Molecular hydrodynamics of the moving contact line in two-phase immiscible flows

The ``no-slip'' boundary condition, i.e., zero fluid velocity relative to the solid at the fluid-solid interface, has been very successful in describing many macroscopic flows. A problem of principle arises when the no-slip boundary condition is used to model the hydrodynamics of immiscible-fluid displacement in the vicinity of the moving contact line, where the interface separating two immiscible fluids intersects the solid wall. Decades ago it was already known that the moving contact line is incompatible with the no-slip boundary condition, since the latter would imply infinite dissipation due to a non-integrable singularity in the stress near the contact line. In this paper we first present an introductory review of the problem. We then present a detailed review of our recent results on the contact-line motion in immiscible two-phase flow, from MD simulations to continuum hydrodynamics calculations. Through extensive MD studies and detailed analysis, we have uncovered the slip boundary condition governing the moving contact line, denoted the generalized Navier boundary condition. We have used this discovery to formulate a continuum hydrodynamic model whose predictions are in remarkable quantitative agreement with the MD simulation results at the molecular level. These results serve to affirm the validity of the generalized Navier boundary condition, as well as to open up the possibility of continuum hydrodynamic calculations of immiscible flows that are physically meaningful at the molecular level.Comment: 36 pages with 33 figure

Hydrodynamic slip boundary condition at chemically patterned surfaces: A continuum deduction from molecular dynamics

We investigate the slip boundary condition for single-phase flow past a chemically patterned surface. Molecular dynamics (MD) simulations show that modulation of fluid-solid interaction along a chemically patterned surface induces a lateral structure in the fluid molecular organization near the surface. Consequently, various forces and stresses in the fluid vary along the patterned surface. Given the presence of these lateral variations, a general scheme is developed to extract hydrodynamic information from MD data. With the help of this scheme, the validity of the Navier slip boundary condition is verified for the chemically patterned surface, where a local slip length can be defined. Based on the MD results, a continuum hydrodynamic model is formulated using the Navier-Stokes equation and the Navier boundary condition, with a slip length varying along the patterned surface. Steady-state velocity fields from continuum calculations are in quantitative agreement with those from MD simulations. It is shown that, when the pattern period is sufficiently small, the solid surface appears to be homogeneous, with an effective slip length that can be controlled by surface patterning. Such a tunable slip length may have important applications in nanofluidics.Comment: 41 pages, 17 figure

The Nonlinear Permittivity Including Non-Abelian Self-interaction of Plasmons in Quark-Gluon Plasma

By decomposing the distribution functions and color field to regular and fluctuation parts, the solution of the semi-classical kinetic equations of quark-gluon plasma is analyzed. Through expanding the kinetic equations of the fluctuation parts to third order, the nonlinear permittivity including the self-interaction of gauge field is obtained and a rough numerical estimate is given out for the important \vk =0 modes of the pure gluon plasma.Comment: 7 pages, shortened version accepted by Chin.Phys.Let

Quantum logical gates with four-level SQUIDs coupled to a superconducting resonator

We propose a way for realizing a two-qubit controlled phase gate with superconducting quantum interference devices (SQUIDs) coupled to a superconducting resonator. In this proposal, the two lowest levels of each SQUID serve as the logical states and two intermediate levels of each SQUID are used for the gate realization. We show that neither adjustment of SQUID level spacings during the gate operation nor uniformity in SQUID parameters is required by this proposal. In addition, this proposal does not require the adiabatic passage or a second-order detuning and thus the gate is much faster.Comment: 6 pages, 3 figure

Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material

Two-dimensional (2D) transition metal dichalcogenide (TMD) nanosheets exhibit remarkable electronic and optical properties. The 2D features, sizable bandgaps, and recent advances in the synthesis, characterization, and device fabrication of the representative MoS$_2$, WS$_2$, WSe$_2$, and MoSe$_2$ TMDs make TMDs very attractive in nanoelectronics and optoelectronics. Similar to graphite and graphene, the atoms within each layer in 2D TMDs are joined together by covalent bonds, while van der Waals interactions keep the layers together. This makes the physical and chemical properties of 2D TMDs layer dependent. In this review, we discuss the basic lattice vibrations of monolayer, multilayer, and bulk TMDs, including high-frequency optical phonons, interlayer shear and layer breathing phonons, the Raman selection rule, layer-number evolution of phonons, multiple phonon replica, and phonons at the edge of the Brillouin zone. The extensive capabilities of Raman spectroscopy in investigating the properties of TMDs are discussed, such as interlayer coupling, spin--orbit splitting, and external perturbations. The interlayer vibrational modes are used in rapid and substrate-free characterization of the layer number of multilayer TMDs and in probing interface coupling in TMD heterostructures. The success of Raman spectroscopy in investigating TMD nanosheets paves the way for experiments on other 2D crystals and related van der Waals heterostructures.Comment: 30 pages, 23 figure

Changes in endogenous hormone concentrations during inflorescence induction and development in pineapple (Ananas comosus cv. Smooth Cayenne) by ethephon

This study investigated the changes of five endogenous hormones in the shoot apex and the white bases of D-leaf during the inflorescence induction and development of ‘Smooth Cayenne’ pineapple, using 14-month-old pot-grown plants as material and ethephon as flower forcing agent. Results showed that application of ethephon increased the level of endogenous ethylene (C2H4), abscisic acid (ABA) and 2-isopentyl adenine (2-iP) while it decreased the concentration of indole-3-acetic acid (IAA), gibberellic acid (GA3) and zeatin (ZT), and led to the transition of vegetative growth to inflorescence initiation. After inflorescence initiation, the contents of C2H4, ABA and 2-iP declined but the contents of IAA, ABA and ZT increased. These results indicated that low levels of IAA, GA3 and ZT and high levels of C2H4, ABA and 2-iP facilitated inflorescence initiation, while high levels of ZT, IAA and GA3 and low levels of C2H4 and ABA facilitated inflorescence development.Key words: Pineapple, inflorescence initiation, inflorescence development, endogenous hormone

The Study of Dynamic Monitor of Rice Drought in Jiangxi Province with Remote Sensing

AbstractMODIS sensor has a high temporal resolution, spectral resolution, and moderate spatial resolution. The data products are widely used in Large-scale and long period dynamic monitoring of drought. This paper focuses on characters of farming rice dominated in Jiangxi province, and analysis on remote sensing monitoring model and drought monitoring indicators which selection the MODIS data products and drought information related from 2000-2008. Established standard for classification of drought in Jiangxi province, and verified instances of 2003 drought in Jiangxi. This study may have a certain significance to agricultural drought monitoring based on rice planting in southern China, because the correspondencematch between the selected TD indices and cloud cover with precipitation and daily maximum temperature evolution curve