某钢结构厂房及设备基础改造设计实例

本文总结了某钢结构厂房、地脚螺栓、设备基础、钢梁振动、零星构件等几个方面的改造措施。钢结构厂房改造应综合考虑残余应力和内应力及厂房空间作用。地脚螺栓和设备基础改造,需要设备和结构两个专业相互配合。通过轴向力传递钢梁上动荷载,可有效防止梁的过大振动。零星构件应尽可能采用钢构件。     

钢轨承重吊车梁的应用及其发展

在单层工业厂房中,由于生产工艺和设备检修的需要,通常都设置一种或二种类型的桥式吊车,进行工作件的运输、加工、设备维修等工作。支承桥式吊车的吊车梁,直接承受吊车超重运输产生的具有动力的移动荷载,受力情况比较复杂。同时吊车梁对传递厂房的纵向荷载,加强厂房的纵向刚度,保证厂房结构的空间工作,起着重要的作用。因此要求使用高强度钢材,较高标号水泥,施工要求严格,造价高,耗钢量大,在一般中型厂房中其用钢量约占厂房主要承重构件用钢量的20—30%。因此吊车梁的选型、设计和改革历     

某网架屋盖厂房的结构设计分析

以某一边开口的网架屋盖厂房为研究对象,利用空间有限元设计软件3D3S对该厂房整体进行了各荷载工况下的计算分析,并考察了其动力特性。结果表明：该厂房柱和屋面网架各杆件的强度、稳定性和长细比均符合规范要求,该结构稳定可靠,满足设计、施工和使用的要求。     

中板厂加热炉钢坯托出机研制与应用

针对济钢中板厂加热炉、辊道、厂房布置空间的特点和要求,设计出新型的符合实际需求的并具有独立知识产权的钢坯托出机.     

一钢不锈钢工程主厂房钢结构设计

本文介绍了一钢不锈钢工程主厂房钢结构设计，对特大型工业厂房的结构布置、温度作用、高层刚架结构体系进行了较全面分析，并对厂房各系统主要情况、关键技术作了描述。希望能对今后大型厂房，尤其是转炉炼钢厂房的设计起到借鉴作用。     

工业厂房钢筋混凝土排架结构设计

排架结构具有传力明确、构造简单、方便施工等特点,特别适用于大空间厂房的特殊要求.     

重工公司涂装厂房通风除尘设计

简要介绍重工公司将原机加工厂屠改建为喷砂、涂装厂房的通风除尘设计经验。采用国际上同类涂装厂房通行标准，重点解决大空间、大尺度厂房通风除尘的设计要求，选择合理的气流组织方式进行粉尘捕集，强化抽风吸尘效果，从整体上提升了涂装厂房的适用性。预留温度湿度调节接口，可达到特涂环境要求。同时考虑原有设施的就用，节约了投资。     

有色行业基本回暖

在国家应对国际金融危机相关政策措施作用下，有色金属生产下滑局面已得到扭转。随着有色金属价格逐步回升，以及消费需求的恢复性增长，企业盈利空间开始得到提升。而投资增长过快、产能过剩、出口下滑、集约化程度低等因素严重影响我国有色金属行业健康发展。     

轧钢车间自然通风降温的建筑措施初探

介绍对原老厂房的局部建筑的改造措施，表明增大冷风入口和天窗做法的改进，对强化厂房内自然通风所起的作用和效果，提出在设计此类厂房时应注意相关事项。以供借鉴参考。     

球墨铸铁管厂房建筑造型设计

以圣戈班(徐州)管道有限公司球墨铸铁管厂房为例,对组成厂房建筑立面设计的各个元素在工业厂房建筑设计中的作用进行了分析,阐述了厂房建筑立面设计的各个元素的处理原则,使工业建筑造型更富现代气息的方法。     

漩流氧枪转炉炼钢熔体的喷溅行为

 转炉冶炼过程金属熔体的喷溅对于转炉反应器的性能有重要影响。氧枪作为氧气射流的产生及控制单元,决定了转炉吹炼过程熔体的喷溅行为。通过水模型试验,研究了漩流氧枪转炉冶炼过程熔体的喷溅,考察了氧枪喷孔扭转角设计及操作参数下熔体喷溅速率和喷溅的空间分布规律,基于此,分析了漩流氧枪对转炉反应器性能的影响。结果表明,相比于传统氧枪吹炼,漩流氧枪吹炼时熔体喷溅速率降低,喷溅高度下降,喷溅在径向空间分布趋于均匀,且随着喷孔扭转角的增大,该分布规律变化更为显著,扭转角大于20°时,喷溅到炉口及炉外的熔体降为零。漩流氧枪吹炼时,喷溅速率及喷溅量在不同径向和高度位置处分布随着顶吹气量的增大而增大,受枪位的影响规律与扭转角有关。     

Structure-energy correlation for grain boundaries in F.C.C. metals—III. Symmetrical tilt boundaries

The correlation between the structure and zero-temperature energy of symmetrical tilt grain boundaries (STGBs) in f.c.c. metals is investigated using two embedded-atom-method potentials (for Cu and Au) and a Lennard-Jones potential fitted for Cu. Similar to free surfaces, misorientation phase space associated with these simple planar defects consists of only two degrees of freedom, namely those associated with the GB plane. The sampling of this two-dimensional phase space in terms of the stereographic triangle shows energy cusps as its corners and along its edges. These cusps are shown to arise from GB geometries with particularly small planar unit cells. Similar to free surfaces, a good correlation is found between the number of broken nearest-neighbor bonds per unit area and the GB energy. Also, as in our earlier study of twist boundaries, a practically linear relationship is found between the GB energy and volume expansion at the boundary. Finally, a comparison with twist boundaries shows that the STGBs represent the endpoints of the energy vs twist-angle curves. This enables a direct comparison of the properties of twist and tilt boundaries.     

The artistic function in Stage Design

Stage Design is a comprehensive art, set flat, space and time as a whole, will be time and space Factors in a comprehensive and flexible use of means that of artistic expression to create unique, by creating visual effects to convey information and emotio     

Structure and energy of (110) twist boundaries in the Ag/Ni system

Low-energy (110) twist boundaries have been studied in the Ag/Ni system. Four low-energy orientations were observed in the experiments using the particle rotation method (PRM) with (110)Ag crystallites sintered on the (110) surface of a single crystal Ni substrate. These are characterized by twist angles of 0, 35, 55 and 70°, measured between the two close-packed direction of the crystals at the boundary. The determination of the orientation of the samples was made by transmission electron microscopy. The reorientation of the particles was achieved in two ways: continuous rotation, and twinning. In samples with initial twist angles of 3, 35, and 49°, a progressive rotation of the particles was observed. The silver particles in the sample with 70° initial twist were reoriented to 0° by the nucleation and growth of twins which had parallel crystallographic directions with the Ni substrate. Samples with initial twist angles of 58 and 65° showed both types of reorientation. While the particles underwent a continuous rotation, twins nucleated and grew in the particles. The results of the experiments are compared with calculations with the embedded-atom method and with geometrical models of interfaces.     

Microstructure and Mechanical Properties of Copper Processed by Twist Extrusion with a Reduced Twist-Line Slope

Pure copper processed by a twist extrusion process with a reduced twist-line slope is investigated. Twist extrusion is a severe plastic deformation technique which is promising for scale-up because it allows for processing of relatively large metallic bars. On the way to commercialization, decreasing costs associated with processing is critical for twist extrusion. As one of the measures, reducing the twist-line slope—an important geometrical feature of twist extrusion—can be advantageous in terms of processing costs. The current study seeks to elucidate effects of reducing the twist-line slope on the microstructure, mechanical properties, and their heterogeneity in the processed metal, which were unclear because most of the previous research has focused on twist extrusion with high twist-line slopes (e.g., 60 deg). Results of the present study suggest that reducing the twist-line slope moderates grain refinement and limits improvement of mechanical properties of the twist-extruded metal. These findings are discussed in terms of the shear strain reversal which is inherent in the process.     

Left ventricular systolic torsion and early diastolic filling by echocardiography in normal humans

This study describes a novel 2-dimensional echocardiographic technique to measure left ventricular (LV) systolic twist in humans and relates this measure to early ventricular filling. LV twist is the counterclockwise rotation of the left ventricle during systole when viewed from the apex. The effect of ventricular twist has been postulated to store potential energy, which ultimately aids in diastolic recoil, leading to ventricular suction. The generated negative early diastolic pressures may augment early ventricular filling. We measured ventricular twist in 40 patients with normal transthoracic echocardiograms. End-systolic twist was determined by measuring rotation of the anterolateral papillary muscle about the center of the ventricle. LV filling was assessed by analysis of transmitral Doppler flow velocities. The mean value obtained was 9 +/- 7 degrees of rotation. Twist measurements were highly reproducible with an intraobserver correlation coefficient of r = 0.881, p <0.001. The magnitude of ventricular twist was strongly correlated positively with acceleration of the mitral E-wave (r = 0.75; p <0.0001) and negatively with the mitral E-wave acceleration time (r = -0.83; p <0.0001).     

Minimally invasive bedside craniotomy using a self-controlling pre-adjustable mechanical twist drill trephine

BACKGROUND: Craniotomy with a mechanical twist drill is a standard, minimally invasive procedure in neurosurgery, widely used for the drainage of chronic subdural hematomas and the placement of ventricular drains. Nevertheless, the use of a standard twist drill trephine bears the risk of causing cerebral lesions. METHOD: A commercially available mechanical twist drill system has been modified by a special self-controlling drill and a pre-adjustable distance holder that limits intracerebral penetration. After initial cadaver testing, the modified trephine has been used for 65 trephinations in patients (37 chronic subdural hematomas, 21 external ventricular drains, 6 frontal hygromas, 1 tumor cyst). RESULTS: There were no complications related to the modified trephine; cerebral lesions caused by drilling too deeply or by uncontrolled penetration were safely prevented. In our series no procedure related infections occurred, and the drilling time was reduced significantly. CONCLUSION: The described modified mechanical twist drill enables fast, easy, and safe craniotomy without jeopardizing the advantages of a mechanical twist drill. Therefore, it can be recommended particularly for difficult emergency conditions.     

Crystal structure of a B-DNA dodecamer containing inosine, d(CGCIAATTCGCG), at 2.4 A resolution and its comparison with other B-DNA dodecamers

The crystal structure of the dodecamer, d(CGCIAATTCGCG), has been determined at 2.4 A resolution by molecular replacement, and refined to an R-factor of 0.174. The structure is isomorphous with that of the B-DNA dodecamer, d(CGCGAATTCGCG), in space group P2(1)2(1)2(1) with cell dimensions of a = 24.9, b = 40.4, and c = 66.4 A. The initial difference Fourier maps clearly indicated the presence of inosine instead of guanine. The structure was refined with 44 water molecules, and compared to the parent dodecamer. Overall the two structures are very similar, and the I:C forms Watson-Crick base pairs with similar hydrogen bond geometry to the G:C base pairs. The propeller twist angle is low for I4:C21 and relatively high for the I16:C9 base pair (-3.2 degrees compared to -23.0 degrees), and the buckle angles alter, probably due to differences in the contacts with symmetry related molecules in the crystal lattice. The central base pairs of d(CGCIAATTCGCG) show the large propeller twist angles, and the narrow minor groove that characterize A-tract DNA, although I:C base pairs cannot form the major groove bifurcated hydrogen bonds that are possible for A:T base pairs.     

Crystal structure of an RNA octamer duplex r(CCCIUGGG)2 incorporating tandem I.U wobbles

The crystal structure of the RNA octamer duplex r(CCCIUGGG)2has been elucidated at 2.5 A resolution. The crystals belong to the space group P21and have unit cell constants a = 33.44 A, b = 43.41 A, c = 49.39 A and beta = 104.7 degrees with three independent duplexes (duplexes 1-3) in the asymmetric unit. The structure was solved by the molecular replacement method and refined to an Rwork/Rfree of 0.185/0.243 using 3765 reflections between 8.0 and 2.5 A. This is the first report of an RNA crystal structure incorporating I.U wobbles and three molecules in the asymmetric unit. Duplex 1 displays a kink of 24 degrees between the mismatch sites, while duplexes 2 and 3 have two kinks each of 19 degrees and 27 degrees, and 24 degrees and 29 degrees, respectively, on either side of the tandem mismatches. At the I.U/U.I mismatch steps, duplex 1 has a twist angle of 33.9 degrees, close to the average for all base pair steps, but duplexes 2 and 3 are underwound, with twist angles of 24.4 degrees and 26.5 degrees, respectively. The tandem I.U wobbles show intrastrand purine-pyrimidine stacking but exhibit interstrand purine-purine stacking with the flanking C.G pairs. The three independent duplexes are stacked non-coaxially in a head-to-tail fashion to form infinite pseudo-continuous helical columns which form intercolumn hydrogen bonding interactions through the 2'-hydroxyl groups where the minor grooves come together.     

The control of non-twisting somersaults using configuration changes

Theoretical analyses have shown that rotations of a rigid body about the principal axis corresponding to the intermediate principal moment of inertia are unstable. This poses a potential problem for gymnasts who perform double somersaults without twist in a layout configuration. A computer simulation model is used to investigate configurational strategies for controlling such movements. It is shown that the build up of twist is not reduced by abduction of the arms but can be controlled by adopting a configuration with sufficient body flexion. For somersaults with a straight body, control in the form of asymmetrical arm abduction accelerations, based upon twist angular velocity and angular acceleration, is capable of preventing a build up of twist providing that the feedback time delay is less than a quarter somersault.