cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.6007904.v1
title: Run time Assessment for Gas Turbine Performance Simulation

description: ABSTRACT: This article describes the run time characteristics of a gas turbine performance simulation using different solvers and components off-design performance database formats. Two different nonlinear systems of equation solvers, Newton-Raphson's and Broyden's, and two different formats of compressor and turbine off-design performance database (maps), tabulated values and fitted surface equations, were compared. Based on the results it is then possible to trade off and select the most appropriate combination of solver and component map type for the gas turbine performance simulation for real-time application.
DOI: 10.6084/m9.figshare.6083780
title: Performance Prediction of Microwave Absorbers Based on POMA/Carbon Black Composites in the Frequency Range of 8.2 to 20 GHz

description: ABSTRACT: This paper presents a comparative study involving experimental and numerical behaviors of radar absorbing materials (RAM), based on conducting composites of poly(o-methoxyaniline) (POMA) and carbon black (CB). Samples of POMA/CB in epoxy resin matrix were prepared. First, these samples were experimentally characterized by electric permittivity and magnetic permeability measurements in the frequency range of 8.2 to 12.4 GHz. Afterwards, a linear extrapolation of these electromagnetic parameters until 20 GHz was carried out. These amounts were used as parameters for a set of simulations, developed from numerical implementation of theoretical predictions. The main advantage of the performed simulations is to know the behavior of the POMA/CB/epoxy resin as RAM in a wide range of frequencies (8.2-20 GHz), previously to the experimental work. The validation of the simulations with experimental reflection loss measurements showed a good fit and allowed predicting the material behavior as RAM. The results show that the studied RAM presents good return loss values in different frequencies, for example, -32 dB (~99.95% of absorption) at 14.6 GHz and -18 dB at 19.2 GHz, for samples with 7 and 9 mm-thickness values, respectively. The simulation tool used in this study was adequate to optimize the RAM production, contributing to the reduction of development costs and processing time of this kind of material.
DOI: 10.6084/m9.figshare.6083780.v1
title: Performance Prediction of Microwave Absorbers Based on POMA/Carbon Black Composites in the Frequency Range of 8.2 to 20 GHz

description: ABSTRACT: This paper presents a comparative study involving experimental and numerical behaviors of radar absorbing materials (RAM), based on conducting composites of poly(o-methoxyaniline) (POMA) and carbon black (CB). Samples of POMA/CB in epoxy resin matrix were prepared. First, these samples were experimentally characterized by electric permittivity and magnetic permeability measurements in the frequency range of 8.2 to 12.4 GHz. Afterwards, a linear extrapolation of these electromagnetic parameters until 20 GHz was carried out. These amounts were used as parameters for a set of simulations, developed from numerical implementation of theoretical predictions. The main advantage of the performed simulations is to know the behavior of the POMA/CB/epoxy resin as RAM in a wide range of frequencies (8.2-20 GHz), previously to the experimental work. The validation of the simulations with experimental reflection loss measurements showed a good fit and allowed predicting the material behavior as RAM. The results show that the studied RAM presents good return loss values in different frequencies, for example, -32 dB (~99.95% of absorption) at 14.6 GHz and -18 dB at 19.2 GHz, for samples with 7 and 9 mm-thickness values, respectively. The simulation tool used in this study was adequate to optimize the RAM production, contributing to the reduction of development costs and processing time of this kind of material.
DOI: 10.6084/m9.figshare.6083789
title: Aircraft Preventive Maintenance Data Evaluation Applied in Integrated Product Development Process

description: ABSTRACT: Initial Maintenance Review Board Report (MRBR) uses in service operation experience as a reference to define maintenance tasks intervals. However, in general, there is no structured data to compare systems performance and provide useful information to the analysts' decision-making. Even when engineering judgment is based on certification process, structural design, components intrinsic reliability and so on, the analysts responsible for maintenance tasks definitions tend to choose rather conservative proposals. This article presents a method to optimize preventive maintenance tasks intervals and use structured data based on interval optimization process to define maintenance intervals to those of similar systems under development. The method has been applied in an aircraft manufacturing company using current operation database after regulatory authorities' approval. As a result, it has been feasible to propose to the selected system, a maintenance task interval 100% higher than the one applicable to a similar system under operation.
DOI: 10.6084/m9.figshare.6083789.v1
title: Aircraft Preventive Maintenance Data Evaluation Applied in Integrated Product Development Process

description: ABSTRACT: Initial Maintenance Review Board Report (MRBR) uses in service operation experience as a reference to define maintenance tasks intervals. However, in general, there is no structured data to compare systems performance and provide useful information to the analysts' decision-making. Even when engineering judgment is based on certification process, structural design, components intrinsic reliability and so on, the analysts responsible for maintenance tasks definitions tend to choose rather conservative proposals. This article presents a method to optimize preventive maintenance tasks intervals and use structured data based on interval optimization process to define maintenance intervals to those of similar systems under development. The method has been applied in an aircraft manufacturing company using current operation database after regulatory authorities' approval. As a result, it has been feasible to propose to the selected system, a maintenance task interval 100% higher than the one applicable to a similar system under operation.
DOI: 10.6084/m9.figshare.6083777
title: An Evaluation of the Dielectric Barrier Discharge Treatment on the Mechanical, Structural and Morphological Properties of Carbon Fibers

description: ABSTRACT: Carbon fibers (CFs) have been widely applied in the manufacture of polymeric composites. The mechanical properties of these composites depend on the adhesion in the matrix/CF interface. Since the CFs have poor adhesion properties, a surface treatment of the CFs becomes necessary. The plasma process used in this work was the dielectric barrier discharge (DBD). The DBD treatment of twill weave carbon fibers (2×2) was performed during 2.0; 5.0; 7.5 and 10.0 minutes. CF/polypropylene (PP) composites were produced by hot pressing method. The surface morphology, structure and mechanical properties of CFs were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, interlaminar shear test (ILSS) and dynamical mechanical analysis (DMA), respectively. SEM images show great changes on the CF surface after the treatment, AFM results show that the fiber treated for 2.0 min exhibited the highest roughness and Raman spectra revealed that the carbon fiber crystalline structure did not change after the treatment. The ILSS and DMA results show an increase of the mechanical strength and no major change in the glass temperature of the composites after the DBD treatment, respectively. Some results were compared to those obtained in our previous study, in which the plain weave fiber (1×1) was evaluated.
DOI: 10.6084/m9.figshare.6083777.v1
title: An Evaluation of the Dielectric Barrier Discharge Treatment on the Mechanical, Structural and Morphological Properties of Carbon Fibers

description: ABSTRACT: Carbon fibers (CFs) have been widely applied in the manufacture of polymeric composites. The mechanical properties of these composites depend on the adhesion in the matrix/CF interface. Since the CFs have poor adhesion properties, a surface treatment of the CFs becomes necessary. The plasma process used in this work was the dielectric barrier discharge (DBD). The DBD treatment of twill weave carbon fibers (2×2) was performed during 2.0; 5.0; 7.5 and 10.0 minutes. CF/polypropylene (PP) composites were produced by hot pressing method. The surface morphology, structure and mechanical properties of CFs were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, interlaminar shear test (ILSS) and dynamical mechanical analysis (DMA), respectively. SEM images show great changes on the CF surface after the treatment, AFM results show that the fiber treated for 2.0 min exhibited the highest roughness and Raman spectra revealed that the carbon fiber crystalline structure did not change after the treatment. The ILSS and DMA results show an increase of the mechanical strength and no major change in the glass temperature of the composites after the DBD treatment, respectively. Some results were compared to those obtained in our previous study, in which the plain weave fiber (1×1) was evaluated.
DOI: 10.6084/m9.figshare.7518158
title: Analytical Solution for Optimal Low-Thrust Limited-Power Transfers Between Non-Coplanar Coaxial Orbits

description: ABSTRACT: In this paper, an analytical solution for time-fixed optimal low-thrust limited-power transfers (no rendezvous) between elliptic coaxial non-coplanar orbits in an inverse-square force field is presented. Two particular classes of maneuvers are related to such transfers: maneuvers with change in the inclination of the orbital plane and maneuvers with change in the longitude of the ascending node. The optimization problem is formulated as a Mayer problem of optimal control with the state defined by semi-major axis, eccentricity, inclination or longitude of the ascending node, according to the class of maneuver considered, and a variable measuring the fuel consumption. After applying Pontryagin's maximum principle and determining the maximum Hamiltonian, short periodic terms are eliminated through an infinitesimal canonical transformation. The new maximum Hamiltonian resulting from this canonical transformation describes the extremal trajectories for long duration transfers. Closed-form analytical solution is then obtained through Hamilton-Jacobi theory. For long duration maneuvers, the existence of conjugate points is investigated through the Jacobi condition. Simplified solution is determined for transfers between close orbits. The analytical solution is compared to the numerical solution obtained by integration of the canonical system of differential equations describing the extremal trajectories for some sets of initial conditions. Results show a great agreement between these solutions for the class of maneuvers considered in the analysis. The solution of the two-point boundary value problem of going from an initial orbit to a final orbit, based on the analytical solution, is also discussed.
DOI: 10.6084/m9.figshare.7518158.v1
title: Analytical Solution for Optimal Low-Thrust Limited-Power Transfers Between Non-Coplanar Coaxial Orbits

description: ABSTRACT: In this paper, an analytical solution for time-fixed optimal low-thrust limited-power transfers (no rendezvous) between elliptic coaxial non-coplanar orbits in an inverse-square force field is presented. Two particular classes of maneuvers are related to such transfers: maneuvers with change in the inclination of the orbital plane and maneuvers with change in the longitude of the ascending node. The optimization problem is formulated as a Mayer problem of optimal control with the state defined by semi-major axis, eccentricity, inclination or longitude of the ascending node, according to the class of maneuver considered, and a variable measuring the fuel consumption. After applying Pontryagin's maximum principle and determining the maximum Hamiltonian, short periodic terms are eliminated through an infinitesimal canonical transformation. The new maximum Hamiltonian resulting from this canonical transformation describes the extremal trajectories for long duration transfers. Closed-form analytical solution is then obtained through Hamilton-Jacobi theory. For long duration maneuvers, the existence of conjugate points is investigated through the Jacobi condition. Simplified solution is determined for transfers between close orbits. The analytical solution is compared to the numerical solution obtained by integration of the canonical system of differential equations describing the extremal trajectories for some sets of initial conditions. Results show a great agreement between these solutions for the class of maneuvers considered in the analysis. The solution of the two-point boundary value problem of going from an initial orbit to a final orbit, based on the analytical solution, is also discussed.
DOI: 10.6084/m9.figshare.7510706
title: Proper Orthogonal Decomposition and Spectral Analysis of a Wall-Mounted Square Cylinder Wake

description: ABSTRACT: The flow patterns over a finite square cylinder of aspect ratio of 3 were analyzed experimentally in a subsonic wind tunnel using the time-resolved particle image velocimetry (TR - PIV) techniques. The near wake flow structures and vortex shedding characteristics were investigated using mean flow analysis, spectral analysis and proper orthogonal decomposition (POD). The cylinders were fixed on a elliptical leading edge flat plate, creating a boundary layer which interacted with the cylinder wake. The 2D PIV measurements were conducted at a low horizontal plane, z/h = 0.3, to investigate possible boundary layer interactions. Due to the complexity of the phenomena, the flow was characterized both in terms of average behavior and time-resolved velocity fields. Both symmetrical and anti-symmetrical vortices structures occur in the cylinder wake, which can be identified based on the coefficients of the first four POD modes. The results indicated that the alternating Karman vortex structures are dominant, described by the first two POD modes.
DOI: 10.6084/m9.figshare.7510706.v1
title: Proper Orthogonal Decomposition and Spectral Analysis of a Wall-Mounted Square Cylinder Wake

description: ABSTRACT: The flow patterns over a finite square cylinder of aspect ratio of 3 were analyzed experimentally in a subsonic wind tunnel using the time-resolved particle image velocimetry (TR - PIV) techniques. The near wake flow structures and vortex shedding characteristics were investigated using mean flow analysis, spectral analysis and proper orthogonal decomposition (POD). The cylinders were fixed on a elliptical leading edge flat plate, creating a boundary layer which interacted with the cylinder wake. The 2D PIV measurements were conducted at a low horizontal plane, z/h = 0.3, to investigate possible boundary layer interactions. Due to the complexity of the phenomena, the flow was characterized both in terms of average behavior and time-resolved velocity fields. Both symmetrical and anti-symmetrical vortices structures occur in the cylinder wake, which can be identified based on the coefficients of the first four POD modes. The results indicated that the alternating Karman vortex structures are dominant, described by the first two POD modes.
DOI: 10.6084/m9.figshare.7518152.v1
title: Investigating Space Radiation Environment Effects on Communication of Razaksat-1

description: ABSTRACT: This study attempted to identify whether space radiation sources could have affected the communication on RazakSAT-1 that was orbiting in a Low Earth Orbit-Near Equatorial (LEO-NEqO). Data on galactic cosmic rays (GCR), trapped protons, trapped electrons, and solar energetic particles (SEPs) obtained from Space Environment Information System (SPENVIS) are considered. The effects of these radiation sources are analyzed using the linear energy transfer (LET), total ionizing dose (TID), and solar cell degradation. Flux data from National Oceanic and Atmospheric Administration (NOAA) 15, 16, and 17 satellites, and the geomagnetic conditions during the time when RazakSAT-1's missing is also analyzed. Another two satellites, Satélite de Coleta de Dados (SCD-2) and Advanced Land Observation Satellite (ALOS), are compared with the performance of RazakSAT-1. Results showed that GCR dominated at a high energy range of 103 MeV and above in the LEO-NEqO, whereas the energies of the trapped protons and trapped electrons are less than 400 MeV and 4 MeV, respectively. There are no SEPs estimated during the mission period (2009 - 2011). Based on the SPENVIS, SCD-2 and ALOS are more exposed to higher radiation damage than RazakSAT-1. Thus, an analysis of space radiation environment effects on the RazakSAT-1 communication lost after one year of operation will be discussed further, as a platform to find the best strategy for future missions.
DOI: 10.6084/m9.figshare.7518152
title: Investigating Space Radiation Environment Effects on Communication of Razaksat-1

description: ABSTRACT: This study attempted to identify whether space radiation sources could have affected the communication on RazakSAT-1 that was orbiting in a Low Earth Orbit-Near Equatorial (LEO-NEqO). Data on galactic cosmic rays (GCR), trapped protons, trapped electrons, and solar energetic particles (SEPs) obtained from Space Environment Information System (SPENVIS) are considered. The effects of these radiation sources are analyzed using the linear energy transfer (LET), total ionizing dose (TID), and solar cell degradation. Flux data from National Oceanic and Atmospheric Administration (NOAA) 15, 16, and 17 satellites, and the geomagnetic conditions during the time when RazakSAT-1's missing is also analyzed. Another two satellites, Satélite de Coleta de Dados (SCD-2) and Advanced Land Observation Satellite (ALOS), are compared with the performance of RazakSAT-1. Results showed that GCR dominated at a high energy range of 103 MeV and above in the LEO-NEqO, whereas the energies of the trapped protons and trapped electrons are less than 400 MeV and 4 MeV, respectively. There are no SEPs estimated during the mission period (2009 - 2011). Based on the SPENVIS, SCD-2 and ALOS are more exposed to higher radiation damage than RazakSAT-1. Thus, an analysis of space radiation environment effects on the RazakSAT-1 communication lost after one year of operation will be discussed further, as a platform to find the best strategy for future missions.
DOI: 10.6084/m9.figshare.6235040
title: Minimum Activation Power of a Passive UHF RFID Tags: a Low Cost Method

description: ABSTRACT: RFID is an automatic contactless identification method based on radio frequency (RF). The reading process depends of the power of electromagnetic signal received by a tag. Thus an accurate characterization of RFID tags is crucial for early adopter in aerospace industry. The present study shows the preliminary approach to characterize the reading distance for UHF RFID passive tag from the low-cost application test deployment.
DOI: 10.6084/m9.figshare.6235040.v1
title: Minimum Activation Power of a Passive UHF RFID Tags: a Low Cost Method

description: ABSTRACT: RFID is an automatic contactless identification method based on radio frequency (RF). The reading process depends of the power of electromagnetic signal received by a tag. Thus an accurate characterization of RFID tags is crucial for early adopter in aerospace industry. The present study shows the preliminary approach to characterize the reading distance for UHF RFID passive tag from the low-cost application test deployment.
DOI: 10.6084/m9.figshare.7511648
title: Modeling and Analysis of a LOX/Ethanol Liquid Rocket Engine

description: ABSTRACT This work studies the performance and dry mass of the under development LOX/Ethanol L75 liquid rocket engine. To this end, an object-oriented program written in C++ was developed. The program is intended to be versatile and easily extensible in order to analyze different configurations of liquid rocket engines. The UML (Unified Modeling Language) tool is used to model the architecture of the codes. UML diagrams help to visualize the code structure and the communication between objects, enabling a high degree of abstraction. The cryogenics Vulcain and HM7B engines power cycles along with the staged-combustion SSME engine perform the verification of the codes. Finally, the influence of changes in design parameters on the performance and dry mass of the L75 rocket engine is analyzed.
DOI: 10.6084/m9.figshare.7511648.v1
title: Modeling and Analysis of a LOX/Ethanol Liquid Rocket Engine

description: ABSTRACT This work studies the performance and dry mass of the under development LOX/Ethanol L75 liquid rocket engine. To this end, an object-oriented program written in C++ was developed. The program is intended to be versatile and easily extensible in order to analyze different configurations of liquid rocket engines. The UML (Unified Modeling Language) tool is used to model the architecture of the codes. UML diagrams help to visualize the code structure and the communication between objects, enabling a high degree of abstraction. The cryogenics Vulcain and HM7B engines power cycles along with the staged-combustion SSME engine perform the verification of the codes. Finally, the influence of changes in design parameters on the performance and dry mass of the L75 rocket engine is analyzed.
DOI: 10.6084/m9.figshare.6832565
title: A Reliable Method for Predicting the Specific Impulse of Chemical Propellants

description: ABSTRACT The specific impulse (Isp) is an important performance parameter that describes energy efficiency of propellant combustion and is intimately related to the rocket engine thrust. In this study, it was possible by using only two variables, i.e., the heat of reaction (Q) and the number of moles of gaseous reaction products per gram of propellant (Ng) calculated according to [H2O-CO2] arbitrary decomposition assumption and constants derived from the ISPBKW code to predict the specific impulse of more than 165 compositions belonging to virtually all classes of propellants such as monopropellants, single-base, double-base, triple-base, and cast modified double-base (CMDB) propellants, pseudo-propellants, composite propellants, liquid mono- and bipropellants, and finally hybrid propellants. Further analysis reveals that for C-H-N-O containing propellants, the specific impulse values estimated using the new method should not deviate more than 5% from the output of the ISPBKW thermochemical code.