The association of typhoon tracks over the western Pacific with the low-frequency wind-field pattern of atmospheric intraseasonal (30-60 days) oscillation at 850 hPa is further studied by using observational data anal...The association of typhoon tracks over the western Pacific with the low-frequency wind-field pattern of atmospheric intraseasonal (30-60 days) oscillation at 850 hPa is further studied by using observational data analyses. Comparative analyses of the composite wind fields at 850 hPa, contrasting the atmospheric intraseasonal oscillation (ISO) with the original circulation, show that the typhoon tracks are closely related to the wind pattern of the ISO but are not obviously related to the original wind fields. Case studies of two typhoons in 2006 also show that the low-frequency wind-field pattern, particularly the maximum-value line (belt) of low-frequency cyclonic vorticity at 850 hPa, is closely related to the typhoon track. Therefore, the lowfrequency circulation pattern and the maximum-value line (belt) of low- frequency cyclonic vorticity at 850hPa can be used to predict typhoon tracks over the northwestern Pacific.展开更多
Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based fl...Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based flexible optical networks, Routing and Spectrum Assignment (RSA) has become a key problem. However, widely used dynamic RSA schemes, such as Fixed Routing (FR) and K-shortest Paths (KSP) routing schemes, are not able to realize route computation based on the link state information, thus leading to poor blocking performance and inefficient resource utilization. To solve this problem, Adaptive Routing (AR) schemes, e.g., the Entire Path Searching (EPS) scheme, have been proposed recently. These schemes have low blocking probability; however, since their computational complexities are factorial, they are not suitable for use in real networks. In this paper, we propose a novel Spectrum-Scan Routing (SSR) scheme in dynamic flexible optical networks. To the best of our knowledge, SSR is the first polynomial-time AR scheme that can realize adaptive shortest-route computation. Simulation results show that our proposed SSR scheme has lower blocking probability and higher resource utilization compared with FR and EPS. Moreover, the worst-case computational complexity of SSR increases linearly with the network scale of the torus topologies, making it applicable to real networks.展开更多
The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the io...The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. U0833602)the National Basic Research Program of China (Grant No. 2007CB411805)
文摘The association of typhoon tracks over the western Pacific with the low-frequency wind-field pattern of atmospheric intraseasonal (30-60 days) oscillation at 850 hPa is further studied by using observational data analyses. Comparative analyses of the composite wind fields at 850 hPa, contrasting the atmospheric intraseasonal oscillation (ISO) with the original circulation, show that the typhoon tracks are closely related to the wind pattern of the ISO but are not obviously related to the original wind fields. Case studies of two typhoons in 2006 also show that the low-frequency wind-field pattern, particularly the maximum-value line (belt) of low-frequency cyclonic vorticity at 850 hPa, is closely related to the typhoon track. Therefore, the lowfrequency circulation pattern and the maximum-value line (belt) of low- frequency cyclonic vorticity at 850hPa can be used to predict typhoon tracks over the northwestern Pacific.
基金supported in part by projects of National 863 Program under Grant No.2012AA011301National 973 Program under Grants No. 2010CB328203, No. 2010CB328205National Natural Science Foundation of China under Grant No. 61201188
文摘Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based flexible optical networks, Routing and Spectrum Assignment (RSA) has become a key problem. However, widely used dynamic RSA schemes, such as Fixed Routing (FR) and K-shortest Paths (KSP) routing schemes, are not able to realize route computation based on the link state information, thus leading to poor blocking performance and inefficient resource utilization. To solve this problem, Adaptive Routing (AR) schemes, e.g., the Entire Path Searching (EPS) scheme, have been proposed recently. These schemes have low blocking probability; however, since their computational complexities are factorial, they are not suitable for use in real networks. In this paper, we propose a novel Spectrum-Scan Routing (SSR) scheme in dynamic flexible optical networks. To the best of our knowledge, SSR is the first polynomial-time AR scheme that can realize adaptive shortest-route computation. Simulation results show that our proposed SSR scheme has lower blocking probability and higher resource utilization compared with FR and EPS. Moreover, the worst-case computational complexity of SSR increases linearly with the network scale of the torus topologies, making it applicable to real networks.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804042 and 41074115)the Post Doctor Foundation of China (Grant No. 200902445)the Fundamental Research Funds for the Central Universities (Grant No. 4081004)
文摘The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.
