As an important ecological tree species in northern China, Populus simonii plays a crucial role in maintaining ecological balance and promoting environmental sustainability. The academic community has conducted a seri...As an important ecological tree species in northern China, Populus simonii plays a crucial role in maintaining ecological balance and promoting environmental sustainability. The academic community has conducted a series of in-depth studies on this species, covering key areas such as genomics, survival mechanisms, and genetic breeding. Through the analysis of the genomic structure and function of P. simonii, we have not only revealed the molecular basis for its adaptation to harsh environments but also identified key genes that promote its growth and resistance to pests and diseases. Furthermore, exploring the survival mechanisms of P. simonii has deepened our understanding of its stress resistance traits, including how it effectively copes with abiotic stresses such as drought, salinization, and heavy metal pollution. In genetic breeding, significant progress has been made through the application of modern biotechnology, improving the growth rate and wood quality of P. simonii and enhancing its environmental adaptability and disease resistance. These research findings have not only enriched our knowledge of the biological characteristics of P. simonii but also provided a solid scientific foundation for its application in ecological restoration, forestry production, and environmental management.展开更多
This paper studies the estimation performance of the coherent processing parameter (CPP), including time delay differences and phase synchronization errors among different apertures of the distributed coherent apert...This paper studies the estimation performance of the coherent processing parameter (CPP), including time delay differences and phase synchronization errors among different apertures of the distributed coherent aperture radar (DCAR). Firstly, three architectures of signal processing in the DCAR are introduced. Secondly, the closed-form Cramer-Rao bound (CRB) of the CPP estimation is derived and compared. Then, the closed-form CRB is verified by numerical simulations. Finally, when the next generation radar works in a fully coherent mode, the closed-form signal-to-noise ratio (SNR) gain of the three architectures is presented.展开更多
The optimal estimation performance of target parameters is studied. First, the general form of Cramer-Rao bound (CRB) for joint estimation of target location and velocity is derived for coherent multiple input multi...The optimal estimation performance of target parameters is studied. First, the general form of Cramer-Rao bound (CRB) for joint estimation of target location and velocity is derived for coherent multiple input multiple output (MIMO) radars. To gain some insight into the behavior of the CRB, the CRB with a set of given orthogonal waveforms is studied as a specific case. Second, a maximum likelihood (ML) estimation algorithm is proposed. The mean square error (MSE) of the ML estimation of target location and velocity is obtained by Monte Carlo simulation and it approaches CRB in the high signal-to-noise ratio (SNR) region.展开更多
Objective:To investigate the grossαandβradioactivity levels of drinking water source in the city,the largest oil field production base in northeast China,in order to ensure the safety of drinking water and public he...Objective:To investigate the grossαandβradioactivity levels of drinking water source in the city,the largest oil field production base in northeast China,in order to ensure the safety of drinking water and public health.Methods:The water samples from three drinking water sources were collected and tested in the dry and wet season,respectively.The grossαradioactivity was measured by standard curve method,grossβwas measured by thin sample method.Results:Totally 184 samples were collected from the three sampling areas in dry and wet season respectively.The average values of grossαandβradioactivity levels in the drinking water source area were(0.24±0.09)and(0.30±0.17)Bq/L respectively.The average activity concentration of grossαand grossβin the dry season was(0.23±0.09)and(0.29±0.18)Bq/L,respectively.The grossαandβradioactivity levels gradually decreased from the intake to the end of the reservoir of drinking water source areas.Conclusions:The grossαandβradioactivity levels and distribution of drinking water source areas in this city were all lower than the drinking water limit issued by China and the reference level recommended by the World Health Organization.The radioactivity of water body of the drinking water source was within the normal background level.展开更多
文摘As an important ecological tree species in northern China, Populus simonii plays a crucial role in maintaining ecological balance and promoting environmental sustainability. The academic community has conducted a series of in-depth studies on this species, covering key areas such as genomics, survival mechanisms, and genetic breeding. Through the analysis of the genomic structure and function of P. simonii, we have not only revealed the molecular basis for its adaptation to harsh environments but also identified key genes that promote its growth and resistance to pests and diseases. Furthermore, exploring the survival mechanisms of P. simonii has deepened our understanding of its stress resistance traits, including how it effectively copes with abiotic stresses such as drought, salinization, and heavy metal pollution. In genetic breeding, significant progress has been made through the application of modern biotechnology, improving the growth rate and wood quality of P. simonii and enhancing its environmental adaptability and disease resistance. These research findings have not only enriched our knowledge of the biological characteristics of P. simonii but also provided a solid scientific foundation for its application in ecological restoration, forestry production, and environmental management.
基金supported by the National Natural Science Foundation of China(61171120)the Key National Ministry Foundation of China(9140A07020212JW0101)+2 种基金the Foundation of Tsinghua University(20101081772)the Foundation of National Laboratory of Information Control Technology for Communication System of Chinathe Foundation of National Information Control Laboratory
文摘This paper studies the estimation performance of the coherent processing parameter (CPP), including time delay differences and phase synchronization errors among different apertures of the distributed coherent aperture radar (DCAR). Firstly, three architectures of signal processing in the DCAR are introduced. Secondly, the closed-form Cramer-Rao bound (CRB) of the CPP estimation is derived and compared. Then, the closed-form CRB is verified by numerical simulations. Finally, when the next generation radar works in a fully coherent mode, the closed-form signal-to-noise ratio (SNR) gain of the three architectures is presented.
基金supported by the National Natural Science Foundation of China(61171120)the Key National Ministry Foundation of China(9140A07020212JW0101)the Foundation of Tsinghua University(20101081772)
文摘The optimal estimation performance of target parameters is studied. First, the general form of Cramer-Rao bound (CRB) for joint estimation of target location and velocity is derived for coherent multiple input multiple output (MIMO) radars. To gain some insight into the behavior of the CRB, the CRB with a set of given orthogonal waveforms is studied as a specific case. Second, a maximum likelihood (ML) estimation algorithm is proposed. The mean square error (MSE) of the ML estimation of target location and velocity is obtained by Monte Carlo simulation and it approaches CRB in the high signal-to-noise ratio (SNR) region.
基金Special Project of Basic Application Technology Research in Heilongjiang Province(China,Primary Funders:The Finance Department of Heilongjiang Province and Heilongjiang Academy of Sciences,No.ZNBZ2019WL02 and ZNBZ2020WL02).
文摘Objective:To investigate the grossαandβradioactivity levels of drinking water source in the city,the largest oil field production base in northeast China,in order to ensure the safety of drinking water and public health.Methods:The water samples from three drinking water sources were collected and tested in the dry and wet season,respectively.The grossαradioactivity was measured by standard curve method,grossβwas measured by thin sample method.Results:Totally 184 samples were collected from the three sampling areas in dry and wet season respectively.The average values of grossαandβradioactivity levels in the drinking water source area were(0.24±0.09)and(0.30±0.17)Bq/L respectively.The average activity concentration of grossαand grossβin the dry season was(0.23±0.09)and(0.29±0.18)Bq/L,respectively.The grossαandβradioactivity levels gradually decreased from the intake to the end of the reservoir of drinking water source areas.Conclusions:The grossαandβradioactivity levels and distribution of drinking water source areas in this city were all lower than the drinking water limit issued by China and the reference level recommended by the World Health Organization.The radioactivity of water body of the drinking water source was within the normal background level.