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1
Kuzenov, Victor V., Sergei V. Ryzhkov, and Aleksey Yu Varaksin. "Calculation of Heat Transfer and Drag Coefficients for Aircraft Geometric Models." Applied Sciences 12, no. 21 (October 30, 2022): 11011. http://dx.doi.org/10.3390/app122111011.
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A numerical model to calculate the heat transfer and resistance coefficients near the bodies of complex geometric shapes moving at high velocity is formulated. The processes of heat and mass transfer and flow around aircraft elements are considered. An algorithm for calculating heat fluxes and the heat transfer coefficient is proposed. The developed numerical technique can give an idea of the essential features of the flow, heat transfer at the end keels of the wings, and integral layouts of high-speed aircraft. An approximate mathematical model for calculating the heat transfer processes and resistance coefficients near the bodies of complex geometric shapes moving at high speed in the Earth’s atmosphere is formulated. The calculated results for convective heat transfer and friction coefficients for the X-33 and X-43 vehicles are obtained.
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Flay, R. G. J., and D. C. McMillan. "A Wind Tunnel Investigation of Yacht Hydrodynamic Side Force and Drag." Journal of Ship Research 37, no. 04 (December 1, 1993): 331–41. http://dx.doi.org/10.5957/jsr.1993.37.4.331.
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Measurements of side force and drag on models of various yacht hull/keel combinations in a wind tunnel are presented. The accuracy of the resulting side force measurements was verified by comparing results for two of the standard configurations with towing tank data from geometrically identical models at the same Reynolds number. The agreement between the results was excellent. Measurements from the models were then compared with the predictions of five different methods for a range of keel to canoe body draft ratios from 2.27 to 5.56. It was found that there was considerable variation in the predictions of the various methods, but that the wind tunnel results fell at the center of the range of predicted values. Effective aspect ratios were estimated from induced drag measurements and were found to be in excess of twice the geometric aspect ratio of the keels, reducing as heel increased to 30 deg.
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Ovaskainen, Otso, Panu Somervuo, and Dmitri Finkelshtein. "A general mathematical method for predicting spatio-temporal correlations emerging from agent-based models." Journal of The Royal Society Interface 17, no. 171 (October 2020): 20200655. http://dx.doi.org/10.1098/rsif.2020.0655.
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Agent-based models are used to study complex phenomena in many fields of science. While simulating agent-based models is often straightforward, predicting their behaviour mathematically has remained a key challenge. Recently developed mathematical methods allow the prediction of the emerging spatial patterns for a general class of agent-based models, whereas the prediction of spatio-temporal pattern has been thus far achieved only for special cases. We present a general and mathematically rigorous methodology that allows deriving the spatio-temporal correlation structure for a general class of individual-based models. To do so, we define an auxiliary model, in which each agent type of the primary model expands to three types, called the original, the past and the new agents. In this way, the auxiliary model keeps track of both the initial and current state of the primary model, and hence the spatio-temporal correlations of the primary model can be derived from the spatial correlations of the auxiliary model. We illustrate the agreement between analytical predictions and agent-based simulations using two example models from theoretical ecology. In particular, we show that the methodology is able to correctly predict the dynamical behaviour of a host–parasite model that shows spatially localized oscillations.
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Reinharz, Vladimir, Alexander Churkin, Harel Dahari, and Danny Barash. "Advances in Parameter Estimation and Learning from Data for Mathematical Models of Hepatitis C Viral Kinetics." Mathematics 10, no. 12 (June 19, 2022): 2136. http://dx.doi.org/10.3390/math10122136.
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Mathematical models, some of which incorporate both intracellular and extracellular hepatitis C viral kinetics, have been advanced in recent years for studying HCV–host dynamics, antivirals mode of action, and their efficacy. The standard ordinary differential equation (ODE) hepatitis C virus (HCV) kinetic model keeps track of uninfected cells, infected cells, and free virus. In multiscale models, a fourth partial differential equation (PDE) accounts for the intracellular viral RNA (vRNA) kinetics in an infected cell. The PDE multiscale model is substantially more difficult to solve compared to the standard ODE model, with governing differential equations that are stiff. In previous contributions, we developed and implemented stable and efficient numerical methods for the multiscale model for both the solution of the model equations and parameter estimation. In this contribution, we perform sensitivity analysis on model parameters to gain insight into important properties and to ensure our numerical methods can be safely used for HCV viral dynamic simulations. Furthermore, we generate in-silico patients using the multiscale models to perform machine learning from the data, which enables us to remove HCV measurements on certain days and still be able to estimate meaningful observations with a sufficiently small error.
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Calabrese, Peter P., Richard T. Durrett, and Charles F. Aquadro. "Dynamics of Microsatellite Divergence Under Stepwise Mutation and Proportional Slippage/Point Mutation Models." Genetics 159, no. 2 (October 1, 2001): 839–52. http://dx.doi.org/10.1093/genetics/159.2.839.
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Abstract Recently Kruglyak, Durrett, Schug, and Aquadro showed that microsatellite equilibrium distributions can result from a balance between polymerase slippage and point mutations. Here, we introduce an elaboration of their model that keeps track of all parts of a perfect repeat and a simplification that ignores point mutations. We develop a detailed mathematical theory for these models that exhibits properties of microsatellite distributions, such as positive skewness of allele lengths, that are consistent with data but are inconsistent with the predictions of the stepwise mutation model. We use our theoretical results to analyze the successes and failures of the genetic distances (δμ)2 and DSW when used to date four divergences: African vs. non-African human populations, humans vs. chimpanzees, Drosophila melanogaster vs. D. simulans, and sheep vs. cattle. The influence of point mutations explains some of the problems with the last two examples, as does the fact that these genetic distances have large stochastic variance. However, we find that these two features are not enough to explain the problems of dating the human-chimpanzee split. One possible explanation of this phenomenon is that long microsatellites have a mutational bias that favors contractions over expansions.
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Barclay, Pat. "Reciprocity creates a stake in one's partner, or why you should cooperate even when anonymous." Proceedings of the Royal Society B: Biological Sciences 287, no. 1929 (June 17, 2020): 20200819. http://dx.doi.org/10.1098/rspb.2020.0819.
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Why do we care so much for friends, even making sacrifices for them they cannot repay or never know about? When organisms engage in reciprocity, they have a stake in their partner's survival and wellbeing so the reciprocal relationship can persist. This stake (aka fitness interdependence) makes organisms willing to help beyond the existing reciprocal arrangement (e.g. anonymously). I demonstrate this with two mathematical models in which organisms play a prisoner's dilemma, and where helping keeps their partner alive and well. Both models shows that reciprocity creates a stake in partners' welfare: those who help a cooperative partner––even when anonymous––do better than those who do not, because they keep that cooperative partner in good enough condition to continue the reciprocal relationship. ‘Machiavellian' cooperators, who defect when anonymous, do worse because their partners become incapacitated. This work highlights the fact that reciprocity and stake are not separate evolutionary processes, but are inherently linked.
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Cortés, J. C., J. V. Romero, M. D. Roselló, Francisco-J. Santonja, and Rafael-J. Villanueva. "Solving Continuous Models with Dependent Uncertainty: A Computational Approach." Abstract and Applied Analysis 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/983839.
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This paper presents a computational study on a quasi-Galerkin projection-based method to deal with a class of systems of random ordinary differential equations (r.o.d.e.’s) which is assumed to depend on a finite number of random variables (r.v.’s). This class of systems of r.o.d.e.’s appears in different areas, particularly in epidemiology modelling. In contrast with the other available Galerkin-based techniques, such as the generalized Polynomial Chaos, the proposed method expands the solution directly in terms of the random inputs rather than auxiliary r.v.’s. Theoretically, Galerkin projection-based methods take advantage of orthogonality with the aim of simplifying the involved computations when solving r.o.d.e.’s, which means to compute both the solution and its main statistical functions such as the expectation and the standard deviation. This approach requires the previous determination of an orthonormal basis which, in practice, could become computationally burden and, as a consequence, could ruin the method. Motivated by this fact, we present a technique to deal with r.o.d.e.’s that avoids constructing an orthogonal basis and keeps computationally competitive even assuming statistical dependence among the random input parameters. Through a wide range of examples, including a classical epidemiologic model, we show the ability of the method to solve r.o.d.e.’s.
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Willis, David H., and B. G. Krishnappan. "Numerical modelling of cohesive sediment transport in rivers." Canadian Journal of Civil Engineering 31, no. 5 (October 1, 2004): 749–58. http://dx.doi.org/10.1139/l04-043.
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Techniques available to practicing civil engineers for numerically modelling cohesive mud in rivers and estuaries are reviewed. Coupled models, treating water and sediment as a single process, remain research tools but are usually not three-dimensional. The decoupled approach, which separates water and sediment computations at each model time step, allows the three-dimensional representation of at least the bed and the use of well-proven, commercial, numerical, hydrodynamic models. Most hydrodynamic models compute sediment transport in suspension but may require modification of the dispersion coefficients to account for the presence of sediment. The sediment model deals with the sediment exchange between the water column and the bed using existing equations for erosion and deposition. Both equations relate the sediment exchange rates to the shear stress in the bottom boundary layer. In real rivers and estuaries, a depositional bed layer is associated with a period of low flow and shear, at slack tide for example, whereas in numerical models a layer is defined by the model time step. The sediment model keeps track of the uppermost layers at each model grid point, including consolidation and strengthening. Although numerical hydrodynamic models are based strongly on physics, sediment models are only numerical frameworks for interpolating and extrapolating full-scale field or laboratory measurements of "hydraulic sediment parameters," such as threshold shear stresses. Calibration and verification of models against measurement are therefore of prime importance.Key words: cohesive sediment, mathematical modelling, settling velocity, erosion, resuspension, deposition, fluid mud, bed layers.
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Bhar, Aliyu Kisabo. "Design & implementation of a personal Cash flow program using Microsoft Excel®." Global Journal of Business, Economics and Management: Current Issues 9, no. 1 (March 31, 2019): 29–40. http://dx.doi.org/10.18844/gjbem.v9i1.4032.
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A program that keeps record of personal financial details and also mines the data for insightful analysis is definitely a good day-to-day companion. In this generation, such tool is inevitable in the financial dealings of any individual or company. In this study, we developed an easy but highly intuitive method of tracking financial dealings, budgeting and forecasting personal financial expenditure using Microsoft Excel®. Among others, this program can aid in implementing financial strategies designed to meet specific goals based on percentages in specific categories. From such data, mathematical models were also developed and prediction was made. With little or no modification, the Cash flow program presented in this study could be adopted for use in any type of the organisation where money or any article of business comes in and goes out in a particular cycle (typical of which is monthly). Results and method presented here proved to be effective. Keywords: Cash flow, Microsoft Excel, budget, forecast.
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Mao, Xinna, Zhao Guoxi, Mohammad Fallah, and S. A. Edalatpanah. "A Neutrosophic-Based Approach in Data Envelopment Analysis with Undesirable Outputs." Mathematical Problems in Engineering 2020 (July 13, 2020): 1–8. http://dx.doi.org/10.1155/2020/7626102.
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Data Envelopment Analysis is one of the paramount mathematical methods to compute the general performance of organizations, which utilizes similar sources to produce similar outputs. Original DEA schemes involve crisp information of inputs and outputs that may not always be accessible in real-world applications. Nevertheless, in some cases, the values of the data are information with indeterminacy, impreciseness, vagueness, inconsistent, and incompleteness. Furthermore, the conventional DEA models have been originally formulated solely for desirable outputs. However, undesirable outputs may additionally be present in the manufacturing system, which wishes to be minimized. To tackle the mentioned issues and in order to obtain a reliable measurement that keeps original advantage of DEA and considers the influence of undesirable factors under the indeterminate environments, this paper presents a neutrosophic DEA model with undesirable outputs. The recommended technique is based on the aggregation operator and has a simple construction. Finally, an example is given to illustrate the new model and ranking approach in details.
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MAUSER, NORBERT J., and SABER TRABELSI. "L2 ANALYSIS OF THE MULTI-CONFIGURATION TIME-DEPENDENT HARTREE–FOCK EQUATIONS." Mathematical Models and Methods in Applied Sciences 20, no. 11 (November 2010): 2053–73. http://dx.doi.org/10.1142/s0218202510004842.
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The multi-configuration methods are widely used by quantum physicists/chemists for numerical approximation of the many electron Schrödinger equation. Recently, first mathematically rigorous results were obtained on the time-dependent models, e.g. short-in-time well-posedness in the Sobolev space H2 for bounded interactions20 with initial data in H2, in the energy space for Coulomb interactions with initial data in the same space,25,5 as well as global well-posedness under a sufficient condition on the energy of the initial data.4,5 The present contribution extends the analysis by setting an L2 theory for the MCTDHF for general interactions including the Coulomb case. This kind of results is also the theoretical foundation of ad hoc methods used in numerical calculation when modification ("regularization") of the density matrix destroys the conservation of energy property, but keeps the mass invariant.
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Sutikno, Tole, Syahid Hikmatul Wahid, Rizky Ajie Aprilianto, Arsyad Cahya Subrata, and Auzani Jidin. "An Automatic Wind Turbine Braking System on PLTH Bayu Baru through a Fuzzy Logic Controller." JURNAL NASIONAL TEKNIK ELEKTRO 11, no. 1 (March 29, 2022): 1–7. http://dx.doi.org/10.25077/jnte.v11n1.887.2022.
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PLTH Bayu Baru is one of the hybrid power plants (HPP) located in Baru beach, Pandansimo, Bantul, Yogyakarta, Indonesia. It generates electrical energy from two sources, wind and solar energy. However, a problem is encountered regarding wind turbine mechanics due to using a manual switch for braking during periods of excessive wind speed. This study proposes an automatic wind turbine braking system through a utilized fuzzy logic controller (FLC) for the PLTH Bayu Baru application. The Mamdani type FLC without complex mathematical models is applied to the Arduino Uno development board to realize the proposed systems. The error (Error_V) and delta error (dError_V) values from the generator voltage sensor become the input of the proposed systems, while the pulse width modulation (PWM) becomes the output for controlling the on/off period of the MOSFET as switching devices. The proposed systems have been tested on a micro-scale wind turbine with PMSG 12V/400W type. From the testing results, the proposed system successfully braked automatically at the point wherein the generator voltage exceeds the setpoint value. Also, the proposed system keeps the generator voltage less than 13.8V, so the problem caused by excessive speed can be resolved.
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Rangel-Valdez, Nelson, Eduardo Fernandez, Laura Cruz-Reyes, Claudia Gomez-Santillan, Gilberto Rivera, and Rogelio Florencia. "Robustness Analysis of an Outranking Model Parameters’ Elicitation Method in the Presence of Noisy Examples." Mathematical Problems in Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/2157937.
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One of the main concerns in Multicriteria Decision Aid (MCDA) is robustness analysis. Some of the most important approaches to model decision maker preferences are based on fuzzy outranking models whose parameters (e.g., weights and veto thresholds) must be elicited. The so-called preference-disaggregation analysis (PDA) has been successfully carried out by means of metaheuristics, but this kind of works lacks a robustness analysis. Based on the above, the present research studies the robustness of a PDA metaheuristic method to estimate model parameters of an outranking-based relational system of preferences. The method is considered robust if the solutions obtained in the presence of noise can maintain the same performance in predicting preference judgments in a new reference set. The research shows experimental evidence that the PDA method keeps the same performance in situations with up to 10% of noise level, making it robust.
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Hao-ling, Ren, Lin Tianliang, Xie Hai-bo, and Yang Hua-yong. "Stability research of the compression process of two-cylinder four-stroke single-piston hydraulic free piston engine." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, no. 15 (March 24, 2016): 2902–11. http://dx.doi.org/10.1177/0954406216640577.
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An invariable compression ratio in certain conditions must be achieved to ensure a steady and efficient performance of the single-piston hydraulic free piston engine. The compression ratio is determined by the characteristics of the compression stroke. The mathematical models of the key components during the compression process are established. The kinematic characteristics of the free piston assembly are analyzed under two conditions. One condition is that free piston assembly is driven by the compression accumulator only and the other one is that free piston assembly is driven by the compression accumulator and the pump station. Pressures in compression accumulator and compression chamber are analyzed and compared in both conditions. According to the experimental results, pressures in the compression chamber and compression accumulator are not constant in both conditions during the compression process. The compression stroke and compression time vary with the changing of the pressure in the compression accumulator, which adds the complexity and changeability to the compression ratio control. An improved configuration is put forward to solve the pressure variation. The results show that the improved configuration can make the pressure invariable at the inlet of the compression chamber and the compression process keeps almost the same regardless of the pressure changing in the compression accumulator. With this new structure, there is about 2.5% energy loss, which is acceptable considering the stable compression stroke.
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Wu, Jinglai, Zhen Luo, Nong Zhang, and Wei Gao. "A new sequential sampling method for constructing the high-order polynomial surrogate models." Engineering Computations 35, no. 2 (April 16, 2018): 529–64. http://dx.doi.org/10.1108/ec-05-2016-0160.
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Purpose This paper aims to study the sampling methods (or design of experiments) which have a large influence on the performance of the surrogate model. To improve the adaptability of modelling, a new sequential sampling method termed as sequential Chebyshev sampling method (SCSM) is proposed in this study. Design/methodology/approach The high-order polynomials are used to construct the global surrogated model, which retains the advantages of the traditional low-order polynomial models while overcoming their disadvantage in accuracy. First, the zeros of Chebyshev polynomials with the highest allowable order will be used as sampling candidates to improve the stability and accuracy of the high-order polynomial model. In the second step, some initial sampling points will be selected from the candidates by using a coordinate alternation algorithm, which keeps the initial sampling set uniformly distributed. Third, a fast sequential sampling scheme based on the space-filling principle is developed to collect more samples from the candidates, and the order of polynomial model is also updated in this procedure. The final surrogate model will be determined as the polynomial that has the largest adjusted R-square after the sequential sampling is terminated. Findings The SCSM has better performance in efficiency, accuracy and stability compared with several popular sequential sampling methods, e.g. LOLA-Voronoi algorithm and global Monte Carlo method from the SED toolbox, and the Halton sequence. Originality/value The SCSM has good performance in building the high-order surrogate model, including the high stability and accuracy, which may save a large amount of cost in solving complicated engineering design or optimisation problems.
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PANASENKO, GRIGORY. "THE PARTIAL HOMOGENIZATION: CONTINUOUS AND SEMI-DISCRETIZED VERSIONS." Mathematical Models and Methods in Applied Sciences 17, no. 08 (August 2007): 1183–209. http://dx.doi.org/10.1142/s0218202507002248.
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The partial homogenization is a new method for the treatment of the boundary layers in the homogenization theory. It keeps the initial formulation near the boundary, passes to the high order homogenization at some distance from the boundary and prescribes the asymptotically precise junction conditions between the homogenized and the heterogeneous models at the interface. This method is related to the method of asymptotic partial domain decomposition MAPDD (see G. Panasenko, Method of asymptotic partial decomposition of domain, Math. Mod. Meth. Appl. Sci.8 (1998) 139–156). The partial homogenization (as well as the MAPDD) can be interpreted as a multi-scale model coupling the homogenized (macroscopic) description in the internal main part of the domain and the microscopic zoom in the domain of the location of the boundary layers. The semi-discretized partial homogenization uses some high order finite element projection in the homogenized subdomain.
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Tucker, V. A. "Gliding flight: drag and torque of a hawk and a falcon with straight and turned heads, and a lower value for the parasite drag coefficient." Journal of Experimental Biology 203, no. 24 (December 15, 2000): 3733–44. http://dx.doi.org/10.1242/jeb.203.24.3733.
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Raptors - falcons, hawks and eagles in this study - such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 degrees to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s(−)(1). With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct. The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor's higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals. In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (C(D,par)) of 0.18 previously used for calculating the gliding performance of a peregrine. The accuracy with which drag coefficients measured on wingless bird bodies in a wind tunnel represent the C(D,par) of a living bird is unknown. Another method for determining C(D,par) selects values that improve the fit between speeds predicted by mathematical models and those observed in living birds. This method yields lower values for C(D,par) (0.05-0.07) than wind tunnel measurements, and the present study suggests a value of 0.1 for raptors as a compromise.
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Ma, Guifen, Ping Chen, Zhaoshan Liu, and Jia Liu. "The Prediction of Enterprise Stock Change Trend by Deep Neural Network Model." Computational Intelligence and Neuroscience 2022 (August 2, 2022): 1–9. http://dx.doi.org/10.1155/2022/9193055.
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This study aims to accurately predict the changing trend of stocks in stock trading so that company investors can obtain higher returns. In building a financial forecasting model, historical data and learned parameters are used to predict future stock prices. Firstly, the relevant theories of stock forecasting are discussed, and problems in stock forecasting are raised. Secondly, the inadequacies of deep neural network (DNN) models are discussed. A prediction trend model of enterprise stock is established based on long short-term memory (LSTM). The uniqueness and innovation lie in using the stock returns of Bank of China securities in 2022 as the training data set. LSTM prediction models are used to perform error analysis on company data training. The 20-day change trend of the company’s stock returns under different models is predicted and analyzed. The results show that as the number of iterations increases, the loss rate of the LSTM training curve keeps decreasing until 0. The average return price of the LSTM prediction model is 14.01. This figure is closest to the average real return price of 13.89. Through the forecast trend analysis under different models, LSTM predicts that the stock change trend of the enterprise model is closest to the changing trend of the actual earnings price. The prediction accuracy is better than other prediction models. In addition, this study explores the characteristics of high noise and complexity of corporate stock time series, designs a DNN prediction model, and verifies the feasibility of the LSTM model to predict corporate stock changes with high accuracy.
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Bruce, S. A., and J. F. Diaz-Valdes. "Generalized Electromagnetic Fields Associated with the Hydrogen-Like Atom Problem." Zeitschrift für Naturforschung A 74, no. 1 (December 19, 2018): 43–50. http://dx.doi.org/10.1515/zna-2018-0372.
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AbstractIt is known that the principle of minimal coupling in quantum mechanics determines a unique interaction form for a charged particle. By properly redefining the canonical commutation relation between (canonical) conjugate components of position and momentum of the particle, e.g. an electron, we restate the Dirac equation for the hydrogen-like atom problem incorporating a generalized minimal electromagnetic coupling. The corresponding interaction keeps the $1/\left|\mathbf{q}\right|$ dependence in both the scalar potential $V\left({\left|\mathbf{q}\right|}\right)$ and the vector potential $\mathbf{A}\left(\mathbf{q}\right)$ ($\left|{\mathbf{A}\left(\mathbf{q}\right)}\right|\sim 1/\left|\mathbf{q}\right|$). This problem turns out to be exactly solvable; moreover, the eigenstates and eigenvalues can be obtained in an elementary fashion. Some feasible models within this approach are discussed. Then we make a few remarks about the breaking of supersymmetry. Finally, we briefly comment on the possible Lie algebra (dynamical symmetry algebra) of these relativistic quantum systems.
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Lup, Aurel-Sorin, Gabriela Ciuprina, Daniel Ioan, Anton Duca, Alexandra Nicoloiu, and Dan Vasilache. "Physics-aware macromodels for MEMS switches." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 39, no. 2 (April 27, 2020): 497–509. http://dx.doi.org/10.1108/compel-06-2019-0267.
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Purpose The purpose of this paper is to propose a physics-aware algorithm to obtain radio frequency (RF)-reduced models of micro-electromechanical systems (MEMS) switches and show how, together with multiphysics macromodels, they can be realized as circuits that include both lumped and distributed parameters. Design/methodology/approach The macromodels are extracted with a robust procedure from the solution of Maxwell’s equations with electromagnetic circuit element (ECE) boundary conditions. The reduced model is extracted from the simulations of three electromagnetic field problems, in full-wave regime, that correspond to three configurations: signal lines alone, switch in the up and down positions. Findings The technique is exemplified for shunt switches, but it can be extended for lateral switches. Moreover, the algorithm is able take frequency dependence into account both for the signal lines and for the switch model. For the later, the order of the model is increased until a specified accuracy is achieved. Originality/value The use of ECE as boundary conditions for the RF simulation of MEMS switches has the advantage that the definition of ports is unambiguous and robust as the ports are clearly defined. The extraction approach has the advantage that the simplified model keeps the basic phenomena, i.e. the propagation of the signal along the lines. As the macromodel is realized with a netlist that uses transmission lines models, the lines’ extension is natural. The frequency dependence can be included in the model, if needed.
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Thind, Navreet S., Justus Hering, and Dirk Söffker. "Fast and Precise Generic Model for Position-Based Trajectory Prediction of Inland Waterway Vessels." Automation 3, no. 4 (November 30, 2022): 633–45. http://dx.doi.org/10.3390/automation3040032.
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Vessel motion simulation as well as model-based accurate trajectory prediction of vessels require accurate models with respect to related dynamic properties. The ability to predict vessel’s trajectory behaviors will become relevant in the case of future autonomous navigation of vessels to predict the behavior of others. The definition of models or parameters can be realized via first principles or by using experimental modeling methods leading to a time invariant or variant model. Existing hydrodynamical modeling approaches are based on mathematical approaches, which use parameters like mass, hydrodynamic forces, wind velocity, depth under the keel, loading parameters, etc. So, determining a dynamic vessel’s model is a complex task, since the model is vessel-specific. For collision avoidance of autonomous or assisted vessels, the trajectory prediction of encountering other vessels is especially required. It is not possible to use complex hydrodynamical models of encountering vessels online due to missing required information/measurements. Even existing deep learning approaches provide better predictions, but are still insufficient for collision avoidance in the case of strong dynamical changes, since the considered input sequences are long. Due to long input sequences, the model does not adapt to strong dynamical changes. In this work, a simple parameter-based approach is developed to predict the intended behavior using the last seconds of the measured position variables. The idea is to globally identify the model parameters of the vessel, which remains constant for the situation, and additionally two parameters for local adaptation, which adapt at every updated input sequence. Typically parameters like rudder angle, wind velocities, and water current affect the behavior of vessels. The introduced approach works with a sliding window approach for which, after identification of the global system, local values are identified based on the last 80 measurements of the vessels. A trajectory prediction (assuming no additional rudder-based maneuvering) is realized for the prediction horizon of 180 s. To confirm the robustness of the new approach, real AIS/GPS-based measurements from a German research inland vessel for different scenarios and sailing conditions including ‘loaded’ and ‘empty’ sailing cases are used. Furthermore, additional results are shown for position data information of different sample rates.
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Erasmus, Michelle Ellis. "An Application of the Z-Transform in Extracting the Density Regulation from the Periodic Output of an Age-Structured Population Model." International Journal of Circuits, Systems and Signal Processing 15 (November 18, 2021): 1676–86. http://dx.doi.org/10.46300/9106.2021.15.181.
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The application of the Z-transform, a manipulation tool from the discrete signal processing (DSP) toolbox, on an ecological model was motivated by the mathematical similarities between an age-structured fish population model with a non linear density regulation and a linear time invariant (LTI) control system. Both models include a switching mechanism in regulating stock/signal throughput in accordance with a given density limitation/set value and both models can be expressed in terms of a negative feedback loop difference equations (Getz & Haight,1989; °Astr¨om & Murray, 2008). In the fish model, the switching mechanism is a density regulated stock-recruitment (SR) function which models the strategies implemented by the population in keeping the vulnerable egg-larvaejuvenile densities within an environmental limitation thereof (Subbey et al, 2014). A switching mechanism is also present in control engineering, for example, in the mechanism associated with cruise control in cars which keeps traveling speed close to a chosen set value midst varying weather and road conditions (Antsaklis and Gao, 2005). In both cases, the choosing of the control action and the tuning of its parameters requires careful consideration to avoid failures such as incorrectly timed switching actions in a control plant (see Kuphaldt (2019)) and errors in estimating total allowable catch (TAC) in the fishing industry (see Borlestean et al (2015), Skagen et al (2013) and Taboadai and R. Anadn (2016)). The Z-transform has proven itself useful in tuning LTI controlmodels for a desired control action (see Orfanidis, (2010) and Smith, (1999)) and it is on this account that its application was extended to the ecological model in pursuit of a more efficient way of estimating SR parameters to simulate an already existing output. It was however found that it could not be used for parameter tuning but rather for the extraction of the SR component hidden in the output together with components resulting from the age structure itself. Such an extraction can greatly assist in the mathematical identification of the SR, reducing the complexity of its choosing as there are many different types used in the fishing industry such as the classic Beverton-Holt model, the Ricker model and Shepherd model (Myers, 2001; Iles, 1994; Shepherd, 1982). It can also be used to monitor changes in the SR over time which can indicate the presence of strategy evolution (Apaloo et al, 2009; Br¨annstr¨om et al, 2013). In 1998 Schoombie and Getz investigated the latter by subjecting the Shepherd SR to strategy optimization with regards to a parameter associated with population interventions in regulating recruitment throughput and it is because of this versatility that the Shepherd SR is chosen for the intended extraction. In true control style, Simulink, a graphic environment for designing control simulations, is used to visualize the production of the output as well as the extraction of the SR from it. This paper showcases the versatility of the Z transform and the possibilities and unexpected finds when applied to similar systems designed to regulate signals or, in this case, recruitment densities.
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Qin, Chao, Yunfeng Zhang, Fangxun Bao, Caiming Zhang, Peide Liu, and Peipei Liu. "XGBoost Optimized by Adaptive Particle Swarm Optimization for Credit Scoring." Mathematical Problems in Engineering 2021 (March 23, 2021): 1–18. http://dx.doi.org/10.1155/2021/6655510.
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Personal credit scoring is a challenging issue. In recent years, research has shown that machine learning has satisfactory performance in credit scoring. Because of the advantages of feature combination and feature selection, decision trees can match credit data which have high dimension and a complex correlation. Decision trees tend to overfitting yet. eXtreme Gradient Boosting is an advanced gradient enhanced tree that overcomes its shortcomings by integrating tree models. The structure of the model is determined by hyperparameters, which is aimed at the time-consuming and laborious problem of manual tuning, and the optimization method is employed for tuning. As particle swarm optimization describes the particle state and its motion law as continuous real numbers, the hyperparameter applicable to eXtreme Gradient Boosting can find its optimal value in the continuous search space. However, classical particle swarm optimization tends to fall into local optima. To solve this problem, this paper proposes an eXtreme Gradient Boosting credit scoring model that is based on adaptive particle swarm optimization. The swarm split, which is based on the clustering idea and two kinds of learning strategies, is employed to guide the particles to improve the diversity of the subswarms, in order to prevent the algorithm from falling into a local optimum. In the experiment, several traditional machine learning algorithms and popular ensemble learning classifiers, as well as four hyperparameter optimization methods (grid search, random search, tree-structured Parzen estimator, and particle swarm optimization), are considered for comparison. Experiments were performed with four credit datasets and seven KEEL benchmark datasets over five popular evaluation measures: accuracy, error rate (type I error and type II error), Brier score, and F 1 score. Results demonstrate that the proposed model outperforms other models on average. Moreover, adaptive particle swarm optimization performs better than the other hyperparameter optimization strategies.
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Sætra, Marte J., Gaute T. Einevoll, and Geir Halnes. "An electrodiffusive neuron-extracellular-glia model for exploring the genesis of slow potentials in the brain." PLOS Computational Biology 17, no. 7 (July 16, 2021): e1008143. http://dx.doi.org/10.1371/journal.pcbi.1008143.
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Within the computational neuroscience community, there has been a focus on simulating the electrical activity of neurons, while other components of brain tissue, such as glia cells and the extracellular space, are often neglected. Standard models of extracellular potentials are based on a combination of multicompartmental models describing neural electrodynamics and volume conductor theory. Such models cannot be used to simulate the slow components of extracellular potentials, which depend on ion concentration dynamics, and the effect that this has on extracellular diffusion potentials and glial buffering currents. We here present the electrodiffusive neuron-extracellular-glia (edNEG) model, which we believe is the first model to combine compartmental neuron modeling with an electrodiffusive framework for intra- and extracellular ion concentration dynamics in a local piece of neuro-glial brain tissue. The edNEG model (i) keeps track of all intraneuronal, intraglial, and extracellular ion concentrations and electrical potentials, (ii) accounts for action potentials and dendritic calcium spikes in neurons, (iii) contains a neuronal and glial homeostatic machinery that gives physiologically realistic ion concentration dynamics, (iv) accounts for electrodiffusive transmembrane, intracellular, and extracellular ionic movements, and (v) accounts for glial and neuronal swelling caused by osmotic transmembrane pressure gradients. The edNEG model accounts for the concentration-dependent effects on ECS potentials that the standard models neglect. Using the edNEG model, we analyze these effects by splitting the extracellular potential into three components: one due to neural sink/source configurations, one due to glial sink/source configurations, and one due to extracellular diffusive currents. Through a series of simulations, we analyze the roles played by the various components and how they interact in generating the total slow potential. We conclude that the three components are of comparable magnitude and that the stimulus conditions determine which of the components that dominate.
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TİFTİK, Merve Nur, Tugba GURGEN ERDOGAN, and Ayça KOLUKISA TARHAN. "A framework for multi-perspective process mining into a BPMN process model." Mathematical Biosciences and Engineering 19, no. 11 (2022): 11800–11820. http://dx.doi.org/10.3934/mbe.2022550.
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<abstract><p>Process mining is mainly focused on process discovery from control perspective. It is further applied to mine the other perspectives such as time, data, and resources by replaying the events in event logs over the initial process model. When process mining is extended far beyond discovering the control-flow models to capture additional perspectives; roles, bottlenecks, amounts of time passed, guards, and routing probabilities in the process can be identified. This is a such extensions are considered under the topic of multi-perspective process mining, which makes the discovered process model more understandable. In this study, a framework for applying multi-perspective process mining and creating a Business Process Modelling Notation (BPMN) process model as the output is introduced. The framework, which uses a recently developed application programming interface (API) for storing the BPMN Data Model which keeps what is produced from each perspective as an asset into a private blockchain in a secure and immutable way, has been developed as a plugin to the ProM tool. In doing so, it integrates a number of techniques for multi-perspective process mining in literature, for the perspectives of control-flow, data, and resource; and represents a holistic process model by combining the outputs of these in the BPMN Data Model. In this article, we explain technical details of the framework and also demonstrate its usage over a case in medical domain.</p></abstract>
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Xu, Lixin, Armin W. Troesch, and William S. Vorus. "Asymmetric Vessel Impact and Planing Hydrodynamics." Journal of Ship Research 42, no. 03 (September 1, 1998): 187–98. http://dx.doi.org/10.5957/jsr.1998.42.3.187.
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The paper proposes a two-dimensional theory for asymmetric impact problems of vessels with arbitrary geometry. The interaction of two body sides is incorporated into the hydrodynamic impact model. Following Vorus's (1996) flat-cylinder theory, two types of flow models are established for cases of small and large asymmetry. The distinguishing difference between the two types is whether the flow is attached or separates at the keel on the first instances of impact. General solutions for such nonlinear boundary value problems are determined by solving the singular integral equations, while free-vortex shedding (jet-spraying) is carried out through a time-marching procedure. Initial conditions are derived from basic solutions of flat-sided contours with constant impact velocity. The method of discrete vortices is then applied to the prediction of slamming loads (including both lifting force and restoring moment) on typical two-dimensional sections of vessels with flat or nearly flat bottoms. Calculated results of both flow types, i.e., small and large asymmetry, are presented for various hull contours with constant or variable impact velocity. This approach also provides the foundation for future work involving traverse dynamic stability analysis of high speed planing hulls
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Alshammari, Salah T., Aiiad Albeshri, and Khalid Alsubhi. "Integrating a High-Reliability Multicriteria Trust Evaluation Model with Task Role-Based Access Control for Cloud Services." Symmetry 13, no. 3 (March 17, 2021): 492. http://dx.doi.org/10.3390/sym13030492.
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Cloud data storage is revolutionary because it eliminates the need for additional hardware, which is often costly, inconvenient, and requires additional space. Cloud data storage allows data owners to store large amounts of data in a flexible way and at low cost. The number of online cloud storage services and their consumers has therefore increased dramatically. However, ensuring the privacy and security of data on a digital platform is often a challenge. A cryptographic task-role-based access control (T-RBAC) approach can be used to protect data privacy. This approach ensures the accessibility of data for authorized consumers and keeps it safe from unauthorized consumers. However, this type of cryptographic approach does not address the issue of trust. In this paper, we propose a comprehensive trust model integrated with a cryptographic T-RBAC to enhance the privacy and security of data stored in cloud storage systems, and suggests that trust models involve inheritance and hierarchy in the roles and tasks of trustworthiness evaluation, where this study aims to identify the most feasible solution for the trust issue in T-RBAC approaches. Risk evaluations regarding other possible flaws of the design are also performed. The proposed design can decrease risk by providing high security for cloud storage systems and improve the quality of decisions of cloud operators and data owners.
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Pang, Yiqun, Yun-Xiang Pang, and Qiurui Wang. "Revealing the Inner-relevance of College Students’ Physical Fitness by Association Analysis and Neural Network." Computational Intelligence and Neuroscience 2022 (September 26, 2022): 1–10. http://dx.doi.org/10.1155/2022/3320942.
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Background: The physical activity and health status of the students in China are not optimistic, there is a general lack of exercise volume and exercise intensity. Normal college students shoulder the future of China’s education. Promoting their physical health is the basic requirement for cultivating teachers in the new era;Methods:Testing and recording 1123 male, 3266 female college students’ physical fitness indicators in a normal college, the relationship between these indicators was mined by correlation analysis and Apriori, and the intelligent prediction models was constructed according to the mined knowledge;Results: There was no correlation between male 1000m running and vital capacity (P > 0.05), but it was correlated with vital capacity weight index (P < 0.05); Most indicators of women showed varying degrees of correlation. There are many association rules between female 50m sprint and standing long jump, sit-ups, and BMI. The introduction of vital capacity weight index slightly improved the accuracy of the 1000m run prediction model; The prediction model of female 50m sprint with standing long jump, sit-ups and BMI as inputs not only keeps the accuracy in a reasonable range, but also reduces the complexity and parameters;ConclusionsFor male students, the ostensibly paradoxical relationships between vital capacity and a 1000 meter run and between vital capacity and pull up were actually due to body shape; Body shape, lower limb explosive power, and core strength play key roles for female college students’ speed quality; BMI, standing long jump and one minute sit-up can be used to predict the 50m sprint performance of general female college students.
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Teotia, Monu, Manu Sharma, Kuldeep Dubey, Amrendra Mohan Shukla, Mayank Vats, and Garima Saini. "An Approach on the Development of a Smart Monitoring System of a Baby Cradle." International Journal for Research in Applied Science and Engineering Technology 11, no. 1 (January 31, 2023): 930–34. http://dx.doi.org/10.22214/ijraset.2023.48716.
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Abstract: Baby care has grown increasingly vital and difficult for working women in recent years. Working mothers will not have enough time at home to regularly check their babies. They delegate responsibility for their baby to a baby sitter or send the baby to their grandparents' home. A smart cradle with an automatic baby monitoring system was designed in the proposed work. The necessary parameters of the infant, such as temperature, heartbeat rate, gas molecules, capture the movements, and position of the baby, were measured and monitored in the baby monitoring system. The infant monitoring system is connected to the cradle, creating an incubator-like environment for the baby. The infant monitoring device keeps an eye on the baby 24 hours a day, seven days a week. The mobile application will display the measured parameters concerning the baby's health, such as temperature, heartbeat rate, and wetness on the baby bed. The baby monitoring system prototype aids parents in time management while also making life easier for caregivers. This infant monitoring device has been shown to do the least amount of harm to the baby while providing the highest level of accuracy. Though several models are already available on the market, the primary goal of this research paper would be to propose an approach for recognizing a particular accent of an individual infant among a group of infants using advanced technologies like as Ai, NLP, or speech recognition.
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Li, Aoxue, Yingxin Wu, Yu Zhang, Ziwei Feng, Feng Pan, and Lianrong Dai. "The Particle-Rotor-Quadrupole-Coupling Model for Transitional Odd-A Nuclei." Symmetry 14, no. 12 (December 6, 2022): 2578. http://dx.doi.org/10.3390/sym14122578.
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The particle-rotor-quadrupole-coupling model, in which the quadrupole–quadrupole interaction of the even-even core is described by a triaxial rotor with a single-j particle, is adopted to describe low-lying spectra of odd-A nuclei within the vibrational to triaxial transition region. In contrast to the particle-plus-rotor-model, the quadrupole–quadrupole interaction introduced in the particle-rotor-quadrupole-coupling model keeps the rotational symmetry in the collective model framework without approximation. To demonstrate the usability, low-lying level energies, reduced E2 transition probabilities, and ground-state quadrupole moments of 135Ba and 131Xe are fit by the model, of which the results are compared with the experimental data and those of other models. It is shown that the fitting results of the particle-rotor-quadrupole-coupling model to the low-lying level energies, reduced E2 transition probabilities, and ground-state electric quadrupole moments of 135Ba and 131Xe are the best, of which the model parameters of the even-even core are determined by the triaxial rotor model in fitting the low-lying spectra of 134Ba and 130Xe. In comparison with the E(5/4) model results of 135Ba, it is also shown that the quadrupole–quadrupole interaction of the even-even core with the single particle adopted can indeed reproduce the E(5/4) critical point behavior. The fitting quality of the reduced E2 transition probabilities among low-lying states by the particle-rotor-quadrupole-coupling model is also noticeably improved. Thus, it can be concluded that the particle-rotor-quadrupole-coupling model is suitable to describe low-lying properties of odd-A nuclei within the transitional region.
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Chen, Bin, Song Cen, Andrew R. Barron, D. R. J. Owen, and Chenfeng Li. "Numerical investigation of the fluid lag during hydraulic fracturing." Engineering Computations 35, no. 5 (July 2, 2018): 2050–77. http://dx.doi.org/10.1108/ec-02-2018-0087.
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Purpose The purpose of this paper is to systematically investigate the fluid lag phenomena and its influence in the hydraulic fracturing process, including all stages of fluid-lag evolution, the transition between different stages and their coupling with dynamic fracture propagation under common conditions. Design/methodology/approach A plane 2D model is developed to simulate the complex evolution of fluid lag during the propagation of a hydraulic fracture driven by an impressible Newtonian fluid. Based on the finite element method, a fully implicit solution scheme is proposed to solve the strongly coupled rock deformation, fluid flow and fracture propagation. Using the proposed model, comprehensive parametric studies are performed to examine the evolution of fluid lag in various geological and operational conditions. Findings The numerical simulations predict that the lag ratio is around 5% or even lower at the beginning stage of hydraulic fracture under practical geological conditions. With the fracture propagation, the lag ratio keeps decreasing and can be ignored in the late stage of hydraulic fracturing for typical parameter combinations. On the numerical aspect, whether the fluid lag can be ignored depends not only on the lag ratio but also on the minimum mesh size used for fluid flow. In addition, an overall mixed-mode fracture propagation factor is proposed to describe the relationship between diverse parameters and fracture curvature. Research limitations/implications In this study, relatively simple physical models such as linear elasticity for solid, Newtonian model for fluid and linear elasticity fracture mechanics for fracture are used. The current model does not account for such effects like leak off, poroelasticity and softening of rock formations, which may also visibly affect the fluid lag depending on specific reservoir conditions. Originality/value This study helps to understand the effect of fluid lag during hydraulic fracturing processes and provides numerical experience in dealing with the fluid lag with finite element simulation.
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Li, Zhiwei, Wenxin Huai, Zhonghua Yang, Zhongdong Qian, and Yuhong Zeng. "Numerical study on the dynamics and mass transfer characteristics of a radial offset jet." Engineering Computations 31, no. 3 (April 28, 2014): 406–24. http://dx.doi.org/10.1108/ec-05-2012-0106.
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Purpose – A radial offset jet has the flow characteristics of a radial jet and an offset jet, which are encountered in many engineering applications. The purpose of this paper is to study the dynamics and mass transfer characteristics of the radial offset jet with an offset ratio 6, 8 and 12. Design/methodology/approach – Three turbulence models, namely the SST k-? model, detached eddy simulation model, and improved delayed detached eddy simulation (IDDES), were applied to the radial offset jet with an offset ratio eight and their results were compared with experimental results. The contrasting results, such as the distributions of mean and turbulent velocity and pressure, show that the IDDES model was the best model in simulating the radial offset jet. The results of the IDDES were analyzed, including the Reynolds stress, turbulent kinetic energy, triple-velocity correlations, vertical structure and the tracer concentration distribution. Findings – In the axisymmetric plane, Reynolds stresses increase to reach a maximum at the location where the jet central line starts to be bent rapidly, and then decrease with increasing distance in the radial direction. The shear layer vortices, which arise from the Kelvin-Helmholtz instability near the jet exit, become larger scale results in the entrainment and vortex pairing, and breakdown when the jet approaches the wall. Near the wall, the vortex swirling direction is different at both front and back of attachment point. In the wall-jet region, the concentration distributions present self-similarity while it keeps constant below the jet in the recirculation region. Research limitations/implications – The radial offset jet with other offset ratio and exit angle is not considered in this paper and should be investigated. Originality/value – The results obtained in this paper will provide guidance for studying similar flow and a better understanding of the radial offset jet.
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Ascher, Kenneth, Kristin DeVleming, and Yuchen Liu. "K-stability and birational models of moduli of quartic K3 surfaces." Inventiones mathematicae, November 27, 2022. http://dx.doi.org/10.1007/s00222-022-01170-5.
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AbstractWe show that the K-moduli spaces of log Fano pairs $$({\mathbb {P}}^3, cS)$$ ( P 3 , c S ) where S is a quartic surface interpolate between the GIT moduli space of quartic surfaces and the Baily–Borel compactification of moduli of quartic K3 surfaces as c varies in the interval (0, 1). We completely describe the wall crossings of these K-moduli spaces. As the main application, we verify Laza–O’Grady’s prediction on the Hassett–Keel–Looijenga program for quartic K3 surfaces. We also obtain the K-moduli compactification of quartic double solids, and classify all Gorenstein canonical Fano degenerations of $${\mathbb {P}}^3$$ P 3 .
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Foshch, T., and S. Pelykh. "IMPROVED MODELS AND METHOD OF POWER CHANGE OF NPP UNIT WITH VVER-1000." Automation of technological and business processes 9, no. 1 (June 12, 2017). http://dx.doi.org/10.15673/atbp.v9i1.505.
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This study represents the improved mathematical and imitational allocated in space multi-zone model of VVER-1000 which differs from the known one. It allows to take into account the energy release of 235U nuclei fission as well as 239Pu . Moreover, this model includes sub-models of simultaneous control impact of the boric acid concentration in the coolant of the first circuit and the position of 9th group control rods which allows to consider it as the model with allocated parameters and also allows to monitor changes in the mentioned technological parameters by reactor core symmetry sectors, by layers of reactor core height and by fuel assembly group each symmetry sector. Moreover, this model allows to calculate important process-dependent parameters of the reactor (including axial offset) as quantitative measure of its safety. As the mathematical and imitational models were improved, it allows to take into account intrinsic properties of the reactor core (including transient processes of xenon) and thus reduce the error of modelling static and dynamic properties of the reactor.The automated control method of power change of the NPP unit with VVER-1000 was proposed for the first time. It uses three control loops. One of which maintains the regulatory change of reactor power by regulating the concentration of boric acid in the coolant, the second circuit keeps the required value of axial offset by changing the position of control rods, and the third one holds constant the coolant temperature mode by regulating the position of the main turbo generator valves.On the basis of the above obtained method, two control programs were improved. The first one is the improved control program that implements the constant temperature of the coolant in the first circuit and the second one is the improved control program that implements the constant steam pressure in the second circuit.
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Tyler, Jonathan, Yining Lu, Jay Dunlap, and Daniel B. Forger. "Evolution of the repression mechanisms in circadian clocks." Genome Biology 23, no. 1 (January 10, 2022). http://dx.doi.org/10.1186/s13059-021-02571-0.
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Abstract Background Circadian (daily) timekeeping is essential to the survival of many organisms. An integral part of all circadian timekeeping systems is negative feedback between an activator and repressor. However, the role of this feedback varies widely between lower and higher organisms. Results Here, we study repression mechanisms in the cyanobacterial and eukaryotic clocks through mathematical modeling and systems analysis. We find a common mathematical model that describes the mechanism by which organisms generate rhythms; however, transcription’s role in this has diverged. In cyanobacteria, protein sequestration and phosphorylation generate and regulate rhythms while transcription regulation keeps proteins in proper stoichiometric balance. Based on recent experimental work, we propose a repressor phospholock mechanism that models the negative feedback through transcription in clocks of higher organisms. Interestingly, this model, when coupled with activator phosphorylation, allows for oscillations over a wide range of protein stoichiometries, thereby reconciling the negative feedback mechanism in Neurospora with that in mammals and cyanobacteria. Conclusions Taken together, these results paint a picture of how circadian timekeeping may have evolved.
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Codogni, Giulio, Luca Tasin, and Filippo Viviani. "ON THE FIRST STEPS OF THE MINIMAL MODEL PROGRAM FOR THE MODULI SPACE OF STABLE POINTED CURVES." Journal of the Institute of Mathematics of Jussieu, April 22, 2021, 1–67. http://dx.doi.org/10.1017/s1474748021000116.
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Abstract The aim of this paper is to study all the natural first steps of the minimal model program for the moduli space of stable pointed curves. We prove that they admit a modular interpretation, and we study their geometric properties. As a particular case, we recover the first few Hassett–Keel log canonical models. As a by-product, we produce many birational morphisms from the moduli space of stable pointed curves to alternative modular projective compactifications of the moduli space of pointed curves.
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Moreira, A. R. P., J. E. G. Silva, and C. A. S. Almeida. "Teleparallel gravity: Effects of torsion in 6D braneworlds." International Journal of Modern Physics D 30, no. 13 (October 1, 2021). http://dx.doi.org/10.1142/s0218271821501030.
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Braneworld models are interesting theoretical and phenomenological frameworks to search for new physics beyond the standard model of particles and cosmology. In this work, we discuss braneworld models whose gravitational dynamics is governed by teleparallel [Formula: see text] gravities. Here, we emphasize a codimension two-axisymmetric model, also known as a string-like brane. Likewise, in the 5D domain-wall models, the [Formula: see text] gravitational modification leads to a phase transition on the perfect fluid source providing a brane-splitting mechanism. Furthermore, the torsion changes the gravitational perturbations. The torsion produces new potential wells inside the brane core leading to a massless mode more localized around the ring structures. In addition, the torsion keeps a gapless nonlocalizable and a stable tower of massive modes in the bulk.
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Shakiba, Saeid, Moosa Ayati, and Aghil Yousefi-Koma. "Development of Hybrid Prandtl–Ishlinskii and Constitutive Models for Hysteresis of Shape-Memory-Alloy-Driven Actuators." Robotica, February 4, 2021, 1–15. http://dx.doi.org/10.1017/s026357472000123x.
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SUMMARY Prandtl–Ishlinskii (PI) model has an excellent compromise to characterize an asymmetric saturated hysteresis behavior of shape-memory-alloy (SMA)-driven systems, but it cannot consider thermomechanical relations between components of SMA-driven systems. On the other hand, constitutive models are composed of these relations, but their precision needs to be improved. In this paper, PI model is proposed to boost constitutive models in two cases. In the first case, PI model is used to characterize martensite volume fraction (MVF) called hybrid model. In the second case, the model is applied as a regulator in the output of a constitutive model called PI-based output (PIO) regulator. Due to simplicity and ability of Liang–Rogers (LR) model in transformation phases, it is considered as an MVF in the original constitutive model. The performance of both proposed models is compared with the original LR-based constitutive model. Unknown parameters of all three models are identified using genetic algorithm in MATLAB Toolbox. The performance of the three models is investigated at three different frequencies of \[\frac{{2\pi }}{8}\] , \[\frac{{2\pi }}{{15}}\] , and \[\frac{{2\pi }}{{30}}\] Hz because the excitation frequency changes the hysteresis behavior. Results show that the proposed hybrid model keeps the precision of the original constitutive model at different frequencies. In addition, the proposed PIO model shows the best performance to predict hysteresis behavior at different frequencies.
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Lee, Kyungyong, Li Li, and Ba Nguyen. "New Combinatorial Formulas for Cluster Monomials of Type $A$ Quivers." Electronic Journal of Combinatorics 24, no. 2 (June 16, 2017). http://dx.doi.org/10.37236/6464.
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Lots of research focuses on the combinatorics behind various bases of cluster algebras. This paper studies the natural basis of a type $A$ cluster algebra, which consists of all cluster monomials. We introduce a new kind of combinatorial formula for the cluster monomials in terms of the so-called globally compatible collections. We give bijective proofs of these formulas by comparing with the well-known combinatorial models of the $T$-paths and of the perfect matchings in a snake diagram. For cluster variables of a type $A$ cluster algebra, we give a bijection that relates our new formula with the theta functions constructed by Gross, Hacking, Keel and Kontsevich.
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ŞAHİN, Ömer Sinan, and Mehmet İTİK. "ACTIVE CONTROL OF VERTICAL ACCELERATION WITH T-FOIL AND TRIM TAB SYSTEMS IN A FAST FERRY." Dokuz Eylül Üniversitesi Denizcilik Fakültesi Dergisi, December 30, 2022. http://dx.doi.org/10.18613/deudfd.1215103.
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This study is concerned with the active T-foil placed near the bow on the keel line of the fast ferry and two active trim tab controls placed at the stern to improve the maritime performance of a fast ferry, whilst improving the comfort and safety of passengers and crew. In the scope of the study, the vertical direction of the fast ferry under the random head waves, heave and pitch motions were taken into account. For the control of T-foil and trim Tabs, PID and LQR control methods were used. The purpose of these controllers is to reduce the acceleration of the heave and pitch motions of the fast ferry by changing the operating angles of the T-foil and trim tab wings. A random wave model was created using the Pierson-Moskowitz model, and simulations were done assuming that the fast ferry was subjected to random head waves. Finally, in order to see the effect of vertical acceleration on passengers, the rate of seasickness (MSI) change of the fast ferry in uncontrolled and controlled states was examined. Mathematical models of fast ferry, T-foil and trim tab and their simulations were carried out in MATLAB / Simulink environment. The simulation results show that T-foil and trim tab Active systems can effectively reduce vertical acceleration by improving heave and pitch motions.
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Haghshenas-Jaryani, Mahdi, and Alan Bowling. "Modeling Flexibility in Myosin V Using a Multiscale Articulated Multi-Rigid Body Approach." Journal of Computational and Nonlinear Dynamics 10, no. 1 (October 13, 2014). http://dx.doi.org/10.1115/1.4026819.
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This paper presents a multiscale dynamic model for the simulation and analysis of flexibility in myosin V. A 3D finite segment model, a multirigid body model connected with torsional springs, is developed to mechanically model the biological structure of myosin V. The long simulation run time is one of the most important issues in the dynamic modeling of biomolecules and proteins due to the disproportionality between the physical parameters involved in their dynamics. In order to address this issue, the most-used models, based on the famous overdamped Langevin equation, omit the inertial terms in the equations of motion; that leads to a first order model that is inconsistent with Newton's second law. However, the proposed model uses the concept of the method of multiple scales (MMS) that brings all of the terms of the equations of motion into proportion with each other; that helps to retain the inertia terms. This keeps the consistency of the model with the physical laws and experimental observations. In addition, the numerical integration's step size can be increased from commonly used subfemtoseconds to submilliseconds. Therefore, the simulation run time is significantly reduced in comparison with other approaches. The simulation results obtained by the proposed multiscale model show a dynamic behavior of myosin V which is more consistent with experimental observations in comparison with other overdamped models.
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"SHAPE OPTIMIZATION OF A TWO WHEELER SUSPENSION WITH DIFFERENT CROSS SECTIONS." INTERNATIONAL JOURNAL FOR ADVANCED RESEARCH IN SCIENCE & TECHNOLOGY, December 4, 2020, 1–5. http://dx.doi.org/10.48047/ijarst/v10/i12/01.
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The two-wheeler chassis consists of the frame, suspension, wheels and brakes. The chassis is what truly sets the overall style of the two-wheeler. Automotive chassis is the main carriage systems of a vehicle. The frame serves as a skeleton upon which parts like gearbox and engine are mounted. It can be made of steel, aluminum or an alloy. It keeps the wheels in line to maintain the handling of the two-wheeler.The frame of a motor vehicle supports all the drive assemblies, i.e. the engine, gearbox and axles (front and rear). In addition the suspension and steering systems and the shock absorbers are attached to it. The appropriate body is fixed to the chassis. It is essential that the frame should not buckle on uneven road surfaces and that any distortions which may occur should not be transmitted to the body. The frame must therefore be torsion−resistant. The frame of a motor vehicle is the load bearing part of the chassis which supports all forces (wheel forces) and weights. It should be as rigid as possible.The main aim of the project is to model a frame of a two wheeler using 3D modeling software Pro/Engineer. Two models of suspension are designed for pipe type and rectangular cross sections.Considering the frame as a beam, calculations are done to determine the displacement and stress by applying loads.To validate the strength of two models, Structural analysis is done by applying the wheel forces. In this analysis ultimate stress limit for the model is determined. Analysis is done for frame using two materials steel and aluminum to verify the best material for frame. Modal analysis is also done to determine natural frequencies of suspension frame. Analysis is done in ANSYS software.Comparison is done mathematically and by FEA analysis. And also we can validate the better cross section and material for suspension frame.
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Gan, Dailin, and Jun Li. "SCIBER: a simple method for removing batch effects from single-cell RNA-sequencing data." Bioinformatics, December 22, 2022. http://dx.doi.org/10.1093/bioinformatics/btac819.
Full textAbstract:
Abstract Motivation Integrative analysis of multiple single-cell RNA-sequencing datasets allows for more comprehensive characterizations of cell types, but systematic technical differences between datasets, known as “batch effects,” need to be removed before integration to avoid misleading interpretation of the data. Although many batch-effect-removal methods have been developed, there is still a large room for improvement: most existing methods only give dimension-reduced data instead of expression data of individual genes, are based on computationally-demanding models, and are black-box models and thus difficult to interpret or tune. Results Here we present a new batch-effect-removal method called SCIBER (Single-Cell Integrator and Batch Effect Remover) and study its performance on real datasets. SCIBER matches cell clusters across batches according to the overlap of their differentially expressed genes. As a simple algorithm that has better scalability to data with a large number of cells and is easy to tune, SCIBER shows comparable and sometimes better accuracy in removing batch effects on real datasets compared to the state-of-the-art methods, which are much more complicated. Moreover, SCIBER outputs expression data in the original space, that is, the expression of individual genes, which can be used directly for downstream analyses. Additionally, SCIBER is a reference-based method, which assigns one of the batches as the reference batch and keeps it untouched during the process, making it especially suitable for integrating user-generated datasets with standard reference data such as the Human Cell Atlas. Availability SCIBER is publicly available as an R package on CRAN: https://cran.r-project.org/web/packages/SCIBER/. A vignette is included in the CRAN R package. Supplementary information Supplementary data are available at Bioinformatics online.
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Zinchenko, Alexander Z., Jacob R. Gissinger, and Robert H. Davis. "Flow of a concentrated emulsion with surfactant through a periodic porous medium." Journal of Fluid Mechanics 953 (December 7, 2022). http://dx.doi.org/10.1017/jfm.2022.951.
Full textAbstract:
High-resolution, long-time three-dimensional simulations are presented for slow, pressure-driven flow of a periodic emulsion of deformable drops through a dense, simple cubic array of solid spheres (one drop and one particle per periodic cell). The drops, covered with insoluble, non-diffusive surfactant, are large compared with pores, and they squeeze with high resistance, very closely coating the solids to overcome surface tension and lubrication effects. The solid volume fraction is 50 %, the emulsion concentration $c_{em}$ in the pore space is 36 % or 50 %, the drop-to-medium viscosity ratio $\lambda$ is 0.25 to 4. The contamination measure $\beta \leq 0.1$ keeps the linear surfactant model (assumed in most of the work) physically relevant. The boundary-integral solution requires extreme resolutions (tens of thousands of boundary elements per surface) achieved by multipole acceleration with special desingularizations, combined with flow-biased surfactant transport algorithms for numerical stability. The time-periodic regime is typically attained after a few squeezing cycles; the motion period is used in the extrapolation scheme to evaluate critical capillary numbers $Ca_{crit}$ demarcating squeezing from trapping. Due to Marangoni stresses, even light ( $\beta =0.05$ ) to moderate ( $\beta =0.1$ ) contaminations significantly reduce the average drop-phase migration velocity (up to 2.8 times, compared with clean drops), especially at small $\lambda =0.25$ . In contrast, $Ca_{crit}$ is weakly sensitive to contamination and levels off completely at $\beta =0.05$ . At $\lambda =0.25$ and $c_{em}=0.36$ , the average drop-phase velocities are much different for lightly and moderately contaminated emulsions, except for near-critical squeezing when they become the same. Nonlinear surfactant models (Langmuir, Frumkin) are used to validate the linear model.