高压扭转Cu试样微观组织的热稳定性分析

通过高压扭转对Cu试样施加不同程度的变形,利用OM,TEM及差示扫描量热仪(DSC)对变形组织微观结构及其热稳定性进行了分析.在较小的变形程度下,变形组织为高位错密度的位错胞、亚晶组织,试样的变形储能随变形量的增大而增大,在切应变等于13时达到最大,为0.91 J/mol,DSC曲线显示的放热峰随变形量的增大向低温方向偏移;进一步变形,动态回复加剧,高位错密度的亚晶组织逐渐演化成无位错的等轴状晶粒组织,试样的变形储能减小,组织的稳定性提高.显微硬度随退火温度的提高而减小,晶粒的明显长大导致显微硬度急剧减小.出现明显晶粒长大的温度较DSC曲线显示的放热峰起始温度低45℃左右,这主要是由于变形组织的回复再结晶过程是退火温度与时间的函数,降低处理温度并延长处理时间能达到与高温短时处理相同的效果.

Study on the Mechanism of Detonation to Quasi-detonation Transition

In this paper, the mechanism of detonation to quasi-detonation transition was discussed, a new physical model to simulate quasi-detonation was proposed, and one-dimensional theoretical and numerical simulation was conducted. This study firstly demonstrates that the quasi-detonation is of thermal choking. If the conditions of thermal choking are created by some disturbances, the supersonic flow is then unable to accept additional thermal energy, and the CJ detonation becomes the unstable quasi-detonation precipitately. The kinetic energy loss caused by this transition process is firstly considered in this new physical model. The numerical results are in good agreement with previous experimental observations qualitatively, which demonstrates that the quasi-detonation model is physically correct and the study are fundamentally important for detonation and supersonic combustion research.

环境中氧含量水平对细胞辐射敏感性的影响

<正>为了找到环境中氧含量水平对细胞辐射敏感性的影响,我们选取人正常肝细胞系L02、肝癌细胞系SMMC-7721和黑色素癌细胞系A375在分别在氧含量10%、21%(正

从气候标准的改变分析西北地区的气候变化

IEECAS SKLLQG

表层土壤中菲的紫外光降解研究

多环芳烃化合物(PAHs)由于致癌、致畸和致突变而受到广泛关注。本实验以多环芳烃菲(Phe)为目标污染物,研究了温度、腐植酸和紫外辐射强度对Phe光降解的影响并对不同因素对降解动力学的影响作了研究。结果表明,Phe的降解在20℃到30℃范围内,随着温度的升高,光降解率增加;腐植酸在Phe污染土壤的光降解中起敏化作用,可显著促进光解,腐植酸浓度为5mg·kg-1足以达到敏化的效果;Phe光降解速率常数随辐射强度的降低而降低,呈正相关,光解的半衰期随着辐射强度的降低而增加,呈负相关。

Separation of peptides by pressurized capillary electrochromatography

A pressurized electrochromatography (pCEC) instrument with gradient capability was used in this work for separation of peptides. Three separation modes, namely, pCEC, high-performance liquid chromatography and capillary electrophoresis can be carried out with the instrument. In pCEC mode, the mobile phase is driven by both electroosmotic flow and pressurized flow, facilitating fine-tuning in selectivity of neutral and charged species. A continuous gradient elution can be carried out conveniently on this instrument, which demonstrates that it is more powerful than isocratic pCEC for separation of complicated samples. The effects of applied voltage, supplementary pressure and ion-pairing agents on separation of peptides in gradient pCEC were investigated. The effects of flow-rate of the pump and the volume of the mixer on resolution were also evaluated. (C) 2002 Elsevier Science B.V. All rights reserved.

Structure of an unexpected trimer from the reaction of ageratochromene II with aluminum chloride

A new trimer from the reaction of ageratochromene [1] (6,7-dimethoxy-2,2-dimethyl-1-benzopyran) with anhydrous aluminum chloride was shown to be 3,4-dihydro-6,7-dimethoxy-2,2-dimethyl-3-(6',7'-dimethoxy-2',2'-di-methyl-2H-1-benzopyran-4'-yl)-4-(3" 4"-dihydro-6", 7"-dimethoxy-2",2"-dimethyl-2H-1-benzopyran-3"-yl)-2H-1-benzopyran. Its structure was confirmed by NMR (H-1, C-13, DEPT-135. COSY, HMBC, HSQC, TOCSY and NOESY), IR, mass spectra and elemental analysis. Copyright (C) 2002 John Wiley Sons, Ltd.

绿洲前沿地区多枝柽柳水分关系的特征及灌溉的影响

对塔克拉玛干沙漠南缘策勒绿洲前沿地区多枝柽柳 (Tamarixramosissima)进行了研究 ,生长季节和灌溉前后水分关系的特征表明 :多枝柽柳在生长季节保持了较高较稳定的清晨水势 ,植物能够平衡白天水分损失造成的水分亏缺 ,水分恢复状况良好。环境气候变化对渗透势等水分参数的影响不及植物水分恢复状况对它们的影响。除了个别数据 ,多枝柽柳水势和渗透势的降低幅度很小 ,更像是生长过程的结果 ,植物水分胁迫的特征并不明显。对比水分生理上对干旱胁迫的适应———渗透势的迅速降低和质外体水含量的增加 ,膨压消失点相对含水量(RWCp)和渗透势差值 (ΔΠ)等参数显示的生理特征表明 ,植物更加依靠稳定充足的水分供应来适应生长环境中极端的高水压差和与此相应的高大气蒸发要求。与此适应 ,植物和地下水发生了联系 ,并且一次性灌溉对植物水分状况的恢复基本没有帮助 ,保持地下水位稳定在根系的可吸收范围内成为保护绿洲前沿多枝柽柳长期存在的关键。多枝柽柳的水分特征属于中生植物的范畴 ,对极端环境的适应属于躲避的类型。

森林叶凋落物混合分解的研究I.缩微(Microcosm)实验

采用缩微实验法 ,初步系统研究了杉木叶凋落物分别与火力楠、红栲和木荷 3个阔叶树种之一的叶凋落物两两混合分解的动态变化 ,以探明凋落物混合分解过程中可能存在的相互作用 .结果表明 ,杉木叶凋落物与 3种阔叶树种叶凋落物两两混合分解时所表现出不同的相互作用形式 :杉木与木荷表现出抑制作用 ,杉木与红栲或火力楠表现为较弱的促进作用 .

天山北坡中段自然生态系统服务功能价值研究

以位于阜康市的天山北坡中段自然生态系统为研究对象,采用市场价格法、影子价格法、成本核算法、收益损失法等多种生态系统服务功能价值的研究方法,从直接使用价值和就间接使用价值两方面,对这里的生态系统服务功能价值进行了估算。结果表明,这里生态系统服务功能价值达6.32×108元人民币。其中有机物生产4.3016×1012元,涵养水源2.406×108元,观光旅游8.000×108元,土壤保护7.334×108元,调节大气成分4.951×108元,净化空气6.7152×108元,旅游收入8.0×108元,山地草甸1.38×108元。