Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 6 Articles
Saturable absorption and reverse saturable absorption play an important role in the studies of the nonlinear optical properties\nof nanoparticles at resonant excitation. With this viewpoint, nonlinear absorption processes of chemically prepared silver\nnanoparticles in deionized water were studied using femtosecond laser pulses at 400 nm. Our nonlinear absorption study\nshows that there is competition between saturable absorption and two-photon absorption in prepared Ag NPs which\ndepends on the size of the nanoparticles. We have also studied the ultrafast dynamics associated with nanoparticles which\nalso results in the direct correlation between the ultrafast timescale and the size of the nanoparticle. The excitation of Ag\nNPs at 400 nm has shown the manifestation of damped oscillation which is attributed to the radial breathing mode\noscillation due to acoustic vibration....
Photonic resonances in nanostructures have been exploited in reflective or transmission color filters, which can provide vivid\ncolors. Metallic nanostructures have been widely studied to demonstrate a variety of color filters based on strong light\ninteraction due to plasmonic resonances. However, because of the severe absorption loss of metal in visible light, dielectric\nnanoparticles having Mie resonances are a popular study focus in recent years to achieve vivid colors. In contrast to the behaviors\nof point-like electric dipole in metallic nanoparticle, the interplay of the electric and magnetic Mie resonances in dielectric\nnanoparticle enables a large degree of freedom in manipulating the directivity of light scattering, reflecting/transmitting color, and\nspontaneous emission rates. Here, we propose a color reflector based on an array of silicon nanoparticles that shows reflectance\ngreater than 70% and vivid colors over the entire visible spectrum range, which covers sRGB color area. Viewing angle\ndependencies of the color and brightness are also investigated by calculating color-resolved far-field patterns, while exhibiting\nmaintenance of the color and high reflectance over a broad viewing angle....
In the process of adsorption and separation of fluid molecules on the solid surface of porous nanomaterials, the mutual\ntransformation of thermal energy and surface energy can improve the heat absorption and energy utilization efficiency of\ncirculating working medium. In this study, the adsorption, thermal energy storage, and mean square displacement of the\nminimum energy adsorption configuration of R1234ze in UIO-66 were studied by molecular simulations, including molecular\ndynamics (MD) and grand canonical Monte Carlo (GCMC) simulations. The results show that the thermal energy storage\ndensity of R1234ze/UIO-66 mixed working medium is significantly higher than that of pure working medium in the\ntemperature range of 20 K-140 K. However, the increase rate of thermal energy storage density decreases significantly as\ntemperature rises, and the mean square displacement and diffusion coefficient increase with increasing temperature....
Printing technology offers a simple and cost-effective opportunity to develop all-printed\nstretchable circuits and electronic devices, possibly providing ubiquitous, low-cost, and flexible\ndevices. To successfully prepare high-aspect-ratio Ag nanowires (NWs), we used water and\nanhydrous ethanol as the solvent and polyvinylpyrrolidone (PVP) as the viscosity regulator to\nobtain a water-soluble Ag NWs conductive ink with good printability. Flexible and stretchable\nfabric electrodes were directly fabricated through screen printing. After curing at room temperature,\nthe sheet resistance of the Ag NW fabric electrode was.................
Wall-climbing hexapod robot as a bionic robot has become a focus for extensive research, due to a wide range of practical\napplications. The most contribution of this paper is to analyze the kinematics and stability of a wall-climbing hexapod\nrobot, so as to provide a theoretical basis for the stable walking and control of the robot on the wall. Firstly, the\nkinematics model of the wall-climbing hexapod robot is established based on the D-H method. Then, in order to keep the\nrobot from tipping over, the stability of the wall-climbing hexapod robot is analyzed in depth, obtaining the critical\ncondition which makes the robot to tip over. Afterward, the kinematics simulation of the wall-climbing hexapod robot is\noperated to analyze motion performances. Finally, the experiments are used to validate the proposed kinematics model and\nstability. The experimental results show that the kinematics model and stability condition of the wall-climbing hexapod\nrobot are correct....
With the development of marine resources, research on underwater robots has received unprecedented attention.Thediscovery and\napplication of new smartmaterials provide new ideas for the research of underwater robots, which can overcome the issues of traditional\nunderwater robots and optimize their design. A macro fiber composite (MFC) is a new type of piezoelectric fiber composite\nthat combines actuators and sensors. The material has excellent deflection, good flexibility, and a high electromechanical coupling\ncoefficient. Bionic mechatronics design is an effective way to innovate mechatronics in the future and can significantly improve\nmechatronics system performance. As an important issue for the design of bionic mechatronics, it is necessary to make robots as\nsoft as natural organisms to achieve similar biological movement with both higher efficiency and performance. Compared with traditional\nrigid robots, the design and control of a soft robotic fish are difficult because the coupling between the flexible structure and\nthe surrounding environment should be considered, which is difficult to solve due to the large deformation and coupling dynamics.\nIn this paper, anMFC smart material is applied as an actuator in the design of bionic robotic fish. Combined with the piezoelectric\nconstitutive and elastic constitutive equations of theMFCmaterial, the voltage-drive signal is converted to a mechanical load applied\nto the MFC actuator, which makes the MFC material deform and drives the movement of the robotic fish. The characteristics of\ncaudal fin motion during the swimming process of the bionic robotic fish were analyzed by an acoustic-solid coupling analysis\nmethod. The motion control analysis of the bionic robotic fish was carried out by changing the applied driving signal. Through\nnumerical analysis, a new type of soft robotic fish was designed, and the feasibility of using anMFC smart material for underwater\nbionic robotic fish actuators was verified. The new soft robotic fish was successfully developed to achieve high performance....
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