Research on the repeated folding mechanism of membrane antennas based on crease endurance degradation

Microalgal biodiesel production is constrained by inefficient lipid biosynthesis and energy-intensive harvesting process.Here, we report a cationic amphiphilic photoactive antenna TPyD with aggregation-induced emission, which programs microalgae to overcome these...

An efficient vibration control method for large-size space membrane antenna structure is of great practical value and research interest to maintain the on-orbit working performance of the spacecraft. In this paper, a novel cooperative nonlinear vibration control method of membrane antenna structure with piezoelectric and cable actuators is presented. A reduced-order nonlinear dynamic model of the membrane antenna structure is obtained based on the proper orthogonal decomposition (POD) method first. Then, based on the reduced nonlinear dynamic model, a cooperative nonlinear vibration controller that can make the piezoelectric actuators and cable actuators work stably and complementarily is designed. Simulation results show that the reduced-order nonlinear dynamic model can characterize the nonlinear dynamics of the membrane antenna structure effectively, the cooperative controller can achieve better vibration suppression effect with less control effort comparing to conventional control methods, and the proposed cooperative controller is robust to model parameter disturbance, actuator disturbance and sensor disturbance.

As accuracy of the reflector surface of a space parabolic deployable antenna is an important factor to determine its electrical characteristics (transmission gain and side lobes), mechanical characteristics of parabolic antennas under various internal pressures should be studied. The objective of this paper is to explore the force analysis of parabolic antennas by theoretical method and to estimate the effect of different air pressures on the surface precision of parabolic antennas via experiments in horizontal and vertical directions, and then a numerical analysis of the vibration characteristics of the parabolic antenna is proposed to explore the transient response of parabolic antennas. It is found that the ratio of tension reduces as depth of the parabolic membrane increases and can infinitely converge to 1/2. For precision analysis, it is concluded that precision of the parabolic membrane surface in a vertical state is higher than that in a horizontal state.

In-vivo spectral recomposition of sunlight with glycosylated aggregation-induced emission antennas for boosting photosynthesis.

Active nonlinear vibration suppression of membrane antenna spacecraft by using the measurement and control on the hub satellite

Space membrane structures typically operate under tension, requiring a new geometric shape to be obtained through form-finding analysis, followed by vibration analysis based on the updated structure. Additionally, the impact of air on membrane vibration during ground modal testing cannot be ignored. In traditional approaches to membrane analysis, form finding and vibration analyses with pretension and air effects are conducted separately using various techniques (numerical methods or commercial software), making the process highly cumbersome. This paper introduces a unified modeling and analysis strategy within the framework of isogeometric analysis (IGA) to effectively address this challenge. First, non-uniform rational B-splines (NURBS), known for their natural high-order continuity, are employed to discretize the membrane structure. Combined with the dynamic relaxation method, efficient form-finding analysis of the membrane structure is conducted, ensuring a seamless integration between structural design and form finding. Subsequently, based on the new geometric shape, vibration analyses of space membrane structures considering pretension and air effects are performed by updating the stiffness matrix and introducing the added mass method. The proposed strategy leverages the precise modeling and efficient analysis capabilities of IGA and enables multi-demand analysis of space membrane structures using a unified model. The numerical examples validate the correctness and efficiency of the proposed strategy using benchmark cases. Additionally, the proposed strategy is applied to the multi-demand analysis of membrane antenna arrays.

Cationic tetraphenylethylene (TPE)-based amphiphiles were developed as membrane antennas to enhance photosynthesis. The positioning of the TPE group was adjusted to balance ultraviolet to blue light conversion, significantly boosting photosynthetic activity.

Rigid-Flexible-Thermal Coupling Dynamic Modeling and Hybrid Control of Membrane Antenna Spacecraft

Design and demonstration of a roll-out membrane antenna based on thin-walled deployable composite booms

This study investigates the deployment reliability of multifunctional membrane deployable space structures that can be compactly stored and deployed in a two-dimensional direction using carbon composite booms to realize the construction of thin-film solar arrays and membrane antennas. Herein, two aspects are experimentally clarified using the structural models of a nano-satellite OrigamiSat-1, which is a 1 m-by-1 m square multifunctional deployable membrane structure demonstrator. First, a measurement system is developed to quasi-statically quantify the deployment torque of the structural models that failed to complete deployment after long-term storage and fell into an undesirable equilibrium shape. The measurement results confirm that the deployment torque decreases with long-term storage of the structure, and the torque in the deployment direction becomes negative at the deployment angle of the undesirable equilibrium shape. Therefore, as the second contribution, design modifications are made to the boom and membrane, and quasi-static and dynamic deployment tests are employed to evaluate their effects. The deployment reliability evaluation method and two design updates proposed herein will contribute to future space demonstrations and the utilization of lightweight membrane deployment structures with high packaging efficiency.

Cyanobacteria respond to iron limitation by producing the pigment-protein complex IsiA, forming rings associated with photosystem I (PSI). Initially considered a chlorophyll-storage protein, IsiA is known to act as an auxiliary light-harvesting antenna of PSI, increasing its absorption cross-section and reducing the need for iron-rich PSI core complexes. Spectroscopic studies have demonstrated efficient energy transfer from IsiA to PSI. Here we investigate the room-temperature excitation dynamics in isolated PSI-IsiA, PSI, IsiA monomer complexes and IsiA aggregates using two-dimensional electronic spectroscopy. Cross analyses of the data from these three samples allow us to resolve components of energy transfer between IsiA and PSI with lifetimes of 2-3 ps and around 20 ps. Structure-based Förster theory calculations predict a single major timescale of IsiA-PSI equilibration, that depends on multiple energy transfer routes between different IsiA subunits in the ring. Despite the experimentally observed lifetime heterogeneity, which is attributed to structural heterogeneity of the supercomplexes, IsiA is found to be a unique, highly efficient, membrane antenna complex in cyanobacteria.

At the Royal Society meeting in 2023, we have mainly presented our lunar orbit array concept called DSL, and also briefly introduced a concept of a lunar surface array, LARAF. As the DSL concept had been presented before, in this article, we introduce the LARAF. We propose to build an array in the far side of the Moon, with a master station which handles the data collection and processing, and 20 stations with maximum baseline of 10 km. Each station consistsof 12 membrane antenna units, and the stations are connected to the master station by power line and optical fibre. The array will make interferometric observation in the 0.1-50 MHz band during the lunar night, powered by regenerated fuel cells. The whole array can be carried to the lunar surface with a heavy rocket mission, and deployed with a rover in eight months. Such an array would be an important step in the long-term development of lunar-based ultralong wavelength radio astronomy. It has a sufficiently high sensitivity to observe many radio sources in the sky, though still short of the dark age fluctuations. We discuss the possible options in the power supply, data communication, deployment etc. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades (part 2)'.

High surface accuracy design of the electrostatically controlled deployable membrane antenna based on a thermoplastic forming method

Design and experimental verification of an adjustable constant-force mechanism

It is of great significance for the improvement of the computational efficiency of the electrostatically controlled membrane antenna (ECMA) structural-electromagnetic coupling model through the choice of appropriate mesh size and integration points number. In this paper, the physical optics formulation is used to analyze the radiation pattern of the ECMA surface, and the finite element method is applied to the electrostatic-structural coupling analysis. An expression for the relation between the mesh size, the focal length of the parabolic antenna, and the wavelength is developed based on the discretization error analysis of the triangular mesh approximating the parabolic surface. Moreover, the integration points number in each triangular mesh is determined by the numerical evaluation of the physical optics integral. Numerical results show that the proposed method improves the computing efficiency by about 87% compared with the referenced method.

A new structural-electromagnetic coupling (SEC) analysis based on quadratic elements is proposed to solve the mismatch problem between structural elements and electromagnetic grids of the electrostatically controlled deployable membrane antenna (ECDMA). Firstly, the ECDMA reflector surface is meshed and redefined by a series of quadratic elements. Without grid transformation, the calculating formulas for the far-field pattern of ECDMA are derived by the physical-optics method. Then the structural deformation of ECDMA is analyzed and the far-field pattern calculating formulas including deformation errors are developed. Simulation and experiment results show that the quadratic elements are effective and efficient in SEC analysis of the ECDMA, moreover, the electromagnetic grid size demand and the grid discretization error are reduced greatly.

Review of dynamics and active control of large-scale space membrane antenna

Detecting primordial fluctuations from the cosmic dark ages requires extremely large low-frequency radio telescope arrays deployed on the far side of the Moon. The antenna of such an array must be lightweight, easily storable and transportable, deployable on a large scale, durable, and capable of good electrical performance. A membrane antenna is an excellent candidate to meet these criteria. We study the design of a low-frequency membrane antenna for a lunar-based low-frequency (<30 MHz) radio telescope, constructed from polyimide film widely used in aerospace applications, owing to its excellent dielectric properties and high stability as a substrate material. We first design and optimize an antenna in free space, through dipole deformation and coupling principles, then simulate an antenna on the lunar surface with a simple lunar soil model, yielding an efficiency greater than 90% in the range of 12-19 MHz, and greater than 10% in the range of 5-35 MHz. The antenna inherits the omni-directional radiation pattern of a simple dipole antenna in the 5-30 MHz frequency band, giving a large field of view, and allowing detection of the 21 cm global signal when used alone. A demonstration prototype is constructed, and its measured electrical property is found to be consistent with simulated results using |S₁₁| measurements. This membrane antenna can potentially fulfill the requirements of a lunar low-frequency array, establishing a solid technical foundation of future large-scale array for exploring the cosmic dark ages.

Numerical and experimental study on the dynamic equivalent methodology of a membrane antenna structure and a grid membrane structure