在轨维修后端模块接口机构的研究

在轨维修可以大大的延长空间科学仪器的使用寿命,节省大量的经济成本。为了实现空间望远镜后端模块的在轨操作和更换,设计了一套与之对应的接口机构,能够解决在轨快速定位与安装。根据321运动学定位准则,详细介绍了该接口机构的内部组成和工作原理;然后把该接口机构与后端模块进行组件级有限元仿真,仿真结果表明一阶模态远高于整机基频可以有效地避免发射时候的共振;设计了一套平面内的工装来模拟后端模块,利用等效质量法对整个机构进行重力卸载;搭建实验平台,利用激光跟踪仪来测量整个后端模块的重复定位安装精度,实验数据表明,X,Y,Z 3个方向的重复平移定位误差分别为±5.58μm,±3.24μm及±3.63μm,优于总体指标±10μm;热实验结果表明整个机构可以完全释放由于温度变化产生的形变,具有很高的热稳定性;使入射光线和靶面的相对位置持续稳定,保证了较高的成像质量。为其他空间在轨维护装置提供强有力的参考价值。     

Defect structure evolution and electrical properties of BaTiO3-based ferroelectric ceramics

Relaxor perovskite ferroelectric 0.1Bi(Zn_1/2Zr_1/2)O₃-0.9BaTiO₃(0.1BZZ-0.9BT) ceramics were successfully prepared, whose powders synthesized by the sol-gel process, with average grain size about 1.29 μm. 1.75 J/cm³ discharge energy density and good dielectric stability were obtained over a wide temperature range from 25°C to 140°C. The pulse discharge capability of 0.1BZZ-0.9BT ceramics was tested under different electric fields. The discharge time was 2.13 μs, which proved its ability to charge and discharge quickly. Complex impedance analysis and thermally stimulated depolarization current tests were applied to investigate the defect types and activation of 0.1BZZ-0.9BT ceramics. The evolution process of composite defects and oxygen vacancies profoundly affects the dielectric temperature stability of 0.1BZZ-0.9BT ceramics’ energy storage property.     

Transition-Metal-Catalyzed 1,2-Carboboration of Alkenes: Strategies,Mechanisms, and Stereocontrol

During the past decade, many research groups have described catalytic methods for 1,2-carboboration, allowing access to structurally complex organoboronates from alkenes. Various transition metals, especially copper, palladium, and nickel, have been widely used in these reactions. This review summarizes advances in this field, with a special focus on the catalytic cycles involved in different metal-catalyzed carboboration reactions, as well as the regio- and stereochemical consequences of the underlying mechanisms. 1,2-Carboboration of other unsaturated systems, such as alkynes and allenes, is outside of the scope of this review.     

Strengthen flame retardancy of epoxy thermoset by montmorillonite particles adhering phosphorus-containing fragments

Phosphaphenanthrene derivative tri-(3-DOPO-2-hydroxypropan-1-yl)-1,3,5-triazine-2,4,6-trione (TGD) and organo-modified montmorillonite (OMMT) were jointly introduced into the diglycidyl ether of bisphenol A cured by 4,4-diamino-diphenylmethane (EP) to investigate their flame retardant behaviors. With only addition of 0.5%OMMT and 2.5%TGD, epoxy thermoset achieved a limiting oxygen index value of 33.7% and passed UL 94 V-0 rating test. Compared with the combustion behaviors of 3%OMMT/EP and 3%TGD/EP, an obvious synergistic flame retardant effect between OMMT and TGD can be concluded in OMMT/TGD/EP. Meanwhile, the FTIR spectra of gas-phase and condensed-phase products further proved this synergistic effect working in a physical way. On one hand, the co-existence of hydroxyl-containing TGD enabled montmorillonite (MMT) particles to filtrate and adhere more smoke fragments. On the other hand, the co-action of MMT help the polar phosphorus-containing fragments from TGD better strengthened char layer, enhancing the barrier and protective effect of residue. The synergistic flame retardant effect from OMMT/TGD system endowed themselves with higher flame retardant efficiency, and epoxy thermoset with better flame retardant performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47500.     

海底用喷涂聚氨酯硬泡保温配重管的节点补口技术

针对海洋油气输送用聚氨酯硬泡喷涂保温配重管铺设过程中节点补口进行改进研究,介绍了一种聚氨酯硬泡喷涂保温配重管节点结构和施工工艺。主要采用聚氨酯硬泡保温半瓦和浇注聚氨酯弹性体进行节点补口,节点补口性能测试验证效果良好,满足海底油气管道铺设要求。     

太西煤基新型功能炭材料的制备及其电化学性能

以宁夏太西煤高温直流电煅炉制备的煤基石墨为原料,利用Hummers氧化法制备了氧化石墨,然后分别采用水热法和高温膨胀法制备了煤基三维石墨烯气凝胶(3D-GA)和煤基膨胀石墨(EG)两种新型功能炭材料,并通过FTIR,XRD和SEM对其进行了表征,利用电化学工作站对其电化学性能进行了测试和比较。结果表明:在电流密度500 mA/g下,3D-GA和EG的比电容分别为206 F/g和214 F/g,相比煤基石墨烯粉体(G)的比电容113 F/g,分别提高了82.3%和89.4%;充放电循环1000圈后,3D-GA和EG的比电容保持率分别为95.1%和101%,3D-GA和EG均表现出良好的循环稳定性。     

Impact of texturing on the phase transitions in sol–gel-processed Bi(Sm)FeO3 thin films on LaNiO3-buffered silicon

The orientation modulation of ferroelectric materials is a suitable method to optimize material performance. Textured Bi_1-xSm_xFeO₃ thin films (near the rhombohedral-orthorhombic (R-O) phase boundary, that is, x = 0, 0.1, 0.12, 0.14, and 0.16) were fabricated using the sol-gel process by introducing a LaNiO₃ (LNO) seed layer. Structural and ferroelectric characterizations were used to investigate the effect of texturing on the Sm doping-induced R-O phase transition of the BiFeO₃ thin films. It was found that a phase transition occurred from the rhombohedral to the orthorhombic structure with increasing Sm content in the nontextured polycrystalline films, resulting in an R-O phase boundary at x = 0.12. In contrast, the R-O phase boundary in the textured films was more diffuse, indicating a two-phase coexistence in a boarder range of Sm doping levels (x = 0.12-0.16). This discrepancy was attributed to the complexity of the stress status in thin films. The dielectric and electrical properties of the nontextured and textured samples were investigated. The current study shows that the phase boundary in ferroelectric thin films can be altered by diverse means, thus providing insights into potential applications.     

Thermo-economic analysis and optimization of a combined Organic Rankine Cycle (ORC) system with LNG cold energy and waste heat recovery of dual-fuel marine engine

A combined Organic Rankine Cycle (ORC) system with liquefied nature gas (LNG) cold energy and dual-fuel (DF) marine engine waste heat utilization was proposed. Engine exhaust gas and engine jacket cooling water were adopted as parallel heat sources. Thermo-economic analyses of the proposed system with 32 working fluids combinations were performed. Two objective functions covering thermal efficiencies and economic index were employed for performance evaluation. Afterward, the effects of operation pressure on the objective functions were investigated. Finally, the optimal conditions were obtained from the Pareto front with the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) method. The results show that the proposed ORC system has better energy recovery performances than the parallel ORC system. R1150-R600a-R290, R1150-R601a-R600a, and R170-R601-R290 are determined as the three most promising working fluids combinations. Under optimized conditions, the output power range is 199.97 to 218.51 kW, the energy efficiency range is 13.64% to 15.62%, and the exergy efficiency range is 25.29% to 27.3%. The payback period ranges from 8.36 to 8.74 years. The working fluids selection helps to reduce the exergy destruction of intermediate heat exchanger, which could be up to 30.59%.     

采场顶板关键层"横U-Y"型周期破断特征的试验研究

针对部分坚硬顶板矿井采动导水裂缝带处于8~15倍采高的高位关键层,"横O-X"破断运动引发工作面动载矿压甚至压架、临采空侧回风平巷超前100~200 m底鼓大变形等动力灾害的问题,采用自制的大尺度三维物理模拟实验平台,研究高位关键层的破断运动特征。结果表明:关键层发生横向破断时,首先,关键层板正面两侧长边和反面中部长轴方向同时形成破断裂隙;其次,关键层板正面两侧短边形成弧形裂隙,而反面沿中轴线端点同步形成八字形破断裂隙;再次,在板正面形成"O"形裂隙的同时反面形成"X"形裂隙,正面形成"U"形裂隙的同时反面形成"Y"形裂隙;最后,正反面裂缝贯通形成"横O-X"型初次破断和"横U-Y"型周期破断,在工作面上方形成"弧形三角板"和巷道上方形成"梯形板"的破断块体结构。统计发现,"横O-X"型初次破断步距与"横U-Y"型周期破断步距长度基本一致;横向破断形成的"弧形三角板"块体角度为75°~78°,与腰线和弧形切线形成的夹角72°~82°基本相等,近似于一个等角的"弧形三角板"。砌块模型试验结果表明,"弧形三角板"块体大幅回转过程中,因其顶点易与"梯形板"结构发生回转变形失稳而出现脱离现象,导致"弧形三角板"滑落失稳从而会引发工作面强矿压。研究成果为大采高开采工作面强矿压灾害防治提供试验基础。     

Synthetic curli enables efficient microbial electrocatalysis with stainless-steel electrode

Microbial electrocatalysis systems (MES) provide a cutting-edge solution to global problems associated with the environment and energy, but practical applications are hindered by the expensive electrode materials. Although stainless steel (SS) has been proposed as a promising inexpensive candidate, poor cell/SS interaction results in a low performance for MES. Here, a new synthetic biology approach was established for reinforcing the cell/SS interaction. Hybridized curli nanofibers fused with a metal-binding domain were heterogeneously expressed onto the cell surface, which realized efficient cell binding with the SS electrode. Consequently, it enabled a ~420-fold improvement of the anodic power output and a substantial enhancement of the cathodic Coulombic efficiency (from 0.6 to 4% to over 80%) with an SS electrode. This work demonstrates low-cost MES with an SS electrode and introduces a new avenue to engineer the cell/electrode interaction, which is promising for future practical applications of MES.