Dynamic Analysis and Parametric Optimization of Telescopic Tubular Mast Applied on Solar Sail

Large-scale solar sails can provide power to spacecraft for deep space exploration.A new type of telescopic tubular mast(TTM)driven by a bistable carbon fiber-reinforced polymer tube was designed in this study to solve the problem of contact between the sail membrane and the spacecraft under light pressure.Compared with the traditional TTM,it has a small size,light weight,high extension ratio,and simple structure.The anti-blossoming and self-unlocking structure of the proposed TTM was described.We aimed to simplify the TTM with a complex structure into a beam model with equal linear mass density,and the simulation results showed good consistency.The dynamic equation was derived based on the equivalent model,and the effects of different factors on the vibration characteristics of the TTM were analyzed.The performance parameters were optimized based on a multiobjective genetic algorithm,and prototype production and load experiments were conducted.The results show that the advantages of the new TTM can complete the deployment of large-scale solar sails,which is valuable for future deep space exploration.

A Survey: Typical Security Issues of Software-Defined Networking

Software-Defined Networking (SDN) has been a hot topic for future network development, which implements the different layers of control plane and data plane respectively. Despite providing high openness and programmability, the “three-layer two-interface” architecture of SDN changes the traditional network and increases the network attack nodes, which results in new security issues. In this paper, we firstly introduced the background, architecture and working process of SDN. Secondly, we summarized and analyzed the typical security issues from north to south: application layer, northbound interface, control layer, southbound interface and data layer. Another contribution is to review and analyze the existing solutions and latest research progress of each layer, mainly including: authorized authentication module, application isolation, DoS/DDoS defense, multi-controller deployment and flow rule consistency detection. Finally, a conclusion about the future works of SDN security and an idealized global security architecture is proposed.

Novel Surface Design of Deployable Reflector Antenna Based on Polar Scissor Structures

Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering.This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units.The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods.Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized.A new closed-loop deployable structure,called the polar scissor deployable antenna(PSDA),is designed by combining planar polar scissor units with spatial polar scissor units.The overconstrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism.Kinematics simulation and error analysis are performed.The results show that the PSDA can effectively fit the paraboloid of revolution.Finally,deployment experiments verify the validity and feasibility of the proposed design method,which provides a new idea for the construction of large space-reflector antennas.

Design and application of solar sailing: A review on key technologies

Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost,no-propellant consumption,and continuous thrust,which has great potentials in earth polar detection,interstellar explorations and etc.The development of solar sail has made significant progress in structural design,manufacturing,materials,orbit transfer,and stability control in the past few decades,which makes meaningful contributions to astronomy,physics,and aerospace science.Technological breakthroughs of Solar Radiation Pressure(SRP)propulsion and interstellar transfer have been achieved in current solar sail missions.However,there are still many challenges and problems need to be solved.This paper attempts to summarize the research schemes and potential applications of solar sailing in space missions from the viewpoint of key technologies,so as to provide an overall perspective for researchers in this field.Analyses of the key technologies of solar sailing system design are provided.Finally,challenges and prospective development of solar sailing are discussed.

SIV:A Structural Integrity Verification Approach of Cloud Components with Enhanced Privacy

Private data leakage is a threat to current integrity verification schemes of cloud components. To address this issue, this work proposes a privacy-enhancing Structural Integrity Verification (SIV) approach. It is made up of three processes: proof organization, proof transformation, and integrity judgement. By introducing a Merkle tree technique, the integrity of a constituent part of a cloud component on a node is represented by a root value. The value is then masked to cipher texts in proof transformation. With the masked proofs, a structural feature is extracted and validated in an integrity judgement by a third-party verification provider. The integrity of the cloud component is visually displayed in the output result matrix. If there are abnormities, the corrupted constituent parts can be located. Integrity is verified through the encrypted masked proofs. All raw proofs containing sensitive information stay on their original nodes, thus minimizing the attack surface of the proof data, and eliminating the risk of leaking private data at the source. Although some computations are added, the experimental results show that the time overhead is within acceptable bounds.

ePUF: A Lightweight Double Identity Verification in IoT

Remote authentication is a safe and verifiable mechanism.In the Internet of Things (loT),remote hosts need to verify the legitimacy of identity of terminal devices.However,embedded devices can hardly afford sufficient resources for the necessary trusted hardware components.Software authentication with no hardware guarantee is generally vulnerable to various network attacks.In this paper,we propose a lightweight remote verification protocol.The protocol utilizes the unique response returned by Physical Unclonable Function (PUF) as legitimate identity basis of the terminal devices and uses quadratic residues to encrypt the PUF authentication process to perform a double identity verification scheme.Our scheme is secure against middleman attacks on the attestation response by preventing conspiracy attacks from forgery authentication.

Asymmetric Intramolecular Hydroalkoxylation of Unactivated Alkenes Catalyzed by Chiral N-Triflyl Phosphoramide and TiCl4

By using a combination of a chiral/V-triflyl phosphoramide and TiCl4 as the catalyst,a new process for asymmetric intramolecular hydroalkoxylation of unactivated alkenes was developed,producing various chiral tetrahydrofuran derivatives in 51%—99% yields with 30%—71%ee's.

1U-Sized Deployable Space Manipulator for Future On-Orbit Servicing,Assembly,and Manufacturing

Miniaturized,multifunctional,and economical on-orbit service satellites have been increasingly used with the continuous increase of space exploration missions.In this paper,an innovative deployable manipulator is designed,named Cubot,which can be stowed in 1 U-sized(10 cm×10 cm×10 cm)space.With CubeSat as the carrier,the deployable Cubot aims to achieve a variety of on-orbit operation tasks including space debris removal and space station on-orbit maintenance,for future on-orbit servicing,assembly,and manufacturing(OSAM).A kinematics modeling method of a space manipulator with passive joints is proposed,and the motion equation of the manipulator is derived.Considered the elastic potential energy stored in the passive joint during deployment,the momentum change of Cubot is simulated and analyzed.As the main forced element,the end effector is analyzed using FEA.Dynamic stress response with respect to the force distribution and the clamping angle is analyzed to evaluate mechanical performances of the end-effector component.Deployment tests are conducted to verify the feasibility of Cubot based on a principled prototype,which aims to provide engineering and practical experience for the development of this field.