Thruster direction controlling of assembled spacecraft based on gimbal suspension

The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass will be changed in certain axe; consequently, some thrusters＇ directions are deviated from the center of mass（CM） in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters＇ directions is proposed. By using the gimbal installed at the end of the boom, the angle of the thruster is controlled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finally, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.

Overview of development, design, testing and application of compact gas-insulated DC systems up to ±550 kV

The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional density,optimized for projects with limited space as in offshore HVDC converter platforms,onshore HVDC converter stations and transition stations between different transmission media.Up to now,no standards for testing of gas-insulated DC systems are available,although pre-standardization work is in progress within CIGRE.Some tests can be performed as required in AC GIS standards.Special aspects of DC voltage stress,like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution,must be considered by additional electric and thermoelectric tests.For DC GIS,the experience of long-term performance is limited today.Although ageing is expected to be of lower importance,tests are recommended.This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology.It explains the developed modules of the substation and gives an overview of the performed tests.Furthermore,it provides an insight in the on-going standardization activities and describes applications in converter and transition stations,showing its space-saving characteristics.

Progress on direct assembly approach for in situ fabrication of electrodes of reversible solid oxide cells

Reversible solid oxide cells(SOCs)are very efficient and clean for storage and regeneration of renewable electrical energy by switching between electrolysis and fuel cell modes.One of the most critical factors governing the efficiency and durability of SOCs technology is the stability of the interface between oxygen electrode and electrolyte,which is conventionally formed by sintering at a high temperature of~1000–1250℃,and which suffers from delamination problem,particularly for reversibly operated SOCs.On the other hand,our recent studies have shown that the electrode/electrolyte interface can be in situ formed by a direct assembly approach under the electrochemical polarization conditions at 800℃and lower.The direct assembly approach provides opportunities for significantly simplifying the cell fabrication procedures without the doped ceria barrier layer,enabling the utilization of a variety of high-performance oxygen electrode materials on barrier layer–free yttria-stabilized zirconia(YSZ)electrolyte.Most importantly,the in situ polarization induced interface shows a promising potential as highly active and durable interface for reversible SOCs.The objective of this progress report is to take an overview of the origin and research progress of in situ fabrication of oxygen electrodes based on the direct assembly approach.The prospect of direct assembly approach in the development of effective SOCs and in the fundamental studies of electrode/electrolyte interface reactions is discussed.

Bottom-up synthesis of ultrathin straight platinum nanowires： Electric field impact

We present a study of the electric field effect on electrochemically grown ultrathin, straight platinum nanowires with minimum diameter of 15 nm and length in the micrometer range, synthesized on a silicon oxide substrate between metal electrodes in H2PtC16 solution. The influence of the concentration of the platinum- containing acid and the frequency of the applied voltage on the diameter of the nanowires is discussed with a corresponding theoretical analysis. We demonstrate for the first time that the electric field profile, provided by the specific geometry of the metal electrodes, dramatically influences the growth and morphology of the nanowires. Finally, we provide guidelines for the controlled fabrication and contacting of straight, ultrathin metal wires, eliminating branching and dendritic growth, which is one of the main shortcomings of the current bottom-up nanotechnology. The proposed concept of self-assembly of thin nanowires, influenced by the electric field, potentially represents a new route for guided nanocontacting via smart design of the electrode geometry. The possible applications reach from nanoelectronics to gas sensors and biosensors.

Design and Fabrication of Functional Hydrogels through Interfacial Engineering

Hydrogels have drawn considerable attention in the past two decades due to their excellent biocompatibility and multi-stimuli responsiveness. They have a wide range of applications in the fields related to tissue engineering, sensors and biomedicine. Their applications are strongly influenced by the surface properties of hydrogels and the interfacial interactions between hydrogels and other substrates. In particular, the surface wettability and adhesion of hydrogels decide their applications as drug carriers and wound dressing materials. Nevertheless, there is a lack of systematic discussion on the surface functionalization strategies of hydrogels. Therefore, this review aims at summarizing the strategies of functionalizing the surfaces of hydrogels and bonding hydrogels with other solid substrates. It also explores the challenges and future perspectives of interfacial engineering of hydrogels.

Lithographically directed assembly of one-dimensional DNA nanostructures via bivalent binding interactions

In order to exploit the outstanding physical properties of one-dimensional （1D） nanostructures such as carbon nanotubes and semiconducting nanowires and nanorods in future technological applications, it will be necessary to organize them on surfaces with precise control over both position and orientation. Here, we use a 1D rigid DNA motif as a model for studying directed assembly at the molecular scale to lithographically patterned nanodot anchors. By matching the inter-nanodot spacing to the length of the DNA nanostructure, we are able to achieve nearly 100% placement yield. By varying the length of single-stranded DNA linkers bound covalently to the nanodots, we are able to study the binding selectivity as a function of the strength of the binding interactions. We analyze the binding in terms of a thermodynamic model which provides insight into the bivalent nature of the binding, a scheme that has general applicability for the controlled assembly of a broad range of functional nanostructures.