国产十字轴式万向接轴在3500mm中厚板轧机上的应用

针对滑块式万向接轴因润滑效果差、滑块磨损较快、传动效率低而制约产品质量和高附加值产品的开发等问题，在轧机辊端应用国产十字轴式万向接轴，从而提高系统的传动精度和效率，降低综合成本。实现了十字轴式万向接轴在大型中厚板轧机主传动轴上的国产化应用。     

滑块式万向接轴的改造

介绍了对传统滑块式万向接轴的结构改造和轧辊侧滑块干油润滑方式改造，改造后的接轴寿命和润滑等方面都有突破性提高和改善，已获国家专利。通过比较，建议用户对目前在重载低速轧机上使用的传统滑块式万向接轴进行改造，不要急于换成十字头式万向接轴。     

鞍钢中板厂劳特式轧机万向接轴的优化设计

本文根据等强度的原则，建立了滑块式万向接轴优化设计的数学模型，并对劳特式轧机万向接轴进行了优化设计，确定出量佳设计参数，使接轴整体综合承载能力在一定程度上得到了提高。对万向接轴的技术改造具有重要的意义。     

大型滑块式万向接轴模块化结构改进

滑块式万向接轴在轧钢设备中广泛应用,但常见结构接轴制造工艺复杂、制造成本高。介绍了滑块式万向接轴的结构特点,阐述了现有结构在制造、维修及使用过程中存在的问题,提出了接轴模块化结构改进方案。     

中板轧机滑块式万向接轴自动润滑装置研制

介绍一种用于中板轧机滑块式万向接轴的自动润滑装置。当轧机旋转时 ,固定在万向接轴平衡托瓦上的模板使固定在万向接轴上柱塞泵内的数个柱塞做往复运动 ,万向接轴旋转一周柱塞泵完成吸油和压油一个周期 ,柱塞泵压出的干油通过固定在万向接轴上的油管送至滑块与扁头或滑块与叉头摩擦表面 ,为摩擦表面提供良好的润滑条件 ,以避免滑块的发热和烧毁现象     

3500精轧机辊端接轴的改造

针对济钢中厚板厂3500精轧机辊端滑块联轴器经常断裂,使用周期过短,严重影响生产,经过对接轴处进行研究和优化,最终决定把滑块式改为交错式十字万向接轴,经过半年时间的应用,交错式十字万向接轴工作可靠,寿命长,值得借鉴.     

1422轧机滑块式万向接轴的故障及处理

以热轧板厂粗轧主传动滑块式万向接轴为例，分析了该接轴及接轴平衡机构的常见故障及其排除方法，提出了日常维护措施。     

滑块式万向接轴的无损检测方法

本文介绍了滑块式万向接轴的无损检测方法。     

大型轧机主传动万向接轴结构的分析与改造

通过研究中厚板轧机主传动万向接轴的结构形式,对接轴存在的轴向窜动余量过小、接轴平衡连杆强度低等问题进行了整体改造,重新设计万向接轴结构和平衡龙门架,用十字轴式接轴代替虎口滑块式接轴,达到了轧机稳定、高效运行的目的。     

十字轴式万向接轴正确安装的理论推导

十字轴式万向接轴中间轴两端叉形零件安装布置的不合理，会引起速度的不稳定－周期性异常振动，本文通过对十字轴式万向接轴的工作原理及其特性的分析，论证了什么样的安装布置是正确的。     

Restriction map polymorphism in the forked and vermilion regions of Drosophila melanogaster

Restriction map polymorphism at two X linked foci, forked and vermilion of Drosophila melanogaster was studied in three natural populations. The estimates of nucleotide variation were theta = 0.003 and pi = 0.002 for the forked region and theta = 0.004 and pi = 0.002 for the vermilion region. Three insertions (> 500 bp) were observed at each locus. Typical of other regions of this species each of these large insertions was unique in the sample. Non-random association among polymorphisms was common at the vermilion locus, while the forked locus was not polymorphic enough to test linkage disequilibrium. The amounts of restriction site and size variation in the vermilion and forked were within the range observed for other loci of D. melanogaster.     

基于 Solidworks 的万向接轴断裂事故的技术分析

对万向接轴的断裂事故进行了分析。重点是对专用万向接轴叉头做了有限元分析,求得了它的应力分布及最大应力值。还对轧辊在咬入急停而造成的冲击性动力载荷作了具体计算,计算了在可能情况下最大的实际载荷和最大应力,从而解释了万向接轴叉头部件断裂的起因,提出了设备设计和使用方面的改进意见。     

Two New Fossil Lacewing Species from the Middle Jurassic of Inner Mongolia, China (Neuroptera: Grammolingiidae)

Two new species of lacewings are described and illustrated from the Jiulongshan Formation (Middle Jurassic) of Inner Mongolia, China: Leptolingia calonervis sp. nov. and Litholingia ptesa sp.nov. (Grammolingiidae). The species can be distinguished by the following features: the outermost branch of MP2 on the hind wing did not reach the margin of wing in Leptolingia calonervis sp. nov.;the second branch of Rs forked deeply while other branches of Rs forked much later in Litholingia ptesa sp. nov..     

Structure-specific DNA binding by bacteriophage T5 5'-->3' exonuclease

Phage T5 exonuclease is a 5'-->3'exodeoxyribonuclease that also exhibits endonucleolytic activity on flap structures (branched duplex DNA containing a free single-stranded 5'-end). Oligonucleotides were used to construct duplexes with either blunt ends, 5'-overhangs, 3'-overhangs, a flap or a forked end (pseudo-Y). The binding of T5 exonuclease to various structures was investigated using native electrophoretic mobility shift assays (EMSA) in the absence of the essential divalent metal cofactor. Binding of T5 exonuclease to either blunt-ended duplexes or single-stranded oligonucleotides could not be detected by EMSA. However, duplexes with 5'-overhangs, flaps and pseudo-Y structures showed decreased mobility with added T5 exonuclease. On binding to DNA the wild-type enzyme was rendered partially resistant to proteolysis, yielding a biologically active 31.5 kDa fragment. However, the protein-DNA complex remained susceptible to inactivation by p-hydroxymercuribenzoate (PHMB, a cysteine-specific modifying agent), suggesting that neither cysteine is intimately associated with substrate binding. Replacement of both cysteine residues of the molecule with serine did not greatly alter the catalytic or binding characteristics of the protein but did render it highly resistant to inhibition by PHMB.     

Molecular characterization of the complete 23F capsular polysaccharide locus of Streptococcus pneumoniae

The complete DNA sequence of the capsular locus 23F of Streptococcus pneumoniae is presented. The 18.6-kb cps23f locus is composed of 18 open reading frames flanked at the 5' and 3' ends by the genes dexB and aliA, an arrangement similar to those of some of the other identified cps loci.     

The terminal DNA structure of mammalian chromosomes

In virtually all eukaryotic organisms, telomeric DNA is composed of a variable number of short direct repeats. While the primary sequence of telomeric repeats has been determined for a great variety of species, the actual physical DNA structure at the ends of a bona fide metazoan chromosome with a centromere is unknown. It is shown here that an overhang of the strand forming the 3' ends of the chromosomes, the G-rich strand, is found at mammalian chromosome ends. Moreover, on at least some telomeres, the overhangs are > or = 45 bases long. Such surprisingly long overhangs were present on chromosomes derived from fully transformed tissue culture cells and normal G0-arrested peripheral leukocytes. Thus, irrespective of whether the cells were actively dividing or arrested, a very similar terminal DNA arrangement was found. These data suggest that the ends of mammalian and possibly all vertebrate chromosomes consist of an overhang of the G-rich strand and that these overhangs may be considerably larger than previously anticipated.     

35t/h煤气锅炉凝渣管壁穿孔故障分析

35t/h链条炉在改造成同参数煤气锅炉中，为增加受热面积，凝渣管设计成叉形管形式，运行55天后出现3处穿孔。其原因是凝渣管内工质分配不合理，产生汽塞、汽水分层过热而发生蒸汽腐蚀和NaOH液滴腐蚀。取消了叉形管的弯管部位，运行至今状态良好。     

The symmetrical structure of structural maintenance of chromosomes (SMC) and MukB proteins: long, antiparallel coiled coils, folded at a flexible hinge

Structural maintenance of chromosomes (SMC) proteins function in chromosome condensation and several other aspects of DNA processing. They are large proteins characterized by an NH2-terminal nucleotide triphosphate (NTP)-binding domain, two long segments of coiled coil separated by a hinge, and a COOH-terminal domain. Here, we have visualized by EM the SMC protein from Bacillus subtilis (BsSMC) and MukB from Escherichia coli, which we argue is a divergent SMC protein. Both BsSMC and MukB show two thin rods with globular domains at the ends emerging from the hinge. The hinge appears to be quite flexible: the arms can open up to 180 degrees, separating the terminal domains by 100 nm, or close to near 0 degrees, bringing the terminal globular domains together. A surprising observation is that the approximately 300-amino acid-long coiled coils are in an antiparallel arrangement. Known coiled coils are almost all parallel, and the longest antiparallel coiled coils known previously are 35-45 amino acids long. This antiparallel arrangement produces a symmetrical molecule with both an NH2- and a COOH-terminal domain at each end. The SMC molecule therefore has two complete and identical functional domains at the ends of the long arms. The bifunctional symmetry and a possible scissoring action at the hinge should provide unique biomechanical properties to the SMC proteins.     

Asymmetric interactions of hexameric bacteriophage T7 DNA helicase with the 5'- and 3'-tails of the forked DNA substrate

Bacteriophage T7 DNA helicase requires two noncomplementary single-stranded DNA (ssDNA) tails next to a double-stranded DNA (dsDNA) region to initiate DNA unwinding. The interactions of the helicase with the DNA were investigated using a series of forked DNAs. Our results show that the helicase interacts asymmetrically with the two tails of the forked DNA. When the helicase was preassembled on the forked DNA before the start of unwinding, a DNA with 15-nucleotide (nt) 3'-tail and 35-nt 5'-tail was unwound with optimal rates close to 60 base pairs/s at 18 degrees C. When the helicase was not preassembled on the DNA, a >65-nt long 5'-tail was required for maximal unwinding rates of 12 base pairs/s. We show that the helicase interacts specifically with the ssDNA region and maintains contact with both ssDNA strands during DNA unwinding, since conversion of the two ssDNA tails to dsDNA structures greatly inhibited unwinding, and the helicase was unable to unwind past a nick in the dsDNA region. These studies have provided new insights into the mechanism of DNA unwinding. We propose an exclusion model of DNA unwinding in which T7 helicase hexamer interacts mainly with the ssDNA strands during DNA unwinding, encircling the 5'-strand and excluding the 3'-strand from the hole.     

轧机万向接轴叉头断裂失效分析

某轧机万向接轴叉头断裂后,造成停机时间较长,直接影响正常生产。为减少或者避免今后重复故障的发生,针对断裂的叉头进行失效分析。主要从材料成分、力学性能、断口显微组织等方面开展失效分析。