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Journal articles on the topic 'Non-random modes'
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1
Carlquist, Sherwin. "Non-random Vessel Distribution in Woods: Patterns, Modes, Diversity, Correlations." Aliso 27, no. 1 (2009): 39–58. http://dx.doi.org/10.5642/aliso.20092701.04.
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Angelani, Luca, Matteo Paoluzzi, Giorgio Parisi, and Giancarlo Ruocco. "Probing the non-Debye low-frequency excitations in glasses through random pinning." Proceedings of the National Academy of Sciences 115, no. 35 (August 13, 2018): 8700–8704. http://dx.doi.org/10.1073/pnas.1805024115.
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We investigate the properties of the low-frequency spectrum in the density of states D(ω) of a 3D model glass former. To magnify the non-Debye sector of the spectrum, we introduce a random pinning field that freezes a finite particle fraction to break the translational invariance and shifts all of the vibrational frequencies of the extended modes toward higher frequencies. We show that non-Debye soft localized modes progressively emerge as the fraction p of pinned particles increases. Moreover, the low-frequency tail of D(ω) goes to zero as a power law ωδ(p), with 2≤δ(p)≤4 and δ=4 above a threshold fraction pth.
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VENTURI, DANIELE, XIAOLIANG WAN, and GEORGE EM KARNIADAKIS. "Stochastic low-dimensional modelling of a random laminar wake past a circular cylinder." Journal of Fluid Mechanics 606 (July 10, 2008): 339–67. http://dx.doi.org/10.1017/s0022112008001821.
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We present a new compact expansion of a random flow field into stochastic spatial modes, hence extending the proper orthogonal decomposition (POD) to noisy (non-coherent) flows. As a prototype problem, we consider unsteady laminar flow past a circular cylinder subject to random inflow characterized as a stationary Gaussian process. We first obtain random snapshots from full stochastic simulations (based on polynomial chaos representations), and subsequently extract a small number of deterministic modes and corresponding stochastic modes by solving a temporal eigenvalue problem. Finally, we determine optimal sets of random projections for the stochastic Navier–Stokes equations, and construct reduced-order stochastic Galerkin models. We show that the number of stochastic modes required in the reconstruction does not directly depend on the dimensionality of the flow system. The framework we propose is general and it may also be useful in analysing turbulent flows, e.g. in quantifying the statistics of energy exchange between coherent modes.
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RAGHU KANTH, S. T. G. "INTRINSIC MODE FUNCTIONS OF EARTHQUAKE SLIP DISTRIBUTION." Advances in Adaptive Data Analysis 02, no. 02 (April 2010): 193–215. http://dx.doi.org/10.1142/s1793536910000458.
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In this paper, empirical mode decomposition technique is used to analyze the spatial slip distribution of five past earthquakes. It is shown that the finite fault slip models exhibit five empirical modes of oscillation. The last intrinsic mode is positive and characterizes the non-stationary mean of the slip distribution. This helps in splitting the spatial variability of slip into trend and the remaining modes sum as the fluctuation in the data. The fluctuation component indicates that it can be modeled as an anisotropic random field. Important parameters of this random field have been estimated. The effect of these modes on ground motion is presented by simulating both acceleration and displacement time histories.
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Javorskyj, І. M., R. M. Yuzefovych, O. V. Lychak, G. R. Trokhym, and M. Z. Varyvoda. "Stochastic model of the gearbox pair vibration." Information extraction and processing 2021, no. 49 (December 17, 2021): 26–31. http://dx.doi.org/10.15407/vidbir2021.49.026.
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The model of vibration signal of gearbox pair in the form of periodically correlated non-stationary random process is considered. It is shown that hidden periodicities in biperiodic correlated random process mean and covariance function, characterizing the vibrations of gearbox pair can be detected using the component and least square methods. Seven particular cases of the bi-rhythmic hidden periodicity for different modulation modes are analyzed.
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SAKAI, Yasuhiko, Takeshi SUZUKI, and Ikuo NAKAMURA. "Numerical Simulation of Scalar Fluctuation Field in a Non-Buoyant Plume by Random Fourier Modes." Transactions of the Japan Society of Mechanical Engineers Series B 64, no. 628 (1998): 3970–77. http://dx.doi.org/10.1299/kikaib.64.3970.
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Kuznetsov, B. I., T. B. Nikitina, I. V. Bovdui, O. V. Voloshko, V. V. Kolomiets, and B. B. Kobylianskyi. "The method of multi objective synthesis of stochastic robust control by multimass electromechanical systems under non-gausian random external disturbances." Electrical Engineering & Electromechanics, no. 5 (September 6, 2022): 21–30. http://dx.doi.org/10.20998/2074-272x.2022.5.04.
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Aim. Development of the method of multi objective synthesis of stochastic robust control by multimass electromechanical systems to satisfy various requirements for the operation of such systems in various modes under non-gausian random external disturbances. Methodology. The problem of multi objective synthesis of stochastic robust control by multimass electromechanical systems to satisfy various requirements for the operation of such systems in various modes under non-gausian random external disturbances solved based on the choosing of weight matrices in the robust control goal vector.The calculation of the target vector is performed based on the solution of the zero-sum vector antagonistic game. The components of the game payoff vector are variable quality indicators that are applied to the system operation in various modes. The calculation of the components of payoff vector game are performed based on the simulation of the initial system closed by the synthesized stochastic controllers in various operating modes and under various external influences and variations in the parameters of the uncertainty of the initial plant. Results. The results of multi objective synthesis of stochastic robust two-mass electromechanical servo systems modes under non-gausian random external disturbances in which differences requirements for the operation of such systems in various modes were satisfied are given. Based on the results of modeling and experimental studies it is established, that with the help of synthesized robust nonlinear controllers, it is possible to improve of quality indicators of two-mass electromechanical servo system in comparison with the system with standard regulators. Originality. For the first time the method of multi objective synthesis of stochastic robust control by multimass electromechanical systems to satisfy various requirements for the operation of multimass systems in various modes is developed. Practical value. From the point of view of the practical implementation the possibility of solving the problem of multi objective synthesis of stochastic robust control systems to satisfy various requirements for the operation of multimass electromechanical systems in various modes is shown.
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Yew, Pauline, Lee Sai Cheong, Ng Sha Shiong, Yoon Tiem Leong, Haslan Abu Hassan, and Wei Li Chen. "Polarized Infrared Reststrahlen Features of Wurtzite InGaN Thin Film." Materials Science Forum 846 (March 2016): 614–19. http://dx.doi.org/10.4028/www.scientific.net/msf.846.614.
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Polarized infrared (IR) reflectance measurement was carried out to investigate the optical phonon modes of wurtzite structure In0.92Ga0.08N thin film grown by molecular beam epitaxy. Composition dependence of IR reststrahlen features was observed. Theoretical polarized IR reflectance spectrum was simulated using the standard multilayer optics technique with a multi-oscillator dielectric function model. By obtaining the best fit of experimental and theoretical spectrum, the Brillouin zone center E1 optical phonon modes together with the dielectric constant, layer thickness, free carriers concentration and mobility were extracted non-destructively. The extracted E1 optical phonon modes were compared with those generated from modified random element isodisplacement (MREI) model.
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Mamaeva M. P., Selivanov N. I., Emeline A. V., and Kapitonov Yu. V. "Random lasing in MAPbI-=SUB=-3-=/SUB=- single crystal." Optics and Spectroscopy 130, no. 5 (2022): 565. http://dx.doi.org/10.21883/eos.2022.05.54440.8-22.
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Halide perovskites are a promising medium for the creation of microlasers. Random lasing in single crystals can provide principal information on the nature of laser radiation in these materials. This paper demonstrates random lasing in a MAPbI3 (MA+=CH3NH_3+) single crystal at a temperature T = 30 K and pulsed optical excitation with a repetition rate of 80 MHz. The observed laser radiation has a multimode composition with a quality factor of individual modes Q ~ 1200 and threshold behavior. The paper also proposes a method for separating the background non-polarized photoluminescence and lasing signals. Keywords: halide perovskites: random lasing: MAPbI3.
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Cheng, Wen, Gurdiljot Singh Gill, Tom Vo, Jiao Zhou, and Taha Sakrani. "Use of Bivariate Dirichlet Process Mixture Spatial Model to Estimate Active Transportation-Related Crash Counts." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 38 (July 1, 2018): 105–15. http://dx.doi.org/10.1177/0361198118782797.
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The current paper presents the comprehensive analysis of a bivariate Dirichlet process mixture spatial model for estimation of pedestrian and bicycle crash counts. This study focuses on active transportation at traffic analysis zone (TAZ) level by developing a semi-parametric model that accounts for the unobserved heterogeneity by combining the strengths of bivariate specification for correlation among crash modes; spatial random effects for the impact of neighboring TAZs; and Dirichlet process mixture for random intercept. Three alternate models, one Dirichlet and two parametric, are also developed for comparison based on different criteria. Bicycle and pedestrian crashes are observed to share three influential variables: the positive correlation of K12 student enrollment; the bike-lane density; and the percentage of arterial roads. The heterogeneity error term demonstrates the presence of statistically significant correlation among the bicycle and pedestrian crashes, whereas the spatial random effect term indicates the absence of a significant correlation for the area under focus. The Dirichlet models are consistently superior to non-Dirichlet ones under all evaluation criteria. Moreover, the Dirichlet models exhibit the capability to identify latent distinct subpopulations and suggest that the normal assumption of intercept associated with traditional parametric models does not hold true for the TAZ-level crash dataset of the current study.
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Emanuel, Gunadi, R. Kristoforus J. Bendi, and Arieffianto Arieffianto. "DESAIN NON-PLAYER CHARACTER PERMAINAN TIC-TAC-TOE DENGAN ALGORITMA MINIMAX." Jurnal Ilmiah Matrik 21, no. 3 (December 19, 2019): 223–33. http://dx.doi.org/10.33557/jurnalmatrik.v21i3.725.
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Abstract : Tic-Tac-Toe is one of the board games. It is played by filling the columns on the board with X or O in such a way as to form parallel lines vertically, horizontally and diagonally. This study aims to design Non-Player Characters (NPC) in the tic-tac-toe game with the minimax algorithm. The Tic-tac-toe game will be designed with two game modes: easy and minimum random modes. While in minimax NPC mode will determine the best step. The game development process of the tic-tac-toe application is based on a linear sequence process model. In the analysis phase, the NPC will be designed based on the concept of minimax. Software modeling was designed using Unified Modeling Language (UML), and coded with Visual Basic programming. Our tests show that NPCs with the Minimax algorithm can work well.
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Du, Min, Liu Jin, Xiu Li Du, and Yan Zhao. "The Concrete Fracture Performance Response to the Interface Transition Zone Parameters Based on Mesoscopic Simulation." Applied Mechanics and Materials 170-173 (May 2012): 3482–86. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.3482.
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The interface transition zone (ITZ) has a significant impact on the concrete’s mechanical properties and fracture modes. For the influence of ITZ’s strength and elastic modulus, the extended finite element method (XFEM) is adopted to simulate the mesostructure failure process by virtue of random aggregate model under uniaxial tension. The results show that ITZ’s strength and elastic modulus have a certain effect on the mechanical properties and fracture modes. With the tensile strength of ITZ increasing, the fractured modes transit from single coalescent crack to multiple non-coalescent cracks and the fracture energy increases, the ductility of concrete is enhanced. With the elastic modulus of ITZ increasing, the concrete’s elastic modulus increases, the tensile strength and the fracture energy decrease.
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Ibrahim, R. A., and R. T. Heinrich. "Experimental Investigation of Liquid Sloshing Under Parametric Random Excitation." Journal of Applied Mechanics 55, no. 2 (June 1, 1988): 467–73. http://dx.doi.org/10.1115/1.3173701.
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This paper presents an experimental investigation of the random parametric excitation of a dynamic system with nonlinear inertia. The experimental model is a rigid circular tank partially filled with an incompressible inviscid liquid. The random responses of the first antisymmetric and symmetric sloshing modes are considered for band-limited random excitations. These include the means, mean squares, and probability density functions of each sloshing mode. The response of the liquid-free surface is found to be a stationary process for test durations exceeding ten minutes. The time-history response records reveal four response characteristic regimes. Each regime takes place within a certain range of excitation spectral density level. An evidence of the jump phenomenon, which was predicted theoretically by using the non-Gaussian closure scheme, is also reported. Comparisons with analytical results, derived by three different approaches, are given for the first antisymmetric sloshing mode.
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Obermeyer, Andy, Christos Evangelinos, and Andreas Besherz. "Der Wert der Reisezeit deutscher Pendler." Perspektiven der Wirtschaftspolitik 14, no. 1-2 (March 1, 2013): 118–31. http://dx.doi.org/10.1111/pers.12007.
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AbstractTravel time savings are usually the most important utility component of transport projects. This paper shows estimation of the value of travel time savings (VTTS) with particular focus on random parameter models. Employing these models commuters’ VTTS in the German City Dresden is estimated. Results show that travel time savings of motorised and non-motorised modes are valued differently, VTTS derived in this study are higher than values currently used in Germany’s federal transport infrastructure plan and VTTS are dependent on travel time.
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Yasuda, T., N. Nakashima, and Y. Tsuchiya. "GROUPING WAVES AND THEIR EXPRESSING ON ASYMPTOTIC ENVELOPE SOLITON MODES." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 65. http://dx.doi.org/10.9753/icce.v20.65.
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An approach, that treats natural sea states with remarkable groupiness as random sequences of envelope solitons, is suggested here to explain their dynamical and statistical properties from the viewpoint that wave packets contained in the states have their own characteristics and should be regarded as elementary modes. Some examinations are made on its applicability to the temporally observed waves. And the approach is shown to be effective also for waves with a non-zero nonlinearity and finite spectral band-width. Further, a formulation based on envelope solitons is made on the wave drifting force and is shown to be useful for analyzing the time series of drifting forces.
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Hao, Hui Bing, and Chun Su. "Reliability Analysis on Competitive Failure Processes under Multiple Failure Modes." Applied Mechanics and Materials 442 (October 2013): 257–63. http://dx.doi.org/10.4028/www.scientific.net/amm.442.257.
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In this article, a new multiple competing failure models proposed, in which multiple degradation processes and random shocks are considered. The shocks have a significant impact on system reliability, and the system reliability under not considering the impact of shocks is much higher than the impact of shocks is considered. In addition, the influences of the correlation among different degradation processes are also considered in this article. We can find that the reliability with considering the dependent case is higher than the independent case reliability. Thus the dependence of the two degradation processes is non-negligible. A numerical example with reliability analysis and sensitivity analysis is discussed to illustrate the proposed the new model.
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Ashwini, B. P., R. Sumathi, and H. S. Sudhira. "Bus Travel Time Prediction: A Comparative Study of Linear and Non-Linear Machine Learning Models." Journal of Physics: Conference Series 2161, no. 1 (January 1, 2022): 012053. http://dx.doi.org/10.1088/1742-6596/2161/1/012053.
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Abstract Congested roads are a global problem, and increased usage of private vehicles is one of the main reasons for congestion. Public transit modes of travel are a sustainable and eco-friendly alternative for private vehicle usage, but attracting commuters towards public transit mode is a mammoth task. Commuters expect the public transit service to be reliable, and to provide a reliable service it is necessary to fine-tune the transit operations and provide well-timed necessary information to commuters. In this context, the public transit travel time is predicted in Tumakuru, a tier-2 city of Karnataka, India. As this is one of the initial studies in the city, the performance comparison of eight Machines Learning models including four linear namely, Linear Regression, Ridge Regression, Least Absolute Shrinkage and Selection Operator Regression, and Support Vector Regression; and four non-linear models namely, k-Nearest Neighbors, Regression Trees, Random Forest Regression, and Gradient Boosting Regression Trees is conducted to identify a suitable model for travel time predictions. The data logs of one month (November 2020) of the Tumakuru city service, provided by Tumakuru Smart City Limited are used for the study. The time-of-the-day (trip start time), day-of-the-week, and direction of travel are used for the prediction. Travel time for both upstream and downstream are predicted, and the results are evaluated based on the performance metrics. The results suggest that the performance of non-linear models is superior to linear models for predicting travel times, and Random Forest Regression was found to be a better model as compared to other models.
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Мамаева, М. П., Н. И. Селиванов, А. В. Емелин, and Ю. В. Капитонов. "Случайная лазерная генерация в монокристаллах MAPbI-=SUB=-3-=/SUB=-." Оптика и спектроскопия 130, no. 5 (2022): 717. http://dx.doi.org/10.21883/os.2022.05.52425.8-22.
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Halide perovskites are a promising medium for the creation of microlasers. Random lasing in single crystals can provide principal information on the nature of laser radiation in these materials. This paper demonstrates random lasing in a MAPbI3 (MA+ = CH_3NH_3+) single crystal at a temperature T = 30 K and pulsed optical excitation with a repetition rate of 80 MHz.The observed laser radiation has a multimode composition with a quality factor of individual modes Q ~ 1200 and threshold behavior. The paper also proposes a method for separating the background non-polarized photoluminescence and lasing signals.
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Chakravorti, Tatiana, Lipsa Priyadarshini, P. K. Dash, and Badri Narayan Sahu. "Islanding and non-islanding disturbance detection in microgrid using optimized modes decomposition based robust random vector functional link network." Engineering Applications of Artificial Intelligence 85 (October 2019): 122–36. http://dx.doi.org/10.1016/j.engappai.2019.06.004.
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Qi, Di, and Jian-Guo Liu. "A random batch method for efficient ensemble forecasts of multiscale turbulent systems." Chaos: An Interdisciplinary Journal of Nonlinear Science 33, no. 2 (February 2023): 023113. http://dx.doi.org/10.1063/5.0129127.
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A new efficient ensemble prediction strategy is developed for a multiscale turbulent model framework with emphasis on the nonlinear interactions between large and small-scale variables. The high computational cost in running large ensemble simulations of high-dimensional equations is effectively avoided by adopting a random batch decomposition of the wide spectrum of the fluctuation states, which is a characteristic feature of the multiscale turbulent systems. The time update of each ensemble sample is then only subject to a small portion of the small-scale fluctuation modes in one batch, while the true model dynamics with multiscale coupling is respected by frequent random resampling of the batches at each time updating step. We investigate both theoretical and numerical properties of the proposed method. First, the convergence of statistical errors in the random batch model approximation is shown rigorously independent of the sample size and full dimension of the system. Next, the forecast skill of the computational algorithm is tested on two representative models of turbulent flows exhibiting many key statistical phenomena with a direct link to realistic turbulent systems. The random batch method displays robust performance in capturing a series of crucial statistical features with general interests, including highly non-Gaussian fat-tailed probability distributions and intermittent bursts of instability, while requires a much lower computational cost than the direct ensemble approach. The efficient random batch method also facilitates the development of new strategies in uncertainty quantification and data assimilation for a wide variety of general complex turbulent systems in science and engineering.
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Kovernikova, L. I., and Van Chung Luong. "New approach to modeling the nonlinear loads." E3S Web of Conferences 139 (2019): 01055. http://dx.doi.org/10.1051/e3sconf/201913901055.
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Parameters of operating conditions of electric power systems shall ensure efficient and reliable operation of both power generating companies and of consumers, which to a great extent depends on power quality. Most urgent problem in this area is currently non-sinusoidal voltage. Power quality control, development of technical measures to sustain parameters of harmonic modes in conformity with provisions of GOST 32144-2013 require calculations that, in turn, need models adequately representing the electric networks and nonlinear loads in the computing program. Results of studies on parameters of harmonic modes that were obtained by measurements have shown that harmonic modes are random, and their parameters have probabilistic nature. Due to unpredictability of harmonic modes, nonlinear loads can be modeled using measured parameters. The paper presents methodological approach, algorithms and a computing program for modeling the nonlinear loads using parameters measured in the nodes of their connection to the power supply, and gives examples of modeling the nonlinear loads.
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Balagurunathan, Yoganand, Edward R. Dougherty, Stanislav Frančišković-Bilinski, Halka Bilinski, and Neda Vdović. "MORPHOLOGICAL GRANULOMETRIC ANALYSIS OF SEDIMENT IMAGES." Image Analysis & Stereology 20, no. 2 (May 3, 2011): 87. http://dx.doi.org/10.5566/ias.v20.p87-99.
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Sediments are routinely analyzed in terms of the sizing characteristics of the grains of which they are composed. Via sieving methods, the grains are separated and a weight-based size distribution constructed. Various moment parameters are computed from the size distribution and these serve as sediment characteristics. This paper examines the feasibility of a fully electronic granularity analysis using digital image processing. The study uses a random model of three-dimensional grains in conjunction with the morphological method of granulometric size distributions. The random model is constructed to simulate sand, silt, and clay particle distributions. Owing to the impossibility of perfectly sifting small grains so that they do not touch, the model is used in both disjoint and non-disjoint modes, and watershed segmentation is applied in the non-disjoint model. The image-based granulometric size distributions are transformed so that they take into account the necessity to view sediment fractions at different magnifications and in different frames. Gray-scale granulometric moments are then computed using both ordinary and reconstructive granulometries. The resulting moments are then compared to moments found from real grains in seven different sediments using standard weight-based size distributions.
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Luo, Xisheng, Yu Liang, Ting Si, and Zhigang Zhai. "Effects of non-periodic portions of interface on Richtmyer–Meshkov instability." Journal of Fluid Mechanics 861 (December 20, 2018): 309–27. http://dx.doi.org/10.1017/jfm.2018.923.
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The development of a non-periodic $\text{air}\text{/}\text{SF}_{6}$ gaseous interface subjected to a planar shock wave is investigated experimentally and theoretically to evaluate the effects of the non-periodic portions of the interface on the Richtmyer–Meshkov instability. Experimentally, five kinds of discontinuous chevron-shaped interfaces with or without non-periodic portions are created by the extended soap film technique. The post-shock flows and the interface morphologies are captured by schlieren photography combined with a high-speed video camera. A periodic chevron-shaped interface, which is multi-modal (81 % fundamental mode and 19 % high-order modes), is first considered to evaluate the impulsive linear model and several typical nonlinear models. Then, the non-periodic chevron-shaped interfaces are investigated and the results show that the existence of non-periodic portions significantly changes the balanced position of the initial interface, and subsequently disables the nonlinear model which is applicable to the periodic chevron-shaped interface. A modified nonlinear model is proposed to consider the effects of the non-periodic portions. It turns out that the new model can predict the growth of the shocked non-periodic interface well. Finally, a method is established using spectrum analysis on the initial shape of the interface to separate its bubble structure and spike structure such that the new model can apply to any random perturbed interface. These findings can facilitate the understanding of the evolution of non-periodic interfaces which are more common in reality.
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REMMEL, MARK, and LESLIE SMITH. "New intermediate models for rotating shallow water and an investigation of the preference for anticyclones." Journal of Fluid Mechanics 635 (September 10, 2009): 321–59. http://dx.doi.org/10.1017/s0022112009007897.
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New intermediate models for the rotating shallow water (RSW) equations are derived by considering the nonlinear interactions between subsets of the eigenmodes for the linearized equations. It is well-known that the two-dimensional quasi-geostrophic (QG) equation results when the nonlinear interactions are restricted to include only the vortical eigenmodes. Continuing past QG in a non-perturbative manner, the new models result by including subsets of interactions which include inertial-gravity wave (IG) modes. The such simplest model adds nonlinear interactions between one IG mode and two vortical modes. In sharp contrast to QG, the latter model behaves similar to the full RSW equations for decay from balanced initial conditions as well as unbalanced random initial conditions with divergence-free velocity. Quantitative agreement is observed for statistics that measure structure size, intermittency and cyclone/anticyclone asymmetry. In particular, dominance of anticyclones is observed for Rossby numbers Ro in the range 0.1 < Ro < 1 (away from the QG parameter regime Ro → 0). A hierarchy of models is explored to determine the effects of wave-vortical and wave–wave interactions on statistics such as the skewness of vorticity in decaying turbulence. Possible advantages over previously derived intermediate models include (i) the non-perturbative nature of the new models (not restricting them a priori to any particular parameter regime) and (ii) insight into the physical and mathematical consequences of vortical–wave interactions.
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Mondal, Subhajit, and Sushanta Chakraborty. "Identification of non-proportional viscous damping matrix of beams by finite element model updating." Journal of Vibration and Control 24, no. 11 (November 17, 2016): 2134–48. http://dx.doi.org/10.1177/1077546316678528.
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A methodology has been proposed to estimate non-proportional viscous damping matrix of beams from measured complex eigendata using finite element model updating technique. Representation of damping through a proportional damping matrix ignoring the complexity of eigenvectors may not be appropriate when external damping devices are employed. The current literature of determination of non-proportional damping matrix demands measurement of a large number of complex modes which is extremely difficult in practice. A gradient based finite element model updating algorithm implementing inverse eigensensitivity method has been presented through a series of numerically simulated cantilever beams. The method can accurately predict the non-proportional damping matrix even if the measured eigenvectors are polluted with random noise. The novelty of the current method is that it can sustain a high level of modal and coordinate sparsity in measurement. The method assumes prior determination or updating of the mass and stiffness matrices.
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Anggoro, Bambang Sri. "Sejarah Teori Peluang dan Statistika." Al-Jabar : Jurnal Pendidikan Matematika 6, no. 1 (June 16, 2015): 13–24. http://dx.doi.org/10.24042/ajpm.v6i1.55.
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Opportunity theory is a branch of mathematics concerned with opportunities, analysis of random phenomena. The main objects of opportunity theory are random variables, stochastic processes, and events: a non-deterministic mathematical abstraction of measurable events or quantities that can be either single events or develop over time in seemingly random modes. If individual coins throw or dice rolls are considered random events, then if repeated sequences of random events will show certain patterns, which can be learned and predicted. Two representative mathematical results illustrating such patterns are the laws of large numbers and the central limit theorem. As a mathematical basis for statistics, probability theory is important for many human activities that involve quantitative analysis of large sets of data. The method of opportunity theory also applies to complex system descriptions given only partial knowledge of their country, as in statistical mechanics. A great discovery of twentieth-century physics is the nature of probability of physical phenomena on the atomic scale, described in quantum mechanics.
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Li, Yue, Linlin Li, and Chao Zhang. "Desert seismic signal denoising by 2D compact variational mode decomposition." Journal of Geophysics and Engineering 16, no. 6 (September 10, 2019): 1048–60. http://dx.doi.org/10.1093/jge/gxz065.
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Abstract Noise suppression and effective signal recovery are very important for seismic signal processing. The random noise in desert areas has complex characteristics due to the complex geographical environment; noise characteristics such as non-stationary, non-linear and low frequency. These make it difficult for conventional denoising methods to remove random noise in desert seismic records. To address the problem, this paper proposes a two-dimensional compact variational mode decomposition (2D-CVMD) algorithm for desert seismic noise attenuation. This model decomposes the complex desert seismic data into an finite number of intrinsic mode functions with specific directions and vibration characteristics. The algorithm introduces binary support functions, which can detect the edge region of the signal in each mode by penalizing the support function through the L1 and total variation (TV) norm. Finally, the signal can be reconstructed by the support functions and the decomposed modes. We apply the 2D-CVMD algorithm to synthetic and real seismic data. The results show that the 2D-CVMD algorithm can not only suppress desert low-frequency noise, but also recover the weak effective signal.
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Li, Wenlung, and R. A. Ibrahim. "Monte Carlo Simulation of Coupled Nonlinear Oscillators Under Random Excitations." Journal of Applied Mechanics 57, no. 4 (December 1, 1990): 1097–99. http://dx.doi.org/10.1115/1.2897638.
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The main objectives of this note are to examine the random response of nonlinear three degree-of-freedom systems in the neighborhood of combination internal resonance by using Monte Carlo simulation and to compare the results with those obtained by first-order non-Gaussian closure. The numerical simulation is found to support the main features of the nonlinear interaction in the neighborhood of internal resonance conditions. For example, the nonlinear interaction takes place in the form of a randomly continuous energy exchange between the modes involved. In addition, the results verify the existence of energy absorbing effect as predicted by the non-Gaussian closure method. While the non-Gaussian closure exhibits regions of multiple solutions in the neighborhood of exact internal resonance, the numerical simulation gives only one solution depending on the assigned initial conditions. This observation requires further investigation to establish the domains of attraction in stochastic nonlinear dynamics.
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Verma, Mahendra K. "Boltzmann equation and hydrodynamic equations: their equilibrium and non-equilibrium behaviour." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2175 (June 22, 2020): 20190470. http://dx.doi.org/10.1098/rsta.2019.0470.
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This short article summarizes the key features of equilibrium and non-equilibrium aspects of Boltzmann and hydrodynamic equations. Under equilibrium, the Boltzmann equation generates uncorrelated random velocity that corresponds to k 2 energy spectrum for the Euler equation. The latter spectrum is produced using initial configuration with many Fourier modes of equal amplitudes but with random phases. However, for a large-scale vortex as an initial condition, earlier simulations exhibit a combination of k −5/3 (in the inertial range) and k 2 (for large wavenumbers) spectra, with the range of k 2 spectrum increasing with time. These simulations demonstrate an approach to equilibrium or thermalization of Euler turbulence. In addition, they also show how initial velocity field plays an important role in determining the behaviour of the Euler equation. In non-equilibrium scenario, both Boltzmann and Navier–Stokes equations produce similar flow behaviour, for example, Kolmogorov’s k −5/3 spectrum in the inertial range. This article is part of the theme issue ‘Fluid dynamics, soft matter and complex systems: recent results and new methods’.
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Huete, C., J. G. Wouchuk, B. Canaud, and A. L. Velikovich. "Analytical linear theory for the shock and re-shock of isotropic density inhomogeneities." Journal of Fluid Mechanics 700 (April 30, 2012): 214–45. http://dx.doi.org/10.1017/jfm.2012.126.
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AbstractWe present an analytical model that describes the linear interaction of two successive shocks launched into a non-uniform density field. The re-shock problem is important in different fields, inertial confinement fusion among them, where several shocks are needed to compress the non-uniform target. At first, we present a linear theory model that studies the interaction of two successive shocks with a single-mode density perturbation field ahead of the first shock. The second shock is launched after the sonic waves emitted by the first shock wave have vanished. Therefore, in the case considered in this work, the second shock only interacts with the entropic and vortical perturbations left by the first shock front. The velocity, vorticity and density fields are later obtained in the space behind the second shock. With the results of the single-mode theory, the interaction with a full spectrum of random-isotropic density perturbations is considered by decomposing it into Fourier modes. The model describes in detail how the second shock wave modifies the turbulent field generated by the first shock wave. Averages of the downstream quantities (kinetic energy, vorticity, acoustic flux and density) are easily obtained either for two-dimensional or three-dimensional upstream isotropic spectra. The asymptotic limits of very strong shocks are discussed. The study shown here is an extension of previous works, where the interaction of a planar shock wave with random isotropic vorticity/entropy/acoustic spectra were studied independently. It is also a preliminary step towards the understanding of the re-shock of a fully turbulent flow, where all three of the modes, vortical, entropic and acoustic, might be present.
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Kumar Yadav, Sarvesh, and Rajib Saha. "Investigating non-Gaussianity in Cosmic Microwave Background temperature maps using spherical harmonic phases." Journal of Cosmology and Astroparticle Physics 2022, no. 01 (January 1, 2022): 001. http://dx.doi.org/10.1088/1475-7516/2022/01/001.
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Abstract In the era of precision cosmology, accurate estimation of cosmological parameters is based upon the implicit assumption of the Gaussian nature of Cosmic Microwave Background (CMB) radiation. Therefore, an important scientific question to ask is whether the observed CMB map is consistent with Gaussian prediction. In this work, we extend previous studies based on CMB spherical harmonic phases (SHP) to examine the validity of the hypothesis that the temperature field of the CMB is consistent with a Gaussian random field (GRF). The null hypothesis is that the corresponding CMB SHP are independent and identically distributed in terms of a uniform distribution in the interval [0, 2π] [1,2]. We devise a new model-independent method where we use ordered and non-parametric Rao's statistic, based on sample arc-lengths to comprehensively test uniformity and independence of SHP for a given ℓ mode and independence of nearby ℓ mode SHP. We performed our analysis on the scales limited by spherical harmonic modes ≤ 128, to restrict ourselves to signal-dominated regions. To find the non-uniform or dependent sets of SHP, we calculate the statistic for the data and 10000 Monte Carlo simulated uniformly random sets of SHP and use 0.05 and 0.001 α levels to distinguish between statistically significant and highly significant detections. We first establish the performance of our method using simulated Gaussian, non-Gaussian CMB temperature maps, along with observed non-Gaussian 100 and 143 GHz Planck channel maps. We find that our method, performs efficiently and accurately in detecting phase correlations generated in all of the non-Gaussian simulations and observed foreground contaminated 100 and 143 GHz Planck channel temperature maps. We apply our method on Planck satellite mission's final released CMB temperature anisotropy maps- COMMANDER, SMICA, NILC, and SEVEM along with WMAP 9 year released ILC map. We report that SHP corresponding to some of the m-modes are non-uniform, some of the ℓ mode SHP and neighboring mode pair SHP are correlated in cleaned CMB maps. The detection of non-uniformity or correlation in the SHP indicates the presence of non-Gaussian signals in the foreground minimized CMB maps.
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Resseguier, Valentin, Etienne Mémin, Dominique Heitz, and Bertrand Chapron. "Stochastic modelling and diffusion modes for proper orthogonal decomposition models and small-scale flow analysis." Journal of Fluid Mechanics 826 (August 15, 2017): 888–917. http://dx.doi.org/10.1017/jfm.2017.467.
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We present here a new stochastic modelling approach in the constitution of fluid flow reduced-order models. This framework introduces a spatially inhomogeneous random field to represent the unresolved small-scale velocity component. Such a decomposition of the velocity in terms of a smooth large-scale velocity component and a rough, highly oscillating component gives rise, without any supplementary assumption, to a large-scale flow dynamics that includes a modified advection term together with an inhomogeneous diffusion term. Both of those terms, related respectively to turbophoresis and mixing effects, depend on the variance of the unresolved small-scale velocity component. They bring an explicit subgrid term to the reduced system which enables us to take into account the action of the truncated modes. Besides, a decomposition of the variance tensor in terms of diffusion modes provides a meaningful statistical representation of the stationary or non-stationary structuration of the small-scale velocity and of its action on the resolved modes. This supplies a useful tool for turbulent fluid flow data analysis. We apply this methodology to circular cylinder wake flow at Reynolds numbers $Re=100$ and $Re=3900$. The finite-dimensional models of the wake flows reveal the energy and the anisotropy distributions of the small-scale diffusion modes. These distributions identify critical regions where corrective advection effects, as well as structured energy dissipation effects, take place. In providing rigorously derived subgrid terms, the proposed approach yields accurate and robust temporal reconstruction of the low-dimensional models.
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Saigal, Taru, Arun Kr Vaish, and N. V. Muralidhar Rao. "Is the choice of less-polluting modes of transport for non-work purposes affected by socio-demographic factors? Evidence from India." Management of Environmental Quality: An International Journal 32, no. 3 (April 6, 2021): 488–505. http://dx.doi.org/10.1108/meq-09-2020-0212.
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PurposeUsing survey data of a developing country city, this study aims to examine the impact of different socio-demographic factors on the choice of less-polluting modes of transport for purposes other than work.Design/methodology/approachStratified random sampling technique is employed and data on socio-demographic characteristics and mode of transport used is collected. Descriptive statistics complemented with a logit model of choice probabilities is implemented on the data obtained.FindingsMajority of the population in the city uses motorized means of transportation irrespective of the socio-demographic changes existing among them. Women, the individuals belonging to the youngest age group, the least economically well-off group of people, the least educated and the non-working are the individuals more likely to use more of less-polluting modes and less of more-polluting modes for non-work purposes as compared to their counterparts.Research limitations/implicationsThe study also calls for the development of an efficient and secured system of public transportation and non-motorized transportation in the city in such a way so as to neither hamper the goal of sustainability nor the goal of empowerment.Originality/valueTo the best of the authors’ knowledge, this is the first time a comprehensive analysis of the influence of socio-demographic factors on choice of type of mode of transport is carried out in this region of the developing world. This analysis will facilitate the policy makers in catering to the transportation needs of different segments of the society.
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Asgari, Marika, Catherine Heymans, Hendrik Hildebrandt, Lance Miller, Peter Schneider, Alexandra Amon, Ami Choi, et al. "Consistent cosmic shear in the face of systematics: a B-mode analysis of KiDS-450, DES-SV and CFHTLenS." Astronomy & Astrophysics 624 (April 2019): A134. http://dx.doi.org/10.1051/0004-6361/201834379.
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We analyse three public cosmic shear surveys; the Kilo-Degree Survey (KiDS-450), the Dark Energy Survey (DES-SV) and the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Adopting the “COSEBIs” statistic to cleanly and completely separate the lensing E-modes from the non-lensing B-modes, we detect B-modes in KiDS-450 and CFHTLenS at the level of ∼2.7σ. For DES-SV we detect B-modes at the level of 2.8σ in a non-tomographic analysis, increasing to a 5.5σB-mode detection in a tomographic analysis. In order to understand the origin of these detected B-modes we measure the B-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modelling errors, camera-based additive shear bias and photometric redshift selection bias. We show that any correlation between photometric-noise and the relative orientation of the galaxy to the point-spread-function leads to an ellipticity selection bias in tomographic analyses. This work therefore introduces a new systematic for future lensing surveys to consider. We find that the B-modes in DES-SV appear similar to a superposition of the B-mode signatures from all of the systematics simulated. The KiDS-450 and CFHTLenS B-mode measurements show features that are consistent with a repeating additive shear bias.
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Lee, Jiahn-Shing, Shih-Tsung Chang, Li-Chuan Shieh, Ai-Yin Lim, Wei-Sheng Peng, Wei-Min Chen, Yen-Hsiu Liu, and Lai-Chu See. "Stereopsis and Response Times between Collegiate Table Tennis Athletes and Non-Athletes." International Journal of Environmental Research and Public Health 18, no. 12 (June 10, 2021): 6287. http://dx.doi.org/10.3390/ijerph18126287.
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Table tennis athletes and non-athletes potentially differ in stereopsis and eye–hand response times (RT), but whether stereopsis correlates with response time has scarcely been discussed. We aimed to compare stereopsis and RT between collegiate table tennis athletes and non-athletes and to examine the correlation between stereopsis and RT. From December 2016 to October 2019, table tennis athletes (n = 80) and non-athletes (n = 56) were recruited. Stereopsis was measured in four modes (A25, A50, R25, R50: approaching and receding directions at 25 mm/s or 50 mm/s). RT was measured with simple and choice tasks at zero, shoulder, and random distance. For stereopsis, the judged deviations were smaller during the approaching phases. Men had smaller A25 than women (p =0.012), whereas table tennis athletes showed smaller R25 and A50 than non-athletes (p = 0.03, 0.01, respectively). RT increased from simple to choice conditions and from zero to random, followed by shoulder distance. Men were significantly faster than women in choice tasks (p < 0.01). Table tennis athletes performed better in RT than the non-athletes (p < 0.05). No correlation was observed between stereopsis and RT (r = −0.01 to 0.12). In conclusion, athletes from table tennis sports showed better stereopsis and RT than non-athletes. Men had better stereopsis and RT than women. There was no correlation between stereopsis and RT.
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Rezende, Filipe, Otávio Brunet, Wendell Diniz Varela, André Pereira, and Eliane Carvalho. "Evaluation of TMD Performance in Footbridges Using Human Walking Probabilistic Models." Vibration 4, no. 2 (April 6, 2021): 323–40. http://dx.doi.org/10.3390/vibration4020021.
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Footbridges are generally slender and lightweight structures with low stiffness, designed to support dynamic loads generated by crowds. Therefore, these structures are exposed to vibration problems related to the resonance of human walking step frequencies and the lower vibration modes. To mitigate these problems, one of the most applied corrective strategies is the installation of tuned mass damper (TMD) systems that aim at the vibration reduction of the footbridge’s dominant mode. A fundamental matter in both the footbridge and the TMD design is the pedestrian load modelling, generally considered as a deterministically moving force or a biodynamic model. However, as human gait is a random process, the deterministic models can lead to non-realistic results, directly affecting the TMD system efficiency. In contrast, the use of probabilistic distributions to simulate the human walk randomness can lead to more reliable time series predictions. In this paper, a random walk (RW) algorithm is developed and applied to simulate different crowd scenarios using a simplified plane model of a coupled human-structure-TMD system. In each scenario, the TMD efficiency in reducing the vibration amplitudes is assessed. Results highlight the importance of considering the walking randomness and pedestrians’ dynamic properties in the TMD design.
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Lubatsch, Andreas, and Regine Frank. "Quantum Many-Body Theory for Exciton-Polaritons in Semiconductor Mie Resonators in the Non-Equilibrium." Applied Sciences 10, no. 5 (March 6, 2020): 1836. http://dx.doi.org/10.3390/app10051836.
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We implement externally excited ZnO Mie resonators in a framework of a generalized Hubbard Hamiltonian to investigate the lifetimes of excitons and exciton-polaritons out of thermodynamical equilibrium. Our results are derived by a Floquet-Keldysh-Green’s formalism with Dynamical Mean Field Theory (DMFT) and a second order iterative perturbation theory solver (IPT). We find that the Fano resonance which originates from coupling of the continuum of electronic density of states to the semiconductor Mie resonator yields polaritons with lifetimes between 0.6 ps and 1.45 ps. These results are compared to ZnO polariton lasers and to ZnO random lasers. We interpret the peaks of the exciton-polariton lifetimes in our results as a sign of gain narrowing which may lead to stable polariton lasing modes in the single excited ZnO Mie resonator. This form of gain may lead to polariton random lasing in an ensemble of ZnO Mie resonators in the non-equilibrium.
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Zhao, Yan Gang, Yue Feng Geng, and Kazuhiro Yoshihara. "Failure Mode Analysis for Column over Designed Ductile Frames." Key Engineering Materials 340-341 (June 2007): 1393–98. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.1393.
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In ultimate asseismic design of ductile frame structures, plastic deformation and plastic hinge are generally permitted, and some preferred failure modes are often selected. It is an important problem that whether the designed structure collapses according to the designed failure mode, because of the large uncertainties included in external loads and member strength. In this paper, an identification procedure of failure modes for frame structures is developed, and the likely collapse modes of frame structures under uncertain load and member strength are investigated under assumption of normal distributed and non-normal distributed external loads and member strength. It is found that the occurrence order of likely collapse mode is much influenced by the distribution of the random variables. The occurrence order of collapse modes for column over designed structures are investigated and it is found that the increase of column over-design factor can effectively avoid the story collapse mode in probabilistic means.
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Appourchaux, T. "On attempting to automate the identification of mixed dipole modes for subgiant stars." Astronomy & Astrophysics 642 (October 2020): A226. http://dx.doi.org/10.1051/0004-6361/202038834.
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Context. The existence of mixed modes in stars is a marker of stellar evolution. Their detection serves for a better determination of stellar age. Aims. The goal of this paper is to identify the dipole modes in an automatic manner without human intervention. Methods. I used the power spectra obtained by the Kepler mission for the application of the method. I computed asymptotic dipole mode frequencies as a function of the coupling factor and dipole period spacing, as well as other parameters. For each star, I collapsed the power in an echelle diagramme aligned onto the monopole and dipole mixed modes. The power at the null frequency was used as a figure of merit. Using a genetic algorithm, I then optimised the figure of merit by adjusting the location of the dipole frequencies in the power spectrum. Using published frequencies, I compared the asymptotic dipole mode frequencies with published frequencies. I also used published frequencies to derive the coupling factor and dipole period spacing using a non-linear least squares fit. I used Monte-Carlo simulations of the non-linear least square fit to derive error bars for each parameter. Results. From the 44 subgiants studied, the automatic identification allows one to retrieve within 3 μHz, at least 80% of the modes for 32 stars, and within 6 μHz, at least 90% of the modes for 37 stars. The optimised and fitted gravity-mode period spacing and coupling factor are in agreement with previous measurements. Random errors for the mixed-mode parameters deduced from the Monte-Carlo simulation are about 30−50 times smaller than previously determined errors, which are in fact systematic errors. Conclusions. The period spacing and coupling factors of mixed modes in subgiants are confirmed. The current automated procedure will need to be improved upon using a more accurate asymptotic model and/or proper statistical tests.
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TURNER, LEAF. "Using helicity to characterize homogeneous and inhomogeneous turbulent dynamics." Journal of Fluid Mechanics 408 (April 10, 2000): 205–38. http://dx.doi.org/10.1017/s002211209900779x.
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The ability of the helicity decomposition to describe compactly the dynamics of three-dimensional incompressible fluids is invoked to obtain new descriptions of both homogeneous and inhomogeneous turbulence. We first use this decomposition to derive four coupled nonlinear equations that describe an arbitrary three-dimensional turbulence, whether anisotropic and/or non-mirror-symmetric. We then use the decomposition to treat the inhomogeneous turbulence of a channel flow bounded by two parallel free-slip boundaries with almost the ease with which the homogeneous case has heretofore received treatment. However, this ease arises from the foundation of a random-phase hypothesis, which we introduce and motivate, that supersedes the translational invariance of a turbulence that is hypothesized to be homogeneous. For the description of this channel turbulence, we find that the three-dimensional modes and the two-dimensional modes having wave vectors parallel to the boundaries each couple precisely as in a homogeneous turbulence of the corresponding dimension. The anisotropy and inhomogeneity is in large part a feature incorporated into the solenoidal basis vectors used to describe an arbitrary solenoidal free-slip flow within the channel. We invoke the random-phase hypothesis, a feature of the dynamics, with closures, such as Kraichnan's direct-interaction approximation and his test-field model, in addition to the one most utilized in this manuscript, the eddy-damped quasi-normal Markovian (EDQNM) closure.
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Cheng, Sihan, Zhe Tian, Xia Wu, and Jide Niu. "Bottom-Up Model of Random Daily Electrical Load Curve for Office Building." Applied Sciences 11, no. 21 (November 8, 2021): 10471. http://dx.doi.org/10.3390/app112110471.
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In the design stage of energy systems in buildings, accurate load boundary conditions are the key to achieving energy supply and demand balance. Compared with the building cold and heat load, the generation of building electrical load has stronger randomness, and the current standard electrical load calculation method cannot reflect this feature. Therefore, this paper proposes a bottom-up high time resolution power load generation method for office buildings. Firstly, the non-homogeneous Markov chain is used to establish the random mobility model of personnel in office buildings, and the building electrical appliances are divided into four categories according to the different driving modes of personnel to electrical appliances in office buildings. Then, based on the personnel mobility model, the correlation between the use of electrical appliances in office buildings and the personnel in the room is established to construct the random power simulation model of different types of electrical appliances. Finally, the electric load of different types of electrical appliances is superimposed hourly to generate a random daily load curve. In order to verify the validity of the model, an office building is simulated and compared with the measured electrical load value. The verification results show that the model well reflects the daily distribution characteristics of electric load. The simulation value and the measured value are used for statistical analysis. The evaluation results show that the correlation between the simulation value and the measured value is high, which further illustrates the validity and accuracy of the model.
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Klauzner, P. S., D. G. Rudakov, E. A. Anokhina, and A. V. Timoshenko. "Optimal modes of side-section flow in heat-pump-assisted extractive distillation systems for separating allyl alcohol–allyl acetate mixtures with butyl propionate." Fine Chemical Technologies 16, no. 3 (July 22, 2021): 213–24. http://dx.doi.org/10.32362/2410-6593-2021-16-3-213-224.
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Objectives. To investigate the influence of side-section flow modes on the energy efficiency of a partially thermally coupled distillation sequence (PTCDS) with a vapor recompression heat pump for the extractive distillation of an allyl alcohol–allyl acetate mixture with n-butyl propionate and identify modes under which the combined use of a PTCDS and heat pump are the most efficient.Methods. Mathematical modeling in the Aspen Plus V10 software package was used as the main research method. The local composition equation of the non-random two-liquid model was used as a model for describing the vapor–liquid equilibrium, while the Redlich–Kwong model was used to consider the non-ideal vapor phase. When modeling the conventional extractive distillation scheme and PTCDS, parametric optimization was carried out according to the criterion of the total energy costs in the column reboilers. For the economical evaluation, Aspen Process Economic Analyzer V10.1 tools were used.Results. For extractive distillation of a mixture of allyl alcohol (30 wt %) and allyl acetate (70 wt %) with n-butyl propionate as an entrainer, the minimum energy consumption was achieved at the same side-section flow mode for the variants of a PTCDS with and without a heat pump. The reduction in energy costs relative to the conventional scheme was 20% for the sequence without a heat pump and 38% for that with a heat pump. An economic assessment was made of the best options in comparison with the conventional extractive distillation scheme. The PTCDS with a heat pump had an advantage over the sequence without a heat pump only for long periods of operation.Conclusions. For the extractive distillation of an allyl alcohol–allyl acetate mixture, the optimal modes for the combined use of a PTCDS with a vapor recompression heat pump coincide with the optimal modes for a PTCDS without a heat pump.
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Elkasabi, Mahmoud, Z. Tuba Suzer-Gurtekin, James M. Lepkowski, Uiyoung Kim, Richard Curtin, and Rebecca Mcbee. "A Comparison of ABS Mail and RDD Surveys for Measuring Consumer Attitudes." International Journal of Market Research 56, no. 6 (November 2014): 737–56. http://dx.doi.org/10.2501/ijmr-2014-017.
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The increasing cost and decreasing coverage of Random Digit Dialing (RDD) landline telephone surveys motivated The Surveys of Consumer Attitudes (SCA) at the University of Michigan to conduct monthly experimental mail survey studies using address-based sampling (ABS). The primary objectives of the experimental studies were to evaluate the feasibility of transitioning the data collection operations from telephone to mail and to investigate differential survey errors between the two modes. Overall mail survey response rates were comparable to the RDD landline survey. Coverage improved using ABS, with more than 20% of the mail responses from non-landline telephone households not covered by the RDD landline telephone surveys. Mail survey respondents from households without landline telephones were more likely to be younger, have lower income, be renters and live in one-person households. There were no apparent measurement or reporting differences between the telephone and mail self-administered modes of data collection. Furthermore, inclusion of non-landline telephone households did not result in any substantial demographic or economic attitude differences between the two approaches.
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SHAIKH, DASTGEER, B. DASGUPTA, Q. HU, and G. P. ZANK. "Self-organization in a driven dissipative plasma system." Journal of Plasma Physics 76, no. 1 (April 30, 2009): 107–16. http://dx.doi.org/10.1017/s0022377809008058.
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AbstractWe perform a fully self-consistent three-dimensional numerical simulation for a compressible, dissipative magnetoplasma driven by large-scale perturbations, that contain a fairly broad spectrum of characteristic modes, ranging from largest scales to intermediate scales and down to the smallest scales, where the energy of the system is dissipated by collisional (ohmic) and viscous dissipations. Additionally, our simulation includes nonlinear interactions amongst a wide range of fluctuations that are initialized with random spectral amplitudes, leading to the cascade of spectral energy in the inertial range spectrum, and takes into account large-scale as well as small-scale perturbations that may have been induced by the background plasma fluctuations, as well as the non-adiabatic exchange of energy leading to the migration of energy from the energy-containing modes or randomly injected energy driven by perturbations and further dissipated by the smaller scales. Besides demonstrating the comparative decays of the total energy and the dissipation rate of the energy, our results show the existence of a perpendicular component of the current, thus clearly confirming that the self-organized state is non-force free.
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Ibrahim, R. A., B. H. Lee, and A. A. Afaneh. "Structural Modal Multifurcation With Internal Resonance: Part 2—Stochastic Approach." Journal of Vibration and Acoustics 115, no. 2 (April 1, 1993): 193–201. http://dx.doi.org/10.1115/1.2930330.
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Stochastic bifurcation in moments of a clamped-clamped beam response to a wide band random excitation is investigated analytically, numerically, and experimentally. The nonlinear response is represented by the first three normal modes. The response statistics are examined in the neighborhood of a critical static axial load where the normal mode frequencies are commensurable. The analytical treatment includes Gaussian and non-Gaussian closures. The Gaussian closure fails to predict bifurcation of asymmetric modes. Both non-Gaussian closure and numerical simulation yield bifurcation boundaries in terms of the axial load, excitation spectral density level, and damping ratios. The results of both methods are in good agreement only for symmetric response characteristics. In the neighborhood of the critical bifurcation parameter the Monte Carlo simulation yields strong nonstationary mean square response for the asymmetric mode which is not directly excited. Experimental and Monte Carlo simulation exhibit nonlinear features including a shift of the resonance peak in the response spectra as the excitation level increases. The observed shift is associated with a widening effect in the response bandwidth.
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Glizer, Valery Y., and Vladimir Turetsky. "Increasing Pursuer Capturability by Using Hybrid Dynamics." International Journal of Applied Mathematics and Computer Science 25, no. 1 (March 1, 2015): 77–92. http://dx.doi.org/10.1515/amcs-2015-0006.
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Abstract A robust interception of a maneuverable target (evader) by an interceptor (pursuer) with hybrid dynamics is considered. The controls of the pursuer and the evader are bounded. The duration of the engagement is prescribed. The pursuer has two possible dynamic modes, which can be switched once during the engagement, while the dynamics of the evader are fixed. The case where for both dynamic modes there exists an unbounded capture zone was analyzed in our previous work. The conditions under which the pursuer can increase its capturability by utilizing the hybrid dynamics were established and the new robust capture zone was constructed. In the present paper, we extend this result to the cases where at least for one dynamic mode of the pursuer the capture zone is bounded. For these instances, conditions of increasing the pursuer’s hybrid capturability are derived. Respective capture zones are constructed. Illustrative examples and results of extensive simulation for a realistic non-linear engagement model in the presence of a random wind are given.
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Dolgopolov, B. A., Yu G. Zayko, V. A. Mikhailov, and A. V. Trakhtomirov. "Calculation of an SPTA set using the Dialog computer simulation system (Part 1. General provisions for the calculation of an SPTA set)." Dependability 20, no. 1 (March 30, 2020): 32–38. http://dx.doi.org/10.21683/1729-2646-2020-20-1-32-38.
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The paper describes the design concept of the DIALOG simulation software suite (SSS) intended for calculating the dependability indicators of electronic systems (ES) of random configuration, as well as solving problems associated with assuring the functional dependability of such systems. The DIALOG SSS employs a specially designed DIALOG-SINTEZ technology that enables automatic synthesis of event simulation models in the form of programs in the selected programming language. In DIALOG SSS, the input data include: system composition in the form of a combination of conventional blocks; criteria of failure event occurrence and repairs; random value parameters (failures of system components in various modes of operation, SPTA requests, etc.); stages of system operation and types of repairs; list of calculated indicators. For the purpose of ensuring the required indicators, the simulation models undergo statistical testing under modified indicators of random values in each new test. Based on the accumulated results of all the performed tests the required indicators are calculated. The DIALOG SSS consists of four components: DIALOG-NRS is intended for the calculation of dependability indicators of non-repairable redundant systems; DIALOG-RRS is intended for the calculation of dependability indicators of repairable redundant systems, as well as the number of and cost of warranty repairs; DIALOG-ZIP-NS is intended for SPTA sets calculation for simple non-redundant systems; DIALOG-ZIP-RS is intended for SPTA sets calculation for any redundant systems. SPTA set calculation is normally done using standard procedures described in regulatory documents. In solving the direct problem of optimal SPTA set calculation, the input data includes the required value of one of the two SPTA sufficiency indicators (SI) and type of costs that are to be optimized (minimized) in order to achieve the target values of SI. In solving the inverse problem of optimal SPTA set calculation, it is required to ensure the specified costs of the initial SPTA supply. As the SPTA supply SI, the mean spare parts (SP) supply delay time out of SPTA Δtd.SPTA and SPTA availability coefficient Ca.SPTA are used. SPTA optimization using the DIALOG-ZIP SSS allows improving user options through the following additional characteristics: SPTA SP failure logging; optimization of SP count and accounting for the their characteristic features for the purpose of SP emergency delivery (ED); capability to use products with any type of redundancy; when using SPTA-G group set, capability to include differently-structured products into ESs. The paper sets forth the structure diagram of the DIALOG SSS programs interaction, that implies three modes of operation of the simulation model: SI calculation for specific SPTA contents; calculation of preliminary SPTA supply before the beginning of optimization; calculation of optimal SPTA set. The authors examine the matters related to the selection of the required number and duration of simulation model testing.
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IJZERMANS, RUTGER H. A., ELENA MENEGUZ, and MICHAEL W. REEKS. "Segregation of particles in incompressible random flows: singularities, intermittency and random uncorrelated motion." Journal of Fluid Mechanics 653 (April 13, 2010): 99–136. http://dx.doi.org/10.1017/s0022112010000170.
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The results presented here are part of a long-term study in which we analyse the segregation of inertial particles in turbulent flows using the so called full Lagrangian method (FLM) to evaluate the ‘compressibility’ of the particle phase along a particle trajectory. In the present work, particles are advected by Stokes drag in a random flow field consisting of counter-rotating vortices and in a flow field composed of 200 random Fourier modes. Both flows are incompressible and, like turbulence, have structure and a distribution of scales with finite lifetime. The compressibility is obtained by first calculating the deformation tensor Jij associated with an infinitesimally small volume of particles following the trajectory of an individual particle. The fraction of the initial volume occupied by the particles centred around a position x at time t is denoted by |J|, where J ≡ det(Jij) and Jij ≡ ∂xi(x0, t)/∂x0,j, x0 denoting the initial position of the particle. The quantity d〈ln|J|〉/dt is shown to be equal to the particle averaged compressibility of the particle velocity field 〈∇ · v〉, which gives a measure of the rate-of-change of the total volume occupied by the particle phase as a continuum. In both flow fields the compressibility of the particle velocity field is shown to decrease continuously if the Stokes number St (the dimensionless particle relaxation time) is below a threshold value Stcr, indicating that the segregation of particles continues indefinitely. We show analytically and numerically that the long-time limit of 〈∇ · v〉 for sufficiently small values of St is proportional to St2 in the flow field composed of random Fourier modes, and to St in the flow field consisting of counter-rotating vortices. If St > Stcr, however, the particles are ‘mixed’. The level of mixing can be quantified by the degree of random uncorrelated motion (RUM) of particles which is a measure of the decorrelation of the velocities of two nearby particles. RUM is zero for fluid particles and increases rapidly with the Stokes number if St > Stcr, approaching unity for St ≫ 1. The spatial averages of the higher-order moments of the particle number density are shown to diverge with time indicating that the spatial distribution of particles may be very intermittent, being associated with non-zero values of RUM and the occurrence of singularities in the particle velocity field. Our results are consistent with previous observations of the radial distribution function in Chun et al. (J. Fluid Mech., vol. 536, 2005, p. 219).
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Rodríguez-Martín, Manuel, José G. Fueyo, Diego Gonzalez-Aguilera, Francisco J. Madruga, Roberto García-Martín, Ángel Luis Muñóz, and Javier Pisonero. "Predictive Models for the Characterization of Internal Defects in Additive Materials from Active Thermography Sequences Supported by Machine Learning Methods." Sensors 20, no. 14 (July 17, 2020): 3982. http://dx.doi.org/10.3390/s20143982.
Full textAbstract:
The present article addresses a generation of predictive models that assesses the thickness and length of internal defects in additive manufacturing materials. These modes use data from the application of active transient thermography numerical simulation. In this manner, the raised procedure is an ad-hoc hybrid method that integrates finite element simulation and machine learning models using different predictive feature sets and characteristics (i.e., regression, Gaussian regression, support vector machines, multilayer perceptron, and random forest). The performance results for each model were statistically analyzed, evaluated, and compared in terms of predictive performance, processing time, and outlier sensibility to facilitate the choice of a predictive method to obtain the thickness and length of an internal defect from thermographic monitoring. The best model to predictdefect thickness with six thermal features was interaction linear regression. To make predictive models for defect length and thickness, the best model was Gaussian process regression. However, models such as support vector machines also had significative advantages in terms of processing time and adequate performance for certain feature sets. In this way, the results showed that the predictive capability of some types of algorithms could allow for the detection and measurement of internal defects in materials produced by additive manufacturing using active thermography as a non-destructive test.
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Weber, Hanna, Stefan Kaczmarczyk, and Radosław Iwankiewicz. "Non-linear dynamic response of a cable system with a tuned mass damper to stochastic base excitation via equivalent linearization technique." Meccanica 55, no. 12 (May 20, 2020): 2413–22. http://dx.doi.org/10.1007/s11012-020-01169-3.
Full textAbstract:
AbstractNon-linear dynamic model of a cable–mass system with a transverse tuned mass damper is considered. The system is moving in a vertical host structure therefore the cable length varies slowly over time. Under the time-dependent external loads the sway of host structure with low frequencies and high amplitudes can be observed. That yields the base excitation which in turn results in the excitation of a cable system. The original model is governed by a system of non-linear partial differential equations with corresponding boundary conditions defined in a slowly time-variant space domain. To discretise the continuous model the Galerkin method is used. The assumption of the analysis is that the lateral displacements of the cable are coupled with its longitudinal elastic stretching. This brings the quadratic couplings between the longitudinal and transverse modes and cubic nonlinear terms due to the couplings between the transverse modes. To mitigate the dynamic response of the cable in the resonance region the tuned mass damper is applied. The stochastic base excitation, assumed as a narrow-band process mean-square equivalent to the harmonic process, is idealized with the aid of two linear filters: one second-order and one first-order. To determine the stochastic response the equivalent linearization technique is used. Mean values and variances of particular random state variable have been calculated numerically under various operational conditions. The stochastic results have been compared with the deterministic response to a harmonic process base excitation.