In [7], Cross showed that the spectrum of a linear relation T on a normed space satisfies the spectral mapping theorem. In this paper, we extend the notion of essential ascent and descent for an operator acting on a v...In [7], Cross showed that the spectrum of a linear relation T on a normed space satisfies the spectral mapping theorem. In this paper, we extend the notion of essential ascent and descent for an operator acting on a vector space to linear relations acting on Banach spaces. We focus to define and study the descent, essential descent, ascent and essential ascent spectrum of a linear relation everywhere defined on a Banach space X. In particular, we show that the corresponding spectrum satisfy the polynomial version of the spectral mapping theorem.展开更多
High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adapt...High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adaptability for high dynamics require either complicated structures or prior statistical information of noises.This paper proposes a high dynamics algorithm based on steepest ascent method that can circumvent the deficiencies of existing methods.First,the relationship between the error of carrier tracking and the maximum of Fast Fourier Transform(FFT)outputs is established,and a performance function based on the steepest ascent method is designed.It can keep stable in high dynamics.Second,a new carrier-tracking loop is constructed by deploying the performance function.When the variation of GPS receiver acceleration ranges from 10 g to 100 g,compared with the PLL that either loses lock or keeps tracking accuracy less than 33.89 Hz,the experimental results show that the proposed method can not only keep tracking,but also achieve tracking accuracy more than 2.77 Hz.展开更多
During the Yushu Earthquake on April 14,2010,a large number of rescuers from sea level or lowlands ascended to the quake areas very rapidly or rapidly less than 24 h. However,Yushu Earthquake is the highest quake in t...During the Yushu Earthquake on April 14,2010,a large number of rescuers from sea level or lowlands ascended to the quake areas very rapidly or rapidly less than 24 h. However,Yushu Earthquake is the highest quake in the world at altitudes between 3 750 m and 4 878 m where is a serious hypoxic environment. A high incidence of acute altitude illness was found in the unacclimatized rescuers;the mountain rescue operation changed as "rescue the rescuers". Lesson from the Yushu Earthquake is that the occurrence of acute altitude illness may be closely related to the ascent schedules. This prompted us to study the relationship between ascent rate and the incidence and severity of acute altitude illness;five different groups were compared. The first group was 42 sea level male young soldiers who ascended to quake area very rapidly within 8 h at 4 000 m;the second group was 48 sea level male young soldiers who ascended to 4 000 m rapidly less than 18 h;the third group was 66 acclimatized medical workers from 2 261 m who ascended to 4 000 m rapidly within 12 h;the fourth group was 56 Tibetan medical workers from 2 800 m who ascended to 4 000 m rapidly within 8 h;the fifth group was 50 male sea level workers who ascended to 4 000 m gradually over a period of 4 d. The results showed that the sea level rescuers ascended to 4 000 m very rapidly or rapidly had the highest incidence of acute mountain sickness (AMS) with the greatest AMS scores and the lowest arterial oxygen saturation (SaO2);the sea level workers ascended to 4 000 m gradually had moderate incidence of AMS with moderate AMS scores and SaO2 values;whereas the acclimatized and adapted rescuers had the lowest incidence of AMS,lowest AMS scores and higher SaO2;especially none AMS occurred in Tibetan rescuers. AMS score is inversely related to the ascent rate (r=-0.24,p< 0.001). Additionally,acute altitude illness is significantly influenced by altitude acclimatization. The ascent rate is inversely re- lated to the period of altitude acclimatization whereas the time of perfect recovered from AMS is positively correlated to the time taken to acclimatize. Generally,the best means of preventing acute altitude illness is slow and gradual ascent to high altitude,as this allows time for establishing altitude acclimatization and tolerance to the hypoxic environment. However,during an emergency circumstance,such as mountain rescue operation,the rescuers must rapidly ascend to high altitude,so a series of preventive strategies including pre-acclimatization,using some prophylactic drugs and oxygen supplementary are sorely necessary.展开更多
Highly homogeneous, well dispersed SiO_2@Au@TiO_2(SAT) microspheres decorated with Au nanoparticles(AuNPs) were prepared and incorporated into the photoanode with an optimized concentration gradientascent. The effects...Highly homogeneous, well dispersed SiO_2@Au@TiO_2(SAT) microspheres decorated with Au nanoparticles(AuNPs) were prepared and incorporated into the photoanode with an optimized concentration gradientascent. The effects of SAT microspheres and the gradient-ascent architecture on the light absorption and the photoelectric conversion efficiency(PCE) of the dye-sensitized solar cells(DSSCs) were investigated.Studies indicate that the introduction of SAT microspheres and the gradient-ascent architecture in the photoanode significantly enhance the light scattering and harvesting capability of the photoanode. The DSSC with the optimized SAT gradient-ascent photoanode has the maximum short circuit current density(J_(sc)) of 17.7 mA cm^(-2) and PCE of 7.75%, remarkably higher than those of the conventional DSSC by 23.7%and 28.0%, respectively. This significantly enhancement of the performance of the DSSC can be attributed to the excellent light reflection/scattering of SAT, the localized surface plasma resonance(LSPR) effect of AuNPs within the microspheres, and the gradient-ascent architecture of SAT microspheres inside the photoanode. This study demonstrates that the tri-synergies of the scattering of SAT microspheres, the LSPR of AuNPs and the gradient-ascent architecture can effectively improve the PCE of DSSC.展开更多
This study aimed to compare gait properties during level walking and during stair ascent and descent with varying loads. Fifteen healthy young men (mean age: 22.1 ± 1.6 years) walked while holding four different ...This study aimed to compare gait properties during level walking and during stair ascent and descent with varying loads. Fifteen healthy young men (mean age: 22.1 ± 1.6 years) walked while holding four different loads relative to each subject’s body mass (0, 20, 40 and 60% of body mass: BM) on their backs. Stance time, swing time, and double support times were selected as gait parameters. All parameters showed a maximal value during stair ascent and a minimum value during level walking. Stance and double support times increased significan- tly with each load during level walking and during stair ascent and descent. In conclusion, st- air ascent and descent creates more unstable movement than level walking regardless of the weight of the load. The effect of loads on gait increases with the weight of the load and becomes obvious once the load exceeds 60% of BM.展开更多
In this paper, the ascent of 2 × 2 infinite dimensional Hamiltonian operators and a class of 4 × 4 infinite dimensional Hamiltonian operators are studied, and the conditions under which the ascent of 2 ×...In this paper, the ascent of 2 × 2 infinite dimensional Hamiltonian operators and a class of 4 × 4 infinite dimensional Hamiltonian operators are studied, and the conditions under which the ascent of 2 × 2 infinite dimensional Hamiltonian operator is 1 and the ascent of a class of 4 × 4 infinite dimensional Hamiltonian operators that arises in study of elasticity is2 are obtained. Concrete examples are given to illustrate the effectiveness of criterions.展开更多
We solve two problems about ascent sequences： how to get the ascent sequence of the reflection of A with respect to its antidiagonal for a matrix A ∈ Intn and its ascent sequences, and how to determine the ascent se...We solve two problems about ascent sequences： how to get the ascent sequence of the reflection of A with respect to its antidiagonal for a matrix A ∈ Intn and its ascent sequences, and how to determine the ascent sequence of A＋B for kxk matrices A ∈ Int, and B ∈ Intm. We give the other definition of ascent se- quence and get M-sequence. For the first question, we define M-sequence of A and rewrite the ascent sequences as another form We build the bijection between M-sequences and ascent sequences and prove that our bijection is well-defined. For the second ques- tion, we define an operation on M-sequences. On the basis of the operation and the bijections, we get the ascent sequences of the sum of two matrices.展开更多
Gas chimneys,salt domes,and faults are vital to the movement of hydrocarbons within geological systems.Accurate identification of these geological features is crucial to modeling hydrocarbon resources.This study explo...Gas chimneys,salt domes,and faults are vital to the movement of hydrocarbons within geological systems.Accurate identification of these geological features is crucial to modeling hydrocarbon resources.This study explores the processes that have shaped the eastern Persian Gulf,focusing on salt diapir characteristics,origin,and fluid migration.Plate collisions between the Indian,Eurasian,and Arabian Plates have considerably impacted salt tectonics,developing key features such as the Hormuz salt,Qatar-South Fars Arch,and Zagros and Oman orogenic structures.Salt-related features were discerned through two-dimensional seismic data and drilling records,salt movement sequences were reconstructed,and fluid expulsion patterns were delineated using attribute preferences.The results of this study revealed that fractured substrates influenced by regional tectonic forces contribute to the creation of salt diapirs,which serve as conduits for guided fluid transport.Moreover,these results showed that gravity-driven downbuilding mainly controls salt flow,while the circular arrangement of salt structures results from regional stress and interactions between different salt sources.Distinct stress-induced basement incisions compounded by the hindrance of initial salt movement by the Qatar Arch further contribute to the complex salt structure geometry.Crucially,the uplift of the Qatar Arch and stresses from the Oman and Zagros orogenies profoundly affect the salt structure geometry and depositional patterns across diverse regions,resulting in circular salt structures and gas chimneys.This study offers valuable perspectives for oil and gas exploration and provides a comprehensive understanding of the regional dynamics governing salt tectonics and hydrocarbon ascent in the eastern Persian Gulf.展开更多
In the scenario that a solid-fuel launch vehicle maneuvers in outer space at high angles of attack and sideslip for energy management,Approximate Analytical Solutions(AAS)for the threedimensional(3D)ascent flight stat...In the scenario that a solid-fuel launch vehicle maneuvers in outer space at high angles of attack and sideslip for energy management,Approximate Analytical Solutions(AAS)for the threedimensional(3D)ascent flight states are derived,which are the only solutions capable of considering time-varying Mass Flow Rate(MFR)at present.The uneven MFR makes the thrust vary nonlinearly and thus increases the difficulty of the problem greatly.The AAS are derived based on a 3D Generalized Ascent Dynamics Model(GADM)with a normalized mass as the independent variable.To simplify some highly nonlinear terms in the GADM,several approximate functions are introduced carefully,while the errors of the approximations relative to the original terms are regarded as minor perturbations.Notably,a finite series with positive and negative exponents,called Exponent-Symmetry Series(ESS),is proposed for function approximation to decrease the highest exponent in the AAS so as to reduce computer round-off errors.To calculate the ESS coefficients,a method of seeking the Optimal Interpolation Points(OIP)is proposed using the leastsquares-approximation theory.Due to the artful design of the approximations,the GADM can be decomposed into two analytically solvable subsystems by a perturbation method,and thus the AAS are obtained successfully.Finally,to help implement the AAS,two indirect methods for measuring the remaining mass and predicting the burnout time in flight are put forward using information from accelerometers.Simulation results verify the superiority of the AAS under the condition of time-varying MFR.展开更多
The recent approval of pembrolizumab as second-line treatment for any solid tumor with high-level microsatellite instability or mismatch repair deficiency agnostic of tissue and origin1 has shattered a glass ceiling f...The recent approval of pembrolizumab as second-line treatment for any solid tumor with high-level microsatellite instability or mismatch repair deficiency agnostic of tissue and origin1 has shattered a glass ceiling for immune checkpoint inhibitors.No longer bound to a specific cancer diagnosis but rather a biomarker,pembrolizumab has heightened a burgeoning optimism towards the drug class.Yet how these agents should carve out additional展开更多
To evaluate the effect of acute high-altitude exposure on sensory and short-term memory using interactive software,we transported 30 volunteers in a sport utility vehicle to a 4280 m plateau within3 h.We measured thei...To evaluate the effect of acute high-altitude exposure on sensory and short-term memory using interactive software,we transported 30 volunteers in a sport utility vehicle to a 4280 m plateau within3 h.We measured their memory performance on the plain（initial arrival）and 3 h after arrival on the plateau using six measures.展开更多
Dear Editor,This letter proposes a convex optimization-based model predictive control(MPC)autonomous guidance method for the Mars ascent vehicle(MAV).We use the modified chebyshev-picard iteration(MCPI)to solve optimi...Dear Editor,This letter proposes a convex optimization-based model predictive control(MPC)autonomous guidance method for the Mars ascent vehicle(MAV).We use the modified chebyshev-picard iteration(MCPI)to solve optimization sub-problems within the MPC framework,eliminating the dynamic constraints in solving the optimal control problem and enhancing the convergence performance of the algorithm.Moreover,this method can repeatedly perform trajectory optimization calculations at a high frequency,achieving timely correction of the optimal control command.Numerical simulations demonstrate that the method can satisfy the requirements of rapid computation and reliability for the MAV system when considering uncertainties and perturbations.展开更多
The Brisbane Tropical Cyclone Warning Centre has used two forms of a thermal advection diagnostic to identify relatively large areas of isentropic ascent and descent for many years. When the thermodynamic conditions a...The Brisbane Tropical Cyclone Warning Centre has used two forms of a thermal advection diagnostic to identify relatively large areas of isentropic ascent and descent for many years. When the thermodynamic conditions are favourable the ascent regions are correlated with significant outbreaks of convection that produce heavy rainfall. The diagnostic is based on the relationship between geostrophic winds that turn with height and flow perpendicular to thickness contours. As the relationship is also valid for the more general case of gradient winds, the diagnostic, in theory, should be useful for most heavy-rain-bearing tropical systems. A climatology of rainfall rate with one form of the diagnostic is presented at two Queensland locations(one tropical and one subtropical) that demonstrates a clear relationship between the isentropic ascent wind distribution and heavy to extreme rainfall.The diagnostics applied to numerical weather prediction models are valuable forecast tools as they identify heavy rainfall threat regions within which the extreme rain is likely to fall, whereas the rainfall from the same models is often under predicted or has large location errors. Applied to tropical lows and tropical cyclones the diagnostics have been used successfully to forecast tropical cyclone formation and rapid intensification and decay. Examples of such intensification and decay from around the world are presented, as well as a climatology of the diagnostic applied to intensifying tropical cyclones in the Australian region.展开更多
Purpose Understanding the femur load environment during daily activity is necessary for the understanding of risk of femoral pain,pain related falls,and femoral fractures,which could help the design of osteogenic exer...Purpose Understanding the femur load environment during daily activity is necessary for the understanding of risk of femoral pain,pain related falls,and femoral fractures,which could help the design of osteogenic exercises or the preventa-tive methods for older adults.Methods Using the finite element femur analysis,this study was to estimate the femoral strains at 9 cross-sections along the long axis of femur for stair ascent and descent(n=17;age:50-65 years).Motion analysis and inverse dynamics were com-bined with musculoskeletal modelling and optimization,then were used as input to a 3-D femur model to estimate femoral strains.Strains at the hip contact force peaks were calculated.Results The compressive and tensile strains during stair descent were greater than ascent for all or most cross-sections,especially for the proximal cross-sections of the femur:stair ascent produced−324.0±103.8 to−483.7±191.0μεcompressive strains and descent produced−608.8±288.4 to 1016.0±444.1με;stair ascent produced 336.2±105.4 to 391.8±136.9μεtensile strains and descent produced 546.9±252.8 to 741.7±333.6με.Conclusion Strains represent the material deformation effect on the bone due to the sum of all the bone external loads.Using bone strains could help future studies analyze load conditions in a more comprehensive way for other physical activities,which predicts the risk of stress fractures and tests if alternative methods(gait type change)could reduce stress and strain effectively.展开更多
The SCO charts a course for the future at landmark meetings marking its fifth anniversary The Shanghai Cooperation Organization (SCO) Summit on June 15 received extraordinary media coverage in China. Broadcast live on...The SCO charts a course for the future at landmark meetings marking its fifth anniversary The Shanghai Cooperation Organization (SCO) Summit on June 15 received extraordinary media coverage in China. Broadcast live on state radio and television and on the Internet, the summit made headlines展开更多
文摘In [7], Cross showed that the spectrum of a linear relation T on a normed space satisfies the spectral mapping theorem. In this paper, we extend the notion of essential ascent and descent for an operator acting on a vector space to linear relations acting on Banach spaces. We focus to define and study the descent, essential descent, ascent and essential ascent spectrum of a linear relation everywhere defined on a Banach space X. In particular, we show that the corresponding spectrum satisfy the polynomial version of the spectral mapping theorem.
基金funded by National Natural Science Foundation of China(Nos.61533008,61603181,61673208,61873125)。
文摘High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adaptability for high dynamics require either complicated structures or prior statistical information of noises.This paper proposes a high dynamics algorithm based on steepest ascent method that can circumvent the deficiencies of existing methods.First,the relationship between the error of carrier tracking and the maximum of Fast Fourier Transform(FFT)outputs is established,and a performance function based on the steepest ascent method is designed.It can keep stable in high dynamics.Second,a new carrier-tracking loop is constructed by deploying the performance function.When the variation of GPS receiver acceleration ranges from 10 g to 100 g,compared with the PLL that either loses lock or keeps tracking accuracy less than 33.89 Hz,the experimental results show that the proposed method can not only keep tracking,but also achieve tracking accuracy more than 2.77 Hz.
基金"973"National Key Basic Research and Development Program(No.2012CB518202)Project of Qinghai Development of Science and Technology(No.2011-N-150)
文摘During the Yushu Earthquake on April 14,2010,a large number of rescuers from sea level or lowlands ascended to the quake areas very rapidly or rapidly less than 24 h. However,Yushu Earthquake is the highest quake in the world at altitudes between 3 750 m and 4 878 m where is a serious hypoxic environment. A high incidence of acute altitude illness was found in the unacclimatized rescuers;the mountain rescue operation changed as "rescue the rescuers". Lesson from the Yushu Earthquake is that the occurrence of acute altitude illness may be closely related to the ascent schedules. This prompted us to study the relationship between ascent rate and the incidence and severity of acute altitude illness;five different groups were compared. The first group was 42 sea level male young soldiers who ascended to quake area very rapidly within 8 h at 4 000 m;the second group was 48 sea level male young soldiers who ascended to 4 000 m rapidly less than 18 h;the third group was 66 acclimatized medical workers from 2 261 m who ascended to 4 000 m rapidly within 12 h;the fourth group was 56 Tibetan medical workers from 2 800 m who ascended to 4 000 m rapidly within 8 h;the fifth group was 50 male sea level workers who ascended to 4 000 m gradually over a period of 4 d. The results showed that the sea level rescuers ascended to 4 000 m very rapidly or rapidly had the highest incidence of acute mountain sickness (AMS) with the greatest AMS scores and the lowest arterial oxygen saturation (SaO2);the sea level workers ascended to 4 000 m gradually had moderate incidence of AMS with moderate AMS scores and SaO2 values;whereas the acclimatized and adapted rescuers had the lowest incidence of AMS,lowest AMS scores and higher SaO2;especially none AMS occurred in Tibetan rescuers. AMS score is inversely related to the ascent rate (r=-0.24,p< 0.001). Additionally,acute altitude illness is significantly influenced by altitude acclimatization. The ascent rate is inversely re- lated to the period of altitude acclimatization whereas the time of perfect recovered from AMS is positively correlated to the time taken to acclimatize. Generally,the best means of preventing acute altitude illness is slow and gradual ascent to high altitude,as this allows time for establishing altitude acclimatization and tolerance to the hypoxic environment. However,during an emergency circumstance,such as mountain rescue operation,the rescuers must rapidly ascend to high altitude,so a series of preventive strategies including pre-acclimatization,using some prophylactic drugs and oxygen supplementary are sorely necessary.
基金supported financially by the National Natural Science Foundation of China (Nos.51572102,11504101,11604089 and 11364018)
文摘Highly homogeneous, well dispersed SiO_2@Au@TiO_2(SAT) microspheres decorated with Au nanoparticles(AuNPs) were prepared and incorporated into the photoanode with an optimized concentration gradientascent. The effects of SAT microspheres and the gradient-ascent architecture on the light absorption and the photoelectric conversion efficiency(PCE) of the dye-sensitized solar cells(DSSCs) were investigated.Studies indicate that the introduction of SAT microspheres and the gradient-ascent architecture in the photoanode significantly enhance the light scattering and harvesting capability of the photoanode. The DSSC with the optimized SAT gradient-ascent photoanode has the maximum short circuit current density(J_(sc)) of 17.7 mA cm^(-2) and PCE of 7.75%, remarkably higher than those of the conventional DSSC by 23.7%and 28.0%, respectively. This significantly enhancement of the performance of the DSSC can be attributed to the excellent light reflection/scattering of SAT, the localized surface plasma resonance(LSPR) effect of AuNPs within the microspheres, and the gradient-ascent architecture of SAT microspheres inside the photoanode. This study demonstrates that the tri-synergies of the scattering of SAT microspheres, the LSPR of AuNPs and the gradient-ascent architecture can effectively improve the PCE of DSSC.
文摘This study aimed to compare gait properties during level walking and during stair ascent and descent with varying loads. Fifteen healthy young men (mean age: 22.1 ± 1.6 years) walked while holding four different loads relative to each subject’s body mass (0, 20, 40 and 60% of body mass: BM) on their backs. Stance time, swing time, and double support times were selected as gait parameters. All parameters showed a maximal value during stair ascent and a minimum value during level walking. Stance and double support times increased significan- tly with each load during level walking and during stair ascent and descent. In conclusion, st- air ascent and descent creates more unstable movement than level walking regardless of the weight of the load. The effect of loads on gait increases with the weight of the load and becomes obvious once the load exceeds 60% of BM.
基金supported by the National Natural Science Foundation of China(Grant Nos.11101200 and 11371185)the Natural Science Foundation of Inner Mongolia Autonomous Region,China(Grant No.2013ZD01)
文摘In this paper, the ascent of 2 × 2 infinite dimensional Hamiltonian operators and a class of 4 × 4 infinite dimensional Hamiltonian operators are studied, and the conditions under which the ascent of 2 × 2 infinite dimensional Hamiltonian operator is 1 and the ascent of a class of 4 × 4 infinite dimensional Hamiltonian operators that arises in study of elasticity is2 are obtained. Concrete examples are given to illustrate the effectiveness of criterions.
基金Supported by the National Natural Science Foundation of China(61262088,61063042)the Natural Science Foundation Project of Xinjiang Uygur Autonomous Region(2011211A011)
文摘We solve two problems about ascent sequences： how to get the ascent sequence of the reflection of A with respect to its antidiagonal for a matrix A ∈ Intn and its ascent sequences, and how to determine the ascent sequence of A＋B for kxk matrices A ∈ Int, and B ∈ Intm. We give the other definition of ascent se- quence and get M-sequence. For the first question, we define M-sequence of A and rewrite the ascent sequences as another form We build the bijection between M-sequences and ascent sequences and prove that our bijection is well-defined. For the second ques- tion, we define an operation on M-sequences. On the basis of the operation and the bijections, we get the ascent sequences of the sum of two matrices.
基金supported by the National Natural Science Foundation of China(Nos.92055211,42249801)the China-ASEAN Maritime Cooperation Fund Project(No.12120100500017001)。
文摘Gas chimneys,salt domes,and faults are vital to the movement of hydrocarbons within geological systems.Accurate identification of these geological features is crucial to modeling hydrocarbon resources.This study explores the processes that have shaped the eastern Persian Gulf,focusing on salt diapir characteristics,origin,and fluid migration.Plate collisions between the Indian,Eurasian,and Arabian Plates have considerably impacted salt tectonics,developing key features such as the Hormuz salt,Qatar-South Fars Arch,and Zagros and Oman orogenic structures.Salt-related features were discerned through two-dimensional seismic data and drilling records,salt movement sequences were reconstructed,and fluid expulsion patterns were delineated using attribute preferences.The results of this study revealed that fractured substrates influenced by regional tectonic forces contribute to the creation of salt diapirs,which serve as conduits for guided fluid transport.Moreover,these results showed that gravity-driven downbuilding mainly controls salt flow,while the circular arrangement of salt structures results from regional stress and interactions between different salt sources.Distinct stress-induced basement incisions compounded by the hindrance of initial salt movement by the Qatar Arch further contribute to the complex salt structure geometry.Crucially,the uplift of the Qatar Arch and stresses from the Oman and Zagros orogenies profoundly affect the salt structure geometry and depositional patterns across diverse regions,resulting in circular salt structures and gas chimneys.This study offers valuable perspectives for oil and gas exploration and provides a comprehensive understanding of the regional dynamics governing salt tectonics and hydrocarbon ascent in the eastern Persian Gulf.
基金Supported in part by National Natural Science Foundation of China(No.62003012)in part by the Young Tulents Support Program funded by Bcihang Univer-sity,China(No.YWF-23-L-702).
文摘In the scenario that a solid-fuel launch vehicle maneuvers in outer space at high angles of attack and sideslip for energy management,Approximate Analytical Solutions(AAS)for the threedimensional(3D)ascent flight states are derived,which are the only solutions capable of considering time-varying Mass Flow Rate(MFR)at present.The uneven MFR makes the thrust vary nonlinearly and thus increases the difficulty of the problem greatly.The AAS are derived based on a 3D Generalized Ascent Dynamics Model(GADM)with a normalized mass as the independent variable.To simplify some highly nonlinear terms in the GADM,several approximate functions are introduced carefully,while the errors of the approximations relative to the original terms are regarded as minor perturbations.Notably,a finite series with positive and negative exponents,called Exponent-Symmetry Series(ESS),is proposed for function approximation to decrease the highest exponent in the AAS so as to reduce computer round-off errors.To calculate the ESS coefficients,a method of seeking the Optimal Interpolation Points(OIP)is proposed using the leastsquares-approximation theory.Due to the artful design of the approximations,the GADM can be decomposed into two analytically solvable subsystems by a perturbation method,and thus the AAS are obtained successfully.Finally,to help implement the AAS,two indirect methods for measuring the remaining mass and predicting the burnout time in flight are put forward using information from accelerometers.Simulation results verify the superiority of the AAS under the condition of time-varying MFR.
文摘The recent approval of pembrolizumab as second-line treatment for any solid tumor with high-level microsatellite instability or mismatch repair deficiency agnostic of tissue and origin1 has shattered a glass ceiling for immune checkpoint inhibitors.No longer bound to a specific cancer diagnosis but rather a biomarker,pembrolizumab has heightened a burgeoning optimism towards the drug class.Yet how these agents should carve out additional
基金supported by a grant from the National Science Foundation of China(No.81301134,81371444)a research program from the logistics department of PLA(No.CLZ15C005)
文摘To evaluate the effect of acute high-altitude exposure on sensory and short-term memory using interactive software,we transported 30 volunteers in a sport utility vehicle to a 4280 m plateau within3 h.We measured their memory performance on the plain（initial arrival）and 3 h after arrival on the plateau using six measures.
基金supported by the National Defense Basic Scientific Research Program(JCKY2021603B030)the National Natural Science Foundation of China(62273118,12150008)the Natural Science Foundation of Heilongjiang Province(LH2022F023).
文摘Dear Editor,This letter proposes a convex optimization-based model predictive control(MPC)autonomous guidance method for the Mars ascent vehicle(MAV).We use the modified chebyshev-picard iteration(MCPI)to solve optimization sub-problems within the MPC framework,eliminating the dynamic constraints in solving the optimal control problem and enhancing the convergence performance of the algorithm.Moreover,this method can repeatedly perform trajectory optimization calculations at a high frequency,achieving timely correction of the optimal control command.Numerical simulations demonstrate that the method can satisfy the requirements of rapid computation and reliability for the MAV system when considering uncertainties and perturbations.
文摘The Brisbane Tropical Cyclone Warning Centre has used two forms of a thermal advection diagnostic to identify relatively large areas of isentropic ascent and descent for many years. When the thermodynamic conditions are favourable the ascent regions are correlated with significant outbreaks of convection that produce heavy rainfall. The diagnostic is based on the relationship between geostrophic winds that turn with height and flow perpendicular to thickness contours. As the relationship is also valid for the more general case of gradient winds, the diagnostic, in theory, should be useful for most heavy-rain-bearing tropical systems. A climatology of rainfall rate with one form of the diagnostic is presented at two Queensland locations(one tropical and one subtropical) that demonstrates a clear relationship between the isentropic ascent wind distribution and heavy to extreme rainfall.The diagnostics applied to numerical weather prediction models are valuable forecast tools as they identify heavy rainfall threat regions within which the extreme rain is likely to fall, whereas the rainfall from the same models is often under predicted or has large location errors. Applied to tropical lows and tropical cyclones the diagnostics have been used successfully to forecast tropical cyclone formation and rapid intensification and decay. Examples of such intensification and decay from around the world are presented, as well as a climatology of the diagnostic applied to intensifying tropical cyclones in the Australian region.
基金was provided by Chinese Universities Scientific Fund(Grant No.2020063).
文摘Purpose Understanding the femur load environment during daily activity is necessary for the understanding of risk of femoral pain,pain related falls,and femoral fractures,which could help the design of osteogenic exercises or the preventa-tive methods for older adults.Methods Using the finite element femur analysis,this study was to estimate the femoral strains at 9 cross-sections along the long axis of femur for stair ascent and descent(n=17;age:50-65 years).Motion analysis and inverse dynamics were com-bined with musculoskeletal modelling and optimization,then were used as input to a 3-D femur model to estimate femoral strains.Strains at the hip contact force peaks were calculated.Results The compressive and tensile strains during stair descent were greater than ascent for all or most cross-sections,especially for the proximal cross-sections of the femur:stair ascent produced−324.0±103.8 to−483.7±191.0μεcompressive strains and descent produced−608.8±288.4 to 1016.0±444.1με;stair ascent produced 336.2±105.4 to 391.8±136.9μεtensile strains and descent produced 546.9±252.8 to 741.7±333.6με.Conclusion Strains represent the material deformation effect on the bone due to the sum of all the bone external loads.Using bone strains could help future studies analyze load conditions in a more comprehensive way for other physical activities,which predicts the risk of stress fractures and tests if alternative methods(gait type change)could reduce stress and strain effectively.
文摘The SCO charts a course for the future at landmark meetings marking its fifth anniversary The Shanghai Cooperation Organization (SCO) Summit on June 15 received extraordinary media coverage in China. Broadcast live on state radio and television and on the Internet, the summit made headlines
