bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigar en un mundo encantado: los aportes de las metodologías indígenas al quehacer etnográfico
Authors: Micarelli Giovanna
Published: January 2019

Tomando en consideración las metodologías de la Gente de Centro de la Amazonía colombiana, este ensayo busca sustituir una noción de la práctica etnográfica como conjunto de técnicas de extracción de datos, con un compromiso con otras prácticas cognitivas que acate los modos en que el conocimiento se produce y se valida localmente. A través del relato de dos proyectos de investigación indígena, el texto sugiere que el método moderno desencantado –con sus “entrevistas semi-estructuradas”, sus grupos focales y sus diseños de recolección de datos– es inadecuado para dar cuenta de un mundo en que todo habla y lo hace de manera inesperada. A la vez, la advertencia de los indígenas de vigilar los efectos del conocimiento sobre el mundo, nos obliga a asumir una actitud responsable hacia el mundo que el acto de conocer produce o puede producir. La pregunta es: ¿cómo estas metodologías que surgen del diálogo intercultural contribuyen a descolonizar el quehacer etnográfico?
Use of Irradiated Fracture Toughness Values in Nuclear Vessel and Component Design Specifications for Fitness-For-Service Analysis Using the Unified Curve Method
Authors: Ishaque Waleed
Published: January 2019

The American Society of Mechanical Engineers (ASME) Section III Rules for Construction of Nuclear Facility Components subsection NB-2331 Material for Vessels requires that the effects of irradiation shall be considered on material toughness properties in the core belt line region of the reactor vessel. The code also states that “the design specifications shall include additional requirements, as necessary, to ensure adequate fracture toughness for the service lifetime of the vessel.” In a design report of nuclear pressure vessel, the design and service loads do not include loads that are affected by fracture toughness of the material. However, in the cases of fitness-for-service assessment for component flaws (prevalent with age of component), irradiated material properties become highly relevant. An example of a fitness-for-service is that of a beyond design basis reactor vessel head drop accident in a pressurized water reactor with a nozzle junction flaw. As a case study, the critical size of a postulated external surface semielliptical circumferential crack in the combustion engineering three-loop pressurized water reactor nozzle–vessel junction is calculated using ansys Workbench (Academic version) with the applied impact load from the vessel head drop accident. Failure assessment diagrams for numerous crack depths and lengths were developed considering the fracture toughness properties of the irradiated reactor vessel steel. The mode I stress intensity results used in the failure assessment diagram were compared with the available finite element and the American Petroleum Institute (API) standard API 579 analytical solutions for validation, showing good agreement. From this case study, it is demonstrated that the effects of irradiation on fracture toughness become prominent at the same postulated crack size in the nozzle–vessel junction dispositioned as “safe” becomes “unsafe” in the fracture assessment diagram. Using the unified curve method, the irradiated fracture toughness data in design specification can be supplied so that it may be used in fitness-for-service analysis to account for component aging.
Diesel Fuel Multiple Injection Effects on Emission Characteristics of Diesel Engine Mixed Ammonia Gas Into Intake Air
Authors: Niki Yoichi , Nitta Yoshifuru , Sekiguchi Hidenori , Hirata Koichi
Published: January 2019

This study focuses NH3 as an alternative fuel for internal combustion engines, because NH3 is known as a H2 carrier and its combustion does not produce CO2 causing global warming. On the other hand, some reports show that unburned NH3 and N2O appear in exhaust gas, when NH3 is used as fuel for compression ignition or spark ignition engines. NH3 is toxic and N2O is one of the greenhouse gases. These emissions should not be emitted. These reports point out that exhaust gas after treatments and/or injection strategies can be effective to reduce these emissions. From our previous investigations, it was confirmed that NH3 and N2O were contained in the exhaust gas of a conventional diesel engine with NH3 gas mixed into the engine intake. In this study, NH3 combustion processes in the diesel engine were investigated from the experimental results. Based on the investigations, a pilot or postinjection was conducted to reduce emissions of NH3 and N2O. In this paper, first the experimental results of the combustion and exhaust emission characteristics on the conventional diesel engine with NH3 gas mixed into the engine intake are shown. NH3 and N2O emissions are then verified by analyzing the exhaust gas. Next, NH3 combustion processes in the diesel engine are considered from the experimental results to report on the effects of a pilot and postdiesel fuel injection on NH3 and N2O production processes. The experimental results suggest that the multiple diesel fuel injections would be one of the effective measures to reduce N2O and NH3 emissions on NH3 and diesel dual-fueled engine.
Effective Convergence Checks for Verifying Finite Element Stresses at Three-Dimensional Stress Concentrations
Authors: Beisheim J. R. , Sinclair G. B. , Roache P. J.
Published: January 2019

Current computational capabilities facilitate the application of finite element analysis (FEA) to three-dimensional geometries to determine peak stresses. The three-dimensional stress concentrations so quantified are useful in practice provided the discretization error attending their determination with finite elements has been sufficiently controlled. Here, we provide some convergence checks and companion a posteriori error estimates that can be used to verify such three-dimensional FEA, and thus enable engineers to control discretization errors. These checks are designed to promote conservative error estimation. They are applied to twelve three-dimensional test problems that have exact solutions for their peak stresses. Error levels in the FEA of these peak stresses are classified in accordance with: 1–5%, satisfactory; 1/5–1%, good; and <1/5%, excellent. The present convergence checks result in 111 error assessments for the test problems. For these 111, errors are assessed as being at the same level as true exact errors on 99 occasions, one level worse for the other 12. Hence, stress error estimation that is largely reasonably accurate (89%), and otherwise modestly conservative (11%).
Commodities and Rail Damage
Authors: Romero José A. , Otremba Frank , Lozano-Guzmán Alejandro A.
Published: January 2019

A simplified roll-plane model is proposed to assess the effect of the vertical position of the center of gravity of the body-cargo system, on the rail fatigue life. A set of assumptions are made to simplify the analysis, including neglecting the bogie’s dynamic contribution to the wheel-rail forces. Three performance measures are defined to assess the effect of different dedicated railway cars on the rail fatigue life, including the fourth-power law, the load dispersion, and the rail fatigue. The simulation results suggest that the vertical position of the center of gravity of the body-cargo set, severely affects the fatigue life of the railway material, with the two-stack car being the most aggressive. For example, twice as aggressive as the gondola car.
Thermo-Mechanical Performance Assessment of Selected Plates From MP-1 Low Power Experiments
Authors: Ozaltun Hakan , Rabin Barry H.
Published: January 2019

Monolithic plate-type fuel is a fuel form that is being developed for the conversion of high performance research and test reactors to low-enrichment uranium fuels. These fuel-plates are comprised of a high density, low enrichment, U-Mo alloy based fuel foil encapsulated in an aluminum cladding. To benchmark this new design, number of plates has been irradiated with satisfactory performance. As a part of continuing evaluation efforts, a set of plates covering range of operational parameters is scheduled to be tested during MP-1 irradiation experiments. It is necessary to evaluate the thermo-mechanical performance of plates during irradiation. For this, selected plates with distinct operational histories; covering low power, high power and high fission density were simulated. Fully coupled three-dimensional models of plates with a capability to evolve mechanical and thermal properties of constituent materials with irradiation time and burn-up were developed. The models input used projected parameters, including plate geometry, irradiation history and coolant conditions as input. The model output included temperature, displacement and stresses in the fuel, cladding and diffusion barrier. The fuel behavioral model considered inelastic behavior including volumetric swelling due to solid and gaseous products, irradiation induced creep, thermal expansion, conductivity degradation and plasticity. A visco-plastic behavioral model was used for the cladding that included thermal creep, irradiation hardening, growth due to fast neutrons and Mises plasticity. The plates were then simulated by using projected irradiation parameters. The resulting temperature, displacement and stress-strains were comparatively evaluated on the selected paths. The results were then compared with those of plates from previous RERTR experiments.
Sensitising Core Employability Skill Through Peer Assessment Approach
Authors: Jadeja Siddharthsinh , Wadhwa Sujata , Shukla Kapil , Ved Amit
Published: January 2019

Indian Engineering Education is transforming from traditional approach to Outcome based Education approach. The engineering education organizations are not only to change the assessment strategies, evaluation patterns and student’s success with evidences but also to satisfy the employer perspective to be developed among the students. This paper discuss about the how a peer assessment strategy has been implemented to enhance the engagement of the learner to foster the core employability skills. A three layered model has been adopted to measure the progress of the Learner and to collect the reflections on core employability skills. In the first year of the study, a larger mass (more than 300 students) has been assessed through this model, and for next two years they have been closely monitored for the growth. In the final year of their study, all the parameters have been compared and it has evidently improved the acquisition of essential required core employability skill at entry level Job.
3D-Printed PCM/HDPE Composites for Battery Thermal Management
Authors: Freeman Thomas B. , Nabutola Kaloki , Spitzer David , Currier Patrick N. , Boetcher Sandra K. S.
Published: January 2019

Phase-change materials (PCMs) are a useful alternative to more traditional methods of thermal management of Li-ion batteries in electric or hybrid-electric vehicles. PCMs are materials which absorb large amounts of latent heat and undergo solid-to-liquid phase change at near-constant temperature. The goal of the research is to experimentally investigate the thermal properties of a novel shape-stabilized PCM/HDPE composite extruded filament. The extruded filament can then be used in a 3D printer for custom PCM/HDPE shapes. The PCM used in the study is PureTemp PCM 42, which is an organic-based material that melts around 42° C. Four PCM/HDPE mixtures were investigated (all percentages by mass): 20/80, 30/70, 40/60, and 50/50. Preliminary findings include differential scanning calorimeter (DSC) measurements of melting temperature and latent heat as well as scanning electron microscope (SEM) pictures of filament composition.
Analysis of Melt Flows in an Electric Heating Furnace for Quartz Glass Synthesis
Authors: Ma Qianli , Fang Haisheng , Shang Chunli , Liu Zhongyi , Wang Jing
Published: January 2019

Flow patterns in molten quartz are highly related to the bubble transport and removal. Understanding the flow behavior in molten quartz is of great importance to the manufacture of high-purity quartz glass. In this paper, a numerical model is set up to simulate the flow field of molten quartz in a typical electric heating furnace. Natural convection and Marangoni convection are examined for their respective effects on the flow pattern of molten quartz. Different heater arrangements will change the flow field by varying temperature distributions. Top heating and bottom heating have the same vortex direction; while side heating induces an opposite direction to them. To improve the flow field in molten quartz, forced convection is introduced by crucible rotation. The influences of rotating speed of crucible on the flow field are studied in a wide range varying from 0 to 100 rad/s. With the increase of rotating speed, a reverse vortex to natural convection shows in molten quartz; and the velocity magnitude increase at a growing speed. To find out the optimal flow pattern for quartz glass manufacture, a qualitative analysis is presented on the reliance of bubble transport behavior on the convection modes. Based on the results, useful suggestions are provided towards increasing the bubble-free area of molten quartz and improving the quality of quartz glass.
An Integrated Method of FVM and SPH for Treating Melting Process of Quartz Ingot
Authors: Liu Zhongyi , Wang Jing , Ma Qianli , Fang Haisheng
Published: January 2019

The melting of quartz ingot undergoes solid-liquid phase transition, free-surface, large deformation and other complex flow. Thermal field is the fundamental driving factor during the process. Thus, new method of computing the complex flow and thermal field simultaneously needs to be developed. An integrated method of the finite volume method (FVM) and smoothed particle hydrodynamics (SPH) is proposed to combine the advantages of SPH in the complex flow and FVM in the thermal calculation. The method, a solver conjugate scheme, is implemented through the data exchange between the FVM sub-solver and the SPH sub-solver. The sub-solver of FVM focuses on thermal calculation, and SPH concentrates on complex flow with free-surface and large deformation. The inverse distance weighted (IDW) interpolation and spatial matching are employed to translate data from FVM to SPH and from SPH to FVM separately. The mechanism how the heater temperature affects the thermal field is investigated. The conclusion is that the increasing heater temperature affects the hot zone by raising the sidewalls temperature mainly, thus employing additional heating or cooling ways for controlling the temperature of the sidewalls is an efficient direction to optimize the hot zone design.
Thermodynamic Performance Study on Solar-Assisted SOFC - GT Distributed Energy System Fueled by Methanol
Authors: Hou Qinlong , Zhao Hongbin
Published: January 2019

This paper puts forward a new kind of SOFC - GT distributed energy system with methanol as fuel, through the absorption refrigeration (AR) and heat exchanger (HE) to recover the waste heat of GT. Based on thermodynamic analysis model, the performances, especially the exergy losses of the unit as well as its subsystems mainly including eight parts were obtained. The chemical energy of the fuel will directly be changed into electricity. Energy conversion efficiency can be as high as 85% above. The theoretical value has been paid attention by the researchers from all over the world. Comparative study in this paper, the simulation calculation and thermal performance analysis of the performance of two kinds of SOFC - GT is conducted. The results show that the total power generation efficiency of pure SOFC system, Case A and Case B are 19.28%, 55.79% and 52.26% respectively. The total thermal efficiency of Case A and B are 83.44 % and 82.79 % respectively. Additionally, the changing laws of total exergy loss, energy and exergy efficiency of integrated system at different loads also were studied. The results provide not only theory basis and scientific support for the design of the SOFC - GT distributed energy system with absorption refrigeration and heat exchanger recovering waste heat, but also a new scheme of energy saving and optimization for the units.
Design and Characteristic Analysis of Amalgamated Transparent Materials for Armor Structures Using Defeating Ballistic Experimentation
Authors: Attalla Emad , Jawad Badih , Grate Steve , Fernandez Vernon , Abro Sabah , Liu Liping
Published: January 2019

In armored platforms industry, the dominant material solution for ballistic transparency protection applications is relatively low-cost polycarbonate matrix glass. This research work aims to investigate the effects of geometrical designs of the amalgamated layers, engineering characteristics of the materials, and the interaction of both on the ballistic resistance of the transparent armor. The resulted models are used to analyze the strength feasibility of the material in the cost base. Ballistic measurements over a wide range of impact velocities including those well above the ballistic limits are deployed to the model. Under simple loading conditions, the polycarbonate matrix glass or ceramic can be regarded as elastic-brittle materials, however, when considering ballistic impacts the post-yield response of the ceramic becomes significant. A post-yield response model of ceramic materials is used for simulating the characteristics. The model incorporates the effect of damage on residual material strength and the resulting bulking during the compressive failure of the ceramic. A combination of relevant factors including the ability to dissipate ballistic energy and manufacturing processes was considered for the proper evaluation and selection of the armor. The model has been implemented into computer software to predict unsuccessful solutions and optimize the amalgamation with capabilities of defeating a wider range of ballistic impacts. The results will show more physical insight of the behavior and performance of the complex armor systems and provide guidelines/principles for the design and selection of the constituent materials.
A Vertical Seismometer With Build-in Retroreflector for Absolute Gravimetry
Authors: Guo Meiying , Wu Kang , Yao Jiamin , Qian Jin , Wang Lijun
Published: January 2019

A free-fall absolute gravimeter uses a Mach-Zehnder interferometer to track the free-falling object. Theoretically, it needs an inertial reference point, which is a reference retroreflector keeping static in inertial frame for an accurate absolute gravimetry. Practically, the reference retroreflector is always disturbed by the ground vibration. Traditionally, a vibration correction method with a broadband seismometer is used to reduce the effect of the ground vibration. The transfer function between the reference retroreflector and the seismometer is hypothesized as a proportional element with time delay. The difference between the hypothesized and the real transfer function limits the effect of the vibration correction. On this basis, a modified method, replacing the sensitive element of a seismometer with the reference retroreflector, is proposed. The motion of the reference retroreflector is measured directly by differential parallel plate capacitance detection. A closed-loop control circuit produces feedback voltage to make the reference retroreflector track the ground vibration. The feedback voltage represents the reference retroreflector’s motion directly. Experiments show the capacitance detecting circuit detects the displacement of the reference retroreflector relative to the ground with a resolution of 0.6 nm at 500 Hz. The acceleration resolution of the homemade vertical seismometer is about 10 mGal. The sensitivity of the seismometer is 316 V/g. The damp ratio of the homemade seismometer is little, and the natural frequency of the homemade seismometer is 104 Hz by analyzing the step response of the system. The bandwidth of the system is around 175 Hz. In the future, the homemade seismometer will be applied in absolute gravimeters for hostile measurement.
Thermal Stress Associated With Non-Fourier Heat Conduction in Femtosecond Laser Heating of Multilayer Metallic Films
Authors: Bag Swarup , Amin M. Ruhul
Published: January 2019

In the present work, the deformation behavior in metallic film subjected to ultra-short laser heating is investigated. Static thermo-elastic behavior is predicted for 100 nm thin film of either single layer or multiple layers. The temperature distribution is estimated from dual-phase lag non-Fourier heat conduction model. The maximum temperature after single pulse is achieved 730 K. The temperature profile for this pulse laser is used to compute elastic stress and distortion field following the minimization of potential energy of the system. In the present work, the simulation has been proposed by developing 3D finite element based coupled thermo-elastic model using dual phase lag effect. The experimental basis of transient temperature distribution in ultra-short pulse laser is extremely difficult or nearly impossible, the model results have been validated with literature reported thermal results. Since the temperature distribution due to pulse laser source varies with time, the stress analysis is performed in incremental mode. Hence, a sequentially coupled thermo-mechanical model is developed that is synchronized between thermal and mechanical analysis in each time steps of transient problem. The maximum equivalent stress is achieved 0.3 GPa. Numerical results show that the predicted thermal stress may exceeds the tensile strength of the material and may lead to crack or damage the thin film.
Improved Nonlinear Ultrasonic Guided Wave Damage Detection Using a Bandgap Meta-Surface
Authors: Tian Yiran , Shen Yanfeng
Published: January 2019

In this study, a kind of meta-surface was designed for the improvement of nonlinear ultrasonic guided wave detection by creating bandgaps. It is composed of aluminum alloy cylinders arranged in a periodic pattern bounded on an aluminum plate. By artificially adjusting the height of the cylinders, the meta-surface can open up bandgaps over desired frequency ranges. Guided waves within the bandgap cannot propagate through the meta-surface and will be mechanically filtered out. To perform non-destructive evaluation (NDE) of structural components with fatigue cracks, the guided waves generated by a piezoelectric wafer active sensor (PWAS) propagate into the structure, interact with the crack, acquire nonlinear features, and are picked up by the receiver PWAS. In an ideal case, the waves excited by the transmitter PWAS should only contain signals at the fundamental frequency. However, due to the inherent nonlinearity of the electronic instrument, the generated signals are often mixed with weak superharmonic components. And these inherent higher harmonic signals will adversely affect the identifiability of nonlinear characteristics in the sensing signals. The bandgap mechanism and the wave vector dispersion relationship of the meta-surface are investigated using the modal analysis of a finite element model (FEM) by treating a unit structural cell with the Bloch-Floquet boundary condition. In this way, the meta-surface is carefully designed to obtain bandgaps at the desired frequency ranges. Then, a FEM harmonic analysis of a chain of unit cells is performed to further explore the bandgap efficiency. Finally, a coupled field transient dynamic FEM is constructed to simulate the improved nonlinear ultrasonic guided wave active sensing procedure with the bandgap meta-surface. The proposed method possesses great potential for future SHM and NDE applications.
A Verified Non-Linear Regression Model for Elastic Stiffness Estimates of Finite Composite Domains Considering Combined Effects of Volume Fractions, Shapes, Orientations, Locations, and Number of Multiple Inclusions
Authors: Hage Ilige S. , Seif Charbel Y. , Hage Ré-Mi , Hamade Ramsey F.
Published: January 2019

A non-linear regression model using SAS/STAT (JMP® software; Proc regression module) is developed for estimating the elastic stiffness of finite composite domains considering the combined effects of volume fractions, shapes, orientations, inclusion locations, and number of multiple inclusions. These estimates are compared to numerical solutions that utilized another developed homogenization methodology by the authors (dubbed the generalized stiffness formulation, GSF) to numerically determine the elastic stiffness tensor of a composite domain having multiple inclusions with various combinations of geometric attributes. For each inclusion, these considered variables represent the inclusions’ combined attributes of volume fraction, aspect ratio, orientation, number of inclusions, and their locations. The GSF methodology’s solutions were compared against literature-reported solutions of simple cases according to such well-known techniques as Mori-Tanaka and generalized self-consistent type methods. In these test cases, the effect of only one variable was considered at a time: volume fraction, aspect ratio, or orientation (omitting the number and locations of inclusions). For experimental corroboration of the numerical solutions, testing (uniaxial compression) was performed on test cases of 3D printed test cubes.

The regression equation returns estimates of the composite’s ratio of normalized longitudinal modulus (E11) to that of the matrix modulus (Em) or E11/Em when considering any combination of all of the aforementioned inclusions’ variables. All parameters were statistically analyzed with the parameters retained are only those deemed statistically significant (p-values less than 0.05). Values returned by the regression stiffness formulation solutions were compared against values returned by the GSF formulation numerical and against the experimentally found stiffness values. Results show good agreement between the regression model estimates as compared with both numerical and experimental results.
Statistically Validated and Optimized Tabu Search Estimation of Cutting Tool Life in Turning
Authors: Hage Ré-Mi , Hage Ilige , Ghnatios Chady , Hamade Ramsey
Published: January 2019

In machining, tool life is the measure that gives manufacturers fundamental indications on useful tool utilization. In this work, investigated is the influence of turning parameters such as spindle speed, depth of cut, and tool feed on tool life. Literature-reported studies typically utilize Taguchi orthogonal array method for experimental design while tool-wear estimates utilized mathematical expressions by means ofregression analysis. In this work, the authors combine a tabu search (TS) algorithm with the traditional regression analysis (REG) to introduce a combined (TS-REG) scheme that minimizes a weighted sum of the outputs that represent different measures of turning quality. The aim in this paper is to show that the proposed novel combination TS-REG reaches better fitted models in minimal time as compared with other statistical methods. Tool life estimates are plotted versus different turning process parameters. The results that represent optimized tool life of the process are compared to literature reported experimental values. Good correlations confirm desirable efficiency and the ability of the TS-REG method in estimating tool life in turning. In order to determine statistical significance decisions, both p-values and mean absolute percentage error (MAPE: mean of the relative absolute error) were employed. The TS-REG method aids in determining the optimal set of parameters for any combination of the weighting factors resulting in improved tool life.
Experimental Study of the Sustainability of a Renewable-Energy-Driven Residential System With Heating Loads
Authors: Kakizaki Takao , Hirano Kosuke , Morohashi Norio , Oguma Masahito
Published: January 2019

The sustainability of an energy-independent system with a relatively large heating load and that is driven by multiple renewable energy sources such as a photovoltaic battery and a biofuel generator has been investigated. The utilization of renewable energy has become one of the most important areas of interest for residential houses, as seen in zero energy house trends. In particular, technologies for energy-independent residential houses that can be categorized as off-grid systems have gained importance. In this paper, the design concept and the detail of the constructed pilot scale test system comprising a photovoltaic power (PV) generator and a biofuel power generator (BFG) are explained. Experimental results prove that continuous system operation is possible based on an effective control of these multiple renewable energy sources, even for relatively large heating loads. The results also imply that usage of multiple-source renewable energy is effective for the sustainable operation of an energy-independent residential house. Moreover, optimizing the energy consumption of the energy-independent system with heating is discussed. Here, mixed integer linear programming has been applied to the system driven by multiple renewable energy sources to optimize the sustainable operation of the system. The simulation results show that it is possible to reduce the cost incurred on biofuel by about 40% as compared with that of the system driven only by biofuel energy. Consequently, multiple sources of renewable energy are effective for the sustainable operation of an energy-independent residential house even with relatively large heating loads.
Ecological Performance of a Generalized Radiative System Light-Driven Engine (LDE) With [A] ⇌ [B] Reacting System Improved by Controlling Piston Motion
Authors: Feng Huijun , Ma Kang , Chen Lingen , Xia Shaojun
Published: January 2019

This paper introduces the ecological criterion (EC) into the optimal configuration problem of an irreversible light-driven engine (LDE) under the assumption that heat transfer (HT) between the working fluid (WF) and the surroundings is presumed to abide by the generalized radiative heat transfer law (HTL) [q ∝ Δ(Tn) ]. The WF is made up of the reacting system [A] ⇌ [B] , and the primary irreversibilities corresponding to the practical engine are the piston friction and heat conduction with the WF operating at a nonzero rate and far from equilibrium. Meantime, in order to obtain the optimal paths (OPs) for maximum ecological performance (EP) of the engine, the optimal control theory (OCT) is utilized in this paper. Numerical calculations of the OPs at maximum EP with linear phenomenological (n = −1), Newton’s (n = 1) and radiative (n = 4) HTLs are performed. The results derived by maximum EP are compared with those derived by maximum work output (WO) and minimum entropy generation (EG) as well as different HTLs. The results obtained in this paper indicate that utilizing the maximum EC as the design objective could effectively accomplish the EG reduction with a little decrease in the WO. Moreover, the OPs for maximum EP with different HTLs are quite different.
Additive Manufacturing of Polymer Nanocomposites With In-Situ Strain Sensing Capability
Authors: Abshirini Mohammad , Charara Mohammad , Liu Yingtao , Saha Mrinal C. , Altan M. Cengiz
Published: January 2019

This paper presents the additive manufacturing of electrically conductive polydimethylsiloxane (PDMS) nanocomposites for in-situ strain sensing applications. A straight line of pristine PDMS was first 3D printed on a thin PDMS substrate using an in-house modified 3D printer. Carbon nanotubes (CNTs) were uniformly sprayed on top of uncured PDMS lines. An additional layer of PDMS was then applied on top of CNTs to form a thin protective coating. The 3D printed PDMS/CNT nanocomposites were characterized using a scanning electron microscope (SEM) to validate the thickness, CNT distribution, and microstructural features of the sensor cross-section. The strain sensing capability of the nanocomposites was investigated under tensile cyclic loading at different strain rates and maximum strains. Sensing experiments indicate that under cyclic loading, the changes in piezo resistivity mimic, both, the changes in the applied load and the measured material strain with high fidelity. Due to the high flexibility of PDMS, the 3D printed sensors have potential applications in real-time load sensing and structural health monitoring of complex flexible structures.
Fabrication, Optimization, and Characterization of PDMS/CNF Nanocomposite Sensor Arrays
Authors: Luo Wenyuan , Liu Yingtao , Saha Mrinal , Patterson Steven , Robison Thomas
Published: January 2019

This paper presents the fabrication, optimization, and characterization of in-situ pressure sensor arrays using polydimethylsiloxane (PDMS) and carbon nanofibers (CNFs) nanocomposites. We first synthesize and characterize the nanocomposites to identify the optimal material formulation and fabrication procedure. Structural optimization algorithms and finite element method are employed to optimize the geometries of sensors. Pressure sensing units in cylinder and conical shapes are fabricated using the optimized material formulation and geometries. Two prototypes of sensors arrays are assembled and tested under different pressure load conditions. The long term sensor performance is validated using cyclic compression tests.
Low-Cost Wi-Fi Navigation of Smart Wheelchairs
Authors: Batayneh Wafa M. , Hatamleh Khaled S. , Nusayr Amjad A. , Alquraan Rama , Al-Khaleel Aseel , Batainah Ahmad
Published: January 2019

This paper presents the design and implementation of a low-cost and reliable wireless motion control system for conventional electric wheelchairs. The presented work aims to enhance the mobility of handicapped and elderly wheelchair users by utilizing a mobile application to control the motion of their unattained wheelchairs. The designed system takes into consideration cost, weight, a range of operation, ease of use, and implementation. The conventional electric wheelchair is equipped with a motorized front wheel steering mechanism. In addition, it is equipped with a Wi-Fi module to support remote motion control via a specially designed Android mobile application called “Android Application For NavigAtioN”; AAFNAN for short. Experimental testing of the prototype showed successful remote motion control and ease of use.
Design and Integration of High Temperature Latent Heat Thermal Energy Storage for High Power Levels
Authors: Johnson Maike , Hachmann Bernd , Dengel Andreas J. , Fiß Michael , Hempel Matthias , Bauer Dan
Published: January 2019

A latent heat thermal energy storage unit is being integrated into a heat- and power cogeneration plant in Saarland, Germany. This storage unit system will act as an intermediate backup to a heat recovery steam generator and gas turbine and is therefore situated in parallel to this unit, also between the feedwater pumps and the steam main. The steam required is superheated, with a nominal thermal power of 6 MW. The storage unit needs to provide steam for at least 15 minutes, resulting in a minimum capacity of 1.5 MWh. Integration of this storage unit will increase efficiency and decrease fossil fuel use by reducing the use of a conventional backup boiler, while maintaining the steam supply to the customer.

The detailed design and a partial build of the storage unit has to-date been successfully concluded, as well as system design and build. Hot and cold commissioning of the storage unit, including filling of the storage unit, will commence following the completion of the storage unit. With the integration of this storage unit, fossil fuel use will be reduced in this power plant. Additionally, the production of superheated steam at a high power level in a latent heat storage unit and a comparison with simulation tools will be possible. This project includes the design, build, commissioning and testing of the storage unit. The paper discusses the detailed design of the storage and system, including the simulations of the system integration.
An Elastothermoviscoplasticity Anisotropic Damage Model for Short Fiber Reinforced Polymer Composites
Authors: He Ge , Liu Yucheng , Bammann D. J. , Horstemeyer M. F.
Published: January 2019

By using the internal state variable (ISV) theory (Horstemeyer and Bammann, 2010), we developed a finite deformation anisotropic and temperature dependent constitutive model to predict elastoviscoplasticity and progressive damage behavior of short fiber reinforced polymer (SFRP) composites. In this model, the SFRP is considered as a simple anisotropic equivalent medium (lamina), and the rate dependent plastic behavior of the SFRP is captured with the help of three physically-based ISVs. A second-order damage tensor is introduced to describe the anisotropic damage state of the SFRP and the tensorial damage evolution equations are used based on the damage mechanism of micro voids/cracks nucleation, growth and coalescence. The constitutive model developed herein arises employing standard postulates of continuum mechanics with the kinematics, thermodynamics, and kinetics being internally consistent. The developed model is then calibrated to a 35 wt% glass fiber reinforced polyamide 66 (PA66GF-35) for future numerical analyses.
Acoustic Radiation of Axially Stepped-Thickness Piezoelectric Cylindrical Shells
Authors: Meshkinzar Ata , Al-Jumaily Ahmed M.
Published: January 2019

In this work, a new design method is proposed to intensify the focused acoustic field generated inside a circular cylindrical piezoelectric transducer. The proposed design incorporates a stepped-thickness piezoelectric transducer which has thickness variations along the length. The location of these steps are identified based on the mode shape analysis of a uniform-thickness tube. Once the step locations are identified, two cases are considered with internal and external steps. Acoustic radiation characteristics and mode shapes are compared with the uniform-thickness shell. All the investigations are performed using ANSYS. An increase in the sound pressure level is obtained utilizing the stepped-thickness tube at the same input power.
Finite Element Simulation of Cracks Propagation in Rolling Contact Applications With and Without Coating Applied in Industrial Field
Authors: Nehme Gabi , Al Esber Monzer
Published: January 2019

The aim of this study is mainly about preventing crack initiation and propagation in rolling contact under moderate and extreme loading through coating technology using finite element simulation and design of experiment (DOE) optimization techniques. Several applications of rolling contact were conducted and the parameters related to rollers’ materials, coating, temperature, and loads were investigated.

M50 steels (0.8C-4.2Cr-4.3Mo-1V wt.%) and 100CrMnMo8 steel (1.0C-2.0Cr-0.5Mo-1.0Mn-0.5Si wt.%) were analyzed with and without titanium nitride (TiN), zirconium nitride (ZrN) and tungsten carbide (WC) coatings under different temperature and loading conditions. Results showed that cracks propagation were limited to extreme load when using coating technology. A fully three-dimensional finite element model showed the Von Mises stresses and displacement under different temperatures. Findings confirmed that coating will enhance the lifetime of rollers and inhibit cracks and plastic deformation with better contribution from TiN under extreme pressure if compared to WC. DOE optimization of the parameter used in this study correlate closely with previous experiments and provided a solid conclusion of the best combination in rolling contact applications.
The Effect of PTFE Membrane Properties on Vacuum Membrane Distillation Module Performance
Authors: Usta Mustafa , Krysko Robert M. , Anqi Ali E. , Alshwairekh Ahmed M. , Oztekin Alparslan
Published: January 2019

This study investigates the effect of membrane properties — porosity, membrane thickness, and pore radius — on the performance of vacuum membrane distillation (VMD) process by achieving computational fluid dynamics (CFD) simulations on a three-dimensional domain of interest at fixed flow properties. The finite volume method (FVM) is adopted to solve momentum, solute mass transport, and energy equations in the feed channel. To accurately predict the rate of water vapor diffused through the membrane by Knudsen and viscous diffusion mechanism, local concentration, temperature, and flux are coupled at the membrane surfaces. In accordance with the flux, corresponding gradients for temperature and concentration are applied at the membrane boundaries. Since there is a strong coupling of flow properties at the membrane surface, the employed model is validated against an experimental study and further used to characterize the effect of PTFE membrane properties on permeate flux, temperature polarization, and concentration polarization. We found that different set of membrane design parameters substantially changes the total mass flux. The contribution of both viscous and Knudsen mechanism is comparable and, as such, prevents us neglecting neither of them. The temperature and concentration polarization are even more undesirable level for the larger pore sizes.
The Effect of Porous Support Layer in Forward Osmosis Membranes: A Computational Fluid Dynamics Simulation
Authors: Alshwairekh Ahmed M. , Alghafis Abdullah A. , Usta Mustafa , Alwatban Anas M. , Krysko Robert , Oztekin Alparslan
Published: January 2019

Computational fluid dynamics (CFD) simulations are conducted to study the transport phenomena in spiral wound membranes (SWM) within a Forward Osmosis (FO) module. The effect of the porous layer on the membrane performance is examined. Simulations are prepared for three different porous layer thicknesses by having the porous layer facing the draw channel, a mode known as AL-FS (active layer facing feed solution). In the current study, a Reynolds number range from 2 to 500 is considered. The Navier-Stokes and the mass transport equations are used to obtain the velocity, pressure and concentration fields in the flow channels. The local osmotic pressure and the membrane properties are used to calculate the water permeation over the membrane surface. The membrane is considered as a semipermeable functional surface of zero thickness. The effect of the porous layer is included in the flux model, but the flow and concentration fields in the porous layer are not resolved. The results suggest that increasing the streamwise velocity decreases the level of the external concentration polarization on both sides of the membrane which in turn leads to higher water flux through the membrane. Also, the existence of the porous layer reduced the membrane performance. The water flux didn’t improve much with increasing streamwise velocity at the same porous layer thickness. The suction velocity over the membrane starts at a high value at the inlet of the draw channel and decreases until reaching the outlet of the draw channel then it starts to increase slightly from the effect of the inlet of feed solution. Moreover, by increasing the net osmotic pressure difference, the water flux exhibited a non-linear increase.
Comparative Study of Post-Buckling Load Redistribution in Stiffened Aircraft Panel With and Without Material Nonlinearity
Authors: Aydin Enes , Kayran Altan
Published: January 2019

In this article, a comparative study is presented on the post-buckling load redistribution in stiffened aircraft panels modeled with and without material nonlinearity. In the first part of the study, a baseline stiffened panel is generated for further investigation of the material nonlinearity on the post-buckling behavior and on the effective width of the stiffened panel. In this respect, a stiffener section which provides classical clamped edge condition is designed by matching the compression buckling coefficient determined by the finite element analysis closely with the analytically determined buckling coefficient of the clamped edge panel. Post-buckling analysis of the stiffened panel is then performed utilizing linear and nonlinear material models in the finite element analysis and the effect of material plasticity on the post-buckling behavior of the panel is ascertained. The load distribution in the stiffened panel is investigated just before the buckling of the panel and before the collapse of the panel in the post-buckled stage. The effective widths of the panel are calculated before the collapse of the panel using the load distributions determined by the finite element analyses of the panel models with and without material nonlinearity and comparisons are made with the effective width calculated by the classical effective width formulation. It is shown that material nonlinearity accounts for higher effective width and in general the classical empirical approach gives the smallest effective width.
An Eight-Passage Serpentine Design for Negating Coriolis Force Effect on Heat Transfer
Authors: Singh Prashant , Ekkad Srinath
Published: January 2019

Gas turbine blades are subjected to elevated heat loads due to high temperature gases exiting the combustor section. Complex internal and external cooling techniques are employed in blades to protect them from the hot gases. Blades are equipped with internal cooling passages which are connected to each other by 180-degree bends. The coolant flow is typically from blade root-to-tip and blade tip-to-root. Further, since the blades are subjected to rotation, the fluid dynamics and heat transfer inside these serpentine channels get modified. Under the influence of Coriolis force and centrifugal buoyancy force induced by rotation, the heat transfer for radially outward flow enhances on the trailing side (pressure side) and reduces on the leading side (suction side). A reverse trend in heat transfer is observed for radially inward flow. This heat transfer trend leads to non-uniform blade temperature leading to increase in thermal-stresses. Prolonged operation under critical thermal stresses can lead to significant damage and increase in maintenance and overhaul. This paper presents a novel 8-passgae serpentine design, where passages are arranged along the chord of the blade which has similar heat transfer coefficient distribution on both leading and trailing walls. Detailed heat transfer coefficients were measured using transient liquid crystal thermography under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 14264 to 83616 under stationary conditions. Rotation experiments were carried out at Rotation number of 0.05. Heat transfer enhancement levels of approximately two times the Dittus-Boelter correlation (for developed flow in smooth tubes) were obtained under stationary conditions. Under rotating conditions, we found that the heat transfer levels on the leading and trailing sides were similar to each other and with the stationary condition. Some differences in heat transfer were observed on local level, when rotation cases were compared against the stationary cases.