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;     

Similarity solutions for slender dry patches with thermocapillarity

The lubrication approximation is used to investigate slender dry patches in an infinitely wide film of viscous fluid flowing steadily on an inclined plane that is either heated or cooled relative to the surrounding atmosphere. Four non-isothermal situations in which thermocapillary effects play a significant role are considered.Similarity solutions describing a thermocapillary-driven flow with a dry patch that is widening or narrowing due to either gravitational or surface-tension effects on a non-uniformly heated or cooled substrate are obtained, and examples of these solutions, when the substrate temperature gradient depends on the longitudinal coordinate according to a general power law, are presented. When gravitational effects are strong, the solution contains a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing pendent dry patch and a widening sessile dry patch, whose transverse profile has a monotonically increasing shape. When surface-tension effects are strong, the solution also contains a free parameter, and for each value of this parameter there is both a unique solution representing a narrowing dry patch, whose transverse profile has a monotonically increasing shape, and a one-parameter family of solutions representing a widening dry patch, whose transverse profile has a capillary ridge near the contact line and decays in an oscillatory manner far from it.Similarity solutions are also obtained for both a gravity-driven and a constant-surface-shear-stress-driven flow with a dry patch that is widening or narrowing due to thermocapillarity on a uniformly heated or cooled substrate. The solutions in both cases contain a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing dry patch on a heated substrate and a widening dry patch on a cooled substrate, whose transverse profile has a monotonically increasing shape.     

摩擦调节剂抑制钢轨波磨的机理研究

基于轮轨之间的摩擦耦合自激振动引起钢轨波磨的观点,论文建立了车辆稳态通过小半径曲线时由轮对－钢轨－轨枕组成的轮轨系统有限元弹性振动摩擦自激振动有限元模型,用ABAQUS软件对该模型的运动稳定性进行了分析,重点研究了轮轨摩擦系数和蠕滑力-蠕滑率曲线负斜率对轮轨系统摩擦自激振动的影响。计算结果显示,轮轨摩擦系数对轮轨摩擦自激振动有重要影响,当控制摩擦系数 时可以消除钢轨磨耗型波磨,蠕滑力-蠕滑率曲线负斜率对钢轨波磨有显著影响。     

Pd-C高温共晶点复现装置研制

主要针对Pd-C高温共晶点复现装置的组成进行介绍,其中包括复现用高温均热炉炉体、温度控制系统、真空泵、充气保护装置、水冷系统、复现用的石墨坩埚、二等B型标准热电偶和Pt-Pd热电偶等。针对石墨坩埚的灌注和共晶点复现过程进行了描述,根据复现的试验数据进行了相应的分析。     

A general expression for an area integral of a point-wise J for a curved crack front

The expression for the J-integral at a point on a three-dimensional crack front, obtained from a surface independent integral, is in general a sum of a contour integral and an area integral. In this work a general expression of an area integral for a crack with a curved front is derived in curvilinear coordinates. In certain situations the area integral vanishes and previously known cases are a straight crack front in plane stress or plane strain. The general conditions for a vanishing area integral are studied. It is shown that the area integral is non-zero for cracks with a curved front in the direction of crack extension. Some examples of curved cracks are given, for which the area integral vanishes and that are of interest in practice.     

Non-linear predictive control of a vapour compression cycle

A potential energy saving can be obtained by a global optimal setting of each actuator in a vapour compression cycle. This paper describes a predictive optimal control algorithm applying this strategy. At each step, an optimal command profile is computed, upon predictions of variables system evolution, using a simple non-linear model of a vapour compression cycle. Choice of this profile is based on a multiple criterion including cycle efficiency and technological constraints. The approach is experimentally validated on a pilot scale refrigeration plant with variable speed compressor. Trials have been performed and showed a meaningful energy saving.     

Tunable dual-wavelength thulium-doped fiber laser at 1.8 μm region using spatial-mode beating

This study describes a proposal and experimental demonstration of a tunable thulium-doped fiber laser with a multi-wavelength output operating at 1.8 μm. The introduction of a multi-mode non-adiabatic taper fiber into a single-mode cavity induces spatial-mode beating and a consequent narrow band filter mechanism. The fiber laser can be tuned by changing the state of the polarization in a ring cavity via adjustment of a polarization controller. The resulting outputs for single and dual wavelengths with different spacing are reported in detail.     

The substitution of R134a with R744: An exergetic analysis based on experimental data

This paper deals with the problem of R314a substitution with a natural refrigerant fluid. A comparison is performed between R134a and R744 (CO₂). R134a is a hydrofluorocarbon with a large direct warming impact (GWP), whereas the R744 contribution is negligible. A comparative exergetic analysis, carried out with experimental tests, has been presented. This paper compares a commercial R134a refrigeration plant and a prototype R744 system working in a trans-critical cycle. Based on the experimental data an exergetic analysis has been carried out on the overall plant and on each device. The overall exergetic performances of the classical vapour compression plant working with R134a are consistently better than that of R744 (from a minimum of 20 to a maximum of 44%). The performance of the individual components of the plant has been analyzed, in order to pinpoint those contributing most to the decrease in the exergetic performance of R744.     

低爆速炸药中密度调节剂的优选

通常在猛炸药中加入一定量的密度调节剂可制得低爆速炸药,密度调节剂可为带微孔物质或轻质微粉颗粒。本文通过试验研究,对几种常见的密度调节剂对于猛炸药的稀释能力进行对比分析,从中优选出具有较强稀释能力的材料,为低爆速炸药配方研究提供借鉴。     

The X-HPD—conceptual study of a large spherical hybrid photodetector

We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to readout the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal.

Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10–30 keV energy range. The scintillation light was readout with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT.     

Spin Effects in Lateral Quantum Dots

We present the review of our work on spin effects in single lateral quantum dots with the emphasis on the results of Coulomb blockade spectroscopy studies. Realization of a spin-based quantum bit proposal in a lateral quantum dot is discussed. Described are the ways of isolating a single electron spin in a dot containing only one as well as many electrons. Demonstrated is a current readout of spin transitions in a dot by means of spin blockade spectroscopy due to spin polarized injection/detection mechanism in a lateral dot. Discussed are transitions induced both by changing a magnetic field and a number of electrons in a dot with the emphasis on the effects observed close to filling factor in a dot = 2.