Highly reliable electromagnetic MOEMS scanning grating mirror based on folded torsion beam with fillet corners

To overcome the problems of poor structural reliability, high driving voltage and small scanning angle, a novel electromagnetic MOEMS scanning grating mirror (SGM) with folded torsion beam is reported in this work. Compared with the conventional straight torsion beam, the folded torsion beam has better elastic torsion property and can effectively improve the structural reliability of the MOEMS SGM. Furthermore, the fillet structure is added to the folded torsion beam to prevent stress concentration. The stress analysis and impact resistance of the proposed MOEMS SGM are simulated by FEM (ANSYS 18.2), and the simulation results are compared with that of the MOEMS SGM without fillet structure. The stress simulation is carried out under different fillet radius of 40–70 [Formula: see text]m, the maximum stress can be reduced to 85[Formula: see text] and the stress is redistributed uniformly. Meanwhile, in the impact resistance simulation, the impact displacement can be reduced by 10.1[Formula: see text]. A prototype is fabricated and tested, it has a large mirror area of 6 mm ×7 mm. The MOEMS SGM can reach the maximum scanning half angle of [Formula: see text] at 7.63 V under resonance (@602.1 Hz), which means that the full mechanical scanning angle of the MOEMS SGM can reach [Formula: see text].

Restricted Burnside problem for semigroups and its application to language theory

In this paper, we introduce the concept of strongly torsion property of semigroups. Then we prove that the strongly torsion property of a semigroup is a necessary and sufficient condition for a finitely generated semigroup to be finite, and hence, the strongly torsion property is equivalent to the torsion property together with the permutation property for the class of finitely generated semigroups. Finally, we give an application of our main result to language theory. A question proposed in [H. Prodinger, Congruences defined by languages and filters, Inf. Control 44 (1980) 36–46] is consequently answered.

Torsion Property of the Structure Bonded Aluminum Foam Due to Impact

An aluminum foam added with foaming agent, is classified into an open-cell type for heat transfer and a closed-cell type for shock absorption. This study investigates the characteristic on the torsion of aluminum foam for a closed-cell type under impact. The fracture characteristics are investigated through the composite of five types of aluminum foam (the thicknesses of 25, 35, 45, 55 and 65 mm), when applying the torsional moment of impact energy on the junction of a porous structure attached by an adhesive. When applying the impact energy of 100, 200 and 300J, the aluminum foams with thicknesses of 25 mm and 35 mm broke off under all conditions. For the energy over 200J, aluminums thicker than 55 mm continued to be attached. Furthermore, the aluminum specimens with thicknesses of 55 mm and 65 mm that were attached with more than 30% of bonding interface remained, proving that they could maintain bonding interface against impact energy. By comparing the data based on the analysis and test result, an increase in the thickness of specimen leads to the plastic deformation as the stress at the top and bottom of bonding interface moves to the middle by spreading the stress horizontally. Based on this fracture characteristic, this study can provide the data on the destruction and separation of bonding interface and may contribute to the safety design.

Torsion Property and Cyclic Fatigue Fracture Behavior of Nickel-Titanium Endodontic Instruments

The torsion property and rotary fatigue fracture behavior of SmartÒ K file and R reamer made of nickel titanium alloy have been studied by means of Shimadzu Autograph DDS-10T universal tester and man-made cyclic system with curved copper tubes as simulated root canal. The instrument surface and the cyclic fatigue fracture surface have been investigated by optical microscope and scanning electron microscope. Comparing with ANSI/ADA specification no.28, maximum torsion values of both SmartÒ K and R endodontic instruments are satisfied in practice. Tensile stresses on the outer surface of the endodontic instruments play a dominant role in fracture initiation during cyclic fatigue fracture. The cyclic number corresponding to cyclic fatigue fracture decreases with the increase of the instrument size number/ curvature. SmartÒ K- and R endodontic instruments exhibit good ductility characteristics, therefore superior resistance to fracture.