Articles de revues sur le sujet « Minimum entropy coupling »
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1
Li, Cheuk Ting. « Efficient Approximate Minimum Entropy Coupling of Multiple Probability Distributions ». IEEE Transactions on Information Theory 67, no 8 (août 2021) : 5259–68. http://dx.doi.org/10.1109/tit.2021.3076986.
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Hidouri, Nejib, Imen Chermiti et Ammar Ben Brahim. « Second Law Analysis of a Gas-Liquid Absorption Film ». Journal of Thermodynamics 2013 (25 février 2013) : 1–10. http://dx.doi.org/10.1155/2013/909162.
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This paper reports an analytical study of the second law in the case of gas absorption into a laminar falling viscous incompressible liquid film. Velocity, temperature, and concentration profiles are determined and used for the entropy generation calculation. Irreversibilities due to heat transfer, fluid friction, and coupling effects between heat and mass transfer are derived. The obtained results show that entropy generation is mainly due to coupling effects between heat and mass transfer near the gas-liquid interface. Total irreversibility is minimum at the diffusion film thickness. On approaching the liquid film thickness, entropy generation is mainly due to viscous irreversibility.
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Campos, S. D. « Chiral Symmetry Restoration Using the Running Coupling Constant from the Light-Front Approach to QCD ». Ukrainian Journal of Physics 67, no 3 (19 mai 2022) : 151. http://dx.doi.org/10.15407/ujpe67.3.151.
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In this work, the distance between a quark-antiquark pair is analyzed through both the confinement potential and the hadronic total cross- section. Using the Helmholtz free energy, the entropy is calculated near the minimum of the total cross-section through the confinement potential. A fitting procedure for the proton-proton total cross- section is carried out, defining the fit parameters. Therefore, the only remaining free parameter in the model is the mass-scale к used to define the running coupling constant of the light-front the approach to QCD. The mass scale controls the distance r between the quark-antiquark pair and, under some conditions, allows the appearance of free quarks even within the confinement regime of QCD.
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STARIKOV, EVGENI B., DIRK HENNIG et BENGT NORDÉN. « PROTEIN FOLDING AS A RESULT OF 'SELF-REGULATED STOCHASTIC RESONANCE' : A NEW PARADIGM ? » Biophysical Reviews and Letters 03, no 03 (juillet 2008) : 343–63. http://dx.doi.org/10.1142/s1793048008000800.
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We scrutinize the available (seemingly disparate) theories of protein folding and propose a new concept which brings them under one roof. First, we single out dipole–dipole coupling within protein backbone as the main reason for intrinsic double-well nature of the protein potential. Then, protein folding as a whole ought to be (at least) a two-stage process, namely: (a) both amino-acid side chains and solvent enslave the dynamics of the backbone to reach the folding transition state with the help of stochastic resonance, and (b) the backbone funnels the whole protein into the global potential energy minimum by enslaving the dynamics of the amino-acid side chains plus solvent, and simultaneously arresting the stochastic resonance prerequisites to lock the protein in its folded state. The latter is accomplished owing to the concerted action of the protein compactization (enthalpic contribution) and thermal motion intensification (entropic contribution), which is, in fact, a physical hallmark of enthalpy–entropy compensation.
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Feidt, Michel, et Monica Costea. « Effect of Machine Entropy Production on the Optimal Performance of a Refrigerator ». Entropy 22, no 9 (20 août 2020) : 913. http://dx.doi.org/10.3390/e22090913.
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The need for cooling is more and more important in current applications, as environmental constraints become more and more restrictive. Therefore, the optimization of reverse cycle machines is currently required. This optimization could be split in two parts, namely, (1) the design optimization, leading to an optimal dimensioning to fulfill the specific demand (static or nominal steady state optimization); and (2) the dynamic optimization, where the demand fluctuates, and the system must be continuously adapted. Thus, the variability of the system load (with or without storage) implies its careful control-command. The topic of this paper is concerned with part (1) and proposes a novel and more complete modeling of an irreversible Carnot refrigerator that involves the coupling between sink (source) and machine through a heat transfer constraint. Moreover, it induces the choice of a reference heat transfer entropy, which is the heat transfer entropy at the source of a Carnot irreversible refrigerator. The thermodynamic optimization of the refrigerator provides new results regarding the optimal allocation of heat transfer conductances and minimum energy consumption with associated coefficient of performance (COP) when various forms of entropy production owing to internal irreversibility are considered. The reported results and their consequences represent a new fundamental step forward regarding the performance upper bound of Carnot irreversible refrigerator.
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Hu, Xianyang, Changzheng Ma, Ruizhi Hu et Tat Yeo. « Imaging for Small UAV-Borne FMCW SAR ». Sensors 19, no 1 (27 décembre 2018) : 87. http://dx.doi.org/10.3390/s19010087.
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Unmanned aerial vehicle borne frequency modulated continuous wave synthetic aperture radars are attracting more and more attention due to their low cost and flexible operation capacity, including the ability to capture images at different elevation angles for precise target identification. However, small unmanned aerial vehicles suffer from large trajectory deviation and severe range-azimuth coupling due to their simple navigational control and susceptibility to air turbulence. In this paper, we utilize the squint minimization technique to reduce this coupling while simultaneously eliminating intra-pulse motion-induced effects with an additional spectrum scaling. After which, the modified range doppler algorithm is derived for second order range compression and block-wise range cell migration correction. Raw data-based motion compensation is carried out with a doppler tracker. Squinted azimuth dependent phase gradient algorithm is employed to deal with azimuth dependent parameters and inexact deramping, with minimum entropy-based autofocusing algorithms. Finally, azimuth nonlinear chirp scaling is used for azimuth compression. Simulation and real data experiment results presented verify the effectiveness of the above signal processing approach.
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Wang, Binbin, Hao Cha, Zibo Zhou, Huatao Tang, Lidong Sun, Baozhou Du et Lei Zuo. « An Iterative Phase Autofocus Approach for ISAR Imaging of Maneuvering Targets ». Electronics 10, no 17 (30 août 2021) : 2100. http://dx.doi.org/10.3390/electronics10172100.
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Translational motion compensation and azimuth compression are two essential processes in inverse synthetic aperture radar (ISAR) imaging. The anterior process recovers coherence between pulses, during which the phase autofocus algorithm is usually used. For ISAR imaging of maneuvering targets, conventional phase autofocus methods cannot effectively eliminate the phase error due to the adverse influence of the quadratic phase terms caused by the target’s maneuvering motion, which leads to the blurring of ISAR images. To address this problem, an iterative phase autofocus approach for ISAR imaging of maneuvering targets is proposed in this paper. Considering the coupling between translational phase errors and quadratic phase terms, minimum entropy-based autofocus (MEA) method and adaptive modified Fourier transform (MFT) are performed iteratively to realize better imaging results. In this way, both the translational phase error and quadratic phase terms induced by target’s maneuvering motion can be compensated effectively, and the globally optimal ISAR image is obtained. Comparison ISAR imaging results indicates that the new approach achieves stable and better ISAR image under a simple procedure. Experimental results show that the image entropy of the proposed approach is 0.2 smaller than the MEA method, which validates the effectiveness of the new approach.
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Unno, W., et D. R. Xiong. « One Zone Modeling of Irregular Variability of Stellar Convective Envelope ». International Astronomical Union Colloquium 134 (1993) : 77–81. http://dx.doi.org/10.1017/s0252921100013956.
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AbstractOne zone modeling of the irregular variability of red super-giants is intended with regard to the nonlinear coupling of finite amplitude pulsation with convection. The nonlocal mixing length is employed for the evaluation of the convective flux, the turbulent pressure and the turbulent power of temperature fluctuations. The radial pulsation and the Boussinesq convection are assumed for simplicity. The one zone is defined as the layer having the entropy maximum and the minimum at the bottom and at the top, respectively. The quasi-adiabatic approximation is consistent with this definition in fixing the zone to the same mass range. The spatial derivatives are evaluated under the assumption of homologous changes with the equilibrium homologous parameters. Then, a set of 6 simultaneous first order nonlinear ordinary differential equations are obtained as the one zone representation of the irregular variability of the convective envelope.
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Unnikrishnan, K. « Comparison of chaotic aspects of magnetosphere under various physical conditions using AE index time series ». Annales Geophysicae 26, no 4 (13 mai 2008) : 941–53. http://dx.doi.org/10.5194/angeo-26-941-2008.
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Abstract. The deterministic chaotic behaviour of magnetosphere was analyzed, using AE index time series. The significant chaotic quantifiers like, Lyapunov exponent, spatio-temporal entropy and nonlinear prediction error for AE index time series under various physical conditions were estimated and compared. During high solar activity (1991), the values of Lyapunov exponent for AE index time series representing quiet conditions (yearly mean = 0.5±0.1 min−1) have no significant difference from those values for corresponding storm conditions (yearly mean = 0.5±0.17 min−1). This implies that, for the cases considered here, geomagnetic storms may not be an additional source to increase or decrease the deterministic chaotic aspects of magnetosphere, especially during high solar activity. During solar minimum period (1994), the seasonal mean value of Lyapunov exponent for AE index time series belong to quiet periods in winter (0.7±0.11 min−1) is higher compared to corresponding value of storm periods in winter (0.36±0.09 min−1). This may be due to the fact that, stochastic part, which is Dst dependent could be more prominent during storms, thereby increasing fluctuations/stochasticity and reducing determinism in AE index time series during storms. It is observed that, during low solar active period (1994), the seasonal mean value of entropy for time series representing storm periods of equinox is greater than that for quiet periods. However, significant difference is not observed between storm and quiet time values of entropy during high solar activity (1991), which is also true for nonlinear prediction error for both low and high solar activities. In the case of both high and low solar activities, the higher standard deviations of yearly mean Lyapunov exponent values for AE index time series for storm periods compared to those for quiet periods might be due to the strong interplay between stochasticity and determinism during storms. It is inferred that, the external driving forces, mainly due to solar wind, make the solar-magnetosphere-ionosphere coupling more complex, which generates many active degrees of freedom with various levels of coupling among them, under various physical conditions. Hence, the superposition of a large number of active degrees of freedom can modify the stability/instability conditions of magnetosphere.
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Ramakrishna, Satish. « A thermodynamic origin for the Cohen-Kaplan-Nelson bound ». Europhysics Letters 136, no 3 (1 novembre 2021) : 31001. http://dx.doi.org/10.1209/0295-5075/ac49d2.
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Abstract The Cohen-Kaplan-Nelson bound is imposed on the grounds of logical consistency (with classical General Relativity) upon local quantum field theories. This paper puts the bound into the context of a thermodynamic principle applicable to a field with a particular equation of state in an expanding universe. This is achieved without overtly appealing to either a decreasing density of states or a minimum coupling requirement, though they might still be consistent with the results described. We do so by defining an appropriate Helmholtz free energy which when extremized relative to a key parameter (the Hubble radius L) provides a scaling formula for the entropy with the Hubble radius (an exponent r used in the text). We deduce that the CKN bound is one possible solution to this extremization problem (with ), but there are others consistent with r = 2. The paper establishes that the holographic principle applied to cosmology is consistent with minimizing the free energy of the universe in the canonical ensemble, upon the assumption that the ultraviolet cutoff is a function of the causal horizon scale.
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MENDOZA-ARENAS, J. J., R. FRANCO et J. SILVA-VALENCIA. « ENTANGLEMENT IN THE ANISOTROPIC KONDO NECKLACE MODEL ». International Journal of Modern Physics B 24, no 31 (20 décembre 2010) : 6165–74. http://dx.doi.org/10.1142/s0217979210055433.
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We study the entanglement in the one-dimensional Kondo necklace model with exact diagonalization, calculating the concurrence as a function of the Kondo coupling J and an anisotropy η in the interaction between conduction spins, and we review some results previously obtained in the limiting cases η = 0 and 1. We observe that as J increases, localized and conduction spins get more entangled, while neighboring conduction spins diminish their concurrence; localized spins require a minimum concurrence between conduction spins to be entangled. The anisotropy η diminishes the entanglement for neighboring spins when it increases, driving the system to the Ising limit η = 1 where conduction spins are not entangled. We observe that the concurrence does not give information about the quantum phase transition in the anisotropic Kondo necklace model (between a Kondo singlet and an antiferromagnetic state), but calculating the von Neumann block entropy with the density matrix renormalization group in a chain of 100 sites for the Ising limit indicates that this quantity is useful for locating the quantum critical point.
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Cicalese, Ferdinando, Luisa Gargano et Ugo Vaccaro. « Minimum-Entropy Couplings and Their Applications ». IEEE Transactions on Information Theory 65, no 6 (juin 2019) : 3436–51. http://dx.doi.org/10.1109/tit.2019.2894519.
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Wang, Xian-Bo, Pu Miao, Kun Zhang, Xiaoyuan Zhang et Jun Wang. « Study on novel signal processing and simultaneous-fault diagnostic method for wind turbine ». Transactions of the Institute of Measurement and Control 41, no 14 (23 mai 2019) : 4100–4113. http://dx.doi.org/10.1177/0142331219849261.
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High-precision fault diagnosis is important for the widely installed complex industrial product, the wind turbine. However, intelligent monitoring is difficult due to the fuzzy boundaries and individual different variations of the unseen single or simultaneous-fault of such intricate equipment. To solve this problem, this study proposes an ensemble fault diagnostic framework for simultaneous and coupling failure. First, this paper develops novel signal processing methods for effective feature learning and mapping from the non-stationary and nonlinear raw vibrational signals. The adapted variational mode decomposition is introduced based on the particle swarm optimization that applies the minimum mean envelope entropy to optimize the parameters settings. Second, the novel ensemble extreme learning machine-based network is proposed to isolate the faults that applies one extreme learning machine network to count the number of fault scenarios, and the other one to identify the specific single or simultaneous-fault labels. With this scheme, the self-adaptive ensemble extreme learning machine-based fault diagnostic framework is more accurate and faster than the prevailing probabilistic classifier-based methods, as the proposed method does not rely on empirically specified decision-making threshold and generates all the candidate fault labels at the same time. Finally, this study builds the test platform and compares the overall results with the existing feature analysis methods and classifiers. The experimental results verify that the proposed framework detects both single and simultaneous-fault accurately and quickly.
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Zhang, Xueling, Ruoxuan Huang et Yixuan Yang. « On the Landscape Activity Measure Coupling Ecological Index and Public Vitality Index of UGI : The Case Study of Zhongshan, China ». Land 11, no 11 (22 octobre 2022) : 1879. http://dx.doi.org/10.3390/land11111879.
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In the context of high-quality urban development and the increasingly important role of urban green infrastructure (UGI) in public life, landscape activity (LA) has gradually become a dominant indicator for improving UGI quality and efficiency, as well as optimizing its environmental friendliness and meeting the recreational needs of the public. Relevant studies have shown that the ecological index (EI) and the public vitality index (PVI) can characterize LA from the perspectives of greening quality and public activities, respectively, and their simultaneous analysis can provide professional judgment and quantitative technical approaches for the LA analysis of UGI. At the same time, with the support of remote sensing, big data, GIS, and other spatial information data, the LA model coupling EI and PVI of UGI needs to be developed. First, this article established a research framework for UGI landscape activity, and by combining environmental remote sensing and location-based services (LBS) technology, a technical LA measurement strategy suitable for the coupled analysis of EI and PVI was formed. Then, based on the MATLAB platform and the entropy-weighted TOPSIS model, this research developed a fusion analysis algorithm of EI and PVI to establish the LA model, taking the central urban area of Zhongshan as a case study. Finally, four-quadrant classification and quantitative grading of LA were developed based on the ArcGIS platform. Empirical research showed that the UGI area of the study area was about 176.43 km2, and 160 UGI units were identified. The minimum LA value is 0.06, and the maximum is 0.85. The LA of UGI in the study area can be divided into three grades: low (0–0.24), medium (0.24–0.46), and high (0.46–0.85). Among them, the top 5% of UGI units mainly correspond to urban parks and waterfront greenways, and the bottom 5% mainly correspond to islands and farmland. The quantitative distribution of UGI in the four quadrants of LA in the study area is relatively balanced: among them, the number of high-quality developing types is the largest, accounting for 29.4%, and that of high-quality mature types is the least, accounting for 20.0%. This article forms a concise model and technical process for the LA of UGI, which can be used for its quantitative analysis and evaluation. It is expected that the research result will be significant for the high-quality construction of UGI and the sustainable development of the urban landscape in terms of research and exploration.
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Zhou, Yan, Pedro Ojeda-May, Mulpuri Nagaraju, Bryant Kim et Jingzhi Pu. « Mapping Free Energy Pathways for ATP Hydrolysis in the E. coli ABC Transporter HlyB by the String Method ». Molecules 23, no 10 (16 octobre 2018) : 2652. http://dx.doi.org/10.3390/molecules23102652.
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HlyB functions as an adenosine triphosphate (ATP)-binding cassette (ABC) transporter that enables bacteria to secrete toxins at the expense of ATP hydrolysis. Our previous work, based on potential energy profiles from combined quantum mechanical and molecular mechanical (QM/MM) calculations, has suggested that the highly conserved H-loop His residue H662 in the nucleotide binding domain (NBD) of E. coli HlyB may catalyze the hydrolysis of ATP through proton relay. To further test this hypothesis when entropic contributions are taken into account, we obtained QM/MM minimum free energy paths (MFEPs) for the HlyB reaction, making use of the string method in collective variables. The free energy profiles along the MFEPs confirm the direct participation of H662 in catalysis. The MFEP simulations of HlyB also reveal an intimate coupling between the chemical steps and a local protein conformational change involving the signature-loop residue S607, which may serve a catalytic role similar to an Arg-finger motif in many ATPases and GTPases in stabilizing the phosphoryl-transfer transition state.
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Yadav, Navneet K., et Arnab Samanta. « The stability of compressible swirling pipe flows with density stratification ». Journal of Fluid Mechanics 823 (23 juin 2017) : 689–715. http://dx.doi.org/10.1017/jfm.2017.335.
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We investigate the spatial stability of compressible, viscous pipe flows with radius-dependent mean density profiles, subjected to solid body rotations. For a fixed Rossby number $\unicode[STIX]{x1D716}$ (inverse of the rotational speed), as the Reynolds number $Re$ is increased, the flow transitions from being stable to convectively unstable, usually leading to absolute instability. If flow compressibility is unimportant and $Re$ is held constant, there appears to be a maximum $Re$ below which the flow remains stable irrespective of any rotational speed, or a minimum azimuthal Reynolds number $Re_{\unicode[STIX]{x1D703}}$ $(=Re/\unicode[STIX]{x1D716})$ is required for any occurrence of absolute instabilities. Once compressible forces are significant, the effect of pressure–density coupling is found to be more severe below a critical $Re$, where as rotational speeds are raised, a stable flow almost directly transitions to an absolutely unstable state. This happens at a critical $Re_{\unicode[STIX]{x1D703}}$ which reduces with increased flow Mach number, pointing to compressibility aiding in the instability at these lower Reynolds numbers. However, at higher $Re$, above the critical value, the traditional stabilizing role of compressibility is recovered if mean density stratification exists, where the gradients of density play an equally important role, more so at the higher azimuthal modes. A total disturbance energy-based formulation is used to obtain mechanistic understanding at these stability states, where we find the entropic energy perturbations to dominate as the primary instability mechanism, in sharp contrast to the energy due to axial shear, known to play a leading role in incompressible swirling flows.
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Kocaoglu, Murat, Alexandros Dimakis, Sriram Vishwanath et Babak Hassibi. « Entropic Causal Inference ». Proceedings of the AAAI Conference on Artificial Intelligence 31, no 1 (12 février 2017). http://dx.doi.org/10.1609/aaai.v31i1.10674.
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We consider the problem of identifying the causal direction between two discrete random variables using observational data. Unlike previous work, we keep the most general functional model but make an assumption on the unobserved exogenous variable: Inspired by Occam's razor, we assume that the exogenous variable is simple in the true causal direction. We quantify simplicity using Renyi entropy. Our main result is that, under natural assumptions, if the exogenous variable has low H0 entropy (cardinality) in the true direction, it must have high H0 entropy in the wrong direction. We establish several algorithmic hardness results about estimating the minimum entropy exogenous variable. We show that the problem of finding the exogenous variable with minimum H1 entropy (Shannon Entropy) is equivalent to the problem of finding minimum joint entropy given n marginal distributions, also known as minimum entropy coupling problem. We propose an efficient greedy algorithm for the minimum entropy coupling problem, that for n=2 provably finds a local optimum. This gives a greedy algorithm for finding the exogenous variable with minimum Shannon entropy. Our greedy entropy-based causal inference algorithm has similar performance to the state of the art additive noise models in real datasets. One advantage of our approach is that we make no use of the values of random variables but only their distributions. Our method can therefore be used for causal inference for both ordinal and also categorical data, unlike additive noise models.
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Durrani, Zahid Ali Khan, Faris Abualnaja et Mervyn E. Jones. « Room temperature Szilard cycle and entropy exchange at the Landauer limit in a dopant atom double quantum dot silicon transistor ». Journal of Physics D : Applied Physics, 12 avril 2022. http://dx.doi.org/10.1088/1361-6463/ac66a8.
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Abstract Room-temperature (RT) thermodynamics of a dopant-atom double quantum dot (DQD) silicon transistor are extracted using measurements of the dual gate charge stability diagram. Current traces corresponding to electron exchange in the Szilard one-electron gas ‘Maxwell Demon’ thermodynamic cycle are determined. Theoretical analysis, based on energy state shifts within the generalised DQD charge stability diagram, is used to map the Szilard cycle entropy exchange to the stability diagram. The restriction on the inter-QD coupling energy Em > kT, necessary to observe DQD operation, is inherently seen to satisfy the Landauer limit, kTln2, for the minimum energy consumption per cycle for 1 bit. Associated entropy flows are extracted and simulated using single-electron Monte Carlo equivalent circuit simulations, from 4.2 – 290 K. An entropy valley, tending to the Szilard limit minimum of -kln2, occurs at degeneracy between neighbouring electron states, with traces persisting to RT. Changes in gate cycle trajectory, device capacitance, and temperature are characterised to establish conditions for RT operation.
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Asadollahzadeh, Mehdi, Rezvan Torkaman et Meisam Torab-Mostaedi. « Coupling minimum cross-entropy model with experimental data to determine the drop size distribution for lanthanum extraction in ARDC column ». Separation Science and Technology, 26 avril 2020, 1–13. http://dx.doi.org/10.1080/01496395.2020.1754429.
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Zemani, Farah, et Amina Sabeur. « Computational Fluid Dynamics-Based Analysis of Entropy Generation on Laminar Natural Convection in Enclosures With Partitioned Walls and for Different Heating Positions ». Journal of Heat Transfer 144, no 6 (5 avril 2022). http://dx.doi.org/10.1115/1.4053938.
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Abstract A numerical investigation is performed to analyze air's steady natural convection phenomena in an enclosure with partial active sidewalls. A partition is attached to the hot wall for different active locations to study the effect of the partition position on the heat transfer. First, a finite volume method solves the coupled equations of continuity, momentum, and energy. The SIMPLE algorithm is used to solve the pressure velocities coupling iteratively. Second, based on the obtained dimensionless velocity and temperature values, the distributions of the local entropy generation due to heat transfer and fluid friction and the total entropy generation are determined for different parameters. The results are presented graphically in streamlines, isotherms, and average Nusselt numbers. Three different configurations of active region arrangement are considered in this study, while the partition length has been changed. In order to identify the optimum location of the partition for better heat transfer, the effect of entropy generation has been studied. The heat transfer rate decreases with the increased partition length, especially for l = L/2. Thus, the maximum average Nusselt number occurs for the middle–middle arrangement, while the minimum one occurs for the bottom–bottom arrangement. The numerical investigations in this analysis are made over a wide range of parameters, Rayleigh number 103 to 105, dimensionless partitions length (l = L/8, L/4, L/2), and irreversibility coefficients 10−4< ϕ < 10−2; however, the Prandtl numbers was fixed to 0.71.
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Zhang, Weiming, Fu-Zhi Dai, Huimin Xiang, Biao Zhao, Xiaohui Wang, Na Ni, Rajamallu Karre, Shijiang Wu et Yanchun Zhou. « Enabling highly efficient and broadband electromagnetic wave absorption by tuning impedance match in high-entropy transition metal diborides (HE TMB2) ». Journal of Advanced Ceramics, 16 septembre 2021. http://dx.doi.org/10.1007/s40145-021-0505-y.
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AbstractThe advance in communication technology has triggered worldwide concern on electromagnetic wave pollution. To cope with this challenge, exploring high-performance electromagnetic (EM) wave absorbing materials with dielectric and magnetic losses coupling is urgently required. Of the EM wave absorbers, transition metal diborides (TMB2) possess excellent dielectric loss capability. However, akin to other single dielectric materials, poor impedance match leads to inferior performance. High-entropy engineering is expected to be effective in tailoring the balance between dielectric and magnetic losses through compositional design. Herein, three HE TMB2 powders with nominal equimolar TM including HE TMB2-1 (TM = Zr, Hf, Nb, Ta), HE TMB2-2 (TM = Ti, Zr, Hf, Nb, Ta), and HE TMB2-3 (TM = Cr, Zr, Hf, Nb, Ta) have been designed and prepared by one-step boro/carbothermal reduction. As a result of synergistic effects of strong attenuation capability and impedance match, HE TMB2-1 shows much improved performance with the optimal minimum reflection loss (RLmin) of −59.6 dB (8.48 GHz, 2.68 mm) and effective absorption bandwidth (EAB) of 7.6 GHz (2.3 mm). Most impressively, incorporating Cr in HE TMB2-3 greatly improves the impedance match over 1–18 GHz, thus achieving the RLmin of −56.2 dB (8.48 GHz, 2.63 mm) and the EAB of 11.0 GHz (2.2 mm), which is superior to most other EM wave absorbing materials. This work reveals that constructing high-entropy compounds, especially by incorporating magnetic elements, is effectual in tailoring the impedance match for highly conductive compounds, i.e., tuning electrical conductivity and boosting magnetic loss to realize highly efficient and broadband EM wave absorption with dielectric and magnetic coupling in single-phase materials.
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Yuan, Jiahang, Yun Li, Xinggang Luo, Lingfei Li, Zhongliang Zhang et Cunbin Li. « Regional integrated energy system schemes selection based on risk expectation and Mahalanobis-Taguchi system ». Journal of Intelligent & ; Fuzzy Systems, 31 mai 2021, 1–18. http://dx.doi.org/10.3233/jifs-190211.
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Regional integrated energy system (RIES) provides a platform for coupling utilization of multi-energy and makes various energy demand from client possible. The suitable RIES composition scheme will upgrade energy structure and improve integrated energy utilization efficiency. Based on a RIES construction project in Jiangsu province, this paper proposes a new multi criteria decision-making (MCDM) method for the selection of RIES schemes. Because that subjective evaluation on RIES schemes benefit under criteria has uncertainty and hesitancy, intuitionistic trapezoidal fuzzy number (ITFN) which has the better capability to model ill-known quantities is presented. In consideration of risk attitude and interdependency of criteria, a new decision model with risk coefficients, Mahalanobis-Taguchi system and Choquet integral is proposed. Firstly, the decision matrices given by experts are normalized, and then are transformed to minimum expectation matrices according to different risk coefficients. Secondly, the weights of criteria from different experts are calculated by Mahalanobis-Taguchi system. Mobius transformation coefficients based on interaction degree are to calculate 2-order additive fuzzy measures, and then the comprehensive weights of criteria are obtained by fuzzy measures and Choquet integral. Thirdly, based on group decision consensus requirement, the weights of experts are obtained by the maximum entropy and grey correlation. Fourthly, the minimum expectation matrices are aggregated by the intuitionistic trapezoidal fuzzy Bonferroni mean operator. Thus, the ranking result according to the comparison rules using the minimum expectation and the maximum expectation is obtained. Finally, an illustrative example is taken in the present study to make the proposed method comprehensible.
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Liu, Di, Xiaoting Liu, Jing Li et Pengfei Xu. « Probabilistic Response and Performance Predict of Nonlinear Vibration Energy Harvesting Systems Based on Partial Information ». Journal of Nonlinear Mathematical Physics, 2 mars 2022. http://dx.doi.org/10.1007/s44198-022-00040-1.
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AbstractVibration energy harvesting technology is a hotspot research area in energy harvesting technology because it can convert the vibrational energy in the environment into electrical energy for output and thus provide the distributed energy for microelectromechanical systems. To improve the energy harvesting performance of the vibration energy harvesting system with partial information, we analyzed the probabilistic response of the stochastic system excited by Gaussian white noise under different geometric structures and effectively predicted the corresponding energy harvesting performance. Firstly, we established the coupling moment equation of the vibration energy harvesting system with the cumulant truncation method and then obtained some high-order moments. Then, the probability density function of the stationary response was set in exponential form with unknown parameters by using the maximum entropy principle, and those the unknown parameters will be obtained by solving the minimum value of an objective function, which contains the obtained moment information. Finally, the effects of the physical parameters (including geometric structure parameters and Gaussian white noise) on the dynamic behavior of the vibration energy harvesting system with only partial information have been studied and verified all results by direct numerical simulation.
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Siyu, Li, Bian Kai, Han Guilei, Liu Bo, Chen Xi, Sun Hui, Yang Hao et Chang Junbin. « Study on water inrush warning information of coal seam floor fault structure ». Energy Exploration & ; Exploitation, 9 février 2023, 014459872311559. http://dx.doi.org/10.1177/01445987231155980.
Texte intégralRésumé :
Water inrush from coal floor is a gradual process from generation, and development to disaster. In this process, the geophysical information received by the rock mass will show measurable characteristics of the sudden, and the occurrence of water inrush is the inevitable reflection of various characteristics of the sudden in the limit state. In order to study the early warning information before water inrush in working face, based on the fluid-solid coupling theory, similar simulation test and FLAC3D simulation were used to reproduce the water inrush process of the floor fracture structure, to clarify the difference of response characteristics of each physical quantity before and after water inrush, and to calculate the weight value of different physical quantities in the water inrush process combined with entropy method. The results show that when the working face is gradually approaching the penetrating fault, the stress at the water inrush position of the floor rock layer decreases sharply, and the step jump change occurs after reaching the minimum peak value. The water flow shows a stable increase–sudden increase process. Water inrush through fault location water flow presents increasing—stability—the changing process of surge, water pressure appears cliff-like drop. In the sub-emergent stage when water inrush is about to occur in the working face, the variation range of stress and water pressure at the position of water inrush is more intense. The increase rate of stress at the position of water inrush in the floor rock layer increases sharply and reaches the peak value in a short time, while the increase rate of water pressure at the position of water inrush through the fault decreases.