This paper conducts research on collision and obstacle avoidance of multi-agent systems without mapping ability, while the constrained agent can only detect obstacles within a limited distance, then ...a velocity programing strategy is proposed considering the lack of a high-resolution map and the challenge of the modeling of complex obstacles. Based on the detecting information of nearby members and obstacles, a discontinuous velocity programing space is constructed by imposing the constraints on the velocity. To obtain expansive programing space, two different ways are utilized to establish the velocity constraints of avoiding various obstacles. For obstacles that can be viewed as virtual circular obstacles, a barrier function is introduced to restrict the radial component of the velocity. As for the obstacle that can only be detected partially, we use the border lines to construct a velocity feasible domain, and the domain is approximated by the polygonal region using the convex theory. Then, the nominal velocity is utilized as the objective and a nonlinear dynamic programing regulator is proposed. Furtherly, velocity limits generated from the system kinematic constraints are incorporated into the regulator. Finally, three tests are carried out and the feasibility of the proposed regulator is verified.
Previously, it was found that reduced graphene oxide (RGO) can degrade rhodamine B (RhB) under visible‐light irradiation, but with an extraordinarily slow rate. It was also found that modification of ...RGO with gold nanoparticles can dramatically accelerate the photoreaction rate. Herein, we describe the preparation and photocatalytic properties of copper‐ion‐modified RGO composite materials, which display a faster photocatalytic reaction rate and better mineralization under visible‐light irradiation than gold‐modified RGO. The copper‐ion‐modified RGO composites were prepared by an immersion method. The characterization results of X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy, and X‐ray photoelectron spectroscopy show the presence of crystalline copper species Cu2(OH)3NO3 and Cu2(OH)3Cl on the surface of RGO. Modification of RGO with the copper species greatly enhances the degradation of RhB—after 3 hours of reaction under visible‐light irradiation, the total organic carbon is decreased by about 31 %. The copper species act as an electron relay, passing the excited electrons from the RGO sheets to adsorbed oxygen, thus leading to continuous generation of reactive oxygen species for the degradation of RhB.
Dyeing out: An approach to modifying graphene to prepare optically active photocatalysts is presented. The reduced graphene oxide (RGO)‐based composite materials display excellent photocatalytic performance in degrading the dye rhodamine B (RhB) under visible‐light irradiation (see picture; ROSs: reactive oxygen species). The copper species act as an electron relay.
This paper conducts research on obstacle and collision avoidance under kinematical constraints in unknown environments, while communication and simultaneous localization and mapping (SLAM) are ...unavailable to agents. Then a strategy based on mixed‐integer programming is proposed, in which velocity constraints are established with a modified Barrier function for obstacles that can be completely detected. As for obstacles that cannot be completely detected, a feasible set is built for the velocity programming based on the convex theory, and the contradicted constraints are addressed with the logic metric method. Besides, the actuator saturation is avoided by converting kinematical constraints into the restrictions on the magnitude, the restrictions on the direction, and the negative correlations between the components of the velocity respectively. Given that invalid nominal velocity leads to collisions, a virtual goal is estimated for nominal velocity improvement. In addition, the local extremum brought by empty programming space due to multiple constraints is repaired by fixing the velocity constraints. The feasibility of the proposed strategy is analyzed, and numerical simulations are provided to verify the effectiveness of the proposed strategy.
1. This paper conducts research on obstacle and collision avoidance under kinematical constraints in unknown environments, while the communication and SLAM are unavailable to agents.
2. Velocity programming based on mixed‐integer programming model is proposed for collision and obstacle avoidance subject to kinematical constraints.
3. Compared with artificial potential fields (APF) and fluid interference method, the proposed method in this paper provide a feasible control in complex environments.
A novel 3D nanostructure consisting of Ni(OH)2 nanoparticles, carbon nanotubes (CNTs), and reduced graphene oxide with an extremely high electrocapacitance is described. The nanostructure consists of ...CNTs with embedded Ni(OH)2 nanoparticles as pillars for reduced graphene oxide sheets. Electrochemical results show that the composite displays specific capacitances as high as 1235 and 780 F g−1 at current densities of 1 and of 20 A g−1, respectively. In addition, the composite retains 80% of its original capacity after 500 cycles at a discharge current density of 10 A g−1. This 3D pseudocapacitor electrode has a number of important features, such as fast ion and electron transfer, easy access of pseudoactive species and efficient utilization, and excellent reversibility of Ni(OH)2 nanoparticles.
Display omitted The preparation of a composite electrode material consisting of Ni(OH)2 nanoparticles embedded in carbon nanotubes as pillars for graphene sheets is demonstrated and used as supercapacitor electrode. The composite displays a specific capacitance as high as 1235 F g−1 at a current density of 1 A g−1 and good cycle stability, representing a new carbon architecture for high-performance supercapacitors.
► Ni(OH)2 embedded in carbon nanotubes as pillars for graphene sheets was prepared. ► The composite showed a high specific capacitance and good cycle stability. ► High performance is due to the unique 3D nanostructure of the capacitor electrode.
Mesoporous anatase (TiO₂) was modified with silver (Ag) nanoparticles using a photoreduction method. Performance of the resulting TiO₂–Ag nanocomposites for water purification was evaluated using ...degradation of Rhodamine B (RhB) and disinfection of Escherichia coli (E. coli) under ultraviolet (UV) irradiation. The composites with different Ag loadings were characterized using physical adsorption of nitrogen, X-ray diffraction, X-ray photoelectron spectroscopy and UV–Visible diffuse reflectance spectroscopic techniques. The results showed that metallic Ag nanoparticles were firmly immobilized on the TiO₂ surface, which improved electron-hole separation by forming the Schottky barrier at the TiO₂–Ag interface. Photocatalytic degradation of RhB and inactivation of E. coli effectively occurred in an analogical trend. The deposited Ag slightly decreased adsorption of target pollutants, but greatly increased adsorption of molecular oxygen with the latter enhancing production of reactive oxygen species (ROSs) with concomitant increase in contaminant photodegradation. The optimal Ag loadings for RhB degradation and E. coli disinfection were 0.25 wt% and 2.0 wt%, respectively. The composite photocatalysts were stable and could be used repeatedly under UV irradiation.
Objective
To compare the clinical effectiveness of a novel approach, percutaneous leverage reduction using two Kirschner-wires (k-wires) combined with the Métaizeau technique, versus open reduction ...plus internal fixation with k-wire for the treatment of Judet IV radial neck fractures in children.
Methods
Thirty-four patients with Judet IV radial neck fractures were treated either with percutaneous leverage reduction using two k-wires and the Métaizeau technique (n = 16) or open reduction plus internal fixation with k-wire (n = 18). Patient data including sex, age, time from trauma to surgery, fracture type, follow up, postoperative healing time, X-ray studies, elbow function, and complications were collected.
Results
There were no significant differences in patient characteristics between the two treatment groups. In postoperative elbow function assessment, 93.8% of patients in the group that underwent the novel treatment approach had a score of excellent or good, compared with 83.3% of patients in the open reduction and internal fixation with k-wire group. Furthermore, no postoperative complications were reported in patients in the novel treatment group, compared with 5 patients in the open reduction and internal fixation with k-wire group. All patients in both groups were classified as excellent or good according to Métaizeau criteria in postoperative X-ray assessment.
Conclusions
Compared with the open reduction and internal fixation with k-wire approach, percutaneous leverage reduction using two k-wires combined with the Métaizeau technique can significantly increase the minimally invasive reduction rate, and represents an attractive strategy for the treatment of Judet IV radial neck fractures in children.
As clinical trials of pharmacological neuroprotective strategies in stroke have been disappointing, attention has turned to the brain's own endogenous strategies for neuroprotection. Recently, a ...hypothesis has been offered that modified reperfusion subsequent to a prolonged ischemic episode may also confer ischemic neuroprotection, a phenomenon termed ‘postconditioning’. Here we characterize both in vivo and in vitro models of postconditioning in the brain and offer data suggesting a biological mechanism for protection. Postconditioning treatment reduced infarct volume by up to 50% in vivo and by ∼30% in vitro. A duration of 10 mins of postconditioning ischemia after 10 mins of reperfusion produced the most effective postconditioning condition both in vivo and in vitro. The degree of neuroprotection after postconditioning was equivalent to that observed in models of ischemic preconditioning. However, subjecting the brain to both preconditioning as well as postconditioning did not cause greater protection than each treatment alone. The prosurvival protein kinases extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), and Akt show prolonged phosphorylation in the cortex of postconditioned rats. Neuroprotection after postconditioning was inhibited only in the presence of LY294002, which blocks Akt activation, but not U0126 or SB203580, which block ERK and P38 MAP kinase activity. In contrast, preconditioning-induced protection was blocked by LY294002, U0126, and SB203580. Our data suggest that postconditioning may represent a novel neuroprotective approach for focal ischemia/reperfusion, and one that is mediated, at least in part, by the activation of the protein kinase Akt.
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