低温工况甲烷最小点火能实验研究

为探索低温工况下甲烷的爆炸特性,利用自行构建的实验装置,测试了温度为-90~0 ℃、压力为0.1~0.5 MPa的条件下甲烷的最小点火能。研究表明:在研究范围内,随着压力的升高,甲烷的最小点火能减小,且低压时甲烷最小点火能随初始压力的增高减小较快,高压时减小较慢;随着温度的升高,甲烷最小点火能也减小,且低压时甲烷最小点火能随初始温度的增高减小较快,高压时减小较慢;甲烷的最小点火能分别与压力平方的倒数、温度的倒数呈近似线性关系。     

Three new mixed‐ligand copper(II) complexes containing glycyl‐l‐valine and N,N‐aromatic heterocyclic compounds: Synthesis,characterization, DNA interaction,cytotoxicity and antimicrobial activity

Three novel copper(II) complexes, [Cu(Gly‐l ‐Val)(HPBM)(H₂O)]·ClO₄·H₂O ( 1 ), [Cu(Gly‐l ‐Val)(TBZ)(H₂O)]·ClO₄ ( 2 ) and [Cu(Gly‐l ‐Val)(PBO)(H₂O)]·ClO₄ ( 3 ) (Gly‐l ‐Val = glycyl‐l ‐valine anion, HPBM = 5‐methyl‐2‐(2′‐pyridyl)benzimidazole, TBZ = 2‐(4′‐thiazolyl)benzimidazole, PBO = 2‐(2′‐pyridyl)benzoxazole), have been prepared and characterized with elemental analyses, conductivity measurements as well as various spectroscopic techniques. The interactions of these copper complexes with calf thymus DNA were explored using UV–visible, fluorescence, circular dichroism, thermal denaturation, viscosity and docking analyses methods. The experimental results showed that all three complexes could bind to DNA via an intercalative mode. Moreover, the cytotoxic effects were evaluated using the MTT method, and the antimicrobial activity of these complexes was tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The results showed that the activities are consistent with their DNA binding abilities, following the order of 1 > 2 > 3 .     

PRODUCTION, ISOLATION AND SPECTROSCOPIC STUDIES OF THE ENDOHEDRAL FULLERENE Sc_2@C_(80)(I-III)

Introduction C80 and C80-based endohedral metallofullerenes (named as Mn@C80 hereafter) have attracted extensive attention due to their special properties. C80 has an extremely low abundance in soot produced by arc discharge and it is only until recently that two isomers of C80(D2) were isolated by Kappes (Hennrich et al., 1996) and us (Wang et al., 2000). In contrast, some Mn@C80 have a relatively high abun-dance and so far the isolation of Mn@C80 has been achieved for both dimetallofull…     

Analytical/experimental investigation of energy absorption in grid-stiffened composite structures under transverse loading

In this paper we summarize preliminary results from an analytical/experimental study of the energy absorption characteristics of grid-stiffened composite structures under transverse loading. Tests and quasi-static finite element analysis simulations were carried out for isogrid E-glass/polypropylene panels in three-point bending. The results of the tests and simulations show that these types of structures have excellent damage tolerance and that most of the energy absorption occurs beyond initial failure. It is also observed that even though the peak load is greater for loading on the skin side, the specific energy absorption and the range of displacements over which energy is absorbed are significantly better when the load is applied on the rib side.     

基于能量法的多轴疲劳寿命预测方法

多轴疲劳寿命预测对于确保工程构件的安全性及经济性具有重要意义,其中损伤参量的选取对于预测结果的精度具有关键影响作用.Smith-Watson-Topper (SWT)能量参数是目前常用的损伤参量,但由于仅考虑了拉伸应变能对材料损伤的贡献,因此其常做出偏于危险的预测结果.针对此问题,Glinka及Chen-Xu-Huang (CXH)能量参数被相继提出.然而试验验证表明:Glinka参数通常仅适用于以剪切型失效为主要失效模式的材料,CXH参数则易给出过于保守的预测结果.为提高SWT参数对各种材料与加载路径的适用性,论文在评估Glinka及CXH参数的基础上,提出了两个修正的SWT能量参数,并建立起了一个统一的多轴疲劳寿命预测模型.针对不同的疲劳失效形式,所提出的能量参数不仅可考虑平均应力效应,且可同时包括临界面上不同加载方向对材料损伤的影响.通过六种材料的多轴疲劳试验数据对新模型、SWT模型、Glinka模型及CXH模型进行了验证,结果显示新模型比其他三种模型具有更好的寿命预测精度及稳定性.     

截锥形弹体在液体介质中运动速度衰减规律分析

水面舰船被动防护体系中液舱的主要功能之一是阻止高速弹体（爆炸破片）对内部重要结构、设备和人员的威胁,高速弹体打击液舱的过程包含着复杂的能量传递与耗散。为了分析弹体形状对其在液体介质中运动速度衰减的影响, 开展了一系列不同头形因数的截锥形弹体在不同入水速度下弹体垂直侵彻液体介质过程的数值模拟,得到了垂直侵彻液体介质时弹体速度衰减特性,发现高速弹体在液体介质中运动的阻力因数与弹体形状和无量纲速度有关。基于对系列数值模拟计算结果的拟合分析,提出了计及头形因数的截锥形弹体 垂直侵彻液体介质时的速度衰减经验公式,通过开展数值算例分析验证了公式计算结果的可靠性。本文中提出的经验公式可实现对高速弹体在液体介质中速度衰减的准确快速计算,为舰船防护液舱结构设计提供一定的参考。     

A numerical study on a Cartesian-based body-fitted adaptive grid method

ABSTRACT

A hybrid Cartesian-based body-fitted adaptive grid method for compressible Navier–Stokes equations is implemented and investigated. In this method, the body-fitted structured grids are generated around the geometries, and the left regions are filled with Cartesian grids. To transfer the data between the different grids, the donor cell searching technique is adopted. An unstructured data-based finite volume update procedure is used, and least squares method is suggested to retain the second order in the overlap region. The moving shock waves with different speeds and vortex passing through the interfaces of the hybrid Cartesian grid are used to explore the accuracy and conservation. A new technique is presented to deal with the non-physical stagnation of slowly moving shock wave around the interface of grid. Numerical examples are presented to demonstrate the results. The three-dimensional extension has also been shown by a benchmark problem.     

酸性媒染紫-示波计时电位法测定天然水和饮用水中铝

报道酸性媒染紫（ＳＶＲＳ）－示波计时电位法测定天然水及饮用水中铝。在０．８５ｍｏｌ／Ｌ　ＮＨ３·Ｈ２Ｏ－ＮＨ４Ｃｌ－５×１０－５ｍｏｌ／Ｌ ＳＶＢＳ（ｐＨ８．８）底液中,Ａｌ－ＳＶＲＳ络合物在－１．０５Ｖ电位处产生灵敏切口,切口深度与铝浓度成正比,可用于定量分析。线性范围为１×１０－７～６×１０－６ｍｏｌ／Ｌ． ＲＳＤ为５．５％ （ｎ＝１０,２×１０－７ｍｏｌ／Ｌ）,检测限为５×１０－８ｍｏｌ／Ｌ。本法特点为：在碱性条件下,无需加热,无需通氮除氧,无需预富集,大大减少了分析时间。仪器简单,方法灵敏准确,特别适用于天然水和饮料中Ａｌ的分析。对实际水样进行了分析,与ＩＣＰ／ＡＥＳ法所测结果基本一致。     

Polymerization of styrene with ionic comonomer,nonionic comonomer,or both

Nanosized polystyrene latexes with high polymer contents were obtained from an emulsifier-free process by the polymerization of styrene with ionic comonomer, nonionic comonomer, or both. After seeding particles were generated in an initial emulsion system consisting of styrene, water, an ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2-hydroxyethyl methacrylate (HEMA)], and potassium persulfate, most of the styrene monomer or a mixture of styrene and HEMA was added dropwise to the polymerizing emulsion over 6 h. Stable latexes with high polystyrene contents (≤25%) were obtained. The latex particle weight-average diameters were largely reduced (41 nm) by the continuous addition of monomer(s) compared with those (117 nm) obtained by the one-pot polymerization method. Latex particles varied from about 30 to 250 nm in diameters, whereas their molar masses were within 10⁴ to 10⁵ g/mol. The effect of the comonomer concentration on the number of polystyrene particles per milliliter of latex and the weight-average molar masses of the copolymers during the polymerization are discussed. The surface compositions of the latex particles were analyzed by X-ray photoelectron spectroscopy, which indicated that the surface of the latex particles was significantly enriched in NaSS, HEMA, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1634–1645, 2001     

Cytotoxic Withaphysalins from Physalis minima

A novel withanolide, withaphysalin P ( 1 ) with a nine‐membered ring, and six other new withaphysalins, 2 – 7 , together with the three known withaphysalins 8 – 10 were isolated from Physalis minima L. The structures were deduced by means of spectroscopic analyses, and that of withaphysalin P ( 1 ) was confirmed by a single‐crystal X‐ray diffraction analysis. Plausible biosynthetic pathways were postulated (Scheme 1). All compounds were tested for their antiproliferative activities toward the human colorectal‐carcinoma HCT‐116 cells and human nonsmall‐cell lung‐cancer NCI‐H460 cells (Table 4). Compounds 1 – 3, 7 – 10, 7a , and 7b displayed moderate cytotoxic activity against the two human cancer cell lines.