bluuebunny/crossref_metadata_2025 huggingface dataset:
Etnografía, epistemología y reflexividad. Experiencia de acompañamiento a una comunidad en resistencia en México
Authors: Arriaga Ornelas José Luis
Published: January 2019

Este es un texto epistemológico que pretende hacer una observación de segundo orden. Es un trabajo reflexivo sobre la postura de quienes, haciendo antropología “desde el sur”, han acompañado al pueblo de Xochicuautla, municipio de Lerma, Estado de México, en su resistencia de años contra un proyecto carretero que atravesaría el territorio de su comunidad. El argumento a desarrollar se refiere, en un primer momento, a quien pretende hacer trabajo etnográfico como observador; y en un segundo momento se detiene en el objeto observado y el desarrollo de su capacidad para pensarse a sí mismo, delimitarse de un entorno y auto-organizarse. Los principales resultados que se ofrecen son: la constancia de un tipo de trabajo etnográfico que abona a la recuperación del ser histórico del sujeto de estudio, con sentidos crítico y ético distintos al marco nomológico-descriptivo de la antropología eurocéntrica, y una propuesta de ruptura epistemológica con el pensamiento moderno-occidental y su estética representacionalista.
La foto-etnografía como metodología de investigación para el estudio de manifestaciones conmemorativas contestatarias en el espacio público
Authors: Hermansen Ulibarri Pablo , Fernández Droguett Roberto
Published: January 2019

En el marco de diferentes investigaciones que hemos desarrollado sobre manifestaciones políticas conmemorativas en el espacio público de Santiago de Chile, en este artículo presentamos la aproximación metodológica fotoetnográfica que elaboramos para observar y comprender el fenómeno desde la perspectiva de las formas de aparición en el espacio público y las luchas por la visibilización de los manifestantes. Asumimos que ni las imágenes ni los modos de narración de los fenómenos sociales en la etnografía son neutros, sino que dependen de la posición de los investigadores, por lo cual nos ubicamos en una perspectiva de diálogo y de cercanía con las luchas de los actores sociales que se manifiestan en estas conmemoraciones. En términos metodológicos, la propuesta que hemos venido desarrollando pretende ofrecer orientaciones epistemológicas y procedimentales sobre la fotoetnografía y la articulación entre saberes y prácticas propias de la etnografía.
Notas sobre el uso de la etnografía y la teoría fundamentada en ciencia política. Un análisis amplio de la participación política y el Estado en asentamientos informales de la periferia de Buenos Aires, Argentina
Authors: Besana Patricio Bruno
Published: January 2019

A la luz de los resultados obtenidos en el marco de una tesis doctoral sobre la participación política de quienes residen en asentamientos informales de la periferia de Buenos Aires (Argentina), el presente artículo reflexiona sobre la pertinencia del uso de la etnografía en la ciencia política. Desde una perspectiva innovadora que la combina con el enfoque de la teoría fundamentada, se sugiere que dicha combinación permite avanzar a la teoría en temas poco desarrollados al interior de la disciplina. Puntualmente, se hace una introducción al tema de la participación política y se describen las ventajas del enfoque propuesto. Por último, se sugiere la posibilidad de complementar la etnografía y la teoría fundamentada con otros métodos y herramientas de recolección de datos.
An Assessment of Health Hazards in Valves for Gaseous Oxygen Service: Sources and Preventive Measures
Authors: Kumar Anil , Sheikh Younus
Published: January 2019

Oxygen content in air is approximately 21% by volume. With many industrial uses, mainly in the manufacture of steel and chemicals, for metal cutting, welding ,hardening & scarfing, it is being transported as a non-liquefied gas at pressures of 138 bar (13800000 Pa) or above, also as a cryogenic fluid at pressures and temperatures below 13.8bar (1380000 Pa) & −146.5°C (126.65K). Commonly we found air separation plants produce ultra-pure oxygen (> 99.9% purity) via liquefaction of atmospheric air and separation of the oxygen by fractionation and thereby transported to the needy areas via pipelines.

The research efforts directed towards technical assessment to establish the correlations between valve construction and turbulence and solving the complications in the transported ultra-pure oxygen gas in the pipelines and through mounted valves. Hence, it is necessary to study the performance, complexities and fire hazards associated with the valves transporting it and the preventive measures to avoid any catastrophic failure in ultra-pure gaseous oxygen services. The study was conducted on two isolation valves — each of ball and globe of relative size. It was realized that velocities of the ultrapure gaseous oxygen on the impingement sites inside the valve are beyond the safe limit as recommended by European Industrial Gas Association (EIGA) [4] and various other prominent industrial gas manufacturers. Moreover, globe valve gave relatively less turbulence and velocity at initial opening of the valve. The study revealed that majority of health hazards & accidents on industrial usage of ultra-pure gaseous oxygen media are the result of the inadequate awareness of the degreasing or cleaning and optimum material selection and construction of the valve and fittings on the industrial pipeline.
Influence of Façade Area on Thermal Performance of Building for Cooling Purposes
Authors: Almutairi Hamad H. , Almutairi Abdulrahman , Almutairi Jaber H.
Published: January 2019

Buildings account for significant energy consumption worldwide particularly in regions where energy patterns influenced primarily by weather. Air conditioning system became an essential evaluation factor during building design and construction. The level of curiosity about air conditioning system efficiency in terms of energy usage is increasing quickly. In Kuwait; which is a hot climate country; air conditioners account for 70% of total electrical power. Electricity in Kuwait is produced entirely by the non-renewable energy resources. This work aims to assess the potential electrical savings that could be acquired by reducing building’s façade area towards East-West directional orientation in Kuwait. For this purpose, a detached building model with uniform geometry; was simulated by Energy Plus Thermal Simulation Engine through its interface with DesignBuilder software. Two cases were developed for the analysis; both have the same simulation inputs. The only difference was the orientation of the facades. The results show a reduction of about 900 kWh cooling annually if the largest facades were positioned towards north and south. The obtained saving in annual basis is attributed to about 420 kWh electrical power. Equivalent CO2 emissions associated with the saved electrical energy from power plants in Kuwait were estimated. The resulted savings are promising for early decision making for prospective buildings to be built in future.
Taxonomy for Secure CyberManufacturing Systems
Authors: Wu Mingtao , Moon Young B.
Published: January 2019

CyberManufacturing System (CMS) is a vision for manufacturing systems where physical machinery and processes are fully and seamlessly integrated with computational resources. However, this very ubiquitous connectivity opens unintended new doors for cyber-attacks into CMS. This type of attack begins in a digital format, intrudes through computer networks, and ultimately causes physical damages.

Despite the criticality of the CMS security, research on the subject is in its infancy. New types of cyber-physical attack are emerging but not well understood. In order to gain new insights into the problems and to assist much needed research, a taxonomy — as a common language for the interdisciplinary work — was developed and is presented in this paper. The taxonomy is defined in six dimensions: (i) human, (ii) product, (iii) equipment, (iv) intellectual property, (v) environment, and (vi) operation. For each dimension, attacks are decomposed further in terms of attack targets, sub-targets and attack methods. Examples of using the taxonomy are presented.
Improving Boiler Efficiency Using PLC Controller
Authors: Tang Hung , Abu-Ayyad Ma'moun
Published: January 2019

Boiler systems have many factors that affect the efficiency of the air conditioning process. A traditional control system is complicated and requires physical hardware and software programming. The modern operator console is more compact and works better. Regardless of the boiler system, the operator can run it automatically, allowing changes in many variables such as fuel input, air combustion, water feed flow, steam temperature, etc. In fact, it is impossible to control all of these variables simultaneously in the manual mode. Modern systems have been developed to a high degree of precision that can provide excellent results in maintaining high levels of efficiency, reliability, and safety. The Programmable Logic Controller (PLC) was developed in 1968, and since then it has improved rapidly and applied to many manufacturing industries. Besides the Allen Bradley PLC, other modules were developed such as Human Machine Interface (HMI), Variable Frequency Drives (VFDs), and safety components. In this paper, the Allen Bradley PLC ControlLogix family 1756 model is used to control the boiler system. In addition, this work focuses on improving the boiler efficiency by comparing between the manual and automatic control the fuel-air ratio.
Influence of Selective Laser Heat Treatment Pattern Position on Geometrical Variation
Authors: Sagar Vaishak Ramesh , Wärmefjord Kristina , Söderberg Rikard
Published: January 2019

Selective laser heat treatment allows local modification of material properties and can have wide range of applications within the automotive industry. Enhanced formability and strength are possible to achieve. As the process involves selective heating, positioning of the heat treatment pattern in local areas is vital. Pattern positioning is often suggested based on the part design and forming aspects of the material to avoid failures during manufacturing. Along with improving material properties in desired local areas, the process also produces unwanted distortion in the material. Such effects on variation should be considered and minimized.

In this paper, heat treatment pattern is offset from its original position and its effect on geometrical variation is investigated. Boron steel blanks are selectively laser heat treated with a specific heat treatment pattern and then stamped to desired shape. Two heat treatment pattern dimensions are examined. Variation at blank level and after stamping, and springback after stamping is observed. Results show that pattern offsetting leads to higher geometrical variation. Therefore, correct positioning of heat treatment pattern is important to minimize its effect on geometrical variation along with enhancing the material properties. Knowledge from this study will contribute to various stages of the geometrical assurance process.
Modeling Stablization of Crane and Ship by Gyroscopic Control Using the Moving Frame Method
Authors: Flatlandsmo Josef , Smith Torbjørn , Halvorsen Ørjan O. , Vinje Johnny , Impelluso Thomas J.
Published: January 2019

Norwegian industries are constantly assessing new technologies and methods for more efficient and safer production in the aqua cultural, renewable energy, and oil and gas industries. These Norwegian offshore industries share a common challenge: to install new equipment and transport personnel in a safe and controllable way between ships, farms and platforms. This paper deploys the Moving Frame Method (MFM) to analyze the motion induced by a crane and controlled by a gyroscopic inertial device mounted on a ship. The crane is a simple two-link system that transfers produce and equipment to and from barges. An inertial flywheel — a gyroscope — is used to stabilize the barge during transfer. The MFM describes the dynamics of the system using modern mathematics. Lie group theory and Cartan’s moving frames are the foundation of this new approach to engineering dynamics. This, together with a restriction on the variation of the angular velocity used in Hamilton’s principle, enables an effective way of extracting the equations of motion. This project extends previous work. It accounts for the dual effect of both the crane and the stabilizing inertial device. Furthermore, this work allows for buoyancy and motor induced torques. Furthermore, this work displays the results in 3D on cell phones. The long-term results of this work leads to a robust 3D active compensation method for loading/unloading operations offshore. Finally, the interactivity between the crane and the stabilizing gyro anticipates the impending time of artificial intelligence when machines, equipped with on-board CPU’s and IP addresses, are empowered with learning modules to conduct their operations.
Gyroscopic Wave Energy Generator for Fish Farms and Rigs
Authors: Norbach Alexandra , Fjetland Kotryna Bedrovaite , Hestetun Gina Vikum , Impelluso Thomas J.
Published: January 2019

Norway has an opportunity to harvest ocean wave energy through gyroscopic precession as an alternative source of renewable energy, within practical limitations. This research assesses the energy extracted by gyroscopic wave energy generators and their use to provide supplementary power to fish farms and lighting on oilrigs. This project implements the Moving Frame Method (MFM) in dynamics to model the extracted power from a gyroscopic wave energy generator. The MFM leverages Lie Group Theory, Cartan’s moving frames and a new notation from the discipline of geometrical physics. Continuing, the Principle of Virtual Work extracts the equations of motion from the structure of the Special Orthogonal Group. However, the MFM supplements its analysis with a novel application of the restriction on the variations of the angular velocities. This research extends previous work as follows: it accounts for motor torques, it opens a placeholder for buoyancy, and it solves the full 3D set of equations (without assuming negligible yaw). After showing how to obtain the suite of descriptive equations of motion, this project integrates them, however with a relatively simple integration scheme. To complete each step in the analysis, the rotation matrix is updated using the Cayley Hamilton Theorem and the Rodriguez formula. Finally, the results are displayed using the Web Graphics Library such that the actual numerical analysis and display happens on cell phones.
Amplitude and Sweeping Direction Dependent Nonlinear Ultrasonic Resonance Spectroscopy for Fatigue Crack Detection
Authors: Shen Yanfeng , Roy Nipon , Wang Junzhen , Liu Zixuan , Rao Danyu , Xu Wu
Published: January 2019

This paper investigates the amplitude and sweeping direction dependent behavior of nonlinear ultrasonic resonance spectroscopy for fatigue crack detection. The Contact Acoustic Nonlinearity (CAN) and the nonlinear resonance phenomena are illuminated via a reduced-order bilinear oscillator model. Unlike conventional linear ultrasonic spectroscopy, which would not change its pattern under different amplitudes of excitation or the frequency sweeping direction, the nonlinear resonance spectroscopy, on the other hand, may be noticeably influenced by both the wave amplitude and the loading history. Both up-tuning and down-tuning sweeping active sensing tests with various levels of excitation amplitudes are performed on a fatigued specimen. Short time Fourier transform is adopted to obtain the time-frequency features of the sensing signal. Corresponding to each excitation frequency, a nonlinear resonance index can be established based on the amplitude ratio between the superhamronic, the subharmonic, the mixed-frequency response components and the fundament frequency. The measured nonlinear resonance spectroscopy for a certain amplitude and frequency sweeping direction can be readily used to establish an instantaneous baseline. The spectroscopy of a different amplitude or frequency sweeping direction can be compared with such an instantaneous baseline and a Damage Index (DI) is obtained by measuring the deviation between the two spectra. Experimental investigations using an aluminum plate with rivet hole nucleated fatigue cracks are performed. A series of nonlinear spectroscopies are analyzed for both the pristine case and the damaged case. The spectral features for both cases are obtained to demonstrate the proposed fatigue crack detection methodology which may find its application for structural health monitoring (SHM). The paper finishes with summary, concluding remarks, and suggestions for future work.
Integrating an Analytical Uncertainty Quantification Approach to Multi-Scale Modeling of Nanocomposites
Authors: Acar Pınar
Published: January 2019

This work addresses the integration of an analytical uncertainty quantification approach to multi-scale modeling of single-walled carbon nanotube (SWNT)-epoxy nanocomposites consisting of pristine systems. The computational modeling starts with the dendrimer growth approach, which is used to build an epoxy-SWNT network. Next, the molecular dynamics simulations are performed to obtain thermal and mechanical properties. The SWNT orientations are assumed to have natural stochasticity which is modeled by an analytical uncertainty algorithm. Next, the propagation of the uncertainties to the volume-averaged properties of the SWNT and nanocomposite is obtained. The uncertainties are shown to affect the macro-scale properties such as stiffness, thermal expansion, thermal conductivity and natural frequencies.
Guided Wave Generation and Propagation in Self-Sensing Piezoelectric Composite Plates for Structural Health Monitoring
Authors: Wang Junzhen , Shen Yanfeng
Published: January 2019

This paper presents a systematic numerical investigation of guided wave generation, propagation, interaction with damage, and reception in anisotropic piezoelectric composite plates. This approach employs piezoelectric composite materials as both load bearing and sensing elements. Finite element modal analysis of a plate unit cell with Bloch-Floquet boundary condition is performed to understand the guided wave propagation characteristics in piezoelectric composite plates. The guided wave generation and tuning characteristics are investigated using the harmonic analysis model with absorbing boundary conditions. The relationship between the generated wave modes and the laminate layup orientations is studied. Subsequently, an impact damage is introduced and modeled as a group of cone shape delaminated layers and stiffness losses within the layers through the thickness direction. 2D and 3D transient dynamic coupled-field finite element models are constructed to simulate the procedure of guided wave generation, propagation, interaction with the impact damage, and reception in an orthotropic piezoelectric composite plate using the commercial finite element software (ANSYS). In addition, Contact Acoustic Nonlinearity (CAN) is simulated via time domain transient analysis. Advanced signal processing techniques are used to extract the distinctive nonlinear features. The frequency-wavenumber analysis is further adopted to decipher wave modes and frequency components in the scattered wave field. This paper finishes with concluding remarks and suggestions for future work.
Effect of Micro (Banana) and Nano (SiC) Fillers on Mechanical Behaviors of Basalt/Epoxy Hybrid Composites
Authors: Velukkudi Santhanam Senthil Kumar , Sampath Prakash , Ponnusamy Bharani Srikanth , Bangaru Mohan
Published: January 2019

Basalt Fibre Reinforced Polymers (BFRP) was feasibly utilized as a preferable replacement to the Glass Fibre Reinforced Polymers (GFRP) due to their superior property and behaviour. Besides, reinforcing nano and micro fillers with basalt fiber will result in even better mechanical properties. In this research study, epoxy resin was blended with Cashew Nut Shell Liquid (CNSL) hardener, it beneficial to minimize the healing period. For 50% of epoxy resin, the ratio of CNSL hardener was taken as 50%. Standard Hand lay-up technique was utilized to produce the composite structures. In addition, 20g of nano and micro fillers were mixed with each epoxy-CNSL proportion. Accordingly, both (SiC & Banana) filler reinforced composites were fabricated and cut to the ASTM standard. Finally, the result of mechanical properties such as flexural and the impact (Charpy) of silicon carbide (SiC) and banana filler reinforced samples were compared.
Computational Design and Analysis of Nitinol-Based Arch Wedge Support
Authors: Stranburg Tyler , Liu Yucheng , Chander Harish , Knight Adam
Published: January 2019

A nitinol-based arch wedge support (AWS) was designed using computational approach. Finite element analysis (FEA) was performed to on this design to assess the influence of loading, boundary conditions, and thickness on the mechanical response of the computer-aid design (CAD) model. Five loading conditions caused by different human movements, two boundary conditions, and three thicknesses are involved in this computational study. FEA results showed that the presented AWS design can resist forces caused by different human motions without generating any permanent deformation. The study features the first time to design and evaluate a thin-walled nitinol AWS model. The results of this study form the background of prototyping and experimental testing of the design in the next phase.
Method of Construction for High Cycle Fatigue Resistant Pressure Vessels in Hydrogen Service
Authors: Mahmoudian Pooya
Published: January 2019

Currently, pressure vessels that operate in hydrogen service and subjected to fatigue must be designed using a defect tolerant design procedure. This means that first the fracture mechanics properties of the material being considered must be measured in hydrogen at the maximum service pressure. The properties are fatigue crack propagation properties and threshold stress intensity factor for hydrogen embrittlement (KIHE). With these properties, a fatigue crack propagation life can be estimated assuming an initial crack size and geometry and growing this defect to failure. The property measurements are costly and can only be performed at a few laboratories. Furthermore, the resulting lives are usually very short because of the assumed initial crack size. These things limit the application of this design method to lower cycle or static loading applications. This work introduces a cost-effective method of design and construction of pressure vessels for high cycle use in hydrogen service at pressures below 40,000 psi that eliminates the need for determining fracture mechanics properties in hydrogen environment. The method uses shrink fit construction of a liner inside a jacket. The method requires that when the pressure is applied, the magnitude of the resultant stress at the pressure boundary of the liner is more compressive than the magnitude of the applied pressure and the maximum allowed size of defect in the jacket at the interface between the jacket and the liner is such that when the cyclic stress is applied the resultant fatigue loading of that defect at that location to be less than the threshold value for growth of that defect.
Optimal Vibration Control and Energy Scavenging Using Collocated Nonlinear Energy Sinks and Piezoelectric Elements
Authors: Ahmadabadi Zahra Nili , Khadem Siamak Esmaeilzadeh
Published: January 2019

This paper presents an optimal design for a system comprising multiple nonlinear energy sinks (NESs) and piezoelectric-based vibration energy harvesters attached to a free–free beam under shock excitation. The energy harvesters are used for scavenging vibration energy dissipated by the NESs. Grounded and ungrounded configurations are examined, and the systems parameters are optimized globally to maximize the dissipated energy by the NESs. The performance of the system was optimized using a dynamic optimization approach. Compared to the system with only one NES, using multiple NESs resulted in a more effective realization of nonlinear energy pumping particularly in the ungrounded configuration. Having multiple piezoelectic elements also increased the harvested energy in the grounded configuration relative to the system with only one piezoelectric element.
Friction Stir Back Extrusion: Preliminary Investigations on Through-Wall Characteristics for Al-1100-O
Authors: Menard Austin , Gallardo Clarissa , Emblom William J. , Wagner Scott W. , Olayinka Ayotunde , Loehn Clayton , Seguin Daniel , Wahab Muhammad A.
Published: January 2019

Friction stir back extrusion has recently been identified as a method for manufacturing stronger, more ductile seamless tubes. However, most of the work to date has investigated tubes with low length to diameter ratios and there has been little work investigating the change in grain through the thickness of the tube wall. The current project presents preliminary results in an investigation of the effect of the stirring process on developing ultrafine grain through the tube wall. The long term goal of the project is to miniaturize the process in order to produce highly ductile microscale tubes for biomedical applicaions, microscale heat exchangers, and fuel cell manufacturing applications.

Friction stir back extrusion is a variation of friction stir processing and friction stir welding in that the end of a non-cutting tool rotates against a metal work piece, heats the work piece, and creates an ultrafine grain structure. The work described here considers tool speed and diameters when forming tubes from A1100-O aluminum work pieces. It was found that for rotations varying from 750 RPM to 2000 RPM that the maximum stir zone was approximately 250 μm at the bottom of the tube and approximately 50 μm in the walls. The outside diameter of the tubes was 12.5 mm and inside diameters of 6.35 mm and 9.3mm were produced.
Active Vibration Control of a Helicopter Rotor Blade by Using a Linear Quadratic Regulator
Authors: Uddin Md Mosleh , Sarker Pratik , Theodore Colin R. , Chakravarty Uttam K.
Published: January 2019

Active vibration control is a widely implemented method for helicopter vibration control. Due to the significant progress in the microelectronics, this technique outperforms the traditional passive control technique due to the weight penalty and lack of adaptability for the changing flight conditions. In this paper, an optimal controller is designed to attenuate the helicopter rotor blade vibration. The mathematical model of the triply coupled vibration of the rotating cantilever beam is used to develop the state-space model of an isolated rotor blade. The required natural frequencies are determined by the modified Galerkin method and only the principal aerodynamic forces acting on the structure are considered. Linear quadratic regulator is designed to achieve the vibration reduction at the optimum level and the controller is tuned for the hovering and forward flight.
Retracted: “Design and Optimization of a Multipurpose Urban Firefighting and Disaster Relief UAV” [ASME 2018 International Mechanical Engineering Congress and Exposition, Volume 1: Advances in Aerospace Technology, Pittsburgh, Pennsylvania, USA, November 9–15, 2018, Conference Sponsors: ASME, ISBN: 978-0-7918-5200-2, Copyright © 2018 by ASME. Paper No. IMECE2018-86321, pp. V001T03A022; 10 pages; doi: 10.1115/IMECE2018-86321]
Authors: ASME
Published: January 2019

The above referenced paper has been removed from publication. (March 10, 2020)

Copyright © 2020 by ASME
Development of Vehicle Seat by Embedding Urethane Within Air Cell
Authors: Ota Shinichiro , Nakamura Yuji
Published: January 2019

This paper describes a new vehicle seat containing an air cell embedded with urethane. This air cell can be used to control mechanical properties such as spring constants and damping coefficients by varying the air pressure. When the air cell is retrofitted in a vehicle seat, it is essential for us to analyze its vibration characteristics, which is the aim of this study. Herein, after the air cell is retrofitted in a vehicle seat, its vibration characteristics are examined by performing excitation experiments using the prototype seat. From the results of this experiment, the resonance frequency of the human dummy (45.6 kg) was found to be 6.0 Hz when the pressure within the air cell was 2 kPa. However, the resonance frequency of the human dummy was found to be 5.3 Hz when the pressure within the air cell was 10 kPa. These results indicate that the vibration characteristics of the prototype seat can be varied by controlling the pressure within the air cell.
Study on Motor-Driven Gyroscopic Generator: Part 1 — Characteristics at Constant Velocity
Authors: Hosaka Hiroshi , Oonishi Yoshinori , Tajima Yuki , Yamashita Akira
Published: January 2019

A gyroscopic power generator that generates 1.8 W by using a rotor of 100 mm diameter spinning at 500 rpm is developed. In conventional vibrational generators, which use simple vibrations of a inner pendulum, the output power has been less than 10 mW. Gyroscopic generators increase the inertial force by rotating the pendulum at high speed and generate about 100 times greater power than the conventional ones. However, gyro generators have not been able to operate under arbitrary vibrations at wearable sizes because they are unstable and easily stall by disturbances, and the gyro torque and the electromechanical transformation efficiency rapidly decrease by miniaturization. In this paper, first, a theoretical model is developed to clarify the basic characteristics of the generator. Next, a desktop-sized generator that works under any vibration is developed using highly precise motors and gears determined by the theory. Next, mechanical and electrical characteristics are measured to show the validity of the theory. Finally, the performance of wearable-sized generators is predicted to show the generators that have the same device size and rotor spinning speed as those of 2.5” and 3.5” HDD’s generate 0.74 W and 1.84 W, respectively.
A Comparative Study Between Selective Laser Melting and Electron Beam Additive Manufacturing Based on Thermal Modeling
Authors: Rahman M. Shafiqur , Schilling Paul J. , Herrington Paul D. , Chakravarty Uttam K.
Published: January 2019

Selective Laser Melting (SLM) and Electron Beam Additive Manufacturing (EBAM) are two of the most promising additive manufacturing technologies that can make full density metallic components using layer-by-layer fabrication methods. In this study, three-dimensional computational fluid dynamics models with Ti-6Al-4V powder were developed to conduct numerical simulations of both the SLM and EBAM processes. A moving conical volumetric heat source with Gaussian distribution and temperature-dependent thermal properties were incorporated in the thermal modeling of both processes. The melt-pool geometry and its thermal behavior were investigated numerically and results for temperature profile, cooling rate, variation in specific heat, density, thermal conductivity, and enthalpy were obtained with similar heat source specifications. Results obtained from the two models at the same maximum temperature of the melt pool were then compared to describe their deterministic features to be considered for industrial applications. Validation of the modeling was performed by comparing the EBAM simulation results with the EBAM experimental results for melt pool geometry.
Three-Tier Impingement Cooling Design for Gas Turbine Blade Trailing Edge
Authors: Ramakrishnan Kishore Ranganath , Singh Prashant , Ekkad Srinath V.
Published: January 2019

Gas turbine blades are subjected to elevated heat loads due to highly turbulent hot gases exiting the combustor section. Several internal and external cooling techniques are used to protect the blades from such hostile environment. Trailing edge of a turbine blade is usually cooled with array of staggered cylindrical pins, which connects the pressure and suction side internal walls and hence provide improved structural integrity. However, the heat transfer enhancement levels for array of pin-fins is generally lower than jet impingement and ribbed channels. In this study, we present a three-tier impingement cooling design for blade trailing-edge and part of mid-chord region. In this design, pressure and suction side internal walls are subjected to oblique jet impingement. Three different configurations have been studied where we have systematically varied the jet diameters and number of jets in an array for different tiers. Numerical simulations have been carried out for different flow conditions, which corresponds to Reynolds numbers (based on 1st-passage jet diameter) ranging between 3000 and 46000. First two plenums had high levels of heat transfer due to oblique jet impingement, where the suction side internal wall representative surface, had higher heat transfer compared to the pressure side internal wall. Third tier had the lowest heat transfer due to triangle-like configuration where jets were almost parallel to pressure and suction side surfaces, and hence their effectiveness was lower than the oblique jet impingement in upstream two tiers.
Modeling the Influence of Microstructure on Stress Distributions and Concentrations in Pitting Corrosion
Authors: Brewick Patrick , Geltmacher Andrew , Qidwai Siddiq M.
Published: January 2019

Despite the many advances made in material science, stainless steel and aluminum remain the structural materials best-suited for the naval fleet. While these metallic materials offer many benefits, such as high strength and good toughness, their persistent exposure to the maritime environment inevitably leads to issues with corrosion. Among the various manifestations of corrosion, pitting corrosion is of particular concern because the transition of corrosion pits to stress-corrosion cracks can lead to catastrophic failures. Traditional pitting corrosion analyses treat the pit shape as a semi-circle or ellipse and typically assume a growth pattern that maintains the original geometrical shape. However, when the underlying microstructure is incorporated into the model, pit growth is related to the grains surrounding the pit perimeter and the growth rate is proportional to crystallographic orientation. Since each grain has a potentially different orientation, pit growth happens at non-uniform rates leading to irregular geometries, i.e., non-circular and non-elliptical. These irregular pit geometries can further lead to higher stresses.

This work presents a detailed look at corrosion pit growth coupled with mechanical load through a numerical model of a two-dimensional stable corrosion pit. Real microstructural information from a sample of 316 stainless steel is incorporated into the model to analyze microstructural effects on pit growth. Through this work, stress distributions and stress concentration factors are examined for a variety of pit geometries, including comparisons of their range of values to a typical, semi-circular pit. The consequences of these stress distributions and concentration factors are discussed.
How Solar and Storage Can Reduce Coincident Peak Loads and Payments: A Case Study in Austin, TX
Authors: Bandyopadhyay Arkasama , Rhodes Joshua D. , Conger Julia P. , Webber Michael E.
Published: January 2019

This study builds a generalized tool to forecast the change of 4 coincident peak (4CP) loads and payments based on varying amounts of solar, storage capacity, and population estimates over a 10-year period for utilities within the Electric Reliability Council of Texas (ERCOT). It also incorporates an optimization model for the energy storage systems (ESSs) that maximizes the sum of the revenue earned from their operation as well as the net 4CP payments received by the utility by attempting to arbitrage the ERCOT energy market. The tool is illustrated by using empirical data from the municipally-owned utility in Austin, TX (Austin Energy). 4CP payments can be on the order of tens of millions of dollars. Results indicate that solar and storage capacity can substantially lower these payments. For example, a 20 MW increase in solar capacity in 2018 would reduce Austin Energy’s payment by an estimated $200,000 for each subsequent year. By using the novel approach of incorporating coincident peak demand charge reductions at the DSP level, this study highlights the economic value of local generation and storage.
An Approach to Capture Humidity From Exhaled Air
Authors: Grau-Bartual Sandra , Al-Jumaily Ahmed M.
Published: January 2019

Lung supportive devices (LSD) are widely used for respiratory ventilation and therapy to help provide breathing support for patients with various lung diseases including Obstructive Sleep Apnea. These devices deliver air to the patient through a nasal or facial mask, and the use of these devices normally results in dryness in the upper airways. However, the exhaled air consists of very high humidity content. The question raised, is it possible to recover some of the moisture content of this air to reuse in the inhalation process.

This research focuses on developing an element which can recover the moisture from the exhaled air and the possibility of using it for re-inhalation. The main component is made up of a fibrous cotton fabric polymerized with Poly (N-isopropylacrylamide) (PNIPAM) and sewed with a resistor filament to control the temperature. The results show a viable element which is able to trap water molecules from the expiration airflow and release them into the inspiration airflow.
Extending Degree of Disequilibrium Analysis for Automatic Selection of Kinetic Constraints in the Rate-Controlled Constrained-Equilibrium Method
Authors: Hadi Fatemeh , Yousefian Vreg , Sarfaraz Ehsan , Beretta Gian Paolo
Published: January 2019

The Rate-Controlled Constrained-Equilibrium (RCCE) is a model reduction scheme for chemical kinetics. It describes the evolution of a complex chemical system with acceptable accuracy with a number of rate controlling constraints on the associated constrained-equilibrium states of the system, much lower than the number of species in the underlying Detailed Kinetic Model (DKM). Successful approximation of the constrained-equilibrium states requires accurate identification of the constraints. One promising procedure is the fully automatable Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. ASVDADD is based on simple algebraic analysis of the results of the underlying DKM simulation and is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. In this paper, we propose a method, as part of our work-in-progress efforts, that could expand the applicability of the derived constraints. This method involves running DKM calculations for a wider range of initial conditions, appending the results of all these cases one after the other after normalizing, and finally running the ASVDADD method to get a set of ‘universal’ constraints applicable within that range of conditions. The effectiveness and robustness of the derived constraints is examined in hydrogen/oxygen ignition delay simulations and the results are compared with those obtained from DKM. The proof-of-concept results demonstrate the potential of the method for finding ‘universal’ constraints.
One Inclusion in the Infinite Peristatic Matrix
Authors: Buryachenko Valeriy A.
Published: January 2019

A basic problem of of micromechanics is analysis of one inclusion in the infinite matrix subjected to a homogeneous remote loading. A heterogeneous medium with the bond-based peri-dynamic properties (see Silling, J. Mech. Phys. Solids 2000; 48:175–209) of constituents is considered. At first a volumetric boundary conditions are set up at the external boundary of a final domain obtained from the original infinite domain by truncation. An alternative sort of truncation method is periodisation method when a unite cell (UC) size is increased while the inclusion size is fixed. In the second approach, the displacement field is decomposed as linear displacement corresponding to the homogeneous loading of the infinite homogeneous medium and a perturbation field introduced by one inclusion. This perturbation field is found by the Green function technique as well as by the iteration method for entirely infinite sample with an initial approximation given by a driving term which has a compact support. The methods are demonstrated by numerical examples for 1D case. A convergence of numerical results for the peristatic composite bar to the corresponding exact evaluation for the local elastic theory are shown.
Studies on the Hard Chrome Plating in Reciprocating Air Compressors
Authors: Kulasekaran Aadhithiyan Amutha , Subramanian Anbarasu
Published: January 2019

This present work is to investigate the effects of chrome plating in reciprocating air compressors that result in reduction of power consumption. Reciprocating air compressors are the most commonly used compressors for domestic and industrial purposes to give required air output in terms of free air delivery, delivery temperature and maximum working pressure. This study also develops a better understanding on the effect of honing in the cylinder which reduces the surface roughness in the cylinder liner and results in greater air output. Cylinders are made of graded cast iron. The cylinder liner was honed to a thickness of about 0.26 mm and hard chrome plated to the same thickness. The honing improves the volumetric efficiency and hard chrome plating reduces the power consumption. The adequacy of this model can be verified using thermal image analysis, which includes the various temperature distribution plots around the compressor components. Further delivery temperature, actual displacement and free air delivery pressure are the parameters that conclude the deviation in actual and experimental values. Power consumption and efficiency owe for the major expenditures and maintenance for Reciprocating air compressors. This paper suggests the need of hard chrome plating to a compressor cylinder that resulted in annual power savings of about 25%. The increase in volumetric efficiency was about 20–30% from the actual conditions.
Recent Advancements in Spikes Used in Hypersonic Re-Entry Vehicles by Using CFD
Authors: Madhukar E. L. N. Rohit , Panjagala Harish
Published: January 2019

The recent introduction of spike in the frontal region of high speed reentry vehicles has brought a tremendous improvement in space activities in the world. The major issue that the spikes resolves is aero heating of re-entry vehicles. Moreover, it preserves structural integrity and avoids damage. Usage of spike is economical and effective over different kinds of thermal protection system. Previous investigation on spiked re-entry vehicles leads to a conclusion that the Blunt and Snap spikes resulted in better reduction of temperature at nose of re-entry vehicle. This paper deals with geometry optimization of blunt and snap spike specifically the length, which is varied as L/8, L/4 and 3L/8 respectively where L is the length of the vehicle. ANSYS 17.2 FLUENT solver is incorporated for analysis purpose and the results are compared among the three different length spike re-entry vehicles. Modal analysis has also been carried out and natural frequency of spikes are obtained. This would provide a way to accept the safe and economical design with better thermal protection of the high-speed space vehicle.
The Development of a Simple Alternative Hybrid Engine for Gasoline, LPG and Biogas
Authors: Pramuanjaroenkij Anchasa , Tongkratoke Amarin , Phankhoksoong Siriluk , Kakaç Sadık
Published: January 2019

This work was focused on the development of a hybrid engine which was fueled with three different fuels; gasoline as original fuel, Liquid Petroleum Gas (LPG) and biogas as two alternative fuels. The developed engine consisted of fuel storage tanks, a small gas reducer, a fuel premixer and the engine of a Suzuki Skydrive 125CC motorcycle. Performances of the prototype and developed engines were compared in terms of wheel speed. The developed engine could be started, idled and accelerated with the average maximum speed of 1276 revolutions per minute when it was connected directly with the biogas reservoir. Then, the biogas was compressed and stored in a standard gas tank which was connected with the developed engine, the average maximum speed of 1273.67 revolutions per minute was obtained from three experiments. This work emphasized not only biogas usage as the alternative fuel for the engine but also pointed out that biogas quality could affect the engine performance. The developed engine could be applied as vehicle engine or it could drive household self-power generators by using household biogas as fuel.
Numerical Simulation of Droplet Emergence and Growth From Gas Diffusion Layers (GDLs) in Proton Exchange Membrane (PEM) Fuel Cell Flow Channels
Authors: Benner Jingru , Mortazavi Mehdi , Santamaria Anthony D.
Published: January 2019

Liquid water management is critical for Proton Exchange Membrane (PEM) fuel cell operation, as excessive humidity can lead to flooding and cell performance degradation. Water is produced in the cathode catalyst layer during the electrochemical reaction. If reactant gas streams become saturated, liquid water forms and must travel through anode and cathode Gas Diffusion Layers (GDLs) to reach flow channels for removal. Understanding the dynamic behavior of the droplet is critical to improve water removal strategies for PEM fuel cells. In this study a 3D, transient, two-phase model based on the Volume of Fluid (VOF) method was developed to study a single droplet in the gas channel. The formation, growth, and breakup of the droplet is tracked numerically and analyzed. The pressure drop across the droplet is monitored over time and compared with theoretical analysis. The droplet size and shape change over time for two different pore sizes are compared. The impact of various gases including air, helium, and hydrogen on droplet dynamics is presented. The viscous force and pressure force on the droplet and the drag coefficient are calculated.
Low-Temperature Energy Efficiency of Lithium-Ion Batteries
Authors: Nazari Ashkan , Esmaeeli Roja , Hashemi Seyed Reza , Aliniagerdroudbari Haniph , Farhad Siamak
Published: January 2019

In this study, the low-temperature energy efficiency of lithium-ion batteries (LIBs) with different chemistries and nominal capacities at various charge and discharge rates is studied through multi-physics modeling and computer simulation. The model is based on the irreversible heat generation in the battery, leading to the charge/discharge efficiency in LIBs with graphite/LiFePO4, graphite/LiMn2O4, and graphite/LiCoO2 electrode materials in which the effects of the battery nominal capacity at various charge and discharge rates are studied. Using characterized sources of the heat generation in the LIB leads to providing a battery efficiency plot at different operation condition for each LIBs. The results of this study assist the battery engineers to have much more accurate prediction over the efficiency of the LIBs at low temperatures.
Computational Design of a Bird-Inspired Perching Landing Gear Mechanism
Authors: Nadan Paul M. , Lee Christopher L.
Published: January 2019

To support the design of a mechanism with two opposing, underactuated, multi-segmented feet that enables a small UAV to grasp and perch upon a branch or similar structure, a hybrid empirical-computational model has been developed that can be used to predict whether the mechanism can kinematically grasp structures with a range of cross-section shapes and sizes in various orientations and to quantify the forces exerted by the grasp. The model, based on experimentally-determined parameters, relates the curvature of the feet to the displacement and tension of the cable tendon which is related in turn to the weight of the UAV. The working principle of the landing gear follows the anatomy of birds that grasp and perch as tendons in their legs and feet are tensioned. Results demonstrate how the model can be used to simulate and evaluate grasping in order to determine the size and weight of a UAV for landing and perching upon a range of target structures.