When linear regressive models such as AR or ARMA model are used for fitting and predicting climatic time series,results are often not sufficiently good because nonlinear variations in the time series.In this paper, a ...When linear regressive models such as AR or ARMA model are used for fitting and predicting climatic time series,results are often not sufficiently good because nonlinear variations in the time series.In this paper, a nonlinear self-exciting threshold autoregressive(SETAR)model is applied to modeling and predicting the time series of flood/drought runs in Beijing,which were derived from the graded historical flood/drought records in the last 511 years(1470—1980).The results show that the modeling and predicting with the SETAR model are much better than that of the AR model.The latter can predict the flood/drought runs with a length only less than two years,while the formal can predict more than three-year length runs.This may be due to the fact that the SETAR model can renew the model according to the run-turning points in the process of predic- tion,though the time series is nonstationary.展开更多
In the past 50 years, dramatic advances have been Lachieved in male infertility treatment. Intracytoplasmicsperm injection （ICSI） provides an effective manipulation for bypassing some severe etiologies of male ferti...In the past 50 years, dramatic advances have been Lachieved in male infertility treatment. Intracytoplasmicsperm injection （ICSI） provides an effective manipulation for bypassing some severe etiologies of male fertility. However, some men may encounter difficulty in semen collection by masturbation on demand at the time of undergoing assisted reproductive technology （ART）. If a patient is unable to provide semen by masturbation, he has to undergo testicular sperm extraction （TESE） to collect spermatozoa for ICSI, which is expensive and invasive. Some men fail to obtain semen by masturbation because of temporary erectile dysfunction （ED）.展开更多
文摘When linear regressive models such as AR or ARMA model are used for fitting and predicting climatic time series,results are often not sufficiently good because nonlinear variations in the time series.In this paper, a nonlinear self-exciting threshold autoregressive(SETAR)model is applied to modeling and predicting the time series of flood/drought runs in Beijing,which were derived from the graded historical flood/drought records in the last 511 years(1470—1980).The results show that the modeling and predicting with the SETAR model are much better than that of the AR model.The latter can predict the flood/drought runs with a length only less than two years,while the formal can predict more than three-year length runs.This may be due to the fact that the SETAR model can renew the model according to the run-turning points in the process of predic- tion,though the time series is nonstationary.
基金This study was supported by a grant from the National Natural Science Foundation of China （No. 81200466）.
文摘In the past 50 years, dramatic advances have been Lachieved in male infertility treatment. Intracytoplasmicsperm injection （ICSI） provides an effective manipulation for bypassing some severe etiologies of male fertility. However, some men may encounter difficulty in semen collection by masturbation on demand at the time of undergoing assisted reproductive technology （ART）. If a patient is unable to provide semen by masturbation, he has to undergo testicular sperm extraction （TESE） to collect spermatozoa for ICSI, which is expensive and invasive. Some men fail to obtain semen by masturbation because of temporary erectile dysfunction （ED）.
