新型金刚石链锯的链条受力分析

文章对用于大板切割新型金刚石链锯的链条张力进行了分析计算,由计算结果可知,新型金刚石链锯链条张力在试验装置条件下紧边张力为1705N,松边张力为1639N,且张力随着链轮直径的增加而减小;并由此计算并绘出了新型金刚石链锯链条围齿区整体受力分布图,由图可知,两轮结构下最大链条受力点为链条紧边最先与主动链轮啮合处。     

大型链板式斗提机斗链的快速更换方法

根据硫基复合肥大型斗提机斗链更换的实践,介绍快捷、高效、合理更换斗链的新方法,只需3d即可完成(过去6d)更换。     

中央链提升机链条国产化替代经验交流

1 提升机情况简介 我公司一线始建于1999年,由成都水泥工业设计研究院有限公司设计、中材建设有限公司总包,是国内水泥行业第一条交钥匙总包项目.该生产线的主机设备均选用进口产品,其中生料入库提升机选用的是德国AUMUND公司的产品,该提升机链条采用的是模锻中央链条,从2001年投入运行后,链条连续使用了15年,自201...     

Role of chain length in degradation process (chain breakdown)

The role of molecular weight of a chain in the chain breakdown in diluted solution at a constant concentration of chain molecules and constant temperature is discussed theoretically using the methods of the theory of the activated complex and kinetics of cooperative processes. The reaction starts at the certain molecular weight of the chain. The chain breakdown is the flat increasing function of the chain molecular weight. This function has a limit when chain molecular weight approaches infinity. Such dependence is explained by the increase of flexibility (following two theories) and increase of extra entropy of molecules of different sizes (following kinetics of cooperative processes. Unequal reactivity of chemically identical active centers links to the dependence of chain flexibility on the location of the more flexible part (place of reaction) of the chain. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1810–1817, 2002; DOI 10.1002/app.10356     

A lattice chain model for the thermal restructuring of nanoparticle chain aggregates

Chain aggregates composed of nanoparticles of carbon black, silica, titania and other metal oxides are produced commercially using aerosol reactors. Properties of nanoparticle chain aggregates (NCA), such as restructuring when heated in gaseous suspension, may play an important role during synthesis. It is hypothesized that in some cases a separate step in NCA creation is the restructuring of the chains initially formed by rigid body addition processes, for example cluster–cluster aggregation. A model of a freely rotating bead chain (zero activation energy for particle rotation) is adapted here from the polymer literature to describe nanoparticle chain restructuring resulting from interaction with the surrounding gas. The link between the physical properties of the surrounding gas and the dynamics of the nanoparticle chain is provided through the diffusion coefficient of the chain center of mass. We have studied the restructuring dynamics for primary particles of various diameters, different chain lengths and at different temperatures, and the model predicts a fast transition from a non-equilibrium initial chain configuration to a relaxed state. For a stretched chain of 64 particles, each 35 nm in diameter, in air at 1800 K and atmospheric pressure, the characteristic time for relaxation was 0.34 ms. This time is consistent with a 12 ms upper limit in restructuring time for soot aggregates reported in the literature. It is possible that in practice the approach to equilibrium may be delayed by constraints on particle rotation.     

Real-time polymerase chain reaction

Real-time PCR is the state-of-the-art technique to quantify nucleic acids for mutation detection, genotyping and chimerism analysis. Since its development in the 1990s, many different assay formats have been developed and the number of real-time PCR machines of different design is continuously increasing. This review provides a survey of the instruments and assay formats available and discusses the pros and cons of each. The principles of quantitative real-time PCR and melting curve analysis are explained. The quantification algorithms with internal and external standardization are derived mathematically, and potential pitfalls for the data analysis are discussed. Finally, examples of applications of this extremely versatile technique are given that demonstrate the enormous impact of real-time PCR on life sciences and molecular medicine.     

氢氰酸产业链

依据合成路线,将氢氰酸下游主要产品归纳为羟基乙腈、氰化钠、丙酮氰醇、氯化氰和精制氢氰酸五大产业链,系统介绍了五大产业链下游产品市场和技术情况。     

Sphingolipid long chain bases

About 60 natural sphingolipid long chain bases have been identified or proposed. A review is given on their nomenclature, distribution, metabolism, biologic properties, chemistry and methods of characterization.     

支链硅油

概述了支链硅油的定义、结构、特性及表征方法；并根据三官能链节(T链节)的来源，介绍了5种制备支链硅油的方法；最后，介绍了支链硅油在化妆品、防粘隔离剂、低温液力传动油中的应用。     

Phytosterol side chain biosynthesis

The typical plant sterols contain a substituent at C-24 of the side chain. This can be a methylene, ethylidene, methyl, or ethyl group; with the last three groups, all possible isomers have been reported in nature. The C-24 alkyl groups are derived by a transmethylation reaction from methionine. The details of several distinct alkylation mechanisms, which are now recognized in a range of lower and higher plants, have been reviewed. The operation of these different routes may have some phylogenetic significance. One of eight papers presented in the symposium “Phytosterols,” AOCS Spring Meetin, New Orleans, April 1973.     

The origin of chain entanglement: Correlations between entanglement and chain structure

A pseudotopological theory of chain entanglement has recently been developed, which shows that the entanglement junction is a binary hooking contact between two chains, and explicitly relates the entanglement behavior to chain structure. On the other hand, many empirical correlations between entanglement and chain structure have also been proposed to date, including those of Fox and Allen, Porter and Johnson, Privalko and Lipatov, Boyer and Miller, Graessley and Edwards, Aharoni, Lin, and Zang and Carreau. In this work, we show that the various empirical equations cited are variations of the same function, and can be derived as special cases from the theoretical pseudotopological equation. The various forms of the function nevertheless reveal different essential aspects of the chain entanglement behavior, and show that the traditional hooking view of chain entanglement is correct, and also provides a basis for the recent reptation-tube model.     

中双链刮板输送机复合断链检测系统的设计

中双链刮板输送机其机槽较宽且输送量大,其断链事故所带来的影响不言而喻。减小断链所造成的破坏程度和降低事故后的维修难度直接影响着企业的生产效率。目前本领域的断链检测较为单一,响应不够及时,可靠性有待考量。应用于中双链刮板输送机、通过多种组合、结合刮板输送机的结构点,可灵活布置的复合式断链检测系统,提高断链事故发生时响应速度,大大增加了断链检测的及时性,减小因断链带来的破坏和损失,为刮板输送的智能生产和在线监测提供一种可靠方法。     

Average increase in chain length of crystalline long chain compounds per carbon atom

A comprehensive survey has been made of published crystal X-ray diffraction data in order to select an authentic overall value ford ₉₀, the average increase in chain length of crystalline long chain compounds per carbon atom, for general use in calculating angle of tilt. Data were available for 10 isomorphous homologous series including the normal hydrocarbons, alkanoic acids, primary alcohols, ketones, dicarboxylic acids, symmetrical saturated triglycerides, potassium acid salts, quarter-hydrates of Na-1-alkanesulfonates, hydrazides and the dihydrazides of dicarboxylic acids. The results, supported by data for other specific long chain derivatives show that (a) 1.27 Å is the best value for this constant, and (b) there is no justification for the value 1.30 Å, which has been used in the recent literature as the accepted value in estimating the angle of tilt. The information developed can be used to predict the effective length of one molecule in the crystal of any specific long chain member of any of the homologous series studied.     

扩链剂联用技术对PET扩链反应的影响

通过对PET扩链反应前后的特性粘数 [η]和羧基 [COOH]值的比较 ,讨论了扩链剂联用条件下不同扩链剂种类、用量以及加入方式对于扩链反应的影响。实验结果表明 ,扩链剂联用对于PET树脂增粘是一个良好的方法 ,可使扩链产物的特性粘数由 0 .62dL g增至 1.1dL g ,同时 [COOH]含量降至很低 ;少量荧光剂同时加入显著改善扩链产物的色泽。在一定的联用条件下扩链产物的热稳定性可保持在较好水平。     

Properties of side chain liquid crystal polyesters containing chiral groups in the main chain

The synthesis and investigation are reported for the phase behavior of a set of three liquid-crystalline side chain polyesters (SCLCPs), consisting of aromatic diacids and diols bearing cyano biphenyl moieties in the side chain. The materials contain a chiral center in the main chain and show a cholesteric phase indicative of a helical order with a preferred twist. In addition, they exhibit T_g's below room temperature and smectic bilayer phases. Depending on the substitution pattern of the aromatic core, S_c* or S_A* phases are observed. These polymers were synthesized in a four-step synthesis, starting from available materials. The dielectric relaxation behavior and the pyroelectric responses of the three SCLCPs tend to conform to their respective structure.     

Extended chain lamellae self-assembled in liquid crystal phase of soluble polydiacetylenes through chain segregation

This review article highlights our efforts in the past years toward a fundamental understanding of the supramolecular structures of a soluble but rigid polydiacetylene. In our earlier works we presented evidence to indicate that this polymer formed a lyotropic phase in solutions. TEM, AFM and SEM observations on solidified thin films showed an extended chain lamellar structure which is surmised to be self-assembled in the lyotropic phase through chain segregation. Our results revealed that the supramolecular structures formed are closely associated with the structures formed in the lyotropic state. Due to three attributes of rigid macromolecules at the molecular level-high molecular weight, broad molecular weight distribution, and worm-like chain conformation, the supramolecular structures observed are also greatly different from those of conventional nematics or smectics. Dedicated to Professor Dr. Gerhard Wegner, Max-Planck-Institute for Polymer Research, Germany, together with my wishes on the occasion of his 60^th birthday.     

短链和长链交联剂对水性聚氨酯性能的影响

采用不同链长的交联剂三羟甲基丙烷(TMP)、蓖麻油(CTO)和改性蓖麻油(MCO),通过预聚体混合法合成了3种内交联的水性聚氨酯(WPU)分散液。借助激光粒度分析仪、电子拉力试验机和热失重分析详细研究了不同链长交联剂对WPU乳液和胶膜性能的影响。研究结果表明:TMP交联的WPU具有较小的平均粒径和较窄的粒度分布,其胶膜具有较好的力学性能和耐热性;CTO交联的WPU则具有较大的粒径和较宽的粒度分布,但其胶膜具有更好的耐水性;MCO交联的WPU胶膜具有更高的相混合程度和最高的吸水率。