bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Emission Tests in the Monitoring of Cavitation Erosion in Hydraulic Turbines
Authors: Faria Marco Tulio C. , Queiroz Fernando R. , Medeiros Eduardo B. , Martinez Carlos B.
Published: April 2014

This work presents an experimental study about the application of acoustic emission (AE) techniques in the monitoring of cavitation erosion mass loss in small Francis turbines. A vertical Francis turbine test bench is specially devised to perform some experiments designed to evaluate the influence of small surface mass losses on turbine blades in the acoustic emission signals. An AE wideband transducer is employed in the test bench instrumentation system. In order to evaluate the AE levels associated with the turbine erosion stages, a small defect is introduced into the turbine runner. This defect is intended to simulate a small mass loss in the turbine runner. The measurements of the AE signals are performed in the Turbine Francis model at two situations: 1) turbine without defect, which means that the runner blades are free of apparent geometric imperfections; 2) turbine with defect, which is represented by a small hole drilled into a runner blade. The AE transducer is installed on the turbine draft tube and the AE measurements are performed at several operating conditions. The preliminary results obtained for the AE amplitude in this investigation show that the small defect introduced into a runner blade causes variations in the AE levels measured in the experiments, confirming that there is a large potential for the application of AE monitoring techniques in the accurate evaluation of cavitation wear on hydraulic turbines in field.
Thermostructural Design of the HyProb Methane Cooling Channel Breadboard
Authors: Ferraiuolo M. , Martucci A.
Published: April 2014

In the frame of the HYPROB/Bread project, whose main goal is to design build and test a 30 kN regeneratively cooled thrust chamber, a breadboard has been conceived in order to evaluate the thermal properties of methane in supercritical conditions. The breadboard is called MTP (Methane Thermal Properties) and it is made of Glidcop Al 15. The heating process of the breadboard is obtained by means of Nickel-Chrome wire wrapped cartridges. The methane flows through a rectangular cross section with a mass flow rate of 20 g/s. The aim of the present paper is to illustrate the thermo-structural design conducted on the breadboard by means of a Finite Element Method code taking into account the viscoplastic behaviour of Glidcop Al 15. An optimization process has been carried out in order to keep the structural integrity of the breadboard maximizing the life cycles of the component.
Fibroblast Behavior on Electrospun PMMAEA and PMMAEA-Collagen Nanofibers
Authors: Hu Wen , Holy Jon , Yu Xun
Published: April 2014

The influence of different physical forms of substrates on fibroblast behavior was examined by comparing the following experimental and control groups: 1) glass coverslips, 2) poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA) cast films, 3) electrospun PMMAEA nanofibers, 4) electrospun PMMAEA/collagen nanofibers, and 5) electrospun collagen. Cell adhesion, spreading and proliferation were compared on the different substrates. It was observed that fibroblasts on electrospun PMMAEA, PMMAEA-collagen, and collagen substrates spread more slowly after plating, and did not spread out to the extent observed for glass or PMMAEA films. Cells on electrospun fibers exhibited more filopodial-like structures and fewer stress fibers than the glass and PMMAEA film surfaces. Cell viability studies showed that although cells remained viable on all substrates, proliferation was faster on glass and PMMAEA films than on electrospun substrates. Overall, fibroblast behavior appeared to more closely resemble in vivo behavior on the electrospun nanofibers than on films or glass substrates.
Wind Energy Conversion: The Potential of a Novel Ducted Turbine for Residential and Commercial Applications
Authors: Goudarzi N. , Zhu W. D. , Bahari H.
Published: April 2014

A novel ducted turbine, referred to as a Wind Tower, for capturing wind power in either residential or commercial scale applications is studied theoretically and experimentally. A mathematical model is developed to predict the flow behavior inside the tower and a velocity coefficient is defined to correct the results at different test conditions. A wind tower prototype, including a four-quadrant-peak wind-catcher rooftop, a tower, a nozzle, and a turbine, is designed and fabricated. The captured wind power values from the mathematical model and the preliminary experimental tests are compared. While the mathematical model provides a good estimation of the output power in some cases, more precise experimental tests and simulation techniques are required to improve the mathematical model in some other cases. Significant changes in the output wind speed due to pressure differences created by the surrounding environment, the tower height, and the number of nozzles are observed. The advantages of being maintenance free, reliable, and sustainable, together with its special design that eliminates bird/bat mortality make the Wind Tower a promising solution for residential, commercial, and even off-grid applications.
Numerical Study of Head/Helmet Interaction due to Blast Loading
Authors: Zhang Timothy G. , Satapathy Sikhanda S. , Dagro Amy M. , McKee Philip J.
Published: April 2014

Recent wars have heightened the need to better protect dismounted soldiers against emerging blast and ballistic threats. Traumatic Brain Injury (TBI) due to blast and ballistic loading has been a subject of many recent studies. In this paper, we report a numerical study to understand the effects of load transmitted through a combat helmet and pad system to the head and eventually to the brain during a blast event. The ALE module in LS-DYNA was used to model the interactions between fluid (air) and the structure (helmet/head assembly). The geometry model for the head was generated from the MRI scan of a human head. For computational simplicity, four major components of the head are modeled: skin, bone, cerebrospinal fluid (CSF) and brain. A spherical shape blast wave was generated by using a spherical shell air zone surrounding the helmet/head structure. A numerical evaluation of boundary conditions and numerical algorithm to capture the wave transmission was carried out first in a simpler geometry. The ConWep function was used to apply blast pressure to the 3D model. The blast pressure amplitude was found to reduce as it propagated through the foam pads, indicating the latter’s utility in mitigating blast effects. It is also shown that the blast loads are only partially transmitted to the head. In the calculation where foam pads were not used, the pressure in the skin was found to be higher due to the underwash effect in the gap between the helmet and skin, which amplified the blast pressure.
Studying the Potential of a Novel Multiple-Generator Drivetrain in Wind Energy Conversion Systems
Authors: Goudarzi N. , Zhu W. D.
Published: April 2014

A novel multiple generator drivetrain (MGD), where a single large generator in a wind turbine is replaced by multiple generators with the same or different rated powers, is proposed along with an automatic switch mechanism as an alternative to an existing MGD. To better understand the advantages and disadvantages of having a MGD in onshore/offshore wind turbines, a MGD with a single or double stage gearbox and multiple generators is compared with a conventional drivetrain with a triple-stage gearbox and a large induction generator. A simple mathematical model for a MGD with an automatic switch is developed, a novel prototype of a MGD is designed and fabricated, and experiments are conducted on the prototype. It is concluded that a multiple-generator drivetrain with generators operating individually or in parallel through an automatic switch mechanism has a better potential of improving the efficiency and the reliability, expanding the operational range, and reducing the cost of offshore and onshore wind turbines than the existing MGD configuration.
Non-Contact Ultrasonic Guided Wave Inspection of Rails
Authors: Nguyen Thompson V. , Mariani Stefano , Phillips Robert R. , Kijanka Piotr , Lanza di Scalea Francesco , Staszewski Wieslaw J.
Published: April 2014

The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is developing a system for high-speed and non-contact rail integrity evaluation. A prototype using an ultrasonic air-coupled guided wave signal generation and air-coupled signal detection, in pair with a real-time statistical analysis algorithm, is being developed. This solution presents an improvement over the previously considered laser/air-coupled hybrid system because it replaces the costly and hard-to-maintain laser with a much cheaper, faster, and easier-to-maintain air-coupled transmitter. This system requires a specialized filtering approach due to the inherently poor signal-to-noise ratio of the air-coupled ultrasonic measurements in rail steel. Various aspects of the prototype have been designed with the aid of numerical analyses. In particular, simulations of ultrasonic guided wave propagation in rails have been performed using a Local Interaction Simulation Approach (LISA) algorithm. Many of the system operating parameters were selected based on Receiver Operating Characteristic (ROC) curves, which provide a quantitative manner to evaluate different detection performances based on the trade-off between detection rate and false positive rate. Experimental tests have been carried out at the UCSD Rail Defect Farm. The laboratory results indicate that the prototype is able to detect internal rail defects with a high reliability. A field test will be planned later in the year to further validate these results. Extensions of the system are planned to add rail surface characterization to the internal rail defect detection.
Application of Crack Layer in Modeling of Slow Crack Growth in High-Density Polyethylene
Authors: Zhang Haiying , Zhou Zhenwen , Chudnovsky Alexander
Published: April 2014

Crack layer model provides a comprehensive foundation for modeling of fracture growth, failure analysis, and lifetime prediction. During the past two decades, it has been widely applied for modeling various aspects of brittle fracture in general. This paper illustrates in details the procedure of implementation by an example of slow crack growth in a commercialized high-density polyethylene undergoing creep conditions. Firstly, we determine experimentally the basic parameters employed in constitutive equations of crack layer model such as draw ratio λ, the specific energy of transformation γtr, and drawing stress σdr, etc.. Secondly, we implement crack layer model numerically in lab-developed “Simulator”. The paper provides a paradigm for implementation of crack layer model in slow crack growth, and a blueprint for potential software development that can be used in ranking and the lifetime assessment of a large set of engineering polymers.
The Drift Flux Model After Fifty Years: A Personal, Problem Solving Survey
Authors: Toma Peter
Published: April 2014

Offspring of the nuclear reactor industry and gas-oil production, multiphase fluids handling technology appears to have matured into an entirely new field of inquiry, most notably following broad acceptance of the drift flux and flow pattern concepts and their widespread integration into engineering calculations.

The drift flux model (DFM), first suggested by Nicklin in 1962 and, soon after, adapted and developed by Professor Zuber’s research group at General Electric, enables calculation of “locally averaged” phase velocity. Further progress made in selection of the flow patterns, calculated for each section of the pipe, provided the key to properly assessing the terminal velocity of the discrete phase and the local phase distributions.

The flow pattern concept was first introduced by Canadian Charles Govier to describe oil-water laboratory experiments, then by Hewitt-Roberts and Baker in 1954. A decade later, the team of Dukler-Taitel-Barnea developed the qualitative flow pattern concept into a quantitative roadmap procedure leading to rational calculations of the local (cross-section averaged) gas-liquid flow geometry, or flow pattern. The homogeneous gas-liquid flow, presuming the equality of gas and liquid velocities, a simplification broadly accepted during the early days of two-phase flow engineering, came to be regarded, due to Hinze’s work (Shell, 1955), as an identifiable region in the local flow map, reflecting turbulent and high-shear breakup of the discrete phase.

To illustrate the usefulness, validity, and importance of the DFM, and mechanistic modeling using the DFM, as well as the salient work of Prof. Zuber on boiling instability this paper discuses reduction of potential explosive droplet boiling risk during multiphase pumping of high–gas-oil ratio mixtures.

To assess critical operating conditions of the multiphase pumps, the Ishi-Zuber criteria developed during 1970 for assessing potential boiling instabilities were adapted to multiphase pumping/compression equipment and the results compared to field instability data.

The elucidation of this problem relies heavily on the DFM and on salient research performed during 70s by Prof. Zuber’s team.
Experimental Study on the Internal Separated and Inverse Flow Between the Blades
Authors: Furuta Hiroki , Terashima Osamu , Sakai Yasuhiko , Nagata Kouji , Ishiguro Shunsuke , Sakai Masaharu , Ito Yasumasa
Published: April 2014

The objective of this study is to investigate an internal separated flow between the blades of turbo machinery. Flow separation often causes undesirable phenomena such as an increase of the total pressure loss and a vibration of the machine. Therefore, understanding the characteristics of the separated flow in detail is very important for optimizing the machine to decrease the energy loss.

In general, the separated flow involves a reverse flow near the solid wall in the separation bubble and its reattachment of the further downstream location. Hence, a typical hot-wire sensor is not useful for measuring the internal separated flow between the blades because it can detect only the magnitude of the flow velocity, not the flow direction.

Based on this background, a self-developed tandem-type hot-wire sensor, by which both the magnitude and the flow direction can be detected, is used to measure the velocity field between the blades in this study. The tandem-type hot-wire sensor consists of two I-type hot-wire sensors and a small insulated elliptical cylinder placed between them. A calibration test is first conducted to validate its performance.

Subsequently, the separated flow between the blades is measured with the tandem-type hot-wire sensor. The experimental apparatus consists of a closed-type test section which is connected to the nozzle exit of a blowout-type wind tunnel. In this test section, a sample of blade is set up. In this study, experiments are conducted with three kinds of blades with the different shapes (i.e., experiments are performed under three different conditions): a constant blade thickness from the leading edge to the trailing edge (Blade 1), a constant blade thickness from the leading edge to trailing edge but a rounded leading edge (Blade 2) and a thin blade thickness at the leading and trailing edges (Blade 3).

In addition, the unsteady internal separated flow between the blades is also investigated by large-eddy simulation (LES) whose validity was fully confirmed in the previous study. The flow field and dissipation rate of the turbulent kinetic energy obtained by the simulation are discussed.

Experimental and numerical results show that Blade 3 has a smallest separation bubble around the leading edge than that of Blade 1 and 2, and shows a smallest root mean square (RMS) value for the velocity fluctuation near the reattachment point than them. These differences of the size of separation bubble and velocity fluctuation were considered to be resulted in a decrease of the kinetic energy loss in the test section with Blade 3. Therefore, it can be concluded that the non-uniform thickness of the blade causes the decrease of the energy loss around the blade.
A Comparative Study of Mechanical Properties of Tooth Reconstruction Materials
Authors: Chun Keyoung Jin , Choi Hyun Ho , Lee Jong Yeop
Published: April 2014

Tooth reconstruction materials are used to reconstruct damaged teeth as well as to recover their functions. In this study, the mechanical properties of various tooth reconstruction materials were determined using test specimens of identical shape and dimension under the same compressive test condition; the hardness values of them were obtained from previous studies and compared with those of enamel and dentin.

Amalgam, dental ceramic, dental gold alloy, dental resin, zirconia and titanium were processed as tooth reconstruction material specimens. For each material, 10 specimens having a of 3.0 × 1.2 × 1.2 mm (length × width × height) were used.

The stresses, strains, and elastic moduli of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were obtained from the compressive test. The hardness values of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were obtained from the references [14–19].

And, the stresses, strains, elastic moduli, and the hardness values of enamel and dentin were obtained from the reference [13].

The mechanical role of enamel is to crush food and protect dentin because of its higher wear resistance, and that of dentin is to absorb bite forces because of its higher force resistance. Therefore, the hardness value should be prioritized for enamel replacement materials, and mechanical properties should be prioritized for dentin replacement materials. Therefore, zirconia and titanium alloy were considered suitable tooth reconstruction materials for replacing enamel, and gold alloy, zirconia, and titanium alloy were considered suitable tooth reconstruction materials for replacing dentin. However, owing to the excessive mechanical properties and hardness values of zirconia and titanium alloy, these may show poor biocompatibility with natural teeth.

Thus far, no tooth reconstruction material satisfies the requirements of having both a hardness value similar to that of enamel and mechanical properties similar to those of dentin.
Preliminary Analysis of SGTR Accident for an Integral Effect Test Facility, SMART-ITL
Authors: Kim H. K. , Chung Y. J. , Kim S. H. , Kim H. S.
Published: April 2014

SMART-ITL (system-integrated modular advanced reactor-integral test loop) has been built at Korea Atomic Energy Research Institute (KAERI) in order to validate the safety and performance of SMART. It is an integral effect test facility and its scale is 1/1 in height and 1/49 in volume with respect to SMART plant. The objectives of SMART-ITL are to investigate and understand the integral performance of reactor systems and components and the thermal-hydraulic phenomena occurred in the system during normal, abnormal and emergency conditions, and to verify the system safety during various design basis events of SMART. The integral-effect test data will also be used to validate the related thermal-hydraulic models of the safety analysis code such as TASS/SMR-S, which is used for performance and accident analysis of SMART design.

SMART with a rated thermal power of 330 MWt has been developed at KAERI. SMART is an integral type pressurized water reactor with a mixture of the proven technologies and advanced design features. The enhancement of safety is realized by incorporating inherent safety features and passive safety systems. The licensing has been approved by the Korean nuclear regulatory authority in 2012. TASS/SMR-S code can analyze thermal hydraulic phenomena of SMART in a full range of reactor operating and accident conditions. A steam generator tube rupture (SGTR) accident is one of the safety related design basis events and should be analyzed with thermal hydraulic and radiological viewpoint. A preliminary analysis of an SGTR accident for SMART-ITL was performed using TASS/SMR-S code to setup test procedure.

The thermal-hydraulic analysis for SMART-ITL SGTR accident with the geometrical, thermal-hydraulic parameters and modeling information was performed. The major concern of this analysis was to find the thermal-hydraulic phenomena and maximum leakage amount from a primary to a secondary side caused by an SGTR accident. The result was also compared with the result of SMART SGTR accident analysis. In spite of the different assumptions and scaling, the compared results are reasonable. The characteristics of SMART SGTR accident are well reflected on SMART-ITL. The analysis result of preliminary SMART-ITL SGTR accident estimates the major effects of SMART SGTR accident successfully.
Three-Dimensional Holographic Microwave Imaging Array: Experimental Investigation of Tumour Detection in Breast Phantom
Authors: Wang Lulu , Simpkin Ray , Al-Jumaily A. M.
Published: April 2014

This paper extends our previously presented two-dimensional (2-D) Holographic Microwave Imaging Array (HMIA) system for early breast tumour detection to three-dimensional (3-D) imaging, and demonstrates its efficacy using experimental data obtained with a breast phantom. This work describes an experimental setup to collect data to form a 3-D breast image. The obtained experimental result proves that the 3-D HMIA system has potential to become a screening and diagnostic tool that could supplement clinical breast examination through its sensitivity, quantitative record storage, ease-of-use, and inherent low cost.
Numerical Modelling of Electrode Geometry Effects on a 2D Self-Field MPD Thruster
Authors: Xisto Carlos M. , Páscoa José C. , Oliveira Paulo J.
Published: April 2014

A self-field MPD thruster in its most basic form consists in a central cathode surrounded by a concentric anode. With this coaxial geometric shape is very difficult to use experimental techniques to visualize the plasma flow parameters. In the following paper a previously proposed numerical method for the ideal magnetohydrodynamics (MHD) equations is extended to deal with resistive MHD viscous flow. The numerical method is based on the well known PISO algorithm and makes use of the AUSM-MHD scheme for flux calculation. For validation three test cases will be addressed. We start with a resistive MHD problem, namely the Shercliff test case. The second and third test cases are standard 2D ideal MHD problems, these will be used to validate our method for complex interaction of MHD shocks. We will close this paper with some preliminary results for a quasi-bi-dimensional self-field magnetoplasmadynamic (MPD) thruster, where the effects of cathode length in the performance of the nozzle are analysed.
FMM/GPU Accelerated BEM Simulations of Emulsion Flow in Microchannels
Authors: Abramova Olga A. , Itkulova Yulia A. , Gumerov Nail A.
Published: April 2014

Modeling of motion of two-phase liquids in microchannels of different shape is needed for a variety of industrial applications, such as enhanced oil recovery, advanced material processing, and biotechnology. Development of efficient computational techniques is required for understanding the mechanisms of many effects in “liquid-liquid” systems, such as the jamming of emulsion flows in microchannels and blood cell motion in capillaries. In the present study, a mathematical model of a three-dimensional flow of a mixture of two Newtonian liquids of a droplet structure in microchannels at low Reynold’s numbers is considered. The computational approach is based on the boundary element method accelerated both via an advanced scalable algorithm (FMM), and via utilization of a heterogeneous computing architecture (multicore CPUs and graphics processors). To solve large scale problems flexible GMRES solver is developed. Example computations are conducted for dynamics of many deformable drops of different sizes in microchannels. The results of simulations and accuracy/performance of the method are discussed. The developed approach can be used for solution of a wide range of problems related to emulsion flows in micro- and nanoscales.
Boundary Element Simulations of Compressible Bubble Dynamics in Stokes Flows
Authors: Itkulova Yulia A. , Abramova Olga A. , Gumerov Nail A.
Published: April 2014

Modeling of dynamics of compressible bubbles in acoustic fields at low Reynolds numbers is of interest for a number of contemporary micro- and nanotechnologies. Despite the boundary element method (BEM) is an appropriate method to simulate deformation of three-dimensional bubbles computation of compressible bubbles dynamics using conventional BEM causes difficulties due to degeneration of the resulting system of equations. In the present approach additional relations based on the Lorentz reciprocity principle are used to resolve the problem. The approach is validated by test simulations of dynamics of single bubbles and bubble clusters including strong bubble-bubble interaction in acoustic fields and shear flows.
Load Dynamic Analysis of Upper and Lower Arm Automotive Suspension
Authors: Bouazara M. , Saihi M. , Richard M. J.
Published: April 2014

To reduce weight, in last decade the transport industry had recourse to the use of more lightweight material. Currently, several static elements of the vehicles are made of aluminum. However, the dynamic elements such as suspension parts cause difficulties due to high solicitations from vibration and road roughness. To better assess this damage in depth, the modeling of a full suspension system is more than necessary. In this work, a full quarter vehicle model while considering the motion of suspension along three axes is developed. This system is composed of an upper arm, lower arm, the spring, the damper, the wheel and the fastening elements. By using this full analytical model, all parameters such as, velocities, accelerations and forces can be determined.
Tissue- and Cell-Level Stress Distributions of the Heart Valve Tissue During Diastole
Authors: Huang Siyao , Huang Hsiao-Ying Shadow
Published: April 2014

Heart valves are inhomogeneous microstructure with nonlinear anisotropic properties and constantly experience different stress states during cardiac cycles. However, how tissue-level mechanical forces can translate into altered cellular stress states remains unclear, and associated biomechanical regulation in the tissue has not been fully understood. In the current study, we use an image-based finite element method to investigate factors contributing the stress distributions at both tissue- and cell-levels inside the healthy heart valve tissues. Effects of tissue microstructure, inhomogeneity, and anisotropic material property at different diastole states are discussed to provide a better understanding of structure-mechanics-property interactions, which alters tissue-to-cell stress transfer mechanisms in heart valve tissue. To the best of the authors’ knowledge, this is the first study reporting on the evolution of stress fields at both the tissue- and cellular-levels in valvular tissue, and thus contributes toward refining our collective understanding of valvular tissue micromechanics while providing a computational tool enabling further study of valvular cell-tissue interactions.
A Numerical Analysis of Pre-Deployment Effect of Side-Impact Airbags in Reducing Occupant Injuries
Authors: Tay Yi Yang , Moradi Rasoul , Lankarani Hamid M.
Published: April 2014

Side impact collisions represent the second greatest cause of fatality in motor vehicle accidents. Side-impact airbags (SABs), though not mandated by NHTSA, have been installed in recent model year vehicle due to its effectiveness in reducing passengers’ injuries and fatality rates. However, the increase in number of frontal and side airbags installed in modern vehicles has concomitantly led to the rise of airbag related injuries. A typical side-impact mechanical or electronic sensor require much higher sensitivity due to the limited crush zones making SABs deployment more lethal to out-of-position passengers and children. Appropriate pre-crash sensing needs to be utilized in order to properly restraint passengers and reduce passengers’ injuries in a vehicle collision. A typical passenger vehicle utilizes sensors to activate airbag deployment when certain crush displacement, velocity and or acceleration threshold are met. In this study, it is assumed that an ideal pre-crash sensing system such as a combination of proximity and velocity and acceleration sensors is used to govern the SAB pre-deployment algorithm. The main focus of this paper is to provide a numerical analysis of the benefit of pre-deploying SAB in lateral crashes in reducing occupant injuries. The effectiveness of SABs at low and high speed side-impact collisions are examined using numerical Anthropomorphic Test Dummy (ATD) model. Finite Element Analysis (FEA) is primarily used to evaluate this concept. Velocities ranging from 33.5mph to 50mph are used in the FEA simulations. The ATD used in this test is the ES-2re 50th percentile side-impact dummy (SID). Crucial injury criteria such as Head Injury Criteria (HIC), Thoracic Trauma Index (TTI), and thorax deflection are computed for the ATD and compared against those from a typical airbag system without pre-crash sensing. It is shown that the pre-deployment of SABs has the potential of reducing airbag parameters such as deployment velocity and rise rate that will directly contribute to reducing airbag related injuries.
Transient Behavior of the Gallium Nitride Chemical Vapor Deposition Process
Authors: Meng Jiandong , Jaluria Yogesh
Published: April 2014

The transient behavior of the Gallium Nitride deposition process in a CVD reactor is numerically investigated. A two-dimensional impinging reactor is considered to examine the time-dependent transport in the MOCVD process, including the steady-state deposition process, and the system start-up and shut-down. The study involves the consideration of complicated transport phenomena, including fluid flow, heat and mass transfer, and chemical reactions between the reactants and the intermediate species. The temperature field and the deposition rate are studied as functions of time, as well as the precursor mass fraction at certain times. The results obtained provide an in-depth understanding about the entire MOCVD process, and the possibility to control the system operating time and the consumption of input power and precursors, which are generally quite expensive. It also provided inputs on the effects of changing operating conditions and the duration of starting and shut down effects.
Numerical Investigation of Oil Slug Trapped in Capillary Tube With a Level Set Method
Authors: Dai Liming , Wang Xiaojie
Published: April 2014

An investigation of the motion of oil drops trapped in an axisymmetric capillary tube saturated with water is carried out. The governing equations for core-annular flow are derived in detail. Numerical solutions for capturing the evolution of interface are developed by making use of a level set method. A second-order projection method is applied to obtain the velocity field of the incompressible two-phase flow. The results show the high efficiency of the method and the key role of water film in improving the mobilization of oil slugs.
Comparison and Evaluation of Performance, Emission and Wear Analysis of Diesel, JP-8 and Pure Karanja Biodiesel in a Military 780 hp CIDI Engine
Authors: Pandey Anand Kumar , Nandgaonkar M. R. , Sivakumar P. , Kammanni Veerabhadrappa Anand Kumar , Kumarasamy A.
Published: April 2014

Investigating the impact of JP-8 and pure Karanja oil biodiesel fuel on diesel engine performance, emission and pump wear are very important for military track and wheeled vehicles due to their great potential as alternative fuels. In the present study, a military 780 hp CIDI engine was fuelled and tested with diesel, JP-8 and pure Karanja oil biodiesel respectively. The performances of fuels were evaluated in terms of brake horse power, specific fuel consumption, brake specific energy consumption, brake mean effective pressure, thermal efficiency and heat release rates. The emission of carbon monoxide (CO), unburnt hydrocarbon (UHC), and oxides of nitrogen NOx with the three fuels were also compared. Both Karanja oil, after transesterification and JP-8 exhibit the properties (density, viscosity and calorific value) within acceptable limits of ASTM standard. Performance of both JP-8 and pure Karanja oil biodiesel were slightly lower than diesel. Emissions of CO and UHC were found lower with both JP-8 and Karanja oil biodiesel as compared to diesel fuel. However, only JP-8 fuel had lower NOx emission whereas Karanja oil biodiesel had 10% higher NOx emission. The fuel pump wear was tested after a 100 hours run.
The Game Theory Approach for Solving the Hierarchical and Decentralized Bi-Level Problem
Authors: Ghotbi Ehsan , Dhingra Anoop K.
Published: April 2014

This paper presents a game theory approach to solve two types op problem, hierarchical and decentralized bi-level multi-objective problem with multiple objective functions at the upper level and multiple players at the lower level. The sensitivity based approach is applied for numerical approach. A sensitivity based algorithm is proposed to the Hierarchical and decentralized bi-level multi-objective problem. Two scenarios are studied in this paper for modeling the decentralized bi-level multi-objective problem. The first scenario considers the cooperative game as interaction between the players at upper level and the lower level individually. The interaction between the upper and lower level is considered as Stackelberg. On the second scenario, the interaction in the lower level is modeled by Nash game. The sensitivity based method has been used to provide an approximation to the rational reaction set (RRS) for each player. An alternate approach for generating the RRS based on design of experiments (DOE) combined with response surface methodology (RSM) is also explored. Two numerical examples are given to demonstrate the proposed algorithm for the both scenario. It is seen that the proposed sensitivity based approach is able to approximate non linear RRS. For the hierarchical approach, one numerical example is studied to show the application of the algorithm.
Periodicities Changes of Nonlinear Oscillatory Behavior of a Fluttering Plate With Periodicity Ratio and Periodicity Change Rate
Authors: Dai Liming , Han Lu
Published: April 2014

This study focuses on diagnosing the periodicity change of nonlinear dynamic responses of a fluttering plate excited by high-velocity air flow. The number and changing multiple-periodicities of the system with the implementation of Periodicity Ratio (PR) are investigated. The multiple-periodicity diagram is generated such that the periodicities and nonlinearity of the systems with respect to the system parameters can be graphically studied.

The results of the research show that the number of period of periodicity of the systems increases when certain system parameters increase. Transitional characteristics of the systems are also investigated with Periodicity Change Rate as well.
Benchmarking the Accuracy of Inertial Measurement Units for Estimating Kinetic Energy
Authors: Hough Jessandra , McGinnis Ryan S. , Perkins N. C.
Published: April 2014

The energetics of human motion has been intensely studied using experimental and theoretical methods. Knowing the kinetic energy of the human body, and its decomposition into the kinetic energies of the major body segments, has tremendous value in applications ranging from physical therapy, athlete training, soldier performance, worker health and safety, among other uses. Significant challenges thwart our ability to measure segmental kinetic energy in real (non-laboratory) environments such as in the home or workplace, or on the playing/training field. The aim of this research is to address these challenges by advancing the use of an array of miniaturized body-worn inertial measurement units (IMUs) for estimating segmental kinetic energy. As a step towards this goal, this study reports a benchmark experiment that demonstrates the accuracy of IMU-derived estimates of segmental kinetic energy. The study is conducted on a well-characterized mechanical system, a double pendulum that also serves as an apt model for the lower or upper extremities. A two-node IMU array is used to measure the kinematics of each segment as input to the segmental kinetic energy computations. The segments are also instrumented with two high-precision optical encoders that provide the truth data for kinetic energy. The segmental kinetic energies estimated using the IMU array remain within 3.5% and 3.9% of the kinetic energies measured by the optical encoders for the top and bottom segments, respectively, for the freely decaying pendulum oscillations considered. These promising results support the future development of body-worn IMU arrays for real-time estimates of segmental kinetic energy for health, sports and military applications.
Resilient Design of Complex Engineered Systems Against Cascading Failure
Authors: Mehrpouyan Hoda , Haley Brandon , Dong Andy , Tumer Irem Y. , Hoyle Chris
Published: April 2014

This paper describes an approach commonly used with complex networks to study the failure propagation in an engineered system design. The goal of the research is to synthesize and illustrate system design characteristics that results from possible impact of the underlying design methodology based on cascading failures. Further, identifying the most vulnerable component in the design or system design architectures that are resilient to such dissemination of failures provide additional property improvement for resilient design. The paper presents a case study based on the ADAPT (Electrical Power System) EPS testbed at NASA Ames as a subsystem for the Ramp System of an Infantry Fighting Vehicle (IFV). A popular methodology based on the adjacency matrix, which is commonly used to represent edge connections between nodes in complex networks, has inspired interest in the use of similar methods to represent complex engineered systems. This is made possible, by defining the connections between components as a flow of energy, signal, and material and constraining physical connection between compatible components within complex engineered systems. Non-linear dynamical system (NLDS) and epidemic spreading models are used to compare the failure propagation mean time transformation. The results show that coupling, modularity, and module complexity all play an important part in the design of robust large complex engineered systems.
Temperature Dependent Viscoelastic Behavior of FRP/ZnO Nano-Rods Hybrid Nanocomposites
Authors: Skandani Amir Alipour , Boroujeni Ayoub Yari , Al-Haik Marwan
Published: April 2014

The inclusion of nanomaterials within fiber reinforced plastics (FRPs) could improve their resistance against time dependent deformation. Conceivable high temperature applications of such hybrid composites make it crucial to investigate their temperature-dependent properties as well as their durability. In this study, zinc oxide (ZnO) nano rods were grown on the surface of carbon fibers and the hybridized reinforcement was formed in a laminate composites. The viscoelastic behavior was probed utilizing dynamic mechanical analysis (DMA). The time/temperature superposition principle (TTSP) was invoked to obtain the viscoelastic properties of FRPs based on fibers with different surface treatments. Results indicated that the presence of ZnO nano rods at the interface between the carbon fibers and the epoxy matrix enhances the composite’s creep resistance at elevated temperatures and prolonged duration.
Robust Visual PID Control of Planar Parallel Robots Under Constant Disturbances
Authors: Trujano Miguel A. , Garrido Ruben
Published: April 2014

This work presents an image-based visual servoing scheme applied to planar parallel robots. A PID algorithm regulates the robot end-effector position, and rejects constant disturbances perturbing the active robot joints. Instead using the La Salle invariance theorem, the stability analysis provided here relies on a strict Lyapunov function. Experiments on a redundant planar parallel robot validate the proposed control scheme.
Interaction Between the Magnetic Polariton and Surface Plasmon Polariton
Authors: Chen Yu-Bin , Chen Chien-Jing
Published: April 2014

This work numerically investigated the interaction between two resonances: the magnetic polariton (MP) and surface plasmon polariton (SPP). A reflectance contour plot of deep silver slit arrays quantitatively identified the MP mode and the SPP excitation’s dependence on the period. Five arrays were selected for their SPP excitation wavenumber that approached and then diverged from that of an MP mode. Reflectance spectra from arrays showed dips associated with the two resonances between 10000 cm−1 and 25000 cm−1. Both the magnitude and corresponding wavenumber of nearby dips were modified by the interaction. Moreover, a third dip might appear or two dips might merge into a wider valley when two resonance excitation wavenumbers are close enough. The interaction was further elucidated with electromagnetic fields, Poynting vectors, and the energy density corresponding to representative reflectance dips.
Preliminary Investigation of a Liquid Desiccant System for Dehumidification and Cooling in Athens
Authors: Koronaki I. P. , Christodoulaki R. I. , Papaefthimiou V. D. , Rogdakis E. D.
Published: April 2014

Liquid desiccant air conditioning systems have recently been attracting attention due to their capability of handling the latent load without super-cooling and then reheating, as happens in the conventional compression-type air conditioning systems. In liquid desiccant cooling cycles, a sorbent solution is employed to dehumidify the air, circulating between the two critical components; the dehumidifier and the regenerator. As the strong desiccant solution is sprayed on top of the internally cooled dehumidifier, it flows down by gravity and comes in contact with the process air. The desiccant solution which, by definition, has a strong affinity for water vapor absorbs moisture from the air. The end of the process finds the air cool and dehumidified and the solution diluted. The diluted desiccant solution enters the regenerator in order to retrieve its initial concentration. Hot water derived from a low temperature source supplies the necessary heat to the solution and the excessive water content is evaporated. At the end of the process, the hot humid air is rejected to the ambient and the concentrated solution is driven to the dehumidifier.

The complex heat and mass transfer phenomena, occurring both in the dehumidifier and regenerator, has been the subject of earlier work by the authors. Based on the knowledge gained, a liquid desiccant system was installed at the National Technical University of Athens, Laboratory of Applied Thermodynamics, for experimental purposes. The liquid desiccant system was constructed by the German company L-DCS [1].

The main components of the system are the dehumidifier, the regenerator and the evaporative cooler. The system uses water as the cooling medium and LiCl solution as the desiccant. It also employs two storage tanks, one for the concentrated solution and one for the diluted. The purpose of this publication is to present the newly installed liquid desiccant system, to predict the performance of the dehumidifier and to carry out preliminary design optimization.
Experimental Study of a Roll-Plane Hydraulically Interconnected Suspension System Under Vehicle Articulation Mode
Authors: Xu Guangzhong , Roser Holger M. , Zhang Nong
Published: April 2014

This paper presents a detailed experimental study to quantitatively assess the performance of a roll-plane Hydraulically Interconnected Suspension (HIS) system in articulation (warp) mode. This mode is critical for better off-road vehicle handling, particularly in utility vehicles. Articulation of a four-wheel vehicle describes the in-phase motion of two diagonally opposed wheels, with adjacent wheels moving out of phase.

The widely used anti-roll bars, required for increased roll resistance, also stiffen the articulation mode, which may result in one or more wheels losing ground contact on uneven surfaces, compromising vehicle stability and safety. Yet roll-plane HIS systems are capable of decoupling vehicle roll from articulation.

A comparative experimental analysis of HIS and conventional anti-roll bars has been conducted to evaluate vehicle dynamic performance at full-car level under articulation excitation. Test results demonstrate that the HIS system has a negligible effect on wheel travel in articulation mode, offering a significant improvement in vehicle handling and safety over conventional anti-roll bars.
Experimental Study on the Heat Transfer Performance of the Diffusion-Bonded Micro Channel Heat Exchanger in the Pilot-Scale Test Facility
Authors: Yoon Seok Ho , Oh Dong-Wook , Kim Young , Choi Jun Seok
Published: April 2014

The heat exchangers using micro channel structure have been studied due to its high efficiency and compactness. If the micro channel heat exchanger is applied to the natural gas liquefaction process, the efficiency of LNG plant can be improved. In this study, the micro channel was fabricated by chemical etching and the heat exchanger core was made by the diffusion bonding method for cryogenic reliability. For applying to the large scale plant such as LNG plant, the pilot-scale thermal performance test setup of the heat exchanger was built. Tests can be performed in the cryogenic environment. The working fluid is cryogenic nitrogen gas. Two different temperature level of nitrogen gas was made by vaporizing from liquid nitrogen. And these fluids exchange the heat through the micro channel heat exchanger. Test rig is an open loop. Therefore nitrogen gas is discharged to the ambient. Temperatures are measured by RTD sensors. Inlet pressures of heat exchanger are measured by the cryogenic pressure transducer and pressure differences of heat exchanger are measured by the differential pressure transmitters. And all the measured data is acquired by DAQ module and saved into PC. The heat transfer coefficients of the micro channel heat exchanger are calculated and the heat transfer characteristics are investigated. And the test result was compared with the existing heat transfer correlations. And the modified heat transfer correlation of the micro channel heat exchanger in the cryogenic environment is suggested.