feedback control law is proposed for the bushing velocity, and numerical simulations are presented to evaluate the active bearing.
Modeling and Experimental Study of a Biology-Inspired Directional Microphone
Authors: Chen Z. , Lacher A. , Yu M.
Published: May 2009

In this paper, a novel design of a biology-inspired directional microphone is presented. This microphone consists of two clamped circular diaphragms, which are mechanically coupled by a connecting bridge that is pivoted at its center. A mechanics based model is constructed to determine the response of the proposed directional microphone to sound incident from an arbitrary direction. The simulation results show that the proposed biology-inspired miniature directional microphone provides a remarkable amplification of the time delay associated with the sound induced diaphragm responses. Different parameters such as coupling bridge stiffness and damping factor are studied to evaluate the performance of the directional microphone. Preliminary experimental results are presented and compared with model predictions. The analyses and results are expected to be helpful for realizing an optimal version of the biology-inspired miniature directional microphone with high accuracy and localization capability for various applications.
Fluid Mixing in Channels With Microridges
Authors: Xia Zheng , Cattafesta Lou , Sheplak Mark , Mei Renwei , Fan Z. Hugh
Published: May 2009

Microflows in complex channels with uneven surface often display unusual flow behavior compared to their macroscale counterparts. Channels with micro ridges are created in a plastic device using photolithography and molding. Recirculation is reported in the flow in these ridged channels [1]. We use recirculation to enhance fluid mixing and the utility is demonstrated by homogenizing fluorescein and water in the microchannels. In addition, deconvolution microscopy is developed to visualize the fluid flow in the ridged channel. Flow twisting, as expected, results in enhanced fluid mixing; the fluorescence intensity at a cross section is calculated as an indicator of the degree of mixing. The preliminary results show rapid mixing in the ridged channels, verifying existence of circulation. We also compared the experimental results with that from computational fluid dynamics simulation.
A Novel Contamination Free Two Temperature Continuous Flow Polymerase Chain Reactor
Authors: Sayers Michael B. , Dalton Tara M.
Published: May 2009

Polymerase Chain Reaction (PCR) is an enzymatic process that has dramatically advanced many fields of life sciences, where it is an indispensable tool in a burgeoning range of applications, including diagnostic medicine, molecular biology, forensics and food testing. Recent increased demand for extremely high throughput PCR systems has led to the development of miniaturised continuous flow microfluidic PCR devices, which may have extremely high throughput compared to standard commercial PCR thermal cyclers. A novel continuous flow microfluidic PCR device has been designed and fabricated, consisting of two thermal zones maintained on aluminium thermal blocks providing the precise temperatures required for denaturation and annealing/extension. Polycarbonate sideplates retain the denaturation thermal block vertically above the annealing/extension thermal block while allowing for a variable air gap to be maintained between them. Heating of the denaturation thermal block is achieved using a Labview controlled Thermofoil heater, while the annealing/extension thermal block is maintained at temperature by optimised heat transfer from the denaturation block. Flow-through capillary tubing is positioned into a grooved serpentine channel machined into these thermal blocks. This serpentine channel passes through each thermal block fifty times, providing fifty PCR thermal cycles. Contamination free high throughput continuous flow PCR necessitates that the samples be encapsulated in an immiscible carrier fluid to eradicate cross contamination between samples and suppress the likelihood of the sample contacting the capillary leading to sample degradation. Encapsulation of the PCR reaction mixture is achieved upstream of the thermal cycler through segmentation of the sample into droplets entrained within an immiscible carrier fluid, which are then cycled through the thermal cycler. High throughput DNA amplification of two genes, GAPDH and LEF1, from the REH cell line has been successfully demonstrated on this microfluidic platform without any detectable contamination between samples. The PCR droplet reactors were approximately 250nl which is two orders of magnitude less than the standard sample size for most commercial PCR thermal cyclers.
A Real-Time Continuous Flow Polymerase Chain Reactor for DNA Expression Quantification
Authors: Sayers Michael B. , Dalton Tara M.
Published: May 2009

Real-time quantitative Polymerase Chain Reaction (PCR) is an extremely sensitive and reliable method for quantifying gene expression, allowing subtle shifts in gene expression to be easily monitored. Currently, stationary real-time PCR is readily achieved using fluorescent labels which increase in fluorescence as the DNA is exponentially amplified. Quantitative PCR is used in a myriad of applications. However currently most commercial real-time PCR devices are batch process stationary well based systems, limiting their throughput. Continuous flow microfluidic PCR devices have allowed for advancement in terms of improved PCR throughput and reduced reagent usage. As part of an overall total analysis system a device integrating all the functional steps of continuous flow realtime quantitative PCR has been designed and fabricated. Initially the PCR reaction mixture is segmented into nano-litre PCR reactors which are then thermally cycled on a two temperature fifty cycle flow-through PCR device, which allows laser induced fluorescent imaging of the nanoreactors. Previous studies into continuous flow PCR have demonstrated endpoint fluorescent measurements, however this research allows PCR nanoreactors to be fluorescently monitored after every PCR thermal cycle. Fluorescent optical monitoring is achieved through laser excitation of the nanoreactors while a Charged Coupled Device (CCD) camera is used to record the fluorescent emissions from the nanoreactors. Intensity analysis of the recorded images is then preformed using MATLAB to accurately determine the fluorescence intensity level, thereby allowing real-time quantitative amplification curves to be generated. This has major advantages over existing continuous flow PCR devices which use endpoint fluorescence and capillary electrophoresis, as the amplification curves allow far more information to be gleaned and allow the initial DNA template concentration to be accurately determined.
Experimental Investigation on PTFE Composites for Journal Bearings
Authors: Jayaraj V. , Srinivasan K.
Published: May 2009

Journal bearings are widely used in many industrial applications. In journal bearings, under boundary lubricated conditions, the surfaces are considered to be technically dry or only slightly lubricated, so that the resistance to relative motion is due to the interaction between the highest asperities covered by the boundary film. A thin film of lubricating oil exists under this condition and there is partial metal to metal contact. The ideal situation where the two sliding surfaces are completely separated by a thin film of a viscous fluid or a gas is referred to as hydrodynamic lubrication. In hydrodynamic bearings, due to frequent starting and stopping, misalignment of the shaft with the bearing, application of heavy loads and unexpected sudden non flow of lubricant and such other service conditions result in boundary lubrication by squeezing out the lubricating film or allow the surface asperities to break through the film so that the shaft and bearing are pressed into contact with one another. The maximum wear occurs in fluid film bearings during boundary lubricated conditions. The use of dry bearings has therefore become more essential as it requires practically no lubricant to function. Moreover it is less expensive, resist contamination better compared to rolling element bearings and easier to design.
Optimum Operation of a Prototypical Pyroelectric Energy Converter for Harvesting Waste Heat
Authors: Vanderpool Damien , Pilon Laurent
Published: May 2009

This paper is concerned with direct energy conversion of waste heat into electricity using pyroelectric materials. The pyroelectric effect refers to the flow of charges to or from the surface of a material upon heating or cooling. The present study investigates the design and operation of a pyroelectric converter assembly based on the Olsen cycle using multistage pyroelectric elements and heat regeneration. Cooling and heating cycles of the pyroelectric elements are achieved by oscillating the working fluid between hot and cold sources under laminar flow conditions. Multistaging consists of placing different pyroelectric elements in series with increasing Curie temperatures from the cold to the hot sources. Moreover, the heat required to increase the temperature of the lattice is regenerated back and forth between the working fluid and the pyroelectric elements instead of being lost to the heat sink. A prototypical pyroelectric converter is simulated by solving the two-dimensional mass, momentum, and energy equations using finite element methods. The pumping power and the heat transfer rate required for the cycle as well as the electrical power generated are estimated from the computed pressure, temperature, and velocity. Finally, the overall thermodynamic efficiency of the system is calculated and compared with reported experimental data.
Nonlinear Deflection Model for Corner-Supported, Thin Laminates Shape-Controlled With Moment Actuators
Authors: Massad Jordan E. , Chaplya Pavel M. , Martin Jeffrey W. , Reu Philip L. , Sumali Hartono
Published: May 2009

The shape control of thin, flexible structures has been studied primarily for edge-supported thin-plates. For applications such as electromagnetic wave reflectors, corner-supported configurations may prove more applicable since they allow for greater flexibility and larger achievable deflections when compared to edge-supported geometries under similar actuation conditions. Models of such structures provide insight for effective, realizable designs, enable design optimization, and provide a means of active shape control. Models for small deformations of corner-supported, thin laminates actuated by integrated piezoelectric actuators have been developed. However, membrane deflections expected for nominal actuation exceed those stipulated by linear, small deflection theories. In addition, large deflection models have been developed for membranes; however these models are not formulated for shape control. This paper extends a previously-developed linear model for a corner-supported thin, rectangular laminate to a more general large deflection model for a clamped-corner laminate composed of moment actuators and an array of actuating electrodes. First, a nonlinear model determining the deflected shape of a laminate given a distribution of actuation voltages is derived. Second, a technique is employed to formulate the model as a map between input voltage and deflection alone, making it suitable for shape control. Finally, comparisons of simulated deflections with measured deflections of a fabricated active laminate are investigated.
On-Chip Isothermal Polymerase Chain Reaction
Authors: Persat Alexandre , Morita Tomoyuki , Santiago Juan G.
Published: May 2009

We present a novel technique for on-chip PCR where temperature is held constant and uniform in the reactor. Specific chemicals, known as denaturants, have the ability to melt DNA. A flow control scheme establishes spatio-temporal fluctuations in the concentration of denaturants along a microchannel, while electromigration drives DNA through this spatially varying denaturant concentration field. Preliminary results show denaturation and extension of a 200 base pairs (bp) DNA template.
Visualizing Cold-Flow Fluidized Beds With X-Rays
Authors: Franka Nathan P. , Heindel Theodore J. , Battaglia Francine
Published: May 2009

Glass beads or sand particles are typically used as bed materials in fluidized beds due to their high sphericity, uniform properties, and resistance to breaking. X-ray imaging can be used to visualize these complex flows. Glass attenuates X-rays much more than the surrounding air and, consequently, the images may be nearly saturated in order to resolve the internal flow of a large diameter bed. This paper focuses on the use of alternative bed materials to increase X-ray penetration and resolution to enhance flow visualization in a 9.5 cm diameter fluidized bed. Melamine plastic, ground walnut shell, and ground corncob particles are qualitatively compared to glass beads using X-ray computer tomography (CT) imaging and X-ray radiography. The various beds are compared at three different flow rates and the ratio of superficial gas velocity to minimum fluidization velocity is constant for each bed material. X-ray CT imaging is used to provide a qualitative view of the local time-averaged solids concentration, and clearly shows differences in fluidization between the materials. Channeling is shown in melamine, walnut shells and corncob at low flow rates, however, the beds fluidize more uniformly as gas flow rate increases. In all cases, glass beads fluidize most uniformly and flow rate does not significantly affect fluidization uniformity. Radiographic movies confirm that visualizing internal flow structures of the glass bed is much more difficult than for other materials.
Rigid Formation Control of Nonholonomic Multi-Agents
Authors: Maithripala D. H. A. , Woo Sangbum , Jayasuriya S.
Published: May 2009

In this paper we address the formation control problem of maintaining rigid formation for a group of nonholonomic mobile agents. Explicit consideration of actuator limits at a higher level of control in designing formation trajectories that can theoretically result in zero formation error is the main contribution we make. In particular we consider a positive lower bound on the agent speed, to account for stall speeds of fixed winged UAVs. We provide sufficient conditions on the controls that would ensure feasible formation trajectories. The approach we propose is supported with preliminary simulation results.
Chaos in Healthy Ball Bearings
Authors: Ghafari Shahab H. , Abdel-Rahman Eihab M. , Golnaraghi Farid , Ismail Fathy
Published: May 2009

This paper explores the effect of internal clearance on vibration characteristics of ball bearings. It is found that a fault-free bearing exhibits periodic vibration within a small range of internal clearance. However for larger values of internal clearance and large amplitude excitations, fault-free bearings exhibit chaotic behavior.
Cellular Automata Based Model for Droplet Spreading Process
Authors: Bezirganyan R. , Mohanty P. , Zakarian A. , Li B. , Sengupta S.
Published: May 2009

In this work Cellular Automata (CA) based droplet Spreading Process (SP) has been investigated. The core of the model is represented by CA based SP algorithm which implements one of the major features of fluid flow, i.e., mass conservation. We show that one input parameter (α) is sufficient for this algorithm to handle variety of droplet diameters, splat shapes, and target surfaces that the droplets impact. Further, we demonstrate constructal alternatives for viscosity and surface tension, which are scales of CA grid layers (s) and splat surface curvature (γ), respectively. We show that bigger s prevents the droplet from penetrating deep into the target surface crevices, and further variation of γ results in the desired surface tension effect. Calibration of the model is carried out using scaling relations, namely α = α(Re), where Re is the Reynolds number. Results obtained in this work showed good compliance with the experimental measurements found in the literature as well as the constructal theory of droplet impact geometry.
Interfacial Heat Transfer During Droplet Impact on a Solid Surface: Comparison of High-Resolution Laser Measurements With Finite-Element Simulations
Authors: Bhardwaj Rajneesh , Longtin Jon P. , Attinger Daniel
Published: May 2009

The objective of this work is to understand the coupling of fluid dynamics and heat transfer during the impact of a millimeter-size water droplet on a flat, solid glass substrate. In this work, a finite-element model is presented which simulates the transient fluid dynamics and heat transfer during the droplet deposition process, considering Laplace forces on the liquid-gas boundary, and the dynamics of wetting. A novel, experimental laser-based method is used to measure temperatures at the solid-liquid interface. This method is based on a thermoreflectance technique and provides unprecedented temporal and spatial resolutions of 1 microsecond and 20 micrometer, respectively. Matching between simulations, temperature measurements and high-speed visualization allows the determination of the interfacial heat transfer coefficient.
A Numerical Model for the Evaporation of a Nanoliter Droplet on a Solid, Heated Substrate
Authors: Bhardwaj Rajneesh , Attinger Daniel
Published: May 2009

A finite-element numerical model is developed to study the evaporation of a sessile nanoliter droplet on a flat substrate in the isothermal and non-isothermal case. All equations are expressed in a Lagrangian framework, which provides accurate modeling of the free surface motion and the associated Laplace stresses. The evaporative flux at the free surface is defined as a function of the drop geometry and thermodynamic conditions. The boundary conditions at free surface are the mass and energy jump conditions. Results for fluid dynamics, evaporation time and evaporative flux are described for substrate temperature levels of 27°C (ambient), 82°C and 122°C. Comparisons with experiments are made, in terms of the evolution of volume, wetting angle and wetted radius.
Photobiological Hydrogen Production in a Flat Panel Photobioreactor Using Different Nutrient Media
Authors: Berberoglu Halil , Pilon Laurent , Jay Jenny
Published: May 2009

This study reports a factor 5.5 increase in hydrogen production of Anabaena variabilis ATCC 29413 using Allen-Arnon medium compared with BG-11 and BG-110 media. The results were obtained with a flat panel photobioreactor made of acrylic and operated in two stages at 30°C. Stage 1 aims at converting carbon dioxide into biomass by photosynthesis while Stage 2 aims at producing hydrogen. During Stage 1, the photobioreactor is irradiated with 65 μmol/m2/s of light and sparged with a mixture of air and carbon dioxide. During Stage 2, irradiance is increased to 150 μmol/m2/s and the photobioreactor is sparged with pure argon. The parameters continuously monitored are (1) the cyanobacteria concentration, (2) the pH, (3) the dissolved oxygen concentration, (4) the nitrate and (5) the ammonia concentrations in the medium, and (6) the hydrogen concentration in the effluent gas. The three media BG-11, BG-110, and Allen-Arnon are tested under otherwise similar conditions. The light to biomass energy conversion efficiency varied between 5.5 and 10.5% and was similar for all media. The cyanobacteria concentrations during Stage 2 were 1.10 and 1.17 kg dry cell/m3 with BG-11 and Allen-Arnon media, respectively, while it could not exceed 0.76 kg dry cell/m3 with medium BG-110. The average specific hydrogen production rates were about 1 and 0.9 L/kg dry cell/h in media BG-11 and BG-110, respectively. In contrast, it was about 5.6 L/kg dry cell/h in Allen-Arnon medium. The maximum light to hydrogen energy conversion efficiencies achieved were 0.26%, 0.16%, and 1.32% for BG-11, BG-110, and Allen-Arnon media, respectively. The larger specific hydrogen production rates, efficiencies, and cyanobacteria concentrations achieved using Allen-Arnon medium are attributed to the presence of vanadium, and higher concentrations of molybdenum, magnesium, calcium, sodium, and potassium in the medium.
Computational Modeling of Biomass in a Fluidized Bed Gasifier
Authors: Deza Mirka , Battaglia Francine , Heindel Theodore J.
Published: May 2009

Computational modeling of fluidized beds can be used to predict operation of biomass gasifiers after extensive validation with experimental data. The present work will focus on computational simulations of a fluidized bed gasifier with a multifluid Eulerian-Eulerian model to represent the gas and solid phases as interpenetrating continua. The simulations described in this paper will model cold-flow fluidized bed experiments, and consider factors such as particle sphericity, coefficient of restitution, and drag coefficient calibration. Hydrodynamic results from the simulations will be qualitatively compared with X-ray flow visualization studies of a similar bed.
Nanoscale Joule Heating Along Silicon Nanowire and Its Nanoscale Heater Application
Authors: Park Inkyu , Li Zhiyong , Pisano Albert P. , Williams R. Stanley
Published: May 2009

In this paper, we present numerical and experimental studies on the nanoscale Joule heating along the single crystalline silicon nanowires. 50–100nm wide single crystalline silicon nanowires are heated via Joule heating by applying an electrical potential across them. Numerical simulation result predicts an extremely localized temperature field by resistive heating of silicon nanowire. We experimentally verified this highly localized heating of silicon nanowires by AFM imaging of localized thermal ablation of polytetrafluoroethylene (PTFE) thin film. This result implies potential applications of silicon nanowires as nanoscale heaters for the generation of highly localized temperature fields.