Experimental Study on Flow and Sediment Movement in Cavity Circulations

This paper reports a flume experiment of flow and sediment movement in a cavity. The flow velocity, sediment concentration and the mechanism of hydraulic sorting in the circulation flow are discussed. The quantity and patterns of sediment deposition in the circulation area are studied as well.

Gust-Induced Movement of Dusts Suspended in Atmosphere

在气固两相流的单向耦合模型框架下,研究大气悬浮沙尘在阵风作用下的运动轨迹及其随大气风速、沙尘粒径的变化,揭示了在Stokes阻力、Saffman力和重力共同作用下,沙尘悬移可能转换为跃移的现象。

Experimental Investigation Of Particle Velocity Distributions In Windblown Sand Movement

With the PDPA (Phase Doppler Particle Analyzer) measurement technology, the probability distributions of particle impact and lift-off velocities on bed surface and the particle velocity distributions at different heights are detected in a wind tunnel. The results show that the probability distribution of impact and lift-off velocities of sand grains can be expressed by a log-normal function, and that of impact and lift-off angles complies with an exponential function. The mean impact angle is between 28 degrees and 39 degrees, and the mean lift-off angle ranges from 30 degrees to 44 degrees. The mean lift-off velocity is 0.81-0.9 times the mean impact velocity. The proportion of backward-impacting particles is 0.05-0.11, and that of backward-entrained particles ranges from 0.04 to 0.13. The probability distribution of particle horizontal velocity at 4 mm height is positive skew, the horizontal velocity of particles at 20 mm height varies widely, and the variation of the particle horizontal velocity at 80 mm height is less than that at 20 mm height. The probability distribution of particle vertical velocity at different heights can be described as a normal function.

Statistical analysis of synthetic earthquake catalogs generated by models with various levels of fault zone disorder

The stress release model, a stochastic version of the elastic rebound theory, is applied to the large events from four synthetic earthquake catalogs generated by models with various levels of disorder in distribution of fault zone strength (Ben-Zion, 1996) They include models with uniform properties (U), a Parkfield-type asperity (A), fractal brittle properties (F), and multi-size-scale heterogeneities (M). The results show that the degree of regularity or predictability in the assumed fault properties, based on both the Akaike information criterion and simulations, follows the order U, F, A, and M, which is in good agreement with that obtained by pattern recognition techniques applied to the full set of synthetic data. Data simulated from the best fitting stress release models reproduce, both visually and in distributional terms, the main features of the original catalogs. The differences in character and the quality of prediction between the four cases are shown to be dependent on two main aspects: the parameter controlling the sensitivity to departures from the mean stress level and the frequency-magnitude distribution, which differs substantially between the four cases. In particular, it is shown that the predictability of the data is strongly affected by the form of frequency-magnitude distribution, being greatly reduced if a pure Gutenburg-Richter form is assumed to hold out to high magnitudes.

A model experiment of the plate movement

Detailed analysis of some difficult aspects has been made from modeling the platemovement. A new method of using differential density of material (instead of differentialtemperature) has been developed in the experiments. The effect of convection of mantleon the plate movement has been studied using a centrifugal technique, and a patternshowing the recurrence of the plate movement has been successfully obtained. In this paper, a criterion De=Dm is presented for the similarity of the model to thecounterpart of the original mantle. According to the criterion, what happens in the modelin a span of ten minutes suggests a process of the "original model" going on in geologi-cal time of three million years.

Displacive To Order-Disorder Two-Step Phase Transition Model For Para-Ferroelectric Transition

Two-step phase transition model, displacive to order-disorder, is proposed. The driving forces for these two transitions are fundamentally different. The displacive phase transition is one type of the structural phase transitions. We clearly define the structural phase transition as the symmetry broking of the unit cell and the electric dipole starts to form in the unit cell. Then the dipole-dipole interaction takes place as soon as the dipoles in unit cells are formed. We believe that the dipole-dipole interaction may cause an order-disorder phase transition following the displacive phase transition. Both structural and order-disorder phase transition can be first-order or second-order or in between. We found that the structural transition temperatures can be lower or equal or higher than the order-disorder transition temperature. The para-ferroelectric phase transition is the combination of the displacive and order-disorder phase transitions. It generates a variety of transition configurations along with confusions. In this paper, we discuss all these configurations using our displacive to order-disorder two-step phase transition model and clarified all the confusions.

Attention deficit/hyperactivity disorder children with a 7-repeat allele of the dopamine receptor D4 gene have extreme behavior but normal performance on critical neuropsychological tests of attention

An association of the dopamine receptor D4 (DRD4) gene located on chromosome 11p15.5 and attention deficit/hyperactivity disorder (ADHD) has been demonstrated and replicated by multiple investigators. A specific allele [the 7-repeat of a 48-bp variable number of tandem repeats (VNTR) in exon 3] has been proposed as an etiological factor in attentional deficits manifested in some children diagnosed with this disorder. In the current study, we evaluated ADHD subgroups defined by the presence or absence of the 7-repeat allele of the DRD4 gene, using neuropsychological tests with reaction time measures designed to probe attentional networks with neuroanatomical foci in D4-rich brain regions. Despite the same severity of symptoms on parent and teacher ratings for the ADHD subgroups, the average reaction times of the 7-present subgroup showed normal speed and variability of response whereas the average reaction times of the 7-absent subgroup showed the expected abnormalities (slow and variable responses). This was opposite the primary prediction of the study. The 7-present subgroup seemed to be free of some of the neuropsychological abnormalities thought to characterize ADHD.

Spatially directed movement and neuronal activity in freely moving monkey

The abilities to plan a series of movements and to navigate within the environment require the functions of the frontal and ventromedial temporal lobes, respectively. Neuropsychological studies posit the existence of egocentric (prefrontal) and allocentri

Prefrontal white matter abnormalities in young adult with major depressive disorder: A diffusion tensor imaging study

Prefrontal impairments have been hypothesized to be most strongly associated with the cognitive and emotional dysfunction in depression. Recently, white matter microstructural abnormalities in prefrontal lobe have been reported in elderly patients with ma

Effect of disorder on self-collimated beam in photonic crystal

We report a numerical analysis of various types of disorder effects on self-collimated beam in two-dimensional photonic crystal. Finite-difference time-domain (FDTD) method is used to simulate the process by using a pulse propagation technique. The position disorders along the directions parallel and perpendicular to the incidence are considered. We show that random disorder along the perpendicular direction will have a lesser effect on the performance of the dispersion waveguides than those along the parallel direction. Furthermore, the self-collimation waveguide (SCW) has new characteristics when compared with the photonic crystal line defect waveguide. (c) 2006 Elsevier B.V. All rights reserved.