低比转数离心泵叶轮出口紊流流动结构分析

在叶轮内三维紊流流动数值计算的基础上 ,从介质能量的观点 ,分析了不同工况下低比转数离心泵叶轮出口处的紊流流动结构。数值计算采用 SIMPL EC算法 ,在贴体坐标系下求解 Navier- Stokes方程 ,紊流模型采用标准的 kε模型。计算结果表明 ,在叶轮的出口附近靠近吸力面一侧存在一个低能区 ,而压力面一侧能量相对较高。这与有关文献中所指出的离心风机的“射流尾流”结构相对应。当偏离设计工况时 ,该低能区的范围和强度略有增加 ,相对应的叶轮效率也降低。计算结果与水泵在这些工况下的效率实验结果相一致 。

半自磨机大型化过程中的相关问题研究

根据半自磨机大型化过程中出现的钢球直接砸衬板、半自磨机单位容积处理量降低以及介质能量传递效率降低的3个问题,通过利用半自磨机钢球运动理论分析和离散元仿真分析相结合的方法,对半自磨机钢球砸衬板现象进行了研究,为避免半自磨机钢球砸衬板选出了合适的转速率和填充率范围,通过仿真分析验证了半自磨机单位容积处理量和介质能量传递效率均随半自磨机筒体直径的增大而降低。

Deriving Energy-Level Gap of a System in Presence of a Kerr-like Medium by Virtue of Invariant Eigen-operator Method

In this paper, we find the invariant eigen-operators （IEOs） and the energy-level gap of a system with a two-level atom interacting with single mode cavity field through multi-photon transition in the presence of a Kerr-like medium. From this work, one can see that the IEO method in many eases is simpler and easier on obtaining the energy-level gap formula than the usual way.

Energy-efficient Medium Access Approach for Wireless Body Area Network Based on Body Posture

Energy efficiency has become one of the most important issues in wireless body area network(WBAN).In this paper,an energy-efficient medium access control(MAC)protocol for WBAN is proposed based on human body posture under walking scenery.Due to person's movements,WBAN is a dynamic network,which means that traditional static protocols are no more suitable for it.For solving this problem,firstly,the feature of human walking at a constant speed is analyzed and we divide a spell of movements into a sequence of key frames just like a video constituted by numbers of continuous frames.As a result,the dynamic walking process is translated into several static postures,which the static MAC protocol could be used for.Secondly,concerning the performance of network lifetime,we design a posture-aware approach for lifetime maximization(PA-DPLM).With analytical and simulation results provided,we demonstrate that PA-DPLM protocol is energy-efficient and can be used under constant speed walking scenery.

Studying of Physical-Mechanical Properties of Rocks of Geological Section Considering the Influences of Recent Geodynamics

The method of determination of elastic moduli of the geological section rocks had been developed in real conditions. The method is based on application of non-classically linearized theory of elastic waves＇ propagation in the deformable media and utilization of neural networks when creating the geoseismic model. It is proposed to forecast the thin-layer model of medium by velocities of the shear waves on the base of seismic inversion of 2D profile by neural networks and geophysical well logging data. The method had been tested on materials of geophysical well logging data and 2D seismic profile related to one of the structures in the South-Caspian depression. The specific results for Poisson coefficient and elastic moduli of the third order had been obtained. The mentioned method can also be applied to forecast of other physical-mechanical properties of the medium.

Analyzing Heat Extraction and Sustainability of EGS with a Novel Model

We investigate the subsurface heat exchange process in EGS （enhanced geothermal systems） with a previously developed novel model. This model treats the porous heat reservoir as an equivalent porous medium of a single porosity. However, it considers local thermal non-equilibrium between solid rock matrix and fluid flowing in the factures and employs two energy conservation equations to describe heat transfer in the rock matrix and in the fractures, respectively, enabling the modeling and analyses of convective heat exchange in the heat reservoir. Another salient feature of this model is its capability of simulating the complete subsurface heat exchange process in EGS. The EGS subsurface geometry of interest physically consists of multiple domains： open channels for injection and production wells, the artificial heat reservoir, and the rocks enclosing the heat reservoir, while computationally we treat it as a single-domain of multiple sub-regions associated with different sets of characteristic properties （porosity and permeability, etc.）. This circumvents typical difficulties about matching boundary conditions between sub-domains in traditional multi-domain approaches and facilitates numerical implementation and simulation of the complete subsurface heat exchange process. This model is used to perform a comprehensive parametric study with respect to an imaginary doublet EGS. Effects of several parameters, including the permeability of heat reservoir, heat exchange coefficient in the heat reservoir, the specific area of fractures in the heat reservoir, and thermal compensation from surrounding rocks, on the heat extraction efficiency and EGS lifetime are analyzed.

嵌套简单ILU分解代数预处理方法

In this paper, we propose a nested simple incomplete LU decomposition (NSILU) method for preconditioning iterative methods for solving largely scale and sparse ill-conditioned hnear systems. NSILU consists of some numerical techniques such as simple modification of Schur complement, compression of ill-condition structure by permutation, nested simple ILU, and inner-outer iteration. We give detailed error analysis of NSILU and estimations of condition number of the preconditioned coefficient matrix, together with numerical comparisons. We also show an analysis of inner accuracy strategies for the inner-outer iteration approach. Our new approach NSILU is very efficient for linear systems from a kind of two-dimensional nonlinear energy equations with three different temperature variables, where most of the calculations centered around solving large number of discretized and illconditioned linear systems in large scale. Many numerical experiments are given and compared in costs of flops, CPU times, and storages to show the efficiency and effectiveness of the NSILU preconditioning method. Numerical examples include middle-scale real matrices of size n = 3180 or n = 6360, a real apphcation of solving about 755418 linear systems of size n = 6360, and a simulation of order n=814080 with structures and properties similar as the real ones.

Application of Lagrange＇s equation to rigid-elastic coupling dynamics

A consistent focus in theoretical mechanics has been on how to apply Lagrange's equation to continuum mechanics.This paper uses the concept of a variational derivative and its laws of operation to investigate the derivation of Lagrange's equation,which is then applied to nonlinear elasto-dynamics.In accordance with the work-energy principle and the energy conservation law,kinetic and potential energies are proposed for rigid-elastic coupling dynamics,whose governing equation is established by manipulating Lagrange's equation.In addition,case studies are used to demonstrate the application of the proposed method to spacecraft dynamics.

Energy adaptive MAC protocol for IEEE 802.15.7 with energy harvesting

The medium access control(MAC) protocol for indoor visible light communication(VLC) with energy harvesting is explored in this paper. The unfairness of throughput exists among devices due to the significant difference of their energy harvesting rates which changes with distance, acceptance angle and the obstruction probability. We propose an energy harvesting model, a new obstruction probability model and an energy adaptive contention algorithm to overcome the unfairness problem. This device can adjust its contention window according to the energy harvesting rate. As a result, the device with lower energy harvesting rate can get shorter contention window to improve its transmission opportunity. Simulation results show that our MAC protocol can achieve a higher degree of fairness.