油浆蒸汽发生器管板裂纹浅析

重油催化裂化装置中原油浆蒸汽发生器因管板出现裂纹而报废的情况,近几年来在国内油厂中频频发生,笔者结合胜利油田石油化工总厂3台油浆蒸汽发生器管板的裂纹情况对蒸汽发生器发及裂纹的原因进行了分析,并就如何避免裂纹的产生提出了几点建议。     

加氢裂化分馏塔航空煤油干点软测量

基于BP网络、RBF网络、PLS算法建立了加氢裂化分馏塔航空煤油干点软测量模型。在此基础上开发了BP-RBF-PLS的航空煤油干点软测量混合模型。在工业装置上投入运行,精度较高,为实现先进控制创造了条件。     

基于XML的STEP数据安全机制的研究

为了实现STEP格式的数据在网络上发布,引入了XML技术和密码技术。首先,建立了STEP与XML之间的一一映射关系,将STEP数据转换为XML文档,然后研究了XML文档的加密和签名机制,并给出了具体的应用实例。     

基于流量攻击和边失效的复杂网络脆弱特性

基于流量的攻击可能对复杂网络造成严重破坏,现有研究主要针对节点攻击。该文分析了部分边失效时,复杂网络的脆弱特性。此外,分析了时机策略和网络规模对边失效的影响。通过研究节点负载和度分布特点,发现复杂网络的脆弱特性源于其幂率度分布引起的节点负载的极度非均匀分布。仿真实验表明,复杂网络对随机的边失效具有较强的耐受力,但在一定条件下,攻击极少量重要边就可能引发连锁的节点过载失效,而导致网络溃散。     

地下矿山采场顶板厚度数值模拟研究

通过结构力学解析法对顶板沉降量的计算,估算出能维持顶板稳定的厚度取值范围,运用FLAC3D软件建立了开采环境再造采场数值模型,并对不同厚度顶板进行模拟计算,揭示了顶板厚度对采场稳定性、应力分布以及顶板沉降量的影响规律,表明了塑性区、应力扰动范围以及沉降量都随着顶板厚度的增加而减小,且减小的幅度趋缓。以顶板沉降量为判据,模拟结果得出,顶板厚度是6m时的最大沉降量为6.376cm,满足矿山安全要求;同时,兼顾顶板施工工艺、构筑成本和服务年限,得出顶板的最小安全厚度宜取6m。     

提供可靠服务的P2P流媒体点播系统

针对P2P流媒体点播的稳定性和可靠性问题,该文提出一种基于节点可靠度和服务质量评价的点播系统结构RP2MoD。节点根据父节点的失效概率计算自身可靠度,并在点播时对父节点的服务质量作评价。父节点的选择、媒体数据的分配策略以及容错和恢复处理均以此为基础。理论分析和仿真表明,系统具有较强的容错能力,能提供稳定可靠的点播服务,而增加的可靠度和服务质量的相关操作对系统性能影响甚微。     

疏水性白炭黑在硅橡胶海绵中的应用研究

研究了表面疏水处理对白炭黑在硅橡胶及其海绵材料中的分散效果及其增强作用的影响.研究表明:表面疏水处理改善了白炭黑在硅橡胶中的分散均匀性,提高了胶料的可塑性,有利于胶料发泡,使硅橡胶海绵的表现密度降低;而表观密度降低导致硅橡胶海绵的硬度、拉伸强度、延伸率、压缩应力松弛减小.     

Sorption of Pu(IV) in the polymeric colloidal form on rock typical of Mayak Production Association area

Sorption of colloids of polymeric Pu from simulated groundwater on a rock typical of Mayak Production Association area was studied. In 20 days, polymeric Pu with the particle size exceeding 220 nm is 99% sorbed by the rock with the distribution coefficient K _d = 1880. Desorption performed for 5 days allows no more than 40% of the sorbed Pu to be transferred into the solution, even with such strong complexing agents as 0.05 M hydroxyethylidenediphosphonic acid in 0.1 M HNO₃ and 0.1 M Tamm solution.     

Behavior of polymeric Pu(IV) in simulated groundwater

The effect of pH, ionic strength, and supporting electrolyte on the speciation of Pu(IV) in simulated groundwater over polymeric plutonium hydroxide at fixed values of the oxidation potential Eh was examined by centrifugal ultrafiltration. Upon dilution of simulated groundwater (SGW) containing highly polymerized polymeric Pu species of high molecular weight, these species transform into those with a lower degree of polymerization. When fresh SGW portions are subjected to ultrafiltration through a compact precipitate of colloidal Pu, this precipitate becomes a source of weakly polymerized Pu species, as in the case of common dissolution of a compact precipitate of colloidal Pu in SGW. In the process, the amount of weakly polymerized forms increases by two orders of magnitude as compared to the initial SGW over polymeric Pu hydroxide. These transformations of the initial Pu species in solutions can affect its migration behavior in subsequent processes.     

The Effects of Casting Temperature on the Glass Formation of Zr‐Based Metallic Glasses

The glass1‐forming ability of two alloys, Zr_64.9Al_7.9Ni_10.7Cu_16.5 and Zr₄₇Cu_37.5Ag_7.5Al₈, prepared by arc‐melting a mixture of Zr, Cu, Al, Ni and Ag elements is studied as a function of casting temperature. Other processing parameters such as the alloy melt mass, and the vacuum and injection pressures during the copper‐mold‐casting process are kept constant so just the influence of the casting temperature is considered. The casting temperature determines the characteristics of the liquid melt and the cooling rate. The glass‐forming ability is discussed in terms of dissipation of pre‐exiting, metastable local‐ordering clusters that act as nucleation sites promoting crystallization, the cooling rate at high casting temperatures, and the presence of oxygen in the alloys, which is increased at high casting temperatures. It is found that the glass‐forming ranges of alloys shrink as the glass‐forming size approaches a critical value. The optimum temperatures are around 1450 K and 1550 K for Zr_64.9Al_7.9Ni_10.7Cu_16.5 and Zr₄₇Cu_37.5Ag_7.5Al₈ alloys respectively. The alloys were studied by XRD, TEM, oxygen‐level determination, and DSC.