RESUMO
This paper examines the influence of the equipment considered as a DVA (Dynamic Vibration Absorber) upon the mode of vertical vibrations of the car body in high-speed vehicles. The car body is represented as an Euler-Bernoulli beam to minimize flexible vibration. The DVA approach is used to find the appropriate suspension frequencies for various types of equipment. A vertical mathematical model with a flexible car body and equipment is developed to investigate the effect of equipment mass, suspension stiffness, damping, and mounting location on car-body flexible vibrations. A three-dimensional, rigid-flexible coupled vehicle system dynamics model is developed to simulate the car body and equipment's response to track irregularities. The experimental result was considered to verify the theoretical analysis and dynamic simulation. The mathematical analysis demonstrates that the DVA theory can be used to design the suspension parameters of the equipment and that it is suitable and effective in reducing the flexible vibration of the car body in which the vertical bending mode is greatly affected. Heavy equipment should be mounted as close to the car body's center as possible to achieve significant flexible vibration reduction, whereas light equipment contributes very little flexible vibration reduction.
RESUMO
As the environmental pollution issue has recently become significant, environmental regulations in Europe and the United States are being strengthened. Thus, there is a demand for the quality improvement of emission after-treatment systems to satisfy the strengthened environmental regulations. Reducing the amount of welding heat distortion by optimization of the welding order of each part could be a solution for quality improvement since the emission after-treatment system consists of many parts and each assembly is produced by welding individual ones. In this research, a method to derive a welding sequence that effectively minimizes welding deformation was proposed. A two-stage simulation was performed to obtain the optimal welding sequence. In the first stage, the welding sequence was derived by analyzing the number of welding groups in each assembly of a structure. The derived welding sequence was verified by performing a thermal elasto-plastic analysis and comparing it with the experimental results.
RESUMO
From the images of HR-TEM, FE-SEM, and AFM, the cold welding of gold nanoparticles (AuNPs) on a mica substrate is observed. The cold-welded gold nanoparticles of 25 nm diameters are found on the mica substrate in AFM measurement whereas the size of cold welding is limited to 10 nm for nanowires and 2~3 nm for nanofilms. Contrary to the nanowires requiring pressure, the AuNPs are able to rotate freely due to the attractive forces from the mica substrate and thus the cold welding goes along by adjusting lattice structures. The gold nanoparticles on the mica substrate are numerically modeled and whose physical characteristics are obtained by the molecular dynamic simulations of LAMMPS. The potential and kinetic energies of AuNPs on the mica substrate provide sufficient energy to overcome the diffusion barrier of gold atoms. After the cold welding, the regularity of lattice structure is maintained since the rotation of AuNPs is allowed due to the presence of mica substrate. It turns out that the growth of AuNPs can be controlled arbitrarily and the welded region is nearly perfect and provides the same crystal orientation and strength as the rest of the nanostructures.
RESUMO
Gold nanoparticles (AuNPs) were synthesized by a green method using a plant secondary metabolite, gallotannin. Gallotannin was used as a reducing and capping agent to convert gold ions into AuNPs for the generation of gallotannin-capped AuNPs (GT-AuNPs). This synthetic route is ecofriendly and eliminates the use of toxic chemical reducing agents. The characteristic surface plasmon resonance of the GT-AuNPs was observed at 536 nm in the UV-visible spectra. The face-centered cubic structure of GT-AuNPs was verified by X-ray diffraction analysis. The majority of the GT-AuNPs had a spherical shape with an average diameter of 15.93 ± 8.60 nm. Fourier transform infrared spectra suggested that the hydroxyl functional groups of gallotannin were involved in the synthesis of GT-AuNPs. The size and shape of nanoparticles can have a crucial impact on their biological, mechanical, and structural properties. Herein, we developed a modified anisotropic diffusion equation to selectively remove nanoscale experimental noise while preserving nanoscale intrinsic geometry information. To demonstrate the performance of the developed method, the ridge and valley lines were plotted by utilizing the principle curvatures. Compared to the original anisotropic diffusion and raw atomic force microscopy (AFM) experimental data, the developed modified anisotropic diffusion shows excellent performance in nanoscale noise removal while preserving the intrinsic aeometry of the nanoparticles.
