bluuebunny/crossref_metadata_2025 huggingface dataset:
Educating Maritime Engineers for a Globalised Industry: Bridging the Gap Between Industry and Universities
Authors: Andersen Ingrid M. V. , Nielsen Ulrik D.
Published: October 2013

In Denmark, the maritime engineering competences requested by the industry have changed in the past one to two decades. The typical naval architects do no longer find them selves working in the ship-building industry but rather in the industry of ship operators, consultancies, class societies, etc. This means that universities educating maritime engineers need to reflect the changes in the curricula for their maritime engineering students. Topics and issues regarding this matter have recently been addressed in a survey made in the Danish maritime industry. The survey concludes that the demand for maritime engineers in the industry is considerably larger than the output from the technical universities. Moreover, it sets forth a series of recommendations to the industry as well as to the universities to facilitate meeting the demand for maritime engineers in Denmark in the future. The recommendations are outlined together with work commenced at the Technical University of Denmark (DTU) to update the curricula for DTU’s maritime engineering students. Thus, DTU offers an education reflecting a large share of the recommendations in the curricula.
Design Creativity Education in an International Engineering Class
Authors: Iino Kenji , Nakao Masayuki
Published: October 2013

Conventional engineering education in Japan encourages students to widen knowledge built upon work and research by our predecessors. Such education has been effective in producing design improvement for higher efficiency and performance, however, not so in coming up with innovative ideas. Building products from within common knowledge cannot surpass the consumer expectation. We earlier reported about our collaboration between mechanical and industrial engineering educators in finding similarities and differences in the designers’ approaches in the two fields. Industrial designers, like mechanical designers, strive to meet the voice of customer (VOC) by dividing and conquering functional requirements. They also, unlike mechanical engineers, place the starting point of new designs outside the knowledge domain in efforts to define products that surpass consumer expectations. We call the starting point a discomforting seed. This paper reports our experience in educating foreign and native graduate students in mechanical engineering to have them recognize the discomforting seeds.
Magnetorheological Semi-Active Suspension to Improve High Speed Railway Vehicles Performance
Authors: Baiasu Dan , Ghita Gheorghe , Sebesan Ioan
Published: October 2013

The paper presents the opportunity of using a magneto-rheological damper to control the lateral oscillations of a passenger railway vehicle to increase its comfort and speed features. The lateral dynamics of the vehicle is simulated using a multibody model with 17 degrees of freedom considering the lateral, yawing and rolling oscillations. The equations describing the model are integrated by the authors using original software. The mathematical model considers the geometrical nonlinearities of the wheel-track contact. The nonlinear stability of the vehicle running on tangent tracks with irregularities is assessed and it is shown the influence of the construction parameters of the suspensions on the vehicle’s performance. A magneto-rheological device with sequential damping based on balance logic control strategy is introduced in the secondary suspension of the vehicle to reduce the lateral accelerations generated by the track’s irregularities. The system’s response in terms of accelerations is compared for both passive and semi-active cases. It is shown that the magneto-rheological semi-active suspension improves the safety and the comfort of the railway vehicle.
Thermal Rectification in Bulk Materials Using Rough Contacts: A Thermal Diode
Authors: Sayer Robert A.
Published: October 2013

Thermal rectification occurs when a device permits heat to flow preferentially in one direction direction while restricting it in the opposite direction. Thermal rectification can occur whenever an asymmetry is present in a device, and has been demonstrated to arise in bulk materials that have asymmetric geometry, in the contact of two materials with different thermal properties and in nanomaterials. Herein, a thermal diode that utilizes thermal expansion to directionally control interfacial conductance between two contacting surfaces is presented. Essentially, the device consists of two thermal reservoirs contacting a beam with one rough and one smooth end. When the temperature of reservoir in contact with the smooth surface is raised, a similar temperature rise will occur in the beam, causing it to expand, thus increasing the contact pressure at the rough interface and reducing the interfacial contact resistance. However, if the temperature of the reservoir in contact with the rough interface is raised, the large contact resistance will prevent a similar temperature rise in the beam. As a result, the contact pressure will be marginally affected and the contact resistance will not change appreciably. Owing to the decreased contact resistance of the first scenario compared to the second, thermal rectification occurs. A parametric analysis is used to determine optimal device parameters including surface roughness, contact pressure and device length. Modeling predicts rectification factors greater than 2 are possible at thermal biases as small as 3 K.
Redesign of a Test Environment for an Elastic Mechanism for Usage as Pressure Sensor Element
Authors: Ottnad Thomas , Irlinger Franz , Lueth Tim C.
Published: October 2013

When dealing with plastics producing techniques such as injection molding and extrusion control of pressure is a decisive parameter influencing the quality and reproducibility of plastics products. Different types of pressure sensors are commonly used which most often transform mechanical deformation into electrical signals and these in turn are converted into the value of pressure. In some cases separate pressure chambers might be necessary, often the pressure range is limited, and usage of electrical components lead to constraints concerning temperature range. This in turn means extensive effort for installation and insulation of the pressure sensors for example when you want to control the pressure at any desired area of the injection system.

This work is based on an approach of using a flexible element and determining the pressure solely by its deformation. This eliminates thermal insulation and electromagnetic shielding. But concurrently this demands some knowledge concerning the mechanical behavior of the flexible element.

To determine the mechanical behavior of the flexible element especially its stiffness different approaches have been taken into account. First one is to regard the flexible element as Kirchhoff plate. This analytic approach implies a constant bending stiffness which means a linear dependency between working pressure and resulting deflection. This could be confirmed evaluating measurement data that has been taken using a test rig specially designed for that task. In the test rig as substitution of the pressure a variable but defined load can be applied.

When carrying out some measurements with one certain flexible element the influence of assembling and disassembling the test rig was obvious. Only when not changing the assembled test rig measurements have been reproducible. Main reason was the radial variance of applied load and the center of the flexible element.

In order to solve that a test rig was redesigned including a centering device to guarantee load transmission happening always at the same point. Additionally influence of certain linkages in the test rig has been investigated. Combination of both leads to a more reliable and better test rig with higher reproducibility.
A Numerical Study on Taylor Flow Heat Transfer in Square Microchannels Under Constant Wall Temperature Boundary Condition
Authors: Talimi V. , Muzychka Y. S. , Kocabiyik S.
Published: October 2013

Heat transfer in Taylor flows or slug flows has been examined exclusively by researchers. Noncircular microchannels have not been widely considered in the literature. There is a large gap in research since noncircular microchannels are common structures in microcooling processes. Square and rectangular microchannels are the most important examples. In the present study the heat transfer process in slug flows in square microchannels has been investigated numerically under constant wall temperature boundary condition. The local heat flux for the moving slugs has been converted to total microchannel heat flux using the integration methods suggested recently by the authors. This leads to microchannel wall average heat flux which is the parameter of interest in heat sink problems. Finally, effects of liquid film around bubbles on heat transfer process have been discussed.
Characterization of Solid Oxide Fuel Cell Materials Based on Microstructural Skeletonization
Authors: Nakajo Arata , Nelson George J. , DeGostin Matthew , Myles Timothy D. , Peracchio Aldo A. , Chiu Wilson K. S.
Published: October 2013

The understanding of the relationship between the microstructure of materials for energy applications and their transport and electrochemical properties is needed to optimize their long-term performance. The improvements of 3D imaging techniques such as x-ray nanotomography allow access to geometrical and elemental information with ever increasing accuracy and details. These advances warrant determining new relevant metrics for material characterization, the calculation of which will require adaptations of the methodologies for parameter extraction.

This study presents the development of a tool for the characterization of porous, heterogenous materials that provides coherent geometrical and topological information. We illustrate the relevance of the methodology by discussing the differences between geometrical concepts for estimating phase size distributions of real heterogeneous materials investigated using x-ray nanotomography and how research between different scales and physics can be bridged. This is achieved by providing, on the one hand, inputs to classical continuum models and, on the other hand, by synergetic combination with discrete element methods.
Numerical Modeling of Damping Characteristics in a Torsional Micro-Resonator
Authors: Acharya Tathagata , Martin Michael J.
Published: October 2013

The dynamic behavior of torsional micro-resonators with dimensions, 100 μm × 20 μm, 100 μm × 10 μm, 100 μm × 5 μm, and 100 μm × 2.5 μm are modeled under continuum conditions in ambient air and different liquids and at angular frequencies of 1000 Hz and 5000 Hz respectively. The dynamic response in terms of energy lost per cycle, torsional amplitude and the phase shift are calculated and non-dimensionalized suitably. Finally efforts have been made to establish a relationship between the parameters of interest and the aspect ratio.
Eddy Current Measurement for Characterizing Soft Tissues
Authors: Sequin Emily K. , West Joseph , Subramaniam Vish V.
Published: October 2013

Real-time and non-invasive imaging of tissues and detection of diseases on millimeter to centimeter scales can be useful in some clinical applications such as determination of margins during cancer surgery and image-guided pathology. In this paper, we describe an eddy current measurement method for characterizing soft tissues. The device consists of a pair of concentrically wound coils, a primary coil excited by a low frequency (<100 kHz) sinusoidal voltage, inducing a voltage and current in the secondary detecting coil. When a conducting sample is present, eddy currents develop in the sample and alter the induced voltage and phase on the detecting coil. The output voltage and phase of the detecting coil are then monitored using lock-in amplification.

Experimental measurements on porcine muscle tissue examine the effects of varying tissue macrostructure and conductivity on the eddy current detector. Three sets of experiments are presented. First, muscle samples cut into different sized grids simulating the restriction of eddy current domains show that morphological structure has a strong influence on the detector signal. Second, eddy current measurements made on porcine muscle samples at varying degrees of dehydration show that as conductivity decreases, eddy current signals also decrease. Finally, measurements on porcine muscle samples soaked overnight in deionized water complement the dehydration experiments and confirm detector voltage and phase changes decrease with decreasing conductivity.
Drilling Riser System Design in Deepwater Environment
Authors: Woo Nam-Sub , Kim Young-Ju , Kwon Jae-Ki , Kim Sang-Shik , Yun Sang-Woong , Kim Byung-Woo
Published: October 2013

The development of deepwater oil and gas reserves constantly faces the challenge to reduce costs of all components and activities. A drilling riser is a conduit that provides a temporary extension of a subsea oil well to a surface drilling facility. With an increase in drilling operations in harsh environments, drilling riser requirements and limits have become more onerous due to uncertainties involved in response prediction and prolonged drilling programs. A high level of understanding is required of the response of the system to various conditions, and the design issues that govern the system. This paper presents an overview of the engineering challenges faced in designing drilling riser system for drill ship in water depths of 10,000 ft. Also, Static and dynamic analysis of drilling riser system have been carried out for the development of drilling riser joint.
An Experimental Study on the Cuttings Transport in Inclined Slim-Hole Annulus
Authors: Kim Y. J. , Han S. M. , Woo N. S.
Published: October 2013

In directional drilling, it is difficult to adjust and control the cuttings, so it is very important to evaluate the flow characteristics of a drilling flow field. In this study, solid-liquid two-phase flow experiments have been carried out in non-Newtonian fluids for hole inclinations from vertical to 75 degrees, flow velocities from 0.33 m/s to 0.66 m/s, particle concentration from 4 to 16 %, and pipe rotations from 0 to 400 rpm. Pressure drop within the test section, and particle volume fraction are measured for the above test conditions. These quantities were influenced by particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. Moreover, empirical correlations were developed for estimating friction coefficient and particle volume fraction inside annulus. The new correlations generated in this study are believed to be very practical and handy when they are used in the field. Therefore, this study can provide meaningful data for directional drillings.
Laser Transmission Welding of Transparent Thermoplastics Microfluidic Devices
Authors: Ying Ming , Bi Guijun , Wei Jun , Ramachandra Paramasivam S/O
Published: October 2013

Laser transmission welding (LTW) is a widely employed joining technique for thermoplastics microfluidic devices bonding with its distinctive advantages, such as non-contact and no relative part movement. One basic requirement for successful laser transmission welding is that one of the plastics needs to be optically transparent for the wavelength of the laser radiation with the other being laser absorbing. The current study aims to develop laser transmission welding process for the bonding of two transparent polycarbonate (PC) microfluidic substrates with the channel size of 50μm. Transparent laser absorbent material is applied on the one substrate surface to make a laser absorbing interface. A fully coupled thermal-displacement finite element (FE) model is established to simulate the performances of the welding. The process window, including laser power, scanning speed and clamping force, is derived with the modeling method. The welded channel quality, in terms of collapsed height, clogging size, and bonding strength, can meet the requirements of microfluidic device applications.
Assessment of Single and Two-Phase Models for Nanofluid Flow at the Entrance Region of a Uniformly Heated Tube
Authors: Goktepe Sinan , Atalik Kunt , Erturk Hakan
Published: October 2013

Hydrodynamic and thermal characteristics of Al2O3 – water nanofluid flow at entry region of a uniformly heated pipe are studied applying finite control volume method (FCV). Single phase and Eulerian-Eulerian two-phase models were used in modelling of nanofluid flow and heat transfer. The two methods are evaluated by comparing predicted convective heat transfer coefficients and friction factor with experimental results from literature. Solutions with two different velocity pressure coupling algorithms, Full Multiphase Coupled, and Phase Coupled Semi-Implicit Method for Pressure Linked Equations are also compared in terms of accuracy and computational cost. Two-phase model predicts convective heat transfer coefficient and friction factor more accurately at the entry region. Moreover, computational cost can be reduced by implementing Full Multiphase Coupled scheme.
An Innovative Technology Development for Building Humidification and Energy Efficiency
Authors: Wang Dexin , Bao Ainan , Liss William
Published: October 2013

Currently, the most widely used residential humidification technologies are forced air furnace mounted bypass wetted media, spray mist, and steam humidifiers. They all use city water as a water source and require furnace heat or electricity to evaporate the water. Mineral deposition, white dust, and microbial growth problems are associated with these humidifiers. For commercial building humidification, de-mineralized water is typically used for humidification equipment like steam heat exchangers, fogging system, electric, and ultrasonic humidifiers. Therefore, in addition to the energy consumption for the water evaporation, energy is also needed to produce the high quality de-mineralized water.

An innovative technology called Transport Membrane Humidifier (TMH), has been developed by the authors to humidify home air without external water and energy consumption, while simultaneously recovering waste heat from the home furnace flue gas to enhance the furnace efficiency. The TMH technology is based on our previous extensive study on nanoporous membrane water vapor separation from combustion flue gas, and a design for residential home humidification application was first developed. It has been proved by both laboratory prototype testing for long term performance, and by two occupied single family home demonstrations for two heating seasons. The technology can provide whole house humidification without any external water consumption, and at the same time boost the furnace efficiency. Compared with conventional furnace mounted humidifiers, the TMH does not need additional furnace fuel for the water evaporation, no white dust in the home, no microbial growth since there is no standing water involved. Therefore, it is an innovative technology that can provide energy saving, water saving and healthy building humidification.
Thermoeconomic Optimization of Heat Recovery Steam Generators: A Modular Approach to Define the Layout of Heat Exchange Sections
Authors: Carapellucci Roberto , Giordano Lorena
Published: October 2013

One of the most efficient energy conversion systems in state-of-the-art electricity generation technology are combined cycle gas turbines. As is well known, the heat recovery steam generator (HRSG) configuration has a major impact on the overall performance of a combined-cycle power plant. Thus providing a tool for optimizing design parameters and layout of a HRSG is an important issue.

The present study focuses on HRSG optimization, employing an exergoeconomic methodology. This is based on the minimization of the total cost of HRSG, including capital costs of heat exchanger sections and operating costs related to exergy destruction. The decision variables of the proposed optimization method are the HRSG operating parameters, as well as the layout of the heat exchanger sections.

To predict behavior and performance, the HRSG is regarded as a modular structure, i.e. as a set of elementary components, interacting through nodes affected by mass and energy flows. The modular approach proposed makes the optimization methodology particularly flexible, as the configuration of the HRSG can be identified defining an “interaction matrix” to characterize the mode of interaction of the elementary components.
Active Flow Control With an Oscillating Backward Facing Step in a Shallow Open Channel
Authors: Cadirci Sertac , Gunes Hasan
Published: October 2013

An oscillatory, zero-net-mass flux actuator system, Jet and Vortex Actuator (JaVA), is implemented on the step wall of a backward facing step. JaVA can energize the boundary layer by creating jets or vortices thus it may delay flow separation when used properly. The main part of JaVA is a rectangular cavity with a moving actuator plate. The actuator plate is mounted asymmetrically inside the cavity of the JaVA box, such that there are one narrow and one wide gap between the plate and the box. The main governing parameters are the actuator plate’s width (b), the amplitude (a) and the operating frequency (f). The main target of the control with active jets on the step wall is to influence directly the main recirculation zone, thus as the actuator plate or the step’s vertical wall moves periodically in horizontal direction, a jet emerges into the recirculation zone. Non-dimensional numbers such as the scaled amplitude (Sa = 2πa/b) and the jet Reynolds number (ReJ = 4abf/ν) as well as the cross flow parameter characterize the JaVA-induced flow types and the effects on the recirculation zone. One period consists of one blowing and one suction phase into the recirculation zone. Boundary layer profiles extracted from time-averaged flow fields of the not actuated (f = 0) and actuated cases at various operating frequencies indicate the effect of active flow control. The interaction between JaVA-induced flow regimes and the boundary layer is investigated numerically in an open channel with a BFS. The computational domain consists of a moving zone along the channel and the motion of the actuator plate is generated by a moving grid imposing appropriate boundary conditions with User-Defined-Functions and the calculations are carried out by a commercial finite-volume-based unsteady, laminar, incompressible Navier-Stokes solver. Numerical simulations and comparisons reveal the JaVA-boundary layer interaction for various governing parameters. Reynolds numbers based on the step height for the shallow open channel flow are Reh = 225 and 450. The proposed control method based on suction and blowing with an oscillating vertical step seems to be effective in shortening the recirculation zone length and delaying the flow separation downstream of the backward facing step.
Ballistic Helmets: Their Design, Materials, and Performance Against Traumatic Brain Injury
Authors: Kulkarni S. G. , Gao X.-L. , David N. V. , Horner S. E. , Zheng J. Q.
Published: October 2013

Protecting a soldier’s head from injury is critical to function and survivability. Traditionally, combat helmets have been utilized to provide protection against shrapnel and ballistic threats, which have reduced head injuries and fatalities. However, home-made bombs or improvised explosive devices (IEDs) have been increasingly used in theatre of operations since the Iraq and Afghanistan conflicts. Traumatic brain injury (TBI), particularly blast-induced TBI, which is typically not accompanied by external body injuries, is becoming increasingly prevalent among injured soldiers. The response of personal protective equipment, especially combat helmets, to blast events is relatively unknown. There is an urgent need to develop head protection systems with blast protection/ mitigation capabilities in addition to ballistic protection. Modern military operations, ammunitions, and technology driven war tactics require a lightweight headgear that integrates protection mechanisms (against ballistics, blasts, heat, and noise), sensors, night vision devices, and laser range finders into a single system. The current paper provides a comparative study on the design, materials, ballistic and blast performance of the combat helmets used by the U.S. Army based on a comprehensive and critical review of existing studies. Mechanisms of ballistic energy absorption, effects of helmet curvatures on ballistic performance, and performance measures of helmets are discussed. Properties of current helmet materials (including Kevlar® K29 and K129 fibers, and thermoset resins) and future candidate materials for helmets (such as nano-composites, thermoplastic polymers, and carbon fibers) are elaborated. Also, experimental and computational studies on blast-induced TBI are examined, and constitutive models developed for brain tissues are reviewed. Finally, the effectiveness of current combat helmets against TBI is analyzed along with possible avenues for future research.
Fatigue Life Prediction Under Biaxial FALSTAFF Loading Using Statistical Volume Element Based Multiscale Modeling
Authors: Zhang Jinjun , Liu Kuang , Chattopadhyay Aditi
Published: October 2013

This article presents the fatigue life prediction in a cruciform specimen of 2024-T351 aluminum alloy subjected to biaxial FALSTAFF loading. An energy- and slip-based multiscale damage criterion is developed to capture the fatigue crack formation in crystalline metallic materials. In these materials, there are two stages in crack initiation: nucleation of micro cracks and coalescence of micro cracks into major cracks. In the first stage, micro cracks generate from intermetallic particles and extend into surrounding grains. For the FCC crystalline structure, fatigue damage increments in four dependent slip planes are calculated and accumulated to measure micro crack. In the second stage, the micro cracks grow and coalesce into major cracks. Subsequently, a meso-statistical volume element model is developed to represent the microstructure of the material. Finally, a root mean square method is introduced to take into account FALSTAFF loading. Using the root mean square (RMS) method, the loading history for tests is analyzed to determine the RMS maximum and minimum stresses. The multiscale damage criterion, statistical volume element and RMS method were validated using previously conducted fatigue tests on cruciform samples. The fatigue life and crack direction predicted using the developed model correlate well with the experiments.
Prediction of Fracture Toughness via Microstructure-Level Simulations
Authors: Li Yan , Zhou Min
Published: October 2013

Microstructural design is an important approach for enhancing material properties such as fracture toughness at the macroscopic scale. Tasks in this regard require systematic quantification of both microstructure and material response. We report the development of a multi-scale computational framework based on the cohesive finite element method (CFEM) for predicting fracture toughness of materials as a function of microstructure. The approach uses the J-integral to calculate the initiation/propagation fracture toughness, allowing explicit representation of realistic microstructures and fundamental fracture mechanisms. Calculations carried out concern both brittle and ductile materials and focus on the effects of constitute behavior, phase morphology, phase distribution, and size scale on fracture toughness. Based on the CFEM results, a semi-empirical model is developed to provide a quantitative relation between the propagation toughness and statistical measures of microstructure, fracture mechanisms, and constituent and interfacial properties. Both the CFEM calculations and model predictions show that microstructure and constituent properties can significantly influence the fracture behavior and combine to determine the overall fracture toughness through the activation of different fracture mechanisms. In particular, a combination of fine microstructure size scale, rounded reinforcement morphology, and appropriately balanced bonding strength and compliance can best promote desirable crack-reinforcement interactions and lead to enhanced propagation fracture toughness. The CFEM framework, phenomenological model and the relations obtained can be useful tools for the design of failure-resistant materials.
Solution-Based Fabrication of P-Channel and N-Channel Thin-Film Transistors Using Random and Aligned Carbon Nanotube Networks
Authors: Duan Yan , Juhala Jason L. , Griffith Benjamin W. , Uwizeye Vianney J. , Xue Wei
Published: October 2013

Since discovered in the early 1990s, single-walled carbon nanotubes (SWNTs) have attracted significant attention for many research fields. In the long term, micro- and nano-electronics are considered to be one of the most valuable applications of SWNTs. The development of the next generation devices involves the mass fabrication and integration of SWNT field-effect transistors (FETs) to form logic gates, which are the basic units of integrated circuits (ICs). To create logic gates, both p- and n-type SWNT FETs are needed. However, the SWNT FETs are typically p-type in air without special treatment, with holes as the majority charge carriers in SWNTs. Here in this paper, we investigate the p-channel and n-channel SWNT FETs using two solution-based fabrication processes. One method is to use layer-by-layer self-assembly to create SWNT random networks and the other is based on dielectrophoresis-aligned SWNTs. A low-cost, easy-to-control method is introduced to convert p-type FETs to n-type. By coating a polyethylenimine (PEI) layer on the surface, the transistor demonstrates the typical n-channel characteristics. The resulting devices are air-stable outside a vacuum or an inert environment. The combination of the simple fabrication methods, easy conversion of the devices, and satisfactory device performance can promote further development of nanotube-based electronics.
Impact and Quasi-Static Mechanical Properties of a Carbon Fiber Reinforced Carbon Nanotube/Epoxy
Authors: Tehrani Mehran , Boroujeni Ayoub Y. , Hartman Timothy B. , Haugh Thomas P. , Case Scott W. , Al-Haik Marwan
Published: October 2013

Carbon fiber reinforced plastics (CFRPs) possess superior in-plane mechanical properties and are widely used in structural applications. Altering the interphase of CFRPs could alleviate the shortcomings of their out-of-plane performance. In this work, the effects of adding multi-walled carbon nanotubes (MWCNTs) to the epoxy matrix of a CFRP are investigated. Two sets of CFRPs with matrices comprising MWCNTs/epoxy and neat epoxy, respectively, were fabricated. The tensile properties of the two systems, namely the stiffness, the ultimate strength, and the strain to failure were evaluated. The results of the tension tests showed slight changes on the on-axis (along the fiber) tensile modulus and strength of the carbon fiber reinforced epoxy/MWCNT compared to composites with no MWCNTs. The addition of MWCNTs to the matrix moderately increased the strain to failure of the composite. Energy absorption capabilities for the two sets of composites under an intermediate impact velocity (100 m.s−1) test were measured. The energy dissipation capacity of the CFRPs incorporating MWCNTs was higher by 17% compared to the reference CFRPs.
Non-Newtonian Behavior Computer Aided Simulation of Metal Matrix Aluminum Alloy
Authors: Wang Yaou , Miller Allen R. , Kabiri-Bamoradian K.
Published: October 2013

This work is a case study of non-Newtonian behavior of metal matrix composite materials used in the metal casting process. The casting alloys considered are composed of an aluminum alloy matrix reinforced with a relative high fraction of ceramic particles. The composite material exhibits non-Newtonian behavior with viscosity dependent on shear rate, volume fraction of suspended solid particles, phase change and solid fraction of primary metal during solidification. Computer aided simulation method, computational fluid dynamics (CFD), is used in this work to analyze the effect of non-Newtonian behavior on the flow pattern of the composite material during casting mold filling process. The result of this work is expected to describe an approach suitable for die design analysis and operation parameters optimization in the metal matrix alloy casting process.
Active Conical and Planetary Gearing System for Wind Turbines
Authors: Azzouz M. Salim , Fagbe Anjolajesu , Evetts Zachary , Rosales Ethan
Published: October 2013

The purpose of this research project is to explore the possibility of harvesting the energy of the wind by taking advantage of higher wind speeds. Two active gearbox systems allowing a variable speed at the input shaft and delivering a constant speed at the output shaft are currently being built and tested. The first system consists of an assembly of spur, planetary, and ring gears run and controlled by electrical motors. The second system consists of an assembly of a conical shaft, a wheel, and a set of centrifugal masses. The two gearing systems can act separately as a continuously variable transmission (CVT) between the wind turbine hub and the electricity generator which requires an entry speed corresponding to a frequency of 60 Hz. The two gearing systems are designed using the SolidWorks CAD software for modeling and simulation, and the gearing design theory is used to dimension the required spur, planetary and ring gears for the first proposed system. Betz’s law associated with appropriate and realistic wind turbine efficiency is used to estimate the wind power transferred to the turbine hub. The law is also used to determine the hub angular speed as a function of the wind speed. The kinematic gearing theory is used to establish the different gearing ratios of the planetary system, and the kinematic relationships between the system stages. The forces and torques acting on the first and the second systems are computed using the equilibrium equations. The speed ratios are calculated for the first and second system using the kinematic theory. Ideally, the electrical power consumed by the regulating motor for the first system is minimal so that a maximum percentage of the generated electrical power is supplied to the electricity grid. For the second system the totality of the harvested power is transmitted through the conical/wheel system. For the planetary system, when the wind speed deviates from a certain optimum value, the electrical controls activate a regulating motor to guarantee that the generator input speed remains constant. Currently, a prototype of a more robust planetary gearing system than a previously made one is under construction while a newly constructed conical system is under experimental testing. Running speeds, torques, power transfer and distribution for the two systems will be measured. The generated electrical power is measured using different load resistances and compared to the electrical power consumed by the regulating motor for the planetary system. The torques are measured using a prony brake system while the angular speeds are measured using tachometers. It is expected that the power consumed by the regulating motor for the gearing system will remain a small percentage of the power supplied to the grid for various hub input speeds.
Synthesis and Characterization of Nanowire-Graphene Aerogel for Energy Storage Devices
Authors: Shuvo Mohammad Arif Ishtiaque , Khan Md. Ashiqur Rahaman , Mendoza Miguel , Garcia Matthew , Lin Yirong
Published: October 2013

The study of graphene has become one of the most exhilarating topics in both academia and industry for being highly promising in various applications. Because of its excellent mechanical, electrical, thermal and nontoxic properties, graphene has shown promising application in energy storage devices such as lithium-ion-battery (LIB), super capacitor and solar cell. In lithium ion battery, graphite is the most commonly used material as anode. However, due to the limited specific surface area of graphite materials, the diffusion of the Li ions in the anode graphite is relatively slow, leading to limited energy storage density. In order to further increase the capacity, nano-structured materials have been extensively studied due to its potential in reducing Li-ion diffusion pathway. To date, one of the most promising approaches to improve the Li-ion diffusion rate is to introduce hybrid nanostructured electrodes that connect the nonconductive high surface area nanowire with nanostructured carbon materials. While there have been several research efforts investigated to fabricate nanowire-graphene hybrids, all the them were focused on randomly distributed nanostructures thus the LIB performance enhancement was limited. Therefore, this paper will introduce a novel hybrid structure with vertically aligned nanowire on graphene aerogel aiming to further increase the performance of LIB. The aligned nanowire array provides a higher specific surface area and could lead to high electrodeelectrolyte contact area and fast lithium ion diffusion rate. While the graphene aerogel structure is electrically conductive and mechanically robust, as well as has low specific density. The developed nanowire/graphene hybrid structure could have the potential to enhance the specific capacity and charge-discharge rate. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) measurements were used for the initial characterization of this nanowire/graphene aerogel hybrid material system.
An Analytical Solution of the Generalized Phase-Lagging Equation for Ultra-Fast Heat Transfer in One-Dimensional Semi-Infinite Domain
Authors: Kulish Vladimir , Poletkin Kirill V.
Published: October 2013

The paper presents an integral solution of the generalized one-dimensional phase-lagging heat equation with the convective term. The solution of the problem has been achieved by the use of a novel technique that involves generalized derivatives (in particular, derivatives of non-integer orders). Confluent hypergeometric functions, known as Whittaker’s functions, appear in the course of the solution procedure, upon applying the Laplace transform to the original transport equation. The analytical solution of the problem is written in the integral form and provides a relationship between the local values of the temperature and heat flux. The solution is valid everywhere within the domain, including the domain boundary.
Design of the Pitch Cones of Noncircular Bevel Gears
Authors: Shi Kan , Xia Jiqiang , Wang Chunjie , Geng Chunming
Published: October 2013

A design method for the pitch cones of noncircular bevel gears is proposed. In particular, the accurate formulation of the pitch cones of the driving gear and the driven gear are obtained for any number and combination of lobes and in any configuration during their pure-rolling motion. This design method is implemented in Pro/E and several significant examples are included.
Influence of Material Damping on In-Plane Modal Parameters for Rotating Disks
Authors: Hamidzadeh Hamid R. , Sarfaraz Ehsan
Published: October 2013

The linear in-plane free vibration of a thin, homogeneous, viscoelastic, rotating annular disk is investigated. In the development of an analytical solution, two dimensional elastodynamic theory is employed and the viscoelastic material for the medium is allowed by assuming complex elastic moduli. The general governing equations of motion are derived by implementing plane stress theory. Natural frequencies are computed for several modes at specific radius ratios with fixed-free boundary conditions and modal loss factors for different damping ratios are determined. The computed results were compared to previously established results. It was observed that the effects of rotational speed and hysteretic damping ratio on natural frequency and elastic stability of the rotating disks were related to the mode of vibration and type of circumferential wave occurring.
Factors Affecting Torque Loss in Synchronous Belt Drives Under No Transmitted Torque
Authors: Ueda Hiroyuki , Kagotani Masanori
Published: October 2013

Synchronous belts generally exhibit higher transmission efficiency than frictional transmission belts because of their meshing transmission. However, synchronous belts are subject to torque loss due to flexural rigidity when the belt is wound on a pulley. Torque loss also occurs due to incomplete meshing between the belt and pulley teeth at the beginning and end of meshing. If these torque losses can be reduced, synchronous belts can achieve higher transmission efficiency. In the present study, the torque loss in synchronous belt drives under the no transmitted torque and a pulley speed ratio of 1:1 is experimentally investigated with regard to installation tension, belt width, thickness of the belt back face, pitch difference, number of pulley teeth, and temperature of the atmosphere surrounding the belt. It is found that the torque loss in synchronous belt drives increases with increasing installation tension, belt back face thickness, belt width, and pitch length, and with decreasing pulley teeth number and temperature of the atmosphere surrounding the belt.
The TLCD Passive Control: Numerical Investigations vs. Experimental Results
Authors: Di Matteo Alberto , Lo Iacono Francesco , Navarra Giacomo , Pirrotta Antonina
Published: October 2013

Very recently the tuned liquid column damper (TLCD) is receiving an increasing interest from researchers concerned with vibration control, to be considered an alternative device with respect to the tuned mass damper (TMD), since the former has low cost, easy adjustment, flexible installation.

However, in recent studies the authors [1] have pointed out that for TMD the analytical formulation provides results that are in good agreement with the experimental ones, while for TLCD it has been deducted that the analytical formulation needs further investigation.

In fact using the classical formulation of the problem, numerical results are very different from the experimental results obtained by the authors using the facilities at the experimental dynamic laboratory of University of Palermo.

In particular it has been shown that the total liquid length should be corrected in an effective one, but in a different way from what has been done in literature, where only the variation of section of the vessel has been taken into account. On the other hand, from experimental investigations it is seen that the liquid moves more in the central area of the tube and less in the area in contact with the side walls. This aspect plays a fundamental role for capturing the real performance of TLCD. In fact, being the TLCD a special type of auxiliary damping device which relies on the inertia of liquid column in a U-tube to counteract the forces acting on the structure, then it is necessary to identify the effective moving liquid mass. To aim at this, in this paper the authors differentiate the total liquid mass into a liquid dead mass and a liquid dynamic mass, then introducing these values into a properly modified mathematical formulation numerical results match the experimental ones for all tests.
Numerical Simulation of Hydrogen Desorption in Metal-Hydride Reactor
Authors: Han Fei , Dai Weizhong
Published: October 2013

Studying hydrogen desorption in metal-hydrogen reactors is important for the usage and commercialization of hydrogen energy. In this article, we consider a cylindrical metal-H2 reactor and present a finite-difference scheme for simulating the heat and mass transfer between LaNi5 and H2 during the desorption of hydrogen in the reactor, by using a two-dimensional (2D) mathematical model. Numerical results including temperature, gas and solid densities are obtained.
Analytical Solutions of Period-1 Motions in a Periodically Forced van der Pol Oscillator
Authors: Luo Albert C. J. , Lakeh Arash Baghaei
Published: October 2013

In this paper, the approximate analytical solutions of period-1 motion in the periodically forced van der Pol oscillator are obtained by the generalized harmonic balanced method. The stability and bifurcation analysis of the period-1 solutions is completed through the eigenvalue analysis, and numerical illustrations of periodic-1 solutions are given to verify the approximate motion. This investigation provides more accurate solutions of period-1 motions in the van der pol oscillator for a better and comprehensive understanding of motions in such an oscillator.
On Flexural Vibrations of Shear Deformable Laminated Beams
Authors: Lenci Stefano , Clementi Francesco
Published: October 2013

The natural frequencies of a two-layer beam with an elastic interface are investigated. Each beam is modeled by the Timoshenko kinematics, and the interface coupling is linear in both normal and tangential directions. Attention is focused on the shear deformation, axial and rotational inertia, and interface normal stiffness. The dependence of the natural frequencies on these mechanical characteristics is investigated by solving the associated eigenvalue problem. The convergence of the solution toward that of a simplified problem obtained by neglecting axial and rotational inertia, shear deformations and by considering interface perfect adherence in the normal direction, is studied. Various boundary conditions are investigated to extend the generality of the proposed results.
Geometrical Determinations of Photon-Beam Limit Angle (LA) Related to Maximum Pencil-Beam Divergence Angle for Standard Radiotherapy Wedges
Authors: Casesnoves F.
Published: October 2013

Wedge filters constitute a useful type of Beam Modification Devices (BME) in Radiation Therapy. Its use is routinary in both Forward and Inverse Treatment Planning Optimization (ITPO). In previous contributions we presented the exact/approximated path of a Pencil Photon-Beam (AAA Model, Anisothropic Analytic Algorithm), through standard manufacturing alloy wedges. It was found a so-defined Limit-Angle (LA), beyond of which the outpoint of the beam is located improperly at the lateral side of the wedge. LA exists because of the photon-beam physical divergence phenomenon. In this paper we carry out the Geometrical and Analytical determination of the LA in function of the beam divergence angle, collimator output distance, and the size parameters of the wedge filter. Two methods are used, Geometrical and Analytical. A series of Mathematical Formulations for LAs, is shown with basic approximations according to the industrial manufacturing wedge standards. Formulation is verified with Optimization Mathematical Methods.
Pseudo-Color Coded Optical System Based on the Spatial Light Modulator and Charge-Coupled Device
Authors: Zhao S. N. , Chang H. , Wei J. , Wei Z.
Published: October 2013

A new pseudo-color coded optical system based on the liquid crystal spatial light modulator (LC-SLM) and a digital camera (CCD) is proposed. The SLM is used to replace the holographic grating with gray-scale image information, a gray-scale image in real-time modulation methods is proposed by synthesizing phase hologram and Ronchi grating, combined with the 4f coherent optical processing system and spatial filtering. For the high resolution gray image processed with existing digital pseudo-color method, the color sensitivity is low, algorithm is very complex. For traditional optical pseudo-color method, the gray scale image needs chemical pretreatment. The process is complex and time-consuming, and the real-time modulation could not be achieved. Our new method has enhanced the flexibility and adaptability of the optical pseudo-color, and give full play to the high sensitivity, high-capacity, rich colors and other features of the optical processing mode. At the same time, it overcomes the disadvantages of pure optical system which could not perform real-time processing. Therefore, it can be widely used in the field of remote sensing, biomedical, environmental monitoring, public security and criminal investigation, etc.