bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of PIV Seed Particles for Flow in Porous Media
Authors: Patil Vishal A. , Liburdy James A.
Published: May 2012

The ability to perform particle image velocimetry (PIV) in porous media presents many challenges in order to minimize the inherent errors in the process. Index of refraction matching is one method to visualize the entire region of interest. One important question is the available signal to noise ratio when using an index of refraction technique that may have small differences of index between the liquid and solid phases. Scattering that will occur at the phase interfaces are enhanced as the index mismatch increases. Consequently the highest intensity seed scattering is desired along with reduction of unwanted interface scattering. This paper examines four seed types: silver coated hollow glass spheres, polystyrene spheres, dyed polystyrene spheres, and fluorescent filled polystyrene spheres and the scattering power of each is measured in a porous media environment. It is found that the silver coated spheres coupled with the use of P polarized light provides the best scattering intensity coupled with low noise background. Also seed size required, based on Stokes number criterion, to follow inertial flows in porous media is presented.
Study of Strong Pressure Wave Propagation in a Two-Phase Bubbly Mixture
Authors: Raju Reni , Singh Sowmitra , Hsiao Chao-Tsung , Chahine Georges
Published: May 2012

A geometrically simple configuration of a gas bubble expanding in a bubbly medium is chosen to study multi-scale modeling approaches in simulating multiphase flows. Three solvers following the Eulerian-Lagrangian, multi-component compressible and analytical approaches have been studied for different bubbly medium void fractions. In the Eulerian-Lagrangian approach, an incompressible solver was coupled with a bubble dynamics model, while for the Eulerian two-fluid approach and the analytical model the surrounding fluid was assumed to be a homogeneous mixture. It was found that both two-fluid and analytical models match very well for the cases tested. The Eulerian-Lagrangian model shows that the dynamics of the bubbly medium and the expanding bubble are inherently coupled in a non-linear fashion. Presence of discrete bubbles also introduces localized perturbations in the void fraction as well as in the pressure distribution which cannot be captured by the homogeneous mixture models.
Temperature-Stable Differential Micro-Resonators for Timing Application
Authors: Hajhashemi M. Sadegh , Amini Alborz , Bahreyni Behraad
Published: May 2012

In this paper, we present a simple method for the design of temperature-stable oscillators using silicon resonators. This technique is based on generation of two different frequencies f1 and f2 with the same temperature dependence. It is now possible to obtain a third signal from mixing of the two reference frequencies which, through proper selection of resonator parameters, does not change with temperature. The design process is quite simple as it relies on the inherent differences in material properties of crystalline silicon.
Manfacturing and Evaluation of Polyurethane Synthetic Long Bone Models
Authors: Celemin Alejandro , Polanco Ana M.
Published: May 2012

This paper reports the process of production and assessment of rigid polyurethane foam for synthetic bone surrogates. Synthetic bones are currently being used for orthopaedic surgical training and lower limb trauma evaluation. Previous studies have shown that synthetic bones made of rigid polyurethane are able to simulate bone’s mechanical response. In this study, two polyurethane formulations were tested under compression and impact conditions. Results of these tests were compared with data reported in current literature sources for cancellous bone tissue. Comparison between results and reported data, showed that none of the polyurethane foams produced had significant resemblance to cancellous bone properties. Improvements in terms of formulation and manufacturing procedures of polyurethane shall be made in order to acquire a higher mechanical performance.
Numerical Study on Mixed Convection in Porous Media in a Channel With an Open Cavity Below
Authors: Buonomo Bernardo , Manca Oronzio , Mesolella Paolo , Nardini Sergio
Published: May 2012

A numerical analysis of mixed convection in gas saturated metal foam in a horizontal channel with an open cavity heated at uniform heat flux on a vertical wall is studied numerically. Non-local thermal equilibrium and Brinkman-Forchheimer-extended Darcy model are assumed. Boussinesq approximation with constant thermophysical proprieties are considered. Results are carried out for an aluminium foam with 10 PPI and ε = 0.909, the fluid is air and for the assisting case. Results, for different Peclet and Rayleigh numbers, are given in terms of solid and fluid wall temperatures and local Nusselt numbers and stream function and temperature fields. Results show that diffusive effect determined lower temperature values inside the solid and the fluid temperatures are higher in all considered cases. The interaction between the forced flow in the channel and the buoyancy due to the heated wall determines different thermal and fluid dynamic behaviors.
On the Design of a Multi-Megawatt Oil-Free Centrifugal Compressor for Hydrogen Gas Transportation and Delivery: Operation Beyond Supercritical Speeds
Authors: Heshmat Hooshang , Hunsberger Andrew , Ren Zhaohui , Jahanmir Said , Walton James
Published: May 2012

Deployment of a safe, efficient hydrogen production and delivery infrastructure on a scale that can compete economically with current fuels is needed in order to realize the hydrogen economy. While hydrogen compression technology is crucial to pipeline delivery, positive displacement (PD) compressors are costly, have poor reliability and use oil, which contaminates the hydrogen. To overcome poor reliability of the PD compressor, duplicate units are installed but at substantial costs. A totally oil-free, high-speed, efficient centrifugal compressor using 4th generation compliant foil bearings and seals has been designed for hydrogen pipeline delivery. Using 6-12 megawatt drives operating at speeds to 56,000 rpm, a modular, double entry compressor was configured to deliver 500,000 kg/day at pressures greater than 8 MPa. Each of the two or three multi-stage compressor frames operate above its bending critical speed since speeds are 5 to 7 times faster than conventional compressors. To assure a structurally and economically feasible design, the rotor of each compressor spins at the same speed with blade tip velocities below 600 m/s. An iterative aerodynamic/structural/rotordynamic design process was used, including both quasi-three dimensional inviscid internal flow and Computational Fluid Dynamic (CFD) analyses. The flow field was carefully analyzed for areas of excessive diffusion, sudden velocity gradients and flow separation. Excellent correlation between the preliminary design and CFD analyses was obtained. Structural and rotor-bearing system dynamic analyses were also completed to finalize the compressor system configuration. Finite element analysis of the compressor impeller was used to verify structural integrity and fatigue limits for selected materials. Rotor-bearing system analysis was used to define acceptable bearing locations and dynamic coefficients, system critical speeds and dynamic stability. Given the high speeds, supercritical operation, and required reliability, efficiency and freedom from contaminants, compliant foil gas bearings were selected and designed. Since hydrogen will be used as the bearing lubricant for the foil bearings, substantially lower power loss than oil lubricated bearings will be experienced and the auxiliary supply or scavenge system is eliminated.
A Truly Generalized Plane Strain Meshless Model for Combined Normal and Shear Loading of Fiber Reinforced Materials
Authors: Ahmadi Eisa , Aghdam M. M.
Published: May 2012

A truly meshless method based on the integral form of equilibrium equations is formulated. A micromechanical model is developed to study micro-stresses in normal and shear loading of unidirectional fiber reinforced composites. A small repeating area of composite including a fiber surrounded by matrix called representative volume element (RVE) is considered as solution domain. A direct method is proposed for enforcement of the appropriate periodic boundary conditions for shear and normal loading. Especially transverse shear loading is considered in this analysis. Fully bonded interface condition is investigated and the continuity of displacements and traction is imposed to the fiber-matrix interface. Comparison of the predicted results shows excellent agreement with results in available literature. Results of this study also revealed that the presented model can provide highly accurate predictions with respectively small number of nodes and small computation time without the complexity of mesh generation.
Ovariectomy and its Antioxidative Effect on Bone
Authors: Rai Durg V. , Ranu Harcharan Singh
Published: May 2012

Ovarian hormone deficiency increases the generation of reactive oxygen species. Oxidative stress due to reactive oxygen species (ROS) can cause oxidative damage to cells. Cells have a number of defense mechanisms to protect themselves from the toxicity of ROS. There is increasing evidence of the role of free radicals in bone resorption and bone loss. Ovariectomised female wistar rats had been used as the animal model for the study of osteoporosis. Even though, there are studies portraying the role of free radicals in bone loss, the defense mechanism adapted by bone in ovariectomised animals remains obscure. So, the impact of ovariectomy on the bone antioxidant system in rats was investigated. Twenty female wistar rats were taken and divided into two groups: ovariectomised and control. It had been found that a significant (p<0.001) decrease in the activity of various enzymes like CAT (catalase), SOD (superoxide dismutase) (p<0.001), GST (glutathione-s-transferase). However, an increase in the malondialdehyde levels was found to be 30% in the ovariectomised rats as compared to the controls. Thus the study elucidates the oxidative stress in bone under ovariectomy.
Biomimetric Liquid State Inertial Sensor
Authors: Zeng Hansong , Zhao Yi
Published: May 2012

Vestibular system is a motion sensing organ vital to human balance system. Patients suffering from vestibular disorders usually experience symptoms including blurred vision, vertigo and increased risks to fall. It is reported that more than 1 billion dollars are spent each year on treating such diseases. In order to accomplish balance prosthesis, an engineering motion sensing system that possesses a comparable function as the natural vestibular system is needed. One unique characteristic of human body motion is the low frequency, which is different from the resonance frequency range of conventional solid state accelerometers and gyroscopes. This makes it difficult for solid state sensors to achieve large response by the body motion. In this work, we developed a liquid state motion sensing system, whose resonant frequency is within the range of that of body motion. The sensor consists of a curved microchannel, a liquid droplet that can move freely on the channel, and microelectrodes that detect the relative movement of the droplet along the channel. The simple fabrication approach and surface treatment techniques are described in the paper. Droplet dynamics revealing the unique frequency response is theoretically investigated followed by experimental validation. Binary electrical signals are used to determine the acceleration, which minimizes the influence of external electromagnetic noises. Characterization of a single sensor for 1D measurement and an assembled sensor set for 2D measurement demonstrates that low-frequency motion can be precisely determined by the liquid state sensing system. The study of liquid state inertial sensor paves a new route of body motion detection. Considering its concise configuration, simple fabrication, miniaturized size and low cost, the sensor provides a promising candidate for balance prosthesis. It also enables the in-depth investigation of motion detection methodology.
Large Deflection of a Laminated Composite Plate With Different Extensional and Flexural Material Properties
Authors: Arıko¨k Rifat , Mecitog˘lu Zahit
Published: May 2012

This paper presents the large deflection elastic analysis of the hand lay-up composite plates with different extensional and flexural modulus including geometric nonlinearity effects that are taken into account with the von Ka´rma´n large deflection theory of thin plates. Governing equations of the motion are derived by means of the virtual work principle. Then the Galerkin method is applied to reduce the nonlinear coupled differential equations into a nonlinear algebraic equation system. The MATLAB and MATHEMATICA software are used to solve the equation system. Because of the common nonuniformities in hand lay-up fabric laminates such as resin surface layers and unequal layer thickness, the flexural and extensional modulus of such laminated composites are different. By the way, since the bending and in-plane effects are together affect to the nonlinear behavior of a composite laminate, it should give more reliable results when using different flexural and extensional modulus in the analysis. In this study, the results of approximate analysis, ANSYS finite element analysis and experimental study are obtained and compared for a fully-clamped laminated composite plate subjected to a uniform pressure load. The material properties used in the analysis are determined tension and three-point bending tests.
Nondeterministic Multiscale Modelling of Biomimetic Crack Self-Healing in Nanocrystalline Materials
Authors: Karpov Eduard G. , Grankin Mykhailo V.
Published: May 2012

A nondeterministic multiple scale approach based on numerical solution of the Monte-Carlo master equation coupled with a standard finite-element formulation of material mechanics is presented. The approach is illustrated in application to the processes of long-term self-diffusion, precipitation and crack/void healing in nanocrystalline bcc and fcc solids. Effect of static and dynamic loading patterns on the crack healing rates are investigated. The approach is widely applicable to the modeling and characterization of advanced functional materials with evolutionary internal structure.
Vibration of Fiber Reinforced Anisotropic Composite Plates With Nanofiber Reinforced Matrices
Authors: Chamis Christos C. , Murthy Pappu L. N.
Published: May 2012

Anisotropic composite plates were evaluated with nanofiber reinforced matrices (NFRM). The nanofiber reinforcement volumes ratio in the matrix was 0.01. The plate dimensions were 20 by 10 by 1.0 in. (508 by 254 by 25.4 mm). Seven different loading condition cases were evaluated: three for uniaxial loading, three for pairs of combined loading, and one with three combined loadings. The anisotropy arose from the unidirectional plates having been at 30° from the structural axis. The anisotropy had a full 6 by 6 rigidities matrix which were satisfied and solved by a Galerkin buckling algorithm. The buckling results showed that the NFRM plates buckled at about twice those with conventional matrix.
Adaptive Control of a Macro/Micro Bilateral Teleoperation System Under Variable Time Delay
Authors: Esfahani A. Monemian , Rezaei S. M. , Zareinejad M. , Saadat Mozafar
Published: May 2012

In this paper a new stable adaptive control for a Macro-Micro bilateral teleoperation system is proposed. Our platform to implement the controllers consists of a servo DC motor (macro) as the master robot and a piezo-actuator (micro) as the slave robot. Piezo-actuator has some characteristics which disturb the transparency and stability of the teleoperation system. We add a nonlinear disturbance observer to the slave robot controller in order to observe and compensate the disturbances. It is recognized that the presence of time delay is one of the largest barriers in teleoperation systems. This problem is mainly due to the distance separating the master from the slave and also is due to lag effect of filters and motor drivers. Because the time delay is unknown and variable, it can make the system unstable. In this paper, all of the above controllers are discussed using variable time delay. The stability of the system under variable time delay is guaranteed by Lyapunov stability criterion and passivity based methods. Tracking of force/position is achieved by selecting the best design parameters. Performance of the proposed control is validated by experimental results.
Crimp-Imbalanced Protective (Crimp) Fabrics
Authors: Cavallaro Paul V. , Sadegh Ali M.
Published: May 2012

This report documents research that was conducted to explore the unique concept of using crimp imbalance, which is a simple architectural modification achieved during the weaving process, as a potential mechanism to enhance fragmentation and ballistic protection levels of single-ply woven fabrics. It is shown in this report that crimp imbalance (1) can substantially influence the energy-absorption levels of single-ply fabrics for select fragment simulating projectile (FSP) velocities and friction coefficients; (2) can be tailored to controllably delay stress-wave propagations among yarn directions; and (3) can minimize reflections at the yarn crossover regions. This research, which used numerical models of single ply, plain-woven fabric, demonstrated that deviations in crimp contents can have significant effects on energy absorptions and projectile residual velocities; in short, optimal levels of crimp imbalance may exist for a specific ballistic threat type.
Programmable Micropatterning of Polymer Nanofibers
Authors: Kim Bongsu , Zhao Yi
Published: May 2012

This paper reports programmable micropatterning of electrospun nanofibrous materials using a collector chip that consists of an array of independently controllable microelectrodes. The microelectrodes on the collecting chip are prepared by standard photolithography. By programming the local electrical field using excited and floating electrodes, the collector chip allows patterning of microstructures with controllable characteristics. The difference of electrostatic force between the excited and the floating electrodes increases the patterning contrast of electrospun nanofibers. The arbitrary geometries are successfully patterned on the array of 6 × 6 electrodes by independently programmable control of the voltage of each electrode. The experimental result also shows that it is possible to control the porosity and alignment of fibers. This method provides a simple yet highly reliable approach for creating combined micro/nanostructures of polymer nanofibers in a cost effective manner, which has great potential in functional tissue engineering, filtration, and chemical sensing. The work is also expected to foster the use of nanofibers in microdevices for on-chip biochemical analysis, and controlled infiltration and proliferation. The resulting nanofibers with controllable porosity are especially useful for the construction of tissue engineering scaffolds with morphological and functional similarity with natural tissues.
Simulation of Dynamic Fracture Using Peridynamics, Finite Element Modeling, and Contact
Authors: Littlewood David J.
Published: May 2012

Peridynamics is a nonlocal extension of classical solid mechanics that allows for the modeling of bodies in which discontinuities occur spontaneously. Because the peridynamic expression for the balance of linear momentum does not contain spatial derivatives and is instead based on an integral equation, it is well suited for modeling phenomena involving spatial discontinuities such as crack formation and fracture. In this study, both peridynamics and classical finite element analysis are applied to simulate material response under dynamic blast loading conditions. A combined approach is utilized in which the portion of the simulation modeled with peridynamics interacts with the finite element portion of the model via a contact algorithm. The peridynamic portion of the analysis utilizes an elastic-plastic constitutive model with linear hardening. The peridynamic interface to the constitutive model is based on the calculation of an approximate deformation gradient, requiring the suppression of possible zero-energy modes. The classical finite element portion of the model utilizes a Johnson-Cook constitutive model. Simulation results are validated by direct comparison to expanding tube experiments. The coupled modeling approach successfully captures material response at the surface of the tube and the emerging fracture pattern.
Failure-Mode Clustering for Electronics Under Shock and Vibration Using Neural-Net Based Self-Organized Maps
Authors: Lall Pradeep , Gupta Prashant
Published: May 2012

In this paper prognostic framework for electronic systems has been developed with neural network based self organizing maps for clustering of failure modes. The presented approach resides in the pre-failure space with a focus on electronic systems with multiple failure modes. Portable electronic products subjected to transient shock may exhibit multiple failure modes in vicinity of the interconnects. Failure is often diagnosed by loss of functionality using techniques including the built-in self test, which provides limited insight into reliability and remaining useful life. Unsupervised learning of the neural net has been used to train the neural net for identification of individual failure modes. Feature vectors have been developed based on damage pre-cursors from time-spectral measurements. The clustered damage pre-cursors have been correlated with failure modes of the underlying damage. Several chip-scale packages have been studied, with leadfree second-level interconnects including SAC305, SAC405 alloys. Transient strain has been measured during the drop-event using digital image correlation and high-speed cameras operating at 100,000 fps. Continuity has been monitored simultaneously for failure identification. In addition, explicit finite element models have been developed and various kinds of failure modes have been simulated such as solder ball cracking, trace fracture, package falloff and solder ball failure. Fault modes predicted by simulation based pre-cursors have been correlated with those from experimental data. Activation of different neurons in the lattice for various failure modes and combinations of failure modes has been demonstrated. Previously the authors have developed techniques based on statistical pattern recognition for leading indication of impending failure and detection of damage initiation and progression [Lall 2006a, 2007a, 2008]. Early classification of multiple failure modes in the pre-failure space is new.
Analysis of Enterprise Rights Management Solutions for CAD Data According to the Requirements of the Automotive Industry and a Proposal to Increase the ERM Security Level
Authors: Rodrigues Henriques Joselito , Anderl Reiner , Grimm Marco
Published: May 2012

The use of computer aided design (CAD) for product development is well-established. Without this technology, it would be impossible to maintain the speed and quality of products in the collaborative product development process. When CAD technology was first introduced, it was only possible to include simple geometrical elements to represent the product in the CAD system. With the evolution of CAD systems much more information was added to the CAD files such as: model history, manufacturing information, material and others. With this information a lot of intellectual property is saved inside the CAD files. If, on one hand, the integration of the intellectual property to CAD data speeds up the product development, and makes it possible to integrate the different areas of the companies like development and manufacturing; on the other hand, this leads to general danger for the companies, because the CAD data must be shared inside and outside of the company. Nowadays, in most companies which are exchanging data, the security is just kept by contracts, laws and technical mechanisms that do not guarantee the security of the data being exchanged. As soon as the data crosses the border of the company there is no way to control the data anymore. One way to guarantee the security of the data exchanged is to ensure that only authorized people, no matter where they are located, can access distributed data. This is provided by Enterprise Rights Management (ERM), which protects the data as soon as it is created. ERM technology controls digital data, even after it has crossed the borders of the company. The owner of the data to be shared can control its rights by several approvals that can be granted or denied, e.g. who is allowed to work with the data, how long it can be accessed, which actions can be performed, and others. This paper analyzes two of the current ERM solutions for protecting CAD data according to the requirements of the automotive industry. It shows, that the analyzed ERM systems are protecting CAD data only on a file-based level and do not provide granular protection which is necessary to meet the automotive industry’s requirements. In order to furthermore increase security of CAD data, this paper also presents a proposal which extends the current file-based protection to a granular protection.
Investigation of a Multiple Impeller Design for a High Performance Air-Cooled Heat Sink
Authors: Staats Wayne L. , Peters Teresa B. , Allison Jon M. , McCarthy Matthew , Wang Evelyn N. , Brisson John G.
Published: May 2012

A high-performance air-cooled heat sink that incorporates a novel heat pipe with multiple parallel condenser layers and interdigitated blower impellers is presented. A flow circuit model was developed in order to predict the air flow performance of a 15-layer impeller system using experimental measurements from a single layer. A 15-layer impeller system was constructed to validate the flow circuit model. The performance of the multi-layer system was investigated by using a hot wire anemometer to compare flow between layers and by measuring the inflation rate of a bag enclosing the air outlets. This work addresses important issues that allow the extension of the air flow modeling and experimental results from a single impeller design to a multilayer stack of impellers operating in parallel and sharing a common inlet.
Role of the Kinetic Relation in a Phase Transition-Based Model for Mechanical Unfolding in Macromolecules
Authors: Raj Ritwik , Purohit Prashant K.
Published: May 2012

We present applications of a model developed to describe unfolding in macromolecules under an axial force. We show how different experimentally observed force-extension behaviors can be reproduced within a common theoretical framework. We propose that the unfolding occurs via the motion of a folded/unfolded interface along the length of the molecule. The molecules are modeled as one-dimensional continua capable of existing in two metastable states under an applied tension. The interface separates these two metastable states and represents a jump in stretch, which is related to applied force by the worm-like-chain relation. The mechanics of the interface are governed by the Abeyaratne-Knowles theory of phase transitions. The thermodynamic driving force controls the motion of the interface via an equation called the kinetic relation. By choosing an appropriate kinetic relation for the unfolding conditions and the macro-molecule under consideration, we have been able to generate a variety of unfolding processes in macromolecules.
Software Agent-Monitored Tutorials Enabling Collaborative Learning in Computer-Aided Design and Analysis
Authors: Beuth J. L. , Rose´ C. P. , Kumar R.
Published: May 2012

Internet chat-based tutorials are being developed for integrating computer modeling and design skills into mechanical engineering undergraduate and middle school outreach programs. These tutorials help students navigate complicated software interfaces while teaching fundamental concepts through dynamic dialogues between tutorial agents and student user groups. In a typical assignment, students are asked to perform a design or modeling task that includes the use of software such as a commercial finite element code or specially designed educational software. Students work in teams, but team members are distributed within a room or between remote sites, linked by a text interface. As students collaborate electronically, an intelligent agent monitors their interactions and interjects questions or comments in response to the use of key phrases, or due to other triggers. This platform is being used to help automate collaborative learning experiences and to study how students can effectively interact with each other and with the software agents. In undergraduate projects, fundamental technical skills and intuition in interpreting results are emphasized. In outreach efforts, participants are led to consider how their work relates to the broad mechanical engineering profession.
Analysis of Transient Heat Transfer in a Thermal Energy Storage Module
Authors: Kuravi S. , Trahan J. , Rahman M. M. , Goswami D. Y. , Stefanakos E. K.
Published: May 2012

The transient behavior of a thermal energy storage system was studied numerically. The storage system is composed of cylindrical tube containing the phase change material (PCM) surrounded by the heat transfer fluid (HTF) that flows along the axial direction of the tube. The melting of PCM was solved using specific heat capacity method. The heat transfer inside the tubes was analyzed by solving the energy equation, which was coupled with the heat conduction equation in the container wall. The velocity profile was obtained by solving the annular flow outside the tubes. The parameters that control the thermal behavior were identified. Several numerical simulations were performed to assess the effects of the Reynolds number on the heat transfer process of the system during the melting of a PCM.
Air Sparging for Mixing Non-Newtonian Slurries
Authors: Bamberger Judith Ann , Enderlin Carl W. , Tzemos S.
Published: May 2012

The mechanics of air sparger systems have been primarily investigated for aqueous-based Newtonian fluids. Tilton et al. (1982) [1] describes the fluid mechanics of air sparging systems in non-Newtonian fluids as having two primary flow regions. A center region surrounding the sparger, referred to as the region of bubbles (ROB), contains upward flow due to the buoyant driving force of the rising bubbles. In an annular region, outside the ROB, referred to as the zone of influence (ZOI), the fluid flow is reversed and is opposed to the direction of bubble rise. Outside the ZOI the fluid is unaffected by the air sparger system. The flow regime in the ROB is often turbulent, and the flow regime in the ZOI is laminar; the flow regime outside the ZOI is quiescent. Tests conducted with shear thinning non-Newtonian fluid in a 34-in. diameter tank showed that the ROB forms an approximately inverted cone that is the envelop of the bubble trajectories. The depth to which the air bubbles reach below the sparger nozzle is a linear function of the air-flow rate. The recirculation time through the ZOI was found to vary proportionally with the inverse square of the sparging air-flow rate. Visual observations of the ROB were made in both water and Carbopol®. The bubbles released from the sparge tube in Carbopol® were larger than those in water.
Implementing Effective Low-Cost Laboratory Experiments Into a Distance Engineering Program
Authors: Jernigan Shaphan R. , Fortney Bill , Fahmy Yusef , Buckner Gregory D.
Published: May 2012

This paper details the successful and inexpensive implementation of remote laboratory experiments into a control systems course using readily available hardware and software. The custom-made experiments include an inverted pendulum, a platform leveling system, a ball and beam apparatus, and an aerodynamic beach ball levitation system, each implemented in a separate course offering. With each laboratory, the control objective is to regulate a physical parameter, (pendulum angle, platform orientation, ball position, etc.) by manipulating voltage to a drive component (DC motor, linear actuator, blower, etc.). Engineering software commonly used in controls courses (MATLAB/Simulink and LabView) coupled with dedicated hardware (xPC Target and NI Compact Rio) provide the controller platforms, while Microsoft NetMeeting and standard Internet video conferencing equipment are used to interface the distance-learning students with the laboratory equipment. Both local students at North Carolina State University’s campus in Raleigh and distance students at the University of North Carolina at Asheville and Craven Community College in Havelock, NC complete the laboratory experiments. In a student survey, distance students participating in the remote labs rated the experience as favorably as local students. Course grades, including design project grades, were similar between the two groups.
Introducing a Novel Reactor Concept: Indirectly Fired Integrated Gasification and Steam Generation System
Authors: Alyaser Monem , Monaghan Rory , Beitelmal Abdlmonem , Fabris Drazen
Published: May 2012

This paper introduces a novel gasification reactor that uses steam gasification of carbonaceous feedstock by indirectly heating the reacting flow through a high temperature heat exchanger without the need for partial combustion with oxygen. It demonstrates the importance of gasification as a method for increasing power plant efficiency and reducing emissions. This paper also describes the computational model created to model this novel gasifier and the results of the model that illustrates the efficiency and purity advantages of the new gasifier. The reactor was modeled as a 1D counter-reacting flows heat exchanger, using the effectiveness-number of transfer units (ε-Ntu) method. The heating flow was assumed to be fully combusted at the inlet. The gasification stream was modeled as a plug flow, where the reaction is kinetically controlled. A simplified version of the Random Pore Model (RPM) was used to predict the char consumption. The results indicate that the gasification of coal with steam without partial combustion with oxygen using this new concept is feasible. The gasification reaction rates are found to be slow at temperatures less than 1200°C, but most of the char conversion, which reached about almost 100% completion, occurred at higher than 1200°C.
Fault Detection and Diagnostics in an Ocean Turbine Using Vibration Analysis
Authors: Mjit Mustapha , Beaujean Pierre-Philippe J. , Vendittis David J.
Published: May 2012

This paper describes the approach, procedure and techniques developed to evaluate the health of ocean turbines, based on vibration measurements and analyses. A LabVIEW model for on-line vibration condition monitoring, implemented with advanced diagnostic techniques features, was developed. In order to distinguish between a vibration amplitude change due to a developing fault and that due to a change in operating condition, this program includes the use of an ordering technique in the frequency domain, which relates the vibration to the machine speed. Some experiments were first performed on a commercial fan to illustrate and demonstrate the fault detection capability of the monitoring and diagnostics system. To increase the reliability of the monitoring system, and to demonstrate that it can be used for monitoring a wide range of machines, a second series of vibration data collection and monitoring events was performed on a small boat with different combination (on/off status) of the engine, hydraulic pump, generator and air conditioning. This allowed for the detection of the frequency components associated with each subsystem, alone and together, and enabled the detection of mechanical faults, such as imbalance and misalignment, if they existed. For long term monitoring, the model allow for the automatic storing of raw data either periodically and/or after any deviations from normal conditions, i.e., when alerts are on. This makes it possible to follow the progress (towards an alarm condition) of any faults without saving data continuously. In this way, measurements of unexpected events may be made without the vibration engineer’s physical presence, hopefully, early fault detection and diagnosis will avoid catastrophic failure from occurring. This enables the economic and efficient health monitoring of ocean turbines as they become operational.
Thermal-Enhanced and Cost-Effective 3D IC Integration With TSV (Through-Silicon Via) Interposers for High-Performance Applications
Authors: Lau John H. , Chan Y. S. , Lee S. W. Ricky
Published: May 2012

A low-cost (with bare chips) and high (electrical, thermal, and mechanical) performance 3D IC integration system-in-package (SiP) is designed and described. This system consists of a silicon interposer with through-silicon vias (TSV) [1–24] and redistribution layers (RDL), which carries the high-power flip chips with microbumps on its top surface and the low-power chips at its bottom surface. TSVs in the high- and low-power chips are optional but should be avoided. The backside of the high-power chips is attached to a heat spreader with or w/o a heat sink. This 3D IC integration system is supported (packaged) by a simple conventional organic substrate. The heat spreader (with or w/o heat sink) and the substrate are connected by a ring stiffener, which provides adequate standoff for the 3D IC integration system. This novel structural design offers potential solutions for high-power, high-performance, high pin-count, ultra fine-pitch, small real-estate, and low-cost applications. Thermal management and reliability of the proposed systems are demonstrated by simulations based on heat-transfer theory and time and temperature dependent creep theory.
Set-Based Design Method for the Early Phase Design of Structures With Uncertainties
Authors: Inoue Masato , Hattori Yutaka , Ishikawa Haruo
Published: May 2012

Since an early phase of design intrinsically contains uncertainties from various sources of variations, design performances are fluctuating or reflect uncertainty caused by uncertain design variables. Analysis tool such as finite element method (FEM) is useful for structural analysis. However, using unique point solution does not express information about uncertainties. Designers need to figure out an outline of the structural feature and have to obtain a design idea under some uncertain design information in a structural design at the early phase of design. We have proposed a preference set-based design (PSD) method that generates a ranged set of design solutions that satisfy sets of performance requirements. This study proposes a structural design method for the early phase of design based on the PSD method that is possible to analyze structure with design uncertainty by elastic FEM and obtain a ranged set of design solutions. That is, a design method for analyzing structures and obtaining a ranged set of design solutions with uncertainties of material property and dimension of structure (coordinates of geometry) under fluctuating distribution of performance characteristics of stress and displacement is proposed. In order to illustrate the availability of our approach, design problem of 3-dimensional truss structure is solved.
Effects of Nanoparticles and Polymer Additives in Turbulent Pipe Flow
Authors: Oztekin Alparslan , Neti Sudhakar , Ukaew Ananchai
Published: May 2012

Spatial and temporal characteristics of turbulent pipe flows using nanofluids and dilute polymer solutions are examined by means of instantaneous differential pressure and velocity measurements. Spherical and elongated nanosilica particles (SiO2) are mixed into water to make nanofluid and polyacrylamide (PAC) is dissolved into water to make PAC solution. The effects of nanofluid on the drag reduction and turbulent structure are determined and compared with the effects of polymer additives on the turbulent structures and drag reduction. Suppression of turbulence near pipe wall was observed with the introduction of both spherical and elongated nanoparticles. Although experimental results show that nanofluids are not candidates for drag reduction unlike polymer additives, they do not increase pressure drop. Hence addition of nanoparticles into heat transfer fluids could have the potential for heat transfer enhancement in pipe flow without paying the penalty of increasing pumping power.
Analyses of Centrifugal Compressor Performance Impacts on Volute and Scroll
Authors: Xu C. , Amano R. S.
Published: May 2012

Volute is used to collect and transport swirling gas produced by impeller or diffuser. Design of the volute not only impacts compressor efficiency but also influences the operating ranges of the compressor. In this study, Navier-Stokes equations combined with an algebra turbulence model were used to simulate flows inside a single stage compressor. Detailed flow simulations for a large cut back tongue volute are presented and discussed. A rounded tongue volute was tested in a single stage test rig. The compressor stage performance tests were conducted in the test lab and static pressure taps were used to measure static pressures at volute internal walls at locations of θ = 240° and 360°. Thermal couples and other static pressure probes were instrumented at inlet and outlet of the compressor for performance tests. The numerical results were compared with experiments and good agreements are found. Studies showed that a large cut back rounded tongue volute provided good operating range without dramatically dropping compressor peak efficiency.
Atomic force microscopy and x-ray diffraction studies on agglomeration phenomena of ultrathin Au/Fe bilayers
Authors: Kamiko Masao , Koo Jung-Woo , Kim Jae-Min , Ha Jae-Geun
Published: May 2012

The agglomeration phenomena of a few nanometer thick Au/Fe bilayers, grown on an MgO(100) substrate, were studied by using atomic force microscopy and x ray diffraction (XRD). The authors found that the insertion of an Fe ultrathin layer between an MgO(100) substrate and a 4 nm thick Au layer promotes the agglomeration process of the Au layer, in which the bilayer structure changes into large Fe/Au islands of ∼200 nm in diameter. In addition, XRD results revealed that the Au in the agglomerated islands has only a (111)-crystallographic orientation, presumably caused by reducing the large surface energy of Au on the MgO(001) substrate. These findings are quite different from cases in which structural stabilization is achieved by inserting an Fe seeding layer of a few nanometers on an MgO(001) substrate.
Remote H2/N2 plasma processes for simultaneous preparation of low-k interlayer dielectric and interconnect copper surfaces
Authors: Liu Xin , Gill Sandeep , Tang Fu , King Sean W. , Nemanich Robert J.
Published: May 2012

This study focuses on the simultaneous plasma treatment of interlayer dielectric (ILD) and chemical mechanical polished (CMP) Cu surfaces using N2/H2 plasma processes. The modifications induced by the gas chemistries are investigated for two ILD films with different porosities and carbon concentrations. H atoms and radicals in the plasma react with the carbon groups leading to carbon removal for both of the ILD films. Fourier transfer infrared (FTIR) spectra show a greater fractional reduction of CH3 in the high porosity ILD compared to the low porosity ILD. Results indicate that an N2 plasma forms an amidelike layer on the surface, which apparently leads to reduced carbon abstraction from an H plasma process. In addition, FTIR spectra indicate the formation of hydroxyl (SiOH) groups following the plasma exposure. Increased temperature (380 °C) processing leads to a reduction of the hydroxyl group formation compared to ambient temperature processes, and the dielectric constant is increased by a smaller amount. It appears that the increase of the dielectric constant is mainly attributed to moisture uptake rather than network topography change due to carbon loss. The plasma experiments were repeated with CMP Cu surfaces at both ambient temperature and 380 °C. The carbonate contamination was removed by an H2 plasma process at elevated temperature while the CC and CH contamination was removed by an N2 plasma process at elevated temperature.
Novel surface chemical synthesis route for large area graphene-on-insulator films
Authors: Raghavan Srikanth , Denig Tobias J. , Nelson Timothy C. , Stinespring Charter D.
Published: May 2012

The feasibility of a halogen-based surface chemical route to the synthesis of large area graphene-on-insulator films is reported. Both CF4- and Cl2-based plasmas have been used to etch 6H-SiC (0001) surfaces, which were then annealed at 970 °C. These surfaces were characterized using x-ray photoelectron spectroscopy, reflection high energy electron diffraction, atomic force microscopy, and Raman spectroscopy. It was shown that the etching process leads to selective removal of silicon from the SiC matrix to produce carbon rich surface layers. When annealed, these layers reconstruct to form a graphene film. Electrical measurements indicated the resistivity and carrier density of these films are similar to those of few layer graphene.
Secreted Peptide Dilp8 Coordinates
Drosophila
Tissue Growth with Developmental Timing
Authors: Colombani Julien , Andersen Ditte S. , Léopold Pierre
Published: May 2012

Small But Perfectly Formed

The imaginal discs of
Drosophila
represent defined larval tissues that give rise to the subsequent adult appendages. These tissues regenerate in response to damage. When the imaginal discs are injured or show tumor growth, they signal to the rest of the larval animal to slow down growth and delay morphogenesis.

Garelli
et al.

(p.
579
) and

Colombani
et al.

(p.
582
) now show that an insulin-like peptide, termed Dilp8, is secreted into the hemolymph (insect “blood”) and participates in the communication between growing organs and the endocrine system to adjust the growth program and maturation time. This collaboration ensures that adults attain the normal size and maintain appropriate proportions and symmetry.
Imaginal Discs Secrete Insulin-Like Peptide 8 to Mediate Plasticity of Growth and Maturation
Authors: Garelli Andres , Gontijo Alisson M. , Miguela Veronica , Caparros Esther , Dominguez Maria
Published: May 2012

Small But Perfectly Formed

The imaginal discs of
Drosophila
represent defined larval tissues that give rise to the subsequent adult appendages. These tissues regenerate in response to damage. When the imaginal discs are injured or show tumor growth, they signal to the rest of the larval animal to slow down growth and delay morphogenesis.

Garelli
et al.

(p.
579
) and

Colombani
et al.

(p.
582
) now show that an insulin-like peptide, termed Dilp8, is secreted into the hemolymph (insect “blood”) and participates in the communication between growing organs and the endocrine system to adjust the growth program and maturation time. This collaboration ensures that adults attain the normal size and maintain appropriate proportions and symmetry.
Removal of Shelterin Reveals the Telomere End-Protection Problem
Authors: Sfeir Agnel , de Lange Titia
Published: May 2012

Not Broken Until Repaired

Humans, and indeed most eukaryotes, have linear chromosomes with two DNA ends, known as telomeres. Cells have evolved sophisticated systems to repair broken chromosomes, which specifically recognize DNA ends as damage. Telomeres are protected from these repair systems, which would otherwise wreak havoc in the cell, causing genome aberrations that, ironically, can lead to cancer. To understand all the possible threats to telomeres
Sfeir and de Lange
(p.
593
) mutated components of the mouse shelterin protein complex, which forms a protective cap over the telomere ends, rendering telomeres completely devoid of the complex (and packaged only in nucleosomal chromatin). These “naked” telomeres were vulnerable to six DNA repair–related pathways: classical and alternative nonhomologous end joining; ATM and ATR signaling pathways; homology directed recombination; and unmitigated DNA resection.