In higher dimensional spaces Rn(n>3) the usual curl does not have the properties as in R3. In this paper, we established the natural concept of curl in R7 via octonion O. We prove that there exists the curl in Rn i...In higher dimensional spaces Rn(n>3) the usual curl does not have the properties as in R3. In this paper, we established the natural concept of curl in R7 via octonion O. We prove that there exists the curl in Rn if and only if n=3, 7. Some applications are presented, such as the new phenmenon of the differential forms in R7 whcih is different from the ordinary de Rham cohomology and Hodge theory, grad-curl-div type Dirac oper ator in R6, seven dimensional Maxwell equations and Navier-Stokes equations.Supported by the National Natural Science Foundation Of展开更多
Owing to the increasing demand for tribological brakes for space applications, the development of novel materials and advanced technologies is necessary. This paper presents the design, characterization, and realizati...Owing to the increasing demand for tribological brakes for space applications, the development of novel materials and advanced technologies is necessary. This paper presents the design, characterization, and realization of powder metallurgy processed metal-matrix friction materials intended for the above-mentioned tribological brakes. Selecting appropriate ingredients, which provides an effective way to tailor the properties of the friction material, is evolving as a strategy to meet the design requirements. The tribological behaviors of the friction material are experimentally investigated under different conditions, and special attention is focused on the vacuum tribology. Examinations and analyses of the friction surface and subsurface corroborate the wear mechanism. In addition, the erosion resistances of the friction material are evaluated by exposure tests of ultraviolet irradiation and atomic oxygen. Finally, present and potential space applications of the friction material are also introduced based on experimental studies.展开更多
A Chinese delegation of 24 persons headed by Mr. Luan Enjie, Vice Administrator of China National Space Administration (CNSA) attended the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology...A Chinese delegation of 24 persons headed by Mr. Luan Enjie, Vice Administrator of China National Space Administration (CNSA) attended the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology and Applications held at Islamabad, the Capital of Pakistan from April 22 to 26, 1995. Following the First AsiaPacific Workshop held in Beijing in December, 1992, and the First Asia-Pacific Conference on Multilateral Cooperation in展开更多
Since the Asia Pacific Workshop on Multilateral Cooperation in Space Technology and Applications was held in Beijing in December, 1992, the preparatory committee for Asia-Pacific Space Cooperation Mechanism and the Li...Since the Asia Pacific Workshop on Multilateral Cooperation in Space Technology and Applications was held in Beijing in December, 1992, the preparatory committee for Asia-Pacific Space Cooperation Mechanism and the Liaison Committee for AP-MC-STA have done many fruitful works. Thanks to the First Asia Pacific Conference on Multilateral Cooperation in Space Tech-展开更多
Throughout this paper,let(Ω,ι,μ)be a probability space,D the collection of allleft-continuous distribution functions,and D^+={F(0)=0|F∈D},and L(Ω)the collec-tion of all random variables which is a.s.finite on Ω,...Throughout this paper,let(Ω,ι,μ)be a probability space,D the collection of allleft-continuous distribution functions,and D^+={F(0)=0|F∈D},and L(Ω)the collec-tion of all random variables which is a.s.finite on Ω,and L^+={ξ≥0 a.s.|ξ∈L(Ω)}.For random metric (normed) spaces,see [1]or[2].Theorem 1 Let(M,d)be a complete metric space f:M→M,a contract mappingwith contract coefficient α∈[0,1),L(Ω,m)the collection of all M-valued random vari-展开更多
While increasing contact between peoples and cultures,globalization does not weaken the diversity of world's civilizations.Soft power can serve as a lubricant to prevent the clash of civilizations and enhance dial...While increasing contact between peoples and cultures,globalization does not weaken the diversity of world's civilizations.Soft power can serve as a lubricant to prevent the clash of civilizations and enhance dialogues between civilizations.The article summarizes the three components of China's soft power:cultural promoting,foreign assistance and the thought of"a harmonious world."Taking Uzbekistan as an example,the author also illustrates the path of the Islamic nations to implement"soft power"strategy.展开更多
More space truss construction has been planned to develop and utilize space resources.These trusses are designed in the way of large-scale,complex,modular,and on-orbit assembly.To meet the upcoming challenge of large-...More space truss construction has been planned to develop and utilize space resources.These trusses are designed in the way of large-scale,complex,modular,and on-orbit assembly.To meet the upcoming challenge of large-scale space infrastructure construction,it is necessary to study space truss automation design and robotic construction.This paper proposes an ordinal finite screw adjacency matrix model(OFSAMM),focusing on the relationship between assembly motions,to express and compute a space truss structure.In this model,a space truss is abstracted as a set of ordered assembly motions,each of which is recorded as a finite screw as the basic element of the truss and its assembly.The operation of truss transformation is also derived under this model.Therefore,the truss configuration,the assembly sequence,the truss sub-assembly,the truss components,and the on-orbit assembly task can be expressed and calculated in a unified model,which is calculated and stores the truss topology and assembly with the minimum storage cost.At the end of this paper,we introduce how to synthesize and optimize space truss design through two cases.The study will help to improve design efficiency.Furthermore,it provides a theoretical basis for the automatic construction of space truss structures,especially in the next stage.展开更多
To meet more and more high-quality and low-cost needs in aerospace fields nowadays,the large-scale application of COTS components needs standards guidance.This paper discusses the construction of the technical standar...To meet more and more high-quality and low-cost needs in aerospace fields nowadays,the large-scale application of COTS components needs standards guidance.This paper discusses the construction of the technical standards system on assurance of COTS components for space application.Focusing on the core areas of aerospace technology,it gives the standards system framework and key standards such as selection criteria,quality assurance standards,storage and protection standards,and use guides.展开更多
§ 0. IntroductionThe purpose of this paper is to investigate the theory of probabilistic metric spaces (PM-spaces) and its applications. In § 1 we introduce a kind of Menger PM-spaces. By virtue of their bas...§ 0. IntroductionThe purpose of this paper is to investigate the theory of probabilistic metric spaces (PM-spaces) and its applications. In § 1 we introduce a kind of Menger PM-spaces. By virtue of their basic properties and the Menger-Hausdorff metric defined for this kind of spaces, in § 2 we shall give some fixed point theorems for multi-valued mappings on PM-spaces. In addition, in § 3 we shall give some fixed point theorems for one-valued mappings on PM-space, which generalize and展开更多
The plume divergence angle is an important reference index for evaluating the thrust efficiency and propellant utilization of space propulsion systems.However,the characteristics of the dynamic variation of plume dive...The plume divergence angle is an important reference index for evaluating the thrust efficiency and propellant utilization of space propulsion systems.However,the characteristics of the dynamic variation of plume divergence angle over time cannot be measured using current methods.This paper utilizes high-speed photography and image processing methods to develop a strategy that can give a quick,non-destructive and real-time detection of the divergence angle.Effectiveness of the strategy is verified,and the characteristics of plume divergence angles of different lasercontrolled solid propellants were further analyzed and fitted.The experimental results indicate that graphene could effectively reduce the divergence angle,while oxide-doped samples had larger divergence angles than alloy-doped and carbon-doped samples.展开更多
As a key technology for space-based Earth observation and astronomical exploration,cooled mid-wavelength and long-wavelength Infrared(IR)detection is widely used in national defense,astronomy exploration,medical imagi...As a key technology for space-based Earth observation and astronomical exploration,cooled mid-wavelength and long-wavelength Infrared(IR)detection is widely used in national defense,astronomy exploration,medical imaging,environmental monitoring,agricultural and other areas.The performances of IR detectors,including cut-off wavelength,detectivity,sensitivity and temperature resolution,plays a significant role in efficiently observing and tracking the low-temperature far-distance moving targets.Achieving optimal detection performance requires the IR detectors to operate at cryogenic temperatures.The future development of space-based applications relies heavily on the mid-wavelength and long-wavelength IR detection technologies,which should be enabled by the long-life cryogenic refrigeration and high-efficiency energy transportation system operating below 40 K,to support the Earth observation and astronomical detection.However,the efficiency degradation caused by the super low temperature brings tremendous challenges to the life time of cryogenic refrigeration and energy transportation systems.This paper evaluates the influence of cryogenic temperature on the infrared detector performances,reviews the features,development and space applications of cryogenic cooling technologies,as well as the cryogenic energy transportation approaches.Additionally,it analyzes the future development trends and challenges in supporting the space-based IR detection.展开更多
Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications.Hereby,we report a comparative study of the advanced protection of silver mirror stacks for space te...Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications.Hereby,we report a comparative study of the advanced protection of silver mirror stacks for space telescopes provided by SiO_(2)and Al_(2)O_(3)coatings in conditions of accelerated aging by sulfida-tion.The model silver stack samples were deposited by cathodic magnetron sputtering on a reference silica substrate for optical applications and a surface-pretreated SiC substrate.Accelerated aging was per-formed in dry and more severe wet conditions.Optical micrographic observations,surface and interface analysis by Time-of Flight Secondary Ion Mass Spectrometry(ToF-SIMS)and reflectivity measurements were combined to comparatively study the effects of degradation.The results show a lower kinetics of degradation by accelerated aging of the stacks protected by the alumina coating in comparable test conditions.展开更多
A hertz-linewidth ultra-stable laser(USL), which will be used to detect the clock transition line, in a strontium optical clock will be launched into the China Space Station(CSS) in late 2022. As the core of the USL, ...A hertz-linewidth ultra-stable laser(USL), which will be used to detect the clock transition line, in a strontium optical clock will be launched into the China Space Station(CSS) in late 2022. As the core of the USL, an interference-filter-based externalcavity diode laser(IF-ECDL) was developed. The IF-ECDL has a compact, stable, and environmentally insensitive design.Performances of the IF-ECDL are presented. The developed IF-ECDL can pass the aerospace environmental tests, indicating that the IF-ECDL can be suitable for space missions in the CSS.展开更多
After the satellite is launched with the carrier rocket,it is necessary to separate the satellite from the rocket at an appropriate time to ensure that the satellite enters the intended orbit.In this process,it is vit...After the satellite is launched with the carrier rocket,it is necessary to separate the satellite from the rocket at an appropriate time to ensure that the satellite enters the intended orbit.In this process,it is vital to ensure a reliable connection and accurate separation.With the increasing use of microsatellite in orbit,the contradiction between the shock of separation and the requirement of the platform’s dynamic environment is becoming increasingly prominent.Therefore,the traditional pyrotechnic separation device can no longer meet the requirements.This paper presents a reusable non-explosive release actuator using shape memory alloy(SMA)wire for high load and low shock.The system is based on the Fast Acting Shock-less Separation Nut(FASSN)technology.Using the shape memory effect of SMA,a biased SMA wire trigger has been developed,which is used as the driver source of the actuator.At the moment of receiving the electrical signal,the SMA wire generates stress and deformation.The trigger set free the constraints on the mechanical components,and the target is released.Experimental results indicate that the trigger device can unlock successfully and well meet the technical objectives.展开更多
A two-stage gas-coupled Stirling/pulse tube refrigerator(SPR),whose first and second stages respectively involve Stirling and pulse tube refrigeration cycles,is a very promising spaceborne refrigerator.The SPR has man...A two-stage gas-coupled Stirling/pulse tube refrigerator(SPR),whose first and second stages respectively involve Stirling and pulse tube refrigeration cycles,is a very promising spaceborne refrigerator.The SPR has many advantages,such as a compact structure,high reliability,and high performance,and is expected to become an essential refrigerator for space applications.In research regarding gas-coupled regenerative refrigerator,the energy flow distribution between the two stages,and optimal phase difference between the pressure wave and volume flow,are two critical parameters that could widely influence refrigerator performance.The effects of displacer displacement on the pressure wave,phase difference,acoustic power distribution,and inter-stage cooling capacity shift of the SPR have been investigated experimentally.Notably,to obtain the maximum first-stage cooling capacity,an inflection point in displacement exists.When the displacer displacement is larger than the inflection point,the cooling capacity could be distributed between the first and second stages.In the present study,an SPR was designed and manufactured to work between the liquid hydrogen and liquid oxygen temperatures,which can be used to cool small-scale zero boil-off systems and space detectors.Under appropriate displacer displacement,the SPR can reach a no-load cooling temperature of 15.4 K and obtain 2.6 W cooling capacity at 70 K plus 0.1 W cooling capacity at 20 K with 160 W compressor input electric power.展开更多
文摘In higher dimensional spaces Rn(n>3) the usual curl does not have the properties as in R3. In this paper, we established the natural concept of curl in R7 via octonion O. We prove that there exists the curl in Rn if and only if n=3, 7. Some applications are presented, such as the new phenmenon of the differential forms in R7 whcih is different from the ordinary de Rham cohomology and Hodge theory, grad-curl-div type Dirac oper ator in R6, seven dimensional Maxwell equations and Navier-Stokes equations.Supported by the National Natural Science Foundation Of
基金the National Natural Science Foundation of China(Nos.51175516 and 51475476)the Fundamental Research Funds for the Central Universities of Central South University(No.2014 zzts023)Shanghai Key Laboratory of Spacecraft Mechanism(No.QT2010-081)of China for their financial supports
文摘Owing to the increasing demand for tribological brakes for space applications, the development of novel materials and advanced technologies is necessary. This paper presents the design, characterization, and realization of powder metallurgy processed metal-matrix friction materials intended for the above-mentioned tribological brakes. Selecting appropriate ingredients, which provides an effective way to tailor the properties of the friction material, is evolving as a strategy to meet the design requirements. The tribological behaviors of the friction material are experimentally investigated under different conditions, and special attention is focused on the vacuum tribology. Examinations and analyses of the friction surface and subsurface corroborate the wear mechanism. In addition, the erosion resistances of the friction material are evaluated by exposure tests of ultraviolet irradiation and atomic oxygen. Finally, present and potential space applications of the friction material are also introduced based on experimental studies.
文摘A Chinese delegation of 24 persons headed by Mr. Luan Enjie, Vice Administrator of China National Space Administration (CNSA) attended the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology and Applications held at Islamabad, the Capital of Pakistan from April 22 to 26, 1995. Following the First AsiaPacific Workshop held in Beijing in December, 1992, and the First Asia-Pacific Conference on Multilateral Cooperation in
文摘Since the Asia Pacific Workshop on Multilateral Cooperation in Space Technology and Applications was held in Beijing in December, 1992, the preparatory committee for Asia-Pacific Space Cooperation Mechanism and the Liaison Committee for AP-MC-STA have done many fruitful works. Thanks to the First Asia Pacific Conference on Multilateral Cooperation in Space Tech-
文摘Throughout this paper,let(Ω,ι,μ)be a probability space,D the collection of allleft-continuous distribution functions,and D^+={F(0)=0|F∈D},and L(Ω)the collec-tion of all random variables which is a.s.finite on Ω,and L^+={ξ≥0 a.s.|ξ∈L(Ω)}.For random metric (normed) spaces,see [1]or[2].Theorem 1 Let(M,d)be a complete metric space f:M→M,a contract mappingwith contract coefficient α∈[0,1),L(Ω,m)the collection of all M-valued random vari-
文摘While increasing contact between peoples and cultures,globalization does not weaken the diversity of world's civilizations.Soft power can serve as a lubricant to prevent the clash of civilizations and enhance dialogues between civilizations.The article summarizes the three components of China's soft power:cultural promoting,foreign assistance and the thought of"a harmonious world."Taking Uzbekistan as an example,the author also illustrates the path of the Islamic nations to implement"soft power"strategy.
基金financial support under the Manned Aerospace Research Project(Grant No.040102)。
文摘More space truss construction has been planned to develop and utilize space resources.These trusses are designed in the way of large-scale,complex,modular,and on-orbit assembly.To meet the upcoming challenge of large-scale space infrastructure construction,it is necessary to study space truss automation design and robotic construction.This paper proposes an ordinal finite screw adjacency matrix model(OFSAMM),focusing on the relationship between assembly motions,to express and compute a space truss structure.In this model,a space truss is abstracted as a set of ordered assembly motions,each of which is recorded as a finite screw as the basic element of the truss and its assembly.The operation of truss transformation is also derived under this model.Therefore,the truss configuration,the assembly sequence,the truss sub-assembly,the truss components,and the on-orbit assembly task can be expressed and calculated in a unified model,which is calculated and stores the truss topology and assembly with the minimum storage cost.At the end of this paper,we introduce how to synthesize and optimize space truss design through two cases.The study will help to improve design efficiency.Furthermore,it provides a theoretical basis for the automatic construction of space truss structures,especially in the next stage.
文摘To meet more and more high-quality and low-cost needs in aerospace fields nowadays,the large-scale application of COTS components needs standards guidance.This paper discusses the construction of the technical standards system on assurance of COTS components for space application.Focusing on the core areas of aerospace technology,it gives the standards system framework and key standards such as selection criteria,quality assurance standards,storage and protection standards,and use guides.
基金Supported by the Science Fund of Chinese Academy of Sciencas.
文摘§ 0. IntroductionThe purpose of this paper is to investigate the theory of probabilistic metric spaces (PM-spaces) and its applications. In § 1 we introduce a kind of Menger PM-spaces. By virtue of their basic properties and the Menger-Hausdorff metric defined for this kind of spaces, in § 2 we shall give some fixed point theorems for multi-valued mappings on PM-spaces. In addition, in § 3 we shall give some fixed point theorems for one-valued mappings on PM-space, which generalize and
基金This study was co-supported by the Innovative Research Groups of the National Natural Science Foundation of China(No.T2221002).
文摘The plume divergence angle is an important reference index for evaluating the thrust efficiency and propellant utilization of space propulsion systems.However,the characteristics of the dynamic variation of plume divergence angle over time cannot be measured using current methods.This paper utilizes high-speed photography and image processing methods to develop a strategy that can give a quick,non-destructive and real-time detection of the divergence angle.Effectiveness of the strategy is verified,and the characteristics of plume divergence angles of different lasercontrolled solid propellants were further analyzed and fitted.The experimental results indicate that graphene could effectively reduce the divergence angle,while oxide-doped samples had larger divergence angles than alloy-doped and carbon-doped samples.
基金the support from the National Basic Research Program of China(No.613322)the Beijing Nova Program,China(No.Z200002121078)+1 种基金the National Natural Science Foundation of China(No.52202506)the Chinese Government Scholarship(CN)(No.201904980001)。
文摘As a key technology for space-based Earth observation and astronomical exploration,cooled mid-wavelength and long-wavelength Infrared(IR)detection is widely used in national defense,astronomy exploration,medical imaging,environmental monitoring,agricultural and other areas.The performances of IR detectors,including cut-off wavelength,detectivity,sensitivity and temperature resolution,plays a significant role in efficiently observing and tracking the low-temperature far-distance moving targets.Achieving optimal detection performance requires the IR detectors to operate at cryogenic temperatures.The future development of space-based applications relies heavily on the mid-wavelength and long-wavelength IR detection technologies,which should be enabled by the long-life cryogenic refrigeration and high-efficiency energy transportation system operating below 40 K,to support the Earth observation and astronomical detection.However,the efficiency degradation caused by the super low temperature brings tremendous challenges to the life time of cryogenic refrigeration and energy transportation systems.This paper evaluates the influence of cryogenic temperature on the infrared detector performances,reviews the features,development and space applications of cryogenic cooling technologies,as well as the cryogenic energy transportation approaches.Additionally,it analyzes the future development trends and challenges in supporting the space-based IR detection.
文摘Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications.Hereby,we report a comparative study of the advanced protection of silver mirror stacks for space telescopes provided by SiO_(2)and Al_(2)O_(3)coatings in conditions of accelerated aging by sulfida-tion.The model silver stack samples were deposited by cathodic magnetron sputtering on a reference silica substrate for optical applications and a surface-pretreated SiC substrate.Accelerated aging was per-formed in dry and more severe wet conditions.Optical micrographic observations,surface and interface analysis by Time-of Flight Secondary Ion Mass Spectrometry(ToF-SIMS)and reflectivity measurements were combined to comparatively study the effects of degradation.The results show a lower kinetics of degradation by accelerated aging of the stacks protected by the alumina coating in comparable test conditions.
基金This work was supported by the National Key R&D Program of China(No.2020YFC2201300)the National Natural Science Foundation of China(No.11903041)。
文摘A hertz-linewidth ultra-stable laser(USL), which will be used to detect the clock transition line, in a strontium optical clock will be launched into the China Space Station(CSS) in late 2022. As the core of the USL, an interference-filter-based externalcavity diode laser(IF-ECDL) was developed. The IF-ECDL has a compact, stable, and environmentally insensitive design.Performances of the IF-ECDL are presented. The developed IF-ECDL can pass the aerospace environmental tests, indicating that the IF-ECDL can be suitable for space missions in the CSS.
文摘After the satellite is launched with the carrier rocket,it is necessary to separate the satellite from the rocket at an appropriate time to ensure that the satellite enters the intended orbit.In this process,it is vital to ensure a reliable connection and accurate separation.With the increasing use of microsatellite in orbit,the contradiction between the shock of separation and the requirement of the platform’s dynamic environment is becoming increasingly prominent.Therefore,the traditional pyrotechnic separation device can no longer meet the requirements.This paper presents a reusable non-explosive release actuator using shape memory alloy(SMA)wire for high load and low shock.The system is based on the Fast Acting Shock-less Separation Nut(FASSN)technology.Using the shape memory effect of SMA,a biased SMA wire trigger has been developed,which is used as the driver source of the actuator.At the moment of receiving the electrical signal,the SMA wire generates stress and deformation.The trigger set free the constraints on the mechanical components,and the target is released.Experimental results indicate that the trigger device can unlock successfully and well meet the technical objectives.
基金supported by the Hundred Talents Program of the Chinese Academy of Sciences,the National Natural Science Foundation of China(Grant No.51806231)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB35000000,XDB35040102)。
文摘A two-stage gas-coupled Stirling/pulse tube refrigerator(SPR),whose first and second stages respectively involve Stirling and pulse tube refrigeration cycles,is a very promising spaceborne refrigerator.The SPR has many advantages,such as a compact structure,high reliability,and high performance,and is expected to become an essential refrigerator for space applications.In research regarding gas-coupled regenerative refrigerator,the energy flow distribution between the two stages,and optimal phase difference between the pressure wave and volume flow,are two critical parameters that could widely influence refrigerator performance.The effects of displacer displacement on the pressure wave,phase difference,acoustic power distribution,and inter-stage cooling capacity shift of the SPR have been investigated experimentally.Notably,to obtain the maximum first-stage cooling capacity,an inflection point in displacement exists.When the displacer displacement is larger than the inflection point,the cooling capacity could be distributed between the first and second stages.In the present study,an SPR was designed and manufactured to work between the liquid hydrogen and liquid oxygen temperatures,which can be used to cool small-scale zero boil-off systems and space detectors.Under appropriate displacer displacement,the SPR can reach a no-load cooling temperature of 15.4 K and obtain 2.6 W cooling capacity at 70 K plus 0.1 W cooling capacity at 20 K with 160 W compressor input electric power.
