A Synthetic Algorithm for Tracking a Moving Object in a Multiple-Dynamic Obstacles Environment Based on Kinematically Planar Redundant Manipulators

This paper presents a synthetic algorithm for tracking a moving object in a multiple-dynamic obstacles environment based on kinematically planar manipulators. By observing the motions of the object and obstacles, Spline filter associated with polynomial fitting is utilized to predict their moving paths for a period of time in the future. Several feasible paths for the manipulator in Cartesian space can be planned according to the predicted moving paths and the defined feasibility criterion. The shortest one among these feasible paths is selected as the optimized path. Then the real-time path along the optimized path is planned for the manipulator to track the moving object in real-time. To improve the convergence rate of tracking, a virtual controller based on PD controller is designed to adaptively adjust the real-time path. In the process of tracking, the null space of inverse kinematic and the local rotation coordinate method (LRCM) are utilized for the arms and the end-effector to avoid obstacles, respectively. Finally, the moving object in a multiple-dynamic obstacles environment is thus tracked via real-time updating the joint angles of manipulator according to the iterative method. Simulation results show that the proposed algorithm is feasible to track a moving object in a multiple-dynamic obstacles environment

Tribute to the Market City, Service to the Market

I was a military man who is now unexpectedly in charge of the largest small-commodities market in Yiwu and even the whole country ⦠[several sentences omitted].

On the comparison of properties of Rayleigh waves in elastic and viscoelastic media

Dispersion properties of Rayleigh‐type surface waves can be used for imaging and characterizing the shallow subsurface. This paper uses the time‐domain finite difference method on the Rotated staggered grid to simulates Rayleigh waves in complex viscoelastic media. The second‐order displacement‐stress viscoelastic wave equations are used in the computational domain and the unsplit convolutional perfectly matched layer is used as the absorbing boundary condition. The elastic wave‐fields in a two‐layer model is simulated to prove the correctness of this scheme. The viscoelastic Rayleigh waves are calculated and the dispersion properties are analyzed. The dispersion curve changes with different values of quality factor Q in the media and higher modes of Rayleigh waves are generated and possess significant amounts of energy with strong attenuation.NSERCYesIndustrial consortium in Reservoir Simulation and Modelling; Foundation CMG; Alberta Innovates

3D structure fungi-derived carbon stabilized stearic acid as a composite phase change material for thermal energy storage

Stearic acid (SA)/fungi-derived carbon (FDC) composite phase change materials (PCM) were fabricated by vacuum impregnation, where three types of FDC (FDC-C, FDC-H, and FDC-K) as carrier were synthesized by diverse synthetic procedures of carbonization. The FDC-K modified by synergistic hydrothermal and KOH-assisted calcination process had a 3D-cellular structure with considerably higher inner surface area (1799.48 m2 g−1) and cumulative pore volume (0.7476 cm3 g−1) than other matrixes, leading to that a loading capability value of SA (LC, %) in SA/FDC-K composite was up to 344.64%. X-ray diffraction and Fourier transform infrared spectroscopy shown that physical interaction instead of chemical reaction happened between FDC and SA. X-ray photoelectron spectroscopy indicated that KOH-assisted calcination treatment improved oxygenic functional groups on matrix surface so that facilitating SA loading. Raman spectra illustrated the IG/ID value of three amorphous carbons were ∼1.04. For SA/FDC-K composite, it had a melting and freezing enthalpy of 144.8 J g−1 and 142.6 J g−1, respectively, and phase transition point of 52.72 °C and 52.95 °C, respectively. The thermal conductivity (0.574 W m−1 K−1) was 115% higher than pure SA. It was also stable in terms of thermal and chemical after thermal cycles in heating and cooling. Thus, the SA/FDC-K exhibited high phase transition enthalpy and excellent thermal stability has potential application in thermal energy storage.This work was supported by the National Natural Science Foundation of China (51874047, 51504041); the Training Program for Excellent Young Innovators of Changsha (kq1802007); the Fund for University Young Core Instructors of Hunan Province; the Natural Science Foundation of Hunan Province (2016JJ3009); and the Hunan Province 2011 Collaborative Innovation Center of Clean Energy and Smart Grid

First-order decoupled method of the three-dimensional primitive equations of the ocean

This paper is concerned with a first-order fully discrete decoupled method for solving the three-dimensional (3D) primitive equations of the ocean with the Dirichlet boundary conditions on the side, where a decoupled semi-implicit scheme is used for the time discretization, and the $P_1(P_1)-P_1-P_1(P_1)$ finite element for velocity, pressure, and density is used for the spatial discretization of these equations. The $H^1-L^2-H^1$ optimal error estimates for the numerical solution $(u_h^n,p_h^n,\theta_h^n)$ and the $L^2$ optimal error estimate for $(u^n_h,\theta_h^n)$ are established under the restriction of $0<h\le \beta_1$ and $0<\tau\le \beta_2$ for some positive constants $\beta_1$ and $\beta_2$. Moreover, numerical investigations are provided to show that the first-order decoupled method is of almost unconditional convergence with accuracy $\mathcal{O}(h+\tau)$ in the $H^1$-norm and $\mathcal{O}(h^2+\tau)$ in the $L^2$-norm for solving the 3D primitive equations of the ocean. Numerical results are given to verify the theoretical analysis.NSERCYesIndustrial consortium in Reservoir Simulation and Modelling; Foundation CMG; Alberta Innovates

Compressive Rheological Behavior and Microstructure Evolution of a Semi-Solid CuSn10P1 Alloy at Medium Temperature and Low Strain

Copper&ndash;tin alloys are widely used in the machining and molding of sleeves, bearings, bearing housings, gears, etc. They are a material used in heavy-duty, high-speed and high-temperature situations and subject to strong friction conditions due to their high strength, high modulus of elasticity, low coefficient of friction and good wear and corrosion resistance. Although copper&ndash;tin alloys are excellent materials, a higher performance of mechanical parts is required under extreme operating conditions. Plastic deformation is an effective way to improve the overall performance of a workpiece. In this study, medium-temperature compression tests were performed on a semi-solid CuSn10P1 alloy using a Gleeble 1500D testing machine at different temperatures (350&minus;440 &deg;C) and strain rates (0.1&minus;10 s&minus;1) to obtain its medium-temperature deformation characteristics. The experimental results show that the filamentary deformation marks appearing during the deformation are not single twins or slip lines, but a mixture of dislocations, stacking faults and twins. Within the experimental parameters, the filamentary deformation marks increase with increasing strain and decrease with increasing temperature. Twinning subdivides the grains into lamellar sheets, and dislocation aggregates are found near the twinning boundaries. The results of this study are expected to make a theoretical contribution to the forming of copper&ndash;tin alloys in post-processing processes such as rolling and forging

Synergistic Catalysis of SnO2/Reduced Graphene Oxide for VO2+/VO2+ and V2+/V3+ Redox Reactions

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO2/reduced graphene oxide (SnO2/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO2/rGO shows better electrochemical catalysis for both redox reactions of VO2+/VO2+ and V2+/V3+ couples as compared to SnO2 and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO2 has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO2/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm−2, the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions

Rapid flattening of massive hemorrhagic retinal pigment epithelial detachment secondary to polypoidal choroidal vasculopathy after surgery

Purpose: To report 2 polypoidal choroidal vasculopathy (PCV) patients whose massive hemorrhagic pigment epithelial detachments (PEDs) were flattened within a short period after surgery. Observations: Two PCV patients who presented with submacular hemorrhage and massive hemorrhagic PEDs with sizes of more than 50 disc areas underwent pars plana vitrectomy combined with subretinal injection of tissue plasminogen activator (tPA), intravitreous injection of anti-vascular endothelial growth factor medicine, and perfluoropropane tamponade. The massive hemorrhagic PEDs were flattened within a short period after both surgeries, and both patients experienced improved visual acuity. Conclusions: These findings suggest that subretinal injection of tPA together with perfluoropropane tamponade promotes the rapid clearance of hemorrhage under RPE

Compressive Rheological Behavior and Microstructure Evolution of a Semi-Solid CuSn10P1 Alloy at Medium Temperature and Low Strain

Copper–tin alloys are widely used in the machining and molding of sleeves, bearings, bearing housings, gears, etc. They are a material used in heavy-duty, high-speed and high-temperature situations and subject to strong friction conditions due to their high strength, high modulus of elasticity, low coefficient of friction and good wear and corrosion resistance. Although copper–tin alloys are excellent materials, a higher performance of mechanical parts is required under extreme operating conditions. Plastic deformation is an effective way to improve the overall performance of a workpiece. In this study, medium-temperature compression tests were performed on a semi-solid CuSn10P1 alloy using a Gleeble 1500D testing machine at different temperatures (350−440 °C) and strain rates (0.1−10 s−1) to obtain its medium-temperature deformation characteristics. The experimental results show that the filamentary deformation marks appearing during the deformation are not single twins or slip lines, but a mixture of dislocations, stacking faults and twins. Within the experimental parameters, the filamentary deformation marks increase with increasing strain and decrease with increasing temperature. Twinning subdivides the grains into lamellar sheets, and dislocation aggregates are found near the twinning boundaries. The results of this study are expected to make a theoretical contribution to the forming of copper–tin alloys in post-processing processes such as rolling and forging

Emerging mineral-coupled composite phase change materials for thermal energy storage

A mineral-coupled support, flake graphite-carbon nanofiber-modified bentonite, was used to stabilize stearic acid for constructing form-stable phase change material composites. In order to achieve a synergistic improvement of thermal conductivity and loading space, the supporting material was prepared by growing carbon nanofiber on flake graphite surface through chemical vapor deposition technique and then chemically bonding with modified bentonite. The effect of coupling behavior on interfacial thermal resistance was investigated and results show that the thermal conductivity of the coupled supporting material (4.595 W m−1 K−1) is higher than that of non-coupled support (4.291 W m−1 K−1), proving chemical bonding can decrease interface thermal resistance at a certain extent. The performances of composites were further explored, which indicates the obtained composite base on coupled support possesses good chemical compatibility, and great thermal stability under 180 °C. It also shows that this composite with 41.90% loading capability has latent heat value of 79.13 J g−1 for melting and 79.13 J g−1 for freezing, respectively. After 50 heating-cooling cycles, the variation of melting latent heat was within 0.05%, exhibiting a great thermal reliability. Besides, thermal conductivity of this composite is 10.50 times higher than that of pure phase change material, resulting in more rapid heat transfer efficiency, and excellent transient temperature response recorded by thermal infrared images. In all, the composite is a potential candidate for thermal storage applications due to larger latent heat capability and considerable thermal conductivity.This work was supported by the National Natural Science Foundation of China, China (51504041, 51874047); the Training Program for Excellent Young Innovators of Changsha (kq1802007); the Fund for University Young Core Instructors of Hunan Province, China; the Natural Science Foundation of Hunan Province (2016JJ3009); the Key Research and Development Program of Jiangxi Province, China (20171BBH80021); and the Hunan Province 2011 Collaborative Innovation Center of Clean Energy and Smart Grid