bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Objective Parameterization of Graphite Heat Spreader for Portable Systems Applications
Authors: Banerjee Arijit , Lakhkar Nikhil , Riaz Shahi , Refai-Ahmed Gamal , Agonafer Dereje
Published: May 2009

The advancement made in portable electronic systems has primarily been due to miniaturization of electronic systems. This in turn leads to an increase in power density which leads to higher temperatures and formation of hot spots. There is a temperature specification of system surfaces for human comfort (such as the surface close to a keyboard on laptops). Challenge in cooling portable devices is that there is not enough room to accommodate heat sinks. It is therefore important to have heat spreaders that can transfer the heat from critical devices to regions where cooling is available. Traditionally, copper has been the best heat spreader due to its high thermal conductivity. However, copper has a relatively high density and correspondingly high weight. Graphite is a suitable alternative. Recent advances in graphite technology have resulted in fairly high conductivity in the planar directions. In spite of these advances, the cost of graphite is an issue. In this paper, a multi-objective parameterization is utilized that considers weight and temperature distribution of the graphite heat spreader as objective parameters. The data is then compared to published data that utilizes graphite in a laptop.
Micro Particle Transport and Deposition in Human Upper Airways
Authors: Chen Jim S. , Kim Jinho
Published: May 2009

The hazard caused by inhaled particles depends on the site at which they deposit within the respiratory system. Knowledge of respiratory aerosol deposition rates and locations is necessary to (1) evaluate potential health effects and establish critical exposure limits and (2) design effective inhaled medications that target specific lung regions. Particles smaller than 10 μm in diameter can be breathed into lungs and are known as inhalable particles, while most of larger particles settle in mouth and nose. Inhalable particles settle in different regions of the lungs and the settling regions depends on the particle size. The motion of a particle is mainly affected by the inertia of the particle and by the particle’s aerodynamic drag. The most important dimensionless parameters in the prediction of particle motion are the flow Reynolds number and the Stoke number, which combines the effects of particle diameter, particle density, shape factor and slip factor. The purpose of this study is to investigate the airflows in human respiratory airways. The influence of particle size on transport and deposition patterns in the 3-D lung model of the human airways is the primary concern of this research. The lung model developed for this research extends from the trachea to the segmental bronchi and it is based on Weibel’s model. The velocity field of air is studied and particle transport and deposition are compared for particles in the diameter range of 1 μm – 100 μm (G0 to G2) and 0.1 μm – 10 μm (G3 to G5) at airflow rates of 6.0, 16.7, and 30.0 L/min, which represent breathing at rest, light activity, and heavy activity, respectively. The investigation is carried out by computational fluid dynamics (CFD) using the software Fluent 6.2. Three-dimensional, steady, incompressible, laminar flow is simulated to obtain the flow field. The discrete phase model (DPM) is then employed to predict the particle trajectories and the deposition efficiency by considering drag and gravity forces. In the present study, the Reynolds number in the range of 200 – 2000 and the Stoke number in the range of 10−5 – 0.12 are investigated. For particle size over 10 μm, deposition mainly occurs by inertial impaction, where deposition generally increases with increases in particle size and flow rate. Most of the larger micron sized particles are captured at the bifurcations, while submicron sized particles flow with the fluid into the lung lower airways. The trajectories of submicron sized particles are strongly influenced by the secondary flow in daughter branches. The present results of particle deposition efficiency in the human upper airways compared well with data in the literature.
PB-Free Wave Soldering of Thick Printed Circuit Boards Using No-Clean VOC Free Flux
Authors: Mukherjee Shantanu , Castro Manuel , Tsai Pei-Fang Jennifer , Srihari Krishnaswami , Nguyen Van D.
Published: May 2009

There has been an increasing focus on surface mount technology, and the miniaturization of electronic assemblies. However, wave soldering still remains an integral part of the Printed Circuit Board (PCB) assembly process. Hole fill is an important aspect in wave soldering. It is caused by the capillary action of molten alloys, as the PCB traverses across the molten wave. The advent of Pb-free materials has tightened the process windows for wave soldering. This is primarily because Pb-free alloys have higher melting points. One way to enhance hole filling action is to increase the operating temperatures of the molten wave. This step, however, could result in the disintegration of surface mount or through hole devices, board discoloration and warpage. Flux selection is an important process step for Pb-free wave soldering as it enhances hole-fill and cleans the soldering surface of the oxides prior to the PCB hitting the wave. It is critical to use the ‘optimal’ flux in Pb-free wave soldering processes. The objective of this study is to determine the ‘best’ flux for the Pb-free wave soldering of 2.16mm (0.085″) thick PCBs with Ni/Au surface finish. The Pb-free solder in this application is SAC387 (95.5%Sn, 3.8%Ag, and 0.7% Cu) with VOC-free no clean water based flux. Under different conveyor speeds, the experimentation evaluates the ‘best’ flux among three candidates. Complete (100%) inspection using X-ray laminography equipment detects the percentage of hole fill and other defects such as bridging, flux residue, and solder balling. The ‘best’ flux should have the least number of defects.
Time Evoultion of Entropy in a System Comprised of a Boltzmann Type Gas: An Application of the Beretta Equation of Motion
Authors: Smith Charles E. , von Spakovsky Michael R.
Published: May 2009

Basing his work on a new formulation of thermodynamics called the Unified Quantum Theory of Mechanics and Thermodynamics first published in a series of four ground breaking papers in 1976 (Hatsopoulos and Gyftopoulos, 1976a, b, c, d), Beretta develops a dynamical postulate (Beretta et al. 1984; Beretta, Gyftopoulos, and Park, 1985) consistent both with the non-dynamical quantum mechanical postulates of the Unified Theory as well as with its thermodynamic ones (the 2nd Law in particular). The theory itself simply and elegantly extends in a unified fashion the concepts of thermodynamics to quantum mechanics and the concepts of quantum mechanics to thermodynamics. It does so without the bridge traditionally used, i.e. statistical mechanics, eliminating a number of the ambiguities, tautologies, and inconsistencies (including a built-in violation of the 2nd Law) inherent in the presentations of both Classical and Statistical Thermodynamics. This new formulation generalizes thermodynamics so that it applies to all systems large or small (including one particle systems) either in a state of thermodynamic (i.e. stable) equilibrium or not in a state of thermodynamic equilibrium. The Beretta equation of motion describes the time evolution of the state of a system via a density operator which is uniquely based on an unambiguous preparation of an ensemble of identical systems, i.e. the so-called homogenous or irreducible ensemble, and does so both for unitary and non-unitary reversible as well as irreversible processes. In this paper, we present a simple application of this general equation of motion to the time evolution of the entropy of a closed system comprised of a Boltzmann type gas consisting of one or of many particles undergoing an irreversible process. A number of different energy eigenlevels and initial states and their effects on entropy generation and the final state of maximum entropy, i.e. stable equilibrium, are examined. A simple time-dependent work interaction is introduced into the formulation to show how this in turn affects the evolution of the state of the system.
A Tunable Vibration Absorber Design to Suppress Chatter in Boring Manufacturing Process
Authors: Moradi H. , Bakhtiari-Nejad F. , Movahhedi M. R.
Published: May 2009

Dynamic vibration absorbers are used to reduce the undesirable vibrations in many applications such as electrical transmission lines, helicopters, gas turbines, engines, bridges and etc. One type of these absorbers is tunable vibration absorber (TVA) which can act as a semi-active controller. In this paper, by applying a (TVA), chatter vibration is suppressed during boring process in which boring bar is modeled as a cantilever Euler-Bernoulli beam. The optimum specifications of absorber such as spring stiffness, absorber mass and its position can be determined by developing an algorithm based upon mode summation method. Finally, using the SIMULINK Toolbox of MATLAB, the analog simulated block diagram of the problem is developed. The advantage of this simulation is that, one can analyze the effect of other types of excitations such as step, ramp, etc on the absorbed system.
Numerical Investigation of the Validity of Axial Blade Design
Authors: Pascu Maria , Epple Philipp
Published: May 2009

The core of the present work is an axial blade design procedure which stands as premises for an optimization tool for axial fans. The initial design assumptions made refer to the computation of the blade angles and the determination of the blade shape. The back-bone of the present work is a design solver which computes inversely the blade shape, based on the assumption that the angle distribution between the inlet and the outlet blade angles is parabolic. The flow-optimized blade shape of an established industrial fan, used in engine-cooling applications, was derived using this design solver. Intensive numerical investigations were carried out for both the industrial and the optimized impellers, and an appropriate performance indicator had to be found. The static-to-total efficiency is an accurate performance indicator and when computing it for both impellers, it was noticed that the optimized blade impeller performs better and a 24% difference in the efficiency curves was observed. Also, by computing the total-to-total efficiency curves, the optimized blade performed better and a 13% difference between the two impellers was found.
Computational Modeling for a Microchannel Electronics Cooler
Authors: Dix Joseph , Jokar Amir , Martinsen Robert
Published: May 2009

The objective of this study is to analyze the single-phase fluid flow and heat transfer through a microchannel electronics cooler with a hydraulic diameter of about 300 microns. For this purpose, commercial computational fluid dynamics software was used to first characterize the existing design that uses purified water as coolant fluid. The flow parameters of the cooler were then adjusted in order to optimize the design. Geometry modifications were used next to enhance heat transfer, and to reduce pressure drop and erosion from possible impurities in the working fluid. Different working fluids were also considered to investigate possible reductions in corrosion and further increases in heat transfer. Alternative combinations of boundary and operating conditions were explored during optimization. The results of this study showed the microchannel cooler had capacity in rejecting more thermal energy with less pressure drop through flow optimization and geometry modification.
Effect of Tracking Flat Reflector Using Novel Auxiliary Drive Mechanism on the Performance of Stationary Photovoltaic Module
Authors: Kulkarni Sudhir , Tonapi Saurabh , Larochelle Pierre , Mitra Kunal
Published: May 2009

General ways of cost reduction in solar power generation are Solar Tracked Photovoltaic (PV) arrays and concentrator systems. The PV array tracking becomes infeasible with increase in the size of the array and concentrated system is ineffective for continuous power generation as it requires external cooling system. Proposed approach here is to employ a novel auxiliary mirror drive mechanism to track the sun and reflect the rays on to stationary PV arrays. The performance is compared with same PV module without reflector under the same environmental conditions. Solarex SX 38 PV module and cleardome solar reflector (96% reflectivity) are used for the experiments. PV module is connected to electrical load through Maximum Power Point Tracker (MPPT) and data acquisition system for voltage and current measurements. Incident radiation is measured using Li-Cor pyranometers located on the plane of the module and horizontal plane. A shadow band device is used for the measurement of diffuse solar radiation. The PV module is placed facing south at a tilt angle equal to the latitude angle. A reflector is placed facing north and oriented using the novel Mirror Positioning Device (MPD). The MPD is a five bar spherical mechanism used for solar tracking. This mechanism has two degrees of freedom which allows for tracking the sun along its azimuth and altitude. The mechanism is driven by two servo motors which actuate two links. The actuated link 1 helps in achieving the altitude gained by the sun while the actuated link 2 helps to attain the azimuth (or horizontal movement). The reason for using a spherical mechanism is due to the virtue of its architecture; it allows for carrying a larger payload and also helps in reducing weight. Its advantages are that it requires less power than traditional PV array tracking; there is no need for sensors to determine the position of the sun and also that it being a two degree of freedom spherical mechanism yields a large singularity free mirror orienting workspace. Solar radiation, efficiency, and temperature are plotted as a function of time for analysis. Average diffuse solar radiation is found to be in the range of 15 to 20% of total solar radiation. Different experiments are performed to find out the optimum cycle speed for reflector. Measurements show that output from the PV panel can be increased in the order of 22% with the use of tracking reflector. This work has succeeded in its goal in realization that the considerable increase in output power from PV modules can be achieved.
Fracture Behavior of a Dual Phase Sheet Steel in Hole Expansion
Authors: Zhang Yuxiu , Liu Yi , Wu Xin
Published: May 2009

It is commonly recognized that for Advanced High Strength Steels (AHSS) the forming limit is mainly controlled by fracture, rather then by localized necking. To date a reliable fracture limit for forming AHSS is not well defined, especially when a practical forming process is under complex strain paths. Hole expansion test has been used by auto industry for assessing fracture-controlled material forming limit. Understanding of crack mechanisms involved in crack initiation and propagation is important for prediction of fracture failure. A dual phase steel with a fine grain and 20–40vol% martensite particles of ∼1μm mean size was used for this study. The results indicate that the hole piercing and blank placement during hole expansion has sensitive impact to the evaluation of edge crack initiation and propagation. Through the comparative study on the “burr up” and “burr down” blank settings the fracture process and the effect of blank preparation, hole expansion, burr geometry effect on crack initiation, and the crack propagation direction and local interaction with microstructure are investigated.
Multiple Scattering of Elastic Waves by Cubical Lattices of Spheres
Authors: Liu Zunping , Cai Liang-Wu
Published: May 2009

The band gap for elastic waves propagating in a cubical lattice of spherical scatterers is observed through a series of numerical simulations. Along the direction of the incident wave, scatterer arrangements are viewed as comprising layers of scatterers, within which scatterers form a square grid. Starting from one layer and by increasing the number of layers, near-field forward and backward wave propagation spectra are computed as the number of layers increases. In the computations, scatterer polymerization methodology is used. This methodology is based on an analytically exact solution to a general three-dimensional multiple scattering problem obtained by the authors. It can be used to reduce an assemblage of actual scatterers to a lesser number of abstract scatterers. These simulations also demonstrate that the computational system has the capability to simulate multiple scattering of elastic waves in three-dimensional space.
Radiation Characteristics of Chlamydomonas Reinhardtii and Its Genetically Engineered Strains With Less Chlorophyll Pigments
Authors: Berberoglu Halil , Pilon Laurent , Melis Anastasios
Published: May 2009

Photobiological hydrogen production is a sustainable alternative to thermo-chemical and electrolytic technologies with the added advantage of carbon dioxide mitigation. However, the scale-up of this technology from bench top to mass culture in industrial photobioreactors suffers from low solar-to-chemical conversion efficiency and irradiance transmittance limitations. In order to overcome these challenge, algae such as Chlamydomonas reinhardtii, can be genetically engineered to have reduced pigment concentrations in their photosystems. Thus, algae do not absorb more light than they can utilize. Moreover, reducing pigment concentration will enable solar radiation to penetrate deeper in the photobioreactor thus facilitating greater productivity in the high density mass culture. The objective of this study is to experimentally measure the radiation characteristics of the unicellular green algae Chlamydomonas reinhardtii CC125 and its truncated chlorophyll antenna transformants tla1 and tlaX. Their extinction and absorption coefficients are obtained from normal-normal and normal-hemispherical transmittance measurements over the spectral range from 300 to 1,300 nm. Moreover, a nephelometer with a He-Ne laser source is used to measure the scattering phase function of the microorganisms at 632.8 nm. Results indicate that the mass absorption cross-sections decrease for the truncated chlorophyll transformants while the single scattering albedo increases. Therefore, light scattering becomes more important in photobioreactors using the genetically engineered strains. The results reported can be used with the radiative transport equation (RTE) to accurately predict and optimize light transport in photobioreactors for photobiological hydrogen production and/or carbon dioxide mitigation using genetically engineered microorganisms.
Prediction of Biomechanical Properties of Bone Implant Scaffolds
Authors: Shanjani Yaser , Chandrashekar Naveen , Toyserkani Ehsan
Published: May 2009

This work is concerned with the 3D finite element modeling of porous implants in which the pore characteristics and distribution are taken into account. The analysis is conducted for scaffolds composed of various biocompatible materials such as Hydroxyapatite, PMMA, PEEK, Ti-6Al-4V, Silicon Nitride, Zirconia and Alumina. Furthermore, the potential of bone growth within the scaffolds is investigated using principal strain histograms of loaded scaffolds. The results show that the histogram of the principal strain resembles a top hat distribution while the porosity (void fraction) decreases. For a specific porosity, the principal strain distribution falls within the desired region (for optimal bone growth) by selecting materials with some particular Poisson’s ratio, although stress-shielding possibility rises due to an increase in the apparent stiffness of the scaffold. The increase in the apparent stiffness is a result of high Young modulus of the above-mentioned materials. The model will provide a platform for designers to adjust internal architecture features (e.g., the porosity level, shape/size/orientation of pores and the material properties) based on the host bone data prior to the scaffold fabrication.
Thermodynamic Analysis of the CO2 Gas Removal Process
Authors: Chavez Rosa-Hilda , Cortez-Gonzalez Jazmin , Guadarrama Javier de J. , Hernandez-Guerrero Abel
Published: May 2009

The present paper describes the thermodynamic analysis of the carbon dioxide (CO2) gas removal process in two separated columns with absorption/stripping sections respectively. This process is characterized as mass transfer enhanced by chemical reaction, in which the presence of an alkanolamine enhances the solubility of an acid gas in the aqueous phase at a constant value of the equilibrium partial pressure. A very useful procedure for analyzing a process is by means of the Second Law of Thermodynamics. Thermodynamic analyses based on the concepts of irreversible entropy increase have frequently been suggested as pointers to sources of inefficiency in chemical processes. Furthermore, they point out where the irreversibilities of the process are located, and provide a generalized discussion from the successful application of the technique.
Control of Vibration Flow at the Joint of an L-Shaped Frame
Authors: Mei C.
Published: May 2009

There has been an increasing interest in vibration control in recent years. This is due to demands for mechanical structures to be lighter and faster. Lighter and faster structures are more prone to vibrations. Hence, there is an imperative need for practical solutions to vibration problems in complex practical mechanical systems. Regardless of the complexity of a structure, from wave vibration standpoint, it consists of only two basic types of structural components, namely, structural elements and structural joints. In this paper, a control strategy is developed for controlling vibrations flowing from one structural element to another through the structural joint. An L-shaped beam is studied as an example structure. Numerical results are given.
Design, Fabrication and Testing of a Bioinspired Hybrid Hair-Like Fluid Motion Sensor Array
Authors: Barbier Charlotte , Humphrey Joseph A. C. , Paulus John , Appleby Michael
Published: May 2009

Many animals detect motions in air and water by means of specialized hair-like sensilla that respond with high sensitivity and specificity to the fluid medium motion. For a review see Humphrey and Barth (2007). Examples are the filiform hairs of arthropods such as arachnids, crustaceans and insects, and the vibrissae of seals. In the case of the arthropods the sensors are relatively small (diameter ∼ 5–10 microns, length ∼ 100 – 1000 microns). In the case of seals they are much larger (diameter ∼ 1–2 mm, length ∼ 50 – 150 mm). These sensors are generally clustered in arrays consisting of hairs of different lengths which, for example, in the case of the cricket Grillus bimaculatus and the spider Cupiennius salei can result in frequency fractionation of the motion signals detected. We have designed, fabricated and tested a new type of hybrid sensor array that embodies favorable features taken from the spider trichobothria (such as the flexible membrane structure that supports a trichobotrium) and the seal vibrissae (such as the larger hair length). Each sensor in the array is embedded in a polydimethylsiloxane (PDMS) platform that simulates the spider trichobothrium membrane. Four pairs of capacitors associated with each sensor allow the N-S and E-W detection of fluid motion parallel to the plane of the platform. Sensitivities in the order of few picofarads per 0.5° angular displacements of the sensors are obtained. Measurements and modeling of the sensor array are presented and discussed.
Case Study in the Challenges of Integrating CNC Production and Enterprise Systems
Authors: Venkatesh S. , Sides B. , Michaloski J. , Proctor F.
Published: May 2009

Integration of factory floor Computer Numerical Control (CNC) information into Enterprise Resource Planning (ERP) subsystems has been difficult, if not impossible, as traditionally, factory floor machines have been “islands of automation.” Boeing/NIST/Okuma jointly collaborated on a pilot project for using a CNC open architecture controller to collect real-time Boeing-specific part accounting data during the production of Boeing 737 Leading Edge (LE) Panels. The goal was to develop a practical and standardized approach in which to capture the real-time part data and then provide this information to an Enterprise Resource Planning (ERP) subsystem. This paper presents the results from our Boeing/Okuma/NIST pilot project that evaluated Ole for Process Control (OPC) as an integration strategy for the LE Production Line part accounting at Boeing. Using OPC, automatic logging of the relevant part production statistics was done for each production line, which in turn was used to more accurately determine the total cost of making each LE production line.
Design and Validation of Fuzzy Logic Control for a Smart Projectile Fin
Authors: Mudupu Venkat , Trabia Mohamed B. , Yim Woosoon , Weinacht Paul
Published: May 2009

This paper deals with the design and validation of the fuzzy logic control for a smart fin of a projectile. The fin is actuated by a cantilevered piezoelectric bimorph that is completely enclosed within the fin. A linear model of the actuator and fin is identified experimentally by exciting the system using a chirp signal. A procedure for designing a GA-based fuzzy logic controller for the fin is presented. The controller is verified using simulation and experimental testing that is conducted in the subsonic wind tunnel at the University of Nevada, Las Vegas (UNLV). Results illustrate that the proposed controller can track the desired fin angle control under various operating conditions.
Thermal Conductivity of Cubic Mesoporous Silica Thin Films
Authors: Hur Soojung C. , Pilon Laurent , Christensen Adam , Graham Samuel
Published: May 2009

This paper reports, for the first time, the cross-plane thermal conductivity of highly ordered cubic mesoporous silica thin films with porosity of 31% and thickness ranging between 200 and 500 nm. The mesoporous thin films are synthesized based on evaporation induced self-assembly process. The pores are spherical with average inter-pore spacing and pore diameter equal to 5.95 nm and 5 nm, respectively. The thermal conductivity is measured at room temperature using the 3ω method. The experimental setup and the associated analysis are validated by comparing the thermal conductivity measurements for the silicon substrate and for high quality thermal oxide thin films with data reported in the literature. The cross-plane thermal conductivity of the synthesized mesoporous silica thin films does not strongly depend on film thickness due to the reduction in phonon mean free path caused by the presence of nanopores. The average thermal conductivity is 0.61 ± 0.011 W/mK, which is 56% lower than that of bulk fused silica at room temperature.
Flank Correction for Spiral Bevel and Hypoid Gears on a Six-Axis CNC Hypoid Generator
Authors: Shih Yi-Pei , Fong Zhang-Hua
Published: May 2009

Because the contact bearings of spiral bevel and hypoid gears are highly sensitive to tooth flank geometry, it is desirable to reduce the flank deviations caused by machine errors and heat treatment deformation. Several methods already proposed for flank correction are based on the cutter parameters, machine settings, and kinematical flank motion parameters of a cradle-type universal generator, which are modulated according to the measured flank topographic deviations. However, because of the recently developed six-axis Cartesian-type computer numerical control (CNC) hypoid generator, both face-milling and face-hobbing cutting methods can be implemented on the same machine using a corresponding cutter head and NC code. Nevertheless, the machine settings and flank corrections of most commercial Cartesian-type machines are still translated from the virtual cradle-type universal hypoid generator. In contrast, this paper proposes a flank-correction methodology derived directly from the six-axis Cartesian-type CNC hypoid generator in which high-order correction is easily achieved through direct control of the CNC axis motion. The validity of this flank correction method is demonstrated using a numerical example of Oerlikon Spirac face-hobbing hypoid gears made by the proposed Cartesian-type CNC machine.
Band Gap Formation by Cylinder Arrays in an Acoustic Waveguide
Authors: Cai Liang-Wu , Calvo David C. , Dacol Dalcio K. , Orris Gregory J.
Published: May 2009

Scattering of acoustic waves by arrays of identical circular cylindrical scatterers in a horizontal waveguide is studied. Although three-dimensional in its geometry, the waveguide permits only a finite number of modes of acoustic wave propagating in different directions with respect to horizontal, and the number of these propagating modes increases as the frequency increases. The horizontal wave numbers of these modes span a range of frequency limited by the total wave number. Numerical examples are used to explore a special case in which the cylinder height equals the depth of the waveguide and in which the cylinders and the waveguide have pressure-release boundaries at both top and bottom surfaces. In such a special case, there is no coupling among the modes permitted by the waveguide and hence is the simplest case for such problems. It is observed that the combination of the modes generally decreases the wave-blocking effects of a stop band; and it is likely that a stop band in one waveguide mode might correspond to a pass band in a different mode. However, numerical examples also show that the main characteristics of a stop band are maintained, despite the multiple modes; and it is possible to extend the stop band by cascading cylinders arrays of different arrangement.
Suppression of Flow Boiling Instabilities in Microchannels Using Artificial Reentrant Cavities
Authors: Kuo Chih-Jung , Peles Yoav
Published: May 2009

Flow boiling instability in parallel microchannel and the ability of artificial reentrant cavities to suppress their occurrence was experimental studied. Experiments were conducted using two types of 226 μm hydraulic diameter parallel microchannel devices: microchannel with reentrant cavities and plain-wall microchannel. Onset of nucleate boiling (ONB), critical heat flux (CHF) condition, onset of flow oscillation (OFO), and local temperature were also obtained and compared. It was found that reentrant cavities on channel walls can assist mitigating the rapid bubble growth instability and postpone the parallel channel and compressible volume instability, which resulted in the delay of CHF.
Simulation of Chatter Vibrations in Reaming
Authors: Sajjadi M. , Movahhedy M. R.
Published: May 2009

A time domain approach is used to study the cutting conditions in reaming process that leads the system to regenerative chatter vibrations. The dynamic analysis of the system includes inertia of the tool, centripetal and Coriolis terms, damping and the first mode bending of reamer. A model of cutting forces proportional to chip cross sectional area and process damping proportional to cutting speed is considered. Numerical simulation based on the Euler integration scheme is carried out to obtain time domain solution of the equation. Despite linearization in force modelling, the model is nonlinear due to the change in the tool engagement area. Another nonlinearity included in the model jumping out of is the tool from cutting. The results of this model are presented and compared to the results of a linear model regenerated in time domain from previous works.
A Maximal Loop Approach to Automatic Sketching of Mechanisms
Authors: Nie Songhui , Liu Hongzhao , Qiu Aihong
Published: May 2009

Sketching of mechanisms identified during the type synthesis process constitutes an important link with the subsequent dimensional synthesis process in the systematic design of mechanisms. Based on the independent loops, a simple and comprehensive method for automatically sketching every type of kinematic chain regardless of the number of links and degrees of freedom is proposed. In the method, a maximal feasible outer-loop is derived by the independent loops addition or subtraction such that all the independent loops become its non-crossing inner loops. During automatic sketching of mechanisms process, the joints of kinematic chain are located on vertices of concentric inscribed regular polygon by outer lane to inner lane in terms of the outer loop and the inner loops. The development and application of this algorithm based on the outer loop and the inner loops relationships are demonstrated with the aid of several mechanism examples.
Free Vibration of Rectangular Composite Laminates With Delamination
Authors: Shiau L. C. , Hwang S. T.
Published: May 2009

In this paper, the effect of delamination on natural frequencies and natural modes of a simply supported rectangular symmetric composite plate with through-width delamination was investigated by the finite strip method. The delamination was assumed to be located at mid-plane of the laminate so that the contact/impact phenomenon between delaminated interfaces does not exist for the free vibration of the laminate. A finite strip with bending and in-plane stiffnesses was derived for the free vibration analysis. The effects of delamination length, delamination location, fiber angle, stacking sequence, and aspect ratio of the laminate on the natural frequencies of the laminate were studied and presented. Results show that the above mentioned factors have considerable effect on the natural frequencies of the laminate. The aspect ratio of the plate is also having significant effect on the frequency of the laminates, especially on the mode 2 frequency of the cross-ply laminate.
Using Data Acquisition Software to Generate the Vibration Response of a Structure
Authors: Myszka David H. , Drehs Todd O.
Published: May 2009

This paper outlines an automated structural vibration response test that is completely prepared and conducted by engineering technology students. An imbalanced weight, is placed on the shaft of a DC motor, and mounted onto a semirigid structure. The students create a data acquisition program that sends a set voltage to the motor, operating it at a certain speed. The program gathers motor speed and vibration data, then changes the motor voltage and repeats the sequence. Thus, the frequency response of a mechanical structure is automatically generated. This test allows students to create a comprehensive, and in-depth mechanical test procedure using only common equipment, and low cost sensors. Additionally, the power of data acquisition software is incorporated, and clearly recognized. The experience is designed to be completed in one 2–1/2 hour period. This paper provides the necessary details to implement the test at other institutions.
Active Rigidity Smart Joint for a Bat-Wing Micro Air Vehicle
Authors: Manzo Justin E. , Garcia Ephrahim
Published: May 2009

In order to maximize lift for use in turning and landing maneuvers, bats make use of continuous camber change along their fifth metacarpal more effectively than all modern-day aircraft flaps. This biological shape change produces lower drag than modern aircraft, allowing for greater flight efficiency and lower noise signatures. A mechanism to replicate this demands a seamless actuator to avoid gaps and discontinuities, and requires the use of morphing structures. However, a recurring problem in morphing aircraft design is inefficiency of both space and power consumption. Problems often stem from the replacement of rigid structural elements with actuator elements that must be powered in order to carry static loads. To resolve this issue, a ‘smart joint’ concept is proposed which allows rigidity in its passive state, and becomes compliant while serving as an actuator by way of a composite of smart materials. Using a network of shape memory alloy and shape memory polymer, the joint is capable of rotations on the order of 5 percent camber over an arbitrary length when placed along a skeletal element of a bat-like wing structure. An analytical model is used to predict the behavior of the joint as a function of resistive heating and external loading, and is used to examine the layer thicknesses and locations (i.e. bimorph vs. unimorph) and placement of rigid elastic members in order to maximize deflection under a given load. Validation of the joint using is conducted via finite element modeling, and expected airfoil data for a generic shape maneuver to be accomplished by this joint is shown.
Parametric Studies of a Coupled Transport/Hyperelastic Model for High Energy Density Nastic Materials
Authors: Freeman Eric , Weiland Lisa
Published: May 2009

The focus of this research is to optimize the performance of a high energy density active material based upon biological processes. This material uses controlled transport of charge and fluid across a selectively permeable membrane to achieve bulk deformation, similar to nastic movements in the plant kingdom. The membrane utilizes biological ion pumps, ion channels, and ion exchangers surrounding a spherical inclusion in a polymer matrix. This work examines the effect of the geometry of the inclusion and the surrounding matrix on the predictions of the model.
Investigation of the Dilution of Outfall Discharges Using Computational and Neuro-Fuzzy Techniques
Authors: Abdel Gawad Ahmed F.
Published: May 2009

This paper represents a comprehensive study of the dilution of multiple outfall discharges. The discharges emerge from the passage bottom in the form of circular jets. The investigation is concerned with the bounded water passages (open channels). These water passages are frequently found in the Nile delta in Egypt. Moreover, a neuro-fuzzy approach is proposed to predict important characteristics of the dilution process. The main objective is to use the computational results to train the neuro-fuzzy models. Useful conclusions and suggestions are drawn from the present investigation.
Phase Transitions and Thermal Expansion of 10mol%Sc2O3-1mol% CeO2-ZrO2 Ceramics
Authors: Yarmolenko Sergey , Ray Devendra , Pai Devdas , Sankar Jag
Published: May 2009

Phase transitions and CTE of 10mol%Sc2O3-1mol%CeO2-ZrO2 ceramics sintered from two commercial powders produced by Praxair Surface Technologies, USA and DKKK, Japan are studied. Morphology of powders and grain structure of ceramics were studied by SEM and AFM. Ceramics produced from Praxair powder exist in cubic phase while DKKK-based ceramics exhibit slow phase transformation from cubic to rhombohedral (β) phase at temperatures 350–400°C. c-β Phase transition temperature is 440°C obtained by high temperature x-ray diffractometry (HTXRD) and differential scanning calorimetry. Coefficients of thermal expansion of cubic and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25–800°C. These results can be further used for the optimal design of SOFC layered structures as well as for determination of their reliability and durability under operational conditions.
A Comparison of Two Different Strategies for Undergraduate Research Within the Framework of a Rotor Dynamics Laboratory
Authors: Meagher Jim , Wu Xi
Published: May 2009

Introductory graduate level courses and upper division technical electives often present a student with his or her first research project. Time limitations of a course require a balance between open ended discovery, development of specialized technical knowledge, and teaching the mechanics of research methodology. The case study presented in this paper is an outline of two different strategies to introduce research to undergraduate students within the framework of a rotor dynamics laboratory. The laboratory had historically been designed to demonstrate machinery malfunctions in a series of short exercises. The laboratory was changed to have several introductory labs designed to prepare students for an extended self-directed research project that included literature searches, paper reviews, design of experiments, and presentation of research findings to the class. In one strategy the students were expected to practice discovery primarily through experimentation with specific, restricted goals. In the other strategy the students were given more flexibility defining the research question and in establishing priorities. Both projects had students design an experiment whose results were compared to mathematical simulations and each led to research that was presented at a conference. Although both were considered successful in terms of student learning and research outcomes, a balance biased toward experimentation and restricted student options for discovery actually led to broader research findings and more in-depth student research but with less student appreciation for and practice with the necessary preliminary stages of conducting research. The student learning experiences and methodologies for each scenario are presented and compared in this paper.
Design and Fabrication of Fast Micro Heaters for Temperature Programming Micro Gas Chromatographs
Authors: Ramesh Chetan , Bhushan Abhinav , Overton Edward , Murphy Michael C.
Published: May 2009

Prototype, low power, high rate resistance heaters for temperature programming metal micro gas chromatograph (GC) separation column chips were fabricated using UV lithography. Spin coated polyimide was used as the electrically insulating layer between the heating coil and the GC column chip because of its excellent thermal properties — in particular the ability to match the coefficient of thermal expansion with nickel and copper, and ease of application. Low resistivity, copper and nickel, metal heating elements were electrodeposited directly on the polyimide layer spin coated on top of the nickel GC column chips. In experiments, the microfabricated heaters were able to heat the GC column at rates from 5°C/sec to 50°C/sec under PID control. Temperatures from 125°C to 250°C were maintained for soak times of up to 30 seconds. The heaters can be used to generate a variety of temperature programming profiles and offer flexibility in selecting the different ramp rates and soak temperatures needed for different applications.
A MicroGyro With Quartz Fork Sensor
Authors: Wang Frank
Published: May 2009

Mainly targeting the automotive application, Systron Donner’s MicroGyro with quartz fork sensor uses a vibrating quartz tuning fork to sense angular rate, acting as a Coriolis sensor, coupled to a similar fork as a pickup to produce the rate output signal. In this paper, the theoretical analysis of the quartz fork model is presented. Following that, the control of the drive magnitude and design of the pickup path are discussed in details. Experiment results from mechanical testing and electrical testing are presented to show that the MicroGyro has achieved 0.03°/s/rtHz.
Design of Disturbance Observers for Multi-Input Multi-Output Systems
Authors: Shahruz Shahram M. , Yi Jingang
Published: May 2009

In this paper, the long-standing problem of designing disturbance observers for multi-input multi-output (MIMO) systems is solved. The disturbance observer presented here has a simple structure equivalent to that of the internal model control (IMC), thereby there is no need for the system inversion. Techniques to design the proposed disturbance observer are given. Furthermore, the design procedure is illustrated via examples for different MIMO systems.
Suppression of Vibration Localization in Non-Axisymmetric Periodic Structures
Authors: Shahruz Shahram M. , Yi Jingang
Published: May 2009

In this paper, mistuned non-axisymmetric periodic structures are considered. In such a structure, vibration localization, which results in large vibrations in some components of the structure, can occur. Such a behavior is due to mistunings in the structure components, small damping, and weak coupling between components. The efficacy of a passive technique in suppressing vibration localization in mistuned non-axisymmetric periodic structures is examined. The technique is based on adding small components between components of structures. It is shown numerically that the added components suppress vibration localization in mistuned structures. Application of the technique studied in the paper to comb drives of micro electromechanical systems (MEMS) is given.
Performance of Mechanical Band-Pass Filters Used in Energy Scavenging in the Presence of Fabrication Errors and Coupling
Authors: Shahruz Shahram M. , Yi Jingang
Published: May 2009

In this paper, several mathematical models that are more realistic representations of mechanical band-pass filters are studied. Such filters can be used in energy scavengers to convert energy from vibration sources into a small amount of electricity. A mechanical band-pass filter is an ensemble of cantilever beams where at the tip of each beam a mass, known as the proof mass, is mounted. A beam with a proof mass at its tip is called a beam-mass system. By studying a variety of models representing the filter dynamics, it will be unraveled to what extent fabrication errors in beam-mass systems of a filter and/or the coupling of such systems can alter the band-pass behavior of a fabricated filter.
Study on Mathematic Model of Air Valve Based on Real Gas Characteristics
Authors: Hu Jianyong , Zhang Jian , Suo Lisheng , Zheng Yuan
Published: May 2009

Air valve is an important measure of water hammer protection in long water supply system. Accurate simulation of the air-inlet and air outlet process of air valve is directly relative to the safety of water supply engineering. Operational principle of air valve is analyzed and new mathematic model of air valve is built based on Van der Waals equation. Protective function of air valve in transient process caused by valve closing is analyzed with the characteristics method. The result shows the new mathematic model of air valve presents a series of new characteristics in the process of air-inlet and air-outlet comparing with the old mathematic model based on ideal-gas state equation.
Analytical Solutions for Effective Axial Mechanical Properties of a Three-Phase Active Fiber Composite Model
Authors: Askari Davood , Ghasemi Nejhad Mehrdad N.
Published: May 2009

Active fiber composites are among the many other components used in intelligent and smart composite structures which undergo mechanical deformation upon the application of external loads or electric fields. This work presents an analytical approach for derivations of exact solutions for the effective axial mechanical properties of active fiber composites with circular cross-sections, and while the properties of the constituent materials are considered to be generally orthotropic. First, exact analytical solutions of the effective longitudinal Young’s modulus and Poisson’s ratio are obtained for a three-phase composite cylindrical model composed of orthotropic materials. Next, Finite element analysis, as an alternative approach, is performed to numerically determine the effective axial properties of an identical three-phase composite cylinder. Finally, effective material properties obtained from analytical and finite element methods are compared to verify the derived analytical solutions. Excellent agreements are achieved between the results obtained from both techniques validating the exact analytical solutions.