Forecasting nonlinear chaotic time series with function expression method based on an improved genetic-simulated annealing algorithm.

The paper proposes a novel function expression method to forecast chaotic time series, using an improved genetic-simulated annealing (IGSA) algorithm to establish the optimum function expression that describes the behavior of time series. In order to deal with the weakness associated with the genetic algorithm, the proposed algorithm incorporates the simulated annealing operation which has the strong local search ability into the genetic algorithm to enhance the performance of optimization; besides, the fitness function and genetic operators are also improved. Finally, the method is applied to the chaotic time series of Quadratic and Rossler maps for validation. The effect of noise in the chaotic time series is also studied numerically. The numerical results verify that the method can forecast chaotic time series with high precision and effectiveness, and the forecasting precision with certain noise is also satisfactory. It can be concluded that the IGSA algorithm is energy-efficient and superior.

[Prenatal ultrasonic manifestation and clinical significance of fetal hemivertebra].

OBJECTIVE: To explore the manifestation and clinical significance of prenatal ultrasound diagnosis of fetal hemivertebra. METHODS: In the study, 27 fetals with hemivertebras (proven by post-natal X-ray, CT or MR) were examined by prenatal ultrasound and MR in Women & Children's Hospital, Ningbo, Zhejiang. Two-dimensional and three-dimensional prenatal ultrasonic manifestations were retrospective analyzed and compared with the prenatal MR diagnoses, the post-natal X-ray, CT, MR examinations. All the fetuses were carried out karyotype examinations. The full-term births recieved surgical treatment and the Cobb angle correction rate was calculated. RESULTS: The 27 cases of fetal ultrasound showed the morphological changes of the spine, with the involved segment only half of the vertebra, in which 9 cases were single hemivertebra and 18 cases multiple, 8 cases were no malformation and 19 cases other malformations, and 19 cases were induction of labor, and 8 cases of term delivery. Compared with postpartum X-ray and other imaging tests, the prenatal ultrasound accuracy rate was 92.5%, and prenatal MR 96.3%. In the 27 cases, the chromosome cultures of 25 cases were successful, in which the normal karyotype was 68.0% (17/25), and abnormal karyotype 32.0% (8/25) with multiple hemivertebra accounting for 47.1% (8/17). In 8 cases with posterior approach of hemivertebra resection, 6 patients were less than and equal to 3 years old, whose average Cobb angle correction rate was 38.02%, and 2 more than 3 years old, whose average Cobb angle correction rate was 24.98%. CONCLUSION: Fetal hemivertebra have typical sonographic manifestations. In diagnosis of fetal hemivertebra, the accuracy of prenatal ultrasound is close to that of MR, which has important clinical implications in diagnosis and overall assessment of fetal hemivertebra, and can also provide appropriate clinical genetic reference.