Energy conversion materials for the space solar power station

Since it was first proposed,the space solar power station(SSPS)has attracted great attention all over the world;it is a huge space system and provides energy for Earth.Although several schemes and abundant studies on the SSPS have been proposed and conducted,it is still not realized.The reason why SSPS is still an idea is not only because it is a giant and complex project,but also due to the requirement for various excellent space materials.Among the diverse required materials,we believe energy materials are the most important.Herein,we review the space energy conversion materials for the SSPS.

A Green Paradigm for Internet of Things: Ambient Backscatter Communications

Internet of Things (IoT) has attracted extensive interest from both academia and industries, and is recognized as an ultimate infrastructure to connect everything at anytime and anywhere. The implementation of IoT generally faces the challenges from energy constraint and implementation cost. In this paper, we will introduce a new green communication paradigm, the ambient backscatter (AmBC), that could utilize the environmental wireless signals for both powering a tiny-cost device and backscattering the information symbols. Specifically, we will present the basic principles of AmBC, analyze its features and advantages, suggest its open problems, and predict its potential applications for our future IoT.

Reliability Evaluation of All-User Terminals in LEO Satellite Communication Network Based on Modular Reduction

LEO satellite communication network has a large number of satellites distributed in low orbits,which leads to multiple coverage of many areas on the ground.It is hard work to describe and evaluate the reliability of LEO satellite communication network.To solve this problem,the reliability of all-user terminals in LEO satellite communication network is defined,and the corresponding reliability evaluation method is proposed in the paper.Due to the large scale of the interstellar network,a modular reduction algorithm using the modular network instead of the original network for state decomposition is proposed in this paper.Case study shows that the calculation time of the proposed method is equivalent to 6.28%of the original state space decomposition algorithm.On this basis,the reliability of LEO satellite communication network is further analyzed.It is found that the reliability of LEO satellite network was more sensitive to the reliability of Inter-Satellite link and the satisfaction of global coverage in the early stage,and it is more sensitive to the reliability of the satellite in the later stage.The satellite-ground link has a relatively constant impact on of LEO satellite network.

PS-G-GERT Effectiveness Evaluation Model of Link-Based GEO Satellite Communication Constellation under Poor Information Background

The effectiveness evaluation of GEO satellite communication constellation not only characterizes the communication capability of the constellation but also provides a basis for optimizing the constellation structure.Whether due to information poverty or the complexity of the system,the impact of uncertain information on the effectiveness evaluation needs to be considered to ensure the accuracy of the evaluation results.To address this issue,this paper develops a model for evaluating the GEO satellite communication constellation’s effectiveness in the context of poor information.Firstly,it analyses the GEO satellite communication constellation plus system based on communication links with an in-depth analysis of the constellation structure.Secondly,an equivalent transfer function algorithm based on the characteristic function and transfer probability is proposed with the help of graphical evaluation and review technique.Then,by analyzing the communication link importance connotation,the algorithm formula of communication link effectiveness and its importance is derived,and the constellation effectiveness and variance are found.Finally,the model constructed in this paper is used to evaluate the effectiveness of a GEO satellite communication constellation,further verifying the accuracy and validity of the model.Through comparative analysis,it is shown that the model can not only solving the effectiveness of the constellation but also analyzing the variation of its effectiveness.It lays a theoretical foundation for the analysis and optimization of the GEO satellite communication constellation effectiveness.

3D printed hydrogel for soft thermo-responsive smart window

Smart windows with tunable optical properties that respond to external environments are being developed to reduce energy consumption in buildings.In the present study,we introduce a new type of 3D printed hydrogel with amazing flexibility and stretchability(as large as 1500%),as well as tunable optical performance controlled by surrounding temperatures.The hydrogel on a PDMS substrate shows transparent-opaque transition with high solar modulation(ΔT_(sol))up to 79.332% around its lower critical solution temperature(L_(CST))while maintaining a high luminous transmittance(T_(lum))of 85.847% at 20℃.In addition,selective transparent-opaque transition above LCST can be achieved by patterned hydrogels which are precisely fabricated via a projection micro-stereolithography based 3D printing technique.Our hydrogel promises great potential applications for the next generation of soft smart windows.

Bee Colony Optimization Algorithm for Routing and Wavelength Assignment Based on Directional Guidance in Satellite Optical Networks

With the development of satellite communication,in order to solve the problems of shortage of on-board resources and refinement of delay requirements to improve the communication performance of satellite optical networks,this paper proposes a bee colony optimization algorithm for routing and wavelength assignment based on directional guidance(DBCO-RWA)in satellite optical networks.In D-BCORWA,directional guidance based on relative position and link load is defined,and then the link cost function in the path search stage is established based on the directional guidance factor.Finally,feasible solutions are expanded in the global optimization stage.The wavelength utilization,communication success probability,blocking rate,communication hops and convergence characteristic are simulated.The results show that the performance of the proposed algorithm is improved compared with existing algorithms.

Bionic microchannels for step lifting transpiration

Those various cross-sectional vessels in trees transfer water to as high as 100 meters,but the traditional fabrication methods limit the manufacturing of those vessels,resulting in the non-availability of those bionic microchannels.Herein,we fabricate those bionic microchannels with various cross-sections by employing projection micro-stereolithography(PμSL)based 3D printing technique.The circumradius of bionic microchannels(pentagonal,square,triangle,and five-pointed star)can be as small as 100μm with precisely fabricated sharp corners.What's more,those bionic microchannels demonstrate marvelous microfluidic performance with strong precursor effects enabled by their sharp corners.Most significantly,those special properties of our bionic microchannels enable them outstanding step lifting performance to transport water to tens of millimeters,though the water can only be transported to at most 20 mm for a single bionic microchannel.The mimicked transpiration based on the step lifting of water from bionic microchannels is also achieved.Those precisely fabricated,low-cost,various cross-sectional bionic microchannels promise applications as microfluidic chips,long-distance unpowered water transportation,step lifting,mimicked transpiration,and so on.

基于跨层蚁群优化的近地轨道卫星网络路由算法(英文)

To improve the robustness of the Low Earth Orbit(LEO) satellites networks and realise load balancing, a Cross-layer design and Ant-colony optimization based Load-balancing routing algorithm for LEO Satellite Networks(CAL-LSN) is proposed in this paper. In CALLSN, mobile agents are used to gather routing information actively. CAL-LSN can utilise the information of the physical layer to make routing decision during the route construction phase. In order to achieve load balancing, CALLSN makes use of a multi-objective optimization model. Meanwhile, how to take the value of some key parameters is discussed while designing the algorithm so as to improve the reliability. The performance is measured by the packet delivery rate, the end-to-end delay, the link utilization and delay jitter. Simulation results show that CAL-LSN performs well in balancing traffic load and increasing the packet delivery rate. Meanwhile, the end-to-end delay and delay jitter performance can meet the requirement of video transmission.

Grating lobes suppression method for stepped frequency GB-SAR system

A grating lobes suppression method for chirp-subpulse stepped frequency(CSSF) signals is proposed, which is applied to deformation monitoring using the ground based synthetic aperture radar(GB-SAR) system. This method is based on accurate estimation and correction of the phase and amplitude error along two dimensions(range and azimuth), i.e., the error estimation inside the subpulse(in-subpulse error) and across the stepped frequency subpulses(cross-subpulse error) of transmitted CSSF signals. Validated both with simulated data and experimental data recorded in the deformation monitoring campaign, it can be seen that the method as well as the relative conclusions can be fully and effectively applied to most of the stepped frequency systems.

Supported ionic liquid phase-boosted highly active and durable electrocatalysts towards hydrogen evolution reaction in acidic electrolyte

Platinum is generally known as the most effective electrocatalyst for hydrogen evolution reaction because it can greatly lower the overpotential and accelerate the reaction kinetics,while its commercial potential always suffers from scarcity,high cost,low utilization,and poor durability particularly in acidic electrolytes.We herein demonstrate a facile method to improve the hydrogen evolution performance of Pt-based electrocatalysts by simply decorating the-state-of-the-art and commercially available Pt/C with hydrophobic protic([DBU][NTf2])or aprotic([BMIm][NTf2])ionic liquid.The current densities of[BMIm]@Pt/C and[DBU-H]@Pt/C with 10% ionic liquid at an overpotential of 40 mV are 2.81 and 4.15 times,respectively,higher than that of the pristine Pt/C.More importantly,ionic liquid-decoration significantly improves the long-term stability of Pt nanoparticles.After 8 h of chronoamperometric measurements,[DBU-H]@Pt/C and[BMIm]@Pt/C can still retain 83.7% and 78.3% of their original activity,respectively,which is much higher than that of the pristine Pt/C(24.4%).The improved performance of Pt/C decorated with ionic liquid is considered to arise from the improved proton conductivity(particularly for protic ionic liquid)and hydrophobic microenvironment created by the supported ionic liquid phase.The presence of ionic liquid layer not only de-coordinates H+from hydronium ions nearby the Pt nanoparticles,but it also protects Pt nanoparticles from dissolution in the acidic media.

A Satellite Communication System Transmission Scheme Based on Probabilistic Shaping

In this paper, A transmission scheme based on probabilistic shaping applied to satellite communication systems is proposed. 16QAM is taken as an example to establish a 1GBaud ROF experimental system working in Ka-band. The experiment results show that the PS-16QAM signal has better performance in terms of bit error rate than the uniform 16QAM, and its performance is close to the uniform 8QAM scheme.

Autonomous Assembly Method of 3-Arm Robot to Fix the Multipin and Hole Load Plate on a Space Station

Using space stations for a large number of observation, exploration, and research is a necessary way to fully develop spacetechnology. It is a necessary means of space experiment to install the extravehicular experimental load by using the loadplate. However, the extravehicular environment is full of danger, which poses a threat to the health and even safety ofastronauts. Using robots to replace astronauts to complete this task can effectively reduce the threat to astronauts. Aimingat the problem that the configurations of existing space robots have difficulty in balancing the contradiction betweencomplexity and dexterity, our previous work proposes a 12-DOF 3-arm robot and preliminarily explores the feasibility ofits large-scale ability. This paper focus on the 8-DOF redundant dexterous manipulator composed of 2 of the robot arms.In view of the difficulties in solving the inverse kinematics of the redundant manipulator, the challenges of complexenvironmental lighting, and difficulties of matching multiple groups of holes and pins in the load plate assembly task, theresearch on the autonomous assembly of the load plate is carried out. The main work is as follows: (a) A variable D-Hparameter inverse kinematics solution method is proposed, which lays a foundation for humanoid dexterous operationplanning of the robot. (b) An autonomous operation method based on visual guidance and variable parameter admittancecontrol is proposed. Finally, the safety and robustness of the robot in the autonomous assembly of the load plate withmultipins and holes are successfully verified by experiments.

Size,morphology,and composition of lunar samples returned by Chang'E-5 mission

This study focuses on the physical and chemical properties of surficial lunar regolith(LR)samples returned from the Moon by the Chang’E-5(CE-5)mission.Insights regarding the effect of a new sampling geological site on the surficial lunar sample CE5 C0400 were illustrated using nondestructive techniques such as laser diffractometry coupled with image analysis,X-ray computed tomography,and field emission scanning electron microscopy equipped with energy dispersive spectroscopy,and Xray diffraction combined with Rietveld refinement.From the characterization analyses,the CE-5 sampling site in the northeastern Oceanus Procellarum on the Moon yields a unique collection of relatively regular-shaped and fine basalt-dominated particles.The median grain size D_(50) is(55.24±0.96)μm,falling within the relatively low end of the range of the Apollo lunar returned samples.The coefficient of uniformity C_(u)of 15.1 and the coefficient of curvature C_(c)of 1.7 could classify CE5 C0400 to be well-graded.The minerals in CE5 C0400 comprise approximately 44.5%pyroxene,30.4%plagioclase,3.6%olivine,and6.0%ilmenite.There is a relatively low content of approximately 15.5%glass phase in the CE-5 lunar sample.From the results,we deduce that the CE-5 LR structure could have mainly resulted from micrometeoroid impacts to achieve such a high level of maturity.

Taking advantage of glass:capturing and retaining the helium gas on the moon

Helium-3(3He)is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy.It is thought that the lunar regolith contains large amounts of helium,but it is challenging to extract because most helium atoms are reserved in defects of crystals or as solid solutions.Here,we find large amounts of helium bubbles in the glassy surface layer of ilmenite particles that were brought back by the Chang’E-5 mission.The special disordered atomic packing structure of glasses should be the critical factor for capturing the noble helium gas.The reserves in bubbles do not require heating to high temperatures to be extracted.Mechanical methods at ambient temperatures can easily break the bubbles.Our results provide insights into the mechanism of helium gathering on the moon and offer guidance on future in situ extraction.

Potential development of all-inorganic perovskites

The energy consump tion is increasing rapidly with the continuous development of human society.Currently,global energy still mainly depends on fossil fuels.As awareness of the negative impact on the environment of burning fossil fuels,much attention has put on exploring clean and renewable energy.The solar energy has got the limitless foreground as a kind of renewable energy and photovoltaic devices can convert solar energy into electricity directly.

Generalized Maximum Correntropy Kalman Filter for Target Tracking in TianGong-2 Space Laboratory

Target tracking plays an important role in the construction,operation,and maintenance of the space station by the robot,which puts forward high requirements on the accuracy of target tracking.However,the special space environment may cause complex non-Gaussian noise in target tracking data.And the performance of traditional Kalman Filter will deteriorate seriously when the error signals are non-Gaussian,which may lead to mission failure.In the paper,a novel Kalman Filter algorithm with Generalized Maximum Correntropy Criterion(GMCKF)is proposed to improve the tracking accuracy with non-Gaussian noise.The GMCKF algorithm,which replaces the default Gaussian kernel with the generalized Gaussian density function as kernel,can adapt to multi-type non-Gaussian noises and evaluate the noise accurately.A parameter automatic selection algorithm is proposed to determine the shape parameter of GMCKF algorithm,which helps the GMCKF algorithm achieve better performance for complex non-Gaussian noise.The performance of the proposed algorithm has been evaluated by simulations and the ground experiments.Then,the algorithm has been applied in the maintenance experiments in TianGong-2 space laboratory of China.The results validated the feasibility of the proposed method with the target tracking precision improved significantly in complex non-Gaussian environment.

Mathematical prototypes for collocating geostationary satellites

Collocating geostationary satellites sharing the same position is much demanded for satellite operation recently,the separation strategies are adopted to safeguard the satellites collocated of leaving the relative distance beyond collision with different sets of orbit parameters.This paper presents the mathematical prototypes which establish the allowable relative distance with uncertainty of orbital determination(OD),as well as the orbital element offset for each pair of collocated satellites,and puts forward algorithms to build such relationship to face the challenge of putting three satellites sharing the same position,the algorithms to allocate the longitude,eccentricity and inclination for each satellite are also given to ascertain that the mathematical prototypes are the guide specification to design collocation strategy for geostationary satellites.

On time transfer in X-ray pulsar navigation

X-ray pulsar navigation(XPNAV) is a new approach for spacecraft autonomous navigation.The system gets position information utilizing accurate timing methods.Among the timing models,the high-order relativistic effects on the propagated signal must be incorporated to attain precise timing.The time transfer model is provided in detail here in two parts:the time frame transformation and the relativistic effects.

Karst Cave as Terrestrial Simulation Platform to Test and Design Human Base in Lunar Lava Tube

Developing efficient approaches to building a suitable environment for humans on the moon play a key role in future long-term sustainable lunar exploration activities,which has motivated many countries to propose diverse plans to build a lunar base.The lava tubes discovered by the Kaguya mission offer huge potential sites to host such bases.Through computation and analysis,we show that lunar lava tubes offer stable structures,suitable temperatures,low radiation doses,and low meteorite impact rates.We summarize previous research results and put forward the conditions to find and use a suitable lunar lava tube for human habitation on the moon.The establishment of extraterrestrial bases still faces many technical bottlenecks;many countries have begun to use the earth’s environment for extraterrestrial exploration and simulation missions.In this regard,we proposed the idea of using the Earth’s karst caves to simulate extraterrestrial lava tubes,selected caves in Chongqing as the simulation site,and demonstrated the feasibility from both structural and environmental aspects.Finally,we proposed a karst cave simulation platform with three main research directions:cave sealing technology,efficient daylight system,and internal circulation research of artificial ecosystems containing natural soil and rock.We hope to promote the development of related research on extraterrestrial bases through simulation experiments.