摘要：In order to improve the strength and stiffness of shield cutterhead, the method of fuzzy mathematics theory in combination with the finite element analysis is adopted. An optimal design model of structural parameters for shield cutterhead is formulated,based on the complex engineering technical requirements. In the model, as the objective function of the model is a composite function of the strength and stiffness, the response surface method is applied to formulate the approximate function of objective function in order to reduce the solution scale of optimal problem. A multi-objective genetic algorithm is used to solve the cutterhead structure design problem and the change rule of the stress-strain with various structural parameters as well as their optimal values were researched under specific geological conditions. The results show that compared with original cutterhead structure scheme, the obtained optimal scheme of the cutterhead structure can greatly improve the strength and stiffness of the cutterhead, which can be seen from the reduction of its maximum equivalent stress by 21.2%, that of its maximum deformation by 0.75%, and that of its mass by 1.04%.

摘要：A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is *** assumes that the motion of all clutch components can be expressed by a model of epicyclic *** takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races,and it can be used for optimization of design and comparison with other types of sprag clutches.A good deal of analysis shows that the parameters of the steady windup angle,the steady contact force,the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race,while the parameters of the maximum transient windup angle,the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of *** is also shown that the strut angle has great influence on the dynamic engagement performance of *** parameters of the steady windup angle,the maximum transient windup angle,the steady engaging time,the steady contact force,the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle,while the natural frequency of the system increases linearly with the inner strut angle.

摘要：This paper proposes a novel underactuated finger mechanism based on a motion coupling and shape-adaptive linkage design that combines anthropomorphic free motion and adaptive grasping. The proposed three-joint finger mechanism with one active Degree of Freedom （DOF） consists of a five-linkage meehanism in the proximal phalanx and a mechanism comprising two parallel planar four-bar linkages in the middle phalanx. The respective mechanism allows the simultaneously rotation of their corresponding pha- langes in the plane before making contact with an object, and can fully envelop an object, even if certain phalanges are blocked. The duel parallel four-bar linkage mechanism is adopted to improve the grasping capacity of the distal phalanx. An optimal design of the finger is presented according to anthropomorphic phalanx trajectories and maximized grasping forces obtained with consideration for the angular velocity relationships of the three phalanges and their force transmission performances. The functionality of the proposed finger mechanism is verified through multiple simulations and grasping experiments using a prototype finger.

摘要：As two promising biomaterials for bone implants,biomedical metals have favorable mechanical properties and good machinability but lack of bioactivity;while bioceramics are known for good biocompatibility or even bioactivity but limited by their high ***,a kind of composites composing of bioceramics and biomedical metals,have been developed as an effective solution by combining their complementary *** paper focused on the recently studied biocermets for bone implant ***,biocermets were divided into ceramic-based biocermets and metal-based biocermets according to the phase *** characteristics were systematically summarized,and the fabrication methods for biocermets were reviewed and *** were put on the interactions between bioceramics and biomedical metals,as well as the performance improvement *** importantly,the main methods for the interfacial reinforcing were summarized,and the corresponding interfacial reinforcing mechanisms were *** addition,the in vitro and in vivo biological performances of biocermets were also ***,future research directions were proposed on the advancement in component design,interfacial reinforcing and forming mechanisms for the fabrication of high-performance biocermets.

摘要：Hydroxyapatite(HA)nanoparticles and silver(Ag)nanoparticles are expected to enable desirable bioactivity and antibac-terial properties on biopolymer ***,interfacial adhesion between HA/Ag and the biopolymer is poor due to the large physicochemical differences between these *** this study,poly L-lactic acid(PLLA)powder was first surface-modified with bioactive polydopamine(PDA)in an alkaline ***,HA and Ag nanoparticles were grown in situ on the PDA-coated PLLA powder,which was then adhered to the porous bone scaffold using a selective laser-sintering *** showed that HA and Ag nanoparticles were homogenously distributed in the matrix,with enhanced mechanical *** body fluid bioactivity tests showed that the in situ grown HA-endowed scaffold shows excellent *** vitro tests confirmed that the scaffold exhibits favorable biocompatibility with human umbilical cord mesenchymal stem cells,as well as strong antibacterial activity against Gram-negative Escherichia ***,in vivo assays indicated that the scaffold promoted bone generation,with a new bone area fraction of 71.8%after 8 weeks’implantation,without inflammation.

摘要：The layout of the buckets for tunnel boring machine(TBM)directly affects the muck removal efficiency of cutterhead during *** order to improve the muck removal performance for TBM,the optimal design of bucket layout was *** whole muck transfer process was simulated by discrete-element method(DEM),including the muck falling,colliding,pilling up,shoveling and transferring into the *** muck model was established based on size distribution analysis of muck samples from the water-supply tunnel project in Jilin Province,***,the influence of the bucket number and the interval angle between buckets on muck removal performance was *** results indicated that,as the number of buckets increased from four to eight,the removed muck increased by 29%and the residual volume decreased by 40.5%,and the process became *** interval angles between buckets were corresponding to different removed muck irregularly,but the residual muck number increased generally with the *** optimal layout of buckets for the cutterhead in this tunnel project was obtained based on the simulation results,and the muck removal performance of the TBM was verified by the actual data in the engineering construction.

摘要：The preparation of superhydrophobic or underwater superoleophobic interface materials has become a research hotspot because of their wide application in self-cleaning, drag reduction, oil-water separation, anti-oil pollution and so on. The unique wettability of organisms gives inspiration to design and create new interface materials. This review focuses on the recent research progress of femtosecond laser micro/nano fabrication for bioinspired superhydrophobic or underwater superoleophobic surfaces. This review starts with a presentation of the related background including the advantages of femtosecond laser and wettability theoretical basis. Then, organisms with unique wettability in nature, the preparation of superhydrophobic or underwater superoleophobic surfaces by femtosecond lasers on different materials, and their related important applications are introduced. Finally, the current challenges and future prospects with regard to this field are provided.

摘要：A new consistency control method for jet dispensing is proposed. First, the working parameters, namely, viscosity, supply pressure and supply time, are experimentally investigated. Then, the glue viscosity is approximated by a polynomial model using the least square method. Based on this model and temperatme control implemented using the Dahlin principle, the viscosity of the glue can be maintained at a constant value. Then, the viscosity model of the glue is applied to deriving the droplet mass as the nominal model of the temperature controller. The robustness of the temperature controller is analyzed by applying the small gain theory. The glue supply pressure controller is designed using the consistency control strategy, and the robustness is analyzed. Finall）, simulations and experiments are conducted using a jet dispensing control system. The results show that the proposed control strategy can significantly improve the droplet consistency.

摘要：Laser powder bed fusion(LPBF)makes it possible for biodegradable zinc(Zn)to be used to produce customized orthopedic *** this research,we investigate the impact of laser power and scanning speed on the development of surface quality,relative densification,and texture during LPBF of Zn *** laser power was able to decrease melt viscosity and surface tension,which improved the metallurgical bonding between adjacent *** and twisted tracks also became continuous and *** speed could controlmolten-pool temperature to restrain grain natural orientation,achieving various crystal orientations and a weakened ***,it further avoided the thermal expansion and contraction caused by excessive energy storage and accumulation in the matrix,thus reducing the generation of high-dislocation *** a result,by selecting a reasonable laser power and scanning speed,the LPBF parts exhibited a flat surface morphology and a high density over 99.5%.Their average hardness,mechanical strength,and elongation reached 50.2 HV,127.8 MPa,and 7.6%,***,the parts displayed a moderate degradation rate and excellent osteogenic *** these results provide a basis for selecting process parameters to optimize the comprehensive properties of LPBF-processed Zn parts for biodegradable applications.

摘要：磁通反馈式功率放大器中存在的噪声、参数摄动以及其它非线性特征会影响磁悬浮效果。为了研究该问题,建立了磁通反馈式功率放大器及其负载电磁铁的仿真模型,其中引入了气隙变化对磁通生成模型的影响。针对单纯比例积分微分（proportion-integral-differential,PID）控制应用在磁通反馈式功率放大器中会产生磁通稳态输出抖动的问题,设计了一个新型干扰观测器（disturbance observer,DOB）。新型DOB采用多路传感信号综合观测的方式减小反馈信号处的噪声干扰对观测值的影响,并获得了比常规DOB更加稳定的系统等效效果。仿真结果表明,结合新型DOB结构的PID反馈控制方法能够很好的抑制因模型参数摄动、模型非线性特征和噪声而造成的稳态磁通输出抖动,其控制效果优于单独PID控制方法。