Accurate time delay estimation of target echo signals is a critical component of underwater target localization.In active sonar systems,echo signal processing is vulnerable to the effects of reverberation and noise in...Accurate time delay estimation of target echo signals is a critical component of underwater target localization.In active sonar systems,echo signal processing is vulnerable to the effects of reverberation and noise in the maritime environment.This paper proposes a novel method for estimating target time delay using multi-bright spot echoes,assuming the target’s size and depth are known.Aiming to effectively enhance the extraction of geometric features from the target echoes and mitigate the impact of reverberation and noise,the proposed approach employs the fractional order Fourier transform-frequency sliced wavelet transform to extract multi-bright spot echoes.Using the highlighting model theory and the target size information,an observation matrix is constructed to represent multi-angle incident signals and obtain the theoretical scattered echo signals from different angles.Aiming to accurately estimate the target’s time delay,waveform similarity coefficients and mean square error values between the theoretical return signals and received signals are computed across various incident angles and time delays.Simulation results show that,compared to the conventional matched filter,the proposed algorithm reduces the relative error by 65.9%-91.5%at a signal-to noise ratio of-25 dB,and by 66.7%-88.9%at a signal-to-reverberation ratio of−10 dB.This algorithm provides a new approach for the precise localization of submerged targets in shallow water environments.展开更多
Due to the complexity of blockchain technology,it usually costs too much effort to build,maintain and monitor a blockchain system that supports a targeted application.To this end,the emerging“Blockchain as a Service...Due to the complexity of blockchain technology,it usually costs too much effort to build,maintain and monitor a blockchain system that supports a targeted application.To this end,the emerging“Blockchain as a Service”(BaaS)makes the blockchain and distributed ledgers more accessible,particularly for businesses,by reducing costs and overheads.BaaS combines the high computing power of cloud computing,the pervasiveness of IoT and the decentralization of blockchain,allowing people to build their own applications while ensuring the transparency and openness of the system.This paper surveys the research outputs of both academia and industry.First,it introduces the representative architectures of BaaS systems and then summarizes the research contributions of BaaS from the technologies for service provision,roles,container and virtualization,interfaces,customization and evaluation.The typical applications of BaaS in both academic and practical domains are also introduced.At present,the research on the blockchain is abundant,but research on BaaS is still in its infancy.Six challenges of BaaS are concluded in this paper for further study directions.展开更多
The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- veri...The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- verity shown by the gauge record. A general circulation model of the Geophysical Fluid Dynamics Laboratory （GFDL） has simulated climate changes for the area during the past 250 years driven by c^imatic forces, providing scenarios of extreme climate that can further diagnose the mechanisms. This study refined the drought signals from the tree ring data and GFDL modeling at inter-annual and decadal time scales and analyzed the potential mecha- nisms driving the droughts. Results showed that drought years with summer precipitation Ilower than the 10th per- centiles occurred during 1777-1789, 1847-1861 and 1886-1879 AD in the area. Both tree rings and model re- vealed that the frequency of droughts has been relatively consistent in a similar timing andl frequency with climate change. Monte Carlo analysis have detected that the tree ring chronologies have recorded drought years with probabilities of 9.3%-12.8%, and the model has simulated the droughts with probabilities 5..7%-17.8%. Under CO2 and aerosol forcing, the GFDL modeled the drought recurrences of 13 years and 25 years, which are very syn- chronous changes with tree rings and consistent with gauge records. The 20-a and 10-a time scale reoccurrences of droughts are very consistent with solar radiation cycles, and similar to the length of cycles in oceanic records, suggesting that terrestrial precipitation modeling is properly driven from sun-land-sea dynamics. Detected severity, variability and return periods of droughts from the present study make potential improvements in drought predictions and constructing scenarios for climate impacts and adaptation strategies.展开更多
Litchi downy blight,caused by the plant pathogenic oomycete Peronophythora litchii,is one of the most devastating diseases on litchi and resulted in huge economic losses.Autophagy plays an essential role in the develo...Litchi downy blight,caused by the plant pathogenic oomycete Peronophythora litchii,is one of the most devastating diseases on litchi and resulted in huge economic losses.Autophagy plays an essential role in the development and pathogenicity of the filamentous fungi.However,the function of autophagy in oomycetes remain elusive.Here,an autophagy-related protein Atg3 homolog PlAtg3 was identified and characterized in P.litchii.The absence of PlATG3 through the CRISPR/Cas9 gene replacement strategy compromised vegetative growth and sexual/asexual development.Cytological analyses revealed that the deletion of PlATG3 impaired autophagosome formation with monodansylcadaverine(MDC)staining and significantly disrupted zoospore release due to defects of sporangial cleavage with FM4-64 staining.Atg8 is considered to be an autophagy marker protein in various species.Western blot analysis indicated that PlAtg3 is involved in degradation of PlAtg8-PE.Interestingly,PlAtg3 was unable to interact with PlAtg8 in yeast two hybrid(Y2H)assays,possibly due to the absence of the Atg8 family interacting motif(AIM)in PlAtg3.Furthermore,pathogenicity assays revealed that the deletion of PlATG3 considerably reduced the virulence of P.litchii.Taken together,our data reveal that PlAtg3 plays an important role in radial growth,asexual/sexual development,sporangial cleavage and zoospore release,autophagosome formation,and pathogenicity in P.litchii.This study contributes to a better understanding of the pathogenicity mechanisms of P.litchii and provides insights for the development of more effective strategies to control oomycete diseases.展开更多
Dear editor,Acute massive pulmonary embolism(PE) is a common life-threatening disease with high mortality of up to 30%–50%.[1,2]Potential heterogeneous reasons for PE remain controversial, and its treatment strategie...Dear editor,Acute massive pulmonary embolism(PE) is a common life-threatening disease with high mortality of up to 30%–50%.[1,2]Potential heterogeneous reasons for PE remain controversial, and its treatment strategies mainly include antithrombotics, fibrinolytics, and embolectomy.展开更多
基金Supported by the State Key Laboratory of Acoustics and Marine Information Chinese Academy of Sciences(SKL A202507).
文摘Accurate time delay estimation of target echo signals is a critical component of underwater target localization.In active sonar systems,echo signal processing is vulnerable to the effects of reverberation and noise in the maritime environment.This paper proposes a novel method for estimating target time delay using multi-bright spot echoes,assuming the target’s size and depth are known.Aiming to effectively enhance the extraction of geometric features from the target echoes and mitigate the impact of reverberation and noise,the proposed approach employs the fractional order Fourier transform-frequency sliced wavelet transform to extract multi-bright spot echoes.Using the highlighting model theory and the target size information,an observation matrix is constructed to represent multi-angle incident signals and obtain the theoretical scattered echo signals from different angles.Aiming to accurately estimate the target’s time delay,waveform similarity coefficients and mean square error values between the theoretical return signals and received signals are computed across various incident angles and time delays.Simulation results show that,compared to the conventional matched filter,the proposed algorithm reduces the relative error by 65.9%-91.5%at a signal-to noise ratio of-25 dB,and by 66.7%-88.9%at a signal-to-reverberation ratio of−10 dB.This algorithm provides a new approach for the precise localization of submerged targets in shallow water environments.
基金supported by the National Natural Science Foundation of China under Grant No.61672143 and 61662057the Fundamental Research Funds for the Central Universities under Grant No.N2017005the Natural Science Foundation of Liaoning Province under Grant No.2020-BS-054.
文摘Due to the complexity of blockchain technology,it usually costs too much effort to build,maintain and monitor a blockchain system that supports a targeted application.To this end,the emerging“Blockchain as a Service”(BaaS)makes the blockchain and distributed ledgers more accessible,particularly for businesses,by reducing costs and overheads.BaaS combines the high computing power of cloud computing,the pervasiveness of IoT and the decentralization of blockchain,allowing people to build their own applications while ensuring the transparency and openness of the system.This paper surveys the research outputs of both academia and industry.First,it introduces the representative architectures of BaaS systems and then summarizes the research contributions of BaaS from the technologies for service provision,roles,container and virtualization,interfaces,customization and evaluation.The typical applications of BaaS in both academic and practical domains are also introduced.At present,the research on the blockchain is abundant,but research on BaaS is still in its infancy.Six challenges of BaaS are concluded in this paper for further study directions.
基金Financial support for this work was provided by Global Change Research Program of the Ministry of Science and Technology of China (2012CB956103)International Partnership Program and External Cooperation Program of the Chinese Academy of Sciences (KZZD-EW-TZ-08,GJHZ1214)Key Directional Program of the Chinese Academy of Sciences (KZCX2-YW-338-2)
文摘The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- verity shown by the gauge record. A general circulation model of the Geophysical Fluid Dynamics Laboratory （GFDL） has simulated climate changes for the area during the past 250 years driven by c^imatic forces, providing scenarios of extreme climate that can further diagnose the mechanisms. This study refined the drought signals from the tree ring data and GFDL modeling at inter-annual and decadal time scales and analyzed the potential mecha- nisms driving the droughts. Results showed that drought years with summer precipitation Ilower than the 10th per- centiles occurred during 1777-1789, 1847-1861 and 1886-1879 AD in the area. Both tree rings and model re- vealed that the frequency of droughts has been relatively consistent in a similar timing andl frequency with climate change. Monte Carlo analysis have detected that the tree ring chronologies have recorded drought years with probabilities of 9.3%-12.8%, and the model has simulated the droughts with probabilities 5..7%-17.8%. Under CO2 and aerosol forcing, the GFDL modeled the drought recurrences of 13 years and 25 years, which are very syn- chronous changes with tree rings and consistent with gauge records. The 20-a and 10-a time scale reoccurrences of droughts are very consistent with solar radiation cycles, and similar to the length of cycles in oceanic records, suggesting that terrestrial precipitation modeling is properly driven from sun-land-sea dynamics. Detected severity, variability and return periods of droughts from the present study make potential improvements in drought predictions and constructing scenarios for climate impacts and adaptation strategies.
基金supported by the grants from the Hainan Provincial Natural Science Foundation,China(321QN190 and 321CXTD437)the National Natural Science Foundation of China(32202246 and 32160614)+1 种基金the Open Project Program of Fujian Key Laboratory for Monitoring and Integrated Management of Crop Pests,China(MIMCP-202102)the Scientific Research Foundation of Hainan University,China(KYQD(ZR)-21042 and KYQD(ZR)-20080)。
文摘Litchi downy blight,caused by the plant pathogenic oomycete Peronophythora litchii,is one of the most devastating diseases on litchi and resulted in huge economic losses.Autophagy plays an essential role in the development and pathogenicity of the filamentous fungi.However,the function of autophagy in oomycetes remain elusive.Here,an autophagy-related protein Atg3 homolog PlAtg3 was identified and characterized in P.litchii.The absence of PlATG3 through the CRISPR/Cas9 gene replacement strategy compromised vegetative growth and sexual/asexual development.Cytological analyses revealed that the deletion of PlATG3 impaired autophagosome formation with monodansylcadaverine(MDC)staining and significantly disrupted zoospore release due to defects of sporangial cleavage with FM4-64 staining.Atg8 is considered to be an autophagy marker protein in various species.Western blot analysis indicated that PlAtg3 is involved in degradation of PlAtg8-PE.Interestingly,PlAtg3 was unable to interact with PlAtg8 in yeast two hybrid(Y2H)assays,possibly due to the absence of the Atg8 family interacting motif(AIM)in PlAtg3.Furthermore,pathogenicity assays revealed that the deletion of PlATG3 considerably reduced the virulence of P.litchii.Taken together,our data reveal that PlAtg3 plays an important role in radial growth,asexual/sexual development,sporangial cleavage and zoospore release,autophagosome formation,and pathogenicity in P.litchii.This study contributes to a better understanding of the pathogenicity mechanisms of P.litchii and provides insights for the development of more effective strategies to control oomycete diseases.
基金This work was partly supported by grant from the Youth Fund of National Natural Science Foundation of China(81800441)Start-up Fund from Shanghai Fourth People’s Hospital Affiliated to Tongji University,Clinical Science and Technology Innovation Project of Shanghai Hospital Development Center,Construction and Application of Emergency and Critical Care Integrated Management Mode(SHDC22021211).
文摘Dear editor,Acute massive pulmonary embolism(PE) is a common life-threatening disease with high mortality of up to 30%–50%.[1,2]Potential heterogeneous reasons for PE remain controversial, and its treatment strategies mainly include antithrombotics, fibrinolytics, and embolectomy.
