bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Forces in Deep Hole Bone Drilling
Authors: Lee JuEun , Chu Serena , Chavez Craig L.
Published: January 2019

Deep hole drilling is required to install prosthetic devices in surgical implantation. Compared to the common bone drilling processes, deep hole bone drilling is performed with a larger hole depth (i.e., up to a depth of approximately 35 mm in cochlear implantation) using a high ratio of the length to diameter of the drill bit. For successful outcomes from this process, forces must be controlled adequately to avoid other complications such as drill-bit breakage or thermal necrosis. This study investigates the thrust force and torque generated in bone drilling process of up to 36 mm drilling depth. Drilling tests were performed on bovine cortical bone using 2.5 mm diameter twist drill bit with a spindle speed of 3000 rpm, and feed rates of 0.05, 0.075, and 0.1 mm/rev. Two distinct states in both the thrust force and torque data were observed for all conditions, which are called normal and abnormal states in this study. At an early stage of the drilling process, the force signals showed the traditional trend, reaching a constant value once the tip of the drill bit was fully engaged in bone cutting up to a certain depth. After that, both thrust force and torque kept increasing rapidly until the final drilling depth. This study also observed that the chip morphology varies with increasing drilling depth, showing fragmented chips at the normal state and powdery chips at the abnormal state. Chip clogging and increased frictional force between chips, tool, and hole wall with larger drilling depth may cause the abrupt increase in forces and variation in chip morphology.
The Impact of Adding a Labyrinth Surface to an Optimal Helical Seal Design
Authors: Paudel Wisher , Watson Cori , Wood Houston G.
Published: January 2019

Non-contacting annular seals are used in rotating machinery to reduce the flow of working fluid across a pressure differential. Helical and labyrinth grooved seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump and at the balance drum. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves on either or both the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high-pressure region. Previous work has shown that mixed helical-labyrinth seals with labyrinth grooves on stator and helical grooves on rotor or labyrinth grooves on rotor and helical grooves on stator have an approximately 45% lower leakage than an optimized helical groove seal with grooves just on the stator in a high pressure application. The primary objective of this study is to determine whether the same performance gains can also be achieved in a low pressure application. Simulations were run in ANSYS CFX for seal designs with a helical stator and labyrinth rotor. Several labyrinth design parameters including the number of grooves and the groove width and depth are varied while the helical variables such as the groove width and depth as well as helix angle are kept constant. The data obtained are analyzed using backward regression methods and various response plots to determine the relationship between the design parameters and mass flow and power loss. The optimized helical design was simulated and the axial pressure profiles of the designs were compared to analyze the mechanism of the mixed helical-labyrinth seal. Then, the same labyrinth seal designs were simulated for a labyrinth rotor and a smooth stator to determine whether the optimal number of grooves, groove width and groove depth change due to the helical stator. The findings of this study show the effectiveness of mixed helical labyrinth grooved seals for both low and high pressure cases, and thus their efficiency and reliability for numerous industrial applications.
First-Principle Investigation of Structural, Elastic, Electronic and Thermal Properties of Dysprosium Hafnate Oxides
Authors: Niu Hui
Published: January 2019

Systematic first-principles calculations based on density functional theory were performed on Dy2HfxO3+2x (x = 0, 1, and 2) compositions. A complete set of elastic parameters including elastic constants, Hill’s bulk moduli, Young’s moduli, shear moduli and Poisson’s ratio were calculated. Analyses of densities of states and charge densities and electron localization functions suggest that the oxide bonds are highly ionic with some degree of covalency in the Hf-O bonds. Thermal properties including the mean sound velocity, Debye temperature, and minimum thermal conductivity were obtained from the elastic constants.
Experimental Specimen for Classification of Matrix Compression Damage in Carbon Fiber Reinforced Polymers
Authors: Rawlings Taylor J. , Carpenter Kevin T. , Parmigiani John P.
Published: January 2019

Composite materials are becoming increasingly common in the aerospace industry. In order for simulation and modeling to accurately predict failure of composites, a material model based on observed damage mechanisms is required. Composites are commonly classified into four damage categories based on the composite constituents and their loading condition: fiber tension, fiber compression, matrix tension, and matrix compression. Previous work identified a compact compression (CC) specimen as a suitable option for isolating matrix compression damage. However upon continued testing, stable crack propagation in the specimen was limited to a relatively low material failure ratio (σCompressive/σTension). This paper presents specimen geometry that can isolate matrix compression damage in materials with a failure ratio greater than two, the limit of the compact compression specimens. Initial specimen selection used the compact compression specimens from previous research and added additional specimens based on commonly used compressions specimens for different materials. The added specimens included center notched compression (CNC), edge notch compression (ENC), and four-point bending (4PB). All specimens were evaluated experimentally with the success criteria of controlled propagation of a matrix compression crack. In addition to propagating a controlled matrix compression crack, specimens were required to have a visible region around the stress concentrator to allow for digital image correlation (DIC) image capture during the experiments. The specimens were manufactured from a carbon fiber reinforced polymer (CFRP) with a failure ratio greater than six. CC and 4PB specimens were unable to produce a compression crack before any other failure methods were present. CNC specimens produced an unstable compression crack that progressed from the notch to the edge of the specimen too rapidly to acquire meaningful crack propagation data. ENC specimens showed some ability to stably propagate a crack, however some tests resulted in an unstable crack propagation similar to the CNC specimens. In order to increase the test repeatability, a tapered thickness was added to the specimen around the notch tip. The resulting tapered ENC (TENC) produced repeatable controlled matrix compression crack propagation. Ultimately, the specimen fails when the crack has propagated through the entire width of the specimen. TENC specimens show promise for isolating matrix compression damage in materials with high failure ratios. Continued testing of CFRP with TENC specimens could be used to refine the material model for finite element analysis.
Power Flow Topology of Supercritical Carbon Dioxide Power Generation System and its Application in Modeling and Optimization
Authors: Chen Qun , Li Xia , Chen Xi
Published: January 2019

The supercritical carbon dioxide (sCO2) power generation system holds tremendous potential in nuclear, chemical and renewable energy utilization fields due to its compactness, security and high efficiency. However, the dramatic variation in the physical property of sCO2 complicates the system analysis and optimization. Recent researches usually took simple stack of all governing equations of individual components as the physical model of system. Besides, based on the traditional heat transfer modeling method, some researches apply the segmentation method to take fluid property variation into consideration. These methods exacerbate the multivariate nonlinearity of the system and are not suitable to analyze complex sCO2 thermal systems. Moreover, taking the consideration of the strong nonlinearity of sCO2 system, most researches adopt single parameter analysis to obtain the optimum solution, which may not achieve global optimization. In this contribution, introduction of a new definition of thermal resistance of heat exchanger disassembles the original implicit nonlinear properties of heat transfer processes as the linear relation between inlet temperature difference of fluids and heat flow rate, and the explicit nonlinear expression of thermal resistance. For the nonlinearity caused by the variable properties of sCO2, segmentation is also used in heat exchanger modeling. However differently, the introduction of new defined thermal resistance enables the elimination of most intermediate variables produced by segmentation, which contributes to the connection of all segments in heat exchanger into a heat exchanger network. Furthermore, based on the system layout, the equivalent power flow diagram of the system is built to derive the corresponding governing equations revealing the overall transfer and conversion laws of heat. Combining the flow resistance balance equations of all components and the accompanying power flow processes constraints offers the inherent physical constraints among operating parameters. Benefit from the conciseness of system model, the genetic algorithm can be used for the model optimization. Taking thermal efficiency of the system as the optimization objective, the optimal matching of the operating parameters under variable working conditions is obtained.
A Novel Technique for Estimation of the Solid Electrolyte Interphase Film Resistance for Li-Ion Batteries
Authors: Arora Shashank
Published: January 2019

Solid electrolyte interphase (SEI) film resistance is an important parameter in the study of charge transfer kinetics of a Li-ion battery. The passive film affects diffusion process of Li-ions. As such, it becomes essential to include film resistance in battery modelling. However, the traditional method of estimating the SEI film resistance is costly and time consuming. An indirect approach based on Ohm’s law is thus presented in this paper. It relies on determining the interfacial polarisation from the difference of open-circuit voltage measured immediately after switching off the applied current and the equilibrium voltage. The technique is simple, easy to implement and can be used for a quick estimation of SEI film resistance with reasonable accuracy. For instance, average value of SEI film resistance for commercial LFP battery cell is measured as 0.004 Ohm · m2 , which was found to be consistent with the values determined using the impedance spectroscopy techhnique in the published literature for lithium-carbon film electrodes.
Genetic Algorithm-Based Design of Airfoil for the Root Region of Small Wind Turbines and Performance Analysis With Gurney Flaps
Authors: Ahmed Mohammed Rafiuddin , Ram Krishnil R. , Kim Bum-Suk , Lal Sunil P.
Published: January 2019

The root region of small wind turbines experience low Reynolds number (Re) flow that makes it difficult to design airfoils that provide good aerodynamic performance and at the same time, provide structural strength. In the present work, a multi-objective genetic algorithm code was used to design airfoils that are suitable for the root region of small wind turbines. A composite Bezier curve with two Bezier segments and 16 control points (11 of them controlled) was used to parametrize the airfoil problem. Geometric constraints including suitable curvature conditions were enforced to maintain the airfoil thickness between 18% and 22% of chord and a trailing edge thickness of 3% of chord. The objectives were to maximize the lift-to-drag ratio for both clean and soiled conditions. Optimization was done by coupling the flow solver to a genetic algorithm code written in C++, at Re = 200,000 and for angles of attack of 4 and 10 degrees, as the algorithm was found to give smooth variation of lift-to-drag ratio within such a range. The best airfoil from the results was tested in the wind tunnel as well as using ANSYS-CFX. The experimental airfoil had a chord length of 75 mm and was provided with 33 pressure taps. Testing was done for both free and forced transition cases. The airfoil gave the highest lift-to-drag ratio at an angle of 6 degrees with the ratio varying very little between 4 degrees and 8 degrees. Forced transition at 8% of chord did not show significant change in the performance indicating that the airfoil will perform well even in soiled condition. Fixed trailing edge flaps (Gurney flaps) were provided right at the trailing edge on the lower surface. The lift and drag behavior of the airfoil was then studied with Gurney Flaps of 2% and 3% heights, as it was found from previous studies that flap heights of 1% or greater than 3% do not give optimum results. The flaps considerably improved the suction on the upper surface and also improved the pressure on the lower surface, resulting in a higher lift coefficient; at the same time, there was also an increase in the drag coefficient but it was less compared to the increase in the lift coefficient. The results indicate that Gurney flaps can be effectively used to improve the performance of thick trailing edge airfoils designed for the root region of small wind turbines.
On the Dynamic Loading Effects of Soil on Plastic Water Distribution Pipes and its Significance for Leak Detection Using Acoustics
Authors: Scussel Oscar , Brennan Michael J. , Muggleton Jennifer M. , de Almeida Fabrício C. L. , Paschoalini Amarildo T.
Published: January 2019

Detection and location of leaks in buried plastic fluid-filled pipes are topics of increasing concern for water distribution companies. Acoustic correlation techniques have been widely used to provide an accurate estimate of the position of a leak in order to reduce the wastage of water. However, this technique depends on an accurate estimate of the wave propagation speed along the pipe, which is heavily dependent on the type of soil in which the pipe is buried. The soil also affects the distance that leak noise will propagate along the pipe. This paper describes theoretical and experimental investigations into the way the coupling conditions between the pipe and the soil affects the propagation characteristics of the wave that propagates leak noise in the pipe. Two water pipe systems which have different soil properties are considered: one is in Brazil and the other one is in UK. For the Brazilian pipe system, it is found that the shear modulus rather than the bulk modulus of the soil, has a profound effect on the wave motion in the pipe since it is buried in a clay-like soil. In this case, only the shear wave in the soil propagates away from the pipe. For the UK pipe system, which has sandy soil, both compressional and shear waves propagate away from the pipe. An analysis of the physical effects of fluid-pipe-soil interface and their corresponding parameters on the pipe wave speed and attenuation is also carried out. The results show that the axial coupling between the pipe and the soil has an important effect in the UK pipe system, but has a negligible effect in the Brazilian pipe system.
Finite Element Analysis of Contact Force Models During Solid Elastic and Plastic Bodies Impact
Authors: Rodrigues Gustavo Simão , Weber Hans Ingo , Driemeier Larissa
Published: January 2019

There are many models of impact used to predict the post-impact conditions of a system and all of them are based on Hertz’s theory, dated from the nineteenth century, where the repulsive force is proportional to the deformation of the bodies under contact and may also be proportional to the rate of deformation. The objective of this work is to analyze the behavior of the bodies during impact using some contact models and compare the results to a Finite Element Method model. The main parameters which will be evaluated are the body velocities, the contact force and the deformation of the bodies. An advantage of using the Finite Element Method is the possibility to apply plastic deformation to the model according to material definition. In the present study, it will be used Johnson–Cook plasticity model where the parameters are obtained based on empirical tests of real materials. Thus, it is possible to compare the behavior of elastic and plastic numerical models with the finite element model and to verify how these models reproduce the impact between solid bodies.
Avoidable and Unavoidable Exergetic Destruction Analysis of a Nitric Acid Production Plant
Authors: Fajardo J. , Valle H. , Buelvas A.
Published: January 2019

Exergy analysis for Nitric acid production plants are very few and many are outdated. This study aims to support existing scientific studies and incite new investigations of exergy analysis in modern times. An advanced exergy analysis was applied to a production plant with a capacity to process 350 tons/day of nitric acid at a concentration of 55%. The catalytic oxidation of ammonia, condensation and absorption of nitrous gases are considered as the principal process in the nitric acid production. The total destroyed exergy was 46772,55 KW. The component with the greatest impact was the catalytic converter, which presented 75.1% of the total avoidable exergy destruction rate of the plant. These findings are relevant as they can potentially reduce costs of nitric acid production.
Microstructural and Thermal Characterization of Diamond Nanofluids
Authors: Mashali Farzin , Languri Ethan M. , Mirshekari Gholamreza , Davidson Jim , Kerns David
Published: January 2019

Conventional heat transfer fluids such as water, ethylene glycol, and mineral oil, that are used widely in industry suffer from low thermal conductivity. On the other hand, diamond has shown exceptional thermal properties with a thermal conductivity higher than five times of copper and about zero electrical conductivity. To investigate the effectiveness of nanodiamond particles in traditional heat transfer fluids, we study deaggregated ultra-dispersed diamonds (UDD) using X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). Furthermore, nanodiamond nanofluids were prepared at different concentrations in deionized (DI) water as the base fluid. Particle size distribution was investigated using TEM and the average particle size have been reported around 6 nm. The thermal conductivity of nanofluids was measured at different concentrations and temperatures. The results indicate up to 15% enhancement in thermal conductivity compared with the base fluid and thermal conductivity increases with temperature and particle loading. The viscosity raise in the samples have been negligible.
3D Modeling of the Thermal Phenomena During Laser Melting of Polymers
Authors: Mokrane Aoulaiche , Boutaous M’hamed , Xin Shihe , Siginer Dennis
Published: January 2019

A comprehensive model of the selective laser sintering (SLS) process at the scale of the part is presented for application to polymeric powders. The powder bed is considered as a continuous medium with homogenized properties. A thermal model with detailed multiphysics coupling is presented. The model accounts for all elements of the thermal history : laser absorption, melting, coalescence, densification and volume shrinkage. For numerical resolution, a 3D in-house fortran code using FV method is developed. The proposed model is validated through the comparison of modeling data with experimental results available in the published literature. A parametric analysis about the thermal efficiency of the heating process against the laser energy input is proposed and the influence on the densification and thermal kinetics is discussed with regarding the evolution of the structure of the material.
An Experimental Investigation of Inclined Hole Drilling for CFRP Under Various Lubrication Techniques
Authors: Kannan Sathish , Pervaiz Salman , Ghoshal Abhishek
Published: January 2019

Carbon Fiber Reinforced Polymer (CFRP) is favoured in the aerospace, automotive, structural and sports-based industries due to its high strength-to-weight ratio, rigidity and comparatively higher stiffness. CFRP is termed as a difficult-to-machine material due to the problems associated with its machined quality, surface integrity and tooling cost. As per the industrial applications and requirements, drilling operation is mainly conducted on the CFRP material. Due to the layered structure of CFRP material, drilling operation produces defects such as delamination, burr formation, uncut fiber, fiber breakout and fiber pullout etc. These defects are mainly observed at the entrance and exit of the drilled hole. This poor surface finish and associated defects can play a very critical role towards the load carry capacity, reliability and service life of the final product, especially if the component is more prone to experience fatigue type of loading. There are several applications where the requirement is to have a hole at some inclination angle. To facilitate and develop the understanding of CFRP machining performance under inclined drilling, the presented study is focused on the drilling of inclined hole. The study will also incorporate different lubrication strategies such as dry cutting, conventional flood and minimum quantity lubrication (MQL) during the drilling of CFRP material.
Numerical Modeling of Phan-Thien-Tanner Viscoelastic Fluid Flow Through a Square Cross-Section Duct: Heat Transfer Enhancement due to Shear-Thinning Effects
Authors: Hagani Fouad , Boutaous M’hamed , Knikker Ronnie , Xin Shihe , Siginer Dennis
Published: January 2019

Non-isothermal laminar flow of a viscoelastic fluid through a square cross-section duct is analyzed. Viscoelastic stresses are described by the Phan-Thien – Tanner model and the solvent shear stress is given by the linear Newtonian constitutive relationship. The solution of the set of governing equations spawns coupling between equations of elliptic-hyperbolic type. Our numerical approach is based on the finite-differences method. To treat the hyperbolic part, the system of equations are rewritten in a quasilinear form. The resulting pure advection terms are discretized using high-order upwind schemes when the hyper bolicity condition is satisfied. The incompressibility condition is obtained by the semi-implicit projection method. Finally we investigate the evolution of velocity, shear stress, viscosity and heat transfer over a wide range of Weissenberg numbers.
Is Linear Camera Space Manipulation Impervious to Systematic Distortions?
Authors: Martinez Felipe , Mihalko Adam , Blum Lillian , Cardenas Antonio , Piovesan Davide
Published: January 2019

Raster imaging is a low cost application for the tracing of movements for biomedical applications. While of the shelf cameras can nowadays provide pictures with high resolution, the optics used can generate unwanted distortions. We evaluated the positional error obtained using a set of GoPro® cameras in conjunction with a Linear Camera Space Manipulation (LCSM) calibration model. The positioning error was compared with a post-processing algorithm to compensate for the radial distortion of a fisheye lens. We found that using the correction algorithm, the error is statistically lower, but the decrease is negligible for practical use. This demonstrates the imperviousness of LCSM to systematic errors of non-Gaussian nature.
Unmanned Underwater Drone Design for Ocean Exploration
Authors: Goonesekere Rojitha , Guo Yu
Published: January 2019

Human kind has always been intrigued by space but what seems to not make sense is why we aren’t just as intrigued about our ocean. As the life blood of all things on earth we need to understand the approximate 71% of water mass that surrounds us [1]. This is the goal of our paper, bringing interest back to the ocean using unmanned underwater vehicles. In this paper we will discuss the functionality, build and deployment of an intelligent unmanned drone. The mission of this underwater vehicle is to explore the ocean to understand complex ocean dynamics and bring forth the wonders of the ocean to the masses. We will systematically break down the design process of our drone circuitry and sensors on board, then see why we chose these components and sensors to successfully achieve our objective of collecting targeted data from the ocean.
Effectiveness of Evidence-Based Active Learning Pedagogies in Engineering Technology Courses
Authors: Ayoobi Mohsen , Ssemakula Mukasa , Djuric Ana
Published: January 2019

It is shown in the literature that in the traditional lecture teaching mode, students are mostly passive and do not actively engage in the learning process. Not being engaged in the learning process, students are more likely to lose interest in the material and less likely to comprehend material at a deep level. Consequently, students in traditional lecturing are more prone to simply target meeting the minimum requirements to pass a course. In contrast, active-learning pedagogies have been designed such that students are given the opportunity to engage in the learning process as active participants in the classroom. This promotes better comprehension of the concepts involved. At Wayne State University, statistics on students’ performance indicate that many students entering the Engineering Technology programs either drop or fail to pass courses with a C or better, with success rates being as low as 59% for some courses. To address this issue, the authors have adopted evidence-based active learning techniques in selected courses in the Mechanical Engineering Technology program. The Statics, Dynamics, and Applied Thermodynamics courses were targeted for this initial effort. Statics is a gateway course foundational to the rest of the program, Dynamics is taken right after Statics, and Thermodynamics is one of the most challenging senior level courses. These courses will serve as avenues for measuring the effectiveness (or otherwise) of using active learning techniques in engineering technology education. More specifically, the authors have adopted the following evidence-based techniques: in-class experiments, just-in-time teaching, team quizzes, and students as teachers. This paper describes the specific class activities that were undertaken when implementing the different techniques. The effectiveness of these techniques was measured using students’ persistence in the target courses and the final grades. In addition, standardized concept inventory tests were administered at the beginning and the end of the semester as another measure of the effectiveness of this implementation. Preliminary findings from this study indicate that this project has successfully fostered students’ interest, persistence, and performance.
Intelligent Adaptive Control for Anti-Lock Braking System
Authors: Batayneh Wafa , Jaradat Mohammad , Bataineh Ahmad
Published: January 2019

One of the most important safety features of an automobile is its braking system. The ability of a braking system to provide safe and repeatable stopping is the key to safe motoring. Mechatronics subsystems are more and more developed in automotive industries and in the recent years modern control techniques have been applied to a wide range of many electronic control systems in the automotive industry such as Anti-Lock Brake Systems (ABS).

This article proposed an intelligent adaptive control for anti-lock braking system (ABS), to control the desired slip ratio that prevents wheels from locking. A Fuzzy controller having Gaussian memberships is developed to calculate the amount of reduction of the applied torque based on the error signal (the difference between the measured slip ratio and the desired slip ratio).

Results of the proposed controller are compared with the results of a PID controller. The scheme is implemented using a quarter car model and simulation tests were carried out in different conditions. The simulation results show that the proposed scheme is robust and effective.
Truss Design and Optimization Using Stress Analysis and NURBS Curves
Authors: Caputi Antonio , Cohen Miri Weiss , Rizzi Caterina , Russo Davide
Published: January 2019

This paper presents a novel design methodology, which combines topology and shape optimization to define material distribution in the structural design of a truss. Firstly, in order to identify the best layout, the topology optimization process in the design domain is carried out by applying the BESO (Bidirectional Evolutionary Structural Optimization) method. In this approach, the low energy elements are eliminated from an initial mesh, and a new geometry is constructed. This new geometry consists of a set of elements with a higher elastic energy. This results in a new division of material providing different zones, some subjected to higher stress and others containing less elastic energy. Moreover, the elements of the final mesh are re-arranged and modified, considering the distribution of tension. This new arrangement is constructed by aligning and rotating the original mesh elements coherently to the principal directions. In the Shape Optimization stage, the resulting TO (Topology Optimization) geometry is refined. A process of replacing the tabular mesh is performed by rearranging the remaining elements. The vertices of the mesh are set as control polygon vertices and used as reference to define the NURBS (Non-Uniform Rational B-Spline) curves. This provides a parametric representation of the boundaries, outlining the high elastic energy zones. The final stage is the optimization of the continuous and analytically defined NURBS curve outlining the solid material domain. The Shape Optimization is carried out applying a gradient-based optimization method.
Investigation of Bubble Departure Radius in Subcooled Pool Boiling Under Microgravity Condition
Authors: Wang Xueli , Wu Zan , Wei Jinjia , Sunden Bengt
Published: January 2019

The bubble departure radius is a very important parameter for bubble dynamics during boiling heat transfer. In this study, experiments of highly subcooled nucleate pool boiling of FC-72 were conducted on two different sized silicon chips (chip S 2 × 2 and chip S 1 × 1) in short-term microgravity and normal gravity conditions by utilizing the drop tower in Beijing. During the experimental study, bubble dynamics were captured by a high-speed digital camera. From the images at the bubble departure moment, the bubble departure radius was obtained. Although the traditional force balance model is modified through the addition of a Marangoni force, it still cannot precisely predict the bubble departure radius in the microgravity condition, especially in the low heat flux regime. By using the advancing contact angle measured from the bubble departure moment instead of the static contact angle, and considering the bubble asymmetry due to the small bubble coalescence and the surrounding liquid motion, a revised force balance model is proposed. It can predict the experimental bubble departure radius within a deviation of ±3.8% for both silicon chips in the whole heat flux range.
Pool Boiling Heat Transfer of N-Pentane and Acetone on Nanostructured Surfaces by Electrophoretic Deposition
Authors: Wu Zan , Pham Anh Duc , Cao Zhen , Alber Cathrine , Falkman Peter , Ruzgas Tautgirdas , Sunden Bengt
Published: January 2019

This work aims to investigate pool boiling heat transfer enhancement by using nanostructured surfaces. Two types of nanostructured surfaces were employed, gold nanoparticle-coated surfaces and alumina nanoparticle-coated surfaces. The nanostructured surfaces were fabricated by an electrophoretic deposition technique, depositing nanoparticles in a nanofluid onto smooth copper surfaces under an electric field. N-pentane and acetone were tested as working fluids. Compared to the smooth surface, the pool boiling heat transfer coefficient has been increased by 80% for n-pentane and acetone. Possible mechanisms for the enhancement in heat transfer are qualitatively provided. The increase in active nucleation site density due to multiple micro/nanopores on nanoparticle-coated surfaces is likely the main contributor. The critical heat flux on nanostructured surfaces are approximately the same as that on the smooth surface because both smooth and modified surfaces show similar wickability for the two working fluids.
First and Second Law Analysis of a Flat Plate Collector Working With Nanofluids
Authors: Nitsas M. T. , Koronaki I. P. , Prentza L.
Published: January 2019

The utilization of solar energy in thermal energy systems was and always be one of the most effective alternative to conventional energy resources. Energy efficiency is widely used as one of the most important parameters in order to evaluate and compare thermal systems including solar collectors. Nevertheless, the first law of thermodynamics is not solely capable of describing the quantitative and qualitative performance of such systems and thus exergy efficiency is used so as to introduce the systems’ quality. In this work, the performance of a flat plate solar collector using water based nanofluids of different nanoparticle types as a working fluid is analyzed theoretically under the climatic conditions in Greece based on the First and Second Law of Thermodynamics. A mathematical model is built and the model equations are solved iteratively in a MATLAB code. The energy and exergy efficiencies as well as the collector losses coefficient for various parameters such as the inlet temperature, the particles concentration and type are determined. Moreover, a dynamic model is built so as to determine the performance of a flat plate collector working with nanofluids and the useful energy that can be stored in a water tank. The exergy destruction and exergy leakage are determined for a typical day in summer during which high temperatures and solar intensity values are common for the Greek climate.
Stabilization of Graphene Dispersions by Cellulose Nanocrystals Colloids
Authors: Illera Danny , Wickramaratne Chatura , Guillen Diego , Jotshi Chand , Gomez Humberto , Goswami D. Yogi
Published: January 2019

The outstanding properties of single-layer graphene sheets for energy storage are hindered as agglomeration or restacking leads to the formation of graphite. The implications of the aforementioned arise on the difficulties associated with the aqueous processing of graphene sheets: from large-scale production to its utilization in solvent-assisted techniques like spin coating or layer-by-layer deposition. To overcome this, aqueous dispersions of graphene were stabilized by cellulose nanocrystals colloids. Aqueous cellulose nanocrystals dispersion highlights as a low-cost and environmentally friendly stabilizer towards graphene large-scale processing. Colloids of cellulose nanocrystals are formed by electrostatic repulsion of fibrils due to de-protonated carboxyl or sulfate half-ester functional groups. Graphene dispersions are obtained by hydrothermal reduction of electrochemically exfoliated graphene oxide in the presence of cellulose nanocrystals. This approach allows the preservation of the intrinsic properties of the nano-sheets by promoting non-covalent interactions between cellulose and graphene. The dispersions could be cast to form free-standing flexible conducting films or freeze-dried to form foams and aerogels for capacitive energy storage.
Analysis of Phase Change Thermal Storage Configurations for Minichannel-Based Solar Collectors
Authors: Perez Julio C. , Hota Sai Kiran , Diaz Gerardo
Published: January 2019

Solar thermal collectors are efficient components that provide hot water for residential and commercial use. Over the years many techniques and approaches have been proposed in order to improve the efficiency of these systems. One of the improvements suggested has been the use of minichannel tubes as the absorber for a flat plate collector which has been found to be more efficient than a conventional flat plate collector. These collectors have received attention recently with significant research pertaining to enhancing performance. This paper discusses the effect of incorporating a Phase Change Material (PCM) storage system within an aluminum based solar collector. Three different configurations of integrating the PCM next to the aluminum minichannel based absorber plate have been analyzed. The simulations are performed in COMSOL Multiphysics® and the results analyzed to determine the most efficient configuration.
Reverberatory Furnace CFD Modeling for Efficient Design: Burners and Chimney Location
Authors: Alshehhi Saeed , Hassan Ali Mohamed I.
Published: January 2019

Reverberatory furnaces improper burners and chimney location would cause a significant scape of hot gases and shorten their residence time in the furnace and therefore reduce the convective heat transfer opportunity to the metal and walls surfaces. Appropriate burners location and orientation, as well as the chimney location, are very expensive to adjust in practical furnaces by trial and error to maximize the furnace performance. This study aimed to develop a validated 3-D CFD furnace model for studying the effect of burners’ location and orientation, chimney location and flow momentum on the hot gases residence time, heat transfer, flow and temperature distribution as well as the overall exergetic efficiency of the furnace. The results reflect the optimum design parameters for maximizing the furnace performance.
Adhesive Joints Under Impacting Shock Wave Loading
Authors: Yildiz Salih , Andreopoulos Yiannis , Delale Feridun
Published: January 2019

Many engineering structures, in applications such as automobiles, bridges, etc. are assembled by joining the different parts together. Therefore, joints in the mechanical applications play a critical role in durability, flexibility of the mechanical assemblies. Recent advances in adhesive technology have made adhesive joining one of the plausible options in many engineering applications that demand high impact resistance such as ground vehicle armor or civilian vehicles. However, because most of the polymer-based adhesives have non-linear mechanical behavior and loading rate sensitivity caused by their viscoelastic properties, characterization of the adhesives under different loading and environmental conditions become vital in the design of durable and reliable joints in any structure. This study investigated the mode I (bending) response of the adhesive joints to shock-wave loading generated in a large-scale shock tube. The critical failure pressure (P5) of adhesive joints was determined experimentally. Determining the material properties of the adhesive were estimated by the FEM parametric study, and energy absorption capacity of the adhesive joints under different strain rate loadings were investigated.
Vibration Suppression in Two-Dimensional Oscillation Dynamical Systems
Authors: Saeed Adnan S. , AL-Shudeifat Mohammad A.
Published: January 2019

During the past few decades, significant interest in applying linear and nonlinear dynamical vibration absorbers for energy transfer and dissipation has significantly arisen. The existing studies of employing dynamical absorbers with small and large-scale dynamical structures have been mostly focusing on suppressing the oscillations for structures that move in one direction only. However, most of these structures are vulnerable to different sources and types of excitations that could induce two-dimensional oscillations into these structures. Consequently, this paper presents an application of a vibration absorber to suppress the two-dimensional vibration induced into the structure caused by a two-dimensional impulsive loading. The system description and the governing equations are firstly introduced and then followed by an optimization process to maximize vibration suppression. The response of the system under various combinations of longitudinal and lateral impulsive loadings is presented and the capability of the proposed absorber to suppress the induced vibration is evaluated.
Theoretical Model of Droplets Motions on Solid Surface With Radial Wettable and Evaporation Rate Gradients
Authors: Yang Yanjie , Wu Zan , Chen Xiaoqian , Sundén Bengt , Huang Yiyong
Published: January 2019

Wettability gradient in radial direction and evaporation rate gradient can cause droplet motion on a solid surface. Here a theoretical model is proposed. Besides, an equation of droplet velocity is derived on a solid surface. We consider the wettability and evaporation rate gradients are mainly caused by the chemical composition and surface roughness, only along the radial direction. Surface tension at the liquid-vapor interface is constant as it is assumed that the temperature does not change during the whole process. Thus, Marangoni effect induced by the liquid-vapor surface tension gradient is neglected. Besides, as droplet size is set as less than the capillary length (l=γ/ρg), the gravity effect is ignored as well. The velocity at the droplet center on a gradient surface along the radial direction is half of that along the x-direction. With the simulation of water droplet, the center velocity decreases with time and the droplet radius increases at the beginning part and then decreases.
Viscoelastic Properties of the L3-L4 Myofascial Tissue in Ankylosing Spondylitis Patients
Authors: White Allison , Abbott Hannah , Masi Alfonse , Nair Kalyani
Published: January 2019

Ankylosing spondylitis (AS) is a degenerative rheumatological disorder that mainly affects the spine. It has been reported that different degrees of human resting myofascial tone (HRMT) would affect spinal stability and may predispose to the respective curvature deformities of adolescent idiopathic scoliosis (AIS) and the enthesopathy of ankylosing spondylitis (AS). Although osteoligamentous impacts are prominently recognized in many chronic spine and low back conditions, no research has been performed on the possible role of passive axial (spinal) myofascial tone as a causative factor. In this particular study, the passive muscle properties of the lower lumbar regions of 24 healthy adults and 24 adult AS subjects were examined. Our recent publications examined the linear elastic properties among normal and AS subjects. In this study, those analyses are expanded to include detailed analysis and correlations of the linear elastic property of stiffness to two viscoelastic properties: stress relaxation time (SRT) and creep. Analyzed data supports the hypothesis that resting muscle properties of the lower lumbar muscles hold significance in differentiation of human back health between healthy and diseased subjects, but more testing should be performed to support this study’s results.
Influence of Renewable Gas Addition to Natural Gas on the Combustion Performance of Cooktop Burners
Authors: Zhao Yan , Choudhury Shiny , McDonell Vincent
Published: January 2019

This paper investigates the combustion performance of a commercial cooktop burner operating on natural gas and renewable biogas. Various blends of carbon dioxide and methane are used to simulate biogas and fed as fuel to the cooktop burners. Combustion operation on standard pipeline natural gas is taken as a reference for comparison with other fuel classes. In this study, different configurations of cooktop burners available in the market were investigated to establish similarities and differences. Based on the current regulations and testing standards, a protocol for testing and evaluating the cooktop burner combustion performance was generated and adopted in this research. Experimental investigation of the flame characteristics, ignition properties, cooking efficiency, and emissions (CO, NOx, UHC) were studied as a function of gas composition. The results indicate that, based on the overall performance of the cooktop burners, up to 5% CO2 can be added to pipeline natural gas without impacting operation. Different methodologies of analyzing emissions were compared with each other, which can provide insight into future emission regulations on open-air residential or light industrial burners.
Interactive Educational Testbed for Statics and Mechanics of Materials
Authors: He Zhelong , Liu Qingchang , Yang Katherine , Pest Niemann , Xu Baoxing , Kerrigan Jason , Pindera Marek-Jerzy
Published: January 2019

A mechanics education testbed comprised of instructional modules written in Mathematica was developed in order to increase the effectiveness of course delivery through an integrated computation, visualization, and animation approach with the aim of accelerating the learning process. Overall, 25 modules were developed for Statics and another 20 modules for Mechanics of Materials during the AY2017-18. The testbed complements class instruction and motivates self-learning by illustrating basic mechanics concepts relative to homework problems and textbook examples. Its features include visualization, parametrization, and trial-and-error simulation capabilities that enable students to view simulated phenomena from different perspectives, thereby leaving a lasting impression which facilitates quicker absorption of the mechanics concepts than the traditional approach. The parametrization feature enables variation of boundary and initial conditions, as well as other parameters that affect the simulated phenomenon to demonstrate each parameter’s influence on the system response. These capabilities enable students to employ the trial-and-error approach in acquiring an intuitive understanding of the visualized phenomenon, validated through direct calculation. Student comments are summarized and survey results are analyzed and related to individual student performance. Student assessment confirms the testbed’s effectiveness and provides helpful suggestions for further enhancement/development. Representative modules are presented to demonstrate their functions and capabilities.