摘要：7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical *** the process of deep hole boring,the boring bar is prone to vibrate because of its limited machining space,bad environment and large elongation induced low *** reduce vibration and improve machined surface quality,a particle damping boring bar,filled with particles in its inside damping block,is designed based on the theory of vibration *** theoretical damping coefficient is determined,then the boring bar structure is designed and *** studies through impact testing show that cemented carbide particles with a diameter of 5 mm and a filling rate of 70% achieve a damping ratio of 19.386%,providing excellent vibration reduction capabilities,which may reduce the possibility of boring ***,experiments are setup to investigate its vibration reduction performance during deep hole boring of 7075 aluminum *** observe more obviously,severe working conditions are adopted and carried out to acquire the time domain vibration signal of the head of the boring bar and the surface morphologies and roughness values of the *** comparing different experimental results,it is found that the designed boring bar could reduce the maximum vibration amplitude by up to 81.01% and the surface roughness value by up to 47.09% compared with the ordinary boring bar in two sets of experiments,proving that the designed boring bar can effectively reduce *** study can offer certain valuable insights for the machining of this material.

摘要：Three-dimensional printing technologies exhibit tremendous potential in the advancing fields of tissue engineering and regenerative medicine due to the precise spatial control over depositing the *** their widespread utilization and numerous advantages,the development of suitable novel biomaterials for extrusion-based 3D printing of scaffolds that support cell attachment,proliferation,and vascularization remains a ***-material composite hydrogels present incredible potential in this ***,in this work,a multi-material composite hydrogel with a promising formulation of chitosan/gelatin functionalized with egg white was developed,which provides good printability and shape *** addition,a series of comparative analyses of different crosslinking agents and processes based on tripolyphosphate(TPP),genipin(GP),and glutaraldehyde(GTA)were investigated and compared to select the ideal crosslinking strategy to enhance the physicochemical and biological properties of the fabricated *** of the results indicate that the composite hydrogel and the resulting scaffolds utilizing TPP crosslinking have great potential in tissue engineering,especially for supporting neo-vessel growth into the scaffold and promoting angiogenesis within engineered tissues.

摘要：This paper aims to design a MCU-based smart contactor system, which will realize functions of real time surveillance of contactors’ work status and data exchange with host computer, thus instantly reflect different status of the system. In case of abnormal status such as over-current or under-voltage, the contactor will be able to automatically cut off power supply to protect electrical load and the circuit. Through ARINC485 bus, system computer will collect and record contactor parameters, including contact voltage, contact current, supply frequency, contact temperature and contact status to provide critical data to the examination and repair of contactors.

摘要：The present study reports investigations on rheological,mechanical,thermal,tribological and morphological properties of feedstock filaments prepared with polylactic acid-polyether ketone ketone-hydroxyapatite-chitosan(PLA-PEKK-HAp-CS)composite for 3D printing of functional *** study consists of a series of melt processing operations on melt flow index(MFI)setup as per ASTM D-1238 for melt flow certainty followed by fixation of reinforcement composition/proportion as 94%PEKK-4%HAp-2%CS(B)by mass in PLA matrix(A).The blending of reinforcement and preparation of feedstock filament for fused deposition modeling(FDM)set up has been performed on commercial twin screw extruder(TSE).The results of study suggest that feedstock filaments prepared with blend of 95%A-5%B(by mass)at 200℃processing temperature and 100 r/min rotational speed on TSE resulted into better tensile properties(35.9 MPa peak strength and 32.3 MPa break strength)with 6.24%surface porosity,42.67 nm surface roughness(R_(a))and acceptable heat capacity(2.14 J/g).However as regards to tribological behavior,the minimum wear of 316μm was observed for sample with poor tensile *** regards to crash application for scaffolds the maximum toughness of 1.16 MPa was observed for 85%A-15%B(by mass)at 200℃processing temperature and 150 r/min rotational speed on TSE.

摘要：We study the coupling problem of two waveguide antennas using the design of a two-dimensional inhomogeneous impedance structure with a fixed reflected field. Since this structure enables electromagnetic compatibility between antennas located on a plane, the behaviors of the electromagnetic field along the impedance structure are investigated. The method of moments is used to solve the integral equations and the numerical results are presented and analyzed. To reduce coupling between antennas, we need to take into account both the amplitude distribution of the field along the structure and in the openings of the antennas. In addition, while designing the structure, it is necessary to control the coefficient of decoupling.

摘要：The low cycle fatigue behavior of zirconium−titanium−steel composite plate under symmetrical and asymmetric stress control was *** effects of mean stress and stress amplitude on cyclic deformation,ratcheting effect and damage mechanism were discussed in *** results show that under symmetric stress control,the forward ratcheting deformation is *** asymmetric stress control,the ratcheting strain increases rapidly with mean stress and stress amplitude *** high stress amplitude,the influence of mean stress is more *** addition,by studying the variation of strain energy density,it is found that the stress amplitude mainly promotes the fatigue damage,while the mean stress leads to the ratcheting *** addition,fractographic observation shows that the crack initiates in the brittle metal compound at the interface,and the steel has higher resistance to crack ***,the accuracy of life prediction model considering ratcheting effect is discussed in detail,and a high-precision life prediction model directly based on mean stress and stress amplitude is proposed.

摘要：生源物质作为影响水质的重要因素,其在河流中的迁移转换一直倍受关注。水沙界面物质交换过程受众多环境和水动力因素的影响,过程极其复杂,不仅影响着河流生源要素的通量演变规律,还关系到河流水环境问题。为探究水沙界面生源物质迁移转化过程及作用机制,结合国内外研究最新进展,对泥沙颗粒与生源物质的微界面作用、水沙界面对生源物质的迁移转化作用、水流条件对泥沙吸附解吸生源物质作用机理进行总结和概述,总结阐述了河流水质模型和闸坝泵条件下的水环境调控模型,最后指出平原河流水沙运动对生源物质输运作用机理及水环境调控。针对上述已有的研究成果和存在不足,对今后研究方向提出展望。