The collision probability computation of space objects plays an important role in space situational awareness,particularly for conjunction assessment and collision avoidance.Early works mainly relied on Monte Carlo si...The collision probability computation of space objects plays an important role in space situational awareness,particularly for conjunction assessment and collision avoidance.Early works mainly relied on Monte Carlo simulations to predict collision probabilities.Although such simulations are accurate when a large number of samples are used,these methods are perceived as computationally intensive,which limits their application in practice.To overcome this limitation,many approximation methods have been developed over the past three decades.This paper presents a comprehensive review of existing space-object collision probability computation methods.The advantages and limitations of different methods are analyzed and a systematic comparison is presented.Advice regarding how to select a suitable method for different short-term encounter scenarios is then provided.Additionally,potential future research avenues are discussed.展开更多
Rendezvous on the geostationary orbit(GEO)is much more complex than that on the low earth orbit and has a higher critical requirement for safety performance.This paper presents a safe scenario design method for GEO re...Rendezvous on the geostationary orbit(GEO)is much more complex than that on the low earth orbit and has a higher critical requirement for safety performance.This paper presents a safe scenario design method for GEO rendezvous proximity missions where the safety constraint of a collocated satellite is considered.A recently proposed quantitative index considering trajectory uncertainty is introduced to analyze the safety performance of the scenario parameters including the V-bar keeping positions and the fly-by trajectory radius.Furthermore,an exhaustive analysis is performed to find the dangerous regions of the V-bar keeping positions and the appropriate semi-major axis of the fly-by ellipse,considering the safety requirements of both the target and the collocated satellite.A geometry method is then developed for designing a feasible and suboptimal safe rendezvous scenario.The method is tested by designing four rendezvous scenarios with±V-bar approach directions respectively in the situations with and without one collocated satellite.Safety performance and velocity increments of the scenarios are compared and a conclusion is reached that the collocated satellite has a significant influence on the scenario design.展开更多
Objective:To assess the efficacy and safety of mulberry twig alkaloids(Sangzhi alkaloids,SZ-A)for treatment of type 2 diabetes in a randomized,double-blind,placebo-controlled multicenter clinical trial.Methods:A total...Objective:To assess the efficacy and safety of mulberry twig alkaloids(Sangzhi alkaloids,SZ-A)for treatment of type 2 diabetes in a randomized,double-blind,placebo-controlled multicenter clinical trial.Methods:A total of 200 patients were randomized to receive SZ-A(n=100)or placebo(n=100)for 16 weeks.The data analysis system for electronic data capture clinical trial central randomization system was used for randomization and dispensing of drugs.The primary outcome was the change in glycosylated hemoglobin(Hb A1c)level.The secondary outcome included the proportions of cases with Hb A1c<7.0%and Hb A1c<6.5%,fasting blood glucose(FBG),postprandial blood glucose(PBG),area under curve for the PBG(AUC_(0-2h)),body weight,and body mass index(BMI).Adverse events(AEs),severe adverse events(SAEs),treatment-related adverse events(TAEs),gastrointestinal disorders(GDs),blood pressure,routine blood tests,and liver and kidney function were monitored.Results:Compared with baseline,the change of Hb A1c at week 16 was-0.80%(95%CI:-0.98%to-0.62%)and-0.09%(95%CI:-0.27%to 0.09%)in SZ-A group and placebo group,respectively.The proportion of patients with Hb A1c<7%and<6.5%was higher in the SZ-A group than in the placebo group(46.8%vs.21.6%and 29.9%vs.10.8%).The observed values and changes in FBG,1 h-PBG,2 h-PBG,and AUC_(0-2h) differed significantly between groups(P<0.001),but differences were not significant in body weight and BMI(P>0.05).The incidence rates of AEs,TAEs,and GDs differed significantly between groups(P=0.010,P=0.005,and P=0.006,respectively),whereas the incidence rates of SAEs showed no significant differences between groups(P=1.000).Conclusion:SZ-A are effective and safe for treatment of type 2 diabetes.展开更多
The usage of state transition tensors(STTs)was proved as an effective method for orbital uncertainty propagation.However,orbital maneuvers and their uncertainties are not considered in current STT-based methods.Uncert...The usage of state transition tensors(STTs)was proved as an effective method for orbital uncertainty propagation.However,orbital maneuvers and their uncertainties are not considered in current STT-based methods.Uncertainty propagation of spacecraft trajectory with maneuvers plays an important role in spaceflight missions,e.g.,the rendezvous phasing mission.Under the effects of impulsive maneuvers,the nominal trajectory of a spacecraft will be divided into several segments.If the uncertainty is piecewise propagated using the STTs one after another,large approximation errors will be introduced.To overcome this challenge,a set of modified STTs is derived,which connects the segmented trajectories together and allows for directly propagating uncertainty from the initial time to the final time.These modified STTs are then applied to analytically propagate the statistical moments of navigation and impulsive maneuver uncertainties.The probability density function is obtained by combining STTs with the Gaussian mixture model.The proposed uncertainty propagator is shown to be efficient and affords good agreement with Monte Carlo simulations.It also has no dimensionality problem for high-dimensional uncertainty propagation.展开更多
PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth. In this study, we produced a series of POSS-modified PEG adhesives with high adhesive strength. Intr...PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth. In this study, we produced a series of POSS-modified PEG adhesives with high adhesive strength. Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth. The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility. Compared with the sutured wounds, the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig, demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.展开更多
Osteoarthritis(OA)is the most common type of degenerative joint disease which affects 7%of the global population and more than 500 million people worldwide.One research frontier is the development of hydrogels for OA ...Osteoarthritis(OA)is the most common type of degenerative joint disease which affects 7%of the global population and more than 500 million people worldwide.One research frontier is the development of hydrogels for OA treatment,which operate either as functional scaffolds of tissue engineering or as delivery vehicles of functional additives.Both approaches address the big challenge:establishing stable integration of such delivery systems or implants.Adhesive hydrogels provide possible solutions to this challenge.However,few studies have described the current advances in using adhesive hydrogel for OA treatment.This review summarizes the commonly used hydrogels with their adhesion mechanisms and components.Additionally,recognizing that OA is a complex disease involving different biological mechanisms,the bioactive therapeutic strategies are also presented.By presenting the adhesive hydrogels in an interdisciplinary way,including both the fields of chemistry and biology,this review will attempt to provide a comprehensive insight for designing novel bioadhesive systems for OA therapy.展开更多
A library of novel 3-aryl isoindolinone derivatives with aromatic amino acid derivative fragments was designed and synthesized. Two synthetic routes were employed to construct 3-aryl isoindolinone ring system for diff...A library of novel 3-aryl isoindolinone derivatives with aromatic amino acid derivative fragments was designed and synthesized. Two synthetic routes were employed to construct 3-aryl isoindolinone ring system for different amino acid derivatives.展开更多
The term space situational awareness(SSA),in a broad sense,refers to the comprehensive knowledge of the near-Earth space environment.It has gained increasing attention as the number of space objects,including the natu...The term space situational awareness(SSA),in a broad sense,refers to the comprehensive knowledge of the near-Earth space environment.It has gained increasing attention as the number of space objects,including the natural and artificial,continues to grow rapidly in recent years and several collisions between them have occurred.One of the main objectives of SSA is to maintain awareness of potentially adversarial space events,in particular collisions,and avoid them.This typically involves tracking and identification of orbiting space objects,predicting their future locations,assessing the collision risk,and removing harmful objects such as debris to improve safety.展开更多
Nonlinear uncertainty propagation is of critical importance in many application fields of astrodynamics. In this article, a framework combining the differential algebra technique and the Gaussian mixture model method ...Nonlinear uncertainty propagation is of critical importance in many application fields of astrodynamics. In this article, a framework combining the differential algebra technique and the Gaussian mixture model method is presented to accurately propagate the state uncertainty of a nonlinear system. A high-order Taylor expansion of the final state with respect to the initial deviations is firstly computed with the differential algebra technique. Then the initial uncertainty is split to a Gaussian mixture model.With the high-order state transition polynomial, each Gaussian mixture element is propagated to the final time, forming the final Gaussian mixture model. Through this framework, the final Gaussian mixture model can include the effects of high-order terms during propagation and capture the non-Gaussianity of the uncertainty, which enables a precise propagation of probability density. Moreover, the manual derivation and integration of the high-order variational equations is avoided, which makes the method versatile. The method can handle both the application of nonlinear analytical maps on any domain of interest and the propagation of initial uncertainties through the numerical integration of ordinary differential equation. The performance of the resulting tool is assessed on some typical orbital dynamic models, including the analytical Keplerian motion, the numerical J_2 perturbed motion,and a nonlinear relative motion.展开更多
This paper presents the method created by the National University of Defense Technology(NUDT)team in the 10th China Trajectory Optimization Competition,which entails a 3-year observation mission of 180 regions on Jupi...This paper presents the method created by the National University of Defense Technology(NUDT)team in the 10th China Trajectory Optimization Competition,which entails a 3-year observation mission of 180 regions on Jupiter.The proposed method can be divided into three steps.First,a preliminary analysis and evaluation via an analytical method is undertaken to decide whether the third subtask of the mission,i.e.,exploring the Galilean moons,should be ignored.Second,a near-optimal orbit for magnetic field observation is designed by solving an analytical equation.Third,a set of observation windows and their sequence are optimized using a customized genetic algorithm.The final index obtained is 354.505,ranking second out of all teams partaking in the competition.展开更多
An efficient synthesis of novel 3-（piperidin-4-yl）isoxazolo[4,5-d]pyrimidine scaffold has been designed and deveopled. A series of 5-phenylurea derivatives was synthesized using this method. Their cytotoxic activiti...An efficient synthesis of novel 3-（piperidin-4-yl）isoxazolo[4,5-d]pyrimidine scaffold has been designed and deveopled. A series of 5-phenylurea derivatives was synthesized using this method. Their cytotoxic activities against breast cancer cell line BT-474 were evaluated by CCK-8 assay. Most of them showed potent anti-proliferative activities, of which compound 20 and 21 exhibited IC50 s of 1.565 mmol/L and1.311 mmol/L, respectively. Furthermore, compound 20 and 21 also showed potent inhibitory activities against PI3 Kd with IC50 s of 0.286 mmol/L and 0.452 mmol/L, respectively. These results indicate that these 3-（piperidin-4-yl）isoxazolo[4,5-d]pyrimidine derivatives are novel antitumor agents through the inhibition of PI3 Kd.展开更多
A novel simplified parametric model for long-duration impulsive orbit rendezvous is proposed.Based on an existing fast estimation method,the optimal impulses and trajectory can be expressed by only ten parameters whos...A novel simplified parametric model for long-duration impulsive orbit rendezvous is proposed.Based on an existing fast estimation method,the optimal impulses and trajectory can be expressed by only ten parameters whose initial values can be easily determined.Then,these parameters are used to predict orbital deviations with a target orbit.A simple correction process is designed to sequentially update the parameters based on the J_(2) perturbed analytical dynamic equations of circular orbits.Finally,an iteration loop is formed to obtain the precise parameters and optimal trajectory.The simulation results confirm that the simplified parametric optimization method can be applied to elliptical orbits of small eccentricity and adapts well to both analytical and high-precision dynamics.The deviations could always converge within five iterations and the calculation was more efficient than the existing methods.展开更多
The 10th edition of the Global Trajectory Optimization Competition considered the problem of the galaxy settlement wherein competitors from all over the world were expected to design the trajectories of different sett...The 10th edition of the Global Trajectory Optimization Competition considered the problem of the galaxy settlement wherein competitors from all over the world were expected to design the trajectories of different settler vessels to maximize the given multi-faceted merit function.The synthesis methods used by the winning team,led jointly by the National University of Defense Technology(NUDT)and Xi’an Satellite Control Center(XSCC),are described along with a greedy search method and the improved solution obtained by University of Jena.Specifically,we presented a layout-first topology-second approach that allows an efficient settlement tree search guided by the pre-specified ideal spatial distribution.We also explained how the problem of constructing settlement trees can be modeled as the widely studied minimum spanning tree problem.Furthermore,University of Jena explored the possibility that a greedy search can generate even better settlement trees,based on the same initial conditions,when compared to that of the winning solution.展开更多
基金The authors acknowledge financial support from the National Natural Science Foundation of China(Nos.11902347 and 11972044).
文摘The collision probability computation of space objects plays an important role in space situational awareness,particularly for conjunction assessment and collision avoidance.Early works mainly relied on Monte Carlo simulations to predict collision probabilities.Although such simulations are accurate when a large number of samples are used,these methods are perceived as computationally intensive,which limits their application in practice.To overcome this limitation,many approximation methods have been developed over the past three decades.This paper presents a comprehensive review of existing space-object collision probability computation methods.The advantages and limitations of different methods are analyzed and a systematic comparison is presented.Advice regarding how to select a suitable method for different short-term encounter scenarios is then provided.Additionally,potential future research avenues are discussed.
基金the National Natural Science Foundation of China(Grant Nos.11572345 and 11402257)the National Basic Research Program of China(973 Program,Grant No.2013CB733100).
文摘Rendezvous on the geostationary orbit(GEO)is much more complex than that on the low earth orbit and has a higher critical requirement for safety performance.This paper presents a safe scenario design method for GEO rendezvous proximity missions where the safety constraint of a collocated satellite is considered.A recently proposed quantitative index considering trajectory uncertainty is introduced to analyze the safety performance of the scenario parameters including the V-bar keeping positions and the fly-by trajectory radius.Furthermore,an exhaustive analysis is performed to find the dangerous regions of the V-bar keeping positions and the appropriate semi-major axis of the fly-by ellipse,considering the safety requirements of both the target and the collocated satellite.A geometry method is then developed for designing a feasible and suboptimal safe rendezvous scenario.The method is tested by designing four rendezvous scenarios with±V-bar approach directions respectively in the situations with and without one collocated satellite.Safety performance and velocity increments of the scenarios are compared and a conclusion is reached that the collocated satellite has a significant influence on the scenario design.
基金Supported by the National Major Science and Technology Projects of China(No.2013ZX09101005)。
文摘Objective:To assess the efficacy and safety of mulberry twig alkaloids(Sangzhi alkaloids,SZ-A)for treatment of type 2 diabetes in a randomized,double-blind,placebo-controlled multicenter clinical trial.Methods:A total of 200 patients were randomized to receive SZ-A(n=100)or placebo(n=100)for 16 weeks.The data analysis system for electronic data capture clinical trial central randomization system was used for randomization and dispensing of drugs.The primary outcome was the change in glycosylated hemoglobin(Hb A1c)level.The secondary outcome included the proportions of cases with Hb A1c<7.0%and Hb A1c<6.5%,fasting blood glucose(FBG),postprandial blood glucose(PBG),area under curve for the PBG(AUC_(0-2h)),body weight,and body mass index(BMI).Adverse events(AEs),severe adverse events(SAEs),treatment-related adverse events(TAEs),gastrointestinal disorders(GDs),blood pressure,routine blood tests,and liver and kidney function were monitored.Results:Compared with baseline,the change of Hb A1c at week 16 was-0.80%(95%CI:-0.98%to-0.62%)and-0.09%(95%CI:-0.27%to 0.09%)in SZ-A group and placebo group,respectively.The proportion of patients with Hb A1c<7%and<6.5%was higher in the SZ-A group than in the placebo group(46.8%vs.21.6%and 29.9%vs.10.8%).The observed values and changes in FBG,1 h-PBG,2 h-PBG,and AUC_(0-2h) differed significantly between groups(P<0.001),but differences were not significant in body weight and BMI(P>0.05).The incidence rates of AEs,TAEs,and GDs differed significantly between groups(P=0.010,P=0.005,and P=0.006,respectively),whereas the incidence rates of SAEs showed no significant differences between groups(P=1.000).Conclusion:SZ-A are effective and safe for treatment of type 2 diabetes.
基金the National Natural Science Foundation of China(Nos.11222215 and 11572345)the National Basic Research Program of China(973 Program,No.2013CB733100)the Program for New Century Excellent Talents in University(No.NCET-13-0159).
文摘The usage of state transition tensors(STTs)was proved as an effective method for orbital uncertainty propagation.However,orbital maneuvers and their uncertainties are not considered in current STT-based methods.Uncertainty propagation of spacecraft trajectory with maneuvers plays an important role in spaceflight missions,e.g.,the rendezvous phasing mission.Under the effects of impulsive maneuvers,the nominal trajectory of a spacecraft will be divided into several segments.If the uncertainty is piecewise propagated using the STTs one after another,large approximation errors will be introduced.To overcome this challenge,a set of modified STTs is derived,which connects the segmented trajectories together and allows for directly propagating uncertainty from the initial time to the final time.These modified STTs are then applied to analytically propagate the statistical moments of navigation and impulsive maneuver uncertainties.The probability density function is obtained by combining STTs with the Gaussian mixture model.The proposed uncertainty propagator is shown to be efficient and affords good agreement with Monte Carlo simulations.It also has no dimensionality problem for high-dimensional uncertainty propagation.
基金financially supported by the National Natural Science Foundation of China(Nos.21674120,81630056,21474115)PLA(No.AWS14C003)“Young Thousand Talents Program”
文摘PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth. In this study, we produced a series of POSS-modified PEG adhesives with high adhesive strength. Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth. The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility. Compared with the sutured wounds, the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig, demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.
基金supported by the National Natural Science Foundation of China (52103184, 82102593)the China Postdoctoral Science Foundation (XJ2021051, 2020TQ0129, 2021M693960)+3 种基金the"Young Talent Support Plan"and Funding for Basic Scientific Research of Xi’an Jiaotong Universitysupported by a Grant from Science Foundation Ireland (SFI)co-funded under the European Regional Development Fund (13/RC/2073_P2)the funds received from European Union Horizon 2020 Programme (H2020-MSCA-IF-2017) under the Marie Sklodowska-Curie Individual Fellowship (797716).
文摘Osteoarthritis(OA)is the most common type of degenerative joint disease which affects 7%of the global population and more than 500 million people worldwide.One research frontier is the development of hydrogels for OA treatment,which operate either as functional scaffolds of tissue engineering or as delivery vehicles of functional additives.Both approaches address the big challenge:establishing stable integration of such delivery systems or implants.Adhesive hydrogels provide possible solutions to this challenge.However,few studies have described the current advances in using adhesive hydrogel for OA treatment.This review summarizes the commonly used hydrogels with their adhesion mechanisms and components.Additionally,recognizing that OA is a complex disease involving different biological mechanisms,the bioactive therapeutic strategies are also presented.By presenting the adhesive hydrogels in an interdisciplinary way,including both the fields of chemistry and biology,this review will attempt to provide a comprehensive insight for designing novel bioadhesive systems for OA therapy.
基金Supported by the National Natural Science Foundation of China（No.81072526） and the Fund of the Department of Science and Technology of Jilin Province of China（No.20106039）.
文摘A library of novel 3-aryl isoindolinone derivatives with aromatic amino acid derivative fragments was designed and synthesized. Two synthetic routes were employed to construct 3-aryl isoindolinone ring system for different amino acid derivatives.
文摘The term space situational awareness(SSA),in a broad sense,refers to the comprehensive knowledge of the near-Earth space environment.It has gained increasing attention as the number of space objects,including the natural and artificial,continues to grow rapidly in recent years and several collisions between them have occurred.One of the main objectives of SSA is to maintain awareness of potentially adversarial space events,in particular collisions,and avoid them.This typically involves tracking and identification of orbiting space objects,predicting their future locations,assessing the collision risk,and removing harmful objects such as debris to improve safety.
基金supported by the National Natural Science Foundation of China(Grant No.11572345)
文摘Nonlinear uncertainty propagation is of critical importance in many application fields of astrodynamics. In this article, a framework combining the differential algebra technique and the Gaussian mixture model method is presented to accurately propagate the state uncertainty of a nonlinear system. A high-order Taylor expansion of the final state with respect to the initial deviations is firstly computed with the differential algebra technique. Then the initial uncertainty is split to a Gaussian mixture model.With the high-order state transition polynomial, each Gaussian mixture element is propagated to the final time, forming the final Gaussian mixture model. Through this framework, the final Gaussian mixture model can include the effects of high-order terms during propagation and capture the non-Gaussianity of the uncertainty, which enables a precise propagation of probability density. Moreover, the manual derivation and integration of the high-order variational equations is avoided, which makes the method versatile. The method can handle both the application of nonlinear analytical maps on any domain of interest and the propagation of initial uncertainties through the numerical integration of ordinary differential equation. The performance of the resulting tool is assessed on some typical orbital dynamic models, including the analytical Keplerian motion, the numerical J_2 perturbed motion,and a nonlinear relative motion.
基金This work was supported by the National Natural Science Foundation of China(No.11972044).
文摘This paper presents the method created by the National University of Defense Technology(NUDT)team in the 10th China Trajectory Optimization Competition,which entails a 3-year observation mission of 180 regions on Jupiter.The proposed method can be divided into three steps.First,a preliminary analysis and evaluation via an analytical method is undertaken to decide whether the third subtask of the mission,i.e.,exploring the Galilean moons,should be ignored.Second,a near-optimal orbit for magnetic field observation is designed by solving an analytical equation.Third,a set of observation windows and their sequence are optimized using a customized genetic algorithm.The final index obtained is 354.505,ranking second out of all teams partaking in the competition.
基金supported by the National Natural Science Foundation of China (No. 81172914)Tang Aoqing Professorship research grant from Jilin UniversityChina and Changchun Discovery Sciences, Ltd.
文摘An efficient synthesis of novel 3-（piperidin-4-yl）isoxazolo[4,5-d]pyrimidine scaffold has been designed and deveopled. A series of 5-phenylurea derivatives was synthesized using this method. Their cytotoxic activities against breast cancer cell line BT-474 were evaluated by CCK-8 assay. Most of them showed potent anti-proliferative activities, of which compound 20 and 21 exhibited IC50 s of 1.565 mmol/L and1.311 mmol/L, respectively. Furthermore, compound 20 and 21 also showed potent inhibitory activities against PI3 Kd with IC50 s of 0.286 mmol/L and 0.452 mmol/L, respectively. These results indicate that these 3-（piperidin-4-yl）isoxazolo[4,5-d]pyrimidine derivatives are novel antitumor agents through the inhibition of PI3 Kd.
基金The work was supported by the National Natural Science Foundation of China(No.11972044).
文摘A novel simplified parametric model for long-duration impulsive orbit rendezvous is proposed.Based on an existing fast estimation method,the optimal impulses and trajectory can be expressed by only ten parameters whose initial values can be easily determined.Then,these parameters are used to predict orbital deviations with a target orbit.A simple correction process is designed to sequentially update the parameters based on the J_(2) perturbed analytical dynamic equations of circular orbits.Finally,an iteration loop is formed to obtain the precise parameters and optimal trajectory.The simulation results confirm that the simplified parametric optimization method can be applied to elliptical orbits of small eccentricity and adapts well to both analytical and high-precision dynamics.The deviations could always converge within five iterations and the calculation was more efficient than the existing methods.
基金This study is supported by the National Natural Science Foundation of China(No.11702330)the National Science and Technology Innovation Special Zone Project.
文摘The 10th edition of the Global Trajectory Optimization Competition considered the problem of the galaxy settlement wherein competitors from all over the world were expected to design the trajectories of different settler vessels to maximize the given multi-faceted merit function.The synthesis methods used by the winning team,led jointly by the National University of Defense Technology(NUDT)and Xi’an Satellite Control Center(XSCC),are described along with a greedy search method and the improved solution obtained by University of Jena.Specifically,we presented a layout-first topology-second approach that allows an efficient settlement tree search guided by the pre-specified ideal spatial distribution.We also explained how the problem of constructing settlement trees can be modeled as the widely studied minimum spanning tree problem.Furthermore,University of Jena explored the possibility that a greedy search can generate even better settlement trees,based on the same initial conditions,when compared to that of the winning solution.
