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 $C$ is a planar self-similar set generated by the IFS $\{(\frac{x}{4}, \frac{y}{4}),(\frac{x+3}{4}, \frac{y}{4}),(\frac{x}{4}, \frac{y+3}{4}), (\frac{x+3}{4}, \frac{y+3}{4})\}$. In this paper we show that for $t>0$ its projection $C_t:=\{x+ty: (x,y)\in C\}$ is a self-similar set having an exact overlap if, and only if, $t=p/q\in\mathbb Q$ in lowest term satisfies $p\notin\Gamma$ and $q\notin\Gamma$, where $\Gamma:=\{(2k-1)2^{2\ell-1}: k,\ell\in\mathbb N\}$. Let $W$ be the set of all coprime pairs $(p,q)\in\mathbb N^2$ such that $C_{p/q}$ has an exact overlap. By using properties of Euler function from analytic number theory we show that $$\lim_{N\to\infty}\frac{\#(W\cap[1,N]^2)}{N^2}=\frac{10}{3\pi^2}.$$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