The study of the atmospheric boundary layer flow over two-dimensional low-sloped hills under a neutral atmosphere finds numerous applications in meteorology and engineering, such as the development of large-scale atmo...
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The study of the atmospheric boundary layer flow over two-dimensional low-sloped hills under a neutral atmosphere finds numerous applications in meteorology and engineering, such as the development of large-scale atmospheric models, the siting of wind turbines, and the estimation of wind loads on transmission towers and antennas. In this paper, the intermediate variable technique is applied to the momentum equations in streamline coordinates to divide the flow into regions, with each characterized by the dominance of different terms. Using a simple mixing-length turbulence closure, a simplified form of the x momentum equation is solved for the fully turbulent region, resulting in a modified logarithmic law. The solution is expressed as a power series correction to the classical logarithmic law that is valid for flat terrain. A new parameter appears: the effective radius of curvature of the hill. The modified logarithmic law is used to obtain new equations for the speedup, the relative speedup, the maximum speedup, and the height at which it occurs. A new speedup ratio is proposed to calculate the relative speedup at specific heights. The results are in very good agreement with the Askervein and Black Mountain field data.
作者：
V'yugin, VVRussian Acad Sci
Inst Informat Transmiss Problems Moscow 101447 Russia Univ London
Comp Learning Res Ctr Royal Holloway Egham TW20 0EX Surrey England
The problem of existence of predictive complexity for the absolute loss game is studied, Predictive complexity is a generalization of Kolmogorov complexity which bounds the ability of any algorithm to predict elements...
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The problem of existence of predictive complexity for the absolute loss game is studied, Predictive complexity is a generalization of Kolmogorov complexity which bounds the ability of any algorithm to predict elements of a sequence of outcomes. For perfectly mixable loss functions (logarithmic and squared difference are among them) predictive complexity is defined like Kolmogorov complexity to,within an additive constant. The absolute loss function is not perfectly mixable, and the question of existence of the corresponding predictive complexity. which is defined to within an additive constant, is open. We prove that in the case of the absolute loss game the predictive complexity can he defined to within an additive term O(root/n). where n is the length of a Sequence of outcomes, We prove also that in some restricted settings this bound cannot be improved. (C) 2002 Elsevier Science (USA).
The paper presents a fast algorithm to efficiently compute radix-10 logarithm of a decimal number The algorithm uses a 32-bit floating-point arithmetic and is based on a digit-by-digit iterative computation that does ...
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The paper presents a fast algorithm to efficiently compute radix-10 logarithm of a decimal number The algorithm uses a 32-bit floating-point arithmetic and is based on a digit-by-digit iterative computation that does not require look-up tables curve fitting decimal-binary conversion or division operations the number of iterations depends on the precision defined by the user Two numerical examples are shown for the purpose of Illustration The algorithm produces very accurate result with a maximum absolute error of 0 267 x 10(-5) for a 32-bit precision When implemented on to the Xilinx VirtexII FPGA the pipelined architecture costs only 2632 logic cells runs at a maximum frequency of 53 5 MHz and consumes 117 mW of power The design is very suitable for timing and accuracy critical applications and compliant with IEEE754-2008 standard (C) 2010 Elsevier Ltd All rights reserved
The occurrence of logarithmic switchback is studied for ordinary differential equations containing a parameter k which is allowed to take any value in a continuum of real numbers and with boundary conditions imposed a...
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The attenuation of acoustic waves is often in the form exp[-a vertical bar omega vertical bar(b)] with 0 < b <= 2. For b = 2, experiments show negligible dispersion. For b = 1, the variation of the velocity is w...
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The attenuation of acoustic waves is often in the form exp[-a vertical bar omega vertical bar(b)] with 0 < b <= 2. For b = 2, experiments show negligible dispersion. For b = 1, the variation of the velocity is well-fitted by a logarithmic function, and by power functions when b not equal 1. An explanation of theses results has been provided by T. L. Szabo by extensions of the Kramers-Kronig relations. In this paper, we show that a random propagation time leads to similar results. This model explains the loss of power by the existence of noise which cannot be taken into account by the devices. Also, it explains the redshift linked to the wave bandwidth.
Relations describing the velocity and temperature distributions are studied on the basis of an analysis of a large amount of experimental data from investigations of temperature fields in turbulent flow of different m...
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Relations describing the velocity and temperature distributions are studied on the basis of an analysis of a large amount of experimental data from investigations of temperature fields in turbulent flow of different media - air, water (P ae 1) and liquid metal (Pr << 1). It is noted that the use of the coefficients nu(t) and a(t) of turbulent transfer of momentum and heat, respectively, as well as their ratio - the Prandtl number - for the calculation of the heat transfer intensity can lead to significant errors, though in so doing an apparent correspondence is observed between the experimental and computations data expressed in logarithmic coordinates in the form Nu = AE'(Re) or Nu = AE'(Pr), Nu = AE'(Pe). It is concluded that in engineering calculations of heat transfer in turbulent flow it is preferable to use relations based on the velocity and temperature distributions at Pr = const.
In the present work, spinach samples were dried using a pilot-scale cabinet-type convective dryer. Drying experiments were conducted using a constant air velocity of 1.2 m/s and four drying air temperatures of 50, 60,...
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In the present work, spinach samples were dried using a pilot-scale cabinet-type convective dryer. Drying experiments were conducted using a constant air velocity of 1.2 m/s and four drying air temperatures of 50, 60, 70 and 80C. Drying rate increased with the increase in air temperature and thus reduced the drying time. The experimental drying data of spinach were applied to four moisture ratio models, namely, the Henderson and Pabis, Lewis, Page, and logarithmic models. Nonlinear regression analysis was performed to relate the parameters of the model with the drying conditions. The performance of these models is evaluated by comparing the coefficient of determination, R(2), and the reduced chi-square, chi(2), between the observed and predicted moisture ratios. Among all the models, the logarithmic model was found to be the best for explaining the drying characteristics of spinach leaves. The effective moisture diffusivity varied from 6.590 x 10(-10) to 1.927 x 10(-9) m(2) /s over the temperature range studied, with an activation energy of 34.35 kJ/mol for spinach leaves.
We obtain self-similar first-order and second-order rogue wave solutions for the (3+1)-dimensional inhomogeneous nonlinear Schrodinger equation. Based on these solutions, we investigate the control and manipulation of...
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We obtain self-similar first-order and second-order rogue wave solutions for the (3+1)-dimensional inhomogeneous nonlinear Schrodinger equation. Based on these solutions, we investigate the control and manipulation of rogue waves in the dispersion decreasing fibers with logarithmic profile and Gaussian profile. Our results indicate that the propagation behaviors of rogue waves, such as fast excitation, sustainment and restraint, can be manipulated by modulating the relation between the maximum value of the effective propagation distance Z(m) and the parameter Z(0) relating to the excited types of rogue wave. The comparison of the propagation behavior of rogue wave in the dispersion decreasing waveguides with logarithmic profile, Gaussian profile and hyperbolic profile is also given. (C) 2012 Elsevier Ltd. All rights reserved.
By using the first integral method, the traveling wave solutions for the generalized Pochhammer-Chree (PC) equations are constructed. The obtained results include complex exponential function solutions, complex travel...
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By using the first integral method, the traveling wave solutions for the generalized Pochhammer-Chree (PC) equations are constructed. The obtained results include complex exponential function solutions, complex traveling solitary wave solutions, complex periodic wave solutions, and complex rational function solutions. The power of this manageable method is confirmed.
The quantum trajectory approach is generalized to arbitrary coordinate systems, including curvilinear coordinates. This allows one to perform an approximate quantum trajectory propagation, which scales favorably with ...
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The quantum trajectory approach is generalized to arbitrary coordinate systems, including curvilinear coordinates. This allows one to perform an approximate quantum trajectory propagation, which scales favorably with system size, in the same framework as standard quantum wave packet dynamics. The trajectory formulation is implemented in Jacobi coordinates for a nonrotating triatomic molecule. Wave packet reaction probabilities are computed for the O((3)p) + H-2 -> OH + H reaction using the approximate quantum potential. The latter is defined by the nonclassical component of the momentum operator expanded in terms of linear and exponential functions. Unlike earlier implementations with linear functions, the introduction of the exponential function provides an accurate description of asymptotic dynamics for this system and gives good agreement of approximate reaction probabilities with accurate quantum calculations.
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