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The Size Distribution and Mass-Weighted Terminal Velocity of Low-Latitude Tropopause Cirrus Crystal Populations

JOURNAL OF THE ATMOSPHERIC SCIENCES 2009年第7期66卷 2013-2028页

作者： Schmitt, C. G. Heymsfield, A. J. Natl Ctr Atmospher Res Boulder CO 80307 USA

Ice crystal terminal velocities govern the lifetime of radiatively complex, climatologically important, low-latitude tropopause cirrus clouds. To better understand cloud lifetimes, the terminal velocities of low-latitude tropopause cirrus cloud particles have been estimated using data from aircraft field campaigns. Data used in this study were collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) and the Pre-Aura Validation Experiment (Pre-AVE). Particle properties were measured with the NCAR video ice particle sampler (VIPS) probe, thus providing information about particles in a poorly understood size range. Data used in this study were limited to high-altitude nonconvective thin clouds with temperatures between -56 degrees and -86 degrees C. Realistic particle terminal velocity estimates require accurate values of particle projected area and mass. Exponential functions were used to predict the dimensional properties of ice particles smaller than 200 microns and were found to predict ice water content measurements well when compared to power-law representations. The shapes of the particle size distributions were found to be monomodal and were well represented by exponential or gamma functions. Incorporating these findings into terminal velocity calculations led to lower values of mass-weighted terminal velocities for particle populations than are currently predicted for low-latitude ice clouds. New parameterizations for individual particle properties as well as particle size distribution properties are presented and compared to commonly used parameterizations. Results from this study are appropriate for use in estimating the properties of low-latitude thin and subvisible cirrus at temperatures lower than -56 degrees C.

关键词： TROPOPAUSE MIDDLE atmosphere CIRRUS clouds logarithmic functions CLIMATOLOGY

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Expressing uniformity via oracles

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THEORY OF COMPUTING SYSTEMS 1997年第4期30卷 355-366页

作者： Damm, C Holzer, M Rossmanith, P TECH UNIV MUNICH FAK INFORMAT D-80290 MUNICH GERMANY

We study under what circumstances different uniformity notions for Boolean circuits of logarithmic depth lead to the same complexity class. Our investigations are based on a characterization of uniformity in terms of oracle access to tally sets that is proved in the present paper: A-uniform circuits of logarithmic depth are of the same computational power as DLOGTIME-uniform circuits of logarithmic depth with oracle access to tally sets in A. This characterization does not only apply to classes A such as logarithmic space or polynomial time, but to all in some sense ''well-behaved'' classes and especially to all standard complexity classes. We present many applications for this characterization, among them upward separations, depth-uniformity tradeoffs, and inclusion-completeness results for tally languages.

关键词： logarithmic functions COMPUTATIONAL complexity

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A mesoscopic simulation study of distributions of droplets in a bifurcating channel

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COMPUTERS & FLUIDS 2006年第8-9期35卷 971-977页

作者： Inoue, Yasuhiro Takagi, Shu Matsumoto, Yoichiro Univ Tokyo Dept Mech Engn Bunkyo Ku Tokyo 1138656 Japan

A transport of a suspension of slightly deformed immiscible droplets in a bifurcating channel is studied by using a mesoscale simulation technique. The distribution of the droplets is represented by the fractional droplet flux into two daughters as a function of the volumetric flow ratio between the daughters. The data obtained in our simulations is compared with theoretical predictions obtained by assuming an exponential function for the distribution for positions of the droplets in the mother channel. The theoretical predictions show good agreement with the simulation results. Further, we compare our results with an experimental study of transports of spherical and disk-shaped particles in a bifurcating channel, and we confirm that our results show the same tendency towards non-linearity as the experimental result do. A non-uniform distribution of the droplets in the mother channel affects the non-linear separation of the droplet flux at the bifurcation. (C) 2005 Elsevier Ltd. All rights reserved.

关键词： SIMULATION methods & models logarithmic functions PROBABILITY theory OPERATIONS research

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Squeezed vacuum as a universal quantum probe

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PHYSICS LETTERS A 2009年第10期373卷 934-939页

作者： Gaiba, Roberto Paris, Matteo G. A. Univ Milan Dipartimento Fis I-20133 Milan Italy Univ Milan CNISM Udr I-20133 Milan Italy Inst Sci Interchange Fdn I-10133 Turin Italy

We address local quantum estimation of bilinear Hamiltonians probed by Gaussian states. We evaluate the relevant quantum Fisher information (QFI) and derive the ultimate bound on precision. Upon maximizing the QFI we found that single- and two-mode squeezed vacuum represent an optimal and universal class of probe states, achieving the so-called Heisenberg limit to precision in terms of the overall energy of the probe. We explicitly obtain the optimal observable based on the symmetric logarithmic derivative and also found that homodyne detection assisted by Bayesian analysis may achieve estimation of squeezing with near-optimal sensitivity in any working regime. (C) 2009 Elsevier B.V. All rights reserved.

关键词： QUANTUM theory RESEARCH SQUEEZED light ESTIMATION theory VECTOR analysis HAMILTONIAN systems BAYESIAN analysis SENSITIVITY theory (Mathematics) logarithmic functions

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A New Filled Function Method with One Parameter for Global Optimization

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-12页

作者： Wei, Fei Wang, Yuping Xidian Univ Sch Comp Sci & Technol Xian 710071 Peoples R China

The filled function method is an effective approach to find the global minimizer of multidimensional multimodal functions. The conventional filled functions are numerically unstable due to exponential or logarithmic term and sensitive to parameters. In this paper, a new filled function with only one parameter is proposed, which is continuously differentiable and proved to satisfy all conditions of the filled function definition. Moreover, this filled function is not sensitive to parameter, and the overflow can not happen for this function. Based on these, a new filled function method is proposed, and it is numerically stable to the initial point and the parameter variable. The computer simulations indicate that the proposed filled function method is efficient and effective.

关键词： functions (Mathematics) MATHEMATICAL optimization PARAMETER estimation GLOBAL optimization logarithmic functions NUMERICAL analysis SIMULATION methods & models

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A dynamic slip boundary condition for wall-modeled large-eddy simulation

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PHYSICS OF FLUIDS 2014年第1期26卷 1-18页

作者： Bose, S. T. Moin, P. Cascade Technol Inc Palo Alto CA 94303 USA Stanford Univ Ctr Turbulence Res Stanford CA 94305 USA

Wall models for large-eddy simulation (LES) are a necessity to remove the prohibitive resolution requirements of near-wall turbulence in high Reynolds turbulent flows. Traditional wall models often rely on assumptions about the local state of the boundary layer (e.g., logarithmic velocity profiles) and require a priori prescription of tunable model coefficients. In the present study, a slip velocity boundary condition for the filtered velocity field is obtained from the derivation of the LES equations using a differential filter. A dynamic procedure for the local slip length is additionally formulated making the slip velocity wall model free of any a priori specified coefficients. The accuracy of the dynamic slip velocity wall model is tested in a series of turbulent channel flows at varying Reynolds numbers and in the LES of a National Advisory Committee for Aeronautics (NACA) 4412 airfoil at near-stall conditions. The wall-modeled simulations are able to accurately predict mean flow characteristics, including the formation of a trailing-edge separation bubble in NACA 4412 configuration. The validation cases demonstrate the effectiveness of this wall-modeling approach in both attached and separated flow regimes. (C) 2014 AIP Publishing LLC.

关键词： BOUNDARY value problems LARGE eddy simulation models TURBULENT flow REYNOLDS number RESOLUTION (Optics) logarithmic functions

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Long-Time Aftereffects and Relaxation in Piezoelectric Ceramics. 1. Linear Reversible Processes

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FERROELECTRICS 2011年第1期413卷 29-36页

作者： Kuzenko, D. V. Ishchuk, V. M. Bazhin, A. I. Spiridonov, N. A. Natl Acad Sci Ukraine Sci & Technol Ctr Reaktivelektron UA-83096 Donetsk Ukraine Donetsk Natl Univ Dept Phys UA-83055 Donetsk Ukraine

Results of experimental investigation of relaxational aging processes in Pb(Zr, Ti)O-3 based solid solutions after action of DC and AC by electric fields, heating, uniaxial pressure are presented. The said process is long-time and is described by logarithmic function of time. For used in our experiments amplitudes of external excitations process of returning into the initial state is reversible. The criterion of a reversibility is linearly increasing dependence of the speed of a relaxation on amplitude of exciting force. A mechanism of long-time relaxation considering the entrapment of charges, evolved in the annealing process, by vacancies in PZT lattes is suggested.

关键词： PIEZOELECTRIC ceramics RELAXATION phenomena SOLID solutions ELECTRIC fields logarithmic functions ANNEALING of crystals CRYSTAL lattices

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logarithmic ANALOG DIGITAL CONVERTER BASED ON A NON-LINEAR ANALOGUE-TO-DIGITAL CONVERTER

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INTERNATIONAL JOURNAL OF ELECTRONICS 1985年第3期58卷 503-508页

作者： HAFETH, BA ABDULKARIM, MAH University of Baghdad Baghdad Iraq

ABSTRACTABSTRACTThe paper describes a non-linear analogue-to-digital converter (NL-ADC) whose output is proportional to the natural logarithm of the input voltage. It is based on Maclaurin's series of the natural logarithm function. The design is based on voltage-to-frequency conversion (VFC) and a decimal rate multiplier (DRM). The NL-ADC introduces four digital numbers proportional to the first, second, third and fourth powers of the input DC signal. These numbers are digitally added and subtracted according to the first four terms of Maclaurin's series. A microprocessor-controlled hybrid computer with efficient analogue devices is used in the circuit design and implementation.

关键词： Analog-to-digital converters logarithmic functions Taylor's series

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Prediction of a subcooled boiling flow with advanced two-phase flow models

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NUCLEAR ENGINEERING AND DESIGN 2012年 253卷 351-359页

作者： Yun, Byong-Jo Splawski, Andrew Lo, Simon Song, Chul-Hwa Pusan Natl Univ Sch Mech Engn Pusan 609735 South Korea CD Adapco Didcot Oxon England Korea Atom Energy Res Inst Taejon 305353 South Korea

Prediction of bubble size which governs interfacial transfer terms between the two phases is of importance for an accurate prediction of the subcooled boiling flow. In the present work, a mechanistic bubbles size model, S-gamma was examined to enhance the prediction capability of subcooled boiling flows for the CFD (computational fluid dynamics) code. In addition to this, advanced subcooled boiling models such as new wall boiling and two-phase logarithmic wall function models were also applied for an improvement of energy partitioning and two-phase turbulence models, respectively. The benchmark calculation against the DEBORA subcooled boiling data confirms that the S-gamma bubble size model with the two advanced subcooled boiling models shows good prediction results and is applicable to the wide range of flow conditions that are expected in the nominal and postulated accidental conditions of a nuclear power plant. (C) 2011 Elsevier B.V. All rights reserved.

关键词： SUBCOOLED liquids TWO-phase flow COMPUTATIONAL fluid dynamics EBULLITION logarithmic functions PREDICTION theory NUCLEAR power plants -- Accidents

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SCALING LIMITS OF OVERSHOOTING LEVY WALKS

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ACTA PHYSICA POLONICA B 2012年第5期43卷 1111-1132页

作者： Magdziarz, Marcin Teuerle, Marek Zebrowski, Piotr Wroclaw Univ Technol Hugo Steinhaus Ctr Stochast Methods PL-50370 Wroclaw Poland Wroclaw Univ Technol Inst Math & Comp Sci PL-50370 Wroclaw Poland Univ Wroclaw Math Inst PL-50384 Wroclaw Poland

In this paper, we obtain the scaling limits of one-dimensional overshooting Levy walks. We also find the limiting processes for extensions of Levy walks, in which the waiting times and jumps are related by power-law, exponential and logarithmic dependence. We find that limiting processes of overshooting Levy walk are characterized by infinite mean-square-displacement. It also occurs that introducing different dependence between waiting times and jumps of Levy walks results in subdiffusive properties.

关键词： SCALING laws (Statistical physics) LIMITS (Mathematics) POWER law (Mathematics) EXPONENTIAL functions logarithmic functions INFINITE processes MEAN square algorithms

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