A 10-MHz FREE-FREE BEAM MICROMECHANICAL RESONATOR FABRICATION PROCESS USING SURFACE-MICROMACHINED TECHNOLOGY

The fabrication process for the designed MEMS resonator using surface-micromachined technology is presented in this paper. A 10-MHz Free-Free beam MEMS resonator is designed to vibrate in the second-mode shape, which is significant improvement compare to the fundamental mode. The design showed a Q value as high as 75,000, which is significant improvement compared to 8,400 VHF F-F beam MEMS resonator by K. Wang; and very low motional resistance (18kΩ). The surface-micromachined technology is used as the standard process for the design. The process is briefly described from the layout design to the experimental fabricated device.

Investigating the behavior of boundary elements in steel shear walls with different connections

In the recent five decades, steel shear walls have been one of the most important systems in the construction and rehabilitation of many structures. The system has many advantages including high strength and stiffness, high ductility and excellent energy dissipation capacity. Steel shear walls are made and executed in different types. These include walls with and without stiffeners as well as composites. Recent research shows that they are a type of steel shear wall in which the infill plate is slightly away from the boundary members. In fact, there is no connection between the infill plate and one of boundary members. Therefore, in this study, the behavior of traditional one-story-one-span steel shear walls with 4 different lengths was investigated. For comparison, walls in which the sheet was attached only to a beam or column were examined. Obtained results from the study showed that the lateral bearing capacity of samples with free beam or free column is less than that of samples with full connection, on average 20%. Also, the strength of the samples with free column is slightly higher than the samples with free beam. In addition, boundary members, especially columns, are much less affected by forces in free-column specimens than in other specimens, and this could decreases economical costs.

Fabrication and characterization of aluminum, gold-tin and titanium-tungsten alloys for mid-infrared plasmonic applications

We numerically and experimentally investigate aluminum metal (Al), gold-tin (AuSn) and titanium-tungsten (TiW) metallic alloys as plasmonic materials in the mid-infrared (MIR) region using spectroscopic ellipsometry and reflection measurements of gratings. The angle dependence of the specular reflectance of shallow gratings is investigated using a free-beam measurement setup and compared to simulations. It is shown that the deep and narrow resonances observed for all three materials match the associated prediction from simulations.

Skyshine Dose Estimations for an 18 MeV Photon Beam Using MCNPX Code: A Comparison of Flattened and Flattening Filter-Free Beam

Purpose: The current study aimed to estimate photon skyshine dose rate from a Varian linac equippedwith a Flattening Filter (FF) and its FF-Free (FFF) mode. The skyshine photons from a Linac bunker can influence the radiation dose received by personnel and the public in radiation therapy centers. Materials and Methods: In the current study skyshine dose from the conventional flattened beam and the flattening-free beam were compared. The MCNPX Monte Carlo code was used to model an18 MeV photon beam of Varian linac. The skyshine radiation was calculated for FF and FFF linac photon beams at the control room, parking, sidewalk, and corridor around the linac room. Results: For the conventional beam, the skyshine dose rates of 0.53, 0.42, 0.45, and 0.50 mSv/h were estimated for the control room, corridor, sidewalk, and parking, respectively. While for the FFF beam, dose rates of 0.21, 0.20, 0.20, and 0.23 mSv/h were estimated for the same positions, respectively. The results indicated that the empirical method of NCRP 151 can not distinguish between FF and FFF beams in skyshine dose calculations. Our results found a 50% lower level dose rate from the FFF beam at distant and nearby locations. Conclusion: The findings of current can be helpful in the radiation dose calculations and the radiation protection designation of radiation therapy bunkers.

Analytical study of the natural bending oscillations of a concave beam with parabolic change in thickness

The synthesis of factorization and symmetry methods produced a general analytical solution to the fourth-order differential equation with variable coefficients. The form and structure of the variable coefficients correspond, in this case, to the problem of the oscillations of a concave beam of variable thickness. The solution to this equation makes it possible to study in detail the oscillations of such and similar, for example convex, beams at the different fixation of their ends' sections. A practical confirmation has been obtained that the beam whose thickness changes in line with the concave parabola law H=a2x2+1, where a is the concave factor, demonstrates an increase in the natural frequencies of its free oscillations with an increase in its rigidity. As an example, the object's maximum deflection dependence on the beam rigidity factor has been established. The nature of this dependence confirmed the obvious conclusion that the deflections had decreased while the rigidity had increased. The evidence from the calculation results can be a testament to the correctness of the reported procedure of problem-solving. The considered problem and the analytical solution to it could serve as a practical guide to the optimal design of beam structures. In this case, it is very important to take into consideration the place and nature of the distribution of cyclical extreme operating stresses. The resulting ratios to solve the problem make it possible to simulate the required normal stresses in both the fixation and central zones when the rigidity parameter is changed. Designers could predict such a parabolic profile of the beam, which would ensure the required reduction of maximum stresses in the place of fixing the beam. The considered example of solving the problem of the natural oscillations of the beam with rigid fixation of the ends illustrates the effectiveness of the factoring and symmetry methods used. The developed solution algorithm could be extended to study the natural bending oscillations of the beam at other fixing techniques, not excluding a variant of a completely free beam