冷轧薄宽带钢局部型中浪瓢曲变形行为研究

针对薄宽带钢冷轧过程中易发多发的局部型中浪瓢曲缺陷,引入非均匀载荷宽度、弹性约束系数及平均张应力建立了屈曲变形的解析计算模型。应用能量最低原理对屈曲变形区域进行搜索求解,得到了局部型中浪屈曲临界条件(包括临界应力、屈曲波长和屈曲波宽),获得了其与非均匀载荷宽度、弹性约束系数、平均张应力的关系,并发现平均张应力是产生局部型中浪的重要影响因素。应用样条有限元方法对局部型中浪进行数值仿真分析,验证了屈曲解析计算方法的正确性。在实验轧机上进行了轧制研究,通过轧制获得了局部型中浪屈曲模态,对实验结果分析得到了相对应的屈曲临界条件,与解析法和样条有限元法结果基本吻合,证明了样条有限元计算方法与解析计算方法的正确性及其工程应用价值。     

9.3大阅兵:高标准让军魂荡气回肠

<正>阅兵是展示辉煌的时刻,而为这一辉煌采取的所有的标准,不啻也是宝贵的财富,应当成为践行标准的榜样……这个月最令人难忘、最引人自豪、最提振国威的事情,当属"9.3"大阅兵,它有着以往没有的多重的亮点:首次以纪念抗日战争暨世界反法西斯战争胜利为阅兵主题,彰显维护和平是全世界人民共同的愿望。首次邀请外国军队代表参加分列式,体现纪念大会的国际性。首次组织抗战老兵包括国民党老兵参加,体现了对历史的尊重,体现全民族抗战的特色。首次编组英模部队方队受阅,展示中国共产党在抗战中定海     

云冈遗韵

<正>云冈石窟,历经1540年的人间风雨而硕立至今的那种坚强、博爱与宽容的佛国神界!这净25米高的崖壁上蜂窝般开凿出的是人间的奇迹,人类的智慧,     

分光光度计使用维护的注意事项

一、分光光度计检定的主要项目对分析结果的影响 1.波长准确度 分光光度法必须对应于样品吸收光谱中的某一个吸收峰的波长.但由于仪器本身存在的误差和不同的人员进行测量时产生的误差,单色光的实际波长与仪器的波长读数值之间会存在一定的误差.     

乡野如画醉金秋

秋天在不经意间早已悄然远去,留下的是那金色的记忆。乡野的秋色金灿灿。柿子树上硕果累累,红红火火的柿子和层次分明、错落有致的黑色枝干在弥漫的烟雾中若隐若现、飘逸洒脱,宛如一幅写意的国画。     

国内外仪器指标的接轨与合格判断

随着科学技术的发展和科研任务的需要,测量仪表的使用大幅度增加,因此检定的任务量也随之大幅攀升.其中国外仪表占了很大的比重,但在仪器技术指标的表达方式上国外各个厂家不尽相同,与国内计量术语和仪器技术指标的表达方式更是存在较大的差异,这对于仪器的使用和计量检定的合格性判断是一个重要的问题,关系到购置仪器的验收与使用,进而关系到科研任务的质量保障.     

甲醛气体传感器研究进展

甲醛是室内空气的主要污染物之一,随着人们对室内空气污染的日益关注,对甲醛的准确及时检测显得更加重要.目前检测甲醛气体最为快速的方法就是传感器法.在综合分析了国内外甲醛气体传感器的研究现状的基础上,着重就测定甲醛的电化学传感器、基于化学发光的传感器、金属氧化物传感器、电子鼻、声表面波传感器的特性进行了阐述与剖析,指出了甲醛气体传感器存在的问题,并预测了其发展趋势.     

世界著名自驾车露营地

<正>露营在国外已经拥有超过100年的历史,露营地的管理和经营方式大多参照了酒店,也有星级之分。随着人们需求的变化,露营地提供的设施和服务也在不断跟进。如今,在一些著名的露营地,已经不仅仅能够看到为自驾车、房车露营者提供的营位和日常生活的基础设施,还有诸如高尔夫、骑行、划船等形式多样的体育运动,以及像毗邻历史悠久的古村落这样的特色看点。在很多国家,建立一个享有声誉的汽车营地甚至成为了拉动旅游业发展的重要手段之一,也因此得到了政府的大力支持。     

汽车阳极电泳线改造为阴极电泳线的实践

为了将车身涂装线中的阳极电泳改造成阴极电泳,在保留前处理不变的前提下,首先布置合理的工艺流程、确定阴极电泳工作原理,然后对阴极电泳的电泳槽、漆液主循环系统、超滤系统、阳极液循环系统、热交换循环系统、阴极电泳电源和电泳后清洗系统的技术参数进行认真的分析和计算,使改造后的阴极电泳的各项技术指标达到了设计的要求.结果表明,通过局部的技术改造,将车身涂装线的阳极电泳改造成阴极电泳完全可行.     

家的幸福瞬间

家是心灵的港湾,让我们寄托一生;家是人生的加油站,让我们纾解疲劳。家是能铺开心事的地方,家是受伤时的创口贴,家是握在手里盈盈一脉的馨香,家是每一砖每一石都用爱砌出来的城堡。家是以爱为圆心,一家人手牵手为半径走过的一个圆;家是整个世界在下雪,走进其中却是春天的角落;     

Shrinkage compensation approach proposed for ABS material in FDM process

Dimensional accuracy of parts manufactured by Fused Deposition Modelling (FDM) greatly suffers from the shrinkage problems of the available polymer materials. This paper proposes a constructive idea for resolving the shrinkage issues and explains how shrinkage could be managed by interior geometry of the artifacts fabricated on desktop 3D printers. The main principle for preventing the deterioration on dimensional accuracy of the holes/slots is to utilize the auxiliary lines located from the hole’s perimeter to the outer boundaries of the artifact. Thus, the shrinkage of these auxiliary line segments simply helps to pull the original hole backward, acting against the predicted contraction. In this paper, the proposed approach will be examined using a finite element analysis tool to predict the shrinkage behavior of the fabricated samples along with necessary measurements taken on the Coordinate Measuring Machine. Additionally, an analytical framework for modeling the shrinkage behavior of ABS is to be elaborated. The coherence of the simulations and the measurements are to be analyzed regarding the effect of the geometry and material color on the shrinkage behavior. The discussion involves the improvement on the dimensional accuracy of 3D printed features.     

Dynamic simulation of a single-effect ammonia–water absorption chiller

A lumped-parameter dynamic simulation of a single-effect ammonia–water absorption chiller is performed. Modeling is based on the continuity of species constituting the ammonia–water mixture and the conservation of energy for each component of the absorption chiller. Ordinary differential equations governing the response of each component and the algebraic equations describing the constitutive relation are solved in parallel by numerical integration. The model has been applied to a commercially available 10.5 kW absorption chiller to study the transients of temperature, pressure, concentration, and void fraction of each component during the start-up operation. The time constant of the absorption chiller is also investigated. The parameters considered are the bulk concentration of the ammonia–water solution, the mass of the solution filled, and the volumes of key components of the absorption chiller. In addition, the reduction of the time constant by a stepwise turn-up and turn-down of the flue gas flow rate during the primary stage of start-up period is demonstrated.     

Capturing Nitrosamines in Environment by Zeolite

To meet the requirement of environment protection, the adsorption of volatile nitrosamines, which are carcinogenic compounds in tobacco smoke, by zeolite is investigated in this article, along with the temperature programmed surface reaction of nitrosamines on zeolite to assess the catalytic capability of the porous material on the decomposition of the carcinogens. The actual function of zeolite to reduce the level of nitrosamines in cigarette smoke is also studied. The influences of zeolite pore's structure and the surface acid-basic properties of the adsorbent on the adsorption are explored in terms of geometric matching content and adsorbent-adsorbate interaction. Moreover, the role played by the cation of zeolite in the adsorption of volatile nitrosamines is discussed and the possible attracting range of the sodium cation in basic zeolite to pull the nitrosamine molecule is tentatively calculated. Owing to the specific ability of capturing nitrosamines, zeolite is proven to be the most effective additive encased within a cigarette as the functional additive for lowering the nitrosamines content of smoke to protect the environment and public health. Other porous oxides such as amorphous silica and alumina are also utilized in these experiments, and their actual functions to trap nitrosamines as well as their potential application as the candidates for cigarette additives are discussed and prospected, too.     

Corrosion Resistance of an electrodeposited Zinc Coating Containing CeO2 Nanoparticles

A Zinc coating containing CeO2 nanoparticles has been deposited by electrodeposition in a zinc plating bath.The content of CeO2 in the coating is 0.22 mass%. The results of weight loss experiments and electrochemistry tests show that corrosion resistance of the Zinc coating containing CeO2 nanoparticles is remarkably improved in contrast to the pure zinc coating in 0.5 M MgSO4 solution. The effects of CeO2 microparticles on the corrosion resistance of the zinc coating have been studied, the results show that CeO2 microparticles have no effect on the corrosion resistance of the zinc coating. SEM and XRD experiments suggest that the presence of CeO2 nanoparticles in the coating causes the modification of the surface morphology and preferential orientation of the crystal planes; therefore, the reason for the enhancement of corrosion resistance is mainly related to improvement of the structure of the coating.     

Archaeometallurgical contributions to a better understanding of the past

Archaeometallurgical investigations, and in particular those employing metallographic techniques, have greatly increased our understanding of the past, primarily by improving our knowledge of the histories of technological developments. However, these studies have potential for contributing to our comprehension of many more aspects of life in the past. The series of case studies presented here illustrate the application of metallography not only in elucidating the history of technology but also in areas such as the dating of objects, the determination of the spread of technologies and the nature and implications of the contact of cultures with the ‘outside’ world.     

Corrosion of reinforcement induced by environment containing chloride and carbon dioxide

Reinforced concrete structures during their exploitation may be exposed to the common action of carbonation and chlorides causing corrosion of steel reinforcement. Therefore, the related data seem to be interesting and important when the evaluation of the service life of the structures is the object of interest. This fact was a motivation for the present experimental study on the sequence of action of chloride solutions and carbonation of the embedding concrete. The results obtained show that carbonation of concrete foregoing the action of chloride solutions may intensify the process of corrosion of steel reinforcement in comparison to the converse sequence of the action of mentioned media. At the same time the natrium chloride solution has been shown as a more aggressive medium opposite to the calcium and magnesium chloride solutions.     

Modelling enthalpy and entropy of pure and mixed refrigerants with an innovative corresponding states method

In this work an original improvement of the Corresponding States technique is developed and a new model, based on a three parameters CS format, is proposed to predict the enthalpy and the entropy of the new generation halogenated alkanes fluids together with some alkanes. Limiting the analysis of the selected fluids to a specific thermodynamic property behaviour, an appropriate conformality approach can be deduced, which allows to set up a predictive model of high accuracy level on a wide range of the enthalpy and entropy surfaces. The fundamentals of the model are innovative scaling parameters deduced from the enthalpy of vaporization and from two dedicated equations, belonging to the selected family of fluids. This allows to set up innovative models following a CS format. Through the introduction of advanced mixing rules, the models can be simply extended to calculate the corresponding properties for mixtures. The proposed models allow also the calculation of VLE for systems of rather regular behaviour. The required inputs for a pure target fluid are an ideal gas isobaric heat capacity correlation, a single value of saturated liquid density and of vaporization enthalpy; if the last one is lacking, a single value of vapor pressure can be alternatively supplied. For non azeotropic mixtures the enthalpy and entropy models are predictive, whereas in case of azeotropy VLE calculations are possibly only applying regressed interaction coefficients. Due to the lack of accurate experimental enthalpy data and to the particular nature of the entropy function, the validation of the models is proposed against fundamental dedicated EoS available, both for pure and mixtures, for a significant number of the studied family of fluids. The predictive character of the proposed approach as well as the high performances reached, make these models particularly suitable for the new families of fluids regarding advanced technological applications.     

Ice crystal growth in supercooled solution

Study on the crystal growth of ice in water-ethyleneglycol solution was carried out, experimentally. The ice crystal, which was seeded on top of the capillary tube, propagated inside the tube slowly and began to grow freely at the tip of the tube in subcooled solution. The outer diameter of the tip of the capillary tube was less than 0.1 mm, which was much smaller than that of other researchers. Hence, considerable reduction of the influence of the existence of a capillary was accomplished and the initial growth of a single crystal was observed, precisely. Under the condition of subcooling of less than 8 K, the shape of the crystal was observed to be different from that of the one in pure water. The velocity of dendrite ice growth and the radius of the curvature of the tip were measured. It was found that after the dendrite ice developed to a certain size, the velocity of the dendritic growth and the radius of curvature were kept steady, and its values were dependent on the degree of subcooling and the concentration of the solution.     

Untersuchung von Schmelz‐ und Rekristallisationsprozessen sowie Riss‐, Oxid‐ und Porenbildung beim Schweißen

Investigation of melting and re‐crystallization processes and of crack, oxide and pore formation during welding In the paper some known investigation methods of the primary re‐crystallization and of the structure of the crystallization front are discussed. All these methods have disadvantages, in some cases they cause a limited validity or are expensive. The presented new method is based on the micrographic recording of the melting and solidifying metal surfaces. The method overcomes the above‐mentioned disadvantages. It is able to investigate in the welding seams not only the primary re‐crystallization processes but also the secondary ones including the formation of cracks and pores and the appearance of non‐metallic inclusions like oxides. The facilities of the method are demonstrated on some examples of use.     

对广电数字化运动的几点看法——兼谈对信息时代的数字技术标准化意义的反思

从信息革命的角度对于当前这场广电数字化运动做定位分析。对当前数字电视领域中的一些有争议的问题提出了看法。如,公共平台与收费平台的关系,服务平台的统一,整体平移,外来标准和自主标准,数字标准的统一等。提出了对标准化意义的反思。指出,在信息时代,给社会和技术带来进步的往往是追求标准化的过程,而不是标准建立的事实本身。近几年来,许多人已经开始意识到工业时代标准化的“旧瓶”,已经很难装下信息时代数字技术的“新酒”。标准化的工作要有一种新思维来适应信息社会的变化和特点。