Analysis of 2D flow and heat transfer modeling in fracture of porous media

Heat and mass transfer between porous media and fluid is a complex coupling process,which is widely used in various fields of engineering applications,especially for natural and artificial fractures in oil and gas extraction.In this study,a new method is proposed to deal with the flow and heat transfer problem of steady flow in a fracture.The fluid flow in a fracture was described using the same method as Mohais,who considered a fracture as a channel with porous wall,and the perturbation method was used to solve the mathematical model.Unlike previous studies,the shear jump boundary condition proposed by Ochoa-Tapia and Whitaker was used at the interface between the fluid and porous media.The main methods were perturbation analysis and the application of shear jump boundary conditions.The influence of permeability,channel width,shear jump degree and effective dynamic viscosity on the flow and heat transfer in the channel was studied by analysing the analytical solution.The distribution of axial velocity in the channel with the change of the typical parameters and the sensitivity of the heat transfer was obtained.     

Domain structure-based transfer learning for cross-domain word representation

Cross-domain word representation aims to learn high-quality semantic representations in an under-resourced domain by leveraging information in a resourceful domain. However, most existing methods mainly transfer the semantics of common words across domains, ignoring the semantic relations among domain-specific words. In this paper, we propose a domain structure-based transfer learning method to learn cross-domain representations by leveraging the relations among domain-specific words. To accomplish this, we first construct a semantic graph to capture the latent domain structure using domain-specific co-occurrence information. Then, in the domain adaptation process, beyond domain alignment, we employ Laplacian Eigenmaps to ensure the domain structure is consistently distributed in the learned embedding space. As such, the learned cross-domain word representations not only capture shared semantics across domains, but also maintain the latent domain structure. We performed extensive experiments on two tasks, namely sentiment analysis and query expansion. The experiment results show the effectiveness of our method for tasks in under-resourced domains.     

3-D Elasticity Solutions of Layered Rectangular Plates Subjected to Thermo-Loads

According to the exact three-dimensional (3D) thermoelasticity theory, the elasticity solution of the simply-supported layered rectangular plates subjected to steady temperature loads was studied. An analytical method was developed to solve the temperature, stress and displacement fields in the plate. Firstly, the general solutions of the temperature, displacements and stresses in a simply-supported isotropic layer were obtained by solving the 3-D heat conduction equation and the 3-D equations of elasticity respectively, which were expressed in the form of double Fourier series. Then, the temperature, displacement and stress relationships between the upper surface and the lower surface of the isotropic layer were derived. Based on the continuity of the temperature, the heat flux, the displacements and the stresses on the interface of two adjacent layers with different material properties, the recursive formulae of temperature, displacements and stresses between the bottom layer and the top layer of the layered plate were obtained by using the transfer matrix method. The unknown coefficients in the solutions for every layer were uniquely determined by the upper surface and lower surface conditions of the plate. The distributions of the temperature, displacements and stresses in the plate were given by substituting the unknown coefficients obtained back to the recurrence formulae and the solutions. The convergence of the solutions was checked with respect to the number of the terms of series. Comparing the results with those obtained from the finite element method, the correctness of the present method was verified. Finally, the effects of surface temperatures, plate thickness, layer number and material properties of each layer on the distributions of the temperature, displacements and stresses in the plates were discussed in detail.     

Comparison of microbial transfer rates from Salmonella spp. biofilm growth on stainless steel to selected processed and raw meat

Salmonella biofilm cells can serve as a serious source of cross-contamination, both in the home and at food production sites. The objectives of this study were to determine the transfer rates (RTs) of Salmonella biofilm cells and to model the transfer process of biofilm cells from stainless steel surfaces to raw meat. The results showed that the RTs were significantly influenced by the types of meat products, with bacon and emulsified sausage showing higher RTs and roast pork showing lower RTs. Higher RTs of biofilm grown in a meat-based medium, Meat Thawing-Loss Broth (MTLB), were observed as compared to that in a standard growth medium (TSB). The logistic, exponential and multi-roots models could be used to satisfactorily describe the transfer of biofilm cells as demonstrated by use of MSE, F-test and R². There was no difference in attachment strength (reflected by the coefficients of transfer models) of biofilm grown in TSB or MTLB, as shown by the coefficients of r, D and B in three models. Compared with the exponential and the multi-roots models, the logistic model was able to more accurately fit the whole transfer process of biofilm cells. Our findings highlight the occurrence of cross-contamination with biofilm cells, and the models may provide useful tools in quantitative microbiological risk assessment of meat products.     

New environmentally friendly composite laminates with epoxidized linseed oil (ELO) and slate fiber fabrics

This work focuses on the development of new composite laminates based on the use of epoxidized linseed oil (ELO) as matrix and reinforcement fabrics from slate fibers with different silane treatments. The curing behavior of the ELO resin is followed by differential scanning calorimetry (DSC) and the gelation is studied by oscillatory rheometry and gel-time. Composite laminates of ELO matrix and slate fabrics are manufactured by Resin Transfer Molding (RTM) and the mechanical properties of the composite laminates are tested in tensile, flexural and impact conditions. The effects of different silane coupling agents on fiber-matrix interface phenomena are studied by scanning electron microscopy (SEM). As in other siliceous fibers, silane treatment leads to improved mechanical performance but glycidyl silane treatment produces the optimum results as the interactions between silanized slate fiber and epoxidized linseed oil are remarkably improved as observed by scanning electron microscopy (SEM).     

The superlattice structure and self-adaptive performance of C–Ti/MoS2 composite coatings

To improve the self-adaptability of MoS₂ coating in different environments, the coatings were doped with functional C and Ti by unbalanced magnetron sputtering system. The clear superlattice structure with minimal modulation period was investigated by High Resolution Transmission Electron Microscope (HRTEM). The co-doped coatings have better mechanical properties due to the special structure and the formation of C–Mo, Ti–S and Ti–O bonds, and better lubrication performance in both high humidity and vacuum than those of the single-doped ones. The doped Ti not only facilitates the formation of the MoS₂ (002) basal plane, but also improves the oxidation resistance of the composite film. The degree of friction-induced graphitization on the wear tracks and the quality of transfer films on the wear scars are key factors affecting the lubrication performance of the composite film. In the high-humidity environment, the reasonable doping elements can promote the formation the high-quality transfer film by interacting with H₂O water molecules, which will benefit the lubrication of the coating better. Our findings deepen the understanding of MoS₂ composite coating and provide a new solution for improving the self-adaptability of the coating.     

风电扭矩限制器性能测控系统设计

扭矩限制器是风力发电机组中用于过载保护的关键部件，但目前对其打滑扭矩、疲劳寿命等性能的测试存在流程复杂、自动化程度低、功能单一等缺点，为此设计了一种风电扭矩限制器性能测控系统。根据测控系统的功能要求，首先进行了硬件结构设计，选用PLC为下位机主控单元，工控机作为上位机管理及监控单元。随后采用组态软件设计了人机交互界面，并编写PLC控制程序，实现了对测控系统的控制和管理。经过现场应用证明，该测控系统具有运行稳定、方便快捷的特点，能够满足扭矩限制器的测试要求。     

节点度估计和静态博弈转发策略的Ad Hoc网络路由协议

针对Ad Hoc网络路由发现过程中广播路由请求分组导致的广播风暴问题，提出了一种基于节点度估计和静态博弈转发策略的Ad Hoc网络路由协议NGRP.NGRP考虑边界影响，采用分段函数的思想将网络场景分为中心、边和角区域，分别估算网络中节点在不同区域的节点度，避免了周期性广播Hello消息获取节点度导致的开销；NGRP路由请求分组的转发采用静态博弈转发策略，利用节点度估算参与转发路由请求分组的节点数量，将转发和不转发作为策略集合，设计效益函数，通过纳什均衡获得节点转发路由请求分组的转发概率，从而减少了路由请求分组广播过程中产生的大量的冗余、竞争和冲突，提高了路由发现过程中路由请求分组的广播效率.运用NS-2对协议的性能进行大量的仿真，结果表明：NGRP的分组投递率、路由开销、MAC层路由开销和吞吐率这4项指标明显优于AODV+FDG，AODV with Hello和AODV without Hello协议.     

Bloch–Floquet waves in flexural systems with continuous and discrete elements

In this paper we describe the dynamic behavior of elongated multi-structured media excited by flexural harmonic waves. We examine periodic structures consisting of continuous beams and discrete resonators disposed in various arrangements. The transfer matrix approach and Bloch–Floquet conditions are implemented for the determination of different propagation and non-propagation regimes. The effects of the disposition of the elements in the unit cell and of the contrast in the physical properties of the different phases have been analyzed in detail, using representations in different spaces and selecting a proper set of non-dimensional parameters that fully characterize the structure. Coupling in series and in parallel continuous beam elements and discrete resonators, we have proposed a class of micro-structured mechanical systems capable to control wave propagation within elastic structures.     

IPv6的部署进程和过渡技术应用

IPv6过渡技术广泛应用在Internet上，技术发展相对成熟。为了给内部网的升级换代提供有效的参考，实现内部网的平稳过渡。本文首先对常用的双栈技术、隧道技术和协议转换技术的基本原理进行分析研究。