科创中国

DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics(CFD) and computational aerodynamic acoustics(CAA) simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures(i.e. the heat sink, the bell-mouth type shroud and the outlet grille) upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring's size and throat's depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %(i.e. 100 m3·h-1) at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.

Layered organic-inorganic hybrids containing bilayer perovsikte (R-NH3)2(CH3NH3)Pb2I7 (where R=C12H25,C6H5C2H4) were synthesized by reactions in solution. The influences of the solvents and the reactant ratio on the structures of the products were investigated. The structures and the properties of the hybrids were characterized using X-ray diffraction (XRD) and ultraviolet and visible (UV) adsorption spectra. For comparing with the bilayer perovskite hybrids in structure and band gap magnitude, the hybrids containing monolayer perovskite (R-NH3)2PbI4 were also synthesized and characterized. The results demonstrate that the thickness of inorganic layer has obvious effect on the tunneling magnitude of the band gap but the organic part can be micro actuator of band gap.

Many attentions for structural synthesis are paid to planar linkages and parallel mechanisms, while design novel pyramid deployable truss structure(PDTS) of satellite SAR mainly depends on experience of designer. To design novel configuration of PDTS, a two-step topology structure synthesis and analysis approach is proposed. Firstly, a conceptual configuration of PDTS is synthesized. Weighted graph and weighted adjacency matrix are established to realize topological description for PDTS. Graph properties are then summarized to distinguish differentia between PDTS and other type structures. According to graph properties, a procedure for synthesis conceptual configuration of PDTS is presented. Secondly, join relationship of components in a PDTS is analyzed. Kinematic chain and corresponding incidence/adjacency matrix are employed to analyze join relationship of PDTS. Properties and simplified rules of kinematic chain are extracted to construct kinematic chain. A procedure for construction kinematic chain of PDTS is then established. Finally, with this two-step approach all 11 rectangular pyramid deployable structures whose folded state is planar are discovered and their kinematic chains are constructed. Based on synthesis results, a novel deployable support structure for satellite SAR is designed. The proposed research can be applied to obtain some novel PDTSs, which is of great importance to design some novel deployable support structures for satellite SAR antenna.

分析专业图书馆实现知识服务转型的4个主要方面及对图书馆人员结构的需求,包括建设多元化数字资源保障体系、探索面向专业领域的知识服务模式、试验开展集成化知识环境建设、创建柔性灵活的团队与协作机制.结合以国家科技文献中心成员单位为代表的专业图书馆人员队伍结构,分析其人员队伍状况,阐明专业图书馆人员结构与未来发展存在业务布局、专业能力、信息技术水平、组织管理体制等方面的差距.

采用乙二胺水杨醛sch诳碱配体与水合硝酸铜配位生成了一雁形的双核Cu(II)配合物.产物通过了元素分析、红外光谱及单晶x射线衍射分析等手段的证实.结果表明,该配合物晶体属于单斜晶系,P21/c空间群,晶胞参数为:a=0.8559(14),b=2.3276(4),c=1.1057(18)nm,β=91.360(4)°,V=2.2021(6)nm3,Z=2,Do=1.706g/cm3,M=1130.82,RI=0.0.543,wR2=0.1522;结构分析表明,配合物中存在两种截然不同的Cu(II)配位模式,Cu(1)离子采取四方平面构型,Cu(2)离子却为扭曲八面体几何构型.

Current research on the operational reliability of centrifugal pumps has mainly focused on hydrodynamic instability. However, the interaction between the fluid and structure has not been sufficiently considered; this interaction can cause vibration and dynamic stress, which can affect the reliability. In this study, the dynamic stresses in a single-blade centrifugal pump impeller are analysed under different operating conditions; the two-way coupling method is used to calculate the fluid–structure interaction. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations are solved with the SST k–ω turbulence model for the fluid in the whole flow passage, while transient structure dynamic analysis is used with the finite element method for the structure side. The dynamic stresses in the rotor system are computed according to the fourth strength theory. The stress results show that the highest stress is near the loose bearing and that the equivalent stress increases with the flow rate because the dynamic stresses are closely related to the pressure load. The stress distributions on the blade pressure side, suction side, leading edge, and trailing edge are each analysed for different flow rates; the highest stress distribution is found on the pressure side. On the blade pressure side, a relatively large stress is found near the trailing edge and hub side. Based on these results, a stress distribution prediction method is proposed for centrifugal pumps, which considers the interaction between the fluid and structure. The method can be used to check the dynamic stress at different flow rates when optimising the pump design to increase the pump reliability.

针对电子战中敌方雷达的快速定位,设计了一种基于三基线干涉仪的二维瞬时测向系统,解决了在宽频带范围内保证测向视角和精度的难题.给出了系统的工作原理、电路结构以及软件算法,并重点介绍了信号处理组件的设计等关键技术.试验结果表明,该测向系统在X波段全频带内的测向视角达到了±60°,测角精度优于1°.

本文认为,基层税收征管体系改革,必须以明确征纳双方法律权责、切实提高纳税遵从度和科学可控为目标.在改革原则上,要后移控制措施,前置应需服务;注重分析预警,加强税源管控;强化激励监督,健全内部管理.在整体架构设计上,应划分为宣导办税、税务管理和检查内控3个环节,其工作重点分别为满足需求、预警控制和监督考核.

主要探讨产品模块化设计与供应链战略协同设计问题,从产品模块化程度的考量因素分析其带来的收益及对供应链的影响,结合企业案例分析,提出产品模块化和供应链的设计决策,从而为企业模块化产品开发设计提供参考.

Parallel robots with SCARA(selective compliance assembly robot arm) motions are utilized widely in the field of high speed pick-and-place manipulation. Error modeling for these robots generally simplifies the parallelogram structures included by the robots as a link. As the established error model fails to reflect the error feature of the parallelogram structures, the effect of accuracy design and kinematic calibration based on the error model come to be undermined. An error modeling methodology is proposed to establish an error model of parallel robots with parallelogram structures. The error model can embody the geometric errors of all joints, including the joints of parallelogram structures. Thus it can contain more exhaustively the factors that reduce the accuracy of the robot. Based on the error model and some sensitivity indices defined in the sense of statistics, sensitivity analysis is carried out. Accordingly, some atlases are depicted to express each geometric error's influence on the moving platform's pose errors. From these atlases, the geometric errors that have greater impact on the accuracy of the moving platform are identified, and some sensitive areas where the pose errors of the moving platform are extremely sensitive to the geometric errors are also figured out. By taking into account the error factors which are generally neglected in all existing modeling methods, the proposed modeling method can thoroughly disclose the process of error transmission and enhance the efficacy of accuracy design and calibration.