Ultra-high frequency, high Q/volume micromechanical resonators in a planar AlN phononic crystal

Citation: Baboly, M. G., Alaie, S., Reinke, C. M., El-Kady, I., & Leseman, Z. C. (2016). Ultra-high frequency, high Q/volume micromechanical resonators in a planar AlN phononic crystal. Journal of Applied Physics, 120(3), 5. doi:10.1063/1.4958671This paper presents the first design and experimental demonstration of an ultrahigh frequency complete phononic crystal (PnC) bandgap aluminum nitride (AlN)/air structure operating in the GHz range. A complete phononic bandgap of this design is used to efficiently and simultaneously confine elastic vibrations in a resonator. The PnC structure is fabricated by etching a square array of air holes in an AlN slab. The fabricated PnC resonator resonates at 1.117 GHz, which corresponds to an out-of-plane mode. The measured bandgap and resonance frequencies are in very good agreement with the eigen-frequency and frequency-domain finite element analyses. As a result, a quality factor/volume of 7.6 x 10(17)/m(3) for the confined resonance mode was obtained that is the largest value reported for this type of PnC resonator to date. These results are an important step forward in achieving possible applications of PnCs for RF communication and signal processing with smaller dimensions. Published by AIP Publishing

COD removal from gasfield produced water using photoelectrocatalysis process on coil type microreactor

A special type of reactor with a high active surface-to-volume ratio was used for investigation of organic pollutants degradation from a gasfield produced water by photoelectrocatalysis process. The GC–MS analysis showed that there were more than 50 organic substances in this wastewater; therefore, COD was considered as the target parameter for studying. A simple evaporation process used for decreasing high TDS of the wastewater reduced its electrical conductivity from 6300 μS/cm to 1100 μS/cm and also initial COD decreased simultaneously from 9500 mg/L to 750 mg/L. Distilled wastewater from the evaporation process was treated again by the photoelectrocatalysis process using a coil type microreactor, and its COD dropped off to 143 mg/L. Instead of usual semiconductors in photoelectrocatalysis like TiO2, boron carbon nitride (BCN) nanosheets are used as a photocatalyst in this study. Investigating the impact of different parameters on COD removal efficiency showed that the greatest COD removal efficiency (81%) was obtained at residence time 15 min, pH = 3, applied cell voltage 20 V, electrical conductivity = 2500 μS/cm and H2O2 concentration of 8 mM. © 2021 The Korean Society of Industrial and Engineering Chemistr

The effect of stiffness and mass on coupled oscillations in a phononic crystal

Insight into phononic bandgap formation is presented using a first principles-type approach where phononic lattices are treated as coupled oscillators connected via massless tethers. The stiffness of the tethers and the mass of the oscillator are varied and their influences on the bandgap formation are deduced. This analysis is reinforced by conducting numerical simulations to examine the modes bounding the bandgap and highlighting the effect of the above parameters. The analysis presented here not only sheds light on the origins of gap formation, but also allows one to define design rules for wide phononic gaps and maximum gap-to-midgap ratios

Iranian consensus on use of vitamin D in patients with multiple sclerosis

Background: Accumulating evidences from experimental, epidemiologic and clinical studies support the potential linkage between poor vitamin D status and the risk of developing Multiple Sclerosis (MS), as well as, an adverse disease course. However, the results of the trials on the clinical outcomes of vitamin D supplementation in MS patients are less consistent which brought many discrepancies in routine practice. In this article we presented a summary of a symposium on vitamin D and MS. In this symposium we aim to review the current data about the relationship between vitamin D and MS, and suggest management guides for practicing neurologists. Discussion: Generally, supplementation seems to be reasonable for all MS and clinically isolated syndrome (Rinaldi et al., Toxins 7:129-37, 2015) patients with serum 25(OH)D level below 40ng/ml. In patients with vitamin D insufficiency or deficiency, a large replacing dose (e.g. 50,000IU capsules of D per week for 8-12 week) is recommended. Panel also suggested: the checking of the serum vitamin D, and calcium level, as well as, patients' compliance after the initial phase; a maintenance treatment of 1500-2000IU daily or equivalent intermittent (weekly, biweekly or monthly) Dose, considering the patient's compliance; routine check of serum vitamin D level at least two times a year especially at the beginning of spring and autumn; Serum vitamin D evaluation for first degree relatives of MS patients at high risk age and supplementation in case of insufficiency (25(OH)D less than 40 ng/ml); correction of vitamin D deficiency and insufficiency before pregnancy, as well as, a daily dose of 1500-2000IU or equivalent biweekly intake in 2nd and 3rd trimesters; stopping supplementation if 25(OH)D serum level exceeds 100ng/ml. Summary: Although the results of high power studies are not available, correcting vitamin D status seems plausible in all MS and CIS patients. Maintaining the serum 25(OH)D level between 40 and 100 ng/ml is not known to exert adverse effect. More ever, it might be associated with lower disease activity. © 2016 Jahromi et al