bluuebunny/crossref_metadata_2025 huggingface dataset:
Mesoscopic Model for Simulation of CNT-Based Materials
Authors: Volkov Alexey N. , Simov Kiril R. , Zhigilei Leonid V.
Published: August 2009

A mesoscopic computational model is developed for simulation of the collective behavior of carbon nanotubes (CNTs) in CNT-based materials. The model adopts a coarse-grained representation of a CNT as a sequence of stretchable cylindrical segments defined by a chain of nodes. The dynamic behavior of CNTs is governed by the equations of motion for the nodes, enabling computationally efficient “molecular dynamics-type” simulations. The internal part of the mesoscopic force field takes into account stretching and bending of individual CNTs. A novel computationally-efficient “tubular” potential method is developed for the description of van der Waals interactions among the nanotubes. The parameterization of the “tubular” potential is based on an interatomic potential for non-bonded interactions between carbon atoms. The application of the mesoscopic model to simulation of systems consisting of hundreds of CNTs demonstrates perfect energy conservation for times as long as tens of nanoseconds. Self-assembly of CNTs into bundles with hexagonal ordering of nanotubes is observed in simulations performed for systems with initial random orientation of CNTs.
Self-Assembly of Rod-Like Particles Into 2D Lattices
Authors: Janjua M. , Nudurupati S. , Fischer I. , Singh P. , Aubry N.
Published: August 2009

It was recently shown by us that spherical particles floating on a fluid-fluid interface can be self-assembled, and the lattice between them can be controlled, using an electric field. In this paper we show that the technique can also be used to self assemble rod-like particles on fluid-fluid interfaces. The method consists of sprinkling particles at a liquid interface and applying an electric field normal to the interface, thus resulting in a combination of hydrodynamic (capillary) and electrostatic forces acting on the particles. A rod floating on the fluid interface experiences both a lateral force and a torque normal to the interface due to capillarity, and in the presence of an electric field, it is also subjected to an electric force and torque. The electric force affects the rods’ approach velocity and the torque aligns the rods parallel to each other. In the absence of an electric field, two rods that are initially more than one rod length away from each other come in contact so that they are either perpendicular or parallel to the line joining their centers, depending on their initial orientations. In the latter case, their ends are touching. Our experiments show that in an electric field of sufficiently large strength, only the latter arrangement is stable. Experiments also show that in this case the electric field causes the rods of the monolayer to align parallel to one another and that the lattice spacing of a self-assembled monolayer of rods increases.
Aerodynamic Investigation of Air Knife System to Find Out the Mechanism of the Check Mark in a Continuous Hot-Dip Galvanizing Process
Authors: Yoon Hyun Gi , Ahn Gi Jang , Chung Myung Kyoon , Kim Jong Keun
Published: August 2009

When galvanized steel strip is produced through a continuous hot-dip galvanizing process, the thickness of the adhered zinc film is controlled by a gas wiping process. In the gas wiping process there is a technically serious problem which is called a “check mark problem”. The check mark is caused by non-uniform coating on the steel strip surface. Such a non-uniform zinc coating lowers the quality, productivity and profit of the end products. In the present study, to find out the causes of the check mark and technical methods to resolve the check mark problem, the flow field of the high speed rectangular nitrogen gas jet which is impinging on the moving steel strip in the continuous hot-dip galvanizing system has been investigated numerically by using a commercial 3-D flow analysis code, FLUENT. LES (Large Eddy Simulation) is used to obtain instantaneous flow field in the region under consideration. Numerical studies were conducted for two ratios of the plate distance (d) to the nozzle width (x) d/x = 6.7, 10.5 under the same jet Reynolds number of Re = 20000. It was found that the check mark is caused by the alternating vortices which are generated on the jet impinging line (stagnation line). The center of the alternating vortex has a relatively low pressure compared with the periphery of the vortex. The high impinging pressure removes the adhered molten zinc more than the low pressure. Hence the non-uniformity of the zinc coating appears on the strip surface. Such the alternating vortices move periodically to the right and to the left sides on the impinging line due to the jet flow instability and the pressure force balance. In addition since the strip moves upward at a constant speed, the non-uniform coating results in a variety of patterns like “W”, “V” and “X”. This pattern is collectively called as “check mark” in the production field. The angle of the check mark was calculated by using both the moving speeds of the steel strip and the vortices. It was favorably compared with the experimental measurement.
Thermal Conductance of Bi-Material AFM Cantilevers
Authors: Shen Sheng , Narayanaswamy Avind , Goh Shireen , Chen Gang
Published: August 2009

In this letter, based on the beam theory and the thermal analysis of a bi-material cantilever, we demonstrate that the effective thermal conductance of the cantilever and the temperature at the tip of the cantilever can be determined by measuring the bending of the cantilever in response to two different thermal inputs: power absorbed at the tip and ambient temperature. The bi-material cantilevers were first introduced as a calorimeter to measure the heat generated in chemical reactions. [1] The same device was demonstrated to be sensitive enough to measure power as small as 100 pW or energy of 150 fJ in photothermal measurements. [2] They were also used as IR detectors [3, 4, 5] or as scanning thermal imaging probes. [6] Although the bi-material cantilevers are often used as temperature or heat flux sensors based on the beam bending due to the unequal thermal expansion of the two materials, the exact temperature at the tip of the cantilever is usually unknown. Directly measuring the temperature is difficult due to the small geometry of the cantilever structure. To find out the temperature of the cantilever, one should obtain the thermal conductance of the cantilever. However, since the thermal properties of two layers of the cantilever are dependent on their thickness, one cannot rely on theoretical calculation. In this letter, we develop a technique to determine the thermal conductance of the cantilever by measuring the bending of the cantilever in response to the variations of the absorbed power at the tip and the ambient temperature. A triangular silicon nitride cantilever coated with 70 nm gold film is used in the current experiment. As shown in Fig.1 (a), a semiconductor laser beam is focused on the tip of the cantilever and reflected onto a position sensing detector (PSD). The deflection of the reflected laser beam spot on the PSD is used as a measure of the deflection of the cantilever. A part of the laser power is absorbed by the cantilever and thus creates a temperature rise at the end of the cantilever. The output of the PSD is converted into an X or Y signal corresponding to the position of the laser spot on the PSD and a sum signal proportional to the incident laser power.
Electrical Leakage Through Thin PDMS Microchannel Walls and its Applications
Authors: Sun Jiashu , Vajandar Saumitra K. , Xu Dongyan , Kang Yuejun , Li Dongqing , Li Deyu , Hu Guoqing
Published: August 2009

PDMS is usually considered as a dielectric material and PDMS microchannel walls can be treated as an electrically insulated boundary. However, in certain layouts of microfluidic networks, electrical leakage through PDMS walls could significantly alter the electrical field in the microfluidic circuits, which must be carefully considered in microfluidic circuit design. We report on our experimental characterization of electrical leakage through PDMS microfluidic channel walls. Numerical modeling clearly disclosed the alteration of electrical field and electroosmotic velocity in the microfluidic channels because of the electrical leakage through the thin PDMS wall. In addition, we demonstrate that the electrical leakage through the PDMS channel wall can be used to realize trapping of individual particles at different locations inside the mcirofluidic channel by balancing the electroosmotic flow and electrophoretic migration of the particle.
Development of a Diffusion Limited Microfluidic Module for DNA Purification via Phenol Extraction
Authors: Morales Mercedes C. , Zahn Jeffrey D.
Published: August 2009

Purification of Deoxyribonucleic acid (DNA) by organic-aqueous liquid extraction, also called phenol extraction, is a standard technique commonly utilized in biology laboratories. In order to minimize interaction energies, membrane components and proteins naturally partition to the organic (phenol) phase while the DNA stays in the aqueous phase, where it can be easily removed. In recent years, microfluidics has become a driving force toward more efficient and autonomous platforms for fluid based diagnostics, chemical reaction chambers, separation and preparation of biological materials. In this work, fabrication, and performance of a long microfluidic device for DNA extraction are presented. The devices were fabricated using soft lithography to transfer lithographically defined features into a PDMS structure via replica molding. Stratified-flow experiments using a rhodamine dye conjugated bovine serum albumin protein (BSA) in an aqueous phase were conducted to demonstrate the ability to remove proteins from the aqueous phase into the phenol phase. Additionally, the study of BSA partitioning and DNA isolation in a two-phase system under stratified flow condition were presented, separately and conjunctly. Finally, protein partitioning and DNA recovery obtained with this device could be compared with other types of mixing and extraction such as mixing by droplet formation and electrohydrodynamic (EHD) instability.
Loading Direction Versus Crack Propagation Path in a Lead-Free Single Solder Joint Sample
Authors: Gao Feng , Jing Jianping , Johnson Janine , Liang Frank Z. , Williams Richard L. , Qu Jianmin
Published: August 2009

In this paper, single solder joints (SSJs) were subjected to moderate speed loading (5mm/sec) in different directions, from pure tensile, mixed mode to pure shear. Fracture surfaces from different loading directions were examined both experimentally and numerically. It is observed that intermetallic compound (IMC) is formed between the solder alloy and the Cu pad, and failure typically occurs at or near the solder/IMC/Cu interfaces on the board side. Pure tensile loading typically leads to interfacial fracture along the IMC/Cu interface. Mixed mode loading usually results in a mixture of interfacial and cohesive failure with crack propagating in a zigzag fashion between the solder/IMC interface and the solder alloy. Loading with higher shear component tends to result in more cohesive failure of the solder alloy near the solder/IMC interface. Under pure shear loading, failure is almost always cohesive within the solder alloy near the solder/IMC interface.
Control of Non-Spherical Particles in Microfluidic Channel
Authors: Song Minghao , Wang Pengtao , Sun Hongwei
Published: August 2009

A precise control of orientation and position of micro- and nano-particles is critical for their applications in micro- and nano-scale systems. This research is focused on a numerical investigation of controlling the cylindrical particle/road with transverse electric field in a pressure driven microchannel flow with Finite Element Method (FEM). The particle/rod is initially located at the channel centerline with different initial angles. The electrophoretic force and hydrodynamic force are combined to control particle/rod movement. It was found that pressure, applied voltage and initial angles have different impact on particles dynamic behavior.
Numerical Simulation of Contaminant Dispersion Within an Aircraft Interior
Authors: Wang Xiuling , Pepper Darrell W.
Published: August 2009

A hybrid numerical model has been developed to simulate contaminant dispersion within an aircraft interior. A two-equation Low-Reynolds-Number adaptive FEM model is used for simulating turbulent flow within an aircraft. Coupled with Lagrangian Particle Transport Technique, contaminant dispersion within aircraft interiors can be accurately simulated. Mesh independent studies can be avoided when using the adaptive technology, an L2 norm error estimator is used to guide the adaptation procedure. By using the adaptive algorithm, mesh independent studies can be avoided.
Experimental Study on Nucleation Site Interaction During Pool Nucleate Boiling by Using Three Artificial Cavities
Authors: Sato Takato , Koizumi Yasuo , Ohtake Hiroyasu
Published: August 2009

Pool nucleate boiling heat transfer experiments were performed for water using heat transfer surfaces having unified cavities. Cylindrical holes of 10 μm in diameter and 40 μm in depth were formed on a mirror-finished silicon wafer of 0.2 mm in thickness using Micro-Electro Mechanical Systems (MEMS) technology. This silicon plate was used as the heat transfer surface. The test heat transfer surface was heated by a semiconductor laser beam. Experiments were conducted in the range of up to 1.35 × 105 W/m2. When the cavity spacing was narrow such as S = 1 or 2 mm, the convection created by the departure of coalesced bubbles played a main role in heat transfer when the heat flux was low. As the heat flux was increased, the coalesced bubbles absorbed enough heat to become large while the frequent bubble departure was maintained. As a result of it, the latent heat term in heat transfer became large to approximately 40%. When the cavity spacing was wide such as S = 4 mm, a bubble absorbed heat enough to become large before departure and the coalescence of bubbles were not prominent. Thus, the latent heat term took approximately 50% in heat transfer. With an increase in the heat flux, the vertical coalescence became to happen quite frequently. This coalescence made convection vigorous to increase the heat transfer. As a result of it, the convection term increased to 60% and the latent term decreased to 40%.
Analytical Prediction of the Transition to Chaos in Porous Media Natural Convection
Authors: Vadasz Peter
Published: August 2009

The failure of the linear stability analysis to predict accurately the transition point from steady to chaotic solutions in porous media natural convection motivates this study. A weak non-linear solution to the problem is shown to produce an accurate analytical expression for the transition point as long as the validity condition and consequent accuracy of the latter solution is fulfilled. The analytical results are compared to accurate computational solutions showing an excellent fit within the validity domain of the analytical solution.
A Study of Mixing and Its Enhancement in an Impeller-Stirred Tank
Authors: Roy Somnath , Acharya Sumanta , Gao Diangrong
Published: August 2009

Mixing inside a moderately turbulent Rushton impeller stirred tank (STR) has been explored using both experimental and computational tools. Numerical predictions showed satisfactory agreement with experimental observations. Mixing behavior of a passive scalar inside the tank is predicted numerically in order to identify the zones of poor mixedness. Effects of variable impeller-speed are studied through velocity measurements using Particle Image Velocimetry (PIV). Impeller-speed perturbations promoted the spreading of impeller jet and enhanced the level of turbulent fluctuations. The enhancement in fluctuating components of turbulent velocity is expected to promote better mixing inside the tank.
Heat Transfer in Novel Internally-Finned Heat Exchange Passages
Authors: Zhou Fuguo , Acharya Sumanta
Published: August 2009

Heat exchange passages usually use internal fins to enhance heat transfer. These fins have ranged from simple ribs or turbulators to complex helical inserts. Applications of interest range from traditional heat exchangers to internal cooling of turbine blades. In the present paper, a novel fin design that combines the benefits of swirl, impingement and high heat transfer surface area is presented. Measurements of the internal heat transfer coefficients are provided using a liquid crystal technique. Pressure drop along the passage are also measured, therefore friction factors and thermal performance factors are presented. The experiments cover Reynolds number from 10,000 to 40,000 based on the hydraulic diameter of the main channel of the test section. Two models are tested, which have fins oriented at 30 degree and 45 degree to the flow direction, respectively. The results demonstrate that these novel designs produce overall heat transfer ratios greater than 3 compared to the smooth passage.
Internal Resonance of Finite Beams on Nonlinear Foundations Traversed by a Moving Load
Authors: Ansari Masoud , Esmailzadeh Ebrahim , Younesian Davood
Published: August 2009

Vibration analysis of beams traversed by moving load is an old and well known topic in structural mechanics, and has been of great interest for researchers of different fields, such as mechanical, railway and civil engineering. Many researchers have conducted different investigations in this field. In the present research, the nonlinear vibration of the system is studied and consequently the response of the system to a moving load is determined as a closed form solution. Furthermore, the effects of load amplitude on the response of the system are investigated. Galerkin’s method is first utilized to truncate the governing equation of motion and then MMS (Method of Multiple Scales) perturbation method is applied to study the nonlinear vibration of the system, in the presence of the internal resonance. Effects of damping of the foundation as well as magnitude of the moving load on the frequency responses are investigated. The proposed methodology and obtained results can be used to investigate the behavior several systems among which railway system shows a good compatibility.
A General Approach to Analysis of Flow and Heat Transfer in Packed Beds
Authors: Vadnjal Aleksander , Catton Ivan
Published: August 2009

It is postulated that proper scaling will collapse the multiplicity of data for friction and heat transfer coefficient to a usable reasonably general formulation by choosing the hydraulic diameter as Dh=4·〈m〉Sw where  is the average porosity and Sw is the surface area per unit volume. The chosen hydraulic diameter allows the transformation and comparison of correlation equations and experimental results obtained for diverse media morphologies. Also, it allows experimentally-determined characteristics of the media to be related to the closure relationship derived from the VAT analysis. The numerical results of closure are presented and are compared to various experimental results. The Nusselt number is based on the media internal local surface average transfer coefficient and the friction factor is the local internal value. Results obtained by VAT closure using direct numerical simulation show reasonable agreement between calculated local friction factors and local heat transfer coefficients and data confirming that the friction factor and heat transfer coefficient when correctly scaled can be computed numerically with satisfactory results. This conclusion will enable one to optimize the effectiveness of a compact heat exchanger in terms of porosity and internal surface area.
The Use of Volume Averaging Theory (VAT) for Evaluation of Surface Heat Transfer Augmentation
Authors: Tam V. K. , Chang M. R. , Catton I.
Published: August 2009

A model, based on Volume Averaging Theory (VAT), was developed to predict friction and heat transfer over augmented surfaces. The objective is to find augmentation that produces a higher heat removal relative to the increase in pumping power necessary to overcome the additional friction that is generated. This was accomplished with a numerical solution of the VAT transport equations for describing fully developed turbulent flow in a channel with augmented surfaces. Friction factor and Nusselt number results produced by the numerical simulation are compared with experimental data to validate the model and which of the augmented surfaces performs the best is clearly show.
CFD Analysis of Batch-Type Reheating Furnace for Improved Heating Performance
Authors: Wu Bin , Roesel Tom , Arnold Andrew M. , Xu Zhaojiang , Arnold Eugene , Downey George , Zhou Chenn Q.
Published: August 2009

A reheating furnace is a critical component in value-added steel production. These furnaces can have a significant impact on both product quality and total cost. In order to obtain a better understanding of the furnace operation which influences the temperature distribution, a Computational Fluid Dynamics (CFD) analysis has been conducted to examine the transient and three dimensional temperature fields in a prototype of the number three reheating furnace located at ArcelorMittal. Also, a series of simulations have been conducted to maximize the furnace performance. These parametric studies include different burner designs, fuel flow rates, and combustion air supplies to optimize the heating capacity of the furnace. The comparison of the simulation results assists in understanding the effective factors which are critical to the improvement of the furnace’s production capacity, thus providing insight into furnace optimization.
Fabrication and Test of Polymer-Based Electrospray Device
Authors: Tran Si Bui Quang , Byun Doyoung , Nguyen Vu Dat , Yu Myoung Jong , Lee Kyun Ho
Published: August 2009

In this paper, interference effect between multi-nozzles has been experimentally investigated for an electrospray device. Array of nozzles is either prepared by electrically conductive stainless steel capillaries and by electrically dielectric nozzle array fabricated using polymer material. The result shows that polymer-based device may reduce or avoid the interference effect when the spacing distance between nozzles is optimized. For a conductive electrospray array, the end effect, which is able to deflect conejets through the outer nozzles of the array due to asymmetric electric field and repulsive forces between adjacent conductive nozzles and the menisi, can be eliminated by using two dry nozzles mounted at the boundary. However, for a polymer-based device, the end effect can be avoided without using extra dry nozzles. In order to eliminate this end effect, a novel ten-nozzle Polymethyl Methacrylate (PMMA)-based electrospray, with inner and outer diameters of 300μm and 500μm, respectively, has been successfully fabricated and evaluated. The performce of the multi-nozzle array device is analysed by measuring the current of the charged droplets through a novel ten nozzles of the polymer-based electrospray device.
Designing and Manufacturing of a “Pick and Place-Painting” Robot With Adaptive-Robust Controller
Authors: Safavi Seyed Mohsen , Mirian Seyed Saeed , Hoshyarmanesh Hamid Reza , Khandan Rasoul
Published: August 2009

In this research, primarily designing and manufacturing of Double Acting Pick and Place robot (DAP) mechanism, along with its kinematic and dynamic analysis aiming at elimination of human force usage in contaminated industrial environment such as coating process shops is introduced and analyzed. Simulations of the robot’s movement and control procedure via nonlinear adaptive-robust and inverse dynamic controllers are applied in order to overcome to their uncertainties. The main function of this robot is coating epoxy powder on “Hawel” gate valves at temperatures up to 200°C. The results obtained in this study can greatly fulfill the need to resolve industrial uncertainties in such combinational processes.
Flow in a Corrugated Channel With Multiple Heat Sources
Authors: Alawadhi Esam M.
Published: August 2009

Numerical method based on the finite element method is utilized to study the heat transfer enhancement from discrete heat sources using a wavy channel. The considered geometry consists of a channel formed by two wavy plates with six discrete heat sources placed on upper and lower walls. The effect of the Reynolds number, Prandtl number, waviness of the wavy wall, and the location of the heat sources on the heat transfer out of the heat sources is investigated. The result indicates that the wavy channel significantly enhances the heat flow out of the heat sources, and heat sources located at the minimum cross section areas of the channel shows the best performance. The heat transfer enhancement can reaches as high as 120% for high Reynolds numbers and waviness of the channel.
Heat Transfer Considerations for Designing FSW Cryogenic Thermal Structures for Aerospace Applications
Authors: Langerman Michael A.
Published: August 2009

Research was conducted to investigate potential structural design configurations for aerospace cryogenic tank wall applications. The primary design considerations included the vibration damping characteristics under various flight loading conditions and the panel wall thermal resistance under different heat loads. The discussion herein is with regards to the thermal issue, specifically the heat transfer rates across two different panel wall designs that have attractive vibration damping characteristics. The heat transfer rates were evaluated analytically and verified with experimental data. One panel is a corrugated, serpentine-layered design fabricated using friction stir welding. The other panel is an “egg-carton” design fabricated using friction stir spot welding. An important thermal consideration for the cryogenic tank wall design is the minimum outer wall temperature attained during ambient storage or prior to launch. Of the two designs considered herein, neither wall provided sufficient thermal resistance to maintain outer wall temperatures above freezing under ambient conditions. One of the wall designs, however, performed somewhat better. It is shown that when configured with an outer layer of thermal plastic coating both designs could maintain an outer wall temperature within design constraints.
Capillary Flow With Overlapping Electrical Double Layer
Authors: Song Zhuorui , Ban Heng
Published: August 2009

Most analytical models for the electrokinetic flow were developed for pipe or channel sizes sufficiently large or the zeta-potential sufficiently small for the application of Boltzmann distribution. With increasing interest in nano-fluidic flows, the effect of overlapping electrical double layer (EDL), which means that the pipe size is similar to or less than the Debye length, plays a more and more important role in the flow. The Boltzmann equation, which has been widely used to describe the ionic distribution in the EDL in the semi-infinite domain, is not applicable for the case of the overlapping EDL due to its limited flow space. The Nernst equation, instead, has been suggested in the literature.
Ambient Condition Effects on NOx and CO Emissions From Process Heaters
Authors: Bussman Wesley R. , Baukal Charles E.
Published: August 2009

Because process heaters are typically located outside, their operation is subject to the weather. Heaters are typically tuned at a given set of conditions; however, the actual operating conditions may vary dramatically from season to season and sometimes even within a given day. Wind, ambient air temperature, ambient air humidity, and atmospheric pressure can all significantly impact the O2 level, which impacts both the thermal efficiency and the pollution emissions from a process heater. Unfortunately, most natural draft process burners are manually controlled on an infrequent basis. This paper shows how changing ambient conditions can considerably impact both CO and NOx emissions if proper adjustments are not made as the ambient conditions change. Data will be presented for a wide range of operating conditions to show how much the CO and NOx emissions can be affected by changes in the ambient conditions for fuel gas fired natural draft process heaters, which are the most common type used in the hydrocarbon and petrochemical industries. Some type of automated burner control, which is virtually non-existent today in this application, is recommended to adjust for the variations in ambient conditions.
Online Wall Thickness Control for Blow Molded Part Using Hybrid Optimization Method and Fuzzy Iterative Learning Control Algorithm
Authors: Huang Geng-Qun , Huang Han-Xiong
Published: August 2009

An online wall thickness control strategy for the extrusion blow molded part was proposed in this work. A simulation-based optimization method combining with finite element, artificial neural network, and genetic algorithm was used to determine the initial die gap profile for a part with required thickness distribution. A multi-channel ultrasonic thickness measurement system was built up to get the in-mold wall thickness of the blow molded part. Then, a feedback closed-loop control system based on fuzzy iterative learning control algorithm was designed and implemented to control the wall thickness of blow molded part. The results showed that the online wall thickness control system developed in this work can automatically achieve a proper die gap profile and get the satisfied part thickness distribution.
Analysis of Dual Phase Lag Heat Conduction in Gold Nanoparticle Based Hyperthermia Treatment
Authors: Liu C. , Li B. Q. , Mi C.
Published: August 2009

This paper addresses the fast-transient heat conduction phenomena of a gold nanoparticle embedded in cancerous tissue in hyperthermia treatment. Dual phase lag model in spherical coordinates was employed and a semi-analytical solution of 1-D non-homogenous dual phase lag equation was presented. Results show that transient temperature depends dramatically on the lagging characteristic time of the surrounding tissue. Temperature predicted by dual phase lag model greatly exceeds that predicted by a classical diffusion model, with either a constant source or a pulsed source. This phenomenon is mainly attributed by the phase lag of heat flux of tissue. The overheating in short time scale and the consequent biological effect needs to be paid more attention in the related study.
CFD Simulation of a Meso-Scale Combustor: An Exercise in Verification and Validation
Authors: Weathers Jeffrey W. , Taylor Robert P. , Weathers James B.
Published: August 2009

With the simulation of engineering processes via numerical methods on the rise comes the need for a quantitative measure of the agreement between computational results and experimental measurements. The use of quantitative methods in the comparison of the results of numerical and experimental analyses supersedes the traditional qualitative approach. In the present paper, the importance of the role of modeling assumptions in a verification and validation effort is illustrated through a meso-scale combustor example. The various types of uncertainties encountered in the experimentation and numerical simulation are investigated. Through the investigation the initial modeling assumptions proved to be insufficient, producing a comparison error outside of the acceptable range. Thus, the modeling assumptions were sequentially revised, minimizing the comparison error and producing a successful verification and validation effort.
Heat Transfer Performance of a Pulsated Two-Phase Loop Thermosyphon
Authors: Islam Md. Ashraful , Rahman Md. Ashiqur , Alam Mohammad
Published: August 2009

Thermoloop is a pulsated two-phase thermosyphon (PTPT) comprising of evaporator, condenser and a liquid reservoir with associated tubing and fittings with a view to cooling electronic devices. This study presents an experimental investigation on the thermoloop to address some issues on design and heat transfer performance. The evaporator employed in this study was of 72.5 mm × 60 mm × 20 mm in dimension with inside volume of 75 cm3. The reservoir had a liquid storing capacity of 80 cm3. A copper tubular condenser was used as the heat sink having two different convection conditions. For various heat input, evaporator wall temperatures, condenser inlet and outlet temperatures and reservoir liquid column height were recorded at a regular interval. For the variation of heat input from 100 W to 250 W, the maximum temperature of the evaporator wall increased from 106°C to 112°C and the minimum temperature of evaporator wall increased from 73°C to 95°C at an evaporator fill ratio of 30%. The values of other functional parameter such as cycle time, height of liquid column in the reservoir and condenser temperature also increased with an increase in thermal load. The inclusion of a fan to cool the condenser increased the operational limit of the device from 125 W to 275 W. This thermoloop device transported heat in cyclic and pulsated manner; the amount of heat transported was as high as 250 W with a thermal resistance of 0.116 m2K/W. Furthermore, various functional parameters of the thermoloop attained a steady value after 5 to 6 heat transport cycles.
The Forming Theory and NC Machining for Rotary Burs With the Spectral Edge Distribution
Authors: Liu Huran
Published: August 2009

The rotary burs with special cutting edges are researched. It is the newest lay out of such tools, and represents the international direction of development of such kind of cutters. The cutting condition of the cutter is improved dramatically.
Visibility Analysis of Vehicles and Mobile Equipment: A Design and Forensic Method
Authors: Ferrone Christopher W. , Przybyla Julie A. , Orseske Matthew T.
Published: August 2009

Trucks, cars, buses, trains and construction machinery often come into contact with people and objects. An issue that naturally arises during the vehicle design phase or after a vehicle accident is the available visibility from the operator’s station. A method is needed that allows acquisition of data that can be translated into a format understood by both technical and non-technical users.
LES-PIV Comparison for Air Flow in a Simplified Cowl-Box
Authors: Berger Re´mi , Depardon Se´bastien , Rambaud Patrick , Buchlin Jean-Marie
Published: August 2009

A single-phase Large Eddy Simulation is performed in a simplified cowl-box model and compared to PIV data. Indeed, prior to the analysis of the interaction between a turbulent air flow and an interface of liquid, the most accurate description of the 3D flow field is required. Although the qualitative phenomena are correctly rendered (flapping motion of impinging inlet jets), quantitative differences are noticed, mainly due to non satisfactory turbulent boundary condition, which induces an overestimation of the jets core length, and modifies its interaction with the cowl box walls. Nevertheless, a qualitative analysis of the instantaneous flow shows the generation of large coherent vortical structures due to the oscillation of the impinging jets at the bottom wall. The advection of these structures in the cowl-box generates large oscillations of wall shear stress and pressure distribution, which are thought to be of great importance for further two-phase flow simulations.
The Experimental Investigation of Fouling Phenomenon in Tubular Heat Exchangers by Heat Transfer Resistance Monitoring (HTRM) Method
Authors: Izadi M. , Aidun D. K. , Marzocca P. , Lee H.
Published: August 2009

The aim of this paper is to describe a monitoring system for fouling phenomenon in tubular heat exchangers. This system is based on a physical model of the fouling resistance. A mathematical model of the fouling resistance is also developed based on applied thermal heat, the inside heat transfer coefficient and geometrical characteristics of the heat exchanger. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocities, and some physical properties of the fluid flowing inside the tubes such as viscosity, conductivity, and density. An on-line fouling evaluation system has been prepared and heat transfer resistance for selected solutions has been measured in real time by this system. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Output data is significantly important for the design, and for formulating operating and cleaning schedules of the equipment.
Electrical Conductivity and Elastic Properties of MWCNT-PP Nanocomposites
Authors: Ngabonziza Yves , Li Jackie , Barry Carol F.
Published: August 2009

Electrical and elastic properties of multiwalled carbon nanotubes (MWCNTs) reinforced polypropylene (PP) nanocomposites were studied experimentally and theoretically. The MWCNT-PP nanocomposites samples with a range of 0 to 12 wt% MWCNT were injection molded using different injection velocities. These nanocomposites were characterized for their electrical resistance using 2-Probe measurement and their tensile properties. Parallel to the experimental investigation, a percolation theory was applied to study the electrical conductivity of the nanocomposite system in terms of content of nanotubes and injection rate. Both Kirkpatrick [1] and McLachlan [2] models were used to determine the transition from low conductivity to high conductivity which designates as percolation threshold. Both experimental and modeling results have shown that the electrical conductivity increased suddenly as the content of MWNTs was close to percolation threshold of 3.8 wt%. The injection speed also showed an effect on electrical conductivity of the composites. In addition, several micromechanical models were applied to elucidate the elastic properties of the nanocomposites. The results indicate that the interphase between the carbon nanotubes and polymers plays an important role in determining elastic modulus of the system.
Growth and Characterization of Iron Nanoparticle Catalysts for Nanomaterial Synthesis
Authors: Lombardo Jeffrey J. , Lysaght Andrew C. , Goberman Daniel G. , Chiu Wilson K. S.
Published: August 2009

The properties and structure of nanoscale particles can vary widely from their bulk counterparts. In order to use nanoparticles effectively one must first have an understanding of their composition. In this study, Fe nanoparticles were grown on fused quartz substrates using a method that allows for varying particle size and surface coverage by altering the particle deposition time. The resulting particles were analyzed using x-ray photoelectron spectroscopy (XPS) in order to understand how nanoparticle composition evolves as a function of deposition time. In addition, atomic force microscopy (AFM) was used to correlate the changes in size and surface density of the Fe particles with the changes in the XPS spectra as deposition time was varied. Knowledge gained through this study will be used to optimize the growth of Fe nanoparticles for single-walled carbon nanotube (SWNT) synthesis.
Automotive Side Glazing Ejection Mechanisms: Part I — Model Development
Authors: Batzer Stephen A. , Herndon G. Grant , Semones Paul T. , Thorbole Chandrashekar K. , Ziejewski Mariusz , Hooker Robert M.
Published: August 2009

The mechanisms of occupant ejection through automotive side glazing during rollover collisions are analyzed. It is shown that partial or complete ejection can occur through centrifugal acceleration based motion through an open portal, or due to the changes in velocity (ΔVs) developed during corner impacts. Aspects of vehicle kinematics, effective mass, impact velocity, window design, rotational velocity, and injury are examined. Analysis indicates that the dominant ejection mode is rotational acceleration induced exit motion at a low velocity relative to the center of gravity of the vehicle facilitated by vehicle body flexure based fracture of tempered side glass. In this first part of a two paper series, a new rollover angular velocity model is presented and given experimental validation, and the concept of the two ideal ejection modes is developed.
Development and Testing of an Autonomous Driving Module for Critical Driving Conditions
Authors: Biral Francesco , Bertolazzi Enrico , Bortoluzzi Daniele , Bosetti Paolo
Published: August 2009

In the last years a great effort has been devoted to the development of autonomous vehicles able to drive in a high range of speeds in semi-structured and unstructured environments. This article presents and discusses the software framework for Hardware-In-the-Loop (HIL) and Software-In-the-Loop (SIL) analysis that has been designed for developing and testing of control laws and mission functionalities of semi-autonomous and autonomous vehicles. The ultimate goal of this project is to develop a robotic system, named RUMBy, able to autonomously plan and execute accurate optimal manoeuvres both in normal and in critical driving situations and to be used as a test platform for advanced decision and autonomous driving algorithms. RUMBy’s hardware is a 1:6 scale gasoline engine R/C car with onboard telemetry and control systems. RUMBy’s software consists of three main modules: the manager module that coordinates the other modules and take high level decision; the motion planner module which is based on a Nonlinear Receding Horizon Control (NRHC) algorithm; the actuation module that produces the driving command for the vehicle. The article describes the details of RUMBy architecture and discusses its modular configuration that easily allows HIL and SIL tests.
Comparing of Direct and Sensitivity-Base Model Updating Methods in Structural Dynamics and Its Application for Updating of Cantilever Model
Authors: Abasi K. , Asayesh M. , Nikravesh M.
Published: August 2009

Reliable finite element (FE) modeling in structural dynamics is very important for studies related to the safety of structural components used in industry. FE model updating is a tool to produce these reliable models. The method uses an initial FE model and experimental modal data of the structural components to modify physical parameters of the initial FE model, and a number of approaches have been developed to perform this task. This paper presents an overview of model updating and particularly its application for updating of cantilever model. An example of the need for model updating is a cantilever beam, where often the beam is assumed to be rigidly fixed at the clamped end. However, during tests it is often found that the beam has either a small rotation or deflection at the clamped end. If one has to construct the FE model without the knowledge of the experimental modal data, the natural assumption would be to include an ideal, fixed boundary condition, which may not be true. Even with such a simple structure the FE model is not reliable a priori, and based on intuition or engineering judgments it is difficult to estimate the values of the boundary stiffnesses. However, after creating an initial FE model, the model should be updated based on the experimental modal data obtained from modal tests so that the FE model may be used with confidence for further analysis.
Strain Fields and Transition Energies in Multilayer InAs/GaAs Quantum Dots
Authors: Lin T. R. , Kuo M. K. , Hong K. B.
Published: August 2009

Strain fields and transition energies of vertically stacked semiconductor quantum dots are investigated. Strain fields, induced by lattice mismatches in heterostructures, in and around quantum dots are analyzed on the basis of the linear elasticity. The three-dimensional steady-state strained-effective-mass Schro¨dinger equation is then modified by incorporating the effects of strain fields into the carrier confinement potential and is analyzed by finite element methods numerically. The results include the energy levels and wavefunction spectra of InAs/GaAs quantum dots. The calculated optoelectronic transition energies agree well with the previous experimental photoluminescence data. Numerical results also suggest that transition energy decreases as the spacer thickness increases.
Dynamic Analysis of Soft Tissues With Hard Inclusions
Authors: Shan Baoxiang , Pelegri Assimina A.
Published: August 2009

Research on the biomechanical behavior of soft tissues has drawn a lot of recent attention due to its application in tissue evaluation, early cancer detection, rehabilitation and surgery. Dynamic analysis of soft tissues not only provides histological, pathological and physiological information of the tissues, but also presents theoretical support for the modern medical imaging modalities (like Acoustic Radiation Force Imaging, Harmonic Motion Imaging, Supersonic Shear Imaging and Shear Wave Elasticity Imaging) based on tissue dynamics. Using our FEMSS (Finite Element Method with a State Space representation) technique, a realistic model of breast soft tissue with hard inclusions is geometrically discretized in ANSYS using finite elements, while a state space representation is adopted to characterize the motions of tissues stimulated by an internal radiation force. Our objective for this paper is to investigate the effects of size, location and mechanical properties of hard inclusions on the tissues’ response, frequency spectrum and forced vibration. The response differentiation between soft tissues with and without hard inclusions may reveal the resolution and delectability of the dynamic measurement and could lead in the development of new, more effective diagnostic techniques. Our simulation results indicate that the existence of hard inclusion(s) can significantly change the dynamic response of the tissue system. Specifically, hard inclusions may shift the spectrum of an elastic tissue system to a range of higher frequency, with larger sized hard inclusions causing bigger shifts. Furthermore, the location effect of hard inclusions is exhibited when a shallow one tends to vibrate with a larger magnitude at lower frequency than a deep hard inclusion. Finally, the tissue viscosity can significantly compress the range of high frequencies in the tissue system spectrum and cause the magnitude decrease of the forced vibration.
Review of Recent Developments in Metal and Syntactic Foam for Composite Material Applications
Authors: Roth Grant , Flowers George , Dean Robert
Published: August 2009

The field of composite materials is a rapidly developing and expanding area, with new innovations and discoveries occurring almost daily, producing new available materials, processing techniques, fabrication methods, and applications. This article reviews recent innovations and developments in this field with a specific focus on syntactic and metal foams. Recent work is identified and placed in context with regard to other work in the area. A summary discussion of the implications of this work and potential applications is also provided.