摘要
应用最广泛的 QSIM算法针对的是连续函数 ,无法处理不同状态满足不同约束的问题 .PQSIM算法作了相应改进 ,增加两个新的约束 :判断约束 IF和赋值约束 EQ,限定约束作用的状态集合 ,从而可以有效地对分段函数系统进行定性仿真 .该文以其在脑电图定性产生模型中的应用实例验证算法的正确性 ,同时也展示出 PQSIM算法为脑电图研究开辟了新路 .通过时间复杂性计算证明 PQSIM算法是一个高效的定性仿真算法 .
QISM algorithm, the most popular qualitative algorithm, requires that variables in the system must be continuous, so it can't solve the problem with different constraints in different states, such as the system with piecewise functions. PQSIM algorithm makes certain improvements at this point. Two constraints are added in PQSIM, Constraint IF( f,l,g 1,g 2,g 3 ), that is defined as if f<l , then the system must satisfy g 1, if f=l , then g 2 , and if f>l , then g 3, and Constraint EQ (f,g) defined as f=g , where f is a variable, l is one of f 's landmarks, g i is a constraint set, and g is one of f 's qualitative states. The storage structure of constraints is changed to tree structure and every node in the tree has its own inherited set, S , to constrict the state sets affected by constraints. PQSIM can simulate the system with piecewise functions qualitatively and effectively. For instance, the application of PQSIM in the research of EEG Generating Model, is given to testify the correctness of this algorithm. An ideal qualitative coupled populations model of partial is set up. This qualitative model combines given biologic information and qualitative methods together. In the single population model, a cluster of neuron is considered and contains two subsets: subset 1 is composed of the main cells (i.e. pyramidal cells) which receives feedback (either excitatory or inhibitory) from subset 2, and generates excitatory potential or inhibitory potential. Subset 2 is composed of local interneurons (i.e. other nonpyramidal cells, stellate or basket cells) which receives excitatory input only and generates the output of the population. When the excitatory potential is higher than a certain value, it will jump to its max potential. This qualitative model could simulate all of the five kinds of epileptic signals spread simultaneously, i.e. one-side seizures, two-side seizures, one-side oscillatory seizures, two-side oscillatory seizures and combined seizures, which is a big problem that makes trouble in the research of quantitative EEG models. Thus it also shows that the PQSIM explore a new and promising way of EEG research. At last we analyze the complex of PQSIM, only O(ct) usually, to prove its good efficiency.
出处
《计算机学报》
EI
CSCD
北大核心
2001年第12期1287-1293,共7页
Chinese Journal of Computers
基金
国家自然科学基金 ( 6 99740 38)
国家高性能计算基金 ( 0 0 2 15 )资助
关键词
分段函数
赋值约束
PQSIM
定性仿真算法
脑电图
qualitative simulation, piecewise function, constraint IF, constraint EQ, qualitative model of EEG
