528 research outputs found
Mathematical modeling and vibration simulation of an orbital sander
Numerous epidemiological studies have shown that operators who use hand-held power tools are prone to develop hand-arm vibration syndrome. Therefore, it is necessary to reduce the tool vibrations to protect the worker’s health. This research focuses on the dynamic modeling and the vibration simulation of orbital sanders which are commonly used in industrial sectors. The mathematic model with eighteen degrees-of-freedom (DOF) of this machine is established based upon the Lagrange equation. The experiments are also conducted to test vibrations at the top of the housing where the operators hold the machine. The simulated results are found in good coincidence with the experimental results, and the errors between the experimental results and the simulated values are in acceptable range, which demonstrates the mathematic model in this paper is accurate
Numerical Simulation of Sloshing in 2D Rectangular Tanks Based on the Prediction of Free Surface
A finite difference method for analyzing 2D nonlinear sloshing waves in a tank has been developed based on the potential flow theory. After σ-transformation, the free surface is predicted by the kinematic condition, and nonlinear terms are approximated; the governing equation and boundary conditions are discretized to linear equations in the iterative process of time. Simulations of standing waves and sloshing in horizontally excited tanks are presented. The results are compared with analytical and numerical solutions in other literatures, which demonstrate the effectiveness and accuracy of this numerical method. The beating phenomenon of sloshing in the tank with different aspect ratios is studied. The relationship between sloshing force and aspect ratio under the same external excitation is also discussed
Exact overlaps on the projections of the four corner Cantor set
The four corner Cantor set is a planar self-similar set generated by the
IFS . In this paper we show that
for its projection is a self-similar set
having an exact overlap if, and only if, in lowest term
satisfies and , where
. Let be the set of all
coprime pairs such that has an exact overlap.
By using properties of Euler function from analytic number theory we show that
Comment: 21 pages, 4 figure
Sensitivity analysis of leaf blower vibration isolator based on ISIGHT
In order to reduce the optimal design space of the vibration isolator, a sensitivity analysis method based on ISIGHT for the leaf blower vibration isolator was proposed in this paper. Parametric modeling of the isolator was realized by Solidworks, Hypermesh, Optistruct and ADAMS, and a multi-software co-simulation working framework based on ISIGHT was established. Taking the design parameters of the vibration isolator as the variable and the minimum transmission force as the optimization, Sensitivity analysis of the vibration isolator was carried out based on the Latin Hypercube. The results show that the length of the vibration isolator has the greatest influence on the vibration isolation and the contribution of d1, d3, D3 and E3 is the smallest. The result provided a guiding significance for the design optimization of the vibration isolator
Visual Realism Assessment for Face-swap Videos
Deep-learning based face-swap videos, also known as deep fakes, are becoming
more and more realistic and deceiving. The malicious usage of these face-swap
videos has caused wide concerns. The research community has been focusing on
the automatic detection of these fake videos, but the assessment of their
visual realism, as perceived by human eyes, is still an unexplored dimension.
Visual realism assessment, or VRA, is essential for assessing the potential
impact that may be brought by a specific face-swap video, and it is also
important as a quality assessment metric to compare different face-swap
methods. In this paper, we make a small step towards this new VRA direction by
building a benchmark for evaluating the effectiveness of different automatic
VRA models, which range from using traditional hand-crafted features to
different kinds of deep-learning features. The evaluations are based on a
recent competition dataset named DFGC 2022, which contains 1400 diverse
face-swap videos that are annotated with Mean Opinion Scores (MOS) on visual
realism. Comprehensive experiment results using 11 models and 3 protocols are
shown and discussed. We demonstrate the feasibility of devising effective VRA
models for assessing face-swap videos and methods. The particular usefulness of
existing deepfake detection features for VRA is also noted. The code can be
found at https://github.com/XianyunSun/VRA.git.Comment: Accepted by ICIG 202
rac-3,9-Bis(3-chlorophenyl)-2,4,8,10-tetraoxaspiro[5.5]undecane
In the title compound, C19H18Cl2O4, the two non-planar six-membered heterocycles passing through the spiro-C atom both adopt chair conformations, and the dihedral angle between the two benzene rings is 7.2 (1)°. In the crystal, the enantiomers with R and S configurations are generated by the symmetry elements of the centrosymmetric space group, forming a racemic crystal. Intermolecular C—H⋯π and weak C—H⋯O interactions link the molecules in the crystal structure
Photoluminescence from Bi5(GaCl4)3 molecular crystal
Bi5(GaCl4)3 sample has been synthesized through the oxidation of Bi metal by
gallium chloride (GaCl3) salt. Powder X-ray diffraction as well as micro-Raman
scattering results revealed that, in addition to crystalline Bi5(GaCl4)3 in the
product, amorphous phase containing [GaCl4]- and [Ga2Cl7]- units also exist.
The thorough comparison of steady-state and time-resolved photoluminescent
behaviors between Bi5(GaCl4)3 product and Bi5(AlCl4)3 crystal leads us to
conclude that Bi53+ is the dominant emitter in the product, which gives rise to
the ultrabroad emission ranging from 1 to 2.7 micrometer. Detailed quantum
chemistry calculation helps us assign the observed excitations to some
electronic transitions of Bi53+ polycation, especially at shorter wavelengths.
It is believed that our work shown here not only is helpful to solve the
confusions on the luminescent origin of bismuth in other material systems, but
also serves to develop novel broadband tunable laser materials
Investigation and protection of fishery resources in the middle of Bohai Sea
In May and October 2017, 12 stations were set up in the Central Bohai Sea for fishery resources investigation. The results show that there are many dominant species in this area, and the inshore fishery resources are higher than those in the open sea because of the abundant nutrients from land, the high density of zooplankton and the food of swimming animals. In order to effectively protect the fishery resources in the Central Bohai Sea, this paper puts forward some suggestions, such as strengthening the protection propaganda, scientific and reasonable fishing, and strengthening the management of marine environment
Contactless Haptic Display Through Magnetic Field Control
Haptic rendering enables people to touch, perceive, and manipulate virtual
objects in a virtual environment. Using six cascaded identical hollow disk
electromagnets and a small permanent magnet attached to an operator's finger,
this paper proposes and develops an untethered haptic interface through
magnetic field control. The concentric hole inside the six cascaded
electromagnets provides the workspace, where the 3D position of the permanent
magnet is tracked with a Microsoft Kinect sensor. The driving currents of six
cascaded electromagnets are calculated in real-time for generating the desired
magnetic force. Offline data from an FEA (finite element analysis) based
simulation, determines the relationship between the magnetic force, the driving
currents, and the position of the permanent magnet. A set of experiments
including the virtual object recognition experiment, the virtual surface
identification experiment, and the user perception evaluation experiment were
conducted to demonstrate the proposed system, where Microsoft HoloLens
holographic glasses are used for visual rendering. The proposed magnetic haptic
display leads to an untethered and non-contact interface for natural haptic
rendering applications, which overcomes the constraints of mechanical linkages
in tool-based traditional haptic devices
- …