共查询到11条相似文献,搜索用时 73 毫秒
1.
采用Chiew的硬球链方程描述分子间的排斥作用,改进了SAFT状态化学方程。对烷烃、芳香烃、酮、卤代烃和聚合物体系PVT性质的计算结果表明,改进后的SAFT状态方程进一步提高计算精度,初值的敏感性降低,模型参数呈良好的规律性,为提高模型对聚合物溶液相平衡预测能力奠定了良好的基础。 相似文献
2.
含临界区流体混合物汽液平衡等热力学性质的研究是化工热力学的一个难题。本文用改进的统计缔合流体理论方程(SAFT-CP)^[1,2]结合范德华单流体混合规则(vdWl)计算了含临界点的二元混合物的汽液平衡。与原始的SAFT方程^[3/4]相比,SAFT-CP方程以非球形的硬体项作为参考流体,代替原来的硬球项,考虑了分子成链对色散作用的影响,对于极性流体,考虑了分子的偶极-偶极相互作用而忽略了缔合作用。本文计算的二元体系包括非极性-非极性体系:二氧化碳-丙烷、二氧化碳-丁烷和二氧化碳-戊烷,以及非极性~极性体系:硫化氢-戊烷、甲烷-丙酮和二氧化碳-甲醇。含临界点在内的计算结果与文献实验值符合很好,表明该方程适用于二元混合物含临界区的相平衡计算,具有广阔的应用前景。 相似文献
3.
有机物临界参数的关联式估算研究 总被引:3,自引:0,他引:3
为改善有机物临界参数估算方法的精度,提出了以化合物的正常沸点Tb、常温比重d、分子量M和分子中原子数N估算临界参数的一组关联式:其中:Tc=a0 a1Tb^k1 a2Tb^k1d^k2/M^k3 a3Tb^K1d^k4/m^k5 Pc=a0 a1x1 a2X2 a3x1^2 a4x2^2 Vc=a0 a1x1 a2x2 a3xa^2 a4x2^2其中:x1=Tb^k1M^k2N^k3d^k4,X1=Tb^k5M^k6N^k7d^k8,用正交优化法对上述关联式进行参数估值,得出各类有机化合物的关联式参数,用312个有实测l临界数值的化合物进行验算,结果表明:本文关联式估算Tc、Pc、Vc的平均误差均比前人估算方法的平均误差大大降低,且计算方便,适用范围广。 相似文献
4.
本文基于P-V-T与T-u-P联系的相似性,结合Peng—Robinson立方型状态方程(PREOS),建立了一个预测纯烷烃气液相粘度的统一模型。新模型首先运用PREOS方程来计算指定温度下物质的饱和蒸汽压,然后以温度和饱和蒸汽压为独立变量,计算饱和气液相粘度。采用大量实测数据对新模型进行考核的结果表明,新模型在亚临界和超临界范围内,都有较好的计算结果。 相似文献
5.
定义了一个petri网子类:PN=(S,T;F,M0),满足条件s∈S→|·s|≤1。证明:当目标标识Md>0时,此petri网子类的可达性等价于状态方程Md=M0+ATX的可满足性。同时,当此petri网子类的可达性等价于状态方程可满足性时,可得出如下两点结论:(1)对于满足M0+ATX>0的每个非平凡的非负整数向量X,都■t∈Tx:M0[t>;(2)对于满足M0+ATX>0的每个非平凡的非负整数向量X,X都是PN的一个可执行向量。 相似文献
6.
本文定义了一个petri网子类: ,满足条件 。本文证明:当目标标识 时,此petri网子类的可达性等价于状态方程 的可满足性。同时,当此petri网子类的可达性等价于状态方程可满足性时,可得出如下两点结论:①对于满足 的每个非平凡的非负整数向量 ,都 ;②对于满足 的每个非平凡的非负整数向量 , 都是 的一个可执行向量。 相似文献
7.
In this paper, we study statistical properties of fluid flows that are actively controlled. Statistical properties such as Lagrangian and Eulerian time-averages are important flow quantities in fluid flows, particularly during mixing processes. Due to the assumption of incompressibility, the transformations in the state space can be described by a sequence of measure preserving transformations on a measure space. The classical Birkhoff's pointwise ergodic theorem does not necessarily apply in the context of sequences of transformations. We call B-regular a sequence for which this theorem holds. Motivated by mixing control concepts, we define three notions of asymptotic equivalence for sequences of transformations. We show an example in which Birkhoff's pointwise ergodic theorem does not hold even when a ‘strong’ asymptotic equivalence to a B-regular sequence is assumed. Under a ‘very strong’ asymptotic equivalence condition, we prove B-regularity. In the context of optimize-then-stabilize strategy for mixing control, we also prove that very strong asymptotic equivalence to a mixing sequence implies mixing. The mean ergodic theorem and the Poincare’ recurrence theorem are also proven for sequences of transformations under suitable asymptotic equivalence assumptions. 相似文献
8.
Pedro Almenar 《Computers & Mathematics with Applications》2012,63(1):310-317
This paper presents an upper bound for the distance between a zero and a critical point of a solution of the second order linear differential equation (p(x)y′)′+q(x)y(x)=0, with p(x),q(x)>0. It also compares it with previous results. 相似文献
9.
梯度矢量流Snake模型临界点剖析 总被引:7,自引:0,他引:7
作为经典Snake模型的一个变体,梯度矢量流(gradient vector flow,简称GVF)Snake在扩大Snake轮廓的捕捉范围和深度凹陷区域的收敛上具有卓越的性能.但GVF Snake在初始化时存在一个临界点问题:在目标内部的临界点必须在初始Snake轮廓的内部;在目标外部的临界点必须在Snake轮廓的外部.否则,Snake轮廓将不能收敛到正确的结果.对GVF Snake的临界点问题进行探讨,详细分析了临界点的影响因素,指出GVF场只有在合适的条件下才是有效的;证明了相关文献中从粘性流体力学 相似文献
10.
On the convergence of an extended state observer for nonlinear systems with uncertainty 总被引:1,自引:0,他引:1
The extended state observer first proposed by Jingqing Han in [J.Q. Han, A class of extended state observers for uncertain systems, Control Decis. 10 (1) (1995) 85-88 (in Chinese)] is the key link toward the active disturbance rejection control that is taking off as a technology after numerous successful applications in engineering. Unfortunately, there is no rigorous proof of convergence to date. In this paper, we attempt to tackle this long unsolved extraordinary problem. The main idea is to transform the error equation of objective system with its extended state observer into a asymptotical stable system with a small disturbance, for which the effect of total disturbance error is eliminated by the high-gain. 相似文献
11.
Huxiao Luo 《Computers & Mathematics with Applications》2019,77(3):877-887
In this paper, we study the fractional Choquard equation where , , , and satisfies the general Berestycki–Lions conditions. Combining constrained variational method with deformation lemma, we obtain a ground state solution of Pohoz?aev type for the above equation. The result improves some ones in Shen et al. (2016). 相似文献