Non-axisymmetric instability in the Taylor-Couette flow of fiber suspension

An analysis of the instability in the Taylor-Couette flow of fiber suspensions with respect to the non-axisymmetric disturbances was performed. The constitutive model proposed by Ericksen was used to represent the role of fiber additives on the stress tensor. The generalized eigenvalue equation governing the hydrodynamic stability of the system was solved using a direct numerical procedure. The results showed that the fiber additives can suppress the instability of the flow. At the same time, the non-axisymmetric disturbance is the preferred mode that makes the fiber suspensions unstable when the ratio of the angular velocity of the outer cylinder to that of the inner cylinder is a large negative number.     

On the structural features of fiber suspensions in converging channel flow

The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective viscosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of the rate-of-strain tensor and the fiber orientation state; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local streamlines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of effective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds number but on the converging channel angle. Projects (No. 19925210) supported by the National Natural Science Foundation of China     

On the structural features of fiber suspensions in converging channel flow

INTRODUCTIONModelingfiber fiberinteractionsinnon di lutefibersuspensionsanddescribinghowtheseinteractionsaffecttherheologicalpropertiesofthesuspensionsintheflowsarefundamentalandimportantinmulti phaseflowsresearch .Ulti matelywewouldliketobeabletodesignan…     

Emission characteristics and combustion instabilities in an oxy-fuel swirl-stabilized combustor

This paper presents an experimental study on the emission characteristics and combustion instabilities of oxy-fuel combustions in a swirl-stabilized combustor. Different oxygen concentrations （Xoxy=25%-45%, where Xoxy is oxygen concentration by volume）, equivalence ratios （φ=0.75-1.15） and combustion powers （CP= 1.08-2.02 kW） were investigated in the oxy-fuel （CH4/CO2/O2） combustions, and reference cases （Xoxy=25%-35%, CH4/N2/O2 flames） were covered. The results show that the oxygen concentration in the oxidant stream significantly affects the combustion delay in the oxy-fuel flames, and the equivalence ratio has a slight effect, whereas the combustion power shows no impact. The temperature levels of the oxy-fuel flames inside the combustion chamber are much higher （up to 38.7%） than those of the reference cases. Carbon monoxide was vastly produced when Xoxy〉35% or （φ〉0.95 in the oxy-fuel flames, while no nitric oxide was found in the exhaust gases because no N2 participates in the combustion process. The combustion instability of the oxy-fuel combustion is very different from those of the reference cases with similar oxygen content. Oxy-fuel combustions excite strong oscillations in all cases studied Xoxy=25%-45%. However, no pressure fluctuations were detected in the reference cases when Xoxy〉28.6% accomplished by heavily sooting flames which were not found in the oxy-fuel combustions. Spectrum analysis shows that the frequency of dynamic pressure oscillations exhibits randomness in the range of 50-250 Hz, therefore resulting in a very small resultant amplitude. Temporal oscillations are very strong with amplitudes larger than 200 Pa, even short time fast Fourier transform （FFT） analysis （0.08 s） shows that the pressure amplitude can be larger than 40 Pa.     

从协作到完善：大学与中小学的合作研究

大学的院本化自我发展不利于与中小学合作,双方实质上是一种共栖关系,双螺旋发展是一种较为适当的合作模式。理论者需要深度介入实践,注意两套话语系统的融合等细节,才能取得教师参与的积极性和学校支持,使得大学与中小学的合作从协作到完善。     

Science Letters： Research on 3D fiber orientation distribution in arbitrary planar flows

A non-stretchable fiber rotation in planar flows has been solved. The fiber will rotate periodically or run to the asymptotical direction decided by a discriminant defined in the paper involving the fiber aspect ratio and the flow characteristics. Subsequently the fiber orientation distribution is derived directly without the bother of solving the Fokker-Planck equation. The research clearly indicates the overall configuration of a fiber rotation movement in planar flows.     

小学科学课程与ICT文献综述

本文献主要回顾了自1989年以来小学科学课程的发展以及在科学课堂中应用ICT的研究。文章讨论了ICT对小学科学课程中教师与学习者的角色关系、教师的专业知识、程序技能和科学内容之间的平衡、形成性评价的应用等方面所产生的影响。此外,还提供了一套目前ICT被应用于促进优秀科学教学方式的批判性评估。最后,作者提倡要对ICT的各种应用以及它们对促进小学科学课程中儿童的学习有何种促进潜能开展系统研究,并为那些旨在促进儿童小学科学学习经验的软、硬件开发者提出了建议和启示。     

因特网上获取一次文献的方法技巧

随着Internet的全面普及、网上信息服务模式不断出现、网上信息发布更加便利，信息用户获取一次献难的老问题得到突破性的改善。但由于网络信息的过于庞大和无序，使无经验的用户根本就因不知所在而不得所需。本就目前Internet上所能获取的、同时又是用户最需要、最难获取的外期刊、国内外学位论、科技报告、国内外学术会议的一次献的网上获取方式、获取途径做充分的归总、陈述。     

印度初等教育性别公平问题及其启示

印度初等教育的发展中存在着诸多问题,其中以性别公平问题较为突出,本文由此从性别的角度来探讨印度初等教育近年来的发展成果和存在的问题,以及为解决这一问题印度政府所采取的政策和措施,并从中为我国初等教育的普及提供一些借鉴.     

In vitro inhibition of pigmentation and fiber development in colored cotton

Colored cotton has naturally pigmented fibers. The mechanism of pigmentation in cotton fiber is not well documented. This experiment was conducted to study the effects of respiratory chain inhibitors, i.e., rotenone and thiourea, on pigmentation and fiber development in colored cotton. After 1 d post-anthesis, ovaries were harvested and developing ovules were cultured on the liquid medium containing different concentrations of rotenone and thiourea for 30 d. The results demonstrate that both respiratory inhibitors reduced fiber length and ovule development under ovule culture conditions, and the inhibition efficiency of rotenone was much higher than that of thiourea. Rotenone and thiourea also showed significant effects on fiber pigment (color) development in colored cotton. In green cotton fiber, rotenone advanced fiber pigment development by 7 d at 200 μmol/L, while thiourea inhibited fiber pigmentation at all treatment levels (400, 600, 800, 1 000, and 2 000 μmol/L). Both respiratory inhibitors, however, had no significant effects on pigmentation of brown cotton fibers. The activities of cytochrome c oxidase (COX) and polyphenol oxidase (PPO) decreased significantly with increasing levels of both respiratory inhibitors. It is suggested that both respiratory inhibitors have important roles in deciphering the mechanism of pigmentation and fiber development in colored cotton.     

小学劳动教育与养成教育的整合实践

学生只有从小养成劳动的好习惯,才能热爱劳动,积极参与劳动。劳动课是义务教育阶段的重要课程之一,需要小学劳动教师科学合理地制订教学计划,采取新举措,完善劳动课程建设,提升小学生的劳动技能和素养。小学劳动与养成教育的结合,可以有效培养小学生动手和动脑的能力,让他们在轻松的氛围中学习。笔者从五个方面展开论述,旨在提升小学劳动教育实效。     

小学语文中劳动教育的渗透意义及策略

劳动教育是培养小学生正确劳动观念的重要途径,将小学语文和劳动教育结合起来势在必行。小学语文不是单独存在的,语文教材中的许多内容都源于生活,在小学语文中渗透劳动教育有利于锻炼小学生的思维能力和动手能力,发展小学生的心智,促进小学生全面发展。因此,小学语文教师要时刻关注劳动教育,创新课堂教学方式,通过多种渠道培养小学生的劳动意识,传承中华民族传统美德。     

小学自然合作学习研究

文章论述了作者在小学自然学科教学中实施合作学习的具体策略、基本模式和成效。     

小学语文教育与小学教育专业语文课程设计

自1992年至2001年,我国小学语文教育理念及教学内容都发生了很大的变化。据此,高师院校小学教育专业中文方向语文类课程也进行了相应地设计和规划,包括汉语、中国文学、文学概论、儿童文学、基础写作等组成的必修基础课程;以小学综合实践活动、班级管理、教师口语、书写、小学语文多媒体课件制作为内容的必修应用类课程;以小学语文教学论,小学语文教学研究、小学语文教育心理学等构成的语文教育类课程;还有教育实践课程和选修类课程,以培养师范生较高的语文素养,为成为合格的小学教师打下坚实的基础．     

小学道德教育中存在问题与解决对策

小学道德教育对于小学生的成长十分重要,良好的小学道德教育能够在很大程度上促进小学生的发展。因此,本文对小学道德教育进行研究,指出了目前小学道德教育中存在的问题。针对存在的问题,本文从学校、教师、家长等方面入手,更好地解决小学道德教育中存在的问题,促进小学生的良好发展。     

中小学教育策略探析

中小学年龄段的学生,还没有形成良好的世界观、人生观与价值观,其逻辑思维能力以及综合能力的发展也不够健全。因此,学校应有效加强对中小学教育教学策略的重视,积极更新中小学教育的管理理念,建立科学有效的教育思想,结合先进的教学手段,摒弃传统落后的教育模式,实现对中小学教育策略的创新,从而满足当今中小学生的学习需求,调动中小学生学习的积极性与热情。本文就中小学教育策略进行探讨与分析,以供参考。     

Properties of frictional bridging in fiber pull-out for fiber-reinforced composites

Stress equilibrium equations, boundary- and continuity-conditions were used to establish a theoretical model of progressive debonding with friction at the debonded interface. On a basis of the minimum complementary energy principle, an expression for the energy release rate G was derived to explore the interfacial fracture properties. An interfacial debonding criterion G≥Гi was introduced to determine the critical debond length and the bridging law. Numerical calculation results for fiber-reinforced composite SCS-6/Ti-6Al-4V were compared with those obtained by using the shear-lag models.     

多媒体技术在小学劳动教育中的应用分析

劳动课作为一门实践性学科,对于培养小学生的实践能力和行为习惯具有重要作用。多媒体技术在小学劳动教育中的应用,符合课程改革的要求,有利于激发小学生学习劳动知识的热情,为小学生掌握劳动技能、应用劳动技能奠定坚实的基础。因此,小学劳动教师要转变教学观念,提高多媒体等先进教学手段的利用率,真正提高课堂教学效果。     

捕捉生活元素,书写精彩篇章——小学语文习作生活化的探索与思考

语文学科在教育起步阶段中发挥着重要作用,而习作教学的充分落实对学生的语言综合应用能力与水平产生影响,因此加强习作能力是当前小学语文教学的关键环节。赋予小学语文习作生活化特征是依据新课标制定的授课内容,可以让学生从生活中获取写作灵感、增强习作体验。本文立足于新课改对于小学语文习作课堂所提出的全新要求,探究如何以生活化内容创新习作训练。     

浅析人本管理在农村小学教师管理中的应用

在教育领域里,农村小学教师担负着基础教育改革和发展以及素质教育实施的伟大历史重任,对他们的管理工作已经引起教育管理人员和研究人员的重视;同时当代教育领域的改革也迫切要求以管理的创新实现教育的创新。文章从农村小学教师实施人本管理的必要性出发,通过分析目前实现人本管理这一理念的制约因素,提出了具体应用办法,以期对小学教师管理水平的提高,以及提升对农村教师的关注尽绵薄之力。