从单一多位交换~(119)Sn二维交换谱求取SnCl_6~(2-)水解体系的动态交换速率常数

本文对如何从单一二维交换谱提取速率常数进行了理论分析,提出了一种近似处理方法,即把较短混合时间τ_m内在二维平面上磁化强度传递看成是单向进行的,进而导出了二维交换谱中所有峰强随τ_m变化的表达式。所得结果与Ernst的精确结果在一级近似下完全一致,在二级近似下略有不同,但将难以求解的问题转化成简单的代数方程、用这一方法对新近获得的SnCl_4·5H_2O在水溶液中的~(119)Sn二维交换谱进行了处理,得到与实验相吻合的结果,并求得了SnCI_6~(2-)水解体系的动态交换速率常数。     

反应速率控制步骤定义的更新

一、引言反应速率控制步骤的概念在连串反应中得到广泛的应用,它是一个化学动力学中的重要基本概念。然而,对什么是反应速率控制步骤,近年来在教科书和杂志上曾出现各种定义及修正;在叫法上亦存在着速率     

RESEARCH ON METHOD TO CALCULATE VELOCITIES OF SOLID PHASE AND LIQUID PHASE IN DEBRIS FLOW

Velocities of solid phase and liquid phase in debris flow are one key problem to research on impact and abrasion mechanism of banks and control structures under action of debris flow. Debris flow was simplified as two-phase liquid composed of solid phase with the same diameter particles and liquid phase with the same mechanical features. Assume debris flow was one-dimension two-phase liquid moving to one direction, then general equations of velocities of solid phase and liquid phase were founded in two-phase theory. Methods to calculate average pressures, volume forces and surface forces of debris flow control volume were established. Specially, surface forces were ascertained using Bingham's rheology equation of liquid phase and Bagnold's testing results about interaction between particles of solid phase. Proportional coefficient of velocities between liquid phase and solid phase was put forward, meanwhile, divergent coefficient between theoretical velocity and real velocity of solid phase was provided too. To state succinctly before, method to calculate velocities of solid phase and liquid phase was obtained through solution to general equations. The method is suitable for both viscous debris flow and thin debris flow. Additionally, velocities every phase can be identified through analyzing deposits in-situ after occurring of debris flow. It is obvious from engineering case the result in the method is consistent to that in real-time field observation.     

温升速率对高温应变计性能的影响

本文介绍了高温应变计在温度变化下热输出特性变化的理论公式,用实验方法测定了应变计敏感栅和试件表面温度之间的温差,找出了用两种不同胶粘剂(无机胶粘剂u_(529),及有机胶粘剂 J06—2)粘贴的应变计在试件正面加热与反面加热条件下,热输出的变化规律.     

粘塑性损伤模型模拟准超塑性单轴拉伸行为

发展了Chaboche粘塑性本构模型的大变形隐式算法，用损伤(DM)和无损伤(NDM)模型模拟准超塑性单轴拉伸。发现变形过程可分为三个阶段：均匀变形、颈缩发展、断裂破坏阶段。DM可准确模拟前两个阶段变形，NDM只能较好地模拟均匀变形阶段，表明DM可以较精确地描述稳定发展的动态过程。由于有限元方法只能描述连续介质，因此对于断裂破坏阶段，NDM模拟载荷大于试验结果，DM的载荷小于试验结果，这是由高应变速率敏感性造成。DM能够描述试验中出现地多处颈缩现象，局部应变速率分布随时间演化反映了颈缩发展程度。严重颈缩部位的距离代表着超塑性变形能力，距离越大，抗颈缩能力越好。     

Evaluation of Thermal Hazard of Composite Modified Double-base Propellant by Microcalorimetery Method

<正>The thermal decomposition behavior of composite modified double-base(CMDB) propellant containing cyclotrimethylene trinitramine(RDX) was studied via a Calvet microcalorimeter at five different heating rates.The activation energy(E) and the pre-exponential factor(A) of two obvious exothermic processes were obtained by Kissinger's method and Ozawa's method.The entropy of activation(△A~≠),the enthalpy of activation(△H~≠),and the free energy of activation(△G~≠) of the first stage were calculated.To evaluate the thermal hazard of the RDX-CMDB propellant, the critical temperature of thermal explosion(T_b),the self acceleration decomposition temperature(T_(SADT)),the adiabatic decomposition temperature increment(△T_(ad)) and the time-to-explosion of adiabatic system(t) were presented as 145.3℃,138.15℃,1634 K and 583.71 s(n=0) and 586.28 s(n=1),respectively.     

CH_3SO+HO_2气相反应机理与主通道速率常数

在MPW1PW91/6-311G(d,p)水平上优化了标题反应各驻点物种的几何构型,并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态结构及连接性进行了验证.采用QCISD(T)/6-311G(d,p)方法对所有驻点及反应路径的部分选择点进行单点能校正,分别构建了CH3SO+HO2反应体系的单、三重态反应势能剖面.研究结果表明,CH3SO+HO2反应体系存在6条反应通道7条路径,优势通道(1)R→3IM→P1(CH3SOH+3O2)发生在三重态势能面上,此通道包含两条路径,其表观活化能分别为12.01和-30.04kJ?mol-1,主路径(2)R→3IM→3TS2→P1(CH3SOH+3O2)是一个无势垒氢迁移过程.利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了主路径(2)在200～2500K温度范围内的速率常数kTST,kCVT和kCVT/SCT,在此温度区间内的表观反应速率常数三参数表达式为kCVT/SCT=4.08×10-24T3.13exp(8012.2/T)cm3imolecule-1is-1,具有负温度系数效应.速率常数计算结果显示,变分效应在计算温度段内影响较小,而量子力学隧道效应在低温段有显著影响.     

PEEK复合材料的降解动力学

石墨、碳纤维和聚四氟乙烯(PTFE)填充的聚醚醚酮(PEEK)具有自润滑作用,是高性能的复合材料。采用热失重分析仪研究了聚醚醚酮及其复合材料的热降解行为,用Kissinger方法和Ozawa方法计算了复合材料的反应活化能(Ea)。与PEEK相比较,自润滑PEEK复合材料具有更高的降解反应活化能和更低的反应速率常数(K)。     

激发态H2(X1∑+g,v=1,J=1)之间的碰撞能量合并

受激拉曼激发H2(0,1)基态的Q支得到H2(1,1)能级.在室温条件下,利用反斯托克斯拉曼散射(CARS)探测技术测量了碰撞能量合并(EP)过程H2(1,1)+H2(1,1)→H2(2,J)+H2(0,J″)及H2(1,1)与H2(1,J)转动能级间的碰撞转移速率系数.扫描CARS谱表明在H2(1,1)能级的碰撞能量...     

医用生物材料的低温保存研究

生物材料的低温保存一般都要经历降温过程、低温储存过程及复温过程,其中降温过程中对生物细胞的影响最大.每一种生物细胞都有自己合适的降温速率,如能满足其这种降温速率,细胞所受到的低温损伤最小,则生物细胞的复活率最高.文中介绍程序控制变速降温装置的主要结构及几种典型生物体的降温过程.最后,对器官的低温保存进行分析讨论.