The stability of an atomic clock can change with time due to several factors, such as temperature, humidity, radiations, aging, and sudden breakdowns. The dynamic Allan variance, or DAVAR, is a representation of the t...
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The stability of an atomic clock can change with time due to several factors, such as temperature, humidity, radiations, aging, and sudden breakdowns. The dynamic Allan variance, or DAVAR, is a representation of the time-varying stability of an atomic clock, and it can be used to monitor the clock behavior. Unfortunately, the computational time of the DAVAR grows very quickly with the length of the analyzed time series. In this article, we present a fast algorithm for the computation of the DAVAR, and we also extend it to the case of missing data. Numerical simulations show that the fast algorithm dramatically reduces the computational time. The fast algorithm is useful when the analyzed time series is long, or when many clocks must be monitored, or when the computational power is low, as happens onboard satellites and space probes.
Additive manufacturing (AM) is evolving toward multimaterial processes for improved functionality and performance. A recently developed AMF format provides the platforms for digitizing multimaterial/feature model suit...
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Additive manufacturing (AM) is evolving toward multimaterial processes for improved functionality and performance. A recently developed AMF format provides the platforms for digitizing multimaterial/feature model suitable for AM processes. However, the current build strategies of monomaterial may not be appropriate for multimaterial objects presented in AMF format. The internal architecture of the part cannot be ignored in heterogeneous solids and functional porous objects. The material deposition path-plan in such multifeature objects can be interrupted by frequent directional changes and/or secondary material source activation. Dealing with these interruptions during fabrication requires more resources and may affect the part integrity, quality, and build time. This research aims to minimize such interruptions by focusing on build direction. A computational algorithm is proposed for the heterogeneous object that quantifies the build direction considering the feature characteristics and manufacturing attributes in order to bundle the slices based on the heterogeneity. The proposed methodology is illustrated by two heterogeneous models and generates more than 42% homogeneous slices generated for both examples. Higher heterogeneity is consolidated in strips that may require more resources during fabrication. Thus, differentiating and bundling the slice based on the resources requirement would certainly benefit the process plan for the multimaterial additive manufacturing technique.
The paper presents a closed-form solution, in the distributional form, of the bending problem for continuous sandwich panels in lightweight cladding that has been derived from the general solution of the system of dif...
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The paper presents a closed-form solution, in the distributional form, of the bending problem for continuous sandwich panels in lightweight cladding that has been derived from the general solution of the system of differential equations for the problem of sandwich beams with thick facings. The analysis covers three-layer members with facings made from profiled metal sheets and a core having good insulating properties, for any number and spacing of elastic intermediate supports. Panels are subjected to bending under uniform transverse load and a load caused by temperature difference. The solution for the multi-span panels inflexibly (rigidly) pin-supported at their ends is derived from the general solution for members arbitrarily supported at their ends. A calculation algorithm for this type of panels is provided. Numerical examples are included to illustrate the influence of the intermediate supports on the effort of both the entire sandwich panel and its profiled facing. Finally, practical concluding remarks are given. (C) 2014 Elsevier Ltd. All rights reserved.
The new quantum simulation model and the self-consistent algorithm (SCA) for magnetic nanosystems, that we proposed 2 years ago, were extended to study the magnetic properties of a nanowire consisting of 3d ions which...
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The new quantum simulation model and the self-consistent algorithm (SCA) for magnetic nanosystems, that we proposed 2 years ago, were extended to study the magnetic properties of a nanowire consisting of 3d ions which are coupled ferromagnetically. To test the applicability of the algorithm, our simulations in the present work were started from a magnetic structure in which all spins in the whole nanosample were randomly oriented (defined as the random magnetic configuration for later use) as other authors have been doing with Monte Carlo or micromagnetism method, and such calculated results were all reasonable. Especially, the free energies evaluated at the chosen temperatures were found to attenuate spontaneously and quickly, as the program ran, towards the minima according to the principle of lowest free energy as expected. This suggests that the computational algorithm is able to lead the code to converge rapidly to the equilibrium state automatically without the need to minimize the total (free) energy of the system elaborately that must be done if the Monte Carlo or micromagnetism method is used, demonstrating the great power of natural laws. (C) 2013 Elsevier B.V. All rights reserved.
Artificial neural network (ANN) is a computational algorithm based on the structure and functions of biological neural networks. It is used for modelling of the non-linear systems that cannot be mathematically express...
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Artificial neural network (ANN) is a computational algorithm based on the structure and functions of biological neural networks. It is used for modelling of the non-linear systems that cannot be mathematically expressed by the formula and extraction of the system dynamics, expressed by using the complex mathematical equations, such as harmonics. To show the effective usage of ANNs in the power system, the fundamental harmonic of a load with six-pulse thyristor controlled rectifier is extracted with ANN by using the system variables that are difficult to express with each other. Then, a new approach is proposed to generate the reference signal for compensating the harmonics of the current by using discrete fuzzy logic in this study. In addition, a simple and useful method to determine the circuit parameters of the active power filter (APF) is proposed to reduce the rating of the required filter and the capacitor values without affecting its efficiency. Case studies are performed to test the performance of the proposed control algorithm for APF.
Two new quantum simulation methods, which we developed recently based on the Metropolis and self-consistent algorithms defined as QMC and SCA approaches respectively, were employed to investigate the magnetic properti...
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Two new quantum simulation methods, which we developed recently based on the Metropolis and self-consistent algorithms defined as QMC and SCA approaches respectively, were employed to investigate the magnetic properties of an antiferromagnetic nanoparticle with strong surface anisotropy. All simulations were started from a random magnetic configuration and carried out from a temperature well above the phase transition stepwise down to very low temperatures as other researchers have been doing in classical Monte Carlo (CMC) simulations. It turns out that the magnetic structures, magnetizations, total (free) energy, magnetic entropy and specific heat calculated by means of the two approaches are well consistent with each other, thereby verifying their correctness mutually. (C) 2014 Elsevier B.V. All rights reserved.
The problem of optimal observation of a nonlinear step system is considered. The task is to obtain guaranteed estimates of the initial state from given incomplete and inaccurate measurements of the current states. The...
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The problem of optimal observation of a nonlinear step system is considered. The task is to obtain guaranteed estimates of the initial state from given incomplete and inaccurate measurements of the current states. The cases of fixed and unfixed transition times in a step system are examined. algorithms for solving a posteriori and positional observation problems are proposed. The results are illustrated by examples.
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