bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Servo Control for Underactuated Mechanical Systems
Authors: Cheng Hongtai , Chen Heping , Zhang Xiaohua , Chen Hongjun
Published: October 2013

Due to the lack of control inputs, the motion range and application areas of underactuated mechanical system are greatly limited. To overcome such difficulties, the arbitrary state point dynamic tracking problem named dynamical servo control is discussed in this paper. Considering simplicity and repeatability, periodic trajectory is the best way leading to the desired point. Virtual constraints concept is employed and a target oriented trajectory planning procedure is proposed, which can generate periodic dynamic compatible and desired point crossing trajectory. A Lyapunov based tracking controller is proposed to avoid the strict conditions for using a traditional LQR based method. Experiments are performed on an Acrobot prototype and verify the correctness of the proposed periodic trajectory generating method and the effectiveness of the tracking controller.
Fabrication of Perforated Conical Nanopores in Freestanding Polymer Membranes Using Nanoimprint Lithography and Pressed Self-Perfection Method
Authors: Choi Junseo , Farshchian Bahador , Park Sunggook
Published: October 2013

Nanopores have proven to be an important sensing element in biosensors to detect and analyze single biomolecules such as DNAs, RNAs, or proteins. The charged biomolecules are driven by an electric field and detected as transient current blocks associated with their translocation through the pores. While protein nanopores, such as alpha-hemolysin and MspA protein nanopores embedded within a lipid bilayer membrane [1], promise to be a rapid, sensitive and label-free sensing paradigm, their duration of usage is too short to perform repetitive experiments due to the mechanical instability of the lipid bilayer. A variety of methods have been developed to prepare synthetic nanopores, which can substrate for protein nanopores, including a direct milling with a focused high-energy electron or ion beam in insulating substrates, an ion track etching in polymer substrates, and an anodizing in aluminum substrates. However, those methods do not allow for control over both the size and location of pores and the high yield of production.
A Multiphysics Reduced Order Model of Valve Pumping in a 4-Stage Vacuum Micropump
Authors: Kumar Karthik , Besharatian Ali , Bernal Luis P. , Peterson Rebecca L. , Najafi Khalil
Published: October 2013

Micro pumps are required in gas chromatographs and other gas analysis systems. Thermodynamic and reduced order models reported in the literature consider only the deflection of pumping membranes which is insufficient to study the performance characteristics of more complicated multistage peristaltic pumps with multiple coupled chambers, active checkerboard valves and single or multiple electrodes for actuating the pumping membranes and valves. Specifically the volume displaced by the valves membranes can be significant compared to the volume displaced by the pumping membranes. In this paper a multiphysics model is extended to include the effect of valves as well the pump membranes deflections. The viscous losses in the flow through the valves are modeled using CFD while the structural behavior of the membrane is modeled using COMSOL in quasi-steady analyses and the results incorporated into the multiphysics unsteady reduced-order model. The model is validated by comparing computed flow-rate as a function of frequency with experimental results for a 4-stage micropump which are found to be within 7%. At a high flow rate condition the model results show that for a 4-stage pump the deflection of the valves significantly affects the performance of the pump.
Extended Finite Element Analysis of Journal Bearing Dynamic Forced Performance to Include Fluid Inertia Force Coefficients
Authors: San Andrés Luis
Published: October 2013

Reynolds equation governs the generation of hydrodynamic pressure in oil lubricated fluid film bearings. The static and dynamic forced response of a bearing is obtained from integration of the film pressure on the bearing surface. For small amplitude journal motions, a linear analysis represents the fluid film bearing reaction forces as proportional to the journal center displacements and velocity components through four stiffness and four damping coefficients. These force coefficients are integrated into rotor-bearing system structural analysis for prediction of the system stability and the synchronous response to imbalance. Fluid inertia force coefficients, those relating reaction forces to journal center accelerations, are routinely ignored because most oil lubricated bearings operate at relatively low Reynolds numbers, i.e., under slow flow conditions. Modern rotating machinery operates at ever increasing surface speeds to deliver more power in smaller size units. Under these operating conditions fluid inertia effects need to be accounted for in the forced response of oil lubricated bearings, as recent experimental test data also reveal. The paper presents a finite element formulation to predict added mass coefficients in oil lubricated bearings by extending a basic formulation that already calculates the bearing stiffness and damping force coefficients. That is, a small amplitude perturbation analysis of the lubrication flow equations keeps the temporal fluid inertia effects and develops a set of equations to obtain the bearing stiffness, damping and inertia force coefficients. The method does not impose on the cost of the original formulation which makes it very attractive for ready implementation in existing software. Predictions of the computational model are benchmarked against archival test data for an oil-lubricated pressure dam bearing supporting large compressors. The comparisons show fluid inertia effects cannot be ignored for operation at high rotor speeds and with small static loads.
A Comparison of Oil-Water Flow and Oil-Gas Flow in Capillary Model
Authors: Zhang Yihe , Dai Liming
Published: October 2013

A capillary model is employed to study the slug flow behavior in pore structure. Oil-water system and oil-gas system are investigated in the experiments. During the flow process, it is observed that the wetting phase liquid will generate a thin liquid film on the inner surface of the tube wall, and the liquid film plays an important role in capillary flow. At the meantime, the pressure drop across the tube is recorded during the experiment, result shows that the pressure drop magnitude is proportional to the oil slug length, while it is not significantly affected by the liquid injecting velocity.
Analysis of TSV/Micro-Bump Deformation due to Chip Misalignment and Thermal Processing in 3D IC Packages
Authors: Johnson R. W. , Shen Y.-L.
Published: October 2013

Misalignment of chips in three-dimensional (3D) integrated circuit (IC) packages subjects the bonding layer between chips to shear deformation. Chip warpage and thermal effects from chip processing can further compound the problem. In this study we perform a numerical assessment on the shear and thermally-induced deformations in and around the through-silicon vias (TSV) and solder micro-bumps. The 3D finite element model features a TSV/micro-bump bonding structure connecting two adjacent silicon chips, with and without an underfill layer in between. The possibility that the entire solder micro-bump may be transformed into an intermetallic is also considered in this study. We seek to parametrically explore the trend of stress and deformation fields due to misalignment-induced shear deformation and thermal expansion mismatch. Potential for damage initiation in the TSV/micro-bump is examined by the measure of plastic strain accumulation. The existence of an underfill layer around the TSV/micro-bump enhances the overall resistance to shear deformation, although with a higher buildup of local stresses. The TSV and silicon chip are less affected by misalignment than by thermal expansion mismatches.
Numerical Investigation of Electronic Liquid Cooling Based on the Thermomagnetic Effect
Authors: Karimi-Moghaddam Giti , Gould Richard D. , Bhattacharya Subhashish
Published: October 2013

Liquid cooling for thermal management has been widely applied in high power electronic systems. Use of pumps may often introduce reliability and mechanical limitations such as vibration of moving parts, noise problems, leakage problems, and considerable power consumption. This paper presents a theoretical design of circulating a liquid coolant using magnetic and thermal fields which surround high power electronic systems by means of thermomagnetic effects of temperature sensitive magnetic fluids. Numerical simulation models of the heat transfer process from a magnetic liquid contained in a closed flow loop in the presence of an external magnetic field have been developed. These models include the coupling of three fundamental phenomena, i.e. magnetic, thermal, and fluid dynamic features. In this cooling device, the thermomagnetic convection is generated by a non-uniform magnetic field from a solenoid, which is placed close to the fluid loop. The device cooling load is calculated in the region near the solenoid. No energy is needed, other than the heat load (i.e. waste heat from actual electrical device), to drive the cooling system, and as such, the device can be considered completely self-powered. In effect, the heat added to the ferrofluid in the presence of a magnetic field is converted into useful flow work. In this numerical study, the effects of different factors such as input heat load, magnetic field strength and magnetic distribution (based on solenoid dimensions and the applied electrical current) along the loop, on the performance of the cooling system are analyzed and discussed. Finally, the variation of the local Nusselt number along the heated and cooled regions of the flow loop are calculated and compared with laminar entry length analytical solutions.
Design and Build Methods for a Variable Radius Wheel Mechanism
Authors: Chen Yin M. , Cappelleri David
Published: October 2013

One of the main concerns regarding robotic mobility is its ability to traverse different types of terrain. As we know from our own experiences driving and riding wheeled vehicles, different types of wheels are better for different applications. In the same vein, giving robots wheels of variable radius can change the torque needed to traverse the terrain, the speed of the vehicle, and the way the vehicle handles the roughness of the terrain. In our prior research of basic modes of mobility, we were able to identify a method for creating a variable radius wheel mechanism. This paper will focus on the mechanical manipulation needed to actuate the mechanism as well as several different ways to implement it. In application, one mechanism can be the sole mobility source for a robot or a few can be chained together to create a more conventional system. This mechanism can be used to give us more versatility in our application scope as well as provide us with more control over the vertical motion of the Center of Mass of a robotic vehicle.
Sequential vs. Parallel Synthesis for Dual-Stage Hard Disk Drives
Authors: Stensland Craig E. , Bedillion Mark
Published: October 2013

Modern hard disk drives (HDDs) use single-input, dual-output (SIDO) controllers to control a dual-stage plant consisting of a large-stroke voice coil motor (VCM) and a short-stroke, high-bandwidth piezoelectric microactuator (PZT). Various methods have been proposed to perform the SIDO controller design; among the most commonly used approaches is μ-synthesis. While μ-synthesis generates stable controllers for the overall system, it does not guarantee stability of the VCM-only loop in the presence of microactuator saturation or failure. One approach to the DISO design that maintains VCM-only stability is the sequential design of VCM and PZT controllers. This paper presents a systematic study of sequential vs. parallel design. Designs are evaluated by comparing values of μ obtained for equivalent designs between the sequential and parallel approaches. The circle criterion is used to test stability of the system under saturation. Performance of sequential and parallel designs in shock events are tested in simulation.
Assessment of Embedded Water Needs at a Mixed-Use Facility in Palo Alto, California
Authors: Clayton Mary , Webber Michael E.
Published: October 2013

Assessing and mitigating the water footprint of a business can reduce the risks associated with potential freshwater shortages. Because water is vital in the supply chain and operations of all major industries, depletion of freshwater sources, increases in demand of water, and droughts can threaten a company’s production, financial stability, and reputation. Consequently, it is essential to identify water vulnerability in a business’s operational portfolio and to ensure that the business’s water management aligns with its overall sustainability strategies. Furthermore, understanding a business’s water footprint allows for effective resource management, which can help minimize costs and reduce its environmental impact.

Currently, interest in the water footprints of organizations, products, and services is increasing, creating a need for a shared standard of definitions and methodologies for water metering and reporting. In addition, consistent methodologies for including embedded and indirect water use and a uniform application of analysis boundaries need to be developed. This research aims to develop an accounting methodology for water reporting along with tools for identifying opportunities to improve water efficiency. Additionally, existing definitions, approaches, and best practices for measuring, reporting, and managing water use across different industries are summarized. A conceptual model was developed to evaluate the lifecycle water footprint, including direct and indirect (embedded in energy and materials) water use in both supply chains and operations. Further, a case study is considered to assess the water impact of a mixed-use facility in Palo, Alto, California. Comprehensive water, electricity, and gas metering data were collected for this site, and the water uses of California’s energy mix were determined. Finally, this data set was utilized to summarize direct and indirect water use at a corporate site, and recommendations of water conservation and reuse for this site are considered. Future work includes development of validation and optimization approaches for minimizing water usage. The model was built such that it can be expanded to include multiple sites in the global supply chain in order to estimate worldwide water usage throughout a large company’s operations.
Passive Evaporative Cooler for Malaria Testing in Developing Countries
Authors: Lucero-Bernhardt Briana , Turner Cameron
Published: October 2013

A top-wicking cooler box was designed for this purpose and included an experimental and theoretical analysis of an evaporative cooling technique utilizing mounted water troughs and a single transfer surface. Construction and insulation material, cooling capabilities, and environmental sustainability were compared between two boxes with different dimensions. The smaller boxes were found to be more effective due to a smaller ratio of volume to surface area, which resulted in higher cooler system effectiveness than the larger boxes. Regardless of the roofing metal, it was found that the square dimensioned boxes were unsuitable to sufficiently cool numerous RDTs irrespective of their scaling. Future testing on rectangular boxes and additional evaporative cooling options warrant further investigation.
Improving the Pumping Efficiency of a Micropump Using Hydrophobic Nanocomposite Coating
Authors: Askari Davood , Islam Nazmul
Published: October 2013

This paper describes the improvement of bidirectional micropump velocity by deposition of a hydrophobic nanocomposite thin layer. A polymer base nanocomposite coating consisting of a homogeneous mixture of Silicon nanoparticles in polydimithylsiloxane (PDMS) is used to improve the hydrophobicity of the micropump surfaces. For hydrophobic nature of PDMS and the monolayer coating with nanoscale surface roughness, the hydrophilic surface of a biased AC electroosmotic micropump will transform to a hydrophobic surface. Here in this work, improvement of the micropump velocity is investigated through a surface modification process. This paper will also discuss the synthesis process and characteristics of the polymer base nanocomposite monolayer. In addition to hydrophobicity improvement, adding a thin nanocomposite monolayer will separate the electrodes from the pumping liquid, thus eliminating their reaction, which is usually observed due to the application of voltage. As a result, higher voltages can be applied to the electrodes and higher pumping rates are achievable.
Performance Analysis of a Modular Air Cooled Condenser for a Concentrated Solar Power Plant
Authors: Moore J. , Grimes R. , Walsh E. J.
Published: October 2013

The use of air cooled condensers in power generation facilities is increasing in arid regions around the world. There is a specific requirement for more efficient air cooling technologies to be developed for Concentrated Solar Power (CSP) plants. This paper aims at determining the effects of various condenser design features on CSP plant output. In particular this paper considers a modular condenser and focuses on designing a suitable compact heat sink to be coupled with a variable speed fan array. Tube banks with radial fins have been used for decades to heat and cool gases and numerous correlations exist to predict the performance of such a heat exchanger. The initial design of this air-cooled condenser is essentially a tube bundle consisting of 6 rows of helically finned round tubes in an equilateral staggered arrangement. A laboratory-scale steady state test facility was designed to investigate the accuracy of the relevant correlations for the given design. Due to an undesired phenomenon which exists in multi-row condensers known as backflow, an investigation was performed to analyze the performance of the tube bank with fewer tube rows. The thermal and hydraulic performance for a tube bundle with a different number of tube rows was measured and found to be within 10–18% of the existing correlations. New correlations for heat transfer and pressure drop for the given design are presented for greater accuracy in the calculation of the condenser performance. These correlations, based on the measured data were combined with performance characteristics from a steam turbine to model the thermodynamic plant performance incorporating the various condenser designs. The investigation shows that for each condenser size, design and ambient temperature, an optimum fan speed exists which maximizes plant output. Further analysis shows that for a 1000 module condenser, a 4 row condenser results in the highest plant output, with a loss in efficiency due to condenser operation of 1.85%. A 2 row condenser also performs relatively well with 600 or more modules. This analysis shows that a condenser consisting of a series of such modules, can tightly control and optimize the net plant output power by simply varying fan speed.
2D Structures-Based Energy Management Nanofluids
Authors: Taha-Tijerina Jaime , Narayanan T. N. , Avali Soorya , Ajayan P. M.
Published: October 2013

Designing of compact electronic and electrical instruments needs the development of high efficient thermal and electrical management fluids. Recent advances in layered materials enable large scale synthesis of diverse two-dimensional (2D) structures. Some of these 2D materials are good choices as nanofillers in heat/electrical energy transfer fluids; mainly due to their high surface area available for energy conduction. Among various 2D nanostructures, hexagonal boron nitride (h-BN) or graphene (G) exhibit versatile properties such as outstanding thermal conductivity (TC), excellent mechanical stability, and remarkable chemical inertness. These 2D nanostructures have been used to create composite fluids for diverse thermal management applications, such as microelectronics, high voltage power transmission systems, automobiles, solar cells, biopharmaceuticals, medical therapy/diagnosis, and nuclear cooling, among others. The ever increasing thermal loads in applications now require advanced operational fluids, like high TC dielectric insulating fluids for electrical transformers. These fluids require superb filler dispersion, high thermal conduction, as well as electrical insulation. Such thermal oils that conform to this thermal/electrical requirement, and yet remain in highly suspended stable state, have not yet been synthesized. We discuss the synthesis and characterization of stable high TC and electrically conducting and non-conducting Newtonian nanofluids using liquid exfoliated layers of h-BN and G in dielectric mineral oil.
Sensitivity Analysis of Micropart Motion on a Controlled Deformable Continuous Surface
Authors: Rizwan Mohsin , Shiakolas Panos S.
Published: October 2013

Various approaches have been investigated for micropart (∼250 μm in size) manipulation especially for their controlled positioning for automated assembly of MEMS devices. The motion dynamics of a micropart in a dry-friction environment due to controlled deformation of a continuous flexible surface have been developed and are used to study the sensitivity of micropart motion and micropositioning as function of micropart and surface material properties and input actuator properties. The dynamics consider Van der Waal’s forces, effects of surface deformation profile, relative surface roughness, the dynamic compression of asperities and their effect on the dynamic friction coefficient based on extending Kogut-Etsion friction model through a quasi-dynamic coefficient of friction estimation. The motion of the micropart is affected by these parameters, and it is found that for some combinations of parameters a range exists that could cause motion while outside this range either there is no motion or the micropart detaches from the surface. The understanding of the effects of these parameters on micropart motion could pave the way towards controlled micropart translocation and manipulation employing a continuous flexible surface for microassembly, processes requiring controlled micropart handling for homogeneous or heterogeneous microdevice mass production, or for the development of microconveyor systems.
Optimal Design of Axe-Symmetric Diffuser via Genetic Algorithm and Ball-Spine Inverse Design Method
Authors: Vaghefi Navid S. , Nili Ahmadabadi Mahdi , Roshani Mohammad R.
Published: October 2013

In this research, an optimal aerodynamic design of an axe-symmetric diffuser is performed via combination of a developed boundary layer numerical code, BSA inverse design Algorithm and genetic optimization algorithm. To do this, developed numerical boundary layer code is incorporated into the genetic algorithm to reach to an optimum pressure distribution on the wall in such a way that the maximum pressure recovery is obtained without separation. To validate the developed boundary layer code, the calculated quantities are compared with Blasius and Howart’s analytical results. Then, the optimized pressure distribution will be the candidate “target pressure distribution” for the inverse design algorithm to find out the relevant optimum geometry. Geometry modification takes place based on the combination of Ball-Spine algorithm and fluent software as the flow field solver. Implementation of this combination is completed through User Defined Function (UDF) feature of Fluent. Fluent advantageous provides the capabilities for extension of the proposed method to turbulent flows, complicated geometries and employment of both structured and unstructured grids. To show the true performance of the proposed method of inverse design, several issues have been investigated for different initial guess. To validate the effect of the presented method, increased pressure coefficient for an optimized diffuser is illustrated.
Potential of Phase Change Material-Enhanced Constructions in Commercial Buildings
Authors: Naimaster Edward J. , Sleiti Ahmad K.
Published: October 2013

Buildings account for a significant portion of the total energy consumption in the US, especially the energy-inefficient commercial building sector. As part of the future path towards realizing net zero energy buildings, innovative energy-efficient technologies must be developed. In this study, the potential of phase change material (PCM)-enhanced constructions to lower HVAC energy consumption in a commercial building was investigated.

A commercially available fatty acid-based PCM product was selected due promising thermal and chemical properties. Differential scanning calorimetry (DSC) was used in isothermal step mode to accurately measure the latent heat energy storage of the PCM. A US DOE commercial reference building model with a PCM-enhanced ceiling was simulated using a finite-difference conduction heat transfer algorithm in EnergyPlus to determine the effects of the PCM on the building energy performance.

It was found that, although the PCM-enhanced ceiling had a beneficial stabilizing effect on the interior surface temperature of the ceiling, the zone mean air temperatures were not significantly altered. As such, minimal HVAC energy savings were seen. Future work should focus on the potential of active PCM constructions, which could successfully remove stored thermal energy from the PCM without increasing the space cooling energy consumption.
Multi-Objective Optimization for the Sustainable-Resilient Synthesis/Design/Operation of a Power Network Coupled to Distributed Power Producers via Microgrids
Authors: Cano-Andrade Sergio , von Spakovsky Michael R. , Fuentes Alejandro , Lo Prete Chiara , Hobbs Benjamin F. , Mili Lamine
Published: October 2013

In this paper, multiobjective optimization is proposed for evaluating the sustainable synthesis/design and operation of sets of small renewable and non-renewable energy production technologies coupled to power production/transmission/distribution networks via microgrids. The optimization is conducted over a quasi-stationary twenty four hour, winter period. Partial load behavior of the generators is included by introducing non-linear functions for efficiency, costs and emissions as a function of the electricity generated by each technology. A new index for resiliency is included in the multiobjective optimization model in order to account for the capacity of the power network system to self-recover to a new normal state after experiencing an unanticipated catastrophic event. Since sustainability/resiliency indices are typically not expressed in the same units, fuzzy logic and an explicit set of weighting factor methods are employed to calculate a composite sustainability-resiliency index. Results indicate for the particular problem posed that the inclusion of microgrids into the network leads to a better overall network efficiency, a reduction in life cycle costs, and an improved network resiliency. On the other hand, total life SO2 emissions and network reliability are not improved for this particular case when microgrids are included.
Low-Variance Monte Carlo Simulation of Thermal Transport in Graphene
Authors: Landon Colin , Hadjiconstantinou Nicolas G.
Published: October 2013

Due to its unique thermal properties, graphene has generated considerable interest in the context of thermal management applications. In order to correctly treat heat transfer in this material, while still reaching device-level length and time scales, a kinetic description, such as the Boltzmann transport equation, is typically required. We present a Monte Carlo method for obtaining numerical solutions of this description that dramatically outperforms traditional Monte Carlo approaches by simulating only the deviation from equilibrium. We validate the simulation method using an analytical solution of the Boltzmann equation for long graphene nanoribbons; we also use this result to characterize the error associated with previous approximate solutions of this problem.
Influence of Tool Holder Material on Interfacial, Insert and Tool Holder Temperatures During Turning Operation of Gray Iron
Authors: Kaminise Almir K. , Guimaraes Gilmar , Da Silva Marcio B.
Published: October 2013

Usually studies related to machining temperature consider a system comprised of workpiece, chip and cutting tool, the effect of tool holder material is not taken in account. However, due to its physical properties, the tool holder material, usually carbon steel, has effect in the dissipation of the heat generated. This work studies the effect of the tool holder material on the temperature distribution during the turning operation of gray iron using cemented carbide cutting tool and without cutting fluid. Five tool holders were manufactured from materials with different heat conductivity: carbon steel, stainless steel, titanium, copper and bronze. Temperatures in eight different positions in the tool holder and cutting insert were measured. The average temperature at the chip tool interface was also measured using the tool-work thermocouple method. The results showed that the measured chip tool interface temperature was less affected by the tool holder material, although the temperature distribution at the cutting tool is highly affected.
Fatigue Behavior and Microstructure of Pt-20Ir Wire as Lead Conductor in Implantable Medical Device
Authors: Li Bernard Q. , Cho Kailynn , Zhang Haitao
Published: October 2013

Pt-20Ir cold draw wire has been used as lead conductor in implantable medical devices. The lead is a medical device to transfer the electrical signal from a implanted stimulator to the body area for stimulating such as brain and neurological nerves. In this study, fatigue behavior and failure mechanism of Pt-20Ir wire was studied with rotary bending fatigue testing. The relations between the cyclic strain amplitude (ε) and the cycles to failure (N) were obtained and compared with MP35N wire which is the most commonly used metal wire as lead conductors. The results show Pt-20Ir cold drawn wire (0.102 mm) has a fatigue endurance strain limit of 0.18% which is significant lower than that of MP35N wire.

Microstructure of Pt-20Ir cold draw wire was also analyzed. Results show that the grain size of in wire is elongated like bundled fiber structure. The texture of wire is strongly fiber textured and with a strong gradient from outside layer to center of the wire. Near surface region has <111> textured grain and around center region of the wire has <100> textured grain. The center of grain also has larger size than near surface.
Dynamic Analysis and Sliding Mode Control of a Novel Extendable Modular Multi-DOFs Link
Authors: Yi Hak , Yoo Je Hong , Langari Reza
Published: October 2013

In this paper, we have considered the new extendable modular multi-DOFs link to have a larger reachable workspace and more dexterous manipulability, as compared to a typical link. As a part of the extendable modular robot (EMR), our link is implemented to allow free motion when performing required tasks. In addition, this paper deals with a function of adjusting the link’s length (within 25% of the nominal length). Our investigation also focuses on the dynamics of a multi-DOFs link and the nonlinear controller for a given trajectory. The simulation results show the effectiveness of this control approach.
Heat Transfer in Thermal Lattice Boltzmann Equation Method
Authors: Li Like , Mei Renwei , Klausner James F.
Published: October 2013

The evaluation of the boundary heat flux and total heat transfer in the lattice Boltzmann equation (LBE) simulations is investigated. The boundary heat fluxes in the discrete velocity directions of the thermal LBE (TLBE) model are obtained directly from the temperature distribution functions at the lattice nodes. With the rectangular lattice uniformly spaced the effective surface area for the discrete heat flux is the unit spacing distance, thus the heat flux integration becomes simply a summation of all the discrete heat fluxes with constant surface areas. The present method for the evaluation of total heat transfer is very efficient and robust for curved boundaries because it does not require the determination of the normal heat flux on the boundary and the surface area. To validate its applicability and accuracy, several numerical tests with analytical solutions are conducted, including 2-dimensional (2D) steady thermal flow in a channel, 1-D transient heat conduction in an inclined semi-infinite solid, 2-D transient conduction inside a circle, and 3-D steady thermal flow in a circular pipe. For straight boundaries perpendicular to one of the discrete velocity vectors, the total heat transfer is second-order accurate. For curved boundaries only first-order accuracy is obtained for the total heat transfer due to the irregularly distributed lattice fractions cut by the curved boundary.
Modeling of Nano-Particle Reinforced Resin-Based Dental Composites
Authors: Hua Yi , Gu Linxia
Published: October 2013

The objective of this work is to predict the effective material properties of nano-particle reinforced resin-based dental composites using the Mori-Tanaka theory. The results were validated against the finite element simulation of a representative volume element of the microstructure. The influences of nano-particle properties, aspect ratio and volume fraction were examined in terms of effective Young’s modulus and yield strength of the composite. Cohesive material will be used to assess the damage at inter-phase.
Effects of Spindle Speed on Turning Stability
Authors: Dassanayake Achala V. , Suh C. Steve
Published: October 2013

Machining stability study for rough cuts suggests that low speeds impart instability. However, bifurcated states could be staged in between with increasing speeds. Therefore it cannot be concluded that speed increase would always result in stability. Using the cutting model presented in [1] and [2], critical DOCs are seen to increase with the increase of speed. Cutting force amplitude oscillations are determined by the nonlinearity of the force, not by speed increments. While both the tool and workpiece show similar instability stages most of the times, however, when it is closer to the critical depth-of-cut, the tool reaches instability first before the workpiece does. In contrast to the observation, when DOC is less than 1.00mm, most of the times when system is unstable, only the workpiece or the tool is unstable, but not both.
Third-Order Muscle Models: The Role of Oscillatory Behavior in Force Control
Authors: Piovesan Davide , Pierobon Alberto , Mussa-Ivaldi Ferdinando A.
Published: October 2013

This paper presents the analysis of a third-order linear differential equation representing a muscle-tendon system, including the identification of critical damping conditions.

We analytically verified that this model is required for a faithful representation of muscle-skeletal muscles and provided numerical examples using the biomechanical properties of muscles and tendon reported in the literature.

We proved the existence of a theoretical threshold for the ratio between tendon and muscle stiffness above which critical damping can never be achieved, thus resulting in an oscillatory free response of the system, independently of the value of the damping. Oscillation of the limb can be compensated only by active control, which requires creating an internal model of the limb mechanics.

We demonstrated that, when admissible, over-damping of the muscle-tendon system occurs for damping values included within a finite interval between two separate critical limits. The same interval is a semi-infinite region in second-order models. Moreover, an increase in damping beyond the second critical point rapidly brings the system to mechanical instability.
Net Energy and CO2 Emissions Analysis of Using MRF Residue as Solid Recovered Fuel at Coal Fired Power Plants
Authors: Breckel Alex C. , Fyffe John R. , Webber Michael E.
Published: October 2013

According to the waste management hierarchy published by the U.S. EPA, waste reduction and reuse are the most preferred modes of waste management, followed by recycling, energy recovery and lastly disposal. As many communities in the U.S. work towards sustainable waste management practices, recycling tends to be a cost-effective and common solution for handling municipal solid waste. With the introduction of single-stream recycling and automated materials recovery facilities (MRFs), where commingled recyclables are sorted into various commodity streams for sale to recycling facilities, recycling rates have steadily climbed in recent years. Despite increasing total recycling rates, contamination and diminishing returns for higher recovery ratios causes MRFs to landfill 5–25% of the incoming recycling stream as residue. This residue stream is composed primarily of plastics and fiber, both of which have high energy content that could be recovered instead of buried in a landfill. Plastics in particular are reported to have heat contents similar to fossil fuels, making energy recovery a viable end-of-life pathway. Sorting, shredding and densifying the residue stream to form solid recovered fuel (SRF) pellets for use as an alternative fuel yields energy recovery, displaced fossil fuels and landfill avoidance, moving more disposed refuse up the waste management hierarchy. Previous studies have shown that plastic, paper, and plastic-paper mixes are well suited for conversion to SRF and combustion for energy production. However, these studies focused on relatively homogenous and predictable material streams. MRF residue is not homogenous and has only a moderate degree of predictability, and thus poses several technical challenges for conversion to SRF and for straightforward energy and emissions analysis.

This research seeks to understand the energetic and environmental tradeoffs associated with converting MRF residue into SRF for co-firing in pulverized coal power plants. A technical analysis is presented that compares a residue-to-SRF scenario to a residue-to-landfill scenario to estimate non-obvious energy and emissions tradeoffs associated with this alternative end-of-life scenario for MRF residue. Sensitivity to key assumptions was analyzed by considering facility proximity, landfill gas capture efficiency, conversion ratio of residue to SRF and the mass of residue used.

The results of this study indicate that the use of MRF residue derived SRF in coal fired steam-electricity power plants realizes meaningful reductions of emissions, primary energy consumption, coal use and landfill deposition.
Circuit Development of Piezoelectric Energy Harvesting Device for Recharging Solid-State Batteries
Authors: Li Yuejuan , Cheng Marvin H. , Bakhoum Ezzat G.
Published: October 2013

Piezoelectric devices have been widely used as a means of transforming ambient vibrations into electrical energy that can be stored and used to power other devices. This type of power generation devices can provide a convenient alternative to traditional power sources used to operate certain types of sensors/actuators, MEMS devices, and microprocessor units. However, the amount of energy produced by these devices is in many cases far too small to directly power an electrical device. Therefore, much of the research into power harvesting has focused on methods of accumulating the energy until a sufficient amount is present, allowing the intended electronics to be powered.

Due to the tiny amount of harvestable power from a single device, it is critical to collect vibration energy efficiently. Many research groups have developed various methods to operate the harvesting devices at their resonant frequencies for maximal amount of energy. Different techniques of conversion circuits are also investigated for efficient transformation from mechanical vibration to electrical energy. However, efforts have not been made to the analysis of array configuration of energy harvesting elements. Poor combination of piezoelectric elements, such as phase difference, cannot guarantee the increasing amount of harvested energy. To realize a piezoelectric energy-harvesting device with higher volume energy density, the energy conversion efficiencies of different array configurations were investigated. In the present study, various combinations of piezoelectric elements were analyzed to achieve higher volume energy density. A charging circuit for solid-state batteries with planned energy harvesting strategy was also proposed. With the planned harvesting strategy, the required charging time can be estimated. Thus, the applicable applications can be clearly identified.

In this paper, optimal combination of piezoelectric cantilevers and different modes of charging methods were investigated. The results provide a means of choosing the piezoelectric device to be used and estimate the amount of time required to recharge a specific capacity solid-state battery.
Water Splitting by Aluminum Powder Obtained From Foil
Authors: Narayana Swamy Ashvin Kumar , Shafirovich Evgeny
Published: October 2013

The reaction of aluminum with water has the potential for on demand hydrogen generation. Conventional aluminum powders, however, react with water slowly due to a highly protective oxide layer on the particle surface. The present paper investigates the preparation of an activated aluminum powder from aluminum foil that is widely available as scrap and waste. The obtained results demonstrate that a highly reactive, fine aluminum powder can be obtained from aluminum foil by high-energy ball milling with sodium chloride. The obtained powder readily reacts with hot water, releasing hydrogen. The process includes the induction period, the middle stage where the reaction rate is the highest, and the final (saturation) stage. The effective activation energy of the reaction rate at the middle stage is in a good agreement with the literature data for Al-H2O reaction.
Microfluidic Characterization of Steam-Bitumen Interactions During Steam Assisted Gravity Drainage Operations
Authors: de Haas Thomas , Fadeai Hossein , Sinton David
Published: October 2013

In-situ recovery of heavy-oil and bitumen is used when reserves are too deep underground for conventional surface mining technologies. Steam assisted gravity drainage (SAGD) is process in which two horizontal wells, one vertically 5m above the other, are drilled into an oil-rich region. Steam is injected into the reservoir from the top well, and an oil steam-condensate mixture is pumped out the production well. The aim of this research is to physically model a section of oil sand in a SAGD operation. An array of micropillars fabricated into a glass microfluidic chip is used to represent the grains of sand. The chip was positioned vertically so that gravity plays a dominate role in drainage. Steam was pumped into the chip, reducing the viscosity of the oil and allowing oil and steam to flow under gravity to the outlet. The position of the steam front and the micro-scale interactions of the steam and oil were recorded over time.
Computational Analysis of Mixing in a Gas Turbine Combustor
Authors: Gupta Alka , Ibrahim Mohamed Saeed , Amano R. S.
Published: October 2013

This paper presents the computational analysis of the dilution process involved in gas turbines order to cool the combustion gases to the desired temperature before it enters the turbine. Here, it should be noted that in order to focus only on the dilution process, non-reacting flow conditions were simulated and the complete system was reduced to mixing of a primary (hot) stream and dilution (cold) stream of air. Four different schemes were investigated based on the layout of the dilution holes and use of a blunt body. A complete three dimensional analysis was carried out for each case in order to investigate its effectiveness to produce a more uniform temperature conditions at the exit of the combustor, so as to reduce the detrimental effect these temperature non-uniformities have on the turbine blades. For comparison of the proposed schemes, a parameter is defined in terms of the temperatures of the dilution and primary flow streams at the inlet and the exit plane, called the mixture fraction. Based on this parameter, it was found that the staggered dilution holes with the blunt body has the mixture fraction closest to the equilibrium mixture fraction (0.4), which implies that this scheme with the mixture fraction of 0.36, resulted in best mixing and produced the most uniform temperature distribution at the exit amongst the four proposed schemes.
Identifying Magnitudes and Locations of Multiple Loads on a Slender Beam Using Strain Gage Based Methods
Authors: Bednarz Edward T. , Zhu W. D. , Smith Scott A.
Published: October 2013

Unique strain gage based methods are developed to identify magnitudes and locations of multiple loads on a slender beam. Four uniaxial strain gages mounted to the bottom surface of the beam create a force transducer capable of identifying the magnitude and location of a load inside the weight area. For the case of multiple loads separated by two or more strain gage locations, uniaxial strain gages forming multiple force transducers can still identify the magnitudes and locations of all the loads. However, this creates an ill posed problem for loads separated by only one strain gage location. A new method has been developed using two shear gages mounted on the neutral axis of the beam, one on each side of a load, to identify the magnitude of the load in this case. A combination of two uniaxial strain gages and two shear gages, with one uniaxial strain gage and one shear gage at the same location on each side of a load, can be used to identify the location of the load. The strain gage based methods are experimentally validated on a prismatic beam with rest boundary conditions.
Simulation and Thermal Optimization of a Manifold Microchannel Flat Plate Heat Exchanger
Authors: Arie M. A. , Shooshtari A. H. , Dessiatoun S. V. , Ohadi M. M. , Al Hajri E.
Published: October 2013

This paper describes a multi-objective optimization of single-phase, laminar flow inside a single element of a manifold microchannel flat plate heat exchanger. Approximation assisted optimization was used for the optimization process. The process uses metamodeling in conjunction with Computational Fluid Dynamic (CFD) simulation as a method to minimize the number of function evaluations and thereby obtain substantial reductions in computational time. Two optimization objectives were considered: a) maximizing heat density rate per temperature difference Q/(VΔT) and minimizing pumping power density (P/V), and b) maximizing base heat transfer coefficient (h) and minimizing pumping power per base area (P/Abase). Water and air were used as working fluids to compare the optimum solutions of the two fluids with very distinctive thermo-physical properties. The study shows that both optimization objectives result in similar optimum points. The behaviors of the optimum solutions for water and air are also discussed in detail. Additionally, as a case study using the optimization results, it was demonstrated that for an array of microchannels with volume as low as 4,250 mm3 on one side, pumping power of 138 W and heat transfer rate of 56.7 kW can be achieved using water.