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关键词： Linear flow   Flow equivalence   Orbit equivalence   (uniform) core   Kronecker flow  

摘要： New elementary, self-contained proofs are presented for the topological and the smooth classification theorems of linear flows on finite-dimensional normed spaces. The arguments, and the examples that accompany them, highlight the fundamental roles of linearity and smoothness more clearly than does the existing literature.

关键词： Sun   cycles 23 and 24   flares   CMEs   proton events   geomagnetic indices  

摘要： Solar flare activity is characterized by different classification systems, both in optical and X-ray ranges. The most generally accepted classifications of solar flares describe important parameters of flares such as the maximum of brightness of the flare in the optical range - H alpha flare class (change from F to B), area of the flare in H alpha (change from S for areas less than 2 square degrees to 4 for areas more than 24.7 square degrees) and the maximum amplitude of the soft X-ray (SXR)-flux in the band 0.1-0.8 nm (F0.1-0.8max) - X-ray flares of classes from C to X. A new classification parameter of solar flares is proposed here - the X-ray index of flare XI, based on GOES measurements of solar radiation in the SXR-range. The XI-index has a clear physical interpretation associated with the total flare energy in the SXR-range. XI is easily calculated for each flare with the use of available GOES data. The XI-index can be used along with other geoeffective parameters of Solar activity to assess both flares and coronal mass ejections that are connected with them.

标准号: BS ISO 7146-1-2019 - TC

标准号: BS ISO 7146-2-2019 - TC

关键词： Liquid mixing   dispersion coefficient   solid-liquid fluidized bed   solid-liquid circulating fluidized bed   axial dispersion model  

摘要： Liquid phase axial mixing studies have been carried out in the novel solid-liquid circulating fluidized bed (SLCFB). The SLCFB primarily consists of a single multistage column (having an inner diameter of 100 mm i.d. and length of 1.40 m) which is divided into two sections wherein both the steps of utilization, namely loading (e.g., adsorption and catalytic reaction) and regeneration of solid phase, can be carried out simultaneously in continuous mode. Weak base anion exchange resin was used as the solid phase, whereas water as the fluidizing medium. The effects of physical properties of solid phase, superficial liquid velocity, and solid circulation rate on liquid phase axial dispersion coefficient were investigated. The dispersion coefficient increases monotonically with an increase in the size of solid particle, superficial liquid velocity, and solid circulation rate. The axial dispersion model (ADM) was used to model experimental residence time distribution (RTD) data. A good agreement was found between ADM predictions and the experimental measurements. A unified correlation has also been proposed to determine dispersion coefficient as a function of physical properties of solid and liquid phases, superficial liquid velocity, and solid circulation rate based on all previous and present experimental data on multistage SLCFB.

关键词： Dry coal beneficiation   Gas-solid fluidized bed   Spatial characteristics   Separation performance   Regional feeding  

摘要： To study the fluidization characteristics and separation performance of a gas-solid dense-phase fluidized bed, bed space structure and force analyses of particles in the radial and axial zones are explored. The results indicate that the standard deviation and average bed density increases with increases in the static bed height. As the fluidization number is increased, the average bed density decreases and fluctuates drastically. Under the same fluidization number, the density in the upper layer is low with violent fluctuations, and it is relatively lower in middle layer and higher on the side wall. The ratio of the minimum pressure gradients in the axial and radial zones in the fluidized state was 10, which proved that the main movement mode of particles is settlement motion in the axial direction. The probable error values were 0.095 and 0.097 g/cm(3) in optimal test conditions, indicating efficient separation of 13-25 mm coal particles. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Stochastic differential equations   Wong-Zakai approximation   Malliavin calculus  

摘要： We investigate the regularity of the law of Wong-Zakai-type approximations for Ito stochastic differential equations. These approximations solve random differential equations where the diffusion coefficient is Wick-multiplied by the smoothed white noise. Using criteria based on the Malliavin calculus we establish absolute continuity and a Fokker-Planck-type equation solved in the distributional sense by the density. The parabolic smoothing effect typical of the solutions of Ito equations is lacking in this approximated framework;therefore, in order to prove absolute continuity, the initial condition of the random differential equation needs to possess a density itself. (C) 2019 Elsevier Inc. All rights reserved.

关键词： Linear-implicit Crank-Nicolson scheme   Linear-implicit leap-frog scheme   Momentum-preservation   Fourier pseudospectral method  

摘要： We propose two conservative linear-implicit schemes for the space fractional Korteweg- de Vries (fKdV) equation. One is the linear-implicit Crank-Nicolson scheme and the other is the linear-implicit leap-frog scheme. In order to obtain a high order discretization in the space direction, we adopt the Fourier pseudospectral method. The Crank-Nicolson scheme and leap-frog scheme are used for temporal discretization, and those two schemes are efficient in practical computations because of their linear property. Furthermore, we analyse the uniqueness, boundness, convergence of the two schemes. Numerical experiments are presented to validate the theoretical analysis. (C) 2019 Elsevier Inc. All rights reserved.

关键词： Zhundong coal   Oxy-fuel   Ash formation   Sodium and potassium   Density functional theory  

摘要： Zhundong coal is promising to replace inferior coal in fossil-fueled power plants, considering its high abundance, low contents of sulfur and nitrogen. However, the relative high contents of alkalis, especially sodium and potassium, damage the operational economy and safety badly since the release of alkali metals in flue gas can lead to fly ash-related problems such as slagging, ash accumulation and corrosion. Although, oxy-fuel circulating fluidized bed (CFB) combustion is beneficial to reduce the release of sodium and potassium by lowering the operation temperature, the ash formation characteristics of Zhundong coal under the oxy-fuel CFB is still scarce. Our results showed that the residual amounts of sodium and potassium in the ash samples, both tend to decrease with increasing temperature no matter under air combustion or oxy-fuel combustion. However, the sodium content in the cinder obtained under the oxy-fuel combustion atmosphere was higher than that under the air combustion atmosphere, and the insoluble sodium, mainly existed in the form of aluminosilicates, was the main form. In addition, the increase of steam content in both atmospheres reduced the sodium content in the cinder while the residual amount of potassium increased. Density functional theory calculations verified the transformation behavior between sodium and potassium and the inhibiting effect of steam. This study elucidates the release and migration characteristics of sodium and potassium in Zhundong coal both experimentally and theoretically and will benefit the popularity of Zhundong coal.

关键词： 流体包裹体   成矿流体   同位素   矿床成因   塘坝金矿床  

摘要： 塘坝金矿床位于西秦岭金成矿带南部文县—康县金成矿亚带东段,为石英脉型金矿床。野外地质调查发现,矿体主要产于花岗斑岩脉附近的断裂中,在空间上与花岗斑岩脉关系密切,成矿作用可划分为3个阶段。流体包裹体显微测温结果表明:不同阶段成矿流体包裹体类型相近,矿床成矿温度为156.9℃~303.2℃,盐度为1.82%~15.67%,密度为0.76~0.99 g/cm 3,深度为5.18~7.43 km;成矿流体具有中低温度、中低盐度、低密度、中浅成相特征。包裹体激光拉曼光谱分析显示,包裹体气相成分主要为CO 2、H 2O,含少量N 2,液相成分主要为H 2O,属于H 2O-NaCl±CO 2体系。氢-氧-硫同位素分析结果表明,塘坝金矿床δ18 O H 2O为5.98‰~9.87‰,δD V-SMOW为-80.6‰^-74.5‰,δ34 S为-1.9‰~8.0‰;结合矿床野外产出特征,成矿流体主要来源于岩浆热液。综合分析认为,该矿床为与岩浆作用有关的中低温度、中低盐度岩浆期后热液型金矿床。