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51.
In the theory of classical mechanics, the two-body central forcing problem is formulated as a system of the coupled nonlinear
second-order deterministic differential equations. The uncertainty introduced by the small, unmodeled stochastic acceleration
is not assumed in the particle dynamics. The small, unmodeled stochastic acceleration produces an additional random force
on a particle. Estimation algorithms for a two-body dynamics, without introducing the stochastic perturbation, may cause inaccurate
estimation of a particle trajectory. Specifically, this paper examines the effect of the stochastic acceleration on the motion
of the orbiting particle, and subsequently, the stochastic estimation algorithm is developed by deriving the evolutions of
conditional means and conditional variances for estimating the states of the particle-earth system. The theory of the nonlinear
filter of this paper is developed using the Kolmogorov forward equation “between the observations" and a functional difference
equation for the conditional probability density “at the observation." The effectiveness of the nonlinear filter is examined
on the basis of its ability to preserve perturbation effect felt by the orbiting particle and the signal-to-noise ratio. The Kolmogorov forward equation, however, is not appropriate for the numerical simulations, since it is the equation for
the evolution of “the conditional probability density." Instead of the Kolmogorov equation, one derives the evolutions for
the moments of the state vector, which in our case consists of positions and velocities of the orbiting body. Even these equations
are not appropriate for the numerical implementations, since they are not closed in the sense that computing the evolution
of a given moment involves the knowledge of higher order moments. Hence, we consider the approximations to these moment evolution
equations. This paper makes a connection between classical mechanics, statistical mechanics and the theory of the nonlinear
stochastic filtering. The results of this paper will be of use to astrophysicists, engineers and applied mathematicians, who
are interested in applications of the nonlinear filtering theory to the problems of celestial and satellite mechanics. Simulation
results are introduced to demonstrate the usefulness of an analytic theory developed, in this paper. 相似文献
52.
The effect of density inversion on transient natural convection heat transfer of cold water in a square cavity with partially
active vertical walls is studied numerically. The governing equations are solved by control volume method with power law scheme.
In the hot location the temperature is varied sinusoidally and in the cold location uniform temperature is maintained. Nine
different positions of the active zones are considered. Results are discussed for various values of the amplitude, period
and different Grashof numbers and presented graphically in the form of isotherms, streamlines, mid-height velocity profile
and average Nusselt number. It is found that density inversion of water affects natural convection flow and heat transfer.
Heat transfer rate is enhanced upto 80% when the heating location is in the middle of the hot wall. 相似文献
53.
In the United States, the NATO Reference Mobility Model (NRMM) has been used for evaluating military ground vehicle mobility and the Vehicle Cone Index (VCI) has been selected as a mobility metric. VCI represents the minimum soil strength required for a vehicle to consistently make a specific number of passes, usually one or fifty passes. In the United Kingdom, the Mean Maximum Pressure (MMP) has been adopted as a metric for assessing military vehicle cross-country mobility. MMP is the mean value of the maxima occurring under all the wheel stations of a vehicle. Both VCI and MMP are empirically based. This paper presents a review of the basis upon which VCI and MMP were developed, as well as their applications to evaluating vehicle mobility in practice. With the progress in terramechanics and in modelling and simulation techniques in recent years, there is a growing desire to develop physics-based mobility metrics for next generation vehicle mobility models. Based on the review, criteria for selecting physics-based mobility metrics are proposed. Following these criteria, metrics for characterizing military vehicle traction limits and traversability on a given operating area are recommended. 相似文献
54.
Mario Wolf Alexey Rybakov Richard Hinterding Armin Feldhoff 《Entropy (Basel, Switzerland)》2020,22(11)
Besides the material research in the field of thermoelectrics, the way from a material to a functional thermoelectric (TE) module comes alongside additional challenges. Thus, comprehension and optimization of the properties and the design of a TE module are important tasks. In this work, different geometry optimization strategies to reach maximum power output or maximum conversion efficiency are applied and the resulting performances of various modules and respective materials are analyzed. A Bi2Te3-based module, a half-Heusler-based module, and an oxide-based module are characterized via FEM simulations. By this, a deviation of optimum power output and optimum conversion efficiency in dependence of the diversity of thermoelectric materials is found. Additionally, for all modules, the respective fluxes of entropy and charge as well as the corresponding fluxes of thermal and electrical energy within the thermolegs are shown. The full understanding and enhancement of the performance of a TE module may be further improved. 相似文献
55.
Isyaku Muhammad Xingang Wang Changyou Li Mingming Yan Miaoxin Chang 《Entropy (Basel, Switzerland)》2020,22(11)
This paper discussed the estimation of stress-strength reliability parameter based on complete samples when the stress-strength are two independent Poisson half logistic random variables (PHLD). We have addressed the estimation of R in the general case and when the scale parameter is common. The classical and Bayesian estimation (BE) techniques of R are studied. The maximum likelihood estimator (MLE) and its asymptotic distributions are obtained; an approximate asymptotic confidence interval of R is computed using the asymptotic distribution. The non-parametric percentile bootstrap and student’s bootstrap confidence interval of R are discussed. The Bayes estimators of R are computed using a gamma prior and discussed under various loss functions such as the square error loss function (SEL), absolute error loss function (AEL), linear exponential error loss function (LINEX), generalized entropy error loss function (GEL) and maximum a posteriori (MAP). The Metropolis–Hastings algorithm is used to estimate the posterior distributions of the estimators of R. The highest posterior density (HPD) credible interval is constructed based on the SEL. Monte Carlo simulations are used to numerically analyze the performance of the MLE and Bayes estimators, the results were quite satisfactory based on their mean square error (MSE) and confidence interval. Finally, we used two real data studies to demonstrate the performance of the proposed estimation techniques in practice and to illustrate how PHLD is a good candidate in reliability studies. 相似文献
56.
Ademir Hujdurović 《Journal of Graph Theory》2020,95(4):543-564
A clique (resp, independent set) in a graph is strong if it intersects every maximal independent set (resp, every maximal clique). A graph is clique intersect stable set (CIS) if all of its maximal cliques are strong and localizable if it admits a partition of its vertex set into strong cliques. In this paper we prove that a clique in a vertex-transitive graph is strong if and only if for every maximal independent set of . On the basis of this result we prove that a vertex-transitive graph is CIS if and only if it admits a strong clique and a strong independent set. We classify all vertex-transitive graphs of valency at most 4 admitting a strong clique, and give a partial characterization of 5-valent vertex-transitive graphs admitting a strong clique. Our results imply that every vertex-transitive graph of valency at most 5 that admits a strong clique is localizable. We answer an open question by providing an example of a vertex-transitive CIS graph which is not localizable. 相似文献
57.
By deriving the explicit expression of the probability density function (p.d.f.), this paper presents a statistical analysis of the power-level-difference-based dual-channel post-filter (PLD-DCPF) estimator. The derivation is based on the joint p.d.f. of the auto-spectra of a two-dimensional stationary Gaussian process with mean zero, where the theoretical expression is verified by numerical simulations. Using this theoretical p.d.f. expression, this paper studies the impacts of the correlative parameters on the amount of noise reduction and speech distortion. According to both the theoretical analysis results and the simulation results, four schemes are proposed to improve the performance of the traditional PLD-DCPF estimator. 相似文献
58.
59.
Meena Kumari Upendra Kumar Singh Abbul Bashar Khan Maqsood Ahmad Malik 《Journal of Dispersion Science and Technology》2018,39(10):1462-1468
The effect of bovine serum albumin on the surface properties of IL-type gemini surfactant ([C10-4-C10im]Br2), have been investigated by surface tension method. The critical micelle concentration (CMC) as a function of BSA concentrations at various temperatures was investigated. The CMC of [C10-4-C10im]Br2 increases with increasing the concentration of BSA as well as the temperature of the system. The interfacial parameters viz; maximum surface excess concentration (Γmax), the minimum area per molecule (Amin), and surface pressure at CMC (Πcmc) were calculated. In addition, thermodynamic parameters of adsorption and micellization were evaluated by using surface tension data. The results indicated that the binding of [C10-4-C10im]Br2 to BSA is spontaneous and exothermic in nature. The process is entropy driven and hydrophobic interactions are the major driving forces. 相似文献
60.
In this paper, the a posteriori error estimates of Chebyshev–Petrov–Galerkin approximations are investigated. For simplicity, we choose the Poisson equation with Dirichlet boundary conditions to discuss the a posteriori error estimators, and deduce their efficient and reliable properties. Some numerical experiments are performed to verify the theoretical analysis for the a posteriori error estimators. 相似文献