bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Numerical Characterization of the Flow Around the Keel of a Yacht
Authors: Chaves Renata M. B. , Freire Atila P. S. , Alho Alexandre T. P.
Published: August 2009

The present work carries out a detailed comparison between numerical computations for the flow around the keel and the bulb of a sailboat and some newly obtained laboratory data. Two typical turbulence models are tested: the eddy-viscosity SST model and the second-moment model BSL-RSM-ω. Hot-wire anemometry (HWA) and particle image velocimetry (PIV) are used to characterize the flow around the keel and the bulb of a yacht. The experiments are conducted in a low speed wind tunnel. Measured flow parameters include the mean velocity profiles and second order moments. Both turbulence models are shown to perform well regarding mean velocity and global predictions. Turbulence data predictions, however, are shown to be erroneous by at least one order of magnitude.
The Effect of Installing Porous Refractory Panels on the Transient Start Up Performance of a Gas-Fired Reheating Furnace
Authors: Ward John , Tucker Robert J. , Correia-Eicher Sara A. C. , Chong Alex Z. S. , Rhine Jeff
Published: August 2009

The replacement of part of a conventional refractory lining in a furnace by a porous ceramic panel can enhance the thermal efficiency and increase the furnace throughput. If the hot furnace exhaust gases are passed through the panel (instead of leaving through the normal exhaust) heat is transferred, largely by convection, to the fine porous structure. Most of the heat which is recovered in the porous refractory in this fashion is then re-radiated back into the furnace chamber so that the overall radiative heat transfer to the load is substantially enhanced. The paper describes the development, validation and application of a mathematical model which simulates the installation of such a panel in an intermittently operated, gas-fired furnace heating steel bars to temperatures of approximately 1200°C. The overall model iteratively linked a sub-model of the flow and heat transfer through the porous section with a transient zone model of the radiation heat transfer in the furnace chamber. This procedure is then repeated sequentially throughout the period of the furnace operating cycle to predict the overall thermal performance of the furnace. The model was validated by measurements obtained during a series of tests on a gas-fired furnace. The predicted load temperatures and furnace energy consumptions were in good agreement with the corresponding measurements and indicated that reductions in energy consumption of up to 20% can be obtained depending upon the method of operating the furnace. Following the successful validation of the model it was then employed to predict the thermal behaviour of a small furnace heating steel bars or billets from a “cold start up”. The radiative heat transfer to the load was significantly enhanced throughout the heating period and this led to substantial improvements in the thermal efficiency and reductions in the time required to heat the load to its specified discharge temperature.
A Finite Element Model for Bending Buckling of Single Wall Carbon Nano-Tubes and Investigation of Geometrical Parameters on it
Authors: Hemmasizadeh Ali , Kamali Reza , Hadi Ehsan , Khandan Rasoul
Published: August 2009

Bending buckling behavior of single-walled carbon nanotubes (SWCNTs) is modeled by means of finite element method (FEM) and the relations between critical bending buckling curvature and geometrical parameters of nanotubes are determined. Elastic modulus and wall thickness of nanotubes are chosen in a way that elastic shell theory is capable of predicting mechanical properties of nanotubes. The effect of initial internal stress state through the shell thickness is investigated. Computed results are very close to the results of molecular dynamics simulation.
Molecular Dynamics Simulation for Bubble Nucleation of Water and Liquid Nitrogen in Explosive Boiling
Authors: Zou Yu , Huai Xiulan , Liang Shiqiang
Published: August 2009

Molecular dynamics simulation is carried out for the bubble nucleation of water and liquid nitrogen in explosive boiling. The heat is transferred into the simulation system by rescaling the velocity of the molecules. When heat is added into the molecular cluster, liquid initial equilibrium temperature and molecular cluster size can affect the energy conversion in the process of bubble nucleation. The potential energy of the system violently varies at the beginning of the bubble nucleation, and then varies around a fixed value. At the end of the bubble nucleation, the potential energy of the system slowly increases. In the process of bubble nucleation of explosive boiling, the lower initial equilibrium temperature leads to the bigger size of the molecular cluster. With more heat added into the system of the simulation cell, the potential energy varies in a larger range. The primary potential of water molecules includes Lennard-Jones potential energy and Columbic force caused by static charges of oxygen and hydrogen atoms. This is the reason why the bubble nucleation of water is different from that of liquid nitrogen. Pressure controlling is applied in the simulation of water, which makes the bubble more fully extended than that of liquid nitrogen.
Measurement of Dynamic Viscoelasticity of an Osteoblast Under Adhesive Condition Using a Piezoelectric Vibrator
Authors: Shiraishi Toshihiko , Onishi Takafumi , Morishita Shin , Takeuchi Ryohei
Published: August 2009

Bone cells are adaptive to surrounding mechanical conditions. Osteoblasts, one of bone cells, have been reported to be sensible to mechanical stimulation and change the generated bone mass. Viscoelastic properties of such cells are predicted to be related to this phenomenon in the view of mechanical dynamics. In order to find the effective stimulation on the bone formation, it is necessary to understand the viscoelastic properties of the cells. Especially in the case of bone cells, it is important to consider their adhesive condition because they attach on surfaces of bone matrices. In this study, we measured dynamic viscoelastic properties of a cultured osteoblast, MC3T3-E1, under adhesive condition. Using the experimental results, we derived a model for viscoelasticity of the cell and identified the value of each element in this model. The cells were seeded on a glass plate in a petri dish. After the cells were cultured for one day and adhered on the glass plate, it was vertically raised and fixed on a piezo actuator. The center of the cell surface was aspirated with an L-shaped micropipette to be held. The glass plate was moved with the piezo actuator. The load applied to the cell was obtained by measuring the deflection of the micropipette whose spring constant was calibrated after each test. Deflection of the micropipette and elongation of the cell were measured by captured image during the test. As a result, the dynamic viscoelasticity of the cells was measured and modeled, and the value of each element in this model was identified.
Thermal Performance Improvement of Through Silicon Via (TSV) Technology on 3-D Stack Packages
Authors: Kuo Wei-Shen , Wang Mingzong , Chen Eason , Lai Jeng-Yuan , Wang Yu-Po
Published: August 2009

With electronic package tends to be lighter, thinner and smaller, the stacking of the many chips in the 3-D stack packages become more and more popular package. However, the stacking of the multi-function chips in the 3-D stack packages will result in high thermal dissipation. Thermal management has turned into one of the most primary challenge of semiconductor designers. The new technology is required to remove the heat effectively. 3-D stacked package with Through Silicon Via (TSV) technology is developed for two chips in a package. Electrical connections in the silicon interposer are formed by TSV. The silicon interposer has better thermal conductivity than that without interposer, therefore the package thermal resistance is lower. In this paper, thermal evaluations on Flip-Chip Ball Grid Array (FC-BGA) packages were presented using CFD modeling technique. The evaluation topics covered impact of Through Silicon Via (TSV) and dummy bumps, various power consumption, die size and package size effects. Besides, the thermal performance of the package would be decided by thermal conductivity of under fill. Finally, thermal suggestions were concluded for designers to design in TSV arrangements to effectively dissipate hot source.
Model Based System Monitor Using Artificial Neural Networks (ANN)
Authors: Albers Albert , Wang Jiangang , Ott Sascha , Du¨ser Tobias , Lerspalungsanti Sarawut
Published: August 2009

Nowadays, with the integration of diverse mechatronic components, a mechatronic system is capable of performing more difficult and complex tasks. At the same time, it becomes more and more difficult to develop a system to ensure the safety of these complex mechatronic systems. This paper outlines a novel method for fault detection, which uses a neural network monitor based on a feed forward back propagation (FFBP) algorithm. The goal of this study is to develop a real-time capable method for detection of abnormal or faulty behavior of an automation system. An example is used to illuminate the capability of the neural network in modeling and real-time data in this work. Furthermore this method is validated on a test bed, which is developed at the institute of product development Karlsruhe (IPEK). This method will allow the monitor to detect critical state of the system due to unexpected influences in real-time, so that safety hazard to personnel and equipment caused by the fault can be prevented or mitigated.
Analysis and Development of a Magnetocaloric Pump for Electronic Cooling Applications Using a Mn-Zn Ferrite Ferrofluid
Authors: Gutierrez Jorge Gustavo , Riccetti Miguel
Published: August 2009

A device able to pump a fluid with no moving mechanical parts represents a very encouraging alternative since such device would be practically maintenance free. A magnetocaloric pump could achieve this purpose by providing a magnetic pressure gradient to a ferrofluid placed inside a magnetic field while experiencing a temperature change. If the temperature change is produced by extracting heat out of an element that needs refrigeration, coupling this generated heat with the magnetocaloric pump will result in a passive cooling system. For applications near ambient temperature the ferrofluid must have specific characteristics such as low “Curie temperature”, high pyromagnetic coefficient, high thermal conductivity and low viscosity. This work presents an analysis of the ferrohydrodynamic governing equations, emphasizing the importance of the Kelvin force in the magnetocaloric pump analysis. The general equations are simplified and scaled to show which parameters are important in the generation of the magnetic pressure gradient. Based on the scaling analysis, a variable magnetic field and a higher saturation magnetization is needed to generate a higher magnetic pressure gradient. The working fluid used is an aqueous Mn0.5Zn0.5Fe2O4 ferrite ferrofluid synthesized by the co-precipitation technique. This ferrite shows lower “Curie temperature” than commercially available magnetite. Important issues in the design of a magnetocaloric pump prototype with a variable magnetic field source are also discussed.
Experimental Investigation of Micro/Nano Heat Pipe Wick Structures
Authors: de Bock H. Peter J. , Varanasi Kripa , Chamarthy Pramod , Deng Tao , Kulkarni Ambarish , Rush Brian M. , Russ Boris A. , Weaver Stanton E. , Gerner Frank M.
Published: August 2009

The performance of electronic devices is limited by the capability to remove heat from these devices. A heat pipe is a device to facilitate heat transport that has seen increased usage to address this challenge. A heat pipe is a two-phase heat transfer device capable of transporting heat with minimal temperature gradient. An important component of a heat pipe is the wick structure, which transports the condensate from the condenser to the evaporator. The requirements for high heat transport capability and high resilience to external accelerations leads to the necessity of a design trade off in the wick geometry. This makes the wick performance a critical parameter in the design of heat pipes. The present study investigates experimental methods of testing capillary performance of wick structures ranging from micro- to nano-scales. These techniques will facilitate a pathway to the development of nano-engineered wick structures for high performance heat pipes.
Variable-Mass Thermodynamic Analysis of Drying Process
Authors: Xie Yingbai , Su Hang , Zhang Xuedong , Xu Zhouxuan
Published: August 2009

Drying is the complex process which involving simultaneous heat, mass and momentum transfer phenomena. The variable-mass thermodynamic viewpoint is introduced to analysis the drying process. For a closure heat pump drying equipment, variable-mass thermodynamic models based on the first law are constructed. Calculations on the rate of moisture removal and supply airflow are done based on the values of experimental data. The efficiency of drying process is calculated with the variable-mass and the classical thermodynamic method; the two methods have the same result. And the variable-mass thermodynamic analysis reveals that only under the rigorous conditions, drying can be treated as isenthalpic process.
A Droplet Based Microgripper for Microassembly
Authors: Vasudev Abhay , Zhe Jiang
Published: August 2009

A new droplet microgripper that can pick up and release micro objects by electrowetting is presented. Electrowetting is utilized to dynamically change the contact angle between the liquid bridge and the gripper surface to control the capillary lifting forces. A coplanar interdigitated gold electrode pair was employed to simplify the microfabrication. The lifting force generated by the microgripper was experimentally characterized. The pick and release routine were successfully demonstrated for various micro glass beads. The design, microfabrication and testing of the microgripper are presented.
The Sintered Porous Metal Media Development and Measurement of LHP Systems for Electronic Cooling Device
Authors: Sung Byung-ho , Choi Jeehoon , Ki Jaehyung , Yoo Junghyun , Seo Minwhan , Kim Chul-ju
Published: August 2009

Due to the continuous increase of power applied in electric device, the growing demand on cooling systems have led with using various cooling device to conduct the thermal management. As a new cooling device, a Loop Heat Pipe (LHP) system has been taken notice recently. The performance of the LHP systems depends mainly upon the operating performance of the wick structure should possess flow properties such as permeability, maximum capillary pressure and so on. However, expressions on packed metal spherical particles are not related with various particle shapes. In this work, therefore, an experimental apparatus was set up to measure the flow properties of sintered porous metal wicks manufactured with spherical, needled, and corn shape particles. The results of the such experiments gave very accurate and consistent.
Engaging Students in the Social Context of the Engineering Profession Through a Mock Congressional Hearing Exercise
Authors: Cunningham Patrick J.
Published: August 2009

This research project investigates the benefit of a mock Congressional hearing exercise in facilitating students’ reflections on the role of engineers and scientists in society and government and how technological solutions are shaped by society and the government. The benefit is assessed by student survey responses and by instructor experiences throughout the exercise. The hypothesis is that the mock Congressional hearing will prove to be an active and engaging exercise that will result in greater awareness of the interaction of science and technology with society, greater confidence processing these issues, and increased knowledge of where to look for information on contemporary technological issues. In evaluation of the exercise, students noted that their awareness of the social and environmental dimensions of technical issues improved. They also indicated that they were introduced to several governmental websites for Congress and the agencies relevant to their topic. However, students did not feel that the mock hearings contributed significantly to their confidence in performing analysis of current technical issues facing society. Improvements for future mock hearing exercises, such as tying it more closely to the course content, are also presented.
Blind Source Separation Using a Neural Network
Authors: Niino Yukihito , Shiraishi Toshihiko , Morishita Shin
Published: August 2009

Humans are able to well recognize mixtures of speech signals produced by two or more simultaneous speakers. This ability is known as cocktail party effect. To apply the cocktail party effect to engineering, we can construct novel systems of blind source separation such as current automatic speech recognition systems and active noise control systems under environment noises. A variety of methods have been developed to improve the performance of blind source separation in the presence of background noise or interfering speech. Considering blind source separation as the characteristics of human, artificial neural networks are suitable for it. In this paper, we proposed a method of blind source separation using a neural network. The present neural network can adaptively separate sound sources on training the internal parameters. The network was three-layered. Sound pressure was output from two sound sources and the mixed sound was measured with two microphones. The time history of microphone signals was input to the input layer of neural network. The two outputs of hidden layer were corresponding to the two sound pressure separated respectively. The two outputs of output layer were corresponding to the two microphone signals expected at next time step and compared with the actual microphone signals at next time step to train the neural network by a backpropagation method. In this procedure, the signal from each sound source was adaptively separated. There were two conditions of sound source, sinusoidal signals of 440 and 1000 Hz. In order to assess the performance of neural network numerically and experimentally, a basic independent component analysis (ICA) was conducted simultaneously. The results obtained are as follows. The performance of blind separation by the neural network was higher than the basic ICA. In addition, the neural network can successfully separate the sound source in spite of the position of sound sources.
A Particle Size-Shape-Dependent Three-Phase Two-Step Mori-Tanaka Method for Studying the Interphase of Polymer/Clay Nanocomposites
Authors: Li Yaning , Waas Anthony M. , Arruda Ellen M.
Published: August 2009

The enhancement of polymers by nano fillers can improve their mechanical properties beyond those achieved in macro, meso and micro composites with the same volume fraction, particle morphology and particle aspect ratio. The basic enhancement mechanism is analogous to traditional composite mechanics and can be partly explained by classical composite theories. However, the much higher enhancement efficiency of fillers at the nano scale, i.e. the particle size effects, can not be explained by classical composite mechanics theories alone. The interphase is a main structural feature of nano composites within which a significant surface-to-volume ratio is achieved, and it plays a crucial role in understanding the size effects and enhancement mechanisms of nanocomposites. In this investigation, a semi-empirical method of determining the interphase thickness and elastic properties is developed by a combination of finite element simulation, thermodynamic formulation and experimental calibration and applied to LBL (layer by layer) polyurethane-clay nanocomposites studied by Podsiadlo, et al. [1, 2] and Li, et al. [3]. Based on this study, the classical two-phase Mori-Tanaka model is extended into three-phases by introducing the interphase through a two-step procedure using the concept of an effective matrix. It is shown that this two-step Mori-Tanaka method can predict the brittle to ductile transition in terms of interphase overlap. Most importantly, this approach overcomes a serious drawback of the classic Mori-Tanaka model: size-independency. Particle size effects as well as shape effects and their interactions can be studied as applications of this method.
Thermal Characterization of Silicon Carbide Nanowire Films
Authors: Castillo Eduardo , Choudhury Sadia , Shim Hyun Woo , Kuppers Jaron , Huang Hanchen , Borca-Tasciuc Diana-Andra
Published: August 2009

This paper reports on thermal characterization of SiC nanowire films on alumina substrate. The SiC nanowires films were synthesized via carbothermal reduction by thermal evaporation of silica and graphite powders using a high temperature alumina tube furnace. Structural characterization showed that nanowires have a core-shell structure, with a core of single crystal SiC of ∼50 nm in diameter and an amorphous shell of silicon oxide of ∼10 nm in thickness. Prior thermal measurements as-deposited SiC nanowires were compacted into more dense films via capillary coalescence. The effective thermal conductivity in the direction perpendicular to the film was determined employing a steady-state experimental method in conjunction with one-dimensional heat transfer modeling. Preliminary results suggest that these films have a very low thermal conductivity, in the range of 0.1W/mK. The low thermal conductivity may be due to intrinsic structure of the nanowire film such as porosity and large number of interfaces between the SiC nanowire core and its outer oxide layer as well as thermal contact resistance at nanowires junctions.
A Dynamical Systems Approach to Stability Tracking of Treadmill Running
Authors: Adam Christopher S. , Berry Ian R. , Short Kevin M. , Saly Diana I.
Published: August 2009

Traditional analysis of running gait utilizes averaged biomechanical data from several strides to generate a mean curve. This curve is then used to define the average picture of a runners gait. However, such measures are frequently accompanied by time normalization, which results in a loss of temporal variations in the gait patterns. An examination of stability requires analysis of both time and position, therefore loss of such information makes stability analysis difficult. On the contrary, the use of a dynamical systems approach for gait analysis allows for a better understanding of how variations in gait pattern change over time. In the current study runners ran on a treadmill, with both a flat and uneven surface, at a self selected speed. Three-dimensional position data was captured for 11 different anatomical locations at a frequency of 120 Hz using a Qualysis motion capture system. The data was first shifted to a lumbar coordinate system to account for low frequency drift attributed to the subjects’ drift on the treadmill. Since all of the markers were rigidly connected, via the subject, the movements and variations of certain components of the 33-dimensional measurements were not independent. As a result, it was possible to reduce the dimensionality of the transformed data using singular value decomposition techniques. The primary components were then analyzed using the method of delay embeddings to extract geometric information, revealing the natural structure found in the data as a result of the periodicity of each running stride. A nearest neighbor mean stride orbit was then computed to create a reference orbit, so that deviations from the mean stride orbit can be measured. The expectation was that a more stable running configuration would lead to smaller deviations from the mean stride orbit. On-going work that will be reported includes: (i) analysis of running stability related to the reference stride comparator, (ii) compensation of lumbar centroid dynamics, (iii) reconstructions using one dimension from the lumbar centroid transformed data, and (iv) consideration of transients, fatigue, adaptation, etc.
Open Production: A New Broker-Based Approach to Interactive Value Creation and User Manufacturing
Authors: Redlich Tobias , Bruhns Franz-Ludwig
Published: August 2009

Business strategies and organization are subject to a permanent adjustment due to the discontinuity of the markets. Mass production, in particular, and a focus on tayloristic principles, in general, no longer seem to be the right choice within this context. Rather, the increasing importance of customization and the transition to an information-based economy leads to the question whether the currently enshrined distinction between producer and consumer is still appropriate. The authors of this paper assume that the key to dealing with complex economic turbulences can be found in the implementation of a new form of coordination, in which the strict separation between producer and consumer is repealed. That requires changeability at all levels of production systems as it is inherent to the approach of “Open Production” that will be introduced with this paper. While Open Production encompasses recent concepts like “Open Innovation”, “Mass Customization”, and “e-Manufacturing”, the three “pillars” of Open Production are openness, individualization and web integration. Additionally it implies a superior broker system that coordinates the information and material flows between the stakeholders of open production. This represents a completely new, but profoundly changeable form of coordination integrating the customers into production directly, where as the previously static separation into a customer and a corporate domain and the division of labor and competence is dissolved.
Gastroesophageal Reflux 2D and 3D Steady State CFD Simulations
Authors: Odie K. D. , Moloney K. W. , McMahon B. P. , Gregersen H.
Published: August 2009

Gastro-Esophageal Reflux Disease (GERD) is a condition which affects up to 20% of the adult US population on a weekly basis. It is a condition where acid is allowed to flow from the stomach and into the esophagus where it causes damage to the local tissue. In chronic cases the condition can lead to cancer. Dysfunction of the Esophagogastric Junction is indicated as a primary cause. The recently developed Functional Lumen Imaging Probe (FLIP) is designed for assessment of the EGJ. It measures the cross sectional area at eight locations through the junction. This data has been used to construct a series of computational fluid dynamic simulations. These simulations showed a jet of fluid which squirts into the esophagus under the gastric pressure. This jet corresponds with previously gathered anecdotal evidence. The centerline velocities of this jet were measured and this suggested that the jet could travel up to 20 times the minimum diameter of the EGJ into the esophagus before decelerating to 25% of its original velocity. This means that if an EGJ was curved then this jet could impinge on the walls causing a localized area of increased damage to the mucosa compared to the surrounding tissue.
Design and Build of a Portable Instrumentation Elevation Tower
Authors: Jernigan Johnathan , Moore Christopher , Rizzo Ron , Schmaltz Kevin
Published: August 2009

The Western Kentucky University (WKU) Department of Engineering is collaborating with National Park Service – Inventory and Monitoring scientists to support National Park Service (NPS) cave environment and ecosystems research. The NPS, together with the United States Geological Survey, provided the funding that has allowed WKU Engineering students, working with WKU faculty and staff and NPS scientists, to design, build, test and deliver two transportable instrumentation lift systems. Each lift tower has a stationary top platform and a secondary platform capable of continuously raising and lowering instrumentation over extended, unattended periods. NPS-owned instrumentation on the platforms collects air temperature, relative humidity and air velocity data, storing results to NPS-owned devices located on or below the tower. NPS scientists will use the system to gather more accurate data on the quality and movement of air within cave passages and develop predictive models of the environment. The new system will allow measurements as high as 30 feet and make long-term data collection feasible. A variety of design challenges were met by the students working on the project. Portability, flexibility and weight reduction were achieved through a collapsible aluminum base securing the tower, with three-foot PVC sections to build varying tower heights. Stability was accomplished with a tensioning cable system and a gripping mechanism integrated into the base to secure the incomplete tower. Cable spool design and data collection programming achieved positioning accuracy of the moving platform. In addition to satisfying functional needs, the towers were also designed to avoid damage to cave surfaces and meet challenging operating requirements. Tower components are reasonably lightweight and durable, components are shock-resistant, moisture-resistant, easy to dry and clean, and non-corroding. The design modularity facilitates transport by two NPS personnel using duffle bags, and is easy to set up and move. The towers support multiple instruments weighing as much as 10 pounds, can be modified to support instruments in varied configurations, and can be repaired in-house by NPS personnel. The towers were designed and tested to assure user friendly, reliable operation. Tower stability, ease of tower construction, accuracy of platform movement, and required battery life issues were solved by the students.
Mechanical Strength of Copper-Silicon Interface of Planar Metallization Power Modules
Authors: Sinha K. , Dasgupta A. , Beaupre R. , Gowda A.
Published: August 2009

Planar metallization interconnection is an advanced approach to power module packaging. One advantage of this approach is the ability to interconnect a large number of small devices without wirebonds. The structure consists of multiple layers of dissimilar materials including, copper, kapton, silicon, direct bonded copper (DBC) and solder die attach. When subjected to power or thermal cycling, the difference in thermal expansion of the various layers causes interlaminar stresses and risk of delamination. In particular, potential high risk regions include the interface where plated copper vias make electrical connection to the silicon semiconductor device through thin adhesion and barrier metal films, because of the large CTE difference between them. This study examines the mechanical strength of this copper-silicon interface. The delamination mechanisms of a bimaterial interface can be classified into three types: opening mode, sliding mode, and twisting mode. The first two modes are explored in this study using specially designed experiments. The third mode does not contribute to thermo-mechanical stresses at the copper-silicon interface due to surrounding mechanical constraints and is not addressed. 3D finite element analysis of this via structure is combined with the above experimental results, to qualitatively assess the thermomechanical stress margins in a typical operating environment. Identification and understanding of these failure modes and mechanisms enables to better via designs for reliable operation of planar metallization power modules.
Vibration Control With Magnetically Mounted Piezoelectric Actuators
Authors: Collinger J. C. , Messner W. C. , Wickert J. A.
Published: August 2009

A novel vibration control method utilizing magnetically mounted piezoelectric actuators is described. Piezoelectric actuators are bonded to permanent magnets, which are attached to the surface of a steel cantilever beam through their magnetic attraction. The magnetic-piezoelectric control mounts are an alternative to traditional epoxy attachment methods for piezoelectrics which allows easy in-the-field reconfiguration. In model and laboratory measurements, the beam is driven through base excitation and the resonant shunt and synchronized switching techniques are applied to two magnetic-piezoelectric control mounts to attenuate vibration. The coupled system is discretized using a Galerkin finite element model that incorporates relative axial motion between the beam and the mounts, which is governed by the sticking contact stiffness per unit length of the beam-magnet interface. The control mounts are designed using a magnetic array configuration which increases the attraction force for a given magnet thickness. Results show that the magnetic-piezoelectric control mounts provide attenuation, while also providing the flexibility to easily adjust the actuators along the length of the beam.
Law of the Wall Formulation for Separating Flow Over a Rough Hill
Authors: Loureiro Juliana B. R. , Silva Freire Atila P.
Published: August 2009

Simple asymptotic arguments together with the mixing length hypothesis are used to derive a local analytical solution that accounts for adverse pressure gradient and separation effects for flows over rough walls. To model the wall roughness effects, a new parametrization method is advanced for the proposed solution in terms of the friction velocity (u∗), the local pressure gradient (∂xp) and the roughness length (z0). The near-wall solution and the parametrization function are validated against some DNS (smooth wall flow) and LDA (smooth and rough wall flows) data. The experiments were carried out in a water-channel and the extent of separated flow was made to vary as a function of the roughness and the Reynolds number. Global optimization algorithms based on four different direct search methods are used to assess the relevant flow parameters. The analysis includes regions of attached as well as separated flow. Forty two velocity profiles are tested against the proposed expression for the parametrization function, including two profiles that satisfy the solution of Stratford. The present theory furnishes consistent results that might be implemented in predictive numerical models for complex flows.
Generation and Transport of Bubbles in a Microfluidic Device
Authors: Xiong Renqiang , Chung Jacob N.
Published: August 2009

In this paper we used high speed recording to characterize segmented micro-scale air bubble generation in a T-junction and bubble transport in a serpentine micro-channel fabricated in a standard silicon wafer.
Math-Based Control Logic Development for Automotive Industrial Applications: Issues, Challenges and Solution
Authors: Yuan Chengyin , Biller Stephan , Gu Fangming , Liu Jing
Published: August 2009

Intensive global competition forces automotive manufacturers to develop and produce vehicles at lower cost with shorter life cycles and better quality. Faster Vehicle Development Process (VDP) improve profitability by reducing the time and cost related to designing, engineering and launching a new vehicle model. More importantly, it enables automotive makers to react quickly to trend shift in market, e.g., recent shift from SUV (Sports Utility Vehicle) to small fuel efficient vehicle. However, the current manufacturing system design (especially control logic design), key part of VDP, is labor intensive and time consuming, and design quality and performance are highly dependent on the designer’s knowledge and experience. This paper discusses the issues and challenges identified in the current logic development process. A new method to automatically generate control logic using formal method is proposed. In this approach, the required information is collected and modeled as Automata. Possible control logic sequences are then calculated and the optimal one is identified from a set of alternative solutions. This paper also discusses how to implement and integrate the proposed method into the automotive manufacturing engineering process. The method is applied to automotive industry examples, and results are presented. Based on these case studies, this math-based approach can improve the quality of controls logic codes, and reduce ramp-up time and engineering cost significantly.
Dynamic Simulation Model of a Hydraulic Valve Utilizing the Ho¨rbiger Plate Principle and Piezoactuation to Achieve High Bandwidth and Flow Performance
Authors: Branson David T. , Wang Fengcai , Bowen Chris R. , Keogh Patrick S.
Published: August 2009

In order to increase hydraulically actuated machine system performance, valves with high performance bandwidths and large flow rates at low pressure drops are needed. While high flow rates were previously achieved using either very large spool strokes and/or diameters that would hinder valve performance, research is underway on a valve incorporating the Ho¨rbiger plate principle. This principle utilizes multiple metering edges to allow for increased flow at specified pressure drops and using small spool displacements. The valve configuration is then directly actuated using a piezoactuator to further increase valve dynamic response. This paper examines the development of a dynamic valve model using computational fluid dynamic simulations to predict fluid inertance parameters, and combines this with models for the piezoactuator, power amplifier, supply flow, fluid squeeze forces, end stop response, and valve mechanical components. Steady state and dynamic simulations of the valve are then evaluated.
Fluid-Dynamic Analysis of Motorbike Race Engine Injection System
Authors: Senatore Adolfo , Cardone Massimo , Buono Dario , Manganelli Mario
Published: August 2009

The working conditions of all components of a competition engine are very hard: they must assure durability and reliability during a race where the running conditions changes very rapidly. The injection system of a competition engine must ensure a great amount of injected fuel and a great precision about control (timing and quantity) of the injected fuel. In this paper a simulated analysis of a competition engine injection system is shown. The engine was developed by the race team of Aprilia and it will be employed in 4 stroke racing application. The simulation model of the injection system was accurately validated by experimental data. The model was performed by a mono-dimensional and commercial code, which ensures a good reliability and fast calculation times. The model was performed during the engine development, so in the beginning of this activity only design data was used to realize the model. In the first step only experimental data performed on system components by their own manufacturers was used to calibrate the model then, when the engine was realized and tested on an experimental bench, the model was validated by dedicated experimental test performed on the injection system. The model was used to test several design solutions, in particular it was used during the design and the choice of the injectors, furthermore it was used to test several system configurations. This model is an interesting example of a modellistic approach and methodology that could be employed during the development of a new engine and its components of high specific power.
Microfluidic Continuous Particle Separation via AC-Dielectrophoresis With 3D Electrodes
Authors: C¸etin Barbaros , Li Dongqing
Published: August 2009

In this paper, we are presenting the numerical simulation of a novel, simple microfluidic device for continuous separation of the particles according to their size. The device is composed of a straight rectangular channel connecting two inlet reservoirs to two exit reservoirs. Two asymmetric, straight, 3D electrodes are embedded inside the channel along the wall to create a non-uniform electric field for the DEP separation. The separated particles are collected at the different exit reservoirs. Main flow is induced by the pressure difference between the inlet and the exit reservoirs. The region affected by the electric field gradient is confined within the vicinity of the electrodes. Therefore, the undesired effects of the electric field on the system are minimized.
Fresnel Lenses Design by Acoustic Transmission Line
Authors: Zhang Shu , Fang Nicholas
Published: August 2009

We proposed an approach to construct a 2D Fresnel lenses by acoustic network. This lens is composed of an array of Helmholtz resonators. The resonance at individual resonators results in effective focusing even the plate has subwavelength thickness. The FEM simulation results presented the ultrasonic wave propagation through the lenses together with the resulting diffraction pattern.
Multi-Objective System Optimization of Engine Crankshafts Using an Integration Approach
Authors: Albers Albert , Leon Noel , Aguayo Humberto , Maier Thomas
Published: August 2009

The ever increasing computer capabilities allow faster analysis in the field of Computer Aided Design and Engineering (CAD & CAE). CAD and CAE systems are currently used in Parametric and Structural Optimization to find optimal topologies and shapes of given parts under certain conditions. This paper describes a general strategy to optimize the balance of a crankshaft, using CAD and CAE software integrated with Genetic Algorithms (GAs) via programming in Java. An introduction to the groundings of this strategy is made among different tools used for its implementation. The analyzed crankshaft is modeled in commercial parametric 3D CAD software. CAD is used for evaluating the fitness function (the balance) and to make geometric modifications. CAE is used for evaluating dynamic restrictions (the eigen-frequencies). A Java interface is programmed to link the CAD model to the CAE software and to the genetic algorithms. In order to make geometry modifications to our case study, it was decided to substitute the profile of the counterweights with splines from its original “arc-shaped” design. The variation of the splined profile via control points results in an imbalance response. The imbalance of the crankshaft was defined as an independent objective function during a first approach, followed by a Pareto optimization of the imbalance from both correction planes, plus the curvature of the profile of the counterweights as restrictions for material flow during forging. The natural frequency was considered as an additional objective function during a second approach. The optimization process runs fully automated and the CAD program is on hold waiting for new set of parameters to receive and process, saving computing time, which is otherwise lost during the repeated startup of the cad application.
Molecular Dynamics Simulations of Thermal Interactions in Nanoscale Liquid Channels
Authors: Kim BoHung , Beskok Ali , Cagin Tahir
Published: August 2009

Molecular Dynamics (MD) simulations of nano-scale flows typically utilize fixed lattice crystal interactions between the fluid and stationary wall molecules. This approach cannot properly model thermal exchange at the wall-fluid interface. Therefore, we use an interactive thermal wall model that can properly simulate the flow and heat transfer in nano-scale channels. Using the interactive thermal wall, Fourier law of heat conduction is verified for the 3.24 nm channel, while the thermal conductivity obtained from Fourier law is verified using the predictions of Green-Kubo theory. Moreover, temperature jumps at the liquid/solid interface, corresponding to the well known Kapitza resistance, are observed. Using systematic studies thermal resistance length at the interface is characterized as a function of the surface wettability, thermal oscillation frequency, wall temperature and thermal gradient. An empirical model for the thermal resistance length, which could be used as the jump-coefficient of a Navier boundary condition, is developed.
Advanced Computational Modeling of Steady and Unsteady Cavitating Flows
Authors: Li Huiying , Kelecy Frank J. , Egelja-Maruszewski Aleksandra , Vasquez Sergio A.
Published: August 2009

The numerical simulation of steady and unsteady cavitating flows presents unique challenges in the development of robust numerical methodologies. The major difficulties are associated with the large density variations due to the phase change processes, and the modeling of liquid-vapor mass transfer (along with potentially strong interfacial heat transfer). The multiphase cavitation modeling approach described in this paper has been found to be capable of addressing these issues in an accurate and robust fashion, and is therefore suitable for inclusion in an advanced general purpose CFD solver. In the present approach, cavitation can be modeled within the framework of either the multiphase mixture model or the Eulerian multifluid model. The governing equations are the mixture (mixture model) or phase (Eulerian multifluid model) momentum, energy, turbulence, and phase volume fraction equations. The liquid-vapor mass transfer (evaporation and condensation) is modeled using two baseline cavitation models: Schnerr-Sauer model, and Zwart-Gerber-Belamri model. An advanced numerical scheme has been developed for solving the model equations which can handle large liquid-vapor density ratios, provide for mass transfer source terms in phase volume equations, and address the coupling between the phase change rates and the pressure correction equation. In addition, the cavitation models have been extended to compressible multiphase liquid and vapor flow regimes, and to problems involving convective heat transfer. The numerical algorithm has been implemented in an advanced, general-purpose CFD code, FLUENT, and validations have been carried out for a range of steady-state and unsteady flows, including a 2D axisymmetric orifice, a 3D fuel injector, a radial liquid pump, and a vane pump. The results demonstrate that the cavitation models are able to correctly predict the location and size of vapor bubbles, pressure distributions, and bulk flow parameters. Tests also indicate that the present implementation is both fast and robust, as compared to previous approaches. For unsteady simulations, the method can employ large time steps (limited only by physical or mesh motion considerations), making it efficient for unsteady flows driven by either boundary conditions or mesh motion.
A Formal Approach on Specification Modeling to Support Industrial PLC Program Verification
Authors: De Soumen , Sethuraman Nagarajan , Yuan Chengyin
Published: August 2009

Intensive global competition requires the automotive manufacturers to launch new vehicle models with a shorter launch time, better quality, lower cost and more customization. One of the key enablers for achieving these objectives is to have an efficient & error-free manufacturing automation system which is typically controlled by Programmable Logic Controllers (PLC). The current PLC logic code testing process in automotive industry is usually performed manually by individual engineer, and the overall testing quality highly depends on the engineer’s expertise and experience. The PLC logic code testing normally consists of two parts, testing requirements (specification) and testing methods. One of the major hurdles for applying rigorous testing methods on PLC logic verification in industry is the lack of formal testing specifications. The current PLC testing specifications and requirements are documented in various formats, such as sequence of operation document, process instrument diagram, wiring diagrams, and time motion diagrams, etc. These varied documents cannot be directly used for control logic testing and require a better alternative. Formal methods, the latest technology widely used in software testing, is an approach selected for generating comprehensive test cases to ensure the correctness and consistency of PLC programs. This paper presents a novel approach for specifying the expected behavior of the already implemented industrial PLC code. The generated formal specification models can work with math-based logic verification tool to facilitate the usage of formal verification in manufacturing automation control. The specification modeling methodology contains all the required information from different logic design and testing phases, such as process sequence, wiring information, logic pattern, code comments, and domain knowledge, etc. And the statecharts is used as model formalism, because of its capability to model states hierarchically and provide a better visual representation.