Although many authors have emphasized the Cenozoic history of deformation, exhumation and cooling in the Tiaushan area related to the India-Asia collision, very little is known about the Mesozoic history of compressio...Although many authors have emphasized the Cenozoic history of deformation, exhumation and cooling in the Tiaushan area related to the India-Asia collision, very little is known about the Mesozoic history of compression and uplift within the Tianshan. In order to obtain information about the Mesozoic exhumation history and processes of cooling in eastern Tianshan, fission track methods on apatite were used. Sampling was made in the Jueluotage Range. Three samples （Z001-Z003） were taken from granite in borehole ZK6301 of Yandong pluton; the ages range from 97.0 to 87.6 Ma that are much younger than the pluton age which was dated by U-Pb zircon at 334±2 Ma. Two samples in northern piedmont of the Jueluotage Range were collected from Jurassic strata in Dikaner （DK001） and Dananhu （D001） whose ages are 91.5 and 93.4 Ma respectively. The average apparent exhumation rate is 0.039 nun/a calculated by extrapolation on the basis of Yandong samples, indicating an extremely slow exhumation in the Jueluotage Range since the Late Cretaceous. Two Jurassic samples reached the maximum depths after deposition and experienced the maximum temperatures of ca. 105 and 108℃ until the late Early Cretaceous before a period of cooling and exhumation occurred at 114 and 106 Ma.展开更多
A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a ...A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 km, 8.3 and 11 km, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time, are simulated. The model results at the satellite receiving time are compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track. The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, vidth, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L-1are simulated in order to understand the variations of influencing range.展开更多
The curvature factor of the parallel-track bistatic SAR is range dependent, even without variation of the effective velocity. Accounting for this new characteristic, a parallel-track chirp scaling algorithm （CSA） is...The curvature factor of the parallel-track bistatic SAR is range dependent, even without variation of the effective velocity. Accounting for this new characteristic, a parallel-track chirp scaling algorithm （CSA） is derived, by introducing the method of removal of range walk （RRW） in the time domain. Using the RRW before the CSA, this method can reduce the varying range of the curvature factor, without increasing the computation load obviously. The azimuth dependence of the azimuth-FM rate, resulting from the RRW, is compensated by the nonlinear chirp scaling factor. Therefore, the algorithm is extended into stripmap imaging. The realization of the method is presented and is verified by the simulation results.展开更多
Background Changing the distance between a sample and an exposed solid-state nuclear track detector affects the number of alpha tracks recorded by the detector.This concept had been used to distinguish high-energy alp...Background Changing the distance between a sample and an exposed solid-state nuclear track detector affects the number of alpha tracks recorded by the detector.This concept had been used to distinguish high-energy alpha particles by computing the alpha emission rate at two distances(0 and 2 cm)from animal bone ash.Materials and methods Two Cr-39 detectors were placed in a container with bone ash inside to measure the alpha emission rate when the detectors were in contact with the ash and hung at a distance of 2 cm from the ash.Results The alpha emission rate was found to be 62.7×10^(−4) Bq cm^(−2) when the detector was in contact with the sample(a small exposure area)and 324.4×10^(−4) Bq cm^(−2) when the sample was placed 2 cm away(a larger exposure area).A mathematical equalization of the exposure areas was conducted(the area of the detector exposed to the alpha emitter sample at a distance of 2 cm was equalized to the area exposed when in contact with the sample).After equalization,a reduction in the average value of the alpha emission rate from 324.4×10^(−4) to 17.4×10^(−4) Bq cm^(−2) was observed.Conclusion The increase in distance between the sample and the detector allowed only high-energy alpha particles with a range greater than the traveled distance to reach the detector.Thus,this system can distinguish the type and number of nuclides in the sample by changing the distance between the detector and the sample according to each nucleus range.Additionally,the results show that the alpha emission rates in these bone samples are higher than the local values.展开更多
The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of ...The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.展开更多
文摘Although many authors have emphasized the Cenozoic history of deformation, exhumation and cooling in the Tiaushan area related to the India-Asia collision, very little is known about the Mesozoic history of compression and uplift within the Tianshan. In order to obtain information about the Mesozoic exhumation history and processes of cooling in eastern Tianshan, fission track methods on apatite were used. Sampling was made in the Jueluotage Range. Three samples （Z001-Z003） were taken from granite in borehole ZK6301 of Yandong pluton; the ages range from 97.0 to 87.6 Ma that are much younger than the pluton age which was dated by U-Pb zircon at 334±2 Ma. Two samples in northern piedmont of the Jueluotage Range were collected from Jurassic strata in Dikaner （DK001） and Dananhu （D001） whose ages are 91.5 and 93.4 Ma respectively. The average apparent exhumation rate is 0.039 nun/a calculated by extrapolation on the basis of Yandong samples, indicating an extremely slow exhumation in the Jueluotage Range since the Late Cretaceous. Two Jurassic samples reached the maximum depths after deposition and experienced the maximum temperatures of ca. 105 and 108℃ until the late Early Cretaceous before a period of cooling and exhumation occurred at 114 and 106 Ma.
文摘A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 km, 8.3 and 11 km, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time, are simulated. The model results at the satellite receiving time are compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track. The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, vidth, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L-1are simulated in order to understand the variations of influencing range.
基金supported by the National Natural Science Foundation of China (60572151)the Ministry of EducationKey Project (103154).
文摘The curvature factor of the parallel-track bistatic SAR is range dependent, even without variation of the effective velocity. Accounting for this new characteristic, a parallel-track chirp scaling algorithm （CSA） is derived, by introducing the method of removal of range walk （RRW） in the time domain. Using the RRW before the CSA, this method can reduce the varying range of the curvature factor, without increasing the computation load obviously. The azimuth dependence of the azimuth-FM rate, resulting from the RRW, is compensated by the nonlinear chirp scaling factor. Therefore, the algorithm is extended into stripmap imaging. The realization of the method is presented and is verified by the simulation results.
文摘Background Changing the distance between a sample and an exposed solid-state nuclear track detector affects the number of alpha tracks recorded by the detector.This concept had been used to distinguish high-energy alpha particles by computing the alpha emission rate at two distances(0 and 2 cm)from animal bone ash.Materials and methods Two Cr-39 detectors were placed in a container with bone ash inside to measure the alpha emission rate when the detectors were in contact with the ash and hung at a distance of 2 cm from the ash.Results The alpha emission rate was found to be 62.7×10^(−4) Bq cm^(−2) when the detector was in contact with the sample(a small exposure area)and 324.4×10^(−4) Bq cm^(−2) when the sample was placed 2 cm away(a larger exposure area).A mathematical equalization of the exposure areas was conducted(the area of the detector exposed to the alpha emitter sample at a distance of 2 cm was equalized to the area exposed when in contact with the sample).After equalization,a reduction in the average value of the alpha emission rate from 324.4×10^(−4) to 17.4×10^(−4) Bq cm^(−2) was observed.Conclusion The increase in distance between the sample and the detector allowed only high-energy alpha particles with a range greater than the traveled distance to reach the detector.Thus,this system can distinguish the type and number of nuclides in the sample by changing the distance between the detector and the sample according to each nucleus range.Additionally,the results show that the alpha emission rates in these bone samples are higher than the local values.
基金supported by the National Natural Science Foundation of China(Nos.61179018,61102165,61002006,61102167)Aeronautical Science Foundation of China(No.20115584006)Special Foundation Program for Mountain Tai Scholars
文摘The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.
