共查询到20条相似文献，搜索用时 328 毫秒
1.
基于分子拓扑学理论,给出了一组可根据链烷烃名称极易获取的分子拓扑指数(N,Pi,Sj),并对链烷烃的色谱保留指数、标准生成焓、标准熵、标准生成自由能以及在200C时链烷烃的摩尔体积、蒸发热、摩尔折光率七种理化性质进行定量结构-相关性研究,得多元线性回归方程.研究结果表明,本文给出的拓扑指数简单易得,应用面广,与链烷烃具有优良的性质相关性和较高的结构选择性. 相似文献
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一个图(分子图)G的Randi(c)指标定义为图G的所有边uv上的权(d(u)d(v))·1/2之和,其中(d(u)和d(v))分别表示顶点u和v的度.Randi(c)指标是化学图论中常见且重要的一个拓扑指标.本文给出了转向细胞数为2的链状四角系统的Randi(c)指标. 相似文献
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Padmakar-Ivan（PI）指数是一个类似于Wiener指数的拓扑指数,它能够反应有机分子的某些结构特征。给出给定顶点数和叶子节点数的Halin图的PI指数,并刻画具有相应PI指数的Halin图类。 相似文献
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雷勇 《吕梁高等专科学校学报》2014,(2):11-13
图G的顶点(边)Pardmakar-Ivan指数是到G的所有边e=uv的两个端点u和v距离不相等的总的顶点数(边数)的和。在此给出了割点数大于1的简单连通图G的顶点和边PI指数的计算公式。 相似文献
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图的L(s,t)-标号的概念来自频道分配问题.设s和t是2个非负整数.图G的一个L(s,t)-标号是一个从G的顶点集到整数集的映射,满足:①任意2个相邻顶点对应的整数相差至少为s;②任意2个距离为2的顶点对应的整数相差至少为t.给定图G的一个L(s,t)-标号f,的L(s,t)边跨度定义为max{|f(u)-f(v)|:(u,v)∈E(G)},记为βst(G,f).图G的L(s,t)边跨度定义为min{βst(G,f):f取遍图G的所有L(s,t)-标号},记为βst(G).设T是一棵最大度为△(≥2)的树.证明了:若2s≥t≥0,则βst(T)=([△/2]-1)t s;若0≤2s＜t且△为偶数,则βst(T)=[(△-1)t/2];若0≤2s＜t且△为奇数,则βst(T)=(△-1)t/2 s.同时完全确定了2条路的笛卡儿乘积图和正四边形格图的L(s,t)边跨度. 相似文献
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设G=(V,E)为简单连通图,称PIv(G)=∑e=uv∈E(nu(e|G)+nv(e|G))为G的顶点PI指数,其中nu(e|G)表示图G中到边e=uv的端点u的距离小于到端点v的距离的顶点数,nv(e|G)表示图G中到边e=uv的端点v的距离小于到端点u的距离的顶点数.用分类讨论法得到了圈和路的平方图的顶点PI指数. 相似文献
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孙立建 《数学学习与研究(教研版)》2008,(3)
设Kv是v点完全图,其任二不同顶点x和y之间都恰有一条边(x,y)相连.对于有限简单图G,所谓的G填充设计,记作G-OPD(v)是一个序偶(X,B),其中X是Kv的顶点集,B为Kv中同构于G的子图的集合,称为区组集,使得Kv中每条边至多出现在B的1个区组中.本文解决了v=22时,一个六点九边图G的填充设计. 相似文献
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对于给定图G顶点集上一个非负整数函数f,满足:若dG(u,v)＝1,f(u)-f(v)≥d;若 dG(u,v)＝2,f(u)-f(v)≥1.称f 为L(2,1)-标号.这是由频道分配问题抽象出来的数学模型.本文主要研究该标号问题的一个参数,即边跨度,记作βd(G)＝minf max{f(u)-f(v):u∈V(G)},即对于所有正常的L(d,1)-标号,使得相邻顶点标号之差的最大值达到最小.本文主要讨论了圈Cn、树T、 k-部完全图、正三角形网格、 正四边形网格以及弦图等图类的边跨度,并给出了确切的数值. 相似文献
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图G的L(j,k) 标号是图的顶点集到非负整数集的一个映射, 使得相邻顶点所对应的整数相差至少为j,距离为2的顶点所对应的整数相差至少为k. 对于图G的一个L(j,k) 标号f, 定义其L(j,k) 边跨度为βj,k(G,f)=max{f(x)-f(y):{ x,y}∈E(G)}. 图G的L(j,k) 边跨度定义为βj,k(G),它是G的所有L(j,k) 标号f的L(j,k) 边跨度中最小的. 图G的实值L(j,k) 标号是整数L(j,k)标号的推广, 是满足相应的距离一条件和距离二条件的从顶点集到实数集的一个映射. 图G的实值L(j,k)标号的边跨度记为j,k(G). 研究了图的实值L(j,k)边跨度和整数L(j,k)边跨度的若干性质, 完全确定了所有圈以及完全t-部图的边跨度. 相似文献
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一种新拓扑指数X用于烯烃的QSAR研究 总被引：2，自引：0，他引：2
根据分子图的邻接矩阵和和距离矩阵,分别获得各烯烃分子的顶点度矩阵和距离加和矩阵,在此基础上提出一种新的拓扑指数X。拓扑指数X与烯烃的热力学函数△Hf（g）,S（g）,△Gf（g）均有良好的相关性,其复相关系数均在0．998以上。 相似文献
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应用于DC-DC变换器的传统拓扑中SEPIC(Single-Ended Primary Inductance Converter)拓扑既可以用于升压又可以用于降压,并且输出电压为正电压,具有启动时限制浪涌电流、较小输入电流纹波和低电磁干扰(Electromagnetic Interference,EMI),具有谐波小等优点,但针对SEPIC拓扑的详细分析和建模相对较少,文中针对工作于电流临界模式(Critical Current Mode,CRM)的SEPIC线路进行了详细的分析,并对理论等式进行了详细推导,给出了简化的设计步骤,最后根据要求对SEPIC变换器进行了设计,并给出了仿真波形. 相似文献
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Objective: To investigate the time and postoperative binocular vision of strabismus surgery for children with intermittent exotropia (X (T)). Methods: A retrospective investigation was conducted in 80 child patients with intermittent exotropia. Pre- and postoperative angles of deviation fixating at near (33cm) and distant targets (6m) were measured with the prolonged alternate cover testing. The binocular function was assessed with synoptophore. Twenty-one patients took the postoperative synoptophore exercise. Results: (1) A week after surgery, 96.2% of the 80 patients had binocular normotopia, while a year after surgery, 91.3% of the 80 patients had binocular normotopia; (2) Preoperatively, 58 patients had near stereoacuity, while postoperatively, 72 patients achieved near stereoacuity (P<0.05); (3) Preoperatively, 64 patients had Grade I for the synoptophore evaluation and postoperatively, 76 patients achieved Grade I. Meanwhile, 55 patients had Grade Ⅱpreoperatively and 72 achieved Grade Ⅱ postoperatively. For Grade Ⅲ, there were 49 patients preoperatively and 64 patients postoperatively (P<0.05); (4) Patients of 5～8 years old had a significantly better recovery rate of binocular vision than those of 9～18 years old (P<0.05); (5)Patients taking postoperative synoptophore exercise had a better binocular vision than those taking no exercise (P<0.05). Conclusions: (1) Strabismus surgery can help to preserve or restore the binocular vision for intermittent exotropia; (2) Receiving the surgery at young ages may develop better postoperative binocular vision; (3) The postoperative synoptophore exercise can help to restore the binocular vision. 相似文献
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讨论了卷积码及删截卷积码的编、译码原理，通过仿真分析了由二者构造的不等差错保护系统的性能和特点，仿真结果表明，该UEP方案在分等级传输中能获得较好的性能。 相似文献
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文中概述了分子连接性指数法的原理和特点,描述了其在预测苯胺及苯酚类化合物、氯代芳香化合物、取代苯甲酸类化合物的生物降解性中的应用.建立的QSBR模型表明,芳香族化合物的生物降解性与其分子连接指数具有良好的相关性,其降解性还受分子的空间结构和电荷密度影响. 相似文献
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以STC89c52单片机设计主控模块,以TI公司的ccll00芯片设计无线发射和接收模块,工作于915MHzISM频段,空中波特率为lOOKbps,利用HFSS仿真软件设计微带天线并进行仿真,得到S参数、驻波比、场强、三维远场辐射方向图等。同时利用smartRFstudio软件可测得天线场强,实际效果好于仿真结果,实现了915MHz无线通信,通信距离在10米以上。 相似文献
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The activation of Ca2 entry through store-operated channels by agonists that deplete Ca2 from the endoplasmic reticulum (ER)is a ubiquitous signaling mechanism,the molecular basis of which has remained elusive for the past two decades.Store-operated Ca2 -release-activated Ca2 (CRAC)channels constitute the sole pathway for Ca2 entry following antigen-receptor engagement.In a set of breakthrough studies over the past two years,stromal interaction molecule l(STIM1,tbe ER Ca2 sensor) and Orail(a pore-forming subunit of the CRAC channel)have been identified.Here we review these recent studies and the insights they provide into the mechanism of store-operated Ca2 channels(SOCCs). 相似文献
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To understand the feasibility of its application to the in situ remediation of contaminated groundwater, the dechlori-nation of 2,4-dichlorophenol (2,4-DCP) by Ni/Fe nanoparticles in the presence of humic acid (HA) was investigated. We found that, as high performance liquid chromatography (HPLC) was used, the 2,4-DCP was first quickly reduced to o-chlorophenol (o-CP) andp-chlorophenol (p-CP), and then reduced to phenol as the final product. Our experimental results indicated that HA had an adverse effect on the dechlorination of 2,4-DCP by Ni/Fe nanoparticles, as the HA concentration increased, the removal rate decreased evidently. It also demonstrated that 2,4-DCP was reduced more easily to o-CP than to p-CP, and that the sequence of the tendency in dechlorination of intermediates was p-CP>o-CP. Transmission electron microscope (TEM) showed that HA could act as an adsorbate to compete reactive sites on the surface of Ni/Fe nanoparticles to decrease the dechlorination rate. Also we con-cluded that the dechlorination reaction of 2,4-DCP over Ni/Fe nanoparticles progressed through catalytic reductive dechlorination. 相似文献
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The expectations for sensor networks are growing. The performance of wireless sensor networks （WSNs） is greatly influenced by their network topology. In this paper, we consider four patterned topologies that best support connectivity among these deployed sensor nodes in two-tiered WSNs. The theoretical and simulation results show that the triangle-based topology has smaller cell number, shorter maximum hop length, less total energy consumption, and better performance than other topologies. The analysis carried out in this paper could provide the guidelines for network deployment and protocol design in the future applications. 相似文献