量热法确定对氯苯甲酸的相变热和纯度

该文使用自动绝热量热计测定了对氯苯甲酸在 480～ 580K温区的热容 ,并由热容与温度关系确定了对氯苯甲酸的熔点为 51 2 .2 79K ,摩尔熔化焓和摩尔熔化熵分别为 1 3 .50kJmol- 1和 2 6 .35JK- 1 mol- 1 ;同时用绝热量热法确定对氯苯甲酸样品的摩尔百分比为 99.35 %。     

Substrate oxidation during incremental arm and leg exercise in men and women matched for ventilatory threshold

Abstract

The aim of this study was to determine the variations in substrate utilization between men and women matched for ventilatory threshold (T _vent) during incremental arm cranking and leg cycling exercise at 70, 85, 100 and 115% of the mode-specific T _vent. Recreationally active men (n = 12) and women (n = 10) with similar values for percentage of peak oxygen consumption at T _vent participated in the study. Ventilatory equivalence, excess CO₂ and modified V-slope methods were used concurrently to determine T _vent. The participants performed 5 min of exercise at each of 70, 85, 100 and 115% T _vent during both arm cranking and leg cycling exercise. The females were tested during the early follicular phase for all trials. A two-way mixed-design analysis of variance was performed to test for differences between the sexes. When carbohydrate and fat oxidation were expressed relative to total fat-free mass, carbohydrate oxidation during arm cranking and leg cycling was significantly higher in men than women at each percentage of T _vent. In contrast, women showed significantly higher fat oxidation across intensities during both arm cranking and leg cycling. Our results suggest that when substrate utilization is expressed relative to total fat-free mass, women appear to maintain a higher rate of fat and lower rate of carbohydrate oxidation than men during both incremental arm cranking and leg cycling exercise relative to T _vent.     

溴化镝丙氨酸配合物热分解反应的热分析研究

在非等温条件下,采用DSC法研究了DyBr3·3Ala·2.5H2O配合物的热分解动力学,计算了热分解过程的活化能;分析了升温速率为10 k/min的DSC曲线,获得了热分解过程相应的动力学参数(E、lnA)及可能的热分解机理及机理函数.     

大气压与高度关系的再讨论

用绝热过程得到大气压强与高度的关系为:P=P0((T0-kμgz)/(T0))(1)/(kR),因而说明等温气压公式:P=P0e-μgz/RT、具有局限性.     

Numerical Modeling of the Performance of R22 and R290 in Adiabatic Capillary Tubes Considering Metastable Two-Phase Region——Flow Characteristics and Parametric Analysis of R22 and R290

Characteristics of R22 and its new alternative refrigerant R200 flowing through adiabatic capillary tubes are investigated based on the homogeneous model. Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity. Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further. a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40℃ to 50℃ C. the mass flow rate for R22 is increased by 16%. while the increasing rate for R290 is 13%.     

组氨酸与锌(Ⅱ)配合物标准生成焓的溶解量热法测定

合成了组氨酸锌(Ⅱ)配合物Zn(His)SO_4·H_2O(s),用溶解量热法测定了反应物和产物在298.2k条件下分别溶解在2mol/LH_2SO_4溶液中的溶解焓,根据Hess定律和所设计的热化学循环计算出配合反应焓变△_rH_m~θ=9.371±0.073kJ.mol~(-1),进而求出配合物Zn(His)SO_4·H_2O(s)的标准生成焓△_fH_m~θ=[Zn(His)SO_4·H_2O(s)]=-1788.72±1.560kJ.mol~(-1)。     

毛细管绝热节流过程焓变化特性的理论分析与实验验证

计算分析了焓相等和滞止焓相等情况下毛细管中R22节流特性参数及其变化规律．并将两种情况下所选取的毛细管与真实制冷系统毛细管比较。理论计算和实验结果都表明滞止焓相等才是毛细管绝热节流的基本特性,而绝热节流焓相等的理论不够准确。     

物理化学教学中绝热过程的探讨

在讲解物理化学概念的同时辅之一定量的习题练习，再列举一些恰当的理论联系实际的例子，将会有助于学生对概念的理解，能提高学生的学习兴趣，活跃课堂气氛．     

绝热技术制备纠缠态的研究

利用绝热技术提出制备W态和两原子高维纠缠态方案．在这些方案中,量子信息都存储在原子的基态上,且系统仅在暗态空间中演化,原子在激发态上无布居,这使得原子的自发辐射效应大大受到抑制．另外,绝热技术确保这些方案对实验参数的涨落具有强的鲁棒性．其方法操作步骤简单,既有效节省了资源,同时更容易在实验上实现．