bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Dimensional Microfluidic Photomasking for Microarray Patterning
Authors: McKechnie Jonathan , Sinton David A.
Published: April 2008

This paper presents a novel microfluidic photomasking strategy. Two opaque, dyed streams hydrodynamically focus a transparent stream to define a line of light transmission. Aligning two separate chips orthogonal to each other defines a small area where the transparent streams overlap. A proof-of-concept chip was developed and tested using visible-spectrum light and a visible light absorbing dye. Probe spot sizes of ~80μm are attainable, with spacing between spots of ~150μm.
Taylor-Like Dispersion of Charged Species in Electrokinetically-Driven Nanoflows
Authors: De Leebeeck Angela , Sinton David A.
Published: April 2008

In this paper, electrokinetic dispersion of charged and uncharged species in nanochannels with finite electric double layers is modelled numerically. The relatively thick electrical double layers in these flows influence dispersion through the coupled effects of both cross-stream electromigration and advection in the presence of cross-stream velocity gradients. It is found that valence charge has a significant effect on axial dispersion in these flows, in addition to other established dependencies. Effective diffusion coefficients were found to vary over 30% from the case of neutral species for single charged ions. An effective diffusion coefficient similar to Taylor dispersion is calculated and a relationship between effective diffusion coefficient, Peclet number, relative electric double layer thickness, and valence charge is plotted.
Be´nard-Marangoni Instability in an Open Vertical Cylinder With Lateral Heating
Authors: Xu B. , Ai X. , Li B. Q.
Published: April 2008

A linear stability analysis of Rayleigh-Be´nard-Marangoni flow of low Prandtl number fluid contained in an open vertical cylinder is presented. The cylinder is heated laterally and is cooled at top surface by radiation. Governing equations of the flow are solved for axisymmetric base flow using higher order finite difference scheme. Small perturbation was applied to the obtained base flow to determine the critical Marangoni number and Grashof number at which the axisymmetry is broken. The eigenvalue matrix equation is solved using linear fractional transformation with banded matrix structure taken into account. It is found that the thermocapillary effect stabilizes the convective flow driven by buoyancy.
Thermodynamic Analysis of Production of Hydrogen Using High-Temperature Fuel Cells
Authors: Leal Elisaˆngela Martins , Brouwer Jacob
Published: April 2008

This paper presents: (1) the electricity and hydrogen co-production concept, (2) a thermodynamic analysis methodology for studying solid oxide and molten carbonate fuel cell hydrogen co-production, and (3) simulation results that address the impact of reformer placement in the cycle on system performance. The methodology is based on detailed thermodynamic and electrochemical principles that apply to each of the system components and the integrated cycles. Eight different cycle configurations that use fuel cell heat to drive hydrogen production in a reformer are proposed, analyzed, and compared. The specific cycle configurations include SOFC and MCFC cycles using both external and internal reforming options. The fuel cell plant performance has been evaluated on the basis of methane utilization efficiency and each component of the plant has been evaluated on the basis of second law efficiency. The analyses show that in all cases the exergy losses (irreversibilities) in the combustion chamber are the most significant losses in the cycle. Furthermore, for the same power output, the internal reformation option has the higher electrical efficiency and produces more hydrogen per unit of fuel supplied, in the case of using a SOFC.
An Object-Oriented Systems Engineering Model Design for Integrating Spent Fuel Extraction and System Processes
Authors: Kwan Kenny , Hodges Matthew , Hsieh Hsuan-Tsung , Chen Yitung , Vandergrift George , Copple Jackie , Laidler James
Published: April 2008

The mission of the Transmutation Research Program (TRP) at University of Nevada, Las Vegas (UNLV) is to establish a nuclear engineering test bed that can carry out effective transmutation and advanced reactor research and development effort. UNLV has developed a multi-function software package, TRPSEMPro, to interact with the chemical separation process developed by the Argonne National Laboratories (ANL). As indicated in the Spent Fuel Treatment Facility (SFTF) process requirement, developing a software package system with the capability of optimizing facility process based on the pre-defined objective functions can be valuable for the SFTF. The objective is to further extent the TRPSEMPro framework to integrate chemical separation calculation package AMUSE (Argonne Model for Universal Solvent Extraction) with commercially available system process package (ASPEN-plus). A development concept of middleware is employed to build communication between the AMUSE code and the ASPEN-plus. Since the object-oriented designed ASPEN-plus software package exposes its parameters as well-defined objects, the TRPSEMPro can directly access its variable trees through the object call. Due to the complicity of the system, a scenario-based database system will be developed associated with the chemical separation and system processes. A light-weight MS ACCESS database is selected for easy maintenance and accessibility. The database manages the scenario parameter files with associated separation results and outputs from the system process packages. A comprehensive SFTF process simulation will greatly facilitate the evaluation of overall systems options. Such simulation is gradually becoming important for down-selecting reactor types, fuel types, and multi-recycle modes. Optimization tool associated with the TRPSEMPro system engineering model intends to speedup the possible chemical separation parameters.
Resonant Dynamics in a Rotordynamic System With Nonlinear Inertial Coupling and Shaft Anisotropy
Authors: Quinn D. Dane
Published: April 2008

The response of a nonlinear, damped Jeffcott rotor with anisotropic stiffness is considered in the presence of an unbalance. For sufficiently small external torque or large imbalance, resonance capture or rotordynamic stall can occur, whereby the rotational velocity of the shaft is unable to increase beyond the fundamental resonance between the rotational and translational motion. This phenomena provides a mechanism for energy transfer from the rotational to the translational mode. Using the method of averaging a reduced-order model is developed, valid near the resonance, that describes this resonant behavior. The equilibrium points of these averaged equations, which correspond to stationary solutions of the original equations and rotor-dynamic stall, are described as the applied torque, damping, and anisotropy vary. As the anisotropy increases, assumed to arise from increasing shaft cracks, the torque required to eliminate the possibility of stall increases. However, when the system is started with zero initial conditions, the minimum torque required to pass through the resonance is approximately constant as the anisotropy increases. The predictions from the reduced-order model are verifled against numerical simulations of the original equations of motion.
Theoretical Modeling and Numerical Simulation of the Corrosion/Precipitation Process in Non-Isothermal Pipe Systems
Authors: Tan Taide , Chen Huajun , Chen Yitung , Hsieh Hsuan-Tsung
Published: April 2008

An improved theoretical model was developed to predict the mass transfer controlled corrosion/precipitation in nonisothermal LBE pipe systems. In this mass transfer model, a turbulent core region and a laminar sub-layer region have been considered separately in the total mass transfer to the transferring corrosion product from the wall of the pipe. Two sets of mass transfer equations have been solved respectively both in the turbulent core region and sub-layer region. Following the model development, both of the local corrosion/precipitation rate and bulk concentration were calculated and a theoretic study has been made to illustrate the effects of the axial temperature profile on the corrosion/precipitation rate and buck concentration by applying present model to DELTA loop in Los Alamos National Laboratory. Numerical simulations were preceded in the open pipe systems and the results were analyzed. The solutions obtained also can be extended to the more general problems of high Schmidt mass transfer in the developed turbulent wall-bounded shear flows.
Application of Quality Function Deployment for New Business R&D Strategy Development
Authors: Ashihara Kosuke , Ishii Kosuke
Published: April 2008

This paper describes a decision-making framework for Research and Development (R&D) strategy development using an adaptation of quality function deployment (QFD). Many manufacturing companies are facing challenges in strengthening their competitiveness to survive in an uncertain and fierce competitive businesses environment. Decision-making on R&D strategy, not only for incremental innovation, but also for radical innovation, is essential for the sustainable future of the company. There are well-structured methodologies for routine product development tasks that help planning and decision-making. QFD is one of the most well known tools for product development that uses matrices to identify relative worth of product requirements from market information and flow the requirements down to more detailed decisions. However, in the R&D strategic planning process that occurs prior to product development, there is little work utilizing structured methodologies such as QFD. This paper presents a new usage of QFD in the R&D strategy development process to cover both incremental and radical innovation. Market-pull R&D leads to incremental innovation of the company, and QFD helps identify new technology requirements using future market predictions. On the other hand, technology-push R&D seeks radical innovation; an inverse usage of QFD that defines new customer needs from new technology development can support a step-by-step approach for future business creation in this context. The paper includes a detailed example from the medical device industry that demonstrates the utility of the method in R&D strategy decision process.
Towards Acoustic Vibration as a Diagnostic Tool for Spinal Fractures
Authors: Tawackoli Wafa , Burton Allen , Rhines Larry , Mendel Ehud , Liebschner Michael
Published: April 2008

The diagnostic tools for clinicians to detect vertebral body fractures are limited to radiation technologies1, such as X-ray and CT. The objective is to identify shape changes that reflect bone tissue failure. Because this method is subjective, only crude changes of 15% and more in vertebral height can be detected2. From in-vitro laboratory experiments it is know that the ultimate load is reached at deformations much less than 5%, and is generally detected before any shape changes are visible in radiographic images3. Acoustic vibration is a promising technique to detect changes in material integrity and quality. The overall goal of this study was to investigate the use of acoustic vibration to detect spinal fractures.
Effects of Mechanical Vibration on Osteoblast-Like Cell Line
Authors: Kumaoka M. , Shiraishi T. , Morishita S.
Published: April 2008

Bone formation is subject in vivo to mechanical stimulation. Though many researches for bone cells of osteoblastic lineage sensing and responding to mechanical stimulation have been reported mainly in the biochemical field, the effects of mechanical stimulation are not so understood. In this study, in order to clarify the effects of mechanical vibration on osteoblast-like cells on the basis of the dynamic properties of the cells in the sense of vibration engineering, sinusoidal excitation was applied to the cells, and their cell proliferation and bone matrix generation were investigated as their frequency response. We developed an electromagnetic exciter of culture plates of the cells, which was designed with high stiffness to excite the whole area of the plates uniformly. We seeded MC3T3-E1, which is a mouse calvaria osteoblast-like cell line, and applied sinusoidal excitation for 24 hours a day for 28 days at the frequency of 12.5 or 100 Hz, setting the acceleration amplitude of 0.5 G to fix the inertia force to the cells. As the experimental results of counting the number of the cells using a hemocytometer, the cell density of all the vibrating groups was higher than that of the non-vibrating group after 14-day cultivation. In the most effective case of the frequency of 12.5 Hz and the cultured period of 25 days, the cell density of the vibrating group was higher than that of the non-vibrating group by about 26 %. That was also morphologically shown by the microscopic observation of the cells. By staining the cells with alizarin red S solution, the amount of the generated calcium salts as one of the bone matrices was measured. The amount of the calcium salts of the vibrating groups was higher than that of the non-vibrating group on 28-day cultivation. The number and the size of the nodules of the calcium salts were different depending on the excited frequency. These results of this study suggest that the mechanical vibration promotes the cell proliferation and the bone matrix generation, and that the effects of the mechanical vibration depend on the frequency.
Surface-Based Scaffold Design: A Mechanobiological Approach
Authors: Bucklen B. , Wettergreen M. , Heinkenschloss M. , Liebschner M. A. K.
Published: April 2008

Despite recent need-based advances in orthopedic scaffold design, current implants are unsuitable as “total” scaffold replacements. Both mechanical requirements of stiffness/strength and biological stipulations dictating cellular behavior (attachment, differentiation) should be included. The amount of mechanical stimulation in the form of stresses, strains, and energies most suitable toward implant design is presently unknown. Additionally unknown is if whole-bone optimization goals such as uniform and non-uniform driving forces are applicable to a scaffold-bone interface. At the very least, scaffolds ready for implantation should exhibit mechanical distributions (dependent on loading type) on the surface within the typical mechanical usage window. Scaffold micro-architectures can be strategically shifted into that window. The overall goal of this study was to produce microarchitectures tailored to a more uniform mechanical distribution, while maintaining the morphological properties necessary to sustain its mechanical integrity. The mechanical adjustment stimuli investigated were von Mises stress, strain energy density, maximum principle strain, and volumetric strain. Scaffold models of a similar volume fraction were generated of three initial architectures (Rhombitruncated Cuboctahedron, hollow sphere, and trabecular-like bone cube) using high resolution voxel mapping. The resulting voxels were translated into finite element meshes and solved, with a specially written iterative solver created in Fortran90, under confined displacement boundary conditions. The result was verified against a commercial software. Once the mechanical distributions were identified one of two methods was chosen to alter the configuration of material in Cartesian space. The success of the alteration was judged through a diagnostic based on the histogram of mechanical values present on the surface of the micro-architecture. The first method used a compliant approach and, for the case of stress, reinforced locations on the surface with large stresses with extra material (strategically taken from the least stressed portions). The second method used a simulated annealing approach to randomly mutate the initial state in a “temperature” dependent manner. Results indicate that the mechanical distributions of the initial scaffold designs vary significantly. Additionally, the end state of the adjustment demonstrated anisotropy shifts toward the direction of loading. Moreover, the adjustment methods were found to be sensitive both to the mechanical parameter used for adjustment and the portion of the surface adjusted at each increment. In conclusion, scaffolds may be adjusted using a mechanical surface-based objective, as the surface of the scaffold is crucial toward its in vivo acceptance. This technique provides some mathematical specificity toward the whole of computer-aided tissue engineering.
Micro-Particle Fabrication for Tissue Engineering Applications Using Rapid Prototyping and Soft Lithography Principles
Authors: Wettergreen M. , Scheffe J. , Mikos A. G. , Liebschner M. A. K.
Published: April 2008

The goal of this study was to develop an efficient and repeatable process for fabrication of micro-particles from multiple materials using rapid prototyping and soft lithography. Phase change three-dimensional printing was used to create masters for PDMS molds. A photocrosslinkable polymer was then delivered into these molds to fabricate geometrically complex three-dimensional micro-particles. This repeatable process has demonstrated the ability to generate micro-particles with greater than 95% repeatability with complete pattern transfer. This process was illustrated for three shapes based on the extrusion of two-dimensional shapes. These particles will allow for tailoring of the pore shapes within a porous scaffold utilized in tissue engineering applications. In addition, the different shapes may allow control of drug release by varying the surface to volume ratio, which could modulate drug delivery. While soft lithography is currently used with photolithography, its high precision is offset by high cost of production. The employment of rapid prototyping to a specific resolution offers a much less expensive alternative with increased throughput due to the speed of current rapid prototyping systems.
On-Design and Off-Design Performance Analysis of a Hybrid MCFC-Micro Gas Turbine System Using the Exergy Method
Authors: Zhang Huisheng , Hao Hongliang , Weng Shilie , Su Ming
Published: April 2008

Molten carbonate fuel cells have been revealed to be very attractive power generation system, promising highly efficient electricity generation and very low environmental impact. The integration of micro gas turbine and molten carbonate fuel cells has been proposed in the last years as an extremely efficient solution for power generation. A steady-state thermodynamic exergetic model for MCFC/MGT hybrid power system is developed on the IPSEpro simulation platform, and applied to a performance analysis of exergy. The exergy method highlights irreversibility within the system components, and it is of particular interest in this paper. The simulation results show that the coupling of MGT with a MCFC reactor has shown a potential for an exergy efficiency of plant over 55% at design point and high efficiency at off-design point compared to other conventional power system.
Predictive-Inspection Based Process Control in End Milling Operations
Authors: Khan Aftab , Tilbury Dawn , Moyne James
Published: April 2008

In the manufacturing industry, product quality control is often treated as a completely different problem than process diagnostics. Diagnostics methods are used to quickly identify faults during the process, whereas product quality is assessed at the final inspection stage, after the process is completed. The large amount of data that is collected to enable the on-line diagnostics, however, can be used to predict the product quality before the part is measured at the final inspection stage. This predicted quality can be used as feedback to a control system that improves the process quality by adjusting the process inputs. In this paper we propose a predictive inspection based process control solution for a manufacturing process. A manufacturing process is modelled as an input-output system with the machine settings as inputs and two kinds of outputs: diagnostic data and quality. This model is obtained from off-line experiments using a combination of process inputs and external disturbances. In the online implementation the predictive process model is updated with the diagnostic data collected during runtime and quality is improved by using a two-loop control strategy, on a part-to-part or run-to-run (R2R) basis. The proposed approach is applied to and developed for an end milling operation and simulation and experimental results are presented.
Practical Application of the LES Method to Mixing in Large Indoor Spaces
Authors: Knight Kelly J. , Debus Kristian K. , Berkoe Jon M. , Dasey Tim J.
Published: April 2008

The scope of protecting public venues in the U.S. is staggering in the areas of money, time and experience at doing this sort of thing. Derivation of protection strategies for the building infrastructure will necessarily involve a combination of experiments and computer simulations to provide confidence in building design or retrofit before the needed dollars and time are committed. Computer simulation can be less costly and be performed in shorter times than experiments even when the building of interest is quite large and thus, will be used extensively now and in the future for building protection design. This paper specifically targets the accuracy and application of computational fluid dynamic (CFD) codes for prediction of mixing behavior. The ability to determine the nature, make correct identification and quantify the amount of a release from a chemical or biological weapon (CBW) relies in part on understanding the underlying physics of air propagation throughout the domain. Specifically, we must understand the rates at which a contaminant may mix throughout the domain. Turbulent mixing is a function of the range of spatial and temporal scales found in the domain, i.e., the large scale eddies (on the size of the domain) advecting the contaminant, the small scale eddies (inertial range) “mixing” the contaminant as it is being advected and the time scales corresponding to these eddy sizes. The widely used Reynolds Averaged Navier-Stokes (RANS) numerical modeling methods cannot capture the time dependent motions which are responsible for a significant amount of mixing. The Large Eddy Simulation (LES) method is based on simulating the turbulent fluctuations that can be resolved by the mesh while the smaller eddies are modeled. The LES method can produce more information about the nature of the flow field than RANS. This paper discusses the application of the LES method, specifically an LES/DES (Detached Eddy Simulation) coupled method, to simulate mixing in a realistically scaled fictitious airport. Application of the LES method such as determination of what eddy size to resolve, transient startup effects, determination of eddy turnover time and others are discussed. This research is sponsored by Department of Homeland Security under Air Force Contract F19628-00-C-0002. The views expressed are those of the author and do not reflect the official policy or procedure of the United States Government.
Micromachined Electrical Conductivity Probe for RF Ablation of Tumors
Authors: Yi Ming , Panchawagh Hrishikesh V. , Mahajan Roop L. , Liu Zhengjun , Goldberg S. Nahum
Published: April 2008

RF ablation is an important technique in cancer treatment. It has been proposed that the effective area treated via RF ablation can be increased by increasing the local electrical conductivity. This is achieved by injection of NaCl solution into the tissue. For an accurate and effective RF ablation treatment using this new method, it is necessary to measure the local electrical conductivity, which varies spatially due to diffusion of sodium chloride. In this paper, we propose a micro probe to measure the local tissue electrical conductivity. The probe consists of two in-plane miniature electrodes separated by a small gap. When the electrodes are in contact with the tissue, the electrical resistance across them can be used to calculate the electrical conductivity. The probe is fabricated by standard photolithography techniques. The substrate material is polyimide and the electrodes are made of gold. A four-electrode probe is used to calibrate the new electrical conductivity micro probe using different concentrations of saline water. The resistance measurements are carried out using an impedance analyzer on different frequencies. The frequency of choice for RF ablation of tumors is 500k Hz and is the one selected for calibration and testing. The micro-probe calibration is then verified by measuring electrical conductivity of a phantom and comparing it with the result measured by the four-electrode probe. Finally, some in vivo tests are performed and the results are compared with literate data.
Finite Element Modeling of Aortic Tissue Using High Speed Experimental Data
Authors: Maddali Muralikrishna , Shah Chirag S. , Yang King H.
Published: April 2008

Traumatic rupture of the aorta (TRA) is responsible for 10% to 20% of motor vehicle fatalities [1]. Both finite element (FE) modeling and experimental investigations have enhanced our understanding of the injury mechanisms associated with TRA. Because accurate material properties are essential for the development of correct and authoritative FE model predictions, the objective of the current study was to identify a suitable material model and model parameters for aorta tissue that can be incorporated into FE aorta models for studying TRA. An Ogden rubber material (Type 77B in LS-DYNA 970) was used to simulate a series of high speed uniaxial experiments reported by Mohan [2] using a dumbbell shaped FE model representing human aortic tissue. Material constants were obtained by fitting model simulation results against experimentally obtained corridors. The sensitivity of the Ogden rubber material model was examined by altering constants G and alpha (α) and monitoring model behavior. One single set of material constants (α = 25.3, G = 0.02 GPa, and μ = 0.6000E-06 GPa) was found to fit uniaxial data at strain rates of approximately 100 s−1 for both younger and older aortic tissue specimens. Until a better material model is derived and other experimental data are obtained, it is recommended that the Ogden material model and associated constants derived from the current study be used to represent aorta tissue properties when using FE methods to investigate mechanisms of TRA.
Thermodynamic Analysis of Transcritical Carbon Dioxide Cycles
Authors: Brown Mark , Rosario Luis , Rahman Muhammad M.
Published: April 2008

Research on natural environmentally friendly refrigerants is very important especially because the world-wide agreement about restriction in the use of ozone depleting refrigerants. Carbon dioxide is a natural refrigerant that has been considered for certain refrigeration and air conditioning applications. The aim of this paper is to present a thermodynamic analysis of carbon dioxide cycles in order to evaluate the potential performance of a refrigeration cycle using carbon dioxide. A thermodynamic model for the cycle is developed which can simulate the operation of a carbon dioxide refrigeration/AC cycle. This model takes into account the practical effects of the thermo-physical properties of carbon dioxide as refrigerant in a trans-critical cycle. A sensitivity analysis has been conducted so that cycle performance is estimated. The cooling load, compressor power, and coefficient of performance (C.O.P.) were evaluated. One and two stages of compression were also considered for comparison purposes. Cycle performance was evaluated based on variation of important parameters such as evaporator, intermediate, and discharge pressures. The effects of cycle components on system capacity and cycle performance are also investigated. Comparison between performances of the CO2 cycle and the standard vapor compression cycle is performed. Thermodynamic calculations showed reasonable agreement with available experimental data based on the general assumptions made.
Characterization and Design of a Non Ported Conventional Speaker for Acoustic Control
Authors: Shim Taehyun
Published: April 2008

A loud speaker has been widely used as a major actuator in the field of active noise control (ANC). In this paper, the design procedures for a non-ported conventional speaker that must meet restrictive size constraint as well as required sound pressure level at a targeted frequency for an acoustic control was presented. Dynamic model of a speaker that includes linear and nonlinear effects such as radiation resistance on speaker damping, voice coil electrical resistance has been developed and its responses were compared to measured data. The effects of speaker design parameter variations on a sound pressure and power consumption were also assessed experimentally and through simulation. It was found that the simulation results are well collated with experimental data and the desired objective has been met.
Non-Linear Stacking Effects in Microfluidic Temperature Gradient Focusing
Authors: Huber David E. , Santiago Juan G.
Published: April 2008

Temperature gradient focusing (TGF) is a promising type of field gradient focusing that simultaneously concentrates and separates charged species according to their electrophoretic mobilities. TGF focuses samples by balancing local electrophoretic and advective fluxes for each analyte species. The technique utilizes buffers whose ionic strength vary with temperature to induce conductivity gradients appropriate for this electrophoretic focusing. In most cases, the contribution of the focused species to the ionic strength is negligible, and linear focusing is observed. In this work, we investigate experimentally non-linear stacking effects that occur when the conductivity of the stacked sample approaches that of the background buffer.
Thermocapillarity and Thermoviscosity Effects on the Spin Coating of Wetting Liquids Above an Axisymmetrically Heated Disk
Authors: Wu Lin
Published: April 2008

The spin coating of wetting liquid on an axisymmetrically and radially heated disk is studied numerically under lubrication and zero Biot number assumptions. Our results show that both thermocapillarity (temperature dependent surface tension) and thermoviscosity (temperature dependent viscosity) effects can be harnessed to enhance the depletion rate of the spin coated liquid film if the disk center is hot. When the applied radial temperature profile has a steep change, an anchored shock wave is generated with a strength determined by the temperature induced viscosity change.
Automotive Diagnostic Decisions Using Probabilistic Information
Authors: Schwall Matthew L. , Gerdes J. Christian
Published: April 2008

Safety, emissions, and driver demands all require progressively better automotive fault detection, identification, and recovery (FDIR). Probabilistic diagnostics represents an effective way of improving fault detection and identification even as vehicle complexity increases. This paper presents a method for making decisions based on fault probabilities, so that these advances can enable more effective fault recovery. The decision maker’s goal is to choose a set of actions that minimizes risks resulting from faults, and this requires analyzing the temporal behavior of the faults and actions. Using a vehicle’s stability control system as an example, a method is presented for modeling these dynamics and determining the optimal decision strategy. Most calculations can be performed off line and stored, enabling efficient real-time decision making. The paper concludes by presenting the optimal decision strategy for the vehicle example.
Small Two-Stage Centrifugal Blowers
Authors: Funabashi Shigehisa , Honda Takeshi , Isoshima Nobuyuki , Takada Yoshihiro , Suganami Masayuki , Nakano Yasuyuki
Published: April 2008

We surveyed small two-stage centrifugal blowers, specifically their static parts and silencers. One of their features was a simple diffuser without a division plate between two centrifugal impellers instead of the normal return channel. Variety chord return vanes that gradually shorten along airflow passes are efficient for our characteristic diffuser channel. Diffuser vanes are efficient for increasing the pressure of a blower only behind the first impeller. If they are behind the second impeller, they cause the pressure of the blower to fall. We designed an original suction-side silencer with channels of two different lengths. The difference in the lengths was aligned to a half wavelength of the main noise, specifically the blade passage frequency noise. With our silencer, sound waves of different phases canceled each other out at the inlet of the blower. As a result, the noise of the blowers was reduced to 18 dB.
Optimized Thermal Design for USB-WLAN Module
Authors: Chen Eason , Lai Jeng Yuan , Wang Ming Zong , Wang Yu-Po , Hsiao C. S.
Published: April 2008

With the increasing demands of wireless network, WLAN modules are developed with various kinds of product patterns; USB type among all is popular for portability. In the market, most USB-WLAN products are made in small form factors that advantage to carry and use as daily portable electronic products. However, the compact size of USB-WLAN elevates the junction temperatures of every package in the module that potentially downgrade the reliability of product. This is a severe challenge for package and module designers that drive a necessity to characterize the thermal behavior from package level to module level to ensure the success of product development. A thermal study was therefore considered for an USB-WLAN module having Baseband, RF and PA packages mounted on a PCB. The characterizations for a commercial USB-WLAN module were conducted with a computational fluid dynamics (CFD) tool to cover the following factors: package design of Base-band and PA, power input level, PCB size and PCB design. The selections of Base-band and PA packages with better Theta_JB performance resulted in better thermal dissipation into PCB. Several power density levels were performed to observe the heat transfer interactions among packages. Different designs of PCB Cu layer, thermal via number and distribution were then investigated in module level simulations for package thermal enhancement. Finally a sample of USB-WLAN module was also built to examine the accuracy of modeling with good agreement.
Symbolic Graph Techniques Applied to Mechanical System Analysis and Featuring
Authors: Fakhfakh Mourad , Fakhfakh Tahar , Loulou Mourad , Haddar Mohammed , Masmoudi Nouri
Published: April 2008

In this paper we present a symbolic analysis tool. It uses the directed graph techniques for the automatic modeling, featuring and analysis of dynamic systems. We use the proposed tool to model mechanical system. With the help of the electromechanical analogies, this tool automatically generates symbolic and semi-symbolic transfer function between specified input and output nodes. The performances of the symbolic tool are exemplified for some dynamic systems.
Modeling the Motion of Slurry Nanoparticles During Chemical Mechanical Polishing
Authors: Terrell Elon J. , Jasti Venkata K. , Higgs C. Fred
Published: April 2008

Chemical mechanical polishing (CMP) has emerged as a commonly used method for achieving global surface planarization of micro-/nano-scale systems during fabrication. During CMP, the wafer to be polished is pressed against a rotating polymeric pad that is flooded with slurry. The motion of the wafer surface against the asperities of the pad and the abrasive nanoscale particles in the slurry causes the surface of the wafer to be polished to an atomically smooth level. Past studies have shown that the wear distribution is a function of the distribution of slurry particles in the wafer/pad interface, and thus it is desirable to model the migration of particles in order to predict the wear of the wafer surface. The current study involves the creation and simulation of a mathematical model which predicts the paths of slurry particles in a Lagrangian reference frame. The model predicts the effects of the various forces on each particle to determine its motion. The model also accounts for interparticle collisions and wafer/particle and pad/particle collisions. It is expected that the particle motion that is predicted from this model will allow for a more accurate correlation of the wafer surface wear distribution.
S-Rail Sled Testing With Deceleration Sled
Authors: Mayer Robert R. , Webb Scott , McCleary Joe , Gusko Ruth , Oliveira Dino , Worswick Michael
Published: April 2008

This paper considers the effects of rotary draw bending on structural crashworthiness. We impacted tested aluminum alloy tubes in s-rail bending, using either 2.0 mm or 3.5 mm thickness, and bend radius of either 152.4 mm or 191 mm. This report documents and summarizes the test setup using the GM R&D Deceleration Sled to achieve this, with emphasis on later correlation with numerical simulation. Theoretical and numerical analyses were used to help with design setup. Forces and moments found in the tests were very consistent, suggesting good test setup design. We also found that using the longest tube section at the constrained end prevents inboard rotation and contact between the two s-rails.
A System for Performing Content-Based Searches on a Database of Mechanical Assemblies
Authors: Deshmukh Abhijit S. , Gupta Satyandra K. , Karnik Mukul V. , Sriram Ram D.
Published: April 2008

The increased use of 3D CAD systems by product development organizations has resulted in large databases of assemblies; this explosion of assembly data will continue in the future. Currently, there are no effective content-based techniques to search these databases. Ability to perform content-based searches on these databases is expected to help the designers in the following two ways. First, it can facilitate reuse of existing assembly designs, and thereby reducing the design time. Second, a lot of useful Design for Manufacturing and Assembly (DFMA) knowledge is embedded in existing assemblies. Therefore a capability to locate existing assemblies and examine them can be used as a learning tool by the designers to learn from the existing assembly designs and hence transfer the best DFMA practices to new designers. This paper describes a system for performing content-based searches on assembly databases. We identify templates for comprehensive search definitions and describe algorithms to perform content-based searches for mechanical assemblies. We also illustrate capabilities of our system through several examples.
Effect of Parameter Uncertainty on Reliability of Hydraulic Transmission System Simulation
Authors: Ellman A. , Kauranne H. , Kajaste J. , Pietola M.
Published: April 2008

Simulation of fluid power systems has become a tool widely used for designing and testing purposes. The usefulness of this approach is however highly dependent on the results that have uncertainty to some extent. In the theoretical approach uncertainty depends mainly on the simplifications made in the modeling, algorithms used and parameters. In the experimental approach uncertainty depends on the transducers and the construction of the measurement system and data transfer. This paper discusses the effect of parameter uncertainty on the reliability of virtual testing of hydrostatic transmission systems in general. The definition of the total uncertainty by using a sum of variances is presented and applied to basic equations of fluid power. As an application a simplified hydrostatic transmission circuit is investigated. Importance of grade of models in reducing the computational inaccuracy is discussed.
Order Reduction of Nonlinear Systems Subjected to an External Periodic Excitation
Authors: Redkar Sangram , Sinha S. C.
Published: April 2008

In this work, the basic problem of order reduction nonlinear systems subjected to an external periodic excitation is considered. This problem deserves attention because the modes that interact (linearly or nonlinearly) with the external excitation dominate the response. A linear approach like the Guyan reduction does not always guarantee accurate results, particularly when nonlinear interactions are strong. In order to overcome limitations of the linear approach, a nonlinear order reduction methodology through a generalization of the invariant manifold technique is proposed. Traditionally, the invariant manifold techniques for unforced problems are extended to the forced problems by ‘augmenting’ the state space, i.e., forcing is treated as an additional degree of freedom and an invariant manifold is constructed. However, in the approach suggested here a nonlinear time-dependent relationship between the dominant and the non-dominant states is assumed and the dimension of the state space remains the same. This methodology not only yields accurate reduced order models but also explains the consequences of various ‘primary’ and ‘secondary resonances’ present in the system. Following this approach, various ‘reducibility conditions’ are obtained that show interactions among the eigenvalues, the nonlinearities and the external excitation. One can also recover all ‘resonance conditions’ commonly obtained via perturbation or averaging techniques. These methodologies are applied to some typical problems and results for large-scale and reduced order models are compared. It is anticipated that these techniques will provide a useful tool in the analysis and control of large-scale externally excited nonlinear systems.
Performance Analysis of Combined Humidified Gas Turbine Power Generation and Multi-Effect Thermal Vapor Compression Desalination Systems
Authors: Wang Yongqing , Lior Noam
Published: April 2008

Humidified gas turbines (HGT) have been identified as an promising way of producing power and their use in combined power and water desalination systems is analyzed, employing energy and exergy performance criteria. Based on two representative HGT cycles, the steam-injected gas turbine (STIG) cycle and evaporative gas turbine (EvGT) cycle, two combined systems are proposed. After analyzing the characteristic of desalination units, a multi-effect thermal vapor compression (METVC) unit run by the exhaust heat of the power cycle is chosen to produce fresh water from seawater for both general use and the HGT humidification. Some of the main results are: the fuel consumption of water production in a STIG-based combined system is about 45% of a water-only unit, and that in a EvGT-based system it is 31%~54%; compared with the individual power-only and water-only units, the fuel savings of the two combined system are 12%~28% and 10%~21%, respectively; a water production gain of more than 15% can be obtained by using a direct-contact seawater-gas heat exchanger to recover the stack heat; and the two combined systems are more flexible in their power-to-water ratio than currently used dual-purpose systems.
A Novel Brayton Cycle With the Integration of Liquid Hydrogen Cryogenic Exergy Utilization
Authors: Zhang Na , Lior Noam
Published: April 2008

Stored or transported liquid hydrogen for use in power generation needs to be vaporized before combustion. Much energy was invested in the H2 liquefaction process, and recovery of as much of this energy as possible in the re-evaporation process will contribute to both the overall energy budget of the hydrogen use process, and to environmental impact reduction. A new gas turbine cycle is proposed with liquefied hydrogen (LH2) cryogenic exergy utilization. It is a semi-closed recuperative gas turbine cycle with nitrogen as the working fluid. By integration with the liquid H2 evaporation process, the inlet temperature of the compressor is kept very low, and thus the required compression work could be reduced significantly. Internal-fired combustion is adopted which allows a very high turbine inlet temperature, and a higher average heat input temperature is achieved also by internal heat recuperation. As a result, the cycle ha ry attractive thermal performance with the predicted energy efficiency over 79%. The choice of N2 as the working fluid is to allow the use of air as the oxidant in the combustor. The oxygen in the air combines with the fuel H2 to form water, which is easily separated from the N2 by condensation, leaving the N2 as the working fluid. The quantity of this working fluid in the system is maintained constant by continuously evacuating from the system the same amount that is introduced with the air. The cycle is environmentally friendly because no CO2 and other pollutant are emitted. An exergy analysis is conducted to identify the exergy losses in the components and the potential for further system improvement. The biggest exergy destruction is found occurring in the LH2 evaporator due to the relatively higher heat transfer temperature difference. The energy efficiency and exergy efficiency are 79% and 52%, respectively. The system has a back-work ratio only 1/4 of that in a Brayton cycle with ambient as the heat sink, and thus can produce 30.14 MW (53.9%) more work, with the LH2 cryogenic exergy utilization efficiency of 54%.
Control Bifurcations in a Nonlinear Active Suspension System for System Design
Authors: Shukla Amit , Koo Jeong Hoi
Published: April 2008

Nonlinear active suspension systems are very popular in the automotive applications. They include nonlinear stiffness and nonlinear damping elements. One of the types of damping element is a magneto-rheological fluid based damper which is receiving increased attention in the applications to the automotive suspension systems. Latest trends in suspension systems also include electronically controlled systems which provide advanced system performance and integration with various processes to improve vehicle ride comfort, handling and stability. A control bifurcation of a nonlinear system typically occurs when its linear approximation loses stabilizability. These control bifurcations are different from the classical bifurcation where qualitative stability of the equilibrium point changes. Any nonlinear control system can also exhibit control bifurcations. In this paper, control bifurcations of the nonlinear active suspension system, modeled as a two degree of freedom system, are analyzed. It is shown that the system looses stability via Hopf bifurcation. Parametric control bifurcation analysis is conducted and results presented to highlight the significance of the design of control system for nonlinear active suspension system. A framework for the design of feedback using the parametric analysis for the control bifurcations is proposed and illustrated for the nonlinear active suspension system.
Influence of Carbon Nanotubes on the Physical and Mechanical Behaviours of Magnesium
Authors: Goh C. S. , Wei J. , Gupta M.
Published: April 2008

The powder metallurgy technique was used to synthesize magnesium reinforced with up to 0.3 weight percentage of carbon nanotubes (CNTs). The nanocomposites fabricated were extruded at an extrusion ratio of 20.25:1 and then characterized for their physical and mechanical properties. The influences of carbon nanotubes on the physical and mechanical properties of Mg were investigated. The thermomechanical property characterization shows an increase in thermal stability of the Mg nanocomposites with increasing amount of CNTs added. Mechanical property results reveal an improvement in yield strength, ductility and work of fracture with higher weight percentages of CNTs incorporated. An attempt is made to correlate the physical and mechanical properties with the increasing weight fractions of carbon nanotubes in pure Mg matrix.
Creep Life Prediction of 0.5%Cr-0.5%Mo-0.25%V Thick-Walled Cylinder Using New Multiaxial Approach
Authors: Ng Lawrence , Khosrow Zarrabi
Published: April 2008

A new method is proposed to predict the life of pressure components operating within the creep range. The method is based on exhaustion of the internal energy in the critical zones of the material. It is shown that the proposed method alleviates some of the major shortcomings of the existing methods yet it is simple enough to be readily applicable to industrial cases. Its predictions compared with a set of experimental data shows that the proposed approach may be used to predict the creep life with an accuracy of better than 2%.