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Wire thermal spraying, one of the significant coating preparation technologies in the field of thermal spraying, has the advantages of low cost, high material utilization rate and fast coating deposition. Powder-cored wires, with easily controllable compositions, are used as spraying materials to prepare functional coatings with special properties. Coatings prepared by traditional wire thermal spraying technologies, mainly including wire flame spraying (WFS), wire arc spraying (WAS) and plasma wire spraying, have some defects, such as weak bonding strength and high porosity. In this paper, the plasma transferred wire arc spraying (PTWAS) technology was innovatively proposed, by which Al/SiC powder-cored wires were successfully sprayed to deposit the aluminum (Al)/Nicalon (SiC) composite coating. Furthermore, the influences of spraying current (I), argon (Ar) flow rate (LAr), hydrogen (H2) flow rate (LH2) and other factors on Al/Sic powder-cored wires prepared by PTWAS and the optimization of the coating preparation process were mainly studied via the single factor method and the response surface methodology. After experimental exploration and analysis, the optimized process parameters were finally determined as follows: LAr was 120 L min−1, I was 160 A, LH2 was 5 L min−1, the spraying distance was 100 mm, the wire feeding speed (V) was 0.18 m s−1, and the distance between the wire and nozzle (d) was 10 mm. It was found in the test that the porosity of the optimized Al/SiC composite coating was only 1.6%, the average microhardness was 102 HV0.1, and the average bonding strength was 36.5 MPa. The comprehensive properties of this coating were better than those of the Al/SiC composite coatings prepared by WFS and WAS. [ABSTRACT FROM AUTHOR]

As rigid robots suffer from the higher inertia of their rigid links, cable-driven parallel robots (CDPRs) are more suitable for large-scale three-dimensional (3D) printing tasks due to their outstanding reconfigurability, high load-to-weight ratio, and extensive workspace. In this paper, a parallel 3D printing robot is proposed, comprising three pairs of driving cables to control the platform motion and three pairs of redundant cables to adjust the cable tension. To improve the motion accuracy of the moving platform, the static kinematic error model is established, and the error sensitivity coefficient is determined to reduce the dimensionality of the optimization function. Subsequently, the self-calibration positions are determined based on the maximum cable length error in the reachable workspace. A self-calibration method is proposed based on the genetic algorithm to solve the kinematic parameter deviations. Additionally, the dynamic errors are effectively reduced by compensating for the elastic deformation errors of the cable lengths. Furthermore, an experimental prototype is developed. The results of dynamic error compensation after the self-calibration indicate a 67.4% reduction in terms of the maximum error along the Z-axis direction. Finally, the developed prototype and proposed calibration and compensation methods are validated through the printing experiment. [ABSTRACT FROM AUTHOR]

Compared to traditional plasma cladding technology, plasma spray melting technology is characterized by a small heat-affected zone and high processing speed, and has a high application value. However, the process still faces significant problems, such as inaccurate parameters and work points and feasibility that need to be investigated. This study discusses a two-dimensional (2D) model of the plasma spray melting process to provide a theoretical basis for determining the optimal process parameters. The spray melting process was studied in depth by considering the cooling effect of gas convection on the melting pool, as well as by the analysis of thermal cycling and thermal diffusion of the matrix. Finally, the reliability of the model was validated by a Ni60 coating with micro-metallurgical bonding characteristics, which was spray melted onto the surface of a Q235 steel matrix. Due to its characteristics of low power, fast heating, and fast cooling, plasma spray melting technology can be used to prepare various thin coatings with micro-metallurgical bonding on the die surface, so as to significantly improve the bonding strength of the coating and mitigate the influence of the heat of the spray melting process on the die, thereby improving the material performance. [ABSTRACT FROM AUTHOR]

High-frequency current transformer (HFCT) sensors are widely used in pulse detection at high frequencies. The sensitivity of the HFCT needs to be improved for low-level pulse detection at high frequencies because their waveforms can rapidly attenuate and disperse. This research shows that refining the ferrites of the magnetic cores can improve their permeability at high frequencies. We employed a two-step sintering technique to refine the nickel-copper-zinc (Ni-Cu-Zn) ferrites by adding barium titanate (BaTiO3). The contribution of the spin rotation to the magnetization was thereby improved. As a result, the transfer functions of the HFCT sensors made from the refined ferrites were improved, significantly improving their sensitivity for pulse detection at high frequencies. [ABSTRACT FROM AUTHOR]

Iron-based anodes for lithium-ion batteries (LIBs) with higher theoretical capacity, natural abundance and cheapness have received considerable attention, but they still suffer from the fast capacity fading. To address this issue, we report a facile synthesis of plate-like carbon-supported Fe3C nanoparticles through chemical blowing/carbonization under calcination. The ultrafine Fe3C nanoparticles are prone to be oxidized when exposing in air; thus, Fe3C/C with mild oxidization and the fully oxidized product of Fe2O3/C are successfully prepared by controlling the oxidization condition. When applied as an anode material in LIB, the Fe3C/C electrode demonstrates excellent cycle stability (826 mAh·g−1 after 120 cycles under 500 mA·g−1) and rate performance (410.6 mAh·g−1 under 2 A·g−1), compared with the Fe2O3/C counterpart. The enhanced electrochemical performance can be ascribed to the synergetic effect of the Fe3C with mild oxidation and the unique hierarchical structure of plate-like carbon decorated with Fe3C catalyst. More importantly, this work may offer new approaches to synthesize other transition metal (e.g., Co, Ni)-based anode material by replacing the precursor ingredient. [ABSTRACT FROM AUTHOR]

To avoid impacts and vibrations during the processes of acceleration and deceleration while possessing flexible working ways for cable-suspended parallel robots (CSPRs), point-to-point trajectory planning demands an under-constrained cable-suspended parallel robot (UCPR) with variable angle and height cable mast as described in this paper. The end-effector of the UCPR with three cables can achieve three translational degrees of freedom (DOFs). The inverse kinematic and dynamic modeling of the UCPR considering the angle and height of cable mast are completed. The motion trajectory of the end-effector comprising six segments is given. The connection points of the trajectory segments (except for point P3 in the X direction) are devised to have zero instantaneous velocities, which ensure that the acceleration has continuity and the planned acceleration curve achieves smooth transition. The trajectory is respectively planned using three algebraic methods, including fifth degree polynomial, cycloid trajectory, and double-S velocity curve. The results indicate that the trajectory planned by fifth degree polynomial method is much closer to the given trajectory of the end-effector. Numerical simulation and experiments are accomplished for the given trajectory based on fifth degree polynomial planning. At the points where the velocity suddenly changes, the length and tension variation curves of the planned and unplanned three cables are compared and analyzed. The OptiTrack motion capture system is adopted to track the end-effector of the UCPR during the experiment. The effectiveness and feasibility of fifth degree polynomial planning are validated. [ABSTRACT FROM AUTHOR]

Deterministic kinematic modeling and stochastic luffing angular response field prediction of the dual automobile cranes system (DACS) are studied in this paper. For the response analysis of the DACS with deterministic information, the inverse kinematics are analyzed. For the prediction of luffing angular response field of the DACS with narrowly random payload parameters, a narrowly random model is introduced. In the narrowly random model, the payload parameters with certain probability distribution are modeled as random variables. Based on the narrowly random model, the equilibrium equation of luffing angular response vector of the DACS with random parameters is derived. Then a perturbation-based random composite function method (PRCFM) is proposed. Based on the PRCFM, the first-order Neumann series expansion and the proposed random variable functional moment method, a modified hybrid random method (MHRM) for the luffing angular response field prediction of the DACS with narrowly random payload parameters is proposed. In the MHRM, the statistical characteristics of luffing angular response vector are determined. Numerical results show the feasibility and efficiency of the MHRM for solving the narrowly stochastic DACS problems compared with the Monte Carlo method. The effects of different random parameters (y, z, θ) on the DACS luffing angular response field are also investigated deeply, and numerical results indicate the impact on the variances made by the randomness in the random payload parameter y is larger than those made by random payload parameters z and θ. [ABSTRACT FROM AUTHOR]

Unbalance is an inevitable issue in rotating machineries due to the manufacturing tolerances, the assembly errors, the damage in rotating components, etc. The effects of unbalance on the nonlinear dynamics of cracked rotors are investigated in this paper. In order to overcome the assumption of weight dominance, 3D finite element models are employed to discretize the rotor and several contact pairs are defined on the cracked surfaces to simulate the intermittent breathing behavior of crack. Then, the complex free interface component mode synthesis method (CMS) is employed to reduce the model’s order and to increase the computational efficiency. Finally, the obtained models are used to study the effects of concentrated and distributed unbalances on the nonlinear dynamic response of cracked rotors. The results show that the unbalance can significantly affect the breathing mechanism of crack and consequently dramatically change the rotor’s dynamic behaviors. Moreover, the different levels and orientations of unbalance lead to obviously different results. Besides, the responses of rotors with two asymmetric distributed unbalance are similar to those of rotors with a single concentrated unbalance though the rotors are overall balanced. [ABSTRACT FROM AUTHOR]

This paper develops a dynamics-based nonsingular interval model and proposes a first-order composite function interval perturbation method (FCFIPM) for luffing angular response field analysis of the dual automobile cranes system (DACS) with narrowly bounded uncertainty. By using the nonsingular interval model to describe a structure parameter with bounded uncertainty, the reasonable lower and upper bounds can be obtained, which is quite different from the traditional interval model with approximate bounds only from a large number of samples. Firstly, for the DACS with deterministic information, the inverse kinematics is analyzed, and the dynamic model of the DACS is established based on the virtual work principle and the inverse kinematics. Secondly, considering the nonsingularity of the dynamic response curves, a dynamics-based nonsingular interval model is introduced. Based on the nonsingular interval model, the interval luffing angular response vector equilibrium equation of the DACS is established. Thirdly, a first-order composite function interval perturbation method is proposed. In the FCFIPM, the composite function vectors are expanded by using the first-order Taylor series expansion, based on the differential property of composite function and monotonic analysis technique, the lower and upper bounds of the interval luffing angular response vector of the crane 1 and crane 2 of the DACS are determined. The first case is to investigate the deterministic kinematics and dynamics of the DACS with a given trajectory. The second case is provided to illustrate the detailed implementation process of constructing a dynamics-based nonsingular interval model. Finally, some numerical examples are given to verify the feasibility and efficiency of the FCFIPM for solving the luffing angular response field problem with narrowly interval parameters. [ABSTRACT FROM AUTHOR]

A series of oedometer test were performed on both undisturbed and remolded specimens of Wenzhou marine clay to quantitatively investigate the degradation of soil structure during compression. The laboratory tests show that the swell index of both natural and remolded Wenzhou marine clay increase with the increase in consolidation stress. Hence, the normalizing parameter 'swell sensitivity', termed as the ratio of the remolded to the natural swelling index, can only be regarded as a qualitative parameter. On the other hand, the normalized stress sensitivity has a good parabolic relationship with the consolidation stress during destructuration. This result indicates that the stress sensitivity can be used as a quantitative interpretation of the degradation of soil structure for natural Wenzhou marine clay. Comparison between stress sensitivity and additional void ratio during destructuration shows that the variation of soil structure during destructuration represented by stress sensitivity and additional void ratio are essentially the same. In addition, the parameter used in formulating the variation of stress sensitivity with the stress level is correlated with natural void ratio and void ratio at liquid limit. [ABSTRACT FROM AUTHOR]

With the experience of successfully developing the 20-inch MCP-PMT (LPMT), the MCP-PMT group in China is now focusing on the R&D of small-sized fast MCP-PMT (FPMT) with time resolution on the order of tens of picoseconds. By now, the single-anode, anodes, anodes and anodes FPMT prototypes have been produced by the cooperation company and evaluated in the PMT Lab in IHEP. The best transit time resolution (TTS) for the anodes FPMT can reach 47 ps for single photoelectron and 16 ps for multi photoelectrons. [ABSTRACT FROM AUTHOR]

This paper addresses the dynamics and trajectory tracking control of cooperative multiple mobile cranes. Compared with a single mobile crane, cooperative cable parallel manipulators for multiple mobile cranes (CPMMC) are more complex in configuration, which have the characters of both series and parallel manipulators. Therefore, for the CPMMC, the forward as well as the inverse kinematics and dynamics include the difficulties of both series and parallel manipulators. However, the closed kinematic chain brings about potential benefits, including sufficient accuracy, higher cost performance, better lifting capacity and security. Firstly, the forward and inverse kinematics of the CPMMC with point mass are derived with elimination method, and the complete dynamic model of the CPMMC is established based on Lagrange equation and the complete kinematics. Secondly, considering the repetitive tasks and high security and precision requirement, a robust iterative learning controller is designed for trajectory tracking on the basis of the linearization of the dynamics. Thirdly, taking the engineering practice into consideration, two case studies are simulated with the same expected trajectory but with different weights of the loads. Finally, the designed controller is compared with traditional PD control algorithm via numerical simulation. The results demonstrate the feasibility and superiority of the CPMMC and designed controller, and provide a theoretical basis for the cooperation of multiple mobile cranes. [ABSTRACT FROM AUTHOR]

The observations on compressibility of reconstituted clays show that the compression line with a higher initial water content lies above the compression line with a lower initial water content for a given clay. Hence there exists additional void ratio due to initial water contents among virgin compression lines (VCLs) of reconstituted clays. In this paper, the difference in void ratio caused by different initial water contents is investigated based on the empirical equation proposed by Liu and Carter (2000) for describing the differential void ratio at the same stress between natural and reconstituted clays. The mechanism of compressibility of reconstituted clays, when the stress level is larger than the remolded yield stress, is also discussed. [ABSTRACT FROM AUTHOR]

Combining mobile cranes with the cable parallel manipulators (CPMs), a cooperative CPMs for multiple mobile cranes (CPMMCs) was designed in this paper. The kinematics were derived on the basis of the configuration of the CPMMCs, aiming at numerical estimation of workspace subject to the constraints on the cable tensions and mobile cranes' structure. Kinematic error, caused by machining, assembly and operation, is one of the major error sources for CPMMCs during high-precision hoisting, which can be estimated by means of error modeling. Kinematics error model was established based on closed-loop vector method. The influences of different error sources on the accuracy are investigated with sensitivity analysis in statistics. Finally, the system is simulated with expected trajectory of the payload based on the established kinematics and error model of the CPMMCs. The simulation results not only provide rationale for design of the CPMMCs, but also of certain guiding significance in practical engineering application. [ABSTRACT FROM AUTHOR]

Cable-driven parallel robots (CDPRs) are categorized as a type of parallel manipulators. In CDPRs, flexible cables are used to take the place of rigid links. The particular property of cables provides CDPRs several advantages, including larger workspaces, higher payload-to-weight ratio and lower manufacturing costs rather than rigid-link robots. In this paper, the history of the development of CDPRs is introduced and several successful latest application cases of CDPRs are presented. The theory development of CDPRs is introduced focusing on design, performance analysis and control theory. Research on CDPRs gains wide attention and is highly motivated by the modern engineering demand for large load capacity and workspace. A number of exciting advances in CDPRs are summarized in this paper since it is proposed in the 1980s, which points to a fruitful future both in theory and application. In order to meet the increasing requirements of robot in different areas, future steps foresee more in-depth research and extension applications of CDPRs including intelligent control, composite materials, integrated and reconfigurable design. [ABSTRACT FROM AUTHOR]

The His-x-Asp (HxD) motif is one of the most conserved structural components of the catalytic core of protein kinases; however, the functional role of the conserved histidine is unclear. Here we report that replacement of the HxD-histidine with Arginine or Phenylalanine in Aurora A abolishes both the catalytic activity and auto-phosphorylation, whereas the Histidine-to-tyrosine impairs the catalytic activity without affecting its auto-phosphorylation. Comparisons of the crystal structures of wild-type (WT) and mutant Aurora A demonstrate that the impairment of the kinase activity is accounted for by (1) disruption of the regulatory spine in the His-to-Arg mutant, and (2) change in the geometry of backbones of the Asp-Phe-Gly (DFG) motif and the DFG-1 residue in the His-to-Tyr mutant. In addition, bioinformatics analyses show that the HxD-histidine is a mutational hotspot in tumor tissues. Moreover, the H174R mutation of the HxD-histidine, in the tumor suppressor LKB1 abrogates the inhibition of anchorage-independent growth of A549 cells by WT LKB1. Based on these data, we propose that the HxD-histidine is involved in a conserved inflexible organization of the catalytic core that is required for the kinase activity. Mutation of the HxD-histidine may also be involved in the pathogenesis of some diseases including cancer. [ABSTRACT FROM AUTHOR]