Additional response: Additional discussion of “Mixed mode ductile fracture using the strain energy density criterion”

boundary-layer flows, the skin friction and wall heat-transfer are higher and the

Asymmetric flow networks

This paper provides a new model of network formation that bridges the gap between the two benchmark models by Bala and Goyal, the one-way flow model, and the two-way flow model, and includes both as particular extreme cases. As in both benchmark models, in what we call an "asymmetric flow" network a link can be initiated unilaterally by any player with any other, and the flow through a link towards the player who supports it is perfect. Unlike those models, in the opposite direction there is friction or decay. When this decay is complete there is no flow and this corresponds to the one-way flow model. The limit case when the decay in the opposite direction (and asymmetry) disappears, corresponds to the two-way flow model. We characterize stable and strictly stable architectures for the whole range of parameters of this "intermediate" and more general model. We also prove the convergence of Bala and Goyal's dynamic model in this context.

含尘大气近地层流底层流动特性及其摩阻系数

采用双向耦合的双流体模型，了大气悬浮沙尘的存在对大气边界层中流底层流动特性及摩阻系数的影响，计算并讨论了不同沙尘含量下含尘大气相对于无尘大气摩阻系数的变化，结果表明，摩阻系数的变化取决于悬浮沙尘的初始运动状态和质量载荷率。

A Multiscale-Domain Decomposition Method for High Reynolds Number Flows

The high Reynolds number flow contains a wide range of length and time scales, and the flow domain can be divided into several sub-domains with different characteristic scales. In some sub-domains, the viscosity dissipation scale can only be considered in a certain direction; in some sub-domains, the viscosity dissipation scales need to be considered in all directions; in some sub-domains, the viscosity dissipation scales are unnecessary to be considered at all. For laminar boundary layer region, the characteristic length scales in the streamwise and normal directions are L and L Re-1/ 2 , respectively. The characteristic length scale and the velocity scale in the outer region of the boundary layer are L and U, respectively. In the neighborhood region of the separated point, the length scale l<friction on the wall are given. The numerical results obtained by the multiscale-domain decomposition algorithm are well agreement with those by NS equations. Comparing with the usual method of solving the Navier-Stokes equations in the whole flow, under the same numerical accuracy, the present multiscale domain decomposition method decreases CPU consuming about 20% and reflects the physical mechanism of practical flow more accurately.

A Study of the Tribological Behavior of Carbon-Nanotube-Reinforced Ultrahigh Molecular Weight Polyethylene Composites

The tribological properties of the high-strength and high-modulus ultrahigh molecular weight polyethylene (UHMWPE) film and the UHMWPE composites reinforced by multiwalled carbon nanotubes (MWCNT/UHMWPE) were investigated using a nanoindenter and atomic force microscope (AFM). The MWCNT/UHMWPE composites films exhibited not only high wear resistance but also a low friction coefficient compared to the pure UHMWPE films. We attribute the high wear resistance to the formation of the new microstructure in the composites due to the addition of MWCNTs.

Experiments about Simple Liquid Flows in Microtubes

The behavior of micro-scale flow is significant for the performance of Micro-Electro-Mechanical- Systems (MEMS) devices. Some experiments about liquid flow through microtubes with diameters about 3similar to20mum are presented here. The liquids used in our experiments include some simple liquids with small molecules, such as non-ion water and several kinds of organic liquids (CCL4, C6H5C2H5 and Isopropanol etc.). The flow rate and the normalized friction cocfficients were measured in micro-flow experimental apparatus. The results show that when the driven pressure varies from 0 to 1Mpa, the flow behaviors in 20mum microtube for both polar and non-polar liquids are in agreement with Hagen-Poiseuille law of the classical theory. It means that N-S equation based on continuous medium still acts well in this case. For higher pressure drop from 1 to 30Mpa, in the microtubes with diameter of 3similar to10mum, the normalized friction coefficients of organic liquids can't keep constant with pressure increases. However the non-ion water reveals different trends.

Currents observed in Panama Bay during September-October 1958

ENGLISH: During the period extending from late August to early October 1958 the United States Navy Hydrographic Office (now the United States Oceanographic Office) undertook a program of current observations in the western part of Panama Bay. The specifications of the survey called for half-hourly monitoring of currents at three depths at each of six locations, one for thirty days and five for five days. Although not all these objectives were realized because of instrument malfunctions and failures, sufficient data were collected at five stations to provide a fairly detailed description of the current pattern as it existed at the times of observation. This report is concerned first with a discussion of those data and the procedures used to reduce them to the tidal and net current components and second, with the effects on the current pattern of tidal amplitude, bottom topography and bottom friction. SPANISH: Durante el período entre fines de agosto y principios de octubre de 1958, la United States Navy Hydrographic Office (ahora la United States Navy Oceanographic Office) tomó a su cargo un programa para observar las corrientes en la parte occidental de la Bahía de Panamá. De acuerdo con las especificaciones del proyecto, las observaciones de las corrientes debían hacerse cada media hora a tres profundidades en cada una de seis localidades; en una de ellas durante treinta días yen las otras cinco durante cinco días. A pesar de que no todos estos objetivos fueron cumplidos a causa del mal funcionamiento y fallas instrumentales, se recogieron suficientes datos en cinco estaciones, como para proporcionar una descripción bastante detallada de la pauta de las corrientes, tal como existía durante las observaciones. Este informe se refiere, primero, al análisis y examen de dichos datos y a los procedimientos empleados para reducir éstos a los componentes de las corrientes netas y a los componentes de las corrientes durante la mareas, y segundo, al efecto que tienen sobre la pauta de las corrientes la fluctuación de las mareas, la topografía del fondo y la fricción del fondo.

Curie Transition Of Nc Nickel By Mechanical Spectroscopy And Magnetization Study

Mechanical spectroscopy measurement is performed to study the internal friction of nanocrystalline ( NC) nickel with an average grain size of 23 nm from room temperature to 610 K. An internal friction peak is observed at about 550 K, which corresponds to the Curie transition process of the NC nickel according to the result of magnetization test. Moreover, the fact that the Curie temperature of NC nickel is lower than that of coarse-grained nickel is explained by an analytical model based on the weakening of cohesive energy.

An Atomistic-Continuum Hybrid Simulation Of Fluid Flows Over Superhydrophobic Surfaces

Recent experiments have found that slip length could be as large as on the order of 1 mu m for fluid flows over superhydrophobic surfaces. Superhydrophobic surfaces can be achieved by patterning roughness on hydrophobic surfaces. In the present paper, an atomistic-continuum hybrid approach is developed to simulate the Couette flows over superhydrophobic surfaces, in which a molecular dynamics simulation is used in a small region near the superhydrophobic surface where the continuum assumption is not valid and the Navier-Stokes equations are used in a large region for bulk flows where the continuum assumption does hold. These two descriptions are coupled using the dynamic coupling model in the overlap region to ensure momentum continuity. The hybrid simulation predicts a superhydrophobic state with large slip lengths, which cannot be obtained by molecular dynamics simulation alone.

Numerical investigation of crack growth in concrete subjected to compression by the generalized beam lattice model

The beam lattice-type models, such as the Euler-Bernoulli (or Timoshenko) beam lattice and the generalized beam (GB) lattice, have been proved very effective in simulating failure processes in concrete and rock due to its simplicity and easy implementation. However, these existing lattice models only take into account tensile failures, so it may be not applicable to simulation of failure behaviors under compressive states. The main aim in this paper is to incorporate Mohr-Coulomb failure criterion, which is widely used in many kinds of materials, into the GB lattice procedure. The improved GB lattice procedure has the capability of modeling both element failures and contact/separation of cracked elements. The numerical examples show its effectiveness in simulating compressive failures. Furthermore, the influences of lateral confinement, friction angle, stiffness of loading platen, inclusion of aggregates on failure processes are respectively analyzed in detail.

An atomistic-continuum hybrid simulation of fluid flows over superhydrophobic surfaces

Recent experiments have found that slip length could be as large as on the order of 1 mu m for fluid flows over superhydrophobic surfaces. Superhydrophobic surfaces can be achieved by patterning roughness on hydrophobic surfaces. In the present paper an atomistic-continuum hybrid approach is developed to simulate the Couette flows over superhydrophobic surfaces in which a molecular dynamics simulation is used in a small region near the superhydrophobic surface where the continuum assumption is not valid and the Navier-Stokes equations are used in a large region for bulk flows where the continuum assumption does hold. These two descriptions are coupled using the dynamic coupling model in the overlap region to ensure momentum continuity. The hybrid simulation predicts a superhydrophobic state with large slip lengths which cannot be obtained by molecular dynamics simulation alone.