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KOVACEVIC, RAIMUND M., e GEORG CH PFLUG. "ARE TIME CONSISTENT VALUATIONS INFORMATION MONOTONE?" International Journal of Theoretical and Applied Finance 17, n. 01 (febbraio 2014): 1450003. http://dx.doi.org/10.1142/s0219024914500034.
Testo completoAbstract (sommario):
Multi-period risk functionals assign a risk value to discrete-time stochastic processes. While convexity and monotonicity extend in straightforward manner from the single-period case, the role of information is more problematic in the multi-period situation. In this paper, we define multi-period functionals in such a way that the development of available information over time (expressed as a filtration) enters explicitly the definition of the functional. This allows to define and study the property of information monotonicity, i.e. monotonicity w.r.t. increasing filtrations. On the other hand, time consistency of valuations is a favorable property and it is well-known that this requirement essentially leads to compositions of conditional mappings. We demonstrate that generally spoken the intersection of time consistent and information monotone valuation functionals is rather sparse, although both classes alone are quite rich. In particular, the paper gives a necessary and sufficient condition for information monotonicity of additive compositions of positively homogeneous risk/acceptability mappings. Within the class of distortion functionals only compositions of expectation or essential infima are information monotone. Furthermore, we give a sufficient condition and examples for compositions of nonhomogeneous mappings exhibiting information monotonicity.
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Kowalczuk, Zdzislaw, e Piotr Suchomski. "Discrete-Time Generalized Predictive Control with Anticipated Filtration". IFAC Proceedings Volumes 29, n. 1 (giugno 1996): 5238–43. http://dx.doi.org/10.1016/s1474-6670(17)58513-4.
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Borisov, A. V., e G. B. Miller. "Analysis and Filtration of Special Discrete-Time Markov Processes. II. Optimal Filtration". Automation and Remote Control 66, n. 7 (luglio 2005): 1125–36. http://dx.doi.org/10.1007/s10513-005-0153-7.
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Savrassov, Ju S. "Algorithms of filtration and extrapolation for discrete-time dynamical systems". Acta Applicandae Mathematicae 30, n. 3 (marzo 1993): 193–263. http://dx.doi.org/10.1007/bf00995471.
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Martyr, Randall, John Moriarty e Magnus Perninge. "Discrete-time risk-aware optimal switching with non-adapted costs". Advances in Applied Probability 54, n. 2 (giugno 2022): 625–55. http://dx.doi.org/10.1017/apr.2021.44.
Testo completoAbstract (sommario):
AbstractWe solve non-Markovian optimal switching problems in discrete time on an infinite horizon, when the decision-maker is risk-aware and the filtration is general, and establish existence and uniqueness of solutions for the associated reflected backward stochastic difference equations. An example application to hydropower planning is provided.
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Popiński, Waldemar. "Wavelet transform for time-frequency representation and filtration of discrete signals". Applicationes Mathematicae 23, n. 4 (1996): 433–48. http://dx.doi.org/10.4064/am-23-4-433-448.
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Obinabo, E. C., e C. E. Ojieabu. "Measurement Noise Filtration and State Estimation of a Discrete-Time Stochastic Process". International Journal of Soft Computing 5, n. 2 (1 febbraio 2010): 29–34. http://dx.doi.org/10.3923/ijscomp.2010.29.34.
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Borisov, A. V., e G. B. Miller. "Analysis and Filtration of Special Discrete-Time Markov Processes. I. Martingale Representation". Automation and Remote Control 66, n. 6 (giugno 2005): 953–62. http://dx.doi.org/10.1007/s10513-005-0138-6.
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Duda, Zdzislaw. "State estimation in a decentralized discrete time LQG control for a multisensor system". Archives of Control Sciences 27, n. 1 (1 marzo 2017): 29–39. http://dx.doi.org/10.1515/acsc-2017-0002.
Testo completoAbstract (sommario):
Abstract In the paper a state filtration in a decentralized discrete time Linear Quadratic Gaussian problem formulated for a multisensor system is considered. Local optimal control laws depend on global state estimates and are calculated by each node. In a classical centralized information pattern the global state estimators use measurements data from all nodes. In a decentralized system the global state estimates are computed at each node using local state estimates based on local measurements and values of previous controls, from other nodes. In the paper, contrary to this, the controls are not transmitted between nodes. It leads to nonconventional filtration because the controls from other nodes are treated as random variables for each node. The cost for the additional reduced transmission is an increased filter computation at each node.
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CHEN, YANHONG, e YIJUN HU. "SET-VALUED DYNAMIC RISK MEASURES FOR BOUNDED DISCRETE-TIME PROCESSES". International Journal of Theoretical and Applied Finance 23, n. 03 (maggio 2020): 2050017. http://dx.doi.org/10.1142/s021902492050017x.
Testo completoAbstract (sommario):
In this paper, we study how to evaluate the risk of a financial portfolio, whose components may be dependent and come from different markets or involve more than one kind of currencies, while we also take into consideration the uncertainty about the time value of money. Namely, we introduce a new class of risk measures, named set-valued dynamic risk measures for bounded discrete-time processes that are adapted to a given filtration. The time horizon can be finite or infinite. We investigate the representation results for them by making full use of Legendre–Fenchel conjugation theory for set-valued functions. Finally, some examples such as the set-valued dynamic average value at risk and the entropic risk measure for bounded discrete-time processes are also given.
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Tanaka, Teruo. "The accessibility and multiple filtration structure for discrete time multiparameter optimal multiple stopping problems". Journal of Statistics and Management Systems 7, n. 2 (gennaio 2004): 221–35. http://dx.doi.org/10.1080/09720510.2004.10701117.
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Alarcón-Carbajal, Martin A., José E. Carvajal-Rubio, Juan D. Sánchez-Torres, David E. Castro-Palazuelos e Guillermo J. Rubio-Astorga. "An Output Feedback Discrete-Time Controller for the DC-DC Buck Converter". Energies 15, n. 14 (21 luglio 2022): 5288. http://dx.doi.org/10.3390/en15145288.
Testo completoAbstract (sommario):
This paper presents a discrete-time output feedback controller to regulate the output voltage of a DC-DC buck converter. The proposal’s main feature is the application of a discrete-time equivalent of the robust exact filtering differentiator. First, the document exposes a theoretical analysis of the closed-loop system, where it is considered the problem of implementing a real-time differentiator with a good relationship between exactness and noise filtration performance. Hence, secondly, the controller in a laboratory setup is presented. The first experimental results suggest that the proposed controller exhibits good robustness against noise and maintains the asymptotic accuracy, even with saturated control inputs, as in the case of the DC-DC buck converter. Consequently, aiming to verify the features of the proposed method, the controller is validated through multiple experiments, showing satisfactory voltage tracking accuracy, good suppression of instantaneous load and supply voltage disturbances, and robustness against bounded measurement noise.
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AGHILI, S. ALIREZA, DIVYAKANT AGRAWAL e AMR EL ABBADI. "SEQUENCE SIMILARITY SEARCH USING DISCRETE FOURIER AND WAVELET TRANSFORMATION TECHNIQUES". International Journal on Artificial Intelligence Tools 14, n. 05 (ottobre 2005): 733–54. http://dx.doi.org/10.1142/s0218213005002363.
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In this paper, we study the problem of sequence similarity search. We incorporate vector transformations and apply DFT (Discrete Fourier Transformation) and DWT (Discrete Wavelet Transformation, Haar) dimensionality reduction techniques to reduce the search space/time of sequence similarity range queries. Our empirical results on a number of Prokaryote and Eukaryote DNA contig databases demonstrate up to 50-fold filtration ratio reduction of the search space and up to 13 times faster filtration. The proposed transformation techniques may easily be integrated as a pre-processing phase on top of current similarity search heuristics/techniques such as BLAST, PatternHunter, FastA and QUASAR to efficiently prune non-relevant sequences. We study the precision of applying dimensionality reduction techniques for faster and more efficient range query searches and discuss the imposed trade-offs.
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Elbanna, Ahmed Mohammed, Xiaobei Cheng, Can Yang, Medhat Elkelawy e Hager Alam Elden. "Knock Recognition System in a PCCI Engine Powered by Diesel". Highlights in Science, Engineering and Technology 15 (26 novembre 2022): 94–101. http://dx.doi.org/10.54097/hset.v15i.2209.
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The measurement of engine vibrations components is used to identify combustion phases in a single-cylinder PCCI diesel engine in this work. A single channel Knock transducer was used to measure engine vibration caused by combustion pressure forces and knocking tendency. The transducer is used to obtain the engine's frequency spectrum in the temporal domain. Categorization discrete wavelet analysis is used to isolate the observed vibration data. Spectral analysis and filtration of fragmented sections of the source signal are used in this approach. Fast Fourier transforms (FFT) and short-time Fourier transform (STFT) are used to investigating the discrete parts of the observed signals (STFT). In order to study engine events, time is given in milliseconds in the time-frequency domain. The engine knocking is determined from the observed signal using time-frequency analysis. The outcomes reveal that the engine events derived from vibration signals are closely connected to the premixing fuel ratio, as expected.
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Красноруцький, А. О., О. В. Федоровський e В. Ж. Ященок. "Method of description for the dynamics of the signal delay change in discrete time with changing aircraft position in space". Системи обробки інформації, n. 3(166) (24 settembre 2021): 41–45. http://dx.doi.org/10.30748/soi.2021.166.04.
Testo completoAbstract (sommario):
The article presents an innovative approach to the description of the aircraft range parameter in discrete time when simulating the process of its repositioning in space. A method of describing the dynamics of changes in signal delay in discrete time when the aircraft is changing its spatial position is proposed. Such a model adequately describes the change in signal delay in discrete time. The direction of estimation for the adequacy of radio signal delay change simulation in algorithms of optimum filtration is defined in accordance with the aerodynamic properties of the aircraft. Simulation of the signal delay dynamic change is carried out (it is completely described by the dynamics of change in the distance to the aircraft). The transformation stages of simulation data for the initial model in continuous time with realization of the standard Gaussian random numbers are justified. Information on the simulation data transformation taking into account the correlation matrix of discrete white noise is provided. A method of calculating the transition matrix through the Laplace transform is proposed. The scientific-applied direction of research is determined – it lies in the development of a method for the legitimate representation for the mathematical model of aircraft’s changing range in discrete time within one-dimensional space: the longitudinal and the transverse dimensions. This approach takes into account the continuous description for a system of stochastic differential equations. A comprehensive algorithm for modeling the values of discrete white noise on modern computer equipment and calculating the dynamics of the aircraft range parameter changes is proposed. This algorithm allows to correctly form the a priori information about the change of the vector parameters of the aircraft spatial position at discrete moments of time. As a result, it was shown that the use of the obtained information in the optimal filtering algorithms minimizes the error when determining distance to the aircraft and, accordingly, allows to increase the accuracy and adequacy of the signal delay simulation in discrete time. The results of this research can be used in modernization of the existing models and development of promising on-board radar stations, integrated rangefinders, systems of radio technical reconnaissance and electronic warfare systems, as well as in technical implementation of aircraft flight simulation systems.
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Leão, Dorival, Alberto Ohashi e Francesco Russo. "Discrete-type approximations for non-Markovian optimal stopping problems: Part I". Journal of Applied Probability 56, n. 4 (dicembre 2019): 981–1005. http://dx.doi.org/10.1017/jpr.2019.57.
Testo completoAbstract (sommario):
AbstractWe present a discrete-type approximation scheme to solve continuous-time optimal stopping problems based on fully non-Markovian continuous processes adapted to the Brownian motion filtration. The approximations satisfy suitable variational inequalities which allow us to construct $\varepsilon$ -optimal stopping times and optimal values in full generality. Explicit rates of convergence are presented for optimal values based on reward functionals of path-dependent stochastic differential equations driven by fractional Brownian motion. In particular, the methodology allows us to design concrete Monte Carlo schemes for non-Markovian optimal stopping time problems as demonstrated in the companion paper by Bezerra et al.
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Glazyrin, Yury E., Gleb G. Mironov, Anna S. Kichkailo e Maxim V. Berezovski. "Separation Abilities of Capillary Electrophoresis Coupled with Ion Mobility Mass Spectrometry for the Discrete Detection of Sequence Isomeric Peptides". Separations 9, n. 5 (25 aprile 2022): 106. http://dx.doi.org/10.3390/separations9050106.
Testo completoAbstract (sommario):
The separation and discrete detection of isomeric sequence peptides with similar properties are important tasks for analytical science. Three different peptide isomers of 12 amino-acid residues long, containing direct and reverse regions of the alanine-valine-proline-isoleucine (AVPI) motif, were partially separated and discretely detected from their mixture using two approaches. Capillary electrophoresis enabled the separation and optical detection of the peptide sequence isomers close to the baseline. The ability to separate these sequence isomers from the mixture and discretely identify them from mass spectra has also been demonstrated by ion-mobility tandem mass spectrometry. Moreover, for the first time, capillary electrophoresis and ion-mobility mass spectrometry connected online have shown their ability for a discrete detection of the multidirectional sequence isomers.
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Glazyrin, Yury E., Gleb G. Mironov, Anna S. Kichkailo e Maxim V. Berezovski. "Separation Abilities of Capillary Electrophoresis Coupled with Ion Mobility Mass Spectrometry for the Discrete Detection of Sequence Isomeric Peptides". Separations 9, n. 5 (25 aprile 2022): 106. http://dx.doi.org/10.3390/separations9050106.
Testo completoAbstract (sommario):
The separation and discrete detection of isomeric sequence peptides with similar properties are important tasks for analytical science. Three different peptide isomers of 12 amino-acid residues long, containing direct and reverse regions of the alanine-valine-proline-isoleucine (AVPI) motif, were partially separated and discretely detected from their mixture using two approaches. Capillary electrophoresis enabled the separation and optical detection of the peptide sequence isomers close to the baseline. The ability to separate these sequence isomers from the mixture and discretely identify them from mass spectra has also been demonstrated by ion-mobility tandem mass spectrometry. Moreover, for the first time, capillary electrophoresis and ion-mobility mass spectrometry connected online have shown their ability for a discrete detection of the multidirectional sequence isomers.
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Go, Hyeon Woo, Soo-Young Moon, Hyeon Soo Kim, So Ye Jang, Eun Byeol Kang e Jin Chul Joo. "Evaluation of the Feasibility of Foam Glass as Filter Media in Rain Garden". Journal of Korean Society of Environmental Engineers 44, n. 12 (31 dicembre 2022): 603–15. http://dx.doi.org/10.4491/ksee.2022.44.12.603.
Testo completoAbstract (sommario):
Objectives:In order to recycle and resource waste glass, the feasibility of foam glass as filter media was evaluated, and column experiments using foam glass media were conducted to confirm the applicability as filter media in rain garden. Through this experiment, various design factors to be considered can be derived in application of foam glass media in the rain garden.Methods:Sieve analysis and SEM/EDS analysis were conducted to confirm the physicochemical properties of the foam glass. Column experiments filled with only foam glass and mixtures of sand and foam glass were conducted to simulate rain garden to evaluate the removal efficiency of suspended solids and turbidity using the foam glass media, head difference (<i>Δh</i>) and hydraulic conductivity (<i>K</i>) changes, and calculation of filtered suspended solids loading using both discrete and cumulative mass approach. Finally, comparison of filtration performance with various filter media used in LID facilities was performed to evaluate the feasibility of foam glass media in rain garden.Results and Discussion:Since foam glass media has a lower density than water, homogeneous particle size, and smooth surface with pores of various sizes, foam glass media effectively induces internal capture and external adsorption of suspended solids. Foam glass media has been applied to high suspended solids and turbidity removal efficiency. As the suspended solids inflow load increased, clogging occurred in the pores and the removal efficiency gradually decreased, but the foam glass media with lower density than water was continuously disturbed and rearranged due to the head difference energy, and some clogging were alleviated by rearrangement of pores and channels. The load of suspended solids in precipitated, adsorbed, and retained on the foam glass was calculated using the effluent sample (discrete) collected at regular time intervals and the continuously accumulated sample (cumulative) from the output. The filtered suspended solids load calculated using the cumulative mass approach was higher due to the estimation of the amounts of suspended solids remaining in the filtration column is lower because the samples (discrete) collected at regular time intervals from the output do not reflect the amount of suspended solids that change over time. Thus, the amounts of suspended solids removed through the filtration process can be much more accurately estimated using the cumulative samples. Finally, when comparing the removal efficiency with other filter media, foam glass can be used as excellent filter media with higher removal efficiency and greater lifespan.Conclusion:Foam glass media with smooth surface, pores of various sizes, and lower density than water can rearrange and regenerate pores to alleviate some clogging, resulting in high suspended solids and turbidity removal efficiency for a long period of time. Considering that the amount of suspended solids filtered is determined by various factors such as particle size and distribution, porosity, depth, linear velocity, and inflow load of the suspended solids, the feasibility test using foam glass media through long-term field experiments is warranted. The amounts of suspended solids removed through the filtration process can be much more accurately estimated using the cumulative samples.
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Popiński, Waldemar. "Statistical View on Phase and Magnitude Information in Signal Processing". Artificial Satellites 47, n. 3 (1 gennaio 2012): 127–36. http://dx.doi.org/10.2478/v10018-012-0018-6.
Testo completoAbstract (sommario):
Statistical View on Phase and Magnitude Information in Signal ProcessingIn this work the problem of reconstruction of an original complex-valued signalot,t= 0, 1, …,n- 1, from its Discrete Fourier Transform (DFT) spectrum corrupted by random fluctuations of magnitude and/or phase is investigated. It is assumed that the magnitude and/or phase of discrete spectrum values are distorted by realizations of uncorrelated random variables. The obtained results of analysis of signal reconstruction from such distorted DFT spectra concern derivation of the expected values and bounds on variances of the reconstructed signal at the observation moments. It is shown that the considered random distortions in general entail change in magnitude and/or phase of the reconstructed signal expected values, which together with imposed random deviations with finite variances can blur the similarity to the original signal. The effect of analogous random amplitude and/or phase distortions of a complex valued time domain signal on band pass filtration of distorted signal is also investigated.
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Thavaneswaran, A., e M. E. Thompson. "Optimal estimation for semimartingales". Journal of Applied Probability 23, n. 02 (giugno 1986): 409–17. http://dx.doi.org/10.1017/s0021900200029703.
Testo completoAbstract (sommario):
This paper extends a result of Godambe's theory of parametric estimation for discrete-time stochastic processes to the continuous-time case. LetP={P} be a family of probability measures such that (Ω,F, P) is complete, (Ft, t≧0) is a standard filtration, andX = (XtFt, t ≧ 0)is a semimartingale for everyP ∈ P. For a parameterθ(Ρ), supposeXt=Vt,θ+Ht,θwhere theVθprocess is predictable and locally of bounded variation and theHθprocess is a local martingale. Consider estimating equations forθof the formprocess is predictable. Under regularity conditions, an optimal form forαθin the sense of Godambe (1960) is determined. WhenVt,θis linear inθthe optimal, corresponds to certain maximum likelihood or least squares estimates derived previously in special cases. Asymptotic properties of, are discussed.
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JEANBLANC, MONIQUE, e STOYAN VALCHEV. "PARTIAL INFORMATION AND HAZARD PROCESS". International Journal of Theoretical and Applied Finance 08, n. 06 (settembre 2005): 807–38. http://dx.doi.org/10.1142/s0219024905003232.
Testo completoAbstract (sommario):
This paper studies in some examples the role of information in a default-risk framework. We examine three types of information for a firm's unlevered asset value to the secondary bond market: the classical case of continuous and perfect information, observation of past and contemporaneous asset values at selected discrete times, and observation of contemporaneous asset value at discrete times. The third information filtration is contained in the second, which in turn, is contained in the first. We investigate the changes of the distributional properties of the default time and the properties of bond prices and credit spreads with the reductions of the information sets. Consistently with the observed market prices, model bond prices with partial information have surprise jumps prior to default. Credit spreads for very short times to maturities are increasing with the reductions of the information sets. High-yield bonds with the two types of incomplete information have downward sloping term structures of credit spreads. For firms with good credit qualities, increases of the observation lags lead to upward shifts in the term structures of credit spreads. The two information constrained models admit reduced form representations, in which the time of default is a totally inaccessible time with default arrival intensities, but it is better avoiding the intensity approach to valuation since the hazard process approach is more efficient.
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Thavaneswaran, A., e M. E. Thompson. "Optimal estimation for semimartingales". Journal of Applied Probability 23, n. 2 (giugno 1986): 409–17. http://dx.doi.org/10.2307/3214183.
Testo completoAbstract (sommario):
This paper extends a result of Godambe's theory of parametric estimation for discrete-time stochastic processes to the continuous-time case. Let P ={P} be a family of probability measures such that (Ω, F, P) is complete, (Ft, t≧0) is a standard filtration, and X = (Xt Ft, t ≧ 0) is a semimartingale for every P ∈ P. For a parameter θ (Ρ), suppose Xt = Vt,θ + Ht,θ where the Vθ process is predictable and locally of bounded variation and the Hθ process is a local martingale. Consider estimating equations for θ of the form process is predictable. Under regularity conditions, an optimal form for α θ in the sense of Godambe (1960) is determined. When Vt,θ is linear in θ the optimal , corresponds to certain maximum likelihood or least squares estimates derived previously in special cases. Asymptotic properties of , are discussed.
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Baigereyev, Dossan, Dinara Omariyeva, Nurlan Temirbekov, Yerlan Yergaliyev e Kulzhamila Boranbek. "Numerical Method for a Filtration Model Involving a Nonlinear Partial Integro-Differential Equation". Mathematics 10, n. 8 (15 aprile 2022): 1319. http://dx.doi.org/10.3390/math10081319.
Testo completoAbstract (sommario):
In this paper, we propose an efficient numerical method for solving an initial boundary value problem for a coupled system of equations consisting of a nonlinear parabolic partial integro-differential equation and an elliptic equation with a nonlinear term. This problem has an important applied significance in petroleum engineering and finds application in modeling two-phase nonequilibrium fluid flows in a porous medium with a generalized nonequilibrium law. The construction of the numerical method is based on employing the finite element method in the spatial direction and the finite difference approximation to the time derivative. Newton’s method and the second-order approximation formula are applied for the treatment of nonlinear terms. The stability and convergence of the discrete scheme as well as the convergence of the iterative process is rigorously proven. Numerical tests are conducted to confirm the theoretical analysis. The constructed method is applied to study the two-phase nonequilibrium flow of an incompressible fluid in a porous medium. In addition, we present two examples of models allowing for prediction of the behavior of a fluid flow in a porous medium that are reduced to solving the nonlinear integro-differential equations studied in the paper.
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Чубич, Владимир Михайлович, e Светлана Олеговна Кулабухова. "Square-root algorithms for robust modifications of the continuous-discrete cubature Kalman filter". Вычислительные технологии, n. 3 (15 luglio 2020): 88–98. http://dx.doi.org/10.25743/ict.2020.25.3.010.
Testo completoAbstract (sommario):
Предложены две устойчивые к ошибкам машинного округления и к аномальным данным квадратно-корневые модификации непрерывно-дискретного кубатурного фильтра Калмана, основанные на вариационном байесовском и коррентропийном подходах. Апробация разработанных алгоритмов на модельной задаче со случайным характером расположения аномальных наблюдений показала их работоспособность при сопоставимом качестве фильтрации. Подтверждена алгебраическая эквивалентность представленных квадратно-корневых и стандартных версий Rounding errors due to the finite length of machine word can significantly affect the quality of estimation and filtering when solving the corresponding problems in various subject areas. In this regard, to improve the reliability of the obtained results, it is advisable to develop and then apply square-root modifications of the used algorithms. Purpose: developing the square-root modifications of the continuous-discrete cubature Kalman filter on the basis of variational Bayesian and correntropy approaches. Methodology: matrix orthogonal QR decomposition. Findings: two robust (resistant to the possible presence of anomalous data and to machine rounding errors) modifications of the continuous-discrete cubature Kalman filter have been developed. The first (variational Bayesian) algorithm is obtained by extending the known discrete equations of the extrapolation stage to the continuous-discrete case. The second algorithm, based on the maximum correntropy criterion, is proposed in this paper for the first time. The developed square-root algorithms for nonlinear filtering are validated on the example of one stochastic dynamical system model with the random location of anomalous observations. In doing so, the filtering quality, estimated by the value of the accumulated mean square error, was quite comparable for both modifications during equivalent results obtained for the corresponding root-free analogues. Value: the proposed square-root versions of robust modifications of the continuous-discrete cubature Kalman filter are algebraically equivalent to their standard analogues. Meanwhile, positive definiteness and symmetry of covariance matrices of the state vector estimates at the extrapolation and the filtration stages are provided. The developed algorithms will be used to develop software and mathematical support for parametric identification of stochastic nonlinear continuous-discrete systems in the presence of anomalous observations in the measurement data
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Čiegis, R., M. Meilūnas e A. Štikonas. "MATHEMATICAL MODELLING OF WATER FLOW IN PAPER PRESS MACHINES". Mathematical Modelling and Analysis 9, n. 4 (31 dicembre 2004): 267–86. http://dx.doi.org/10.3846/13926292.2004.9637259.
Testo completoAbstract (sommario):
In this work, mathematical models of wet pressing of paper are studied. Our goal is to compare two mathematical models, which are developed for simulation of filtration processes in paper press machines. Both models were obtained from the same general model of the compressible porous medium, but different assumptions were used. Modified models are developed that describe water losses at the boundaries of the porous layer and the importance of this factor is investigated. Numerical algorithms are developed for simulation of the liquid movement in the deformable porous media. It is proved that the discrete problem is stable if the time step t satisfies the inequality τ ≤ Ch2 . It follows from the stability analysis that the mathematical model describes an ill-posed problem for some values of parameters used in simulations.
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Hoekzema, Renee S., Lewis Marsh, Otto Sumray, Thomas M. Carroll, Xin Lu, Helen M. Byrne e Heather A. Harrington. "Multiscale Methods for Signal Selection in Single-Cell Data". Entropy 24, n. 8 (13 agosto 2022): 1116. http://dx.doi.org/10.3390/e24081116.
Testo completoAbstract (sommario):
Analysis of single-cell transcriptomics often relies on clustering cells and then performing differential gene expression (DGE) to identify genes that vary between these clusters. These discrete analyses successfully determine cell types and markers; however, continuous variation within and between cell types may not be detected. We propose three topologically motivated mathematical methods for unsupervised feature selection that consider discrete and continuous transcriptional patterns on an equal footing across multiple scales simultaneously. Eigenscores (eigi) rank signals or genes based on their correspondence to low-frequency intrinsic patterning in the data using the spectral decomposition of the Laplacian graph. The multiscale Laplacian score (MLS) is an unsupervised method for locating relevant scales in data and selecting the genes that are coherently expressed at these respective scales. The persistent Rayleigh quotient (PRQ) takes data equipped with a filtration, allowing the separation of genes with different roles in a bifurcation process (e.g., pseudo-time). We demonstrate the utility of these techniques by applying them to published single-cell transcriptomics data sets. The methods validate previously identified genes and detect additional biologically meaningful genes with coherent expression patterns. By studying the interaction between gene signals and the geometry of the underlying space, the three methods give multidimensional rankings of the genes and visualisation of relationships between them.
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Morkun, Natalia, Tetiana Oliinyk, Iryna Kasatkina e Oleksandr Rytsko. "Adaptive control of ore mill charge". E3S Web of Conferences 123 (2019): 01038. http://dx.doi.org/10.1051/e3sconf/201912301038.
Testo completoAbstract (sommario):
The system of mining operations does not enable long-lasting mining of single-type ores that causes instability of mineral materials intended for concentration. To solve the problem of controlling these processes on the basis of operating data on characteristics of processed raw materials, the method of controlling mill charge is suggested considering measurements of its output product. This method is based on correlation of the output product quantity and the rate of the mill charge. The process of the object’s operation is modeled, while time characteristics of the output controlled value and the mill charge are approximated to assess accuracy of the method of determining the mill charge. The possibility to use the discrete Kalman filter is studied in order to indentify the object’s characteristics under noises by measurement results. It is shown that application of the Kalman filter to controlling the mill charge enables not only solving the problem of filtration aimed to obtain data on the object’s current state, but also predicting its state.
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PAGÈS, GILLES, HUYÊN PHAM e JACQUES PRINTEMS. "AN OPTIMAL MARKOVIAN QUANTIZATION ALGORITHM FOR MULTI-DIMENSIONAL STOCHASTIC CONTROL PROBLEMS". Stochastics and Dynamics 04, n. 04 (dicembre 2004): 501–45. http://dx.doi.org/10.1142/s0219493704001231.
Testo completoAbstract (sommario):
We propose a probabilistic numerical method based on optimal quantization to solve some multi-dimensional stochastic control problems that arise, for example, in mathematical finance for portfolio optimization. We then consider some controlled diffusions with most components control free. The Euler scheme of the uncontrolled diffusion part is approximated by a discrete time process obtained by a nearest neighbor projection on some grids optimally fitted to its dynamics. The resulting process is also designed to preserve the Markov property with respect to the filtration of the Euler scheme. This Markovian quantization approach leads to an approximate control problem that can be solved numerically by the dynamic programming formula. This approach seems promising in higher dimension. A prioriLp-error bounds are stated and we show that the spatial discretization error term is minimal at some specific grids. A simple recursive algorithm is devised to compute these optimal grids by induction based on a Monte Carlo simulation. Some numerical illustrations are processed for solving a mean-variance hedging problem.
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Shaffee, Siti Nur, Paul F. Luckham, Omar K. Matar, Aditya Karnik e Mohd Shahrul Zamberi. "Numerical Investigation of Sand-Screen Performance in the Presence of Adhesive Effects for Enhanced Sand Control". SPE Journal 24, n. 05 (3 giugno 2019): 2195–208. http://dx.doi.org/10.2118/195686-pa.
Testo completoAbstract (sommario):
Summary In many industrial processes, an effective particle–filtration system is essential for removing unwanted solids. The oil and gas industry has explored various technologies to control and manage excessive sand production, such as by installing sand screens or injecting consolidation chemicals in sand–prone wells as part of sand–management practices. However, for an unconsolidated sandstone formation, the selection and design of effective sand control remains a challenge. In recent years, the use of a computational technique known as the discrete–element method (DEM) has been explored to gain insight into the various parameters affecting sand–screen–retention behavior and the optimization of various types of sand screens (Mondal et al. 2011, 2012, 2016; Feng et al. 2012; Wu et al. 2016). In this paper, we investigate the effectiveness of particle filtration using a fully coupled computational–fluid–dynamics (CFD)/DEM approach featuring polydispersed, adhesive solid particles. We found that an increase in particle adhesion reduces the amount of solid in the liquid filtrate that passes through the opening of a wire–wrapped screen, and that a solid pack of particle agglomerates is formed over the screen with time. We also determined that increasing particle adhesion gives rise to a decrease in packing density and a diminished pressure drop across the solid pack covering the screen. This finding is further supported by a Voronoi tessellation analysis, which reveals an increase in porosity of the solid pack with elevated particle adhesion. The results of this study demonstrate that increasing the level of particle agglomeration, such as by using an adhesion–promoting chemical additive, has beneficial effects on particle filtration. An important application of these findings is the design and optimization of sand–control processes for a hydrocarbon well with excessive sand production, which is a major challenge in the oil and gas industry.
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Tkacheshak, N. V., e М. І. Horbiichuk. "INVESTIGATION OF EXHAUSTING PHENOMENA OF GAS TURBINE ENGINE ON THE BASIS OF WAVELET ANALYSIS". Scientific Bulletin of Ivano-Frankivsk National Technical University of Oil and Gas, n. 2(45) (27 novembre 2018): 24–33. http://dx.doi.org/10.31471/1993-9965-2018-2(45)-24-33.
Testo completoAbstract (sommario):
The method for research of a gas turbine engine (GTE) surging phenomena based on wavelet analysis was developed. GTE DG-90 was chosen for research. A wavelet decomposition of the air pressure signal was carried out using a high pressure compressor and Dobeski, Symlet, Coffle and Meyer's discrete wavelet. The advantages and disadvantages of filtering properties of these wavelets were graphically represented in the form of amplitude-frequency characteristics. Based on the results obtained, a wavelet transform parameter selection scheme based on the analysis of the frequency response of wavelet filters was constructed, and the optimum sampling time of the wavelet filtering of the investigated signal was calculated for determination of the propagation and rotational breakdown in the GTE turbocompressor. According to this scheme, among the wavelets of Dobeski, Simlet, Koefleta, and Meyer's discrete wavelet, for studying the air pressure signal at the compressor during bursting processes, the first were selected by the Dobeches and Symmetes wavelets of the 2nd order according to their filtration rate. Considering high speed and characteristics of the description of the occurrence of excite phenomena by means of a fast Fourier transform to the distribution of the wavelet coefficients of the air pressure signal by turbocompressor, for the diagnosis of unstable flows occurring in the gas path of the gas turbine trajectory (surging and rotary breakdown), the Dobeski wavelet was selected 2nd order. At the same time, to monitor the wavelet coefficients behavior, the detail of the investigated signal is necessary at the 7th level of decomposition. Thus, the obtained results allow to carry out further analysis of breakdown processes using low-order wavelets.
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Marchenko, Olga, e Tetiana Samoilenko. "Constructing the Approximate Solution of Axisymmetric Problem on the Dynamics of Anisothermal Moisture Transfer". Cybernetics and Computer Technologies, n. 1 (31 marzo 2020): 41–52. http://dx.doi.org/10.34229/2707-451x.20.1.5.
Testo completoAbstract (sommario):
Introduction. Calculation of dynamics of the anisothermal moisture transfer processes in axisymmetric formulation is essential in the study of wet soils condition around, for example, vertical drains, wells, piles, etc. In this paper, we formulate the initial boundary value problem for the system of moisture and heat transfer nonstationary equations. The problem is considered for isotropic medium in cylindrical coordinate system under the inhomogeneous mixed boundary conditions. The obtained results are important for future research in cylindrical coordinates of problems that model the migration of moisture during the seasonal freezing of the soil, taking into account phase transitions from unfrozen water to ice in the entire volume of the soil mass without highlighting the crystallization front. In this case moisture exchange and heat transfer characteristics appear as functions of the total humidity. Consequently, the equation of moisture transfer is written relative to the "fictitious" moisture content. Because of the main direction of moisture migration relative to the freezing/melting front, the convective heat transfer along the vertical coordinate axis is considered to be essential that leads to sufficient coincidence with the experimental data. The purpose of the paper is to formulate the appropriate generalized problem in the Galorkin form for the axisymmetric initial-boundary value problem. The important goal is to investigate the accuracy of the continuous in time and completely discrete approximate generalized solutions based on the finite elements method. Results. The algorithm for constructing of approximate generalized solution of the axisymmetric initial-boundary value problem for the system of filtration and heat transfer equations is proposed. The estimates of the convergence rate for the continuous in time and discrete approximate solutions based on the finite elements method are obtained.
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Wu, Songwei, Ming-Yuan Jian, Yan-Chun Xu, Chun Zhou, Abu-Bakr Al-Mehdi, Wolfgang Liedtke, Hee-Sup Shin e Mary I. Townsley. "Ca2+ entry via α1G and TRPV4 channels differentially regulates surface expression of P-selectin and barrier integrity in pulmonary capillary endothelium". American Journal of Physiology-Lung Cellular and Molecular Physiology 297, n. 4 (ottobre 2009): L650—L657. http://dx.doi.org/10.1152/ajplung.00015.2009.
Testo completoAbstract (sommario):
Pulmonary vascular endothelial cells express a variety of ion channels that mediate Ca2+ influx in response to diverse environmental stimuli. However, it is not clear whether Ca2+ influx from discrete ion channels is functionally coupled to specific outcomes. Thus we conducted a systematic study in mouse lung to address whether the α1G T-type Ca2+ channel and the transient receptor potential channel TRPV4 have discrete functional roles in pulmonary capillary endothelium. We used real-time fluorescence imaging for endothelial cytosolic Ca2+, immunohistochemistry to probe for surface expression of P-selectin, and the filtration coefficient to specifically measure lung endothelial permeability. We demonstrate that membrane depolarization via exposure of pulmonary vascular endothelium to a high-K+ perfusate induces Ca2+ entry into alveolar septal endothelial cells and exclusively leads to the surface expression of P-selectin. In contrast, Ca2+ entry in septal endothelium evoked by the selective TRPV4 activator 4α-phorbol-12,13-didecanoate (4α-PDD) specifically increases lung endothelial permeability without effect on P-selectin expression. Pharmacological blockade or knockout of α1G abolishes depolarization-induced Ca2+ entry and surface expression of P-selectin but does not prevent 4α-PDD-activated Ca2+ entry and the resultant increase in permeability. Conversely, blockade or knockout of TRPV4 specifically abolishes 4α-PDD-activated Ca2+ entry and the increase in permeability, while not impacting depolarization-induced Ca2+ entry and surface expression of P-selectin. We conclude that in alveolar septal capillaries Ca2+ entry through α1G and TRPV4 channels differentially and specifically regulates the transition of endothelial procoagulant phenotype and barrier integrity, respectively.
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Byrski, Jędrzej, e Witold Byrski. "State estimators and observers for continuous and discrete linear systems. Part 1. Differential asymptotic state estimators". Science, Technology and Innovation 3, n. 2 (27 dicembre 2018): 62–68. http://dx.doi.org/10.5604/01.3001.0012.8169.
Testo completoAbstract (sommario):
In the paper an overview of state estimators and state observers used in linear systems, will be presented. The state estimators and observers can be used in many applications like the state reconstruction for the control purposes or for the diagnosis and fault detection in technical processes or for the virtual measurements of inaccessible variables of the system as well as for the best filtration of the differential equation solution. As the standard most commonly the Kalman filter and Luenberger type observers are used. Although the Kalman filter guarantees optimal filtering quality of the state, reconstructed from the noisy measurements, both Kalman filter and the Luenberger observer guarantee only asymptotic quality of the real state changes and tracking, basing on the current measurements of the system output and input signals. Unfortunately, the value of the estimation error at any moment of time cannot be calculated. The discussion on differences between continuous and two types of discrete Kalman Filter will be presented. This paper is plan to be the introduction to presentation of the another type of the state observers which have the structure given by the integral operators. Based on measurements of the system output and input signals on some predefined finite time interval, they can reconstruct, after this interval, the observed state exactly.
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James-Curtis, B., e C. M. Wood. "KIDNEY AND URINARY BLADDER RESPONSES OF FRESHWATER RAINBOW TROUT TO ISOSMOTIC NaCl AND NaHCO3 INFUSION". Journal of Experimental Biology 173, n. 1 (1 dicembre 1992): 181–203. http://dx.doi.org/10.1242/jeb.173.1.181.
Testo completoAbstract (sommario):
The relative roles of the kidney and urinary bladder in ion, fluid and acid-base regulation were examined in freshwater rainbow trout chronically infused with either 140 mmol l-1 NaCl or 140 mmol l-1 NaHCO3 (3 ml kg-1 h-1) for 32 h. NaCl had a negligible effect on blood ionic and acid-base status, whereas NaHCO3 induced a metabolic alkalosis characterized by a rise in arterial pH and [HCO3-] and an equimolar fall in [Cl-]. Urine was collected via either an internal catheter, which bypassed bladder function, or an external urinary catheter, which collected naturally voided urine. As a percentage of the infusion rate, glomerular filtration rate increased by about 135 %, but urine flow rate (UFR) by only 80 %, reflecting increased tubular reabsorption of H2O. During NaCl infusion, virtually all of the extra Na+ and Cl- filtered was reabsorbed by the kidney tubules, resulting in an increased UFR with largely unchanged composition. During NaHCO3 infusion, tubular Na+ and Cl- reabsorption again kept pace with filtration. HCO3- reabsorption also increased, but did not keep pace with filtration; an increased flow of HCO3--rich urine resulted, which excreted about 10 % of the infused base load. At rest, fish fitted with external catheters voided in discrete bursts of about 0.85 ml kg-1 at 25 min intervals. During infusion, burst frequency increased by about 40 % and burst volume by about 20 %. Reabsorption by the bladder reduced UFR by 25 %, the excretion of Na+ and Cl- by 50 %, of K+ by 44 % and of urea by 25 %. These differences persisted on a relative basis during NaCl and NaHCO3 infusion despite the decreased residence time. However, HCO3- was neither secreted nor reabsorbed by the bladder. We conclude that the freshwater kidney functions to remove as much NaCl as possible from the urine, regardless of the NaCl load, and this role is supplemented by bladder function. The bladder plays no role in acid-base regulation during metabolic alkalosis.
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Amirfakhraei, Amirhossein, Jamshid Khorshidi e Taleb Zarei. "A thermodynamic modeling of 2-bed adsorption desalination to promote main equipment performance". Journal of Water Reuse and Desalination 11, n. 1 (5 gennaio 2021): 136–46. http://dx.doi.org/10.2166/wrd.2021.059.
Testo completoAbstract (sommario):
Abstract Adsorption desalination utilizes the discrete adsorption of the water vapor from the evaporator, and is capable of being discharged to the condenser. This study illuminated an advanced cycle of mass and heat recovery among beds, condensers, and evaporators. Morover, the thermodynamic modeling of adsorption desalination systems (ADS) under different operating conditions was investigated. Furthermore, its effect on the evaporator vapor production and the water vapor adsorption and desorption in the adsorption beds were accounted for. Parenthetically, the mathematical model of ADS thermodynamics was validated with the experimental data. Besides, the advanced ADS modeling was conducted via mass and heat recovery among beds, condensers, and evaporators. In addition to the amount of desalinated water, the time history chart of the equipment applied in the process with and without the thermal and mass recovery is also illustrated. Finally, under such operating conditions, the specific daily water production (SDWP) advanced ADS is 153% higher than conventional ADS.
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Langer, Stefan J., Rudolf Klute e Hermann H. Hahn. "Mechanisms of floc formation in sludge conditioning with polymers". Water Science and Technology 30, n. 8 (1 ottobre 1994): 129–38. http://dx.doi.org/10.2166/wst.1994.0396.
Testo completoAbstract (sommario):
In flocculation of dilute suspensions a period of slow mixing is necessary to increase the probability of particle collisions that are necessary for flocculation to occur. When flocculating sludges, the collision frequency is so high that flocs are formed immediately after rapid mixing. However, controlled mixing of the flocculated sludge for some time period does improve dewaterability. The mechanisms that are involved have been studied in detail and the subject of this paper. The results show that after rapid mixing and initial floc formation there might still be polymer in solution, depending on polymer dose. Prolonged mixing results in breakage of large aggregates and in particle/floc surfaces that are not yet covered with polymers. Subsequently the excess polymer adsorbs onto these surfaces. From changes in sludge rheology one can see that within a period of about one half to one minute the bulk properties change dramatically. After the initial floc formation the suspension is in a state characterized by a three-dimensional network structure with strongly interacting, voluminous flocs. After the mixing period there are more discrete and less interacting flocs. Especially the properties of the filter cake from pressure filtration are then more favorable.
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Phillips, James A., e Samuel J. Smidt. "Modeling Improved Performance of Reduced-Height Biosand Water Filter Designs". Water 12, n. 5 (8 maggio 2020): 1337. http://dx.doi.org/10.3390/w12051337.
Testo completoAbstract (sommario):
Point-of-use biosand water filters are widely distributed in undeveloped or developing regions due to their water treatment success and low-cost design, but two gaps remain in the basic technology: (1) the filter body is oversized relative to its contaminant removal performance, and (2) the heavy design largely excludes difficult to reach locations in need of clean water solutions. Here, we model design modifications to the v.10 Centre for Affordable Water and Sanitation Technology biosand filter using a reduced filter height, increased biolayer area, and conserved reservoir volume. We compare the hydraulic characteristics (dynamic velocity and head pressure) and percent contaminant removal of bacteria Escherichia coli and virus MS2 of the modified designs to the traditional control design using a finite element approximation of Darcy’s law with discrete time steps and a slow-sand filtration model. We demonstrate that a reduced-height design has a greater impact on contaminant removal compared to the traditional design (largely due to the increased residence time from the decreased flow rate inside the filter). For example, our 70% reduced-height filter design removed 99.5% and 73.93% of E. coli and MS2, respectively, where the traditional filter design removed 62.81% and 27.6%, respectively. Reduced-height designs should be pursued as a viable solution to improve filter performance while allowing for alternative construction techniques with greater end-user accessibility compared to the traditional design.
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Shcherbak, Yakiv, Yurii Semenenko, Olexandr Semenenko, Nadiia Karpenko, Olexandr Suprun, Oleksandr Plakhtii e Volodymyr Nerubatskyi. "Synthesis of the transfer function of the voltage controller in an active filter-stabilizer converter". Eastern-European Journal of Enterprise Technologies 2, n. 2 (110) (30 aprile 2021): 71–77. http://dx.doi.org/10.15587/1729-4061.2021.229827.
Testo completoAbstract (sommario):
It has been established that in order to ensure effective filtration and stabilization of the voltage of DC traction substations, it is advisable to use active filters-stabilizers. The dynamic characteristics of an active filter-stabilizer have been analyzed taking into consideration its discrete properties. It has been shown that the voltage converter in an active filter-stabilizer with bilateral pulse-width modulation for small values of control signal increment is an amplitude-pulse modulator of the second kind. In order to improve the efficiency of using an active filter-stabilizer, which is part of the DC traction substation converter, the task was set to synthesize the transfer function of its converter's voltage controller. When analyzing a closed automatic control system, it was established that the transfer function of the voltage controller, which ensures the implementation of processes of finite duration in the closed automatic control system, includes a proportional part, an integral part, and a differential part. To determine the time constants for the transfer function of the PID-controller, as well as its damping coefficient, a closed automatic control system of the active filter-stabilizer voltage converter was investigated using an apparatus of Z-transformation. The result of synthesizing the transfer function of the voltage controller has established the parameters for the controller's transfer function, which ensure that the process of finite duration is executed in a closed system of automatic control over the converter's output voltage. The transition process in the system with a stepwise input effect of the processes of finite duration has been calculated, which confirmed that the transition process in the system ends after three clock intervals of discreteness. Establishing a transition process that ends over the finite number of discrete intervals, which is determined by the order of the characteristic equation, means that the process has been optimized for performance
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Knight, Sarah, Nicholas Morley, Dónal Leech e Rachel Cave. "Mobile Voltammetric Laboratory for Ship-Board and Shore-Based Analyses of Dissolved Copper". Environmental Chemistry 3, n. 6 (2006): 450. http://dx.doi.org/10.1071/en06047.
Testo completoAbstract (sommario):
Environmental Context. Determining concentrations of dissolved copper in seawater is of interest, because copper (i) affects the health of aquatic biota, and (ii) has the potential to act as a water mass tracer, a marker which can be used to follow the movement of water in oceans. In situ analyses of copper and other trace metals in seawater have become increasingly popular, because they circumvent potential contamination problems associated with sample collection, storage, and transport to off-site analysis locations. This paper describes the assembly of a low-cost, mobile laboratory utilizing adsorptive cathodic stripping voltammetry (AdCSV) for the real-time determination of total dissolved copper in surface waters. Abstract. The main advantages of using a mobile laboratory for the real-time analyses of copper in surface waters over classical discrete sampling include a reduction in the risk of sample contamination and significant savings in both time and money to the analyst. This paper outlines the development of a portable voltammetric laboratory, capable of deployment from ships or road vehicles, and an experimental method for the real time analysis of total dissolved copper in surface waters. It has been tested in estuarine and coastal waters to the west of Ireland and has proved suitable for the analysis of both fresh and marine waters. The system includes a trace metal-free sampling fish (for shipboard sampling), in-line filtration and UV-digestion units, and a voltammetric analyzer and electrode controlled by a portable PC. Analysis of samples is completed using adsorptive cathodic stripping voltammetry (AdCSV). Using this portable AdCSV laboratory, the high sample throughput – approximately three per hour with standard additions completed on every sample – means that for ship-board surveys good spatial coverage is possible without the need for time-consuming station stops. For van-based tidal surveys, the portable AdCSV laboratory is both straightforward and low in cost to deploy.
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Panfilov, Ivan, Alexey N. Beskopylny e Besarion Meskhi. "Numerical Simulation of Heat Transfer and Spread of Virus Particles in the Car Interior". Mathematics 11, n. 3 (3 febbraio 2023): 784. http://dx.doi.org/10.3390/math11030784.
Testo completoAbstract (sommario):
The epidemic caused by the coronavirus infection SARS-CoV-2 at the beginning of 2022 affected approximately 500 million people in all countries. The source of infection is the particles of the virus, which, when breathing, talking, and coughing, are released with the respiratory droplets and aerosol dust of an infected person. Actions aimed at combating and minimizing the consequences of coronavirus infection led to taking measures in scientific areas to investigate the processes of the spread of viral particles in the air, in ventilation, and air conditioning systems of premises and transport, filtration through masks, the effect of partitions, face shields, etc. The article presents a mathematical model of the spread of viral particles in technological transport. Air intake diverters and the operator’s respiratory tract are the sources of the virus. The Euler–Lagrange approach was used to simulate liquid droplets in a flow. Here, the liquid phase is considered as a continuous medium using Navier–Stokes equations, the continuity equation, the energy equation, and the diffusion equation. Accounting for diffusion makes it possible to explicitly model air humidity and is necessary to consider the evaporation of droplets (changes in the mass and size of particles containing the virus). Liquid droplets are modeled using the discrete-phase model (DPM), in which each particle is tracked in a Lagrange coordinate system. The DPM method is effective, since the volume fraction of particles is small relative to the total volume of the medium, and the interaction of particles with each other can be neglected. In this case, the discrete and continuous phases are interconnected through the source terms in the equations. The averaged RANS equations are solved numerically using the k-ω turbulence model in the Ansys Fluent package. The task was solved in a static form and in the time domain. For a non-stationary problem, the stabilization time of the variables is found. The simulation results are obtained in the form of fields of pressures, velocities, temperatures and air densities, and the field of propagation of particles containing the virus. Various regimes were studied at various free flow rates and initial velocities of droplets with viral particles. The results of trajectories and velocities of particles, and particle concentrations depending on time, size, and on the evaporability of particles are obtained.
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Deline, Bradley, William I. Ausich e Carlton E. Brett. "Comparing taxonomic and geographic scales in the morphologic disparity of Ordovician through Early Silurian Laurentian crinoids". Paleobiology 38, n. 4 (2012): 538–53. http://dx.doi.org/10.1666/11063.1.
Testo completoAbstract (sommario):
Interpretations of morphologic radiations and macroevolutionary patterns are dependent on a priori choices of taxonomic and geographic scales of study. The results of disparity analysis at varying taxonomic (species and genus) and geographic (regional, biofacies, and community) scales are examined in a study of Ordovician though Early Silurian crinoids. Using discrete morphologic characters, we examined the disparity of 421 crinoids from 65 Laurentian biofacies. Crinoid disparity differs when analyzed at the regional and biofacies levels. Regardless of fluctuations in regional crinoid disparity, average within-biofacies disparity was static throughout the Ordovician, deviating only during the Silurian because of the proliferation of the morphologically aberrant myelodactylid crinoids. The choice of taxonomic level does not have an effect at the biofacies level. However, at the regional level, the two taxonomic scales (genus and species) can produce different results because of variation in the number of species per genus through time and the amount of morphologic variation within individual genera. Weighting disparity by abundance provides a metric combining morphology and community structure. Average weighted disparity at the community level showed patterns similar to that of the biofacies-level disparity curve, but this metric has a greater degree of variation between biofacies. Biofacies with a low ratio of weighted to unweighted disparity display the distinctive community structure (based on aerosol filtration theory) that is often reported in crinoid assemblages.
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Balasubramanian, S., Mahaveer Singh Naruka e Gaurav Tewari. "Denoising ECG Signal Using DWT with EAVO". International Journal on Recent and Innovation Trends in Computing and Communication 11, n. 3s (11 marzo 2023): 231–37. http://dx.doi.org/10.17762/ijritcc.v11i3s.6184.
Testo completoAbstract (sommario):
Cardiovascular diseases are the leading cause of death across the world, and traditional methods for determining cardiac health are highly invasive and expensive. Detecting CVDs early is critical for effective treatment, yet traditional detection methods lack accessibility, accuracy, and cost-effectiveness – leaving patients with little hope of taking control of their own cardiac health. Noisy ECG signals make it difficult for health practitioners to accurately read and determine heart health. Unreliable readings can lead to misdiagnosis and needless expense. Despite the importance of ECG analysis, traditional methods of signal denoising are inefficient and can produce inaccurate results. This means that medical practitioners are struggling to obtain reliable readings, leaving them unable to accurately treat their patients and leading to a lack of confidence in the medical field. The Enhanced African Vulture Optimization (AVO) algorithm with Discrete Wavelet Transform (DWT) optimized by adaptive switching mean filtration (SMF) is proven to provide accurate denoising of the ECG signal. With this reliable method, medical professionals can quickly and accurately diagnose patients. Obtaining accurate ECG signals and interpreting them quickly is a challenge for healthcare professionals. Not only it takes a lot of time and skill but also requires specialized software to interpret the signals accurately. Healthcare professionals are facing a serious challenge when it comes to obtaining accurate ECG signals and interpreting them quickly. It requires them to spend extra time and effort, as well as specialize in the field with expensive software. Time is of the essence in healthcare and ECG readings can mean the difference between life and death. Specialized software can be expensive and time-consuming for those who don't have the resources or expertise. Our easy-to-use platform allows healthcare professionals to quickly interpret ECG signals, saving time, money, and lives! Get accurate readings. The EAVO algorithm and MIT-BIH dataset provide an effective solution to this problem. With the proposed filter built using EAVO, businesses can attain significant enhancements in reliable parameters and obtain accurate testing results in terms of SNR, MD, MSE and NRMSE.
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Liu, Keqi, Wantao Ding e Chunxu Qu. "A Mesoscopic Viewpoint on Slurry Penetration and Pressure Transfer Mechanisms for Slurry Shield Tunneling". Buildings 12, n. 10 (19 ottobre 2022): 1744. http://dx.doi.org/10.3390/buildings12101744.
Testo completoAbstract (sommario):
The penetration characteristics of the slurry and the support pressure transfer mechanisms are critical to the tunnel face stability control during a mechanized excavation. In this paper, numerical calculations coupling computational fluid dynamics (CFD) with the discrete element method (DEM) are carried out to simulate sand column penetration tests considering different particle size ratios. The reasonableness of the numerical model is verified by comparing the variation patterns of the soil permeability coefficients monitored in the numerical tests with the results of existing laboratory tests. The mesoscopic transport characteristics of the slurry particles in the sand soil pores are considered based on numerical tests, while the slurry support effects corresponding to different penetration types are evaluated. Three main basic types of slurry infiltration are observed due to the different ratios of slurry particle size over soil pore size. For the first penetration type, the slurry particles are accumulated and able to form a supporting filter cake. The slurry support is effective because of the significant pressure drop generated on both sides of the filter cake. For the second penetration type, both a filter cake and an infiltration zone are present. A dense filling network is formed between the filter cake and the penetration zone. The third type corresponds to a purely penetration zone. An effective impermeable filling network cannot be formed, and the slurry support effect is not obvious. The development of slurry penetration distance shows an obvious time effect; the farther the penetration distance, the larger the slurry filtration loss, and the worse the transformation effect of slurry support pressure.
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Mesri, Mehdi, e Dario C. Altieri. "Endothelial Cell Activation by Leukocyte Microparticles". Journal of Immunology 161, n. 8 (15 ottobre 1998): 4382–87. http://dx.doi.org/10.4049/jimmunol.161.8.4382.
Testo completoAbstract (sommario):
Abstract The ability of polymorphonuclear leukocytes (PMNs) to modulate endothelial cell (EC) activation was investigated. Adding PMNs to cultured HUVECs resulted in a release of IL-6 (888 ± 71 pg/ml, a 35-fold increase over release by the two cell types alone) and IL-8 (45.2 ± 14.5 ng/ml, a 6.4-fold over PMN release alone and a 173-fold increase over EC release alone). In contrast, the release of TNF-α, IL-1β, and platelet-derived growth factor was not affected by the EC-PMN coculture. Neutralizing mAbs to ICAM-1 or β2 integrins or a physical segregation of PMNs and ECs did not reduce EC stimulation. In contrast, cell-free supernatants of PMNs recapitulated EC activation with an 18-fold up-regulation of EC IL-6 mRNA. The filtration of PMN supernatant or PMN pretreatment with metabolic antagonists or membrane cross-linking agents all suppressed EC activation. By flow cytometry, PMNs released in the supernatant, heterogeneous membrane-derived microparticles containing discrete proteins of 28 to 250 kDa as resolved by SDS-PAGE. PMN microparticle formation was enhanced by inflammatory stimuli, including formyl peptide and phorbol ester, and was time-dependent, reaching a plateau after a 1-h incubation from stimulation. Purified PMN microparticles induced EC IL-6 release in a reaction that was quantitatively indistinguishable from that observed with unfractionated PMN supernatant and unaffected by a neutralizing Ab to soluble IL-6R. These findings demonstrate that membrane microparticles released from stimulated PMNs are competent inflammatory mediators to produce EC activation and cytokine gene induction.
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Garzon, Max, Petr Sosik, Jan Drastík e Omar Skalli. "A Self-Controlled and Self-Healing Model of Bacterial Cells". Membranes 12, n. 7 (30 giugno 2022): 678. http://dx.doi.org/10.3390/membranes12070678.
Testo completoAbstract (sommario):
A new kind of self-assembly model, morphogenetic (M) systems, assembles spatial units into larger structures through local interactions of simpler components and enables discovery of new principles for cellular membrane assembly, development, and its interface function. The model is based on interactions among three kinds of constitutive objects such as tiles and protein-like elements in discrete time and continuous 3D space. It was motivated by achieving a balance between three conflicting goals: biological, physical-chemical, and computational realism. A recent example is a unified model of morphogenesis of a single biological cell, its membrane and cytoskeleton formation, and finally, its self-reproduction. Here, a family of dynamic M systems (Mbac) is described with similar characteristics, modeling the process of bacterial cell formation and division that exhibits bacterial behaviors of living cells at the macro-level (including cell growth that is self-controlled and sensitive to the presence/absence of nutrients transported through membranes), as well as self-healing properties. Remarkably, it consists of only 20 or so developmental rules. Furthermore, since the model exhibits membrane formation and septic mitosis, it affords more rigorous definitions of concepts such as injury and self-healing that enable quantitative analyses of these kinds of properties. Mbac shows that self-assembly and interactions of living organisms with their environments and membrane interfaces are critical for self-healing, and that these properties can be defined and quantified more rigorously and precisely, despite their complexity.
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Wang, Hao, Xinyuanrui Wang, Yongping Wu, Song Wang, Junfei Wu, Ping Fu e Yang Li. "Study of CFD-DEM on the Impact of the Rolling Friction Coefficient on Deposition of Lignin Particles in a Single Ceramic Membrane Pore". Membranes 13, n. 4 (27 marzo 2023): 382. http://dx.doi.org/10.3390/membranes13040382.
Testo completoAbstract (sommario):
The discrete element method coupled with the computational fluid dynamic (CFD-DEM) method is effective for studying the micro-flow process of lignin particles in ceramic membranes. Lignin particles may exhibit various shapes in industry, so it is difficult to model their real shapes in CFD-DEM coupled solutions. Meanwhile, the solution of non-spherical particles requires a very small time-step, which significantly lowers the computational efficiency. Based on this, we proposed a method to simplify the shape of lignin particles into spheres. However, the rolling friction coefficient during the replacement was hard to be obtained. Therefore, the CFD-DEM method was employed to simulate the deposition of lignin particles on a ceramic membrane. Impacts of the rolling friction coefficient on the deposition morphology of the lignin particles were analyzed. The coordination number and porosity of the lignin particles after deposition were calculated, based on which the rolling friction coefficient was calibrated. The results indicated that the deposition morphology, coordination number, and porosity of the lignin particles can be significantly affected by the rolling friction coefficient and slightly influenced by that between the lignin particles and membranes. When the rolling friction coefficient among different particles increased from 0.1 to 3.0, the average coordination number decreased from 3.96 to 2.73, and the porosity increased from 0.65 to 0.73. Besides, when the rolling friction coefficient among the lignin particles was set to 0.6–2.4, the spherical lignin particles could replace the non-spherical particles.
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Zhang, Xiuming, Tao Liu e Chunhua Tian. "Artificial Intelligence Algorithm-Based Computed Tomography Image in Assessment of Acute Renal Insufficiency of Patients Undergoing Percutaneous Coronary Intervention". Contrast Media & Molecular Imaging 2022 (28 febbraio 2022): 1–10. http://dx.doi.org/10.1155/2022/2214583.
Testo completoAbstract (sommario):
This study was aimed to analyze the changes in renal function of patients undergoing percutaneous coronary intervention (PCI) surgery and the characteristics of their computed tomography (CT) image based on artificial intelligence algorithms. In this study, 104 patients with coronary atherosclerotic heart disease (CAHD) were treated as the research objects. They were divided into an experimental group (patients who underwent CAG and PCI within 1 week after enhanced coronary CT (ECCT)) and the control group (patients who underwent CAG and PCI within 1–3 weeks after ECCT). Renal imaging scans of patients were performed by CT based on discrete inseparable shear transform (DNST) optimized algorithm, which was named as O-DNST. The results showed that the serum creatinine (Scr), blood urea nitrogen (BUN), and urine protein (UP) levels of patients in the experimental group were significantly higher than those of the control group 24–72 hours after surgery, while the levels of endogenous creatinine clearance (Ccr) and estimated glomerular filtration rate (eGFR) were significantly lower than those of the control group ( P < 0.05). The levels of β2 microglobulin (β2-MG), C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor (TNF-α) in the experimental group were significantly higher than those in the control group 24–72 hours after surgery ( P < 0.05). The incidence of contrast-induced nephropathy (CIN) in the experimental group (15.38%) was significantly higher than that in the control group (5.8%), and the difference was statistically significant ( P < 0.05). The results showed that repeated application of contrast agent in a short period of time can promote the increase of serum inflammation levels in PCI patients, which may be a risk factor for CIN in PCI patients.
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Dritselis, Chris D., Fotini Tzorbatzoglou, Marios Mastrokalos e Onoufrios Haralampous. "Numerical Study of Flow and Particle Deposition in Wall-Flow Filters with Intact or Damaged Exit". Fluids 4, n. 4 (2 dicembre 2019): 201. http://dx.doi.org/10.3390/fluids4040201.
Testo completoAbstract (sommario):
We examine the time-dependent three-dimensional gas-particle flow in an intact wall-flow filter consisting of channels alternatively plugged at each end and a partially damaged filter in which the rear plugs are removed. Our focus is placed on highlighting the differences in the flow pattern and the deposition process between the two geometries. The Navier–Stokes equations are solved for the fluid flow coupled with a Brinkman/Forchheimmer model in order to simulate the flow in the porous walls and plugs. Discrete particle simulation is utilized to determine the nanoparticle trajectories. Using this scheme, we are able to characterize the main features of the flow fields developing in the intact and damaged filters with respect to the Reynolds number and identify those affecting the transport and deposition of particles that have three representative response times. We present fluid velocity iso-contours, which describe the flow regimes inside the channels, as well as in regions upstream and downstream of them. We provide evidence of local recirculating bubbles at the entrance of the channels and after their exit, whereas back-flow occurs in front of the rear plugs of the intact channels. We show that the flow leaves the channels as strong jets that may break up for certain flow parameters, leading to turbulence with features that depend on the presence of the rear plugs. The removal of the rear plugs affects the flow distribution, which, in turn influences the flow rates along the channels and through the walls. We describe the particle trajectories and the topology of deposited particles and show that particles follow closely the streamlines, which may cross the surface of permeable walls for both flow configurations. The distribution of deposited particles resembles the spatial variation of the through-wall flow rate, exhibiting two peak values at both ends of the intact filter channel, and one local maximum near the entrance of the damaged filter channel that is diminished at the exit. We also investigate in detail the particle deposition on the frontal face and indicate that particle accumulation at the edges of the entrance is favored for particles with low response times in flows with high fluid mass rates for both intact and damaged filters. Finally, we examine the filtration efficiency for the defective channels without rear plugs and show that fewer particles are captured as the Reynolds number is increased. A smaller reduction of the filtration efficiency is also predicted with increasing particle size.
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Anosov, Andrey, Elizaveta Borisova, Elena Smirnova, Eugenia Korepanova e Anatoly Osipov. "Effect of Cytochrome C on the Conductance of Asolectin Membranes and the Occurrence of Through Pores at Different pHs". Membranes 13, n. 3 (24 febbraio 2023): 268. http://dx.doi.org/10.3390/membranes13030268.
Testo completoAbstract (sommario):
The study of the electrical parameters of asolectin bilayer lipid membranes in the presence of cytochrome c (cyt c) at various concentrations showed that an increase in the concentration of cyt c leads to an increase in the membrane conductance and the appearance of through pores. The studied membranes did not contain cardiolipin, which is commonly used in studying the effect of cyt c on membrane permeability. In the presence of cyt c, discrete current fluctuations were recorded. The occurrence of these fluctuations may be associated with the formation of through pores. The diameter of these pores was ~0.8 nm, which is smaller than the size of the cyt c globule (~3 nm). Measurements carried out at pH values from 6.4 to 8.4 showed that the concentration dependence of the membrane conductance increases with increasing pH. To assess the binding of cyt c to the bilayer, we measured the concentration and pH dependences of the difference in surface potentials induced by the unilateral addition of cyt c. The amount of bound cyt c at the same concentrations decreased with increasing pH, which did not correspond to the conductance trend. An analysis of conductance traces leads to the conclusion that an increase in the integral conductance of membranes is associated with an increase in the lifetime of pores. The formation of “long-lived” pores, of which the residence time in the open state is longer than in the closed state, was achieved at various combinations of pHs and cyt c concentrations: the higher the pH, the lower the concentration at which the long-lived pores appeared and, accordingly, a higher conductance was observed. The increase in conductance and the formation of transmembrane pores are not due to the electrostatic interaction between cyt c and the membrane. We hypothesize that an increase in pH leads to a weakening of hydrogen bonds between lipid heads, which allows cyt c molecules to penetrate into the membrane. This disrupts the order of the bilayer and leads to the occurrence of through pores.