Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and t...Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis.This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.Methods Seventy-two adult patients were examined by Gemstone Spectral CT.They were randomly divided into six groups.We set up a different value of noise index （NI） when evaluating each group every other number from 13.0 to 23.0.The original images were acquired with a slice of 5 mm thickness.For each group,several image series were reconstructed using different levels of adaptive statistical iterative reconstruction （ASIR） （30％,50％,and 70％）.We got a total of 18 image sequences of different combinations of NI and ASIR percentage.On one hand,quantitative indicators,such as CT value and standard deviation （SD）,were assessed at the region of interest.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were calculated.The volume CT dose index （CTDI） and dose length product （DLP） were recorded.On the other hand,two radiologists with ＞5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.Results The different combinations of noise index and ASIR were assessed.There was no significant difference in CT values among the 18 image sequences.The SD value was reduced with the noise index＇s reduction or ASIR＇s increase.There was a trend towards gradually lower SNR and CNR with an NI increase.The CTDI and DLP were diminishing as the NI increased.The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.Conclusions Increasing NI can reduce radiation dose.With the premise of maintaining the same image quality,using a suitable percentage of ASIR can inc展开更多
Seven-degree-of-freedom redundant manipulators with link offset have many advantages,including obvious geometric significance and suitability for configuration control.Their configuration is similar to that of the exp...Seven-degree-of-freedom redundant manipulators with link offset have many advantages,including obvious geometric significance and suitability for configuration control.Their configuration is similar to that of the experimental module manipulator(EMM)in the Chinese Space Station Remote Manipulator System.However,finding the analytical solution of an EMM on the basis of arm angle parameterization is difficult.This study proposes a high-precision,semi-analytical inverse method for EMMs.Firstly,the analytical inverse kinematic solution is established based on joint angle parameterization.Secondly,the analytical inverse kinematic solution for a non-offset spherical-roll-spherical(SRS)redundant manipulator is derived based on arm angle parameterization.The approximate solution of the EMM is calculated in accordance with the relationship between the joint angles of the EMM and the SRS manipulator.Thirdly,the error is corrected using a numerical method through the analytical inverse solution based on joint angle parameterization.After selecting the stride and termination condition,the precise inverse solution is computed for the EMM based on arm angle parameterization.Lastly,case solutions confirm that this method has high precision,and the arm angle parameterization method is superior to the joint angle parameterization method in terms of parameter selection.展开更多
Of the more than 370000 species of higher plants in nature,fewer than 0.1%can be geneticallymodified due to limitations of the current gene delivery systems.Even for those that can be genetically modified,the modifica...Of the more than 370000 species of higher plants in nature,fewer than 0.1%can be geneticallymodified due to limitations of the current gene delivery systems.Even for those that can be genetically modified,the modification involves a tedious and costly tissue culture process.Here,we describe an extremely simple cut-dip-budding(CDB)delivery system,which uses Agrobacterium rhizogene to inoculate explants,generating transformed roots that produce transformed buds due to root suckering.We have successfully used CDB to achieve the heritable transformation of plant species inmultiple plant families,including two herbaceous plants(Taraxacum kok-saghyz and Coronilla varia),a tuberous root plant(sweet potato),and three woody plant species(Ailanthus altissima,Aralia elata,and Clerodendrum chinense).These plants have previously been difficult or impossible to transform,but the CDB method enabled efficient transformation or gene editing in them using a very simple explant dipping protocol,under non-sterile conditions and without the need for tissue culture.Our work suggests that large numbers of plants could be amenable to genetic modifications using the CDB method.展开更多
The contact fatigue of aviation gears has become more prominent with greater demands for heavy-duty and high-power density gears.Meanwhile,the coexistence of tooth contact fatigue damage and tooth profile wear leads t...The contact fatigue of aviation gears has become more prominent with greater demands for heavy-duty and high-power density gears.Meanwhile,the coexistence of tooth contact fatigue damage and tooth profile wear leads to a complicated competitive mechanism between surface-initiated failure and subsurface-initiated contact fatigue failures.To address this issue,a fatigue-wear coupling model of an aviation gear pair was developed based on the elastic-plastic finite element method.The tooth profile surface roughness was considered,and its evolution during repeated meshing was simulated using the Archard wear formula.The fatigue damage accumulation of material points on and underneath the contact surface was captured using the Brown-Miller-Morrow multiaxial fatigue criterion.The elastic-plastic constitutive behavior of damaged material points was updated by incorporating the damage variable.Variations in the wear depth and fatigue damage around the pitch point are described,and the effect of surface roughness on the fatigue life is addressed.The results reveal that whether fatigue failure occurs initially on the surface or sub-surface depends on the level of surface roughness.Mild wear on the asperity level alleviates the local stress concentration and leads to a longer surface fatigue life compared with the result without wear.展开更多
Motion planning is a vital module for unmanned aerial vehicles(UAVs),especially in scenarios of autonomous navigation and operation.This survey delivers some recent state-of-the-art UAV motion planning algorithms and ...Motion planning is a vital module for unmanned aerial vehicles(UAVs),especially in scenarios of autonomous navigation and operation.This survey delivers some recent state-of-the-art UAV motion planning algorithms and related applications.The logic flow of this survey is divided as the path finding,which is the front-end of most motion planning systems,and the trajectory optimisation,which usually serves as the back-end.Motivation,methodology,problem formulation and derivation are given in this survey,in detail.Finally,a section about real-world applications is given,where roles and effectiveness of most popular motion planning methods are revealed.展开更多
The reviving use of lithium metal anode(LMA)is one of the most promising ways to upgrade the energy density of lithium ion batteries.In the roadmap towards the real use,besides the formation of the dendrite,various ad...The reviving use of lithium metal anode(LMA)is one of the most promising ways to upgrade the energy density of lithium ion batteries.In the roadmap towards the real use,besides the formation of the dendrite,various adverse reactions due to the high activity of LMA when exposed to air or the electrolyte limit its practical applications.Learning from the packaging technology in electronic industry,we propose a wax-based coating compositing with the ion conducting poly(ethylene oxide)by a simple dip-coating technology and the prepared LMA is featured with an air-stable and waterproof surface.The LMA thus remains stable for 24 h in ambient air even with the relative humidity of 70% while retaining about85% its electrochemical capacity.More importantly,the LMA is accessible to water and when dipping in water,no obvious adverse reactions or capacity decay is observed.With the composite coating,a steady cycling performance for 500 h in symmetrical cells and a low capacity decay rate of 0.075% per cycle after 300 cycles in lithium-sulfur batteries assembled with the packaged anode have been achieved.This work demonstrates a very simple and effective LMA package technology which is easily scalable and is very promising for speeding up the industrialization of lithium-sulfur batteries and shows potentials for the large-scale production of air-sensitive electrode materials not limited to LMAs.展开更多
Tuberculosis has become a major public health and social problem threatening human health, and a large proportion of pulmonary tuberculosis patients are associated with tuberculous pleurisy (TP). Therefore, it is of g...Tuberculosis has become a major public health and social problem threatening human health, and a large proportion of pulmonary tuberculosis patients are associated with tuberculous pleurisy (TP). Therefore, it is of great significance to find markers with high specificity and sensitivity for the rapid and accurate diagnosis and differential diagnosis of TP under the severe background of high infectivity and mortality due to the occult nature of TP. The extraction of microRNA (miRNA) from pleural effusion satisfies the characteristics of strong operability. miRNA exists not only in cells, but also in various body fluids and participates in the pathophysiological process of various diseases including infectious diseases. miRNA is a highly specific biomarker in pleural fluid in patients with TP. Therefore, this article provides a review of the research progress of mRNA in tuberculous pleurisy.展开更多
Identified as the pathogenic genes of Alzheimer's disease(AD),APP,PSEN1,and PSEN2 mainly lead to early-onset AD,whose course is more aggressive,and atypical symptoms are more common than sporadic AD.Here,a novel m...Identified as the pathogenic genes of Alzheimer's disease(AD),APP,PSEN1,and PSEN2 mainly lead to early-onset AD,whose course is more aggressive,and atypical symptoms are more common than sporadic AD.Here,a novel missense mutation,APP E674Q(also named“Shanghai APP”),was detected in a Chinese index patient with typical late-onset AD(LOAD)who developed memory decline in his mid-70s.The results from neuroimaging were consistent with AD,where widespread amyloidβdeposition was demonstrated in 18 F-florbetapir Positron Emission Tomography(PET).APP E674Q is close to theβ-secretase cleavage site and the well-studied Swedish APP mutation(KM670/671NL),which was predicted to be pathogenic in silico.Molecular dynamics simulation indicated that the E674Q mutation resulted in a rearrangement of the interaction mode between APP and BACE1 and that the E674Q mutation was more prone to cleavage by BACE1.The in vitro results suggested that the E674Q mutation was pathogenic by facilitating the BACE1-mediated processing of APP and the production of Aβ.Furthermore,we applied an adeno-associated virus(AAV)-mediated transfer of the human E674Q mutant APP gene to the hippocampi of two-month-old C57Bl/6 J mice.AAV-E674Q-injected mice exhibited impaired learning behavior and increased pathological burden in the brain,implying that the E674Q mutation had a pathogenicity that bore a comparison with the classical Swedish mutation.Collectively,we report a strong amyloidogenic effect of the E674Q substitution in AD.To our knowledge,E674Q is the only pathogenic mutation within the amyloid processing sequence causing LOAD.展开更多
Background:Vaccination has been the most important measure to mitigate the COVID-19 pandemic.The vaccination coverage was relatively low in Hong Kong Special Administrative Region China,compared to Singapore,in early ...Background:Vaccination has been the most important measure to mitigate the COVID-19 pandemic.The vaccination coverage was relatively low in Hong Kong Special Administrative Region China,compared to Singapore,in early 2022.Hypothetically,if the two regions,Hong Kong(HK)and Singapore(SG),swap their vaccination coverage rate,what outcome would occur?Method:We adopt the Susceptible e Vaccinated e Exposed e Infectious e Hospitalized e Death-Recovered model with a time-varying transmission rate and fit the model to weekly reported COVID-19 deaths(the data up to 2022 Nov 4)in HK and SG using R package POMP.After we obtain a reasonable fitting,we rerun our model with the estimated parameter values and swap the vaccination rates between HK and SG to explore what would happen.Results:Our model fits the data well.The reconstructed transmission rate was higher in HK than in SG in 2022.With a higher vaccination rate as in SG,the death total reported in HK would decrease by 37.5%and the timing of the peak would delay by 3 weeks.With a lower vaccination rate as in HK,the death total reported in SG would increase to 5.5-fold high with a peak 6 weeks earlier than the actual during the Delta variant period.Conclusions:Vaccination rate changes in HK and SG may lead to very different outcomes.This is likely due that the estimated transmission rates were very different in HK and SG which reflect the different control policies and dominant variants.Because of strong control measures,HK avoided large-scale community transmission of the Delta variant.Given the high breakthrough infection rate and transmission rate of the Omicron variant,increasing the vaccination rate in HK will likely yield a mild(but significant)contribution in terms of lives saved.While in SG,lower vaccination coverage to the level of HK will be disastrous.展开更多
In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath scattering.The performance...In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath scattering.The performance of the radar detection methods under sea clutter,multipath,and combined conditions is categorized and summarized,and future research directions are outlined to enhance radar detection performance for low-altitude targets in maritime environments.展开更多
Encouraging and astonishing developments have recently been achieved in image-based diagnostic technology.Modern medical care and imaging technology are becoming increasingly inseparable.However,the current diagnosis ...Encouraging and astonishing developments have recently been achieved in image-based diagnostic technology.Modern medical care and imaging technology are becoming increasingly inseparable.However,the current diagnosis pattern of signal to image to knowledge inevitably leads to information distortion and noise introduction in the procedure of image reconstruction(from signal to image).Artificial intelligence(AI)technologies that can mine knowledge from vast amounts of data offer opportunities to disrupt established workflows.In this prospective study,for the first time,we develop an AI-based signal-toknowledge diagnostic scheme for lung nodule classification directly from the computed tomography(CT)raw data(the signal).We find that the raw data achieves almost comparable performance with CT,indicating that it is possible to diagnose diseases without reconstructing images.Moreover,the incorporation of raw data through three common convolutional network structures greatly improves the performance of the CT models in all cohorts(with a gain ranging from 0.01 to 0.12),demonstrating that raw data contains diagnostic information that CT does not possess.Our results break new ground and demonstrate the potential for direct signal-to-knowledge domain analysis.展开更多
An AI-empowered indoor digital contact-tracing system was developed using a centralized architecture and advanced low-energy Bluetooth technologies for indoor positioning,with careful preservation of privacy and data ...An AI-empowered indoor digital contact-tracing system was developed using a centralized architecture and advanced low-energy Bluetooth technologies for indoor positioning,with careful preservation of privacy and data security.We analyzed the contact pattern data from two RCHs and investigated a COVID-19 outbreak in one study site.To evaluate the effectiveness of the system in containing outbreaks with minimal contacts under quarantine,a simulation study was conducted to compare the impact of different quarantine strategies on outbreak containment within RCHs.The significant difference in contact hours between weekdays and weekends was observed for some pairs of RCH residents and staff during the two-week data collection period.No significant difference between secondary cases and uninfected contacts was observed in a COVID-19 outbreak in terms of their demographics and contact patterns.Simulation results based on the collected contact data indicated that a threshold of accumulative contact hours one or two days prior to diagnosis of the index case could dramatically increase the efficiency of outbreak containment within RCHs by targeted isolation of the close contacts.This study demonstrated the feasibility and efficiency of employing an AI-empowered system in indoor digital contact tracing of outbreaks in RCHs in the post-pandemic era.展开更多
The effects of polyaluminum chloride（PACl） hydrolysis prior to coagulation on both the coagulation zone and coagulation performance of a kaolin suspension were investigated by a novel jar test named the ＂reversed c...The effects of polyaluminum chloride（PACl） hydrolysis prior to coagulation on both the coagulation zone and coagulation performance of a kaolin suspension were investigated by a novel jar test named the ＂reversed coagulation test＂.The tests showed that PACl hydrolysis prior to coagulation decreased the performance of charge neutralization coagulation in the case of short-time slow mixing（10 min;G = 15 sec-1） and increased the optimal dosage for charge neutralization and sweep coagulation.Moreover,the hydrolysis time had insignificant effects on the size and zeta potential of PACl precipitates and the residual turbidity of the raw water.However,PACl hydrolysis prior to coagulation and the size of PACl precipitates had a negligible effect on the performance of sweep coagulation.The results imply that,in practice,preparing a PACl solution with deionized water,rather than tap water or the outlet water from a wastewater treatment unit,can significantly save PACl consumption and improve the performance of charge neutralization coagulation,while preparing the PACl solution with tap or outlet water would not affect the performance of sweep coagulation.In addition,the optimal rapid mixing intensity appears to be determined by a balance between the degree of coagulant hydrolysis before contacting the primary particles and the average size of flocs in the rapid mixing period.These results provide new insights into the role of PACl hydrolysis and will be useful for improving coagulation efficiency.展开更多
The non-uniform temperature distribution in supercritical CO_(2)(Sc-CO_(2))fracturing influences the density,viscosity,and volume expansion or shrinkage rate of Sc-CO_(2),impacting proppant migration.This study presen...The non-uniform temperature distribution in supercritical CO_(2)(Sc-CO_(2))fracturing influences the density,viscosity,and volume expansion or shrinkage rate of Sc-CO_(2),impacting proppant migration.This study presents a coupled computational fluid dynamics-discrete element method and heat transfer model to examine the effects of proppant bed shape and the heat transfers of proppant-wall,proppant-fluid,and fluid-wall on the fluid and proppant temperature fields.The Sc-CO_(2)volume expansion is assessed under various temperature conditions by evaluating the volume-averaged Sc-CO_(2)density.Several factors,including proppant size,shape,thermal conductivity,concentration,temperature difference,and injection velocity,are carefully analyzed to elucidate their impacts.The findings elucidate the existence of four distinct zones in the fluid temperature field.Each zone exhibits different magnitudes of temperature change under diverse conditions and undergoes dynamic transformations with the development of the proppant bed.The fluid-wall heat transfer and the fluid temperatures in Zones C and D are significantly subject to the fluid injection velocity(governing the heating duration),the temperature difference between fluid and formation(impacting the magnitude of heat flux),and the proppant bed shape(controlling the effective heating area).Additionally,the proppant-wall and proppant-fluid heat transfers determine the temperatures of both the proppant bed and the fluid within Zone B,showing a strong correlation with proppant thermal conductivity,proppant size,injection velocity,and temperature difference.The proposed coupled model provides valuable insights into the temperature distributions and flow behaviors of temperature-dependent fracturing fluids and proppants.展开更多
Cities play a vital role in social development,which contribute to more than 70%of global carbon emission.Low-carbon city construction and decarbonization of the energy sector are the critical strategies to cope with ...Cities play a vital role in social development,which contribute to more than 70%of global carbon emission.Low-carbon city construction and decarbonization of the energy sector are the critical strategies to cope with the increasingly serious climate change problems,and low-carbon technologies have attracted extensive attention.However,the potential of such technologies to reduce carbon emissions is constrained by various factors,such as space,operational environment,and safety concerns.As an essential territorial natural resource,underground space can provide large-scale and stable space support for existing low-carbon technologies.Integrating underground space and low-carbon technologies could be a promising approach towards carbon neutrality,and hence,warrants further exploration.First,a comprehensive review of the existing low-carbon technologies including the technical bottlenecks is presented.Second,the features of underground space and its low carbon potential are summarized.Moreover,a framework for the underground space based integrated energy system is proposed,including system configuration,operational mechanisms,and the resulting benefits.Finally,the research prospect and key challenges required to be settled are highlighted.展开更多
Y zeolites have moderate microporous pore size, large specific surface area, and good hydrothermal stability, which were widely used in industrial adsorption of volatile organic compounds (VOCs), but the performance o...Y zeolites have moderate microporous pore size, large specific surface area, and good hydrothermal stability, which were widely used in industrial adsorption of volatile organic compounds (VOCs), but the performance of Y zeolites in adsorption of VOCs under high humidity conditions is terrible. In this paper, Y zeolites with different silica-alumina ratios were hydrophobically modified by organosilane and characterized by XRD, FTIR, SEM, BET, NMR. In the experiments of static and dynamic adsorption of VOCs by modified Y zeolites, it can be concluded that the static water adsorption capacity of Y zeolites with silica-aluminum ratio of 5 and 40 after silica modification decreased by 62 wt% and 53 wt%, under the conditions of high humidity, GHSV = 15,000 h<sup>-1</sup>, T = 35°C and initial concentration of toluene C<sub>0</sub> = 5000 mg·m<sup>-3</sup>. The saturation adsorption capacity of toluene was increased from 0.06 g·g<sup>-1</sup>, 0.09 g·g<sup>-1</sup> to 0.15 g·g<sup>-1</sup>, 0.21 g·g<sup>-1</sup>, the adsorption selectivity of Y zeolites for water was reduced and that for toluene was increased after Vapor phase silanization overlay modification. The present modification method might carry out targeted modification of zeolites surface, provide research ideas and guidance under high humidity conditions.展开更多
文摘Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis.This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.Methods Seventy-two adult patients were examined by Gemstone Spectral CT.They were randomly divided into six groups.We set up a different value of noise index （NI） when evaluating each group every other number from 13.0 to 23.0.The original images were acquired with a slice of 5 mm thickness.For each group,several image series were reconstructed using different levels of adaptive statistical iterative reconstruction （ASIR） （30％,50％,and 70％）.We got a total of 18 image sequences of different combinations of NI and ASIR percentage.On one hand,quantitative indicators,such as CT value and standard deviation （SD）,were assessed at the region of interest.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were calculated.The volume CT dose index （CTDI） and dose length product （DLP） were recorded.On the other hand,two radiologists with ＞5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.Results The different combinations of noise index and ASIR were assessed.There was no significant difference in CT values among the 18 image sequences.The SD value was reduced with the noise index＇s reduction or ASIR＇s increase.There was a trend towards gradually lower SNR and CNR with an NI increase.The CTDI and DLP were diminishing as the NI increased.The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.Conclusions Increasing NI can reduce radiation dose.With the premise of maintaining the same image quality,using a suitable percentage of ASIR can inc
基金This work was supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51521003)the Major Research Plan of National Natural Science Foundation of China(Grant No.91848202).
文摘Seven-degree-of-freedom redundant manipulators with link offset have many advantages,including obvious geometric significance and suitability for configuration control.Their configuration is similar to that of the experimental module manipulator(EMM)in the Chinese Space Station Remote Manipulator System.However,finding the analytical solution of an EMM on the basis of arm angle parameterization is difficult.This study proposes a high-precision,semi-analytical inverse method for EMMs.Firstly,the analytical inverse kinematic solution is established based on joint angle parameterization.Secondly,the analytical inverse kinematic solution for a non-offset spherical-roll-spherical(SRS)redundant manipulator is derived based on arm angle parameterization.The approximate solution of the EMM is calculated in accordance with the relationship between the joint angles of the EMM and the SRS manipulator.Thirdly,the error is corrected using a numerical method through the analytical inverse solution based on joint angle parameterization.After selecting the stride and termination condition,the precise inverse solution is computed for the EMM based on arm angle parameterization.Lastly,case solutions confirm that this method has high precision,and the arm angle parameterization method is superior to the joint angle parameterization method in terms of parameter selection.
基金supported by Shandong Shunfeng BiotechnologyCo.Ltd.,Jinan,China.
文摘Of the more than 370000 species of higher plants in nature,fewer than 0.1%can be geneticallymodified due to limitations of the current gene delivery systems.Even for those that can be genetically modified,the modification involves a tedious and costly tissue culture process.Here,we describe an extremely simple cut-dip-budding(CDB)delivery system,which uses Agrobacterium rhizogene to inoculate explants,generating transformed roots that produce transformed buds due to root suckering.We have successfully used CDB to achieve the heritable transformation of plant species inmultiple plant families,including two herbaceous plants(Taraxacum kok-saghyz and Coronilla varia),a tuberous root plant(sweet potato),and three woody plant species(Ailanthus altissima,Aralia elata,and Clerodendrum chinense).These plants have previously been difficult or impossible to transform,but the CDB method enabled efficient transformation or gene editing in them using a very simple explant dipping protocol,under non-sterile conditions and without the need for tissue culture.Our work suggests that large numbers of plants could be amenable to genetic modifications using the CDB method.
基金The work was supported by the National Key R&D Program of China(Grant No.2018YFB2001300).
文摘The contact fatigue of aviation gears has become more prominent with greater demands for heavy-duty and high-power density gears.Meanwhile,the coexistence of tooth contact fatigue damage and tooth profile wear leads to a complicated competitive mechanism between surface-initiated failure and subsurface-initiated contact fatigue failures.To address this issue,a fatigue-wear coupling model of an aviation gear pair was developed based on the elastic-plastic finite element method.The tooth profile surface roughness was considered,and its evolution during repeated meshing was simulated using the Archard wear formula.The fatigue damage accumulation of material points on and underneath the contact surface was captured using the Brown-Miller-Morrow multiaxial fatigue criterion.The elastic-plastic constitutive behavior of damaged material points was updated by incorporating the damage variable.Variations in the wear depth and fatigue damage around the pitch point are described,and the effect of surface roughness on the fatigue life is addressed.The results reveal that whether fatigue failure occurs initially on the surface or sub-surface depends on the level of surface roughness.Mild wear on the asperity level alleviates the local stress concentration and leads to a longer surface fatigue life compared with the result without wear.
基金This work was supported in parts by the National Natural Science Foundation of China under grant no.61973270the Foundation or Innovative Research Groups of the National Natural Science Foundation of China under grant no.61621002the Fundamental Research Funds for Central Universities。
文摘Motion planning is a vital module for unmanned aerial vehicles(UAVs),especially in scenarios of autonomous navigation and operation.This survey delivers some recent state-of-the-art UAV motion planning algorithms and related applications.The logic flow of this survey is divided as the path finding,which is the front-end of most motion planning systems,and the trajectory optimisation,which usually serves as the back-end.Motivation,methodology,problem formulation and derivation are given in this survey,in detail.Finally,a section about real-world applications is given,where roles and effectiveness of most popular motion planning methods are revealed.
基金supported by the National Science Fund for Distinguished Young Scholars, China (51525204)National Natural Science Foundation of China (51772164 and U1601206)+3 种基金Guangdong Natural Science Funds for Distinguished Young Scholar (2017B030306006)Guangdong Special Support Program (2017TQ04C664)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01N111)the Shenzhen Basic Research Project (JCYJ20170412171630020 and JCYJ20170412171359175)
文摘The reviving use of lithium metal anode(LMA)is one of the most promising ways to upgrade the energy density of lithium ion batteries.In the roadmap towards the real use,besides the formation of the dendrite,various adverse reactions due to the high activity of LMA when exposed to air or the electrolyte limit its practical applications.Learning from the packaging technology in electronic industry,we propose a wax-based coating compositing with the ion conducting poly(ethylene oxide)by a simple dip-coating technology and the prepared LMA is featured with an air-stable and waterproof surface.The LMA thus remains stable for 24 h in ambient air even with the relative humidity of 70% while retaining about85% its electrochemical capacity.More importantly,the LMA is accessible to water and when dipping in water,no obvious adverse reactions or capacity decay is observed.With the composite coating,a steady cycling performance for 500 h in symmetrical cells and a low capacity decay rate of 0.075% per cycle after 300 cycles in lithium-sulfur batteries assembled with the packaged anode have been achieved.This work demonstrates a very simple and effective LMA package technology which is easily scalable and is very promising for speeding up the industrialization of lithium-sulfur batteries and shows potentials for the large-scale production of air-sensitive electrode materials not limited to LMAs.
文摘Tuberculosis has become a major public health and social problem threatening human health, and a large proportion of pulmonary tuberculosis patients are associated with tuberculous pleurisy (TP). Therefore, it is of great significance to find markers with high specificity and sensitivity for the rapid and accurate diagnosis and differential diagnosis of TP under the severe background of high infectivity and mortality due to the occult nature of TP. The extraction of microRNA (miRNA) from pleural effusion satisfies the characteristics of strong operability. miRNA exists not only in cells, but also in various body fluids and participates in the pathophysiological process of various diseases including infectious diseases. miRNA is a highly specific biomarker in pleural fluid in patients with TP. Therefore, this article provides a review of the research progress of mRNA in tuberculous pleurisy.
基金supported by grants from the Ministry of Science and Technology of the People's Republic of China(No.2021ZD020180)the Natural Science Foundation of China(No.81971068,81922021,81773635,82073765).
文摘Identified as the pathogenic genes of Alzheimer's disease(AD),APP,PSEN1,and PSEN2 mainly lead to early-onset AD,whose course is more aggressive,and atypical symptoms are more common than sporadic AD.Here,a novel missense mutation,APP E674Q(also named“Shanghai APP”),was detected in a Chinese index patient with typical late-onset AD(LOAD)who developed memory decline in his mid-70s.The results from neuroimaging were consistent with AD,where widespread amyloidβdeposition was demonstrated in 18 F-florbetapir Positron Emission Tomography(PET).APP E674Q is close to theβ-secretase cleavage site and the well-studied Swedish APP mutation(KM670/671NL),which was predicted to be pathogenic in silico.Molecular dynamics simulation indicated that the E674Q mutation resulted in a rearrangement of the interaction mode between APP and BACE1 and that the E674Q mutation was more prone to cleavage by BACE1.The in vitro results suggested that the E674Q mutation was pathogenic by facilitating the BACE1-mediated processing of APP and the production of Aβ.Furthermore,we applied an adeno-associated virus(AAV)-mediated transfer of the human E674Q mutant APP gene to the hippocampi of two-month-old C57Bl/6 J mice.AAV-E674Q-injected mice exhibited impaired learning behavior and increased pathological burden in the brain,implying that the E674Q mutation had a pathogenicity that bore a comparison with the classical Swedish mutation.Collectively,we report a strong amyloidogenic effect of the E674Q substitution in AD.To our knowledge,E674Q is the only pathogenic mutation within the amyloid processing sequence causing LOAD.
基金supported by the Collaborative Research Fund(Grant Number HKU C7123-20G)of the Research Grants Council(RGC)of Hong Kong,China and two projects of Otto Poon Charitable Foundation(Q-CDBA and Q-CDAV).
文摘Background:Vaccination has been the most important measure to mitigate the COVID-19 pandemic.The vaccination coverage was relatively low in Hong Kong Special Administrative Region China,compared to Singapore,in early 2022.Hypothetically,if the two regions,Hong Kong(HK)and Singapore(SG),swap their vaccination coverage rate,what outcome would occur?Method:We adopt the Susceptible e Vaccinated e Exposed e Infectious e Hospitalized e Death-Recovered model with a time-varying transmission rate and fit the model to weekly reported COVID-19 deaths(the data up to 2022 Nov 4)in HK and SG using R package POMP.After we obtain a reasonable fitting,we rerun our model with the estimated parameter values and swap the vaccination rates between HK and SG to explore what would happen.Results:Our model fits the data well.The reconstructed transmission rate was higher in HK than in SG in 2022.With a higher vaccination rate as in SG,the death total reported in HK would decrease by 37.5%and the timing of the peak would delay by 3 weeks.With a lower vaccination rate as in HK,the death total reported in SG would increase to 5.5-fold high with a peak 6 weeks earlier than the actual during the Delta variant period.Conclusions:Vaccination rate changes in HK and SG may lead to very different outcomes.This is likely due that the estimated transmission rates were very different in HK and SG which reflect the different control policies and dominant variants.Because of strong control measures,HK avoided large-scale community transmission of the Delta variant.Given the high breakthrough infection rate and transmission rate of the Omicron variant,increasing the vaccination rate in HK will likely yield a mild(but significant)contribution in terms of lives saved.While in SG,lower vaccination coverage to the level of HK will be disastrous.
基金supported by the National Natural Science Foundation of China(62171447)。
文摘In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath scattering.The performance of the radar detection methods under sea clutter,multipath,and combined conditions is categorized and summarized,and future research directions are outlined to enhance radar detection performance for low-altitude targets in maritime environments.
基金supported by the National Key Research and Development Program of China (2017YFA0205200,2023YFC2415200,2021YFF1201003,and 2021YFC2500402)the National Natural Science Foundation of China (82022036,91959130,81971776,62027901,81930053,81771924,62333022,82361168664,62176013,and 82302317)+5 种基金the Beijing Natural Science Foundation (Z20J00105)Strategic Priority Research Program of Chinese Academy of Sciences (XDB38040200)Chinese Academy of Sciences (GJJSTD20170004 and QYZDJ-SSW-JSC005)the Project of High-Level Talents Team Introduction in Zhuhai City (Zhuhai HLHPTP201703)the Youth Innovation Promotion Association CAS (Y2021049)the China Postdoctoral Science Foundation (2021M700341).
文摘Encouraging and astonishing developments have recently been achieved in image-based diagnostic technology.Modern medical care and imaging technology are becoming increasingly inseparable.However,the current diagnosis pattern of signal to image to knowledge inevitably leads to information distortion and noise introduction in the procedure of image reconstruction(from signal to image).Artificial intelligence(AI)technologies that can mine knowledge from vast amounts of data offer opportunities to disrupt established workflows.In this prospective study,for the first time,we develop an AI-based signal-toknowledge diagnostic scheme for lung nodule classification directly from the computed tomography(CT)raw data(the signal).We find that the raw data achieves almost comparable performance with CT,indicating that it is possible to diagnose diseases without reconstructing images.Moreover,the incorporation of raw data through three common convolutional network structures greatly improves the performance of the CT models in all cohorts(with a gain ranging from 0.01 to 0.12),demonstrating that raw data contains diagnostic information that CT does not possess.Our results break new ground and demonstrate the potential for direct signal-to-knowledge domain analysis.
基金This study was supported by the Health and Medical Research Fund(HMRF)-Commissioned Research on COVID-19 from the Health Bureau of Hong Kong Special Administrative Region(reference number COVID1903007)the General Research Fund from the University Research Committee(reference number 15603920)the Teaching Development Grant(2022-25)from the Hong Kong Polytechnic University(reference number TDG22-25/VTL-8).
文摘An AI-empowered indoor digital contact-tracing system was developed using a centralized architecture and advanced low-energy Bluetooth technologies for indoor positioning,with careful preservation of privacy and data security.We analyzed the contact pattern data from two RCHs and investigated a COVID-19 outbreak in one study site.To evaluate the effectiveness of the system in containing outbreaks with minimal contacts under quarantine,a simulation study was conducted to compare the impact of different quarantine strategies on outbreak containment within RCHs.The significant difference in contact hours between weekdays and weekends was observed for some pairs of RCH residents and staff during the two-week data collection period.No significant difference between secondary cases and uninfected contacts was observed in a COVID-19 outbreak in terms of their demographics and contact patterns.Simulation results based on the collected contact data indicated that a threshold of accumulative contact hours one or two days prior to diagnosis of the index case could dramatically increase the efficiency of outbreak containment within RCHs by targeted isolation of the close contacts.This study demonstrated the feasibility and efficiency of employing an AI-empowered system in indoor digital contact tracing of outbreaks in RCHs in the post-pandemic era.
基金the Special Fund for the Technical Development of Scientific Research Institutionsfinanced by the Ministry of Science and Technology of the People's Republic of China(Nos.2011EG111307 and 2012EG111122)the Program for Overseas Talents of the Beijing Academy of Science and Technology(No.OTP-2013-015)
文摘The effects of polyaluminum chloride（PACl） hydrolysis prior to coagulation on both the coagulation zone and coagulation performance of a kaolin suspension were investigated by a novel jar test named the ＂reversed coagulation test＂.The tests showed that PACl hydrolysis prior to coagulation decreased the performance of charge neutralization coagulation in the case of short-time slow mixing（10 min;G = 15 sec-1） and increased the optimal dosage for charge neutralization and sweep coagulation.Moreover,the hydrolysis time had insignificant effects on the size and zeta potential of PACl precipitates and the residual turbidity of the raw water.However,PACl hydrolysis prior to coagulation and the size of PACl precipitates had a negligible effect on the performance of sweep coagulation.The results imply that,in practice,preparing a PACl solution with deionized water,rather than tap water or the outlet water from a wastewater treatment unit,can significantly save PACl consumption and improve the performance of charge neutralization coagulation,while preparing the PACl solution with tap or outlet water would not affect the performance of sweep coagulation.In addition,the optimal rapid mixing intensity appears to be determined by a balance between the degree of coagulant hydrolysis before contacting the primary particles and the average size of flocs in the rapid mixing period.These results provide new insights into the role of PACl hydrolysis and will be useful for improving coagulation efficiency.
基金the National Natural Science Foundation of China(grant number 52034010).
文摘The non-uniform temperature distribution in supercritical CO_(2)(Sc-CO_(2))fracturing influences the density,viscosity,and volume expansion or shrinkage rate of Sc-CO_(2),impacting proppant migration.This study presents a coupled computational fluid dynamics-discrete element method and heat transfer model to examine the effects of proppant bed shape and the heat transfers of proppant-wall,proppant-fluid,and fluid-wall on the fluid and proppant temperature fields.The Sc-CO_(2)volume expansion is assessed under various temperature conditions by evaluating the volume-averaged Sc-CO_(2)density.Several factors,including proppant size,shape,thermal conductivity,concentration,temperature difference,and injection velocity,are carefully analyzed to elucidate their impacts.The findings elucidate the existence of four distinct zones in the fluid temperature field.Each zone exhibits different magnitudes of temperature change under diverse conditions and undergoes dynamic transformations with the development of the proppant bed.The fluid-wall heat transfer and the fluid temperatures in Zones C and D are significantly subject to the fluid injection velocity(governing the heating duration),the temperature difference between fluid and formation(impacting the magnitude of heat flux),and the proppant bed shape(controlling the effective heating area).Additionally,the proppant-wall and proppant-fluid heat transfers determine the temperatures of both the proppant bed and the fluid within Zone B,showing a strong correlation with proppant thermal conductivity,proppant size,injection velocity,and temperature difference.The proposed coupled model provides valuable insights into the temperature distributions and flow behaviors of temperature-dependent fracturing fluids and proppants.
基金supported by the consulting research project of Chinese Academy of Engineering(Grant No.2022-XY-76)National Natural Science Foundation of China(Grant No.52177112).
文摘Cities play a vital role in social development,which contribute to more than 70%of global carbon emission.Low-carbon city construction and decarbonization of the energy sector are the critical strategies to cope with the increasingly serious climate change problems,and low-carbon technologies have attracted extensive attention.However,the potential of such technologies to reduce carbon emissions is constrained by various factors,such as space,operational environment,and safety concerns.As an essential territorial natural resource,underground space can provide large-scale and stable space support for existing low-carbon technologies.Integrating underground space and low-carbon technologies could be a promising approach towards carbon neutrality,and hence,warrants further exploration.First,a comprehensive review of the existing low-carbon technologies including the technical bottlenecks is presented.Second,the features of underground space and its low carbon potential are summarized.Moreover,a framework for the underground space based integrated energy system is proposed,including system configuration,operational mechanisms,and the resulting benefits.Finally,the research prospect and key challenges required to be settled are highlighted.
文摘Y zeolites have moderate microporous pore size, large specific surface area, and good hydrothermal stability, which were widely used in industrial adsorption of volatile organic compounds (VOCs), but the performance of Y zeolites in adsorption of VOCs under high humidity conditions is terrible. In this paper, Y zeolites with different silica-alumina ratios were hydrophobically modified by organosilane and characterized by XRD, FTIR, SEM, BET, NMR. In the experiments of static and dynamic adsorption of VOCs by modified Y zeolites, it can be concluded that the static water adsorption capacity of Y zeolites with silica-aluminum ratio of 5 and 40 after silica modification decreased by 62 wt% and 53 wt%, under the conditions of high humidity, GHSV = 15,000 h<sup>-1</sup>, T = 35°C and initial concentration of toluene C<sub>0</sub> = 5000 mg·m<sup>-3</sup>. The saturation adsorption capacity of toluene was increased from 0.06 g·g<sup>-1</sup>, 0.09 g·g<sup>-1</sup> to 0.15 g·g<sup>-1</sup>, 0.21 g·g<sup>-1</sup>, the adsorption selectivity of Y zeolites for water was reduced and that for toluene was increased after Vapor phase silanization overlay modification. The present modification method might carry out targeted modification of zeolites surface, provide research ideas and guidance under high humidity conditions.
