bluuebunny/crossref_metadata_2025 huggingface dataset:
Realtime Ultrasound Prostate Young’s Modulus Reconstruction Technique Using a Full Inversion Approach
Authors: Mousavi Seyed Reza , Samani Abbas
Published: May 2012

In this work, we present a real-time prostate elastography reconstruction technique which incorporates an accelerated method of tissue stress calculation in its algorithms. The accelerated FE method uses a database of prostate-tumor configurations obtained from imaging. These configurations undergoing specific mechanical loading, e.g. US probe, are modeled and analyzed using conventional FEM to obtain the corresponding stress fields. Principal component analysis (PCA) is used to obtain the main modes of shape and stress fields. As such, the shape and stress fields can be described by these main modes weighted by a small number of weight factors. Next, an efficient mapping technique is developed to relate the weight factors of shape to those of the stress fields. We used Artificial Neural Network (ANN) and PCA based regression for this mapping. Once the mapping function is obtained it can be used for analyzing prostate shapes not included in the database. For a typical prostate, our results indicate that analysis using our technique takes less than 0.1 seconds on a desktop computer irrespective of the model size, while the maximum stress error is less than 5% per element. This mapping is then used for our novel real-time Young’s modulus reconstruction technique in which prostate and tumor moduli are updated iteratively using strain images acquired from an ultrasound imaging system and stress field estimated with the proposed method. Results of elastography show that relative Young’s moduli can be reconstructed fairly accurately.
Prestressed Harmonic Simulation of Electrostatic Microresonator With Proper Orthogonal Decomposition
Authors: Binion David , Chen Xiaolin
Published: May 2012

Due to its ease of implementation, electrostatic operation is one of the most common actuation/sensing techniques for micro-electro-mechanical-systems (MEMS). One such MEMS device is an electrostatic microresonator which is used to generate or filter signals. MEMS resonators are operated by pre-stressing the structure with a large bias voltage and then applying a small magnitude harmonic voltage. Accurate simulation requires models that describe the dynamic frequency response while accounting for stress stiffening. Finite Element Analysis (FEA) has widely been used to obtain accurate simulations of MEMS devices, however, a dense FEA mesh may be required resulting in computationally demanding models. To improve the computational efficiency, Model Order Reduction methods have regularly been used. In particular, Proper Orthogonal Decomposition (POD) has witnessed an increase in MEMS simulation. In this paper, POD has been investigated and implemented to model the dynamic behavior of a microresonator. An FEM model of a microresonator beam structure was produced and POD was employed to simulate the pre-stressed frequency response of the device. A pre-stressed harmonic simulation was performed using a full FEM model for comparison. It was found that the reduced model and full model responses were well matched while the computational time was drastically reduced through the use of POD.
Wave Energy Converter Performance Modeling and Cost of Electricity Assessment
Authors: Jarocki Dmitri , Wilson James H.
Published: May 2012

California is experiencing a rapid increase in interest for the potential of converting ocean waves in into carbon-free electricity. Numerous applications have been submitted for the permitting of such renewable energy projects; however the profitability, practicability, and survivability have yet to be proven. Wave energy conversion technology has steadily matured since its naissance in the 1970’s, several wave energy power installations currently exist, and numerous plans for commercial power plants are in the works on the shores of multiple continents. This study aims to assess the economic viability of two proposed commercial wave energy power plant projects on the Central California Coast. A hypothetical 25 MW capacity wave energy plant located at a site located 5 nautical miles off of Point Arguello, in Santa Barbara County is compared to a similar site 5 nautical miles off of Morro Bay, in the County of San Luis Obispo. The Pacific Gas and Electric Company and Green Wave Energy Solutions, LLC have proposed full-scale commercial wave power plants at these sites, and are currently undergoing the federal permitting processes. Historical wave resource statistics from 1980 to 2001 are analyzed with performance specifications for the AquaBuOY, Pelamis P1, and WaveDragon wave energy converters (WECs) to calculate the annual electrical output of each device at each site. Sophisticated computer modeling of the bathymetric influence on the wave resource at each site is presented using the program Simulating Waves Nearshore (SWAN) developed by the Delft University of Technology. The wave energy flux, significant wave height, and peak period are computed at each site for typical summer and winter swell cases, using seafloor depth measurements at a 90 meter grid resolution. The economic viability of commercial electricity generation is evaluated for each WEC at each site by the calculation of the net present value of an estimated 25-year project life-cycle, the internal rate of return, and the required cost of electricity for a 10-year project payback period. The lowest required price of electricity is $0.13/kWh and occurs at the Point Arguello site using the AquaBuOY WEC. The highest annual capacity factor is 18% using the Pelamis WEC. The net present value and internal rate of return calculations suggest that the AquaBuOY WEC is profitable at both sites for electricity prices above $0.14/kWh. Shallow water wave propagation SWAN modeling demonstrated favorable wave energy flux states for WEC operation and power generation.
Effect of Mechanical Alloying and Equal Channel Angular Extrusion Consolidation on the Structure and Properties of Tungsten Carbide-Cobalt Alloy
Authors: Srinivasan Malur N. , Ramakrishnan Kannan
Published: May 2012

Tungsten carbide-cobalt (WC-Co) materials are widely used today in the area of heavy duty machining (tool bits), in cold-forming dies and in the oil field industry (drill bits). Limited ductility is exhibited by conventionally produced WC-Co parts because of the presence of a high volume fraction of coarse WC particles in a soft cobalt matrix. Recent investigations have indicated that nanostructured WC-Co parts can attain up to twice the hardness values of conventional parts with coarse microstructure. With this background in view, the authors conducted an investigation to produce nanostructured WC-Co powder using mechanical alloying in an attritor and consolidate the powder through equal channel angular extrusion (ECAE) rather than conventional powder metallurgy technique, into bulk billets. An experimental plan based on 23 factorial experimental design was used to determine the effect of mechanical alloying variables, namely, milling time, milling speed and ball-to-powder ratio on the microhardness of billets produced using ECAE. The significance of these variables was examined with respect to the average microhardness of annealed WC-Co samples. The combination of the variables that was most beneficial to the formation of desired microstructure (nanocrystalline) and good hardness was then established. X-ray diffraction and scanning electron microscope (SEM) analysis were performed to determine the composition and grain size to give a better insight into the microstructure developed under different combination of the variables. It is hoped that the results of this investigation will help to develop the technology to produce superior quality WC-Co parts such as inserts, seats and dies required by the oil tool industry.
An Inverse Problem for the Mechanical Characterization of Steels From the Taylor Test
Authors: Hernandez C. , Maranon A. , Ashcroft I. A. , Casas-Rodriguez J. P.
Published: May 2012

Material characterization procedures are often complicated processes. In particular, dynamic material characterization usually requires many complicated and expensive tests. One of the tools used to characterize the behavior of materials under dynamic loading is the Taylor impact test. In this experiment, a flat-ended cylinder of initial uniform cross-sectional area is fired at a rigid target. The terminal geometry of the deformed cylinder is used to determine the material strength at different strain rates. This paper presents the formulation and solution of a first class inverse problem for the identification of the kinematic hardening material model from a Taylor impact test of a steel cylinder. The inverse problem is formulated as an optimization procedure for the determination of the optimal set of the model constants. The input parameter of the procedure is the final shape of a Taylor impact test specimen, in terms of central geometric moments, at a given impact velocity. The output parameters are the material model constants, which are determined by fitting the final shape of a numerically simulated Taylor specimen to the final shape of the experimental specimen. This optimization procedure is performed by a real-coded genetic algorithm. The paper includes a numerical example of the characterization procedure for a steel 1018 Taylor specimen of 8 mm diameter and 20 mm length, impacted at a velocity of 250 m/s. This simulation demonstrates the performance of the algorithm and the ability to estimate the kinematic hardening material model constants.
Enhancement of Solution Wetting and Heat Transfer on Horizontal-Tube, Falling-Film Evaporator Using Porous-Layer Coating
Authors: Lee Sangsoo , Park Chanwoo
Published: May 2012

An experimental study using a porous-layer (wick) coating on a horizontal-tube, falling-film evaporator was conducted to investigate the solution wetting of evaporator tubes and its effects on the evaporator performance. The partial solution wetting and the local dry-out on the evaporator tubes are the commonly encountered problems for the horizontal-tube, falling-film evaporator. In this study, the porous-layer coating was used in an attempt to enhance the solution wetting on the tubes and thus the evaporator performance. An experimental setup was built to measure the solution wetting and the performance of the evaporators using micro-scale hatched tubes (baseline design) and porous-layer coated tubes. Distilled water was used as the solution and the heating fluids. The solution wetting and the falling-film flow modes were visually observed in the range of the solution Reynolds number from 6 to 61. The evaporator using the micro-scale hatched tubes had the partial solution wetting on the tubes in the range of the solution Reynolds number considered for the study. In contrast, the evaporator using the porous-layer coated tubes showed the complete solution wetting which was confirmed by a visual inspection. The evaporator performance was evaluated by a thermal resistance analysis for the ranges of the solution and the heating fluid Reynolds numbers from 18 to 154 and from 3070 to 7270 respectively. The evaporation thermal resistances for the micro-scale hatched and the porous-layer coated tubes were increased as the solution flow rates were increased. The evaporation heat transfer coefficients for the micro-scale hatched tubes were higher than those for the porous-layer coated tubes. However, the evaporation thermal resistances with the porous-layer coated tubes were lower than those with the micro-scale hatched tubes because the complete solution wetting was achieved using the porous-layer coating.
Design of a High-Bandwidth XY Nanopositioning Stage for High-Throughput Micro/Nano Manufacturing
Authors: Polit Sebastian , Dong Jingyan
Published: May 2012

A high natural frequency (open-loop bandwidth) is a critical requirement for nanopositioners in high-throughput nanomanufacturing and nano-metrology applications. This paper presents the design and analysis of a high-bandwidth nanopositioning XY stage. The monolithic stage design has two axes and each axis is comprised of a doubly-clamped beam and a parallelogram hybrid flexure with complaint beams and circular flexure hinges. The doubly-clamped beam that is actuated by a piezoelectric actuator acts as a linear prismatic axis. The parallelogram hybrid flexures are used to decouple the actuation effect from the other axis. The mechanism design decouples the motion in the X and Y directions and restricts parasitic rotations in the XY plane while allowing for an increased bandwidth with linear kinematics in the operating region (or workspace). Kinematic and dynamic analysis shows that the mechanical structure of the stage has decoupled motion in XY direction, while achieving high bandwidth and good linearity. Finite element analysis is adapted to verify the dynamic responses from theoretical analysis. The stage is actuated by piezoelectric stack actuators, and two capacitive gauges were added to the system to build a closed-loop positioning system. The results from frequency test show that the resonation frequencies of the two vibrational modes are over 8K Hz. The stage is capable of about 15 microns of motion along each axis with a resolution of about 1 nanometer. Due to parallel kinematic mechanism design, a uniform performance is achieved across the workspace. A PI controller is implemented for the stage and a high closed-loop bandwidth is obtained.
Analysis and Design of a Nano-Electromechanical Vibration Sensor
Authors: Khoshnoud Farbod , de Silva Clarence W. , Owhadi Houman
Published: May 2012

Design and analysis of an embedded nano-electromechanical capacitive sensor for vibration monitoring is presented in this paper. In this sensor, vibration sensing is carried out by detecting the oscillations of a Single Walled Carbon Nanotube (SWCNT). The SWCNT is excited when it is subjected to a base motion corresponding to the measured vibration. Acquisition of the sensor signal is performed by a capacitance circuit, using the electric charge generated in the Carbon Nanotube (CNT). A modulation in the charge in the CNT, due to change in the capacitance, leads to a modulation in the CNT’s conductance and is used in measuring the input vibration. Vibration properties of the CNTs are obtained by molecular mechanics and finite element analysis where atoms are modeled as particles with an equilibrium distance equal to the bond length, and the bonded interactions of atoms are modeled as flexible beams. Stiffness coefficients of the atomic bonds are modeled using Morse atomic potential. A bridge circuit is utilized in this sensor to compensate for temperature and other environmental effects. When the CNT is in the vicinity of the gate underneath the tube, at a distance in the range of 1 nanometer to 1 micrometer, Casimir pressure, due to quantum fluctuations in the zero point electromagnetic field, can attract the CNT to the gate. This unwanted applied force on the tube may lead to inaccurate measurement of the vibration. In order to study the effect of Casimir pressure on the CNT a simplified model of the Casimir effect, for parallel surfaces, is adopted. This model can assist in achieving better accuracy in vibration measurement, and the sensor can be calibrated accordingly to account for the Casimir attractive force. The paper presents the physical and operational details of the sensor. This device is particularly useful for precise and effective sensing of vibration for machinery and structural condition monitoring and fault diagnosis.
Modal Analysis of Systems Using a Neuro-Fuzzy Approach
Authors: Khoshnoud Farbod , de Silva Clarence W.
Published: May 2012

A novel method of modal analysis for vibration modeling of systems is presented in this paper. In the developed method, first, mode shapes of the structure that is being analyzed are approximated. The approximate mode shapes are expressed by fuzzy sets where approximate deflections or displacement magnitudes of the mode shapes are described by fuzzy linguistic terms such as Zero, Medium, and Large. Fuzzy membership functions provide a means of dealing with the imprecisely defined system and it gives access to a large repertoire of tools available in the field of fuzzy reasoning. Second, fuzzy representations of the approximate mode shapes, called Fuzzy Mode Shapes in this paper, are updated using modal analysis data as obtained through experimentation. Finally, artificial neural networks are used as a tool to obtain an accurate version of the mode shape data by learning the target set of the data. An appropriate analogy of the application of Fuzzy Mode Shapes in the first step is the Starting Mode Shape Vectors in numerical eigenvector problem where the starting vector is updated through an iterative process. In this paper iterative updating process of mode shapes is carried out for the application of experimental modal testing. In this approach the differences between the fuzzy mode shapes and the corresponding measured modal testing data are minimized through an iterative process. In validating the developed technique for vibration modeling of one-dimensional and two-dimensional elastic bodies and structures, modeling of elastic beams, a clamped-free-clamped-free plate and a frame are used as illustrative examples. The solutions of the corresponding simulations are compared with the results from finite element computations and analytical model solutions. The good agreement of the results obtained for these models justifies the application of the developed method in experimental vibration modeling of systems. Use of the fuzzy-neural approach as developed in the paper expands the coverage of experimentally measured data, which is normally limited to a small number of measurement sets due to the limited number of available vibration sensors in the analyzed system. Neural networks provide a satisfactory interpolation of two sets of data including a) modal test data, which is accurate but is normally available only for a few measured points, and b) Fuzzy Mode Shapes, which are available for large number of points but are approximate.
Integrity Assessment of Multiple Dents in Oil and Gas Pipelines Using Probabilistic Design Analysis
Authors: Al-Muslim Husain Mohammed , Arif Abul Fazal M.
Published: May 2012

Mechanical damage in transportation pipelines is a threat to its structural integrity. Failure in oil and gas pipelines is catastrophic as it leads to personal fatalities, injuries, property damage, loss of production and environmental pollution. Therefore, this issue is of extreme importance to Pipeline Operators, Government and Regulatory Agencies, and local Communities. As mechanical damage can occur during the course of pipeline life due to many reasons, appropriate tools and procedures for assessment of severity are necessary. There are many parameters that affect the severity of the mechanical damage related to the pipe geometry and material properties, the defect geometry and boundary conditions, and the pipe state of strain and stress. Moreover, multiple damaged areas may exist and interact like in the case of a hit by a multiple-tooth excavator. The main objective of this paper is to determine the distance and orientation where interaction of multiple dents is significant. The strain and stress fields are evaluated for static pressure loading and the stress range and fatigue life are evaluated for cyclic pressure loading. Accordingly, guidelines are developed for the integrity assessment of multiple dents in oil and gas pipelines. The input parameters of the problem including the pipe material, pipe geometry, dent dimensions, and distance and orientation between two dents have a great variability. Therefore, probabilistic design approach is applied to determine the sensitivity and correlation between the output and input parameters. The base case deterministic FEA model has been validated with full-instrumented full-scale tests conducted by Pipeline Research Council International as part of their active program to fully characterize mechanical damage.
Construction and Application of Mechatronics Automation Laboratory at CDHAW of Tongji University
Authors: Yu Ying , Wang Yu
Published: May 2012

The Sino-German School of Applied Sciences (Chinesisch-Deutsche Hochschule fu¨r Angewandte Wissenschaften, CDHAW) is an educational project of the Chinese Ministry of Education and the German Federal Ministry of Education and Research, implemented by Tongji University and a consortium of German Universities of Applied Sciences. Students mainly study in classroom but lack experimental experience is a common problem in China university education. Main object of this Sino-Germany cooperation project is to train students with both of theoretical knowledge and also problem solving ability based on the experiment and practice in corresponding labs. Laboratory construction is therefore one of the most important parts in this Sino-Germany project. Mechatronics automation laboratory, which is designed to strengthen students’ comprehension of abstract concepts through experimental validation and enable students to benefit from experiment design and development of mechatronics projects, is the first one to be built together with the sponsorship of Siemens. Equipments inside can be combined flexible for different experiments, which can serve for many curricula. The automation laboratory is not only developed for curriculum but also for research work. It is open to all students, who are interesting to some research or take part in some creative games. This paper introduces the automation laboratory construction idea, equipment configuration, and coherent and comprehensive experiment development.
The Influence of Tread Hollowing of the Railway Wheels on the Hunting of a Coach
Authors: Tavakkoli H. , Ghajar R. , Alizadeh K. J.
Published: May 2012

A railway wheel has subjected to millions of intense wheel-rail contact cycles in its lifetime. Due to these severe contacts, wheel surface has worn gradually to a hollow shape. Also, tread hollowing rarely has occurred by plastic flow of surface material. Tread hollowing major consequences are false flange and different rolling radius of the wheels on a wheelset. False flange queers vehicle steerage and rolling radius differences can advance vehicle instability. This paper investigates the effect of tread hollowing, in the form of false flange and rolling radius difference, on the dynamic behavior of a railway coach. Modeling and analysis of the coach equipped by hollow wheels is performed using Adams Rail software. This study is conducted following on the problem appeared after operation of the newly purchased passenger coaches by the Iranian railways. So, the main topic which is focused on is the lateral displacement of the coach. Finally, results are reported and compared to achieve a proper criterion for tread hollowing.
Methodology for the Development of Sustainable Reference Ontology in the Mechanical Engineering Domain
Authors: Goncalves Ricardo Jardim , Sarraipa Joa˜o , Mendonc¸a da Silva Joa˜o
Published: May 2012

Design and manufacturing teams face the challenge of integration and reuse of computational information systems and knowledge. The management of information systems dealing with heterogeneous data and semantics meets the problem of interoperability between software applications, and it has been the basis to research on methodologies for the sustainability of reference ontologies. Ontologies facilitate the computational understanding, communication and seamless interoperability between people and organizations. They allow key concepts and terms relevant to a given domain to be identified and defined in an open and unambiguous way. Therefore, ontologies facilitate the use and exchange of data, information, and knowledge towards intelligent systems interoperability. Tasks on distributed and heterogeneous systems demand support from more than one ontology. Multiple ontologies need to be accessed by the same, but also different systems. The distributed nature of ontology development has led to dissimilar ontologies for the same or overlapping domains. Thus, various parties with different ontologies often do not understand each other. To solve these problems, it is suggested the use of ontology mapping geared for interoperability. This paper proposes a methodology to support the development of a sustainable common reference ontology for a group of endeavors sharing a mechanical engineering domain. This methodology enables each organization to keep its own terminology, glossary and ontological structures, providing seamless communication and interaction with the others, assessed by interoperability checking processes for an overall interoperable level of interacting systems. A use case in the mechanical engineering domain is described and the proposed methodology demonstrated.
Finite Element Analysis on Stress Concentration of Well Casing With Corrosion Pits
Authors: Zhang Jing , Fan Jianchun , Zhang Laibin , Wen Dong , Wang Yumei
Published: May 2012

Corrosion-induced pits will disturb the original stress distribution of casing and appear local high stress area. Through 3-D finite element analysis on casing with spherical and cylindrical corrosion cavity, the stress concentration degree and the influences of cavity shape, size and orifice diameter on stress concentration factor are determined and analyzed. The results show that the depth and shape of corrosion cavities are major factors impacting the stress concentration factor. For the casing with corrosion pits, the smaller orifice diameter, the more obvious influence of hemisphere effect on stress concentration factor. With the transition from shallow-spherical cavity to exact hemispherical cavity or from exact hemispherical cavity to deep-spherical cavity or from exact hemispherical cavity to cylindrical cavity, the changes of stress concentration factor show different characteristics.
Modeling of Cohesive Zone and Crack Growth in Ni-Al Thin-Film Using MD-XFEM Based Approach
Authors: Singh Gaurav , Sutrakar Vijay Kumar , Roy Mahapatra D.
Published: May 2012

Intermetallic alloys of Ni-Al have important applications in high temperature anti-corrosive coatings, engine and turbine related materials, and shape memory devices. Predicting failure behavior of these materials is difficult using purely continuum model, since several of the material constants are complicated functions of micro and nano-scale details. This includes solid-solid phase transformation. In the present paper, a framework for analyzing fracture in two-dimensional planar domain is developed using a molecular dynamic (MD) simulation and extended finite element method (XFEM). The framework is then applied to simulate fracture in Ni-Al thin-film. Effect of Ni Al crystallites of various sizes on the mechanical properties is analyzed using direct MD simulations. Initiation and growth of crack under slow (quasi-static) tensile loading in mode-I condition is considered. Mechanical properties at room temperature are estimated via MD simulations, which are further used in the XFEM at the continuum scale. A cohesive zone model for the macroscopic XFEM model is implemented, which directly bridges the molecular length-scale via MD framework. Numerical convergence studies are reported for mode-I crack in initially single crystal B2 Ni-Al thin film.
Heat Transfer and Thermal Stress in a Lithium-Ion Battery
Authors: Wu Wei , Xiao Xinran , Shi Danghe
Published: May 2012

This paper presents a finite element based multi-scale model for a lithium-ion (Li-ion) battery cell. The model considers multi-physics including battery kinetics, diffusion, thermal and stress analysis. In battery thermal analysis, the heat source is critical. In this model, both resistive and entropic heating were considered. Simulations were carried out for a LiC6/LiPF6/LiyMn2O4 cell under a discharge-charge cycle. The heat generations due to these two heat sources were compared. The thermal stress was computed and compared with the intercalation stress for individual battery components. Within the electrode particles, the thermal induced stress was negligible. In the separator, however, the thermal induced stress was comparable or even higher than the stress caused by intercalation deformation of the electrode particles.
Technoeconomic Study of Wind Energy Potential and Prospects in Oman
Authors: Malik Arif S. , Al-Jabri Haitham N. , Al-Farsi Fahad N. , Al-Ma’mary Thani S. , Al-Khadhuri Mohammed K.
Published: May 2012

This paper reports the study that carried out to find the wind energy potential and prospects in Oman. The results presented here are for three different sites. The first site discussed is for remote non-grid application of wind energy, the second for grid application and the third for wind pump application. The economic comparison for non-grid power applications is made between diesel engine generating sets alone and wind-diesel hybrid system at the selected location. The economic cost of grid system extension is also estimated for comparison purposes. The results show that for non-grid application for the selected site the levelized cost of wind-diesel system is 0.105 $/kWh comparing to 0.148 $/kWh for diesel system alone. For grid power application the study found that installing a 20 MW wind farm in Quiroon Hariti has a levelized cost of energy comparable to long-run marginal cost of open cycle gas turbines. For wind pump application the study found that the total annualized cost of installing wind pumps for irrigating a selected farm in Thumrait without and with one day water storage is $1,368 and $2,067 respectively. The total annualized cost of using a diesel pump for irrigating the same farm is $3,523.
A Numerical Study of Unsteady Natural Convection in a Rectangular Enclosure: Transition From Laminar to Turbulent Flow
Authors: Akyuzlu K. M. , Chidurala M.
Published: May 2012

A two-dimensional, mathematical model is adopted to investigate the development of buoyancy driven circulation patterns and temperature stratification inside a rectangular enclosure. One of the vertical walls of the enclosure is kept at a higher temperature then the opposing vertical wall. The top and the bottom of the enclosure are assumed insulated. The physics based mathematical model for this problem consists of conservation of mass, momentum (two-dimensional, unsteady Navier-Stokes equations for turbulent compressible flows), and energy equations for the enclosed fluid subjected to appropriate boundary conditions. A standard two equation turbulence model is used to model the turbulent flow in the enclosure. The compressibility of the working fluid is represented by an ideal gas relation. The conservation equations are discretized using an implicit finite difference technique which employs second order accurate central differencing for spatial derivatives and second order (based on Taylor expansion) finite differencing for time derivatives. The linearized finite difference equations are solved using a Coupled Modified Strongly Implicit Procedure (CMSIP) for the unknowns of the problem. Numerical experiments were then carried out to simulate the development of the buoyancy driven circulation patterns inside rectangular enclosures (with aspects ratios 0.5, 1 and 1.5) filled with a compressible fluid (Pr = 0.72). Experiments were repeated for various wall temperature differences which corresponded to Rayleigh numbers between 104 and 106. Changes in unsteady circulation patterns, temperature contours, and vertical and horizontal velocity profiles were predicted while the flow inside the enclosure transferred from laminar to turbulent flow due to the sudden temperature change imposed on the vertical walls of the enclosure. Only the results of the enclosure with aspect ratio one is presented in this paper. These results indicate that this transition is characterized by unicellular circulation patterns breaking up in to multicellular formations and increase in the values of the predicted wall heat fluxes and Nusselt number as flow becomes turbulent.
A SOI-MEMS-Based Single Axis Active Probe for Cellular Force Sensing and Cell Manipulation
Authors: Zhang Li , Dong Jingyan
Published: May 2012

This paper presents the design, analysis, fabrication, and characterization of an electrostatically driven single axis active probing device for cellular force sensing and cell manipulation applications. The active probe is actuated by linear comb driver to create the motion in the probing direction. Both actuation and sensing comb drives are designed for the probing stage. The sensing comb structures enable us to sense the probe displacement when it is actuated, which enables application of force balanced sensing. The designed active probing device has an overall size of 5 mm × 4.5 mm, is fabricated on a silicon-on-insulator (SOI) substrate through surface micromachining technologies and deep reactive-ion etching (DRIE) process. The probe stage structure is fabricated on the 10-μm-thick device layer of SOI wafer. The handle layer beneath probe stage is etched away by DRIE process to decrease the film damping between the stage and the handle wafer thus achieving high quality factor. The proposed single axis probe is aimed at sensing cellular force which ranges from pN to μN and cell manipulation applications.
Engineering Design of High Strength Brazed Joints for Heat Exchangers
Authors: Norman Charles R.
Published: May 2012

The design of high strength brazed joints in heat exchangers is critical to the manufacturer and user for efficient manufacturing and satisfactory performance. Material selection, geometric considerations, heat treating recipe, engineering analysis and material testing play critical roles in designing a brazed joint to meet good engineering design requirements. The engineering design is an international problem and all manufacturers require similar methodology including testing before and after brazing. This paper addresses an engineering approach to designs that can be tested, analyzed, documented and monitored during operation. Examples of choosing materials, designing geometry, determining heat treating, engineering analysis and material testing are given. The final product design must satisfy good engineering methodology and perform satisfactorily over the expected life.
Using Online Resources for an Advanced Vehicle Technology Engineering Competition
Authors: Lambiase Nicole E. , Nelson Douglas J. , Falcone Frank J. , Wahlstrom Michael A. , De La Rosa Kristen G.
Published: May 2012

Advanced Vehicle Technology Competitions have adopted an online collaboration system to coordinate information sharing and dissemination among hundreds of people from numerous organizations and across multiple countries, including universities, competition organizers, and sponsors involved in the competitions. Microsoft SharePoint is a collection of software elements that includes web browser based collaboration functions, process management modules, search modules and a document-management platform that serves as the foundation for this online collaboration system. SharePoint is used to host a secure web site that accesses shared workspaces, information stores and documents, as well as threaded discussion forums. Users can manipulate controls called “web parts” or interact with pieces of content such as lists and document libraries. The overall team-based engineering education strategy is facilitated throughout the three year EcoCAR program by a two way flow of information between the teams and organizers. Safety and design rules are updated and posted for teams to access. Each team has their own secure document library area for posting required progress reports, design reports, safety documentation, and technical report deliverables that are scored as part of the competition. Scoring results with comments are returned to each team under the team specific site. Proprietary vehicle and component data are also made available, and can be restricted to only those teams that have approved non disclosure agreements with the sponsor. Specific subject and component-based forums are used for asynchronous, threaded exchange of information and questions to subject matter experts. Issues and solutions discovered by students are shared among all teams. The SharePoint Online Collaboration system has significantly improved the information-sharing, evaluation and communications capabilities of the Advanced Vehicle Technology Competitions across a vast audience. This has enabled us to significantly enhance the technical scope of the program and improve the educational value to the university participants.
Computational Development of a Gas to Liquid Heat Exchanger With a Breathing Operation
Authors: Jorgenson Richard N. , Van de Ven James D.
Published: May 2012

Thermal conditioning of a gas during compression and expansion processes requires rapid transfer of heat. Proposed is a thin flexible membrane with a biologically-inspired, lung-like structure characterized by branching tubes, massive surface area, and low overall pressure drops. By forcing the working gas into contact with the large surface area of a thin membrane, rapid heat transfer may be achieved across the membrane and into a liquid bath. Inspiration and expiration of the gas is driven by volume changes in the liquid bath. A computational approach is taken to the design of the lung-like structure. First, Non-dominated Sorting Genetic Algorithm II (NSGA-II) is run to optimize elemental geometries for minimum pressure drop and maximum heat transfer. In the initial case, 2D elements are passed through Gambit and Fluent to evaluate the fitness function. Here, we present the results of the elemental optimization. In the future, 3D elements will be analyzed and connected in an optimal way to generate a 3D lung-like structure.
Root Cause Analysis of an Industrial Boiler Explosion (and How Hazard Analysis Could Have Prevented It)
Authors: Ramirez Juan C. , Fecke Mark , Morrison Delmar Trey , Martens John D.
Published: May 2012

An explosion occurred in the firebox of an industrial boiler with a nominal fuel input rate of 100 MW (340 million Btu/hr), in a processing plant during final commissioning of the burner systems. This paper describes the investigation of the incident, root cause analysis, and lessons learned from the incident. The original burners in the boiler had recently been replaced with low NOx burners, and the facility was in the process of commissioning the new burner system. The boiler was running only on natural gas igniters at the time of the incident. While firing on igniters, an undetected stoppage of the control equipment occurred, which led to a restriction of airflow through the secondary air dampers. The boiler controls included programmable logic controllers (PLCs) for both the combustion control system (CCS) for regulation and the burner management system (BMS) for safety functions. The BMS was intended to detect a loss of control such as this and immediately stop fuel to the boiler; however, it did not. The BMS PLC was not configured to detect the dangerous states and allowed the igniters to continue to fire. An explosion subsequently occurred within the boiler firebox that caused extensive damages to the facility and equipment. This paper will describe the incident investigation and determination of multiple root causes for failure of the BMS to prevent the explosion. The inadequate configuration of the control systems was likely present for some time prior to the incident, and the explosion was eventually caused when the right conditions occurred during this commissioning. We found through the investigation that the BMS deficiencies could have been detected and prevented (and almost were) through standard hazard analysis techniques common in the chemical processing industries. This paper will also discuss how hazard analysis can be applied to detect and prevent similar system failures.
Development of Scaling Model for a MEMS-Based Micro Heat Engine
Authors: Bardaweel H. , Preetham B. S. , Richards R. , Richards C. , Anderson M.
Published: May 2012

In this work we investigate issues related to scaling of a MEMS-based resonant heat engine. The engine is an external combustion engine made of a cavity encapsulated between two thin membranes. The cavity is filled with saturated liquid-vapor mixture working fluid. We use both model and experiment to investigate scaling of the MEMS-based resonant heat engine. The results suggest that the performance of the engine is determined by three major factors: geometry of the engine, speed of operation, and thermal physical properties of engine components. Larger engine volumes, working fluids with higher latent heat of evaporation, slower engine speeds, and compliant expander structures are shown to be desirable.
Germanium Nanowire Synthesis via Localized Heating and a Comparison to Bulk Processes
Authors: Redcay Christopher J. , Englander Ongi
Published: May 2012

In this work, we compare the localized synthesis of germanium nanowires (GeNWs) to germanium nanowires synthesized under a globally high temperature environment. The localized synthesis of germanium nanowires is presented for the first time using the resistive heating of MEMS microbridges. The results of the localized synthesis process are then compared with the results of well-established high temperature synthesis processes for germanium nanowires. The effect of heat source and local temperature gradients on the resulting nanowires is assessed. The results suggest that optimal nanowire synthesis conditions in a high temperature furnace environment are no longer optimal in localized heating based synthesis. More specifically, there is a significant reduction in growth rates with the localized process. Differences in nanowire quality are observed as kinking and bending of the nanowires are a common result of the localized process yet rare in germanium nanowires synthesized in a global heating environment. Nanowires grown in a global heating environment exhibit larger average wire diameters, approximately 80 nm larger, compared to those synthesized using the localized heating process. Finally, nanowire tapering which is evident in the global heating process is not prevalent in the localized process.
Study of Pre-Stress Effect of Ribcage Structure on Chest Response of Crash Dummy Model
Authors: Lai Xinghua , Zhou Qing
Published: May 2012

Assembling induced pre-stress state commonly exists in the ribcage structure of Hybrid III dummy hardware. In the practice of dummy modeling, however, the pre-stress issue is often neglected. This study is intended to assess the pre-stress effect on chest response of the Hybrid III 50th percentile male dummy model. In this paper, how the pre-stress state is generated in the dummy ribcage assembling process is first elaborated by disassembling and reverse engineering a physical dummy chest structure. A thorax FE model is then built and validated against test results. Using finite element modeling approach, the structural responses with and without the pre-stress state are compared and analyzed at single rib, ribcage and full dummy levels and under a number of loading conditions. The study has found out that, there are two common pre-stress states existing in the rib components of the dummy ribcage, pre-compressive stress and pre-tensile stress. Compared with no pre-stress model, the pre-compressive stress makes a rib stiffer and the pre-tensile stress makes a rib less stiff. It is further concluded that, the pre-stress effect is significant at the single rib level and insignificant at the ribcage level and the full dummy level. This is mainly because the effects of the pre-compressive stress and the pre-tensile stress existing in the six ribs are compensated each other in the assembled ribcage. Therefore, neglecting the pre-stress effect of the ribcage structure in the dummy models is reasonable.
Safety Assessment of Inner Hull Structure Affected by Cryogenic Temperature
Authors: Han Sangmin , Bae Junhong , Lee Kyungwon , Ha Munkeun , Joh Kihun , Suh Yongsuk , Rhee Shinhyung
Published: May 2012

The market of LNG (Liquefied Natural Gas) carrier is continuously in a prosperous condition, and a lot of LNG vessels are being built in many shipyards. Membrane-type MARK-III LNG CCS (Cargo Containment System) is used more and more in the construction of LNG carrier, and it has already taken considerable market share among the various LNG CCS products. This paper deals with a study on structural safety of LNG carrier whose inner hull structure is affected by cryogenic temperature of LNG. If the primary and secondary barriers are failed simultaneously, the inner hull structure comes to be in direct contact with LNG. It is well known that the cryogenic temperature exposes the inner hull structure to fatal risk of structural failure due to brittle fracture, but nevertheless it is quite difficult to find a precedent research which explains the degree of risk and severity with due consideration of the consequence caused by structural failure of inner hull. The heat transfer test has been performed using the specimen appropriate to realize test scenario while considering cryogenic liquid flow from primary and secondary barrier into inner hull structure, and at the same time, the specimen has been tested by applying proper deformation so as to examine the structural behavior of inner hull structure under cryogenic condition. The heat transfer analysis has been performed to simulate and verify the heat transfer test, and consequently it is possible to obtain actual distribution of temperature in the inner hull structure exposed to cryogenic temperature. The structural analysis has been performed to evaluate the damage of inner hull structure and as a result to assess overall decrease of hull girder strength of LNG carrier. Finally, consequence of the decrease of global strength has been discussed.
The Influence of Ratchets Dimension and Shape on the Motion of Leidenfrost Droplet
Authors: Ok Jeong Tae , Farshchian Bahador , Park Daniel Sang-Won , Park Sunggook
Published: May 2012

The influence of ratchet aspect ratio and the shape of ratchet ridges on the motion of film boiling water droplet were investigated. Continuous rebounding behavior of the droplet was observed on micro ratchets with lower depths and round ridges. The residence time and flying time of rebounding droplets are independent of surface temperature. The terminal velocity increases but the number of rebounds decreases as the surface temperature increases in the range of 192–248°C.
Sensitivity of MEMS/NEMS Biosensors Near Twice Natural Frequency
Authors: Caruntu Dumitru I. , Knecht Martin W.
Published: May 2012

Bio-MEMS/NEMS resonator sensors near twice natural frequency for mass detection are investigated. Electrostatic force along with fringe correction and Casimir effect are included in the model. They introduce parametric nonlinear terms in the system. The partial-differential equation of motion of the system is solved by using the method of multiple scales. A direct approach of the problem is then used. Two approximation problems resulting from the direct approach are solved. Phase-amplitude relationship is obtained. Numerical results for uniform electrostatically actuated micro resonator sensors are reported.
Employing Neural Networks for Manipulability Optimization of the Dual-Arm Cam-Lock Robot
Authors: Jouibary B. R. , Osgouie K. G. , Meghdari A.
Published: May 2012

Cooperative systems have been extensively investigated in literature. Herein the criteria and implementation for employing neural networks artificial intelligence for finding the optimal configuration of the Dual-Arm Cam-Lock (DACL) robot manipulators at a specific point with the objective to optimize the applicable task-space force in a desired direction are addressed. The DACL robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators which operate redundantly but they may lock into each other in specific joints to increase structural stiffness in the cost of losing some degrees of freedom. Obtaining the optimal configuration demands lots of computational time and is not practical in real-time applications. The neural network is trained to approximate the optimum configuration considering the geometrical constraints of the planar arms using genetic algorithm as a multi-objective optimizer.