bluuebunny/crossref_metadata_2025 huggingface dataset:
A Monte Carlo Study of Molecular Spintronics Devices
Authors: Tyagi Pawan , D’Angelo Christopher
Published: April 2014

Molecular spintronics devices (MSDs) are capable of harnessing the controllable transport and magnetic properties of molecular device elements and are highly promising candidates for revolutionizing computer logic and memory. These advanced MSD can enable the next generation of instrumentation and control devices for the wide range of mechanical engineering systems. A MSD is typically produced by placing magnetic molecule(s) between the two ferromagnetic electrodes. Recent experimental studies show that some magnetic molecules produced unprecedented strong exchange couplings between the two ferromagnetic electrodes, leading to intriguing magnetic and transport properties in a MSD. Future development of MSDs will critically depend on obtaining an in-depth understanding of the molecule induced exchange coupling, and its impact on MSD’s switchability, functional temperature range, stability etc. However, the large size of MSD systems and unsuitable device designs are the two biggest hurdles in theoretical and experimental studies of magnetic attributes produced by molecules in a MSD. This research theoretically studies the MSD by performing Monte Carlo simulations (MCS). The effect of magnetic molecule induced exchange coupling was studied at different temperature and for different device sizes — represented by a 2D Ising model. Our MCS shows that thermal energy of the MSD strongly influenced the molecular coupling effect. We studied the effect of a wide range of molecule-metal electrode couplings on the fundamental properties of MSDs. If molecules induced exchange coupling increased beyond a threshold limit a MSD acquired dramatically new attributes. Our MCS exhibited that the transition points in MSD’s magnetic properties was the interplay of temperature and molecular coupling strength. These simulations will allow the understanding of fundamental device mechanisms behind the functioning of novel MSDs. Our MSD model represents a myriad of magnetic molecules and ferromagnets combinations promising for realizing experimental MSDs. These MCS will also assist in designing new class of MSDs with desired attributes for advanced computers and control systems.
An Approximate Solution for Period-m Motions in a Periodically Forced Oscillator With Quadratic Nonlinearity
Authors: Luo Albert C. J. , Yu Bo
Published: April 2014

The approximate analytical solutions of the period-m motions for a periodically forced, quadratic nonlinear oscillator are presented. The stability and bifurcation of such approximate solutions in the quadratic nonlinear oscillator are discussed. The bifurcation tree of period-1 to chaos is presented. Numerical simulations for period-1 to period-4 motions in such quadratic oscillator are carried out for comparison of approximate analytical solutions. Such an investigation provides how to analytically determine bifurcation of periodic motion to chaos.
Towards a Geometric Deviation Model of Product in CAD Environment
Authors: Nguyen Dinh Son
Published: April 2014

Due to development of science and information technology, computer has become an effective and useful tool supporting for product design activities. The numerical model of product is quickly created in Computer-Aided-Design (CAD) environment by product designers. However, this model is a nominal model representing ideal geometric information of product. It is not able to cope with various kinds of disturbances during the whole product life-cycle, especially in manufacturing stage where geometric deviations of product are generated and accumulated by material property defects, manufacturing process errors, tooling deformation, etc. This is a limitation of the current product modeling technology. In addition, most of the simulations of product performance such as kinematics, dynamics, failure, etc., are carried out by using this nominal model. It can make the quality of the product designed not to fully meet the requirements of customers and users. Thus, the paper proposes a method that allows integrating geometric deviations of product in CAD environment. The aim is to deal with the above issues and to take into account various disturbances in product performance prediction.
Wavelet Element Method for Computing Band Structures of Phononic Crystals
Authors: Liu Zhangyi , Wu Jiu Hui
Published: April 2014

In this paper we combine biorthogonal wavelet systems with the philosophy of Spectral Element Method to obtain a biorthogonal wavelet system on fairly general bounded domains. We also extend the boundary adaption of wavelet elements to first order derivatives allowing the construction of basis functions that exactly satisfy boundary conditions. Since this method allows us to take advantage of structural features of phononic crystals and the boundary conditions are satisfied rigorously, a better accuracy and higher efficiency can be obtained.
The Protein-Driven Ciliary Motility in Embryonic Nodes: A Computational Model of Ciliary Ultrastructure
Authors: Chen Duanduan , Shinohara Kyosuke , Ren Jun , Hamada Hiroshi
Published: April 2014

The movement of embryonic cilia presents a crucial function in specifying left-right axis for vertebrates. Those mono-cilia are primary (9+0) cilia, whose characteristic architecture is based on a cylindrical arrangement of 9 microtubule doublets. Dynein motors located between adjacent doublets convert the chemical energy of ATP hydrolysis into mechanical work that induces doublet sliding. Passive components, such as the mediated cytoplasm, the ciliary membrane, and other possibly-existent structures constraint the ciliary motion and maintain the cilia structural integrity, thus resulting in the axonemal bending. Dynein motors located along microtubule doublets in a motile nodal cilium activate in a sequential manner. However, due to inherent difficulties, the dynein activation patterns in moving cilia can hardly be directly observed. The exact mechanism that controls ciliary motion is still unrevealed.

In this work, we present a protein-structure model reconstructed from transmission electron microscopy image set of a wide-type embryonic cilium to study the dynein-dependent ciliary motility. This model includes time accurate three-dimensional solid mechanics analysis of the sliding between adjacent microtubule doublets and their induced ciliary bending. As a conceptual test, the mathematical model provides a platform to investigate various assumptions of dynein activity, which facilitates us to evaluate their rationality and to propose the most possible dynein activation pattern. The proposed protein-trigger pattern can reproduce the rotation-like ciliary motion as observed by experiments. Further application of this approach to mutant cilia with ultrastructural modifications also shows consistency to experimental observations. This computational model based on solid mechanics analysis may improve our understandings regarding the protein-beating problems of cilia, and may guide and inspire further experimental investigations on this topic.
Modeling Prion Transport in a Tunneling Nanotube
Authors: Kuznetsov Ivan A. , Kuznetsov Andrey V.
Published: April 2014

We develop a model for simulating prion transport in a tunneling nanotube (TNT). We simulate the situation when two cells, one of which is infected, are connected by a TNT. We consider two mechanisms of prion transport: lateral diffusion in the TNT membrane and active actin-dependent transport inside endocytic vesicles. Endocytic vesicles are propelled by myosin Va molecular motors. Since the transit time of prions through a TNT is short (several minutes), the two population model developed here assumes that there is no interchange between the two prion populations, and that partitioning between the prion populations is decided by prion loading at the TNT entrance. The split between the two prion populations at the TNT entrance is decided by the degree of loading, which indicates the portion of prions that enter a TNT in endocytic vesicles. An analytical solution describing prion concentrations and fluxes is obtained.
Modeling Leftward Flow in the Embryonic Node
Authors: Kuznetsov A. V. , Blinov D. G. , Avramenko A. A. , Shevchuk I. V. , Tyrinov A. I. , Kuznetsov I. A.
Published: April 2014

The establishment of the left-right asymmetry during the development of vertebrates is a fascinating phenomenon that is still not fully understood. Extensive research suggests that in mice a small triangular cavity, called the ventral node, is responsible for breaking the left-right symmetry. A mouse node is ∼ 50 microns across and ∼10 microns deep. The surface of the nodal pit is covered by 200–300 monocilia whose rotation is responsible for the leftward flow in the node. We developed a simplified method of modeling the extraembryonic fluid flow and morphogen transport in a nodal cavity. We simplified the problem as flow in a 2D cavity; the effect of rotating cilia was modeled by specifying a constant vorticity at the edge of the ciliated layer. We also developed approximate solutions for morphogen transport in the nodal pit. The solutions were obtained utilizing the proper generalized decomposition method. We compared our approximate solutions with the results of numerical simulation of flow caused by the rotation of 81 cilia, and obtained reasonable agreement in most of the flow domain. We discuss locations where agreement is less accurate. The obtained semi-analytical solutions enable a quick analysis of flow and morphogen distribution in a nodal pit.
Non-Reflective and Highly Dissipative Acoustic Metamaterials
Authors: Sadeghi Hossein , Srivastava Ankit , Nemat-Nasser Sia
Published: April 2014

In this paper, we consider a composite embedded in a homogenous medium and present a method to design the composite’s microstructure so that when it is subjected to an incident acoustic wave, it does not reflect the incoming wave and also dissipates most of it. High dissipation is achieved through a metamaterial design which is naturally characterized by internal resonance. The effective impedance of the metamaterial is evaluated through dynamic homogenization technique and it is used to design a quarter wave transformer to enforce zero reflection at the interface between the metamaterial composite and its surrounding medium. Transfer matrix method is used to calculate the reflection/transmission spectra at the above mentioned interface. Results show that the reflection at the interface is close to zero at the designed frequency and a large fraction of the wave energy which is transmitted across the interface is attenuated.
Robust and Dynamically Consistent Reduced Order Models
Authors: Segala David B. , Chelidze David
Published: April 2014

The need for reduced order models (ROMs) has become considerable higher with the increasing technological advances that allows one to model complex dynamical systems. When using ROMs, the following two questions always arise: 1) “What is the lowest dimensional ROM?” and 2) “How well does the ROM capture the dynamics of the full scale system model?” This paper considers the newly developed concepts the authors refer to as subspace robustness — the ROM is valid over a range of initial conditions, forcing functions, and system parameters — and dynamical consistency — the ROM embeds the nonlinear manifold — which quanitatively answers each question. An eighteen degree-of-freedom pinned-pinned beam which is supported by two nonlinear springs is forced periodically and stochastically for building ROMs. Smooth and proper orthogonal decompositions (SOD and POD, respectively) based ROMs are dynamically consistent in four or greater dimensions. In the strictest sense POD-based ROMs are not considered coherent whereas, SOD-based ROMs are coherent in roughly five dimesions and greater. Is is shown that in the periodically forced case, the full scale dynamics are captured in a five-dimensional POD and SOD-based ROM. For the randomly forced case, POD and SOD-based ROMs need three dimensions but SOD captures the dynamics better in a lower-dimensional space. When the ROM is developed from a different set of initial conditions and forcing values, SOD outperforms POD in periodic forcing case and are equal in the random forcing case.
Spreading-Droplet Simulation With Surface Tension Model Using Inter-Particle Force in Particle Method
Authors: Ishii Eiji , Sugii Taisuke
Published: April 2014

Predicting the spreading behavior of droplets on a wall is important for designing micro/nano devices used for reagent dispensation in micro-electro-mechanical systems, printing processes of ink-jet printers, and condensation of droplets on a wall during spray forming in atomizers. Particle methods are useful for simulating the behavior of many droplets generated by micro/nano devices in practical computational time; the motion of each droplet is simulated using a group of particles, and no particles are assigned in the gas region if interactions between the droplets and gas are weak. Furthermore, liquid-gas interfaces obtained from the particle method remain sharp by using the Lagrangian description.

However, conventional surface tension models used in the particle methods are used for predicting the static contact angle at a three-phase interface, not for predicting the dynamic contact angle. The dynamic contact angle defines the shape of a spreading droplet on a wall. We previously developed a surface tension model using inter-particle force in the particle method; the static contact angle of droplets on the wall was verified at various contact angles, and the heights of droplets agreed well with those obtained theoretically. In this study, we applied our surface tension model to the simulation of a spreading droplet on a wall. The simulated dynamic contact angles for some Weber numbers were compared with those measured by Šikalo et al, and they agreed well. Our surface tension model was useful for simulating droplet motion under static and dynamic conditions.
The Impact of Hemorheology on Wall Shear Stress in a Separated and Reattached Flow Region
Authors: Hammad Khaled J.
Published: April 2014

Wall-bounded separating and reattaching flows are encountered in biological applications dealing with blood flows through arteries and prosthetic devices. Separated and reattached flow regions have been associated in the past with the most common arterial disease, atherosclerosis. Previous studies suggest that local wall shear stress (WSS) patterns affect the location and progression rate of atherosclerotic lesions. A parametric study is performed to investigate the influence of hemorheology on the wall shear stress distribution in a separated and reattached flow region. Recent hemorheological studies quantified and emphasized the yield stress and shear-thinning non-Newtonian characteristics of unadulterated human blood. Numerical solutions to the governing equations that account for yield stress and shear-thinning rheological effects are obtained. A low WSS region is observed around the flow reattachment point while a peak WSS always exists close to the vortex center. The yield shear-thinning hemorheological model always results in the highest observed peak WSS. The yield stress impact on WSS distribution is most pronounced in the case of severe restrictions to the flow.
Numerical Investigation of JaVA-Induced Flow in Quiescent Water
Authors: Cadirci Sertac , Gunes Hasan , Rist Ulrich
Published: April 2014

A Jet and Vortex Actuator (JaVA) is an oscillatory, zero-net-mass flux active flow control device which has been investigated numerically in quiescent water. JaVA consists of a vertically moving actuating plate and ejects jets or vortices into the quiescent fluid. Main JaVA-induced flow regimes include jets to different orientations and vortex mode.

In this paper, we investigate the effect of the wide gap on the flow characteristics. Three cases consisting of two jets and one vortex mode are presented in detail where the jet-Reynolds number and the scaled amplitude are kept constant. Computational results have been reported to depict instantaneous fields and reveal temporal behavior of JaVA-induced flows in quiescent fluid. In addition, the phase-averaged flow fields have been obtained for suction and blowing phases. The velocity profiles extracted from phase-averaged flow fields across the wide gap supply further insight into the JaVA-induced flow regime and their effectiveness in flow control.
Effective Use of Engineering in Teaching Secondary STEAM Courses: A Robotics Course Example
Authors: Cost Diana , Chin Jessica , Zeid Ibrahim , Duggan Claire , Kamarthi Sagar
Published: April 2014

Global Learning Charter Public School (GLCPS) is an urban secondary school located in the city of New Bedford, Massachusetts. GLCPS educates students in grades 5–12. It is a Title I school with over 74% of the student population on free and reduced lunch. Historically, only 60% of students graduating from New Bedford move on to postsecondary education. It is the goal of our school to change this and increase the number of students entering post secondary education and more specifically to increase their interest in STEAM (science, technology, engineering, arts, and math) fields.

GLCPS provides a unique educational experience where students demonstrate academic excellence and mastery of essential skills. These skills include: technology literacy, public speaking, global citizenship and arts exploration. Incorporation of STEAM (science, technology, engineering, art, and mathematics) is a continued goal for our school. After attending teacher educator training/professional development in engineering-based learning (EBL), we decided to create a robotics course, which fully embedded EBL into the curriculum. The goal of this robotics course is two fold: 1) Combine engineering, math, science, and art/creativity into one course; and 2) engineering-based learning can impact the way students learn STEAM principles, retain STEAM theory, and apply them to real world, relevant applications.

The purpose of this paper is to illustrate how engineering-based learning inspired and impacted the development of a robotics course in an urban, financially disadvantaged, secondary charter school. Specifically, we detail how the principles and tools of the engineering-based learning pedagogy affected the development and implementation of this robotics course. Lastly, we will demonstrate how EBL and the robotics course have changed student perceptions of science, engineering, and math.
A New Concept for Reconfigurable Planar Motion Generators
Authors: Larochelle Pierre , Venkataramanujam Venkatesh
Published: April 2014

This paper presents a novel concept for Reconfigurable Motion Generators (RMGs) for multi-phase planar motion generation. Reconfigurable Motion Generators are a new class of mechanical devices that are designed for a specific part family and their associated motion generation tasks.

Reconfigurable Motion Generators are capable of configuration changes according to variations in the motion generation requirements. Thus, Reconfigurable Motion Generators bridge the gap between the relatively high flexibility and high cost of totally flexible machines (e.g. industrial robots) and the low flexibility and low cost of fully dedicated mechanisms (e.g. cams & linkages). Here, we propose the concept of planar Reconfigurable Motion Generators for multi-phase motion generation tasks. This paper introduces design concepts and principles for the efficient and effective synthesis of Reconfigurable Motion Generators that may be deployed in various automated manufacturing environments.
Comparison of Signal Filtering Techniques for Ultrasonic Waves Used in Inspection of Composite Materials
Authors: Pereira Paulo , Rodovalho Tainá G. , Ambiel Leandro B. , Garcia Rafael H. , Leão Rodrigo J. , dos Santos Auteliano A.
Published: April 2014

The use of composite materials is growing worldwide as the number of its applications. Regarding the quality of components made from composites especially in fields that require high safety standards, such as aerospace, reliable inspection techniques must be used. Nondestructive inspection techniques using ultrasonic waves are largely employed in metals for fault detection, characterization, and stress measurement and they are also being applied in composites. However, composites are heterogeneous in nature and thus the signals acquired from ultrasonic transducers in these materials exhibit high noise, leading to inaccurate measurements. The objective of this work is to evaluate digital filtering techniques for signals from ultrasonic longitudinal bulk waves and longitudinal critically refracted (LCR) waves propagating in a carbon fiber-epoxy prepreg. Samples of unidirectional composites were manufactured to study the signals of waves propagating at different angles in relation to the carbon fibers direction. For bulk waves, we acquired signals at 0, 15, 30, 45, 60, 75 and 90° from the fiber directions; for LCR waves, the signals were measured at 0 and 90°. We compared the techniques based on digital filters IIR (Infinite Impulse Response), FIR (Finite Impulse Response) and Discrete Wavelet Transform (DWT). The results show that the filters FIR and IIR have the best signal-to-noise ratio (SNR) for most propagation directions, both for bulk and LCR waves.
Random Vibration Fatigue: Frequency Domain Critical Plane Approaches
Authors: de Morais Teixeira Giovanni , Hazime Radwan , Draper John , Jones Dewi
Published: April 2014

Frequency domain analysis offers a very efficient method for the fatigue durability assessment of structures subjected to vibration loading. It also allows engineers to gain valuable insight into system behavior and characteristics that are not easily recognized in the time domain. With some reasonable assumptions, most importantly linearity and steady state behavior, the response of a structure in many engineering applications can be simply evaluated through the “scaling” of the input signal by the Frequency Response Functions (FRFs). In cases where the input is random or stochastic in nature additional assumptions are needed to assess the behavior of the system. Usually such cases assume a stationary and ergodic input signal with a zero mean Gaussian distribution. When making such assumptions the system is still characterized by its FRFs. However, since the input signal is random it can be best described by its Power Spectral Density (PSD). Furthermore, the system response (characterized by the stress tensor) can be evaluated by “scaling” the PSD of the input signal(s) by the magnitude squared of the stress FRFs. The linearity assumption also allows the evaluation of a system response due to multiple inputs through superposition principles.

When using stress based fatigue (to assess the durability of a component or a structure) there are several damage evaluation methodologies that can be used. Traditionally, for time domain analysis the von Mises equivalent stress had been the methodology of choice. More recently critical plane search methods have gained popularity and have shown much better correlation with laboratory experiments and field failures, especially under multi-axial and non-proportional loading. Some of these methods have found their way into frequency domain analysis. This paper highlights the application of critical plane methods for the multi-axial fatigue assessment of engineering structures that are subjected to non-deterministic random vibration. A case study is presented to illustrate the process and shows how the proposed method works.
Influence of the Aerodynamic Vibration Excitation on the Turbine Blade Vibration in a Vehicle Turbocharger
Authors: Shan Shujun , Hou Anping , Zheng Xinqian , Zhang Zhang , Zhang Mingming
Published: April 2014

A fluid-solid coupled approach is presented for investigating turbine blade fatigue life in a vehicle turbocharger under the parallel computation of aeroelasticity. The unsteady flow field of rotor is studied in a CFD model of the turbine flowpath, coupled with a finite element model for the impeller to identify modal shapes, natural frequencies, vibratory stress and the structural deformations. Based on the interface exchange of information between the fluid and structural domains, interactions between fluid and structure are calculated in a coupled manner. The numerical simulation is proceeded under different angle of attack and back pressure. In addition the influence of inlet total pressure fluctuation is considered. The inlet total pressure fluctuation is the function of 1st and 3rd natural frequency of impeller. The result shows that the maximum stress is less than the yield stress. The fatigue life will overpass ten million cycles.
Forensic Examination and Failure Analysis of a 220 MV Step-Up Transformer Fire
Authors: Ibrahim Zuhair , Stepan Jeremiah , Reza Ali , Slee Daren
Published: April 2014

The paper presents the results of investigation and engineering analysis by Exponent of the failure of a 220 MVA generator step-up transformer in Southern California. The incident was caused by a dielectric breakdown from the high side phase C bushing to the side wall of the transformer. The ensuing fire continued for 27 hours, fueled by approximately 11,000 gallons of dielectric HYTRANS 61 oil. The paper will discuss the investigation, conducted per the IEEE C57.125 “Guide for Failure Investigation, Documentation, and Analysis for Power Transformers and Shunt Reactors.” [1], and the engineering review and analysis to identify the likely failure scenario(s).
Constitutive Modeling of PLZT Ceramics Based on the Photovoltaic Effect and the Viscoelastic Effect
Authors: Huang J. H. , Wang X. J. , Wang J.
Published: April 2014

Lead lanthanum zirconate titanate (PLZT) ceramics can transform the light energy into the mechanical energy without electric lead wires. The optical and direct drive based on PLZT ceramics, which is also green drive and non-contact drive, has many advantages in micro-driven and structure vibration control. However, the response of the photo-deformation is far slower than the photovoltage and the photocurrent, and the hysteresis and nonlinear of the photo-deformation prevent PLZT from applying to actuation and active structure vibration control. In this paper, a novel mathematical model based on the photovoltaic effect and the viscoelastic effect was established. The novel mathematical model was validated through experiments. According to the new expression of photo-deformation, the viscoelastic effect leading to the hysteresis and nonlinear of the photostrictive response was analyzed.
Effects of Blade Tip Geometries on the Aerodynamic Performance of a Compressor Cascade
Authors: Ma Hongwei , Zhang Jun , Wei Wei
Published: April 2014

This paper presents a numerical simulation of effects of blade tip geometries on the flow field of a compressor cascade. The tip geometries include flat tip (baseline), tip with cavity, tip with pressure side extension and suction side squealer tip. For the tip with cavity and pressure side extension, the mass of the leakage flow is reduced. The loss in the tip gap of the cavity tip is greater than the baseline because of the interaction of the cavity flow and the leakage flow. For the tip with pressure side extension, the loss in the gap is also greater than the baseline. The main reason is that the greater blade width makes the mixing process of the leakage flow in the gap more sufficient than the baseline. For both these two cases, the turning angle of the cascade becomes smaller and the pressure rise of the cascade is lower than the flat tip case. For the suction side squealer tip, the greater curvature of squealer increases the blade loading. The turning angle of the cascade and the pressure rise becomes greater which increases total pressure loss slightly.
Numerical Analysis of the Thermal Dissipation in Horizontal Isothermal Eccentrically Insulated Cylinders by Free Convection
Authors: Malateaux Ezequiel C. , Milanez Luiz F.
Published: April 2014

Heat transfer in horizontal concentrically insulated cylinders exposed to free convection is of importance in industry. However, the NuD and the surface temperature are not constant around the cylinder, raising the point that the use of concentric insulation may not be the best way to arrange the insulating layer. Thus, if an eccentric layer is used, the surface temperature should have a larger variation, changing the flow around the cylinder and the heat dissipation. A numerical analysis of the heat dissipation in horizontal isothermal eccentrically insulated cylinders exposed to free convection (Pr ≅ 0.715) is presented. The conduction through the insulating layer was solved analytically (using the bicylindrical coordinate system) and integrated numerically, while the free convection was solved by the PHOENICS software. The parameters analyzed were the ratio between the outer and inner radius of the insulating layer, the ratio between the insulation and air thermal conductivities, the Rayleigh number and the eccentricity of the insulation. An equation is suggested to calculate the total heat of an eccentric arrangement in terms of the total heat of the corresponding concentric arrangement and the ratio between the convective and conductive thermal resistances, for a given ratio of radius and eccentricity.
Vibration Reduction Using an Attached Local Nonlinear Passive Absorber Based on a Clamped-Clamped Thin Blade
Authors: Bellizzi S. , Cochelin B. , Pinhede C.
Published: April 2014

The concept of nonlinear targeted energy transfer also named energy pumping can be used to passively reduce the vibrations of a primary system by attaching to it an essentially nonlinear damped oscillator also named Nonlinear Energy Sink (NES). In this paper, a thin blade clamped beam is considered as a NES device and studied experimentally. This NES configuration is an alternative way to design an essential stiffness nonlinearity. The behavior of the thin blade structure is first analyzed experimentally and numerically using a 1 DOF nonlinear oscillator. Next, experimental results are presented to demonstrate that the thin blade NES can efficiently reduce the vibrations of a flexible structure. The test set-up is composed of a primary system and the NES. The primary system is a steel beam clamped at one of its end and the NES is attached at the primary structure by its rigid base. Experimental results are discussed and also compared to simulated results obtained from a model.
Boiling Water Treatment for Wettability Improvement of Aluminum Fin Surfaces
Authors: Gao Jianlong , Zhao Jiheng , Chen Xinmiao , Xue Wei , Liu Liping
Published: April 2014

This work reports the effectiveness of a simple and rapid method for wettability improvement on aluminum surfaces – boiling water treatment. The wetting behavior and drainage performance on a series of aluminum surface samples after different lengths of boiling water treatment (3 minutes, 5 minutes, and 10 minutes) are examined. The data of contact angles for different sizes of droplets placed on these samples are reported with detailed surface roughness information from a 3D optical surface profiler. The contact angles are observed to decrease from the original value of 94.5° to approximately 10° after 10 minutes of treatment, and the reduction is correlated with the treatment length. Scanning electron microscopy (SEM) images and 3D optical profiler images suggest that the boiling water treatment facilitates oxidation of the sample surface and greatly alters the micro-structures on the surface, which are believed to be the two main reasons to change the droplet wetting behavior. The contact angle measurements are conducted again two days after the treatment and the hydrophilicity is retained.
Study of Turbulent Natural Convection in Vertical Storage Tubes for Supercritical Thermal Storage System
Authors: Lakeh Reza Baghaei , Kavehpour H. Pirouz , Lavine Adrienne S. , Ganapathi Gani B. , Wirz Richard E.
Published: April 2014

The effect of turbulent natural convection in vertical storage tubes containing a supercritical fluid is investigated computationally. In a supercritical thermal storage system, thermal energy is transferred to the storage fluid and is stored as the internal energy of the fluid in supercritical state. The heat is conducted from the heat transfer fluid to the storage fluid through the storage tube wall. Unlike phase-change systems, the heat transfer mechanism within the storage tubes of supercritical thermal storage system is dominantly affected by rigorous turbulent natural convection. The natural convection enhances the heat transfer and compensates for the low thermal conductivity of the storage fluid. The turbulent buoyancy-driven flow field in vertical storage tubes with different aspect ratios is investigated in this paper and the effect of vertical orientation of storage tubes on the characteristics of the flow field is explored. A standard k-epsilon method is utilized to model the Reynolds stresses in turbulent natural convection flow. The results of this study show that the turbulent buoyancy-driven flow and natural convection play an important role in charge and discharge of the supercritical thermal storage system. The charge time of the system is a function of Rayleigh number and aspect ratio of the storage tube.
Numerical Simulation of the Subcritical Flow Over a Circular Cylinder With “U” and “V” Grooves
Authors: Alonzo-García Alejandro , Gutiérrez-Torres Claudia del C. , Jiménez-Bernal José A. , Barbosa-Saldaña Juan G. , Mollinedo-Ponce de León Helvio R. , Martínez-Delgadillo Sergio A.
Published: April 2014

In this paper the comparative results of three numerical simulations of the subcritical turbulent flow over a circular cylinder (Re = 140,000) for the cases of a “U” grooved cylinder, a smooth cylinder, and a “V” grooved cylinder are presented. Due to the high resolution capabilities of the LES model, it was preferred over the RANS or URANS turbulence models. The simulation was carried out using the commercial CFD code ANSYS FLUENT V.12.0. The grid sizes were: 2.6 million cells for the smooth cylinder, and 14.5 and 13 million for the “U” grooved and “V” grooved cylinders respectively. In order to improve the quality of the solutions, the grids were structured and composed of hexahedral cells. Due to the requirements of the LES technique, the lower y+ values obtained were below 5. With the aim of capture the non-steady characteristics of this kind of flows, the simulations were performed over 8 vortex shedding cycles. Although the cross sections of the V and U grooves have almost the same shape, the resulting flow structures and calculated quantities such as the separation point, turbulent intensity in the normal and streamwise direction and recirculating bubble length were different for both cases. Apparently, the flow configuration resulted from the V grooves is similar to the smooth cylinder flow, being the U grooved cylinder flow different from both of them. This could be related to the drag reduction of about 27% obtained for the U grooved cylinder flow For the V grooved cylinder flow, the obtained drag presented an increase of about 7%.
Simple Expression for the Emittance of H2O-CO2 Mixtures in Zonal Methods of Radiation Transfer Modelling
Authors: Malikov German , Titaev Alexandr , Lisienko Vladimir , Viskanta Raymond
Published: April 2014

A new and simple expression for the calculation of the total gas emittance of H2O-CO2 mixtures for modeling radiation transfer in combustion furnaces is presented. Its accuracy is established by comparing the predictions with those based on the well established exponential wide band model. The computational time was found to be reduced by a factor of 10–30 in comparison to other methods for computing the total emittance of combustion gas mixtures.
Experimental Investigation on Dynamic Mechanical Behavior of the Elastic Ring Support With Metal Rubber
Authors: Ma Yanhong , Zhu Haixiong , Zhang Dayi , Hong Jie
Published: April 2014

A novel oil-free elastic damping support for rotor system is presented here which is combined of Elastic Ring (ER) and Metal Rubber (MR) named ERMR support for short. The ERMR support is an alternative of the traditional elastic damping support combined of squirrel cage and Squeeze Film Damper (SFD). The dynamic characteristics of the support were investigated and discussed, as well as the rotordynamic performances of the rotor system with the ERMR support.

Frequency sweeping experiments with different motion amplitudes were conducted to investigate the dynamic stiffness and damping properties of the support. Results show that both the structural stiffness and equivalent viscous damping of the support decrease significantly with the motion amplitude when the amplitude is smaller than 0.1mm, but tend to reach saturation values when the amplitude is larger. In a wide frequency range (0∼240Hz), the stiffness of the ERMR support shows gradual increasing trend with frequency, while the damping coefficient is approximately inversely proportional to frequency. The loss factor of the support displays nonmonotonic dependency on frequency and motion amplitude and distributes in 0.3–0.75.

Based on the experimental investigation on the dynamic properties of the support, the dynamic tests on the rotor system with an ERMR support were conducted to obtain the dynamic behavior of the system. Under different imbalance exciting forces, the synchronous vibration responses were captured and the mechanical parameters were calculated. The results show that the critical speed remains nearly unchanged with the increase of the imbalance. The stiffness of the rotor system doesn’t exhibit strong nonlinearity, which is quite different from the traditional SFD. In wide rotating speed range, the loss factor of the rotor system distributes in 0.1–0.3, validating the remarkable damping capacity of the ERMR support.
Personal Ventilation and Displacement Ventilation Assessment in Cubicle Workstations
Authors: Abdelmaksoud Waleed A. , Khalil Essam E.
Published: April 2014

Personal ventilation (PV) strategy is increasing very rapidly in ventilating the indoor spaces. Compared to the traditional ventilation system, the use of PV system can provide several advantages such as: energy reduction, comfort and healthy environment. Previous study reported in earlier paper [Schiavon et al. 2010] indicated that the use of PV system may reduce the energy consumption substantially (up to 51%) compared to mixing ventilation. Additionally, healthy environment is assured in the PV system due to the direct supply of fresh “clean” air to the occupant face. In the current study, detailed assessment of PV system and displacement ventilation (DV) system in a cubicle workstation (office cubicle) is presented. This assessment is based on CFD simulations. Five ventilation cases have been studied on the office cubicle. One case is performing a DV system only; another is performing a PV system only; the remaining three cases are performing a combined of PV and DV system. These cases have been evaluated using the PMV and PPD comfort indices, developed by Fanger 1970 and 1982. The target was to achieve a ventilation case that satisfies the best comfort indices near the occupant in the office cubicle. The five cases conditions and the best case conditions are presented in this paper.
Effect of Plume Dynamics for Heat Transfer Enhancement at Solid-Liquid Interface
Authors: Subudhi Sudhakar , Arakeri Jaywant H.
Published: April 2014

The present paper analyzes the effects of plumes for heat transfer enhancement at solid-liquid interface taking both smooth and grooved surfaces. The experimental setup consists of a tank of dimensions 265 × 265 × 300 (height) containing water. The bottom surface was heated and free surface of the water was left open to the ambient. In the experiments, the bottom plate had either a smooth surface or a grooved surface. We used 90° V-grooved rough surfaces with two groove heights, 10mm and 3mm. The experiment was done with water layer depths of 90mm and 140mm, corresponding to values of aspect ratio (AR) equal to 2.9 and 1.8 respectively. Thymol blue, a pH sensitive dye, was used to visualize the flow near the heated plate. The measured heat transfer coefficients over the grooved surfaces were higher compared that over the smooth surface. The enhanced heat transport in the rough cavities cannot be ascribed to the increase in the contact area, rather it must be the local dynamics of the thermal boundary layer that changes the heat transport over the rough surface.
Piezoelectric Synthetic Jet Integrated With Heat Sink for Heat Transfer Enhancement
Authors: Li Qiao , Huang Longzhong , Zhang Min , North Mark T. , Simon Terrence , Cui Tianhong
Published: April 2014

Synthetic jets, known as zero-net mass-flux (ZNMF) devices, have been widely used for cooling electronics. A synthetic jet is generally composed of a cavity with an orifice on one side and an oscillating diagram on the other side. The vibration of the diaphragm will generate a periodically impinging flow through the orifice which is found to be effective in enhancing heat transfer. The thermal performance of the synthetic jet is highly dependent on the peak velocity of the synthetic jet is able to generate. The orifice shape, orifice thickness, and the number of the orifices are the factors which affect the vibration condition of the diaphragm and thus to affect the performance of the synthetic jet. This study will use both experimental and computational methods to find out the optimal design of synthetic jet and how these factors affect synthetic jet performance. The synthetic jet arrays are driven by a piezoelectric stack actuator which is vibrating at around 720 Hz and the mean-to-peak amplitude is around 0.2 mm. The jet diaphragm (120 mm × 15 mm) is designed using a composite structure composed of a carbon fiber beam, a carbon fiber frame, and a jet frame fabricated by polymethyl methacrylate (PMMA). Four different orifice shapes (square, single slot, double slot, and triangle) with the same area have been designed and the square orifice has the highest velocity. The effect of the orifice thickness is also studied by testing four kinds of PMMA films with different thicknesses (1.5 mm, 2 mm, 3 mm, and 4.5 mm) and the case with 4.5 mm thick orifice has the best performance. The numerical simulation is conducted using the CFD software ANSYS Fluent to support the experimental results. The vibrating of the diaphragm is defined as a moving wall using a user defined function. The fluid power consumed by the diaphragm is used to determine the performances of different designs. The same trend with orifice thickness has been found and the reason has been demonstrated.
Soot Load Sensing in a Diesel Particulate Filter via Electrical Capacitance Tomography
Authors: Huq Ragibul , Anwar Sohel
Published: April 2014

Diesel engines are widely used in heavy duty trucks and off road vehicles due to their fuel efficiency and high power outputs. Environmental regulatory agencies have pushed ever stringent regulations on all internal combustion engines, including Diesel engines on gaseous as well as particulates (soot) emissions. In order to meet today’s and tomorrow’s stringent emission requirements, modern diesel engines are equipped with diesel particulate filters (DPF’s), as well as on-board technologies to evaluate the status of DPF. In course of time, particulate matter (soot) will be deposited inside the DPFs which tend to clog the filter and hence generate a back pressure in the exhaust system, negatively impacting the fuel efficiency. To remove the soot build-up, regeneration (active or passive) of the DPF must be done as an engine exhaust after treatment process at pre-determined time intervals. Since the regeneration process consume fuel, a robust and efficient operation based on accurate knowledge of the particulate matter deposit (or soot load) becomes essential in order to keep the fuel consumption at a minimum. In this paper, we propose a sensing method for a DPF that can accurately measure in-situ soot load using Electrical Capacitance Tomography (ECT). Simulation results show that the proposed method offers an effective way to accurately estimate the soot load in DPF. The proposed method is expected to have a profound impact in improving overall PM filtering efficiency (and thereby fuel efficiency), and durability of a Diesel Particulate Filter (DPF) through appropriate closed loop regeneration operation.
Developing a Baseline Strategy for Controlling Blinds in Buildings
Authors: Karizi Nasim , Reddy T. Agami , Dasgupta Partha
Published: April 2014

Automated day-lighting systems can modulate window blinds and electrical lights for maintaining the proper illumination levels and save significant electrical energy in buildings. This paper presents an initial work toward developing an automated installation and maintenance of a generic daylighting system which is able to self-calibrate and adapt to the building needs with minimal human intervention. The system operates based on information provided by a wireless sensor network, and processed through learning algorithms and feedback control principle.

This paper focuses on a preliminary simulation study to establish a control baseline and identifies the required elements. It demonstrates the concept, using daylighting simulation software in the context of a test cell which represents a virtual office space. A startup baseline for the optimal blind slat angle settings for the windows is developed with the objective of maintaining uniform lighting levels on a horizontal surface inside the test cell. The lighting baseline simulations are limited to specific times and days of a year to reduce and optimize the simulation process and are applied to predict the optimal blind slat angles for other days of the year. This paper presents and discusses the results of such an analysis including an extrapolation to all year round.
Integrated Computer-Aided Approach for Supporting Development of Biomedical Devices
Authors: El-Gizawy Ahmed Sherif
Published: April 2014

Both medicine and engineering disciplines use problem-solving techniques to address different needs. The solutions often require an understanding of complex system behavior, identification of important system factors, and prediction of the outcome prior to application. This paper presents an introduction to integrated computer-aided approach to support developments in the field of biomedical devices, particularly for those used with orthopaedic surgery applications. The modern design process is first introduced as a road map to establish design that is robust, cost and time effective in order to satisfy the needs of the medical community. The coverage includes methods such as: function abstraction and decomposition, quality function deployment (QFD), case-based design (CBD) methodology, and risk management in design of orthopedic implants.