Shape Memory Polymer Composite Booms with Applications in Reel-Type Solar Arrays

Solar arrays are the primary energy source for spacecraft.Although traditional rigid solar arrays improve power supply,the quality increases proportionally.Hence,it is difficult to satisfy the requirements of high-power and low-cost space applications.In this study,a shape-memory polymer composite(SMPC)boom was designed,fabricated,and characterized for flexible reel-type solar arrays.The SMPC boom was fabricated from a smart material,a shape-memory polymer composite,whose mechanical properties were tested.Additionally,a mathematical model of the bending stiffness of the SMPC boom was developed,and the bending and buckling behaviors of the boom were further analyzed using the ABAQUS software.An SMPC boom was fabricated to demonstrate its shape memory characteristics,and the driving force of the booms with varying geometric parameters was investigated.We also designed and manufactured a reel-type solar array based on an SMPC boom and verified its self-deployment capability.The results indicated that the SMPC boom can be used as a deployable unit to roll out flexible solar arrays.

GaP/GaPN核壳纳米线阵列修饰的硅光阴极的光电化学制氢反应（英文）

能够大规模同时提升电极的催化效率和稳定性对光电化学分解水系统的开发具有重要意义.硅是一种地球储量丰富且成熟的工业材料,由于其合适的带隙(1.1 eV)和优异的导电性,已被广泛用于光电化学制氢反应.然而,缓慢的表面催化反应和在电解液中的不稳定性限制了其在太阳能制氢中的实际应用.III-IV族半导体材料也具有较高的载流子传输特性且被广泛用于光电器件.其中,GaP的直接带隙和间接带隙分别为2.78和2.26 eV,可与硅组成串联型光电极用于光电化学分解水.然而,GaP的光腐蚀电位位于禁带中,很容易在光电催化过程中发生光腐蚀而导致性能大幅下降.本文报道了一种新型的GaP/GaPN核/壳纳米线修饰的p型硅(p-Si)串联型光阴极,同未修饰的p-Si相比,其光电化学制氢性能更高.这可归因于以下几点:(1)p-Si和GaP纳米线之间形成的p-n结促进了电荷分离;(2)GaPN相对于GaP具有更低的导带边位置,进一步促进了光生电子向电极表面的转移;(3)纳米线结构既缩短了光生载流子的收集距离,又增加了比表面积,从而加快了表面反应动力学.此外,在GaP中引入氮元素还提高了体系的光吸收和稳定性.我们所提出的高效、简便的改进策略可应用于其他的太阳能转换体系.利用简单的化学气相沉积法制备GaP/GaPN核/壳纳米线修饰的p-Si光阴极.首先在p-Si衬底上利用Au纳米颗粒作为催化剂生长GaP纳米线;然后,去除Au催化剂,并在氨气中退火便形成了GaP/GaPN核壳纳米线.高分辨透射电子显微镜,拉曼光谱和X射线光电子谱的表征结果均证实了氨气退火使得GaP纳米线表面形成了GaPN的薄壳层,同时证明了GaP/GaPN核壳纳米线具有可调的核壳结构.在模拟太阳光下作为光阴极用于光解水制氢反应时,GaP/GaPN核壳纳米线修饰的p-Si光阴极的起始电位为~0.14 V,而未修饰的p-Si电极的起始电位大约在?0.77 V.而且,GaP/GaPN核/壳纳米线修饰的p-Si光阴极比未修饰的p-Si光阴极具有更高的光电流密度,在水的还原电位下,其光电流密度为?0.3 mA cm^-2,且饱和光电流密度在?0.76 V时达到了?8.8 mA cm^-2.此外,GaP/GaPN核/壳纳米线修饰的p-Si光阴极的光电化学活性在10 h内没有发生明显下降.由此可见GaP/GaPN核/壳纳米线可以规模化有效地提升Si光电极的催化效率和稳定性.

Hierarchical molybdenum disulfide nanosheet arrays stemmed from nickel-cobalt layered double hydroxide/carbon cloth for highly-efficient hydrogen evolution reaction

The hierarchical structure of molybdenum disulfide(MoS2)nanosheet arrays stemmed from nickelcobalt layered double hydroxide(NiCo-LDH)/carbon cloth was prepared by growing the MoS_(2) nanosheet arrays onto the NiCo-LDH template which was pre-deposited onto the carbon cloth substrate.In this electrode configuration,carbon cloth is the three dimensional and conductive skeleton;NiCo-LDH nanosheets,as the template,ensure the oriented growth of MoS2 nanosheet arrays.Therefore,more MoS_(2) active sites are exposed and the catalyst exhibits good hydrogen evolution reaction activity.

面向大规模数据的高效超图神经网络

高阶关联广泛存在于现实世界中,如社交网络、生物网络、交通网络等,建模及优化高阶关联对于网络属性研究和演化趋势预测具有重要意义.超图是一种灵活的数据结构,能够自然地建模高阶关联.近年来,随着深度学习的发展,基于超图建模的超图神经网络被广泛应用于面向高阶关联的表示学习.然而,现有的超图神经网络均基于直推学习范式,虽然在小规模超图数据集上取得了不错的效果,但难以应用到大规模数据上,限制了其应用范围.本文首先分析了现有超图神经网络方法在大规模数据上应用的挑战,然后针对该问题提出了面向大规模数据的高效超图神经网络方法(efficient hypergraph neural network,EHGNN).针对现有方法空间、时间复杂度过高的问题,EHGNN分别设计了超图采样模块和基于单阶段超图卷积的计算加速模块,同时降低了超图神经网络的空间开销和时间开销,使得超图神经网络适用于大规模超图数据,显著增强了可扩展性.在4个真实超图数据集上的实验结果验证了EHGNN的有效性和高效性.

Multiband camouflage design with thermal management

Although the effective“stealth”of space vehicles is important,current camouflage designs are inadequate in meeting all application requirements.Here,a multilayer wavelength-selective emitter is demonstrated.It can realize visible light and dual-band mid-infrared camouflage with thermal control management in two application scenarios,with better effect and stronger radiation cooling capability,which can significantly improve the stealth and survivability of space vehicles in different environments.The selective emitter demonstrated in this paper has the advantages of simple structure,scalability,and ease of large-area fabrication,and has made a major breakthrough in driving multiband stealth technology from simulation research to physical verification and even practical application.

Zebrafish Foxc1a controls ventricular chamber maturation by directly regulating wwtr1 and nkx2.5 expression

Chamber maturation is a significant process in cardiac development. Disorders of this crucial process lead to a range of congenital heart defects. Foxc1a is a critical transcription factor reported to regulate the specification of cardiac progenitor cells. However, little is known about the role of Foxc1a in modulating chamber maturation. Previously, we reported that foxc1a-null zebrafish embryos exhibit disrupted heart structures and functions. In this study, we observe that ventricle structure and cardiomyocyte proliferation are abolished during chamber maturation in foxc1a-null zebrafish embryos. To observe the endogenous localization of Foxc1a in the hearts of living embryos, we insert eyfp at the foxc1a genomic locus using TALEN. Analysis of the knockin zebrafish show that foxc1a is widely expressed in ventricular cardiomyocytes during chamber development. Cardiac RNA sequencing analysis reveals the downregulated expression of the Hippo signaling effector wwtr1. Dual-luciferase and chromatin immunoprecipitation assays reveal that Foxc1a can bind directly to three sites in the wwtr1 promoter region. Furthermore, wwtr1m RNA overexpression is sufficient to reverse the ventricle defects during chamber maturation. Conditional overexpression of nkx2.5 also partially rescues the ventricular defects during chamber development. These findings demonstrate that wwtr1 and nkx2.5 are direct targets of Foxc1a during ventricular chamber maturation.