[Objectives] This study was conducted to investigate the mutagenic effects of space radiation mutagenesis on sugarcane hybrid seeds. [Methods] Sugarcane hybrid spikes were subjected to space radiation mutagenesis trea...[Objectives] This study was conducted to investigate the mutagenic effects of space radiation mutagenesis on sugarcane hybrid seeds. [Methods] Sugarcane hybrid spikes were subjected to space radiation mutagenesis treatment to identify the effects on the germination, seedling growth and plant growth and development of sugarcane hybrid seeds. [Results] The space radiation treatment had a great impact on the germination and growth of sugarcane hybrid seeds, especially on the germination of sugarcane seeds. The germination number per gram of seeds increased significantly, and the survival rate of seedlings increased significantly. The effect on the growth status was relatively small. The average number of tillers decreased slightly, the percentage of available stems increased, and the plants became higher, which resulted in a greater effect on sugarcane yield. Sugarcane sucrose was increased. The seed germination and late growth status indicated that space radiation promoted the germination and growth of sugarcane hybrid seeds. [Conclusions] This study provides a basis for the space radiation mutagenesis breeding of sugarcane hybrid seeds and the promotion of sugarcane breeding process.展开更多
The process of a γ-irradiation experiment of fibre optical gyroscope （FOG） control circuit was described, in which it is demonstrated that the FOG control circuit, except for D/A converter, could endure the dose of...The process of a γ-irradiation experiment of fibre optical gyroscope （FOG） control circuit was described, in which it is demonstrated that the FOG control circuit, except for D/A converter, could endure the dose of 10krad with the protection of cabin material. The distortion and drift in D/A converter due to radiation, which affect the performance of FOG seriously, was indicated based on the elemental analysis. Finally, a compensation network based on adaptive neuro-fuzzy inference system is proposed and its function is verified by simulation.展开更多
With the development of China’s crewed space mission,the space radiation risk for astronauts is increasingly prominent.This paper describes a simulation of the radiation doses experienced by a Chinese female voxel ph...With the development of China’s crewed space mission,the space radiation risk for astronauts is increasingly prominent.This paper describes a simulation of the radiation doses experienced by a Chinese female voxel phantom on board the Chinese Space Station(CSS)performed using the Monte Carlo N-Particle(MCNP)software.The absorbed dose,equivalent dose,and effective dose experienced by the voxel phantom and its critical organs are discussed for different levels of shielding of the Tianhe core module.The risk of space-radiation exposure is then assessed by comparing these doses with the current risk limits in China(the skin dose limit for short-term low-earth-orbit missions)and the NASA figures(National Council on Radiation Protection and Measurements Report No.98)for female astronauts.The results obtained can be used to guide and optimize the radiation protection provided for manned space missions.展开更多
There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events （SPE） and Gal...There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events （SPE） and Galactic Cosmic Rays （GCR） in deep space exploration. The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far. The magnetic field expansion caused by plasma can improve its protective efficiency of space particles. One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric. A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency （RF） power supply of 13.56 MHz, which exits from both sides of the magnet and makes the magnetic field expand on one side. The discharging belts phenomenon is similar to the Earth＇s radiation belt, but the mechanism has yet to be understood. A magnetic probe is used to measure the magnetic field expansion distributions, and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.展开更多
A radiation gene box （RGB） onboard the S J-10 satellite is a device carrying mice and drosophila cells to determine the biological effects of space radiation environment. The shielded fluxes of different radioactive...A radiation gene box （RGB） onboard the S J-10 satellite is a device carrying mice and drosophila cells to determine the biological effects of space radiation environment. The shielded fluxes of different radioactive sources were calculated and the linear energy transfers of γ-rays, electrons, protons and α-particles in the tissue were acquired using A-150 tissue-equivalent plastic. Then, a conceptutual model of a space radiation instrument employing three semiconductor sub-detectors for deriving the charged and uncharged radiation environment of the RGB was designed. The energy depositions in the three sub-detectors were classified into 15 channels （bins） in an algorithm derived from the Monte Carlo method. The physical feasibility of the conceptual instrument was also verified by Monte Carlo simulations.展开更多
The ESA and CAS SMILE mission orbit is highly elliptical and will pass through multiple radiation environments.The Soft X-ray Imager(SXI)instrument aboard has a radiation shutter door designed to close when the surrou...The ESA and CAS SMILE mission orbit is highly elliptical and will pass through multiple radiation environments.The Soft X-ray Imager(SXI)instrument aboard has a radiation shutter door designed to close when the surrounding radiation flux is high.The shutter door will close when passing below an altitude threshold to protect against trapped particles in the Earth’s Van Allen Belts.Therefore,two radiation environments can be approximated based on the shutter door position:open and closed.The instrument background for the CCDs(Charge-Coupled Devices)that form the focal plane array of the SXI were evaluated for the two environments.Due to the correlation of the space environment with the solar cycle,the solar minima and maxima,the background was also evaluated at these two extremes.The results demonstrated that the highest instrument background will occur during solar minima due to the main contributing source being Galactic Cosmic Rays(GCRs).It was also found that the open background was highest for solar minima and that the closed background was highest during solar maxima.This is due to the radiation shutter door acting as a scattering centre and the changes in the energy flux distribution of the GCRs between the two solar extremes.展开更多
In order to analyze the effect of wavelength-dependent radiation-induced attenuation （RIA） on the mean trans- mission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes （IFOG...In order to analyze the effect of wavelength-dependent radiation-induced attenuation （RIA） on the mean trans- mission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes （IFOGs）, three types of polarization-maintaining （PM） fibers are tested by using a 60Co γ-radiation source. The observed different mean wave- length shift （MWS） behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible ranges and total dose-dependent near-infrared absorption bands. To evaluate the mean wavelength variation in a fiber coil and the induced scale factor change for space-borne IFOGs under low radiation doses in a space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium （Ge） doped fibers and two germanium-phosphorus （Ge-P） codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmission in fibers will shift to a shorter wavelength in a low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOGs.展开更多
Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper ...Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper studies the low-density parity-check(LDPC) coding scheme for improving the reliability of multi-level-cell(MLC) NAND Flash memory in radiation environments. Firstly, based on existing physical experiment works, we introduce a new error model for heavyion irradiations; secondly, we explore the optimization of writing voltage allocation to maximize the capacity of the storage channel; thirdly, we design the degree distribution of LDPC codes that is specially suitable for the proposed model; finally, we propose a joint detection-decoding scheme based on LDPC codes, which estimates the storage channel state and executes an adaptive log-likelihood ratio(LLR) calculation to achieve better performance. Simulation results show that, compared with the conventional LDPC coding scheme, the proposed scheme may almost double the lifetime of the MLC NAND Flash memory in radiation environments.展开更多
Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft,but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser...Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft,but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser-plasma accelerator, we can reproduce exponential energy particle beams as similar as possible to these in space radiation. We used such an electron beam to study the electron radiation effects on the surface structure and performance of two-dimensional material(Fe PS3).Energetic electron beam led to bulk sample cleavage and damage between areas of uneven thickness. For the Fe PS3sheet sample, electron radiation transformed it from crystalline state to amorphous state, causing the sample surface to rough.The full widths at the half maximum of characteristic Raman peaks became larger, and the intensities of characteristic Raman peaks became weak or even disappeared dramatically under electron radiation. This trend became more obvious for thinner samples, and this phenomenon was attributed to the cleavage of P–P and P–S bonds, destabilizing the bipyramid structure of [P2S6]4-unit. The results are of great significance for testing the maximum allowable radiation dose for the two-dimensional material, implying that Fe PS3cannot withstand such energetic electron radiation without an essential shield.展开更多
Although human hibernation has been introduced as an effective technique in space exploration,there are concerns regarding the intrinsic risks of the approach(i.e.,synthetic torpor)and other factors involved in this p...Although human hibernation has been introduced as an effective technique in space exploration,there are concerns regarding the intrinsic risks of the approach(i.e.,synthetic torpor)and other factors involved in this procedure.Besides concerns about the brain changes and the state of consciousness during hibernation,an"Achilles heel"of the hibernation is the negative impact of torpor on factors such as the number of circulating leukocytes,complement levels,response to lipopolysaccharides,phagocytotic capacity,cytokine production,lymphocyte proliferation,and antibody production.Moreover,increased virulence of bacteria in deep space can significantly increase the risk of infection.The increased infection risk during long-term space missions with the combined effects of radiation and microgravity affect the astronauts’immune system.With these additional immune system stressors,torpor-induced extraimmunosuppression can be potentially life threatening for astronauts.展开更多
Deep dielectric charging/discharging,caused by high energy electrons,is an important consideration in electronic devices used in space environments because it can lead to spacecraft anomalies and failures.The Jovian p...Deep dielectric charging/discharging,caused by high energy electrons,is an important consideration in electronic devices used in space environments because it can lead to spacecraft anomalies and failures.The Jovian planets,including Saturn,Uranus,Neptune and Jupiter’s moons,are believed to have robust electron radiation belts at relativistic energies.In particular,Jupiter is thought to have caused at least 42 internal electrostatic discharge events during the Voyager 1 flyby.With the development of deep space exploration,there is an increased focus on the deep dielectric charging effects in the orbits of Jovian planets.In this paper,GEANT4,a Monte Carlo toolkit,and radiation-induced conductivity(RIC)are used to calculate deep dielectric charging effects for Jovian planets.The results are compared with the criteria for preventing deep dielectric charging effects in Earth orbit.The findings show that effective criteria used in Earth orbit are not always appropriate for preventing deep dielectric charging effects in Jovian orbits.Generally,Io,Europa,Saturn(R_S=6),Uranus(L=4.73)and Ganymede missions should have a thicker shield or higher dielectric conductivity,while Neptune(L=7.4)and Callisto missions can have a thinner shield thickness or a lower dielectric conductivity.Moreover,dielectrics grounded with double metal layers and thinner dielectrics can also decrease the likelihood of discharges.展开更多
Field Programmable Gate Arrays(FPGAs)offer high capability in implementing of complex systems,and currently are an attractive solution for space system electronics.However,FPGAs are susceptible to radiation induced Si...Field Programmable Gate Arrays(FPGAs)offer high capability in implementing of complex systems,and currently are an attractive solution for space system electronics.However,FPGAs are susceptible to radiation induced Single-Event Upsets(SEUs).To insure reliable operation of FPGA based systems in a harsh radiation environment,various SEU mitigation techniques have been provided.In this paper we propose a system based on dynamic partial reconfiguration capability of the modern devices to evaluate the SEU fault effect in FPGA.The proposed approach combines the fault injection controller with the host FPGA,and therefore the hardware complexity is minimized.All of the SEU injection and evaluation requirements are performed by a soft-core which realized inside the host FPGA.Experimental results on some standard benchmark circuits reveal that the proposed system is able to speed up the fault injection campaign 50 times in compared to conventional method.展开更多
The single event effect(SEE) is an important consideration in electronic devices used in space environments because it can lead to spacecraft anomalies and failures. The linear energy transfer(LET) of ions is commonly...The single event effect(SEE) is an important consideration in electronic devices used in space environments because it can lead to spacecraft anomalies and failures. The linear energy transfer(LET) of ions is commonly investigated in studies of SEE. The use of a thin detector is an economical way of directly measuring the LET in space. An LET telescope consists of a thin detector as the front detector(D1), along with a back detector that indicates whether D1 was penetrated. The particle radiation effect monitor(PREM) introduced in this paper is designed to categorize the LET into four bins of 0.2–0.4, 0.4–1.0, 1.0–2.0 and 2.0–20 Me V·cm^2/mg, and one integral bin of LET>20 Me V·cm^2/mg. After calibration with heavy ions and Geant4 analysis, the LET boundaries of the first four bins are determined to be 0.236, 0.479, 1.196, 2.254, and 17.551 Me V·cm^2/mg, whereas that of the integral bin is determined to be LET>14.790 Me V·cm^2/mg. The acceptances are calculated by Geant4 analysis as 0.452, 0.451, 0.476, 0.446, and 1.334, respectively. The LET accuracy is shown to depend on the thickness of D1; as D1 is made thinner, the accuracy of the measured values increases.展开更多
Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Prog...Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Program(CLEP),also known as the Chang’e(CE)Project,has achieved remarkable milestones.It has successfully developed and demonstrated the engineering capability required to reach and return from the lunar surface.Notably,the CE Project has made historic firsts with the landing and on-site exploration of the far side of the Moon,along with the collection of the youngest volcanic samples from the Procellarum KREEP Terrane.These achievements have significantly enhanced our understanding of lunar evolution.Building on this success,China has proposed an ambitious crewed lunar exploration strategy,aiming to return to the Moon for scientific exploration and utilization.This plan encompasses two primary phases:the first crewed lunar landing and exploration,followed by a thousand-kilometer scale scientific expedition to construct a geological cross-section across the lunar surface.Recognizing the limitations of current lunar exploration efforts and China’s engineering and technical capabilities,this paper explores the benefits of crewed lunar exploration while leveraging synergies with robotic exploration.The study refines fundamental lunar scientific questions that could lead to significant breakthroughs,considering the respective engineering and technological requirements.This research lays a crucial foundation for defining the objectives of future lunar exploration,emphasizing the importance of crewed missions and offering insights into potential advancements in lunar science.展开更多
Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freef...Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freefrom curvature singularities and a four-dimensional extension of the Misner space in curved spacetime. The spacetime is of type Ⅱ in the Petrov classification scheme and the matter field pure radiation satisfy the energy condition.展开更多
基金Supported by General Project of Hainan Provincial Natural Science Foundation(No.317257)The Fundamental Research Funds for Central Public Welfare Research Institutes(1630052019005)China Agricultural Research System-Sugar crop(CARS-170716)
文摘[Objectives] This study was conducted to investigate the mutagenic effects of space radiation mutagenesis on sugarcane hybrid seeds. [Methods] Sugarcane hybrid spikes were subjected to space radiation mutagenesis treatment to identify the effects on the germination, seedling growth and plant growth and development of sugarcane hybrid seeds. [Results] The space radiation treatment had a great impact on the germination and growth of sugarcane hybrid seeds, especially on the germination of sugarcane seeds. The germination number per gram of seeds increased significantly, and the survival rate of seedlings increased significantly. The effect on the growth status was relatively small. The average number of tillers decreased slightly, the percentage of available stems increased, and the plants became higher, which resulted in a greater effect on sugarcane yield. Sugarcane sucrose was increased. The seed germination and late growth status indicated that space radiation promoted the germination and growth of sugarcane hybrid seeds. [Conclusions] This study provides a basis for the space radiation mutagenesis breeding of sugarcane hybrid seeds and the promotion of sugarcane breeding process.
文摘The process of a γ-irradiation experiment of fibre optical gyroscope （FOG） control circuit was described, in which it is demonstrated that the FOG control circuit, except for D/A converter, could endure the dose of 10krad with the protection of cabin material. The distortion and drift in D/A converter due to radiation, which affect the performance of FOG seriously, was indicated based on the elemental analysis. Finally, a compensation network based on adaptive neuro-fuzzy inference system is proposed and its function is verified by simulation.
基金Project supported by the Open Project Funds for the Key Laboratory of Space Photoelectric Detection and Perception(Nanjing University of Aeronautics and Astronautics),the Ministry of Industry and Information Technology of China(Grant No.NJ2022025-7)the Fundamental Research Funds for the Central Universities(Grant No.NJ2022025).
文摘With the development of China’s crewed space mission,the space radiation risk for astronauts is increasingly prominent.This paper describes a simulation of the radiation doses experienced by a Chinese female voxel phantom on board the Chinese Space Station(CSS)performed using the Monte Carlo N-Particle(MCNP)software.The absorbed dose,equivalent dose,and effective dose experienced by the voxel phantom and its critical organs are discussed for different levels of shielding of the Tianhe core module.The risk of space-radiation exposure is then assessed by comparing these doses with the current risk limits in China(the skin dose limit for short-term low-earth-orbit missions)and the NASA figures(National Council on Radiation Protection and Measurements Report No.98)for female astronauts.The results obtained can be used to guide and optimize the radiation protection provided for manned space missions.
基金Supported by National Natural Science Foundation of China(10805042,11275176)State Key Laboratory of Space Medicine Fundamentals and Application(SMFA09A10)
文摘There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events （SPE） and Galactic Cosmic Rays （GCR） in deep space exploration. The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far. The magnetic field expansion caused by plasma can improve its protective efficiency of space particles. One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric. A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency （RF） power supply of 13.56 MHz, which exits from both sides of the magnet and makes the magnetic field expand on one side. The discharging belts phenomenon is similar to the Earth＇s radiation belt, but the mechanism has yet to be understood. A magnetic probe is used to measure the magnetic field expansion distributions, and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.
文摘A radiation gene box （RGB） onboard the S J-10 satellite is a device carrying mice and drosophila cells to determine the biological effects of space radiation environment. The shielded fluxes of different radioactive sources were calculated and the linear energy transfers of γ-rays, electrons, protons and α-particles in the tissue were acquired using A-150 tissue-equivalent plastic. Then, a conceptutual model of a space radiation instrument employing three semiconductor sub-detectors for deriving the charged and uncharged radiation environment of the RGB was designed. The energy depositions in the three sub-detectors were classified into 15 channels （bins） in an algorithm derived from the Monte Carlo method. The physical feasibility of the conceptual instrument was also verified by Monte Carlo simulations.
文摘The ESA and CAS SMILE mission orbit is highly elliptical and will pass through multiple radiation environments.The Soft X-ray Imager(SXI)instrument aboard has a radiation shutter door designed to close when the surrounding radiation flux is high.The shutter door will close when passing below an altitude threshold to protect against trapped particles in the Earth’s Van Allen Belts.Therefore,two radiation environments can be approximated based on the shutter door position:open and closed.The instrument background for the CCDs(Charge-Coupled Devices)that form the focal plane array of the SXI were evaluated for the two environments.Due to the correlation of the space environment with the solar cycle,the solar minima and maxima,the background was also evaluated at these two extremes.The results demonstrated that the highest instrument background will occur during solar minima due to the main contributing source being Galactic Cosmic Rays(GCRs).It was also found that the open background was highest for solar minima and that the closed background was highest during solar maxima.This is due to the radiation shutter door acting as a scattering centre and the changes in the energy flux distribution of the GCRs between the two solar extremes.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61007040)
文摘In order to analyze the effect of wavelength-dependent radiation-induced attenuation （RIA） on the mean trans- mission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes （IFOGs）, three types of polarization-maintaining （PM） fibers are tested by using a 60Co γ-radiation source. The observed different mean wave- length shift （MWS） behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible ranges and total dose-dependent near-infrared absorption bands. To evaluate the mean wavelength variation in a fiber coil and the induced scale factor change for space-borne IFOGs under low radiation doses in a space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium （Ge） doped fibers and two germanium-phosphorus （Ge-P） codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmission in fibers will shift to a shorter wavelength in a low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOGs.
基金supported by the National Basic Research Project of China(973)(2013CB329006)National Natural Science Foundation of China(NSFC,91538203)the new strategic industries development projects of Shenzhen City(JCYJ20150403155812833)
文摘Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper studies the low-density parity-check(LDPC) coding scheme for improving the reliability of multi-level-cell(MLC) NAND Flash memory in radiation environments. Firstly, based on existing physical experiment works, we introduce a new error model for heavyion irradiations; secondly, we explore the optimization of writing voltage allocation to maximize the capacity of the storage channel; thirdly, we design the degree distribution of LDPC codes that is specially suitable for the proposed model; finally, we propose a joint detection-decoding scheme based on LDPC codes, which estimates the storage channel state and executes an adaptive log-likelihood ratio(LLR) calculation to achieve better performance. Simulation results show that, compared with the conventional LDPC coding scheme, the proposed scheme may almost double the lifetime of the MLC NAND Flash memory in radiation environments.
基金Project supported by the National Natural Science Foundation of China(Grant No.11975308)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA25050200)Science Challenge Project(Grant No.TZ2018001)。
文摘Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft,but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser-plasma accelerator, we can reproduce exponential energy particle beams as similar as possible to these in space radiation. We used such an electron beam to study the electron radiation effects on the surface structure and performance of two-dimensional material(Fe PS3).Energetic electron beam led to bulk sample cleavage and damage between areas of uneven thickness. For the Fe PS3sheet sample, electron radiation transformed it from crystalline state to amorphous state, causing the sample surface to rough.The full widths at the half maximum of characteristic Raman peaks became larger, and the intensities of characteristic Raman peaks became weak or even disappeared dramatically under electron radiation. This trend became more obvious for thinner samples, and this phenomenon was attributed to the cleavage of P–P and P–S bonds, destabilizing the bipyramid structure of [P2S6]4-unit. The results are of great significance for testing the maximum allowable radiation dose for the two-dimensional material, implying that Fe PS3cannot withstand such energetic electron radiation without an essential shield.
文摘Although human hibernation has been introduced as an effective technique in space exploration,there are concerns regarding the intrinsic risks of the approach(i.e.,synthetic torpor)and other factors involved in this procedure.Besides concerns about the brain changes and the state of consciousness during hibernation,an"Achilles heel"of the hibernation is the negative impact of torpor on factors such as the number of circulating leukocytes,complement levels,response to lipopolysaccharides,phagocytotic capacity,cytokine production,lymphocyte proliferation,and antibody production.Moreover,increased virulence of bacteria in deep space can significantly increase the risk of infection.The increased infection risk during long-term space missions with the combined effects of radiation and microgravity affect the astronauts’immune system.With these additional immune system stressors,torpor-induced extraimmunosuppression can be potentially life threatening for astronauts.
基金supported by Beijing Municipal Natural Science Foundation-Quantitative Research on Mitigating Deep Dielectric Charging Effects in Jupiter orbits(No.3184048)National Key Scientific Instrument and Equipment Development Projects,China(No.2012YQ03014207)。
文摘Deep dielectric charging/discharging,caused by high energy electrons,is an important consideration in electronic devices used in space environments because it can lead to spacecraft anomalies and failures.The Jovian planets,including Saturn,Uranus,Neptune and Jupiter’s moons,are believed to have robust electron radiation belts at relativistic energies.In particular,Jupiter is thought to have caused at least 42 internal electrostatic discharge events during the Voyager 1 flyby.With the development of deep space exploration,there is an increased focus on the deep dielectric charging effects in the orbits of Jovian planets.In this paper,GEANT4,a Monte Carlo toolkit,and radiation-induced conductivity(RIC)are used to calculate deep dielectric charging effects for Jovian planets.The results are compared with the criteria for preventing deep dielectric charging effects in Earth orbit.The findings show that effective criteria used in Earth orbit are not always appropriate for preventing deep dielectric charging effects in Jovian orbits.Generally,Io,Europa,Saturn(R_S=6),Uranus(L=4.73)and Ganymede missions should have a thicker shield or higher dielectric conductivity,while Neptune(L=7.4)and Callisto missions can have a thinner shield thickness or a lower dielectric conductivity.Moreover,dielectrics grounded with double metal layers and thinner dielectrics can also decrease the likelihood of discharges.
文摘Field Programmable Gate Arrays(FPGAs)offer high capability in implementing of complex systems,and currently are an attractive solution for space system electronics.However,FPGAs are susceptible to radiation induced Single-Event Upsets(SEUs).To insure reliable operation of FPGA based systems in a harsh radiation environment,various SEU mitigation techniques have been provided.In this paper we propose a system based on dynamic partial reconfiguration capability of the modern devices to evaluate the SEU fault effect in FPGA.The proposed approach combines the fault injection controller with the host FPGA,and therefore the hardware complexity is minimized.All of the SEU injection and evaluation requirements are performed by a soft-core which realized inside the host FPGA.Experimental results on some standard benchmark circuits reveal that the proposed system is able to speed up the fault injection campaign 50 times in compared to conventional method.
基金supported by the National Natural Science Foundation of China(Grant No.41374181)the National Key Scientific Instrument and Equipment Development ProjectsChina(Grant No.2012YQ03014207)
文摘The single event effect(SEE) is an important consideration in electronic devices used in space environments because it can lead to spacecraft anomalies and failures. The linear energy transfer(LET) of ions is commonly investigated in studies of SEE. The use of a thin detector is an economical way of directly measuring the LET in space. An LET telescope consists of a thin detector as the front detector(D1), along with a back detector that indicates whether D1 was penetrated. The particle radiation effect monitor(PREM) introduced in this paper is designed to categorize the LET into four bins of 0.2–0.4, 0.4–1.0, 1.0–2.0 and 2.0–20 Me V·cm^2/mg, and one integral bin of LET>20 Me V·cm^2/mg. After calibration with heavy ions and Geant4 analysis, the LET boundaries of the first four bins are determined to be 0.236, 0.479, 1.196, 2.254, and 17.551 Me V·cm^2/mg, whereas that of the integral bin is determined to be LET>14.790 Me V·cm^2/mg. The acceptances are calculated by Geant4 analysis as 0.452, 0.451, 0.476, 0.446, and 1.334, respectively. The LET accuracy is shown to depend on the thickness of D1; as D1 is made thinner, the accuracy of the measured values increases.
基金supported by the National Natural Science Foundation of China(L2224032)the Research Project on the Discipline Development Strategy of Academic Divisions of the Chinese Academy of Sciences(XK2022DXC004).
文摘Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Program(CLEP),also known as the Chang’e(CE)Project,has achieved remarkable milestones.It has successfully developed and demonstrated the engineering capability required to reach and return from the lunar surface.Notably,the CE Project has made historic firsts with the landing and on-site exploration of the far side of the Moon,along with the collection of the youngest volcanic samples from the Procellarum KREEP Terrane.These achievements have significantly enhanced our understanding of lunar evolution.Building on this success,China has proposed an ambitious crewed lunar exploration strategy,aiming to return to the Moon for scientific exploration and utilization.This plan encompasses two primary phases:the first crewed lunar landing and exploration,followed by a thousand-kilometer scale scientific expedition to construct a geological cross-section across the lunar surface.Recognizing the limitations of current lunar exploration efforts and China’s engineering and technical capabilities,this paper explores the benefits of crewed lunar exploration while leveraging synergies with robotic exploration.The study refines fundamental lunar scientific questions that could lead to significant breakthroughs,considering the respective engineering and technological requirements.This research lays a crucial foundation for defining the objectives of future lunar exploration,emphasizing the importance of crewed missions and offering insights into potential advancements in lunar science.
文摘Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freefrom curvature singularities and a four-dimensional extension of the Misner space in curved spacetime. The spacetime is of type Ⅱ in the Petrov classification scheme and the matter field pure radiation satisfy the energy condition.
