There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

News and social media platforms have implicated dietary supplements in the treatment and prevention of coronavirus disease 2019 (COVID-19). During this pandemic when information quickly evolves in the presence of contradicting messages and misinformation, the role of the pharmacist is essential. Here, we review theoretical mechanisms and evidence related to efficacy and safety of select supplements in the setting of COVID-19, including vitamin C, vitamin D, zinc, elderberry, and silver. Evidence evaluating these supplements in COVID-19 patients is lacking, and providers and patients should not rely on dietary supplements to prevent or treat COVID-19. Rather, reference to evidence-based guidelines should guide treatment decisions.

https://journals.sagepub.com/doi/pdf/10.1177/1060028020928052

Myth Busters: Dietary Supplements and COVID-19.

A current transformer (CT) is accurately modeled for representation of the CT saturation effects on digital protective relays. Simulation studies performed in the PSCAD/EMTDC platform are used to investigate the impacts of CT saturation on the current phasor estimation. A new algorithm is also proposed for detection and compensation of CT saturation effects, based on: a least error squares (LES) filter which estimates the phasor parameters of the CT secondary current; a novel saturation detection method which uses the output of the LES filter for saturation detection; and a new minimum estimation error tracking approach which enhances the precision of the phasor estimation. The proposed saturation detection/compensation algorithm is independent of the parameters of the CT, the burden, and the power system. The study results show that the proposed algorithm: 1) reconstructs the distorted current waveform, under dc and ac saturation conditions, with the required precision and speed and 2) performs satisfactorily under inductive burden and under deep and slight saturation conditions.

/pdf/compensation-of-the-current-transformer-saturation-effects-aokm4uygzk.pdf

Compensation of the Current-Transformer Saturation Effects for Digital Relays

In this paper, we present the first automated system-level analysis of multicore CPUs based on ARMv8 64-bit architecture (8-core, 28nm X-Gene 2 micro-server by AppliedMicro) when pushed to operate in scaled voltage conditions. We report detailed system-level effects including SDCs, corrected/uncorrected errors and application/system crashes. Our study reveals large voltage margins (that can be harnessed for energy savings) and also large $V_{min}$ variation among the 8 cores of the CPU chip, among 3 different chips (a nominal rated and two sigma chips), and among different benchmarks.Apart from the $V_{min}$ analysis we propose a new composite metric (severity) that aggregates the behavior of cores when undervolted and can support system operation and design protection decisions. Our undervolting characterization findings are the first reported analysis for an enterprise class 64-bit ARMv8 platform and we highlight key differences with previous studies on x86 platforms. We utilize the results of the system characterization along with performance counters information to measure the accuracy of prediction models for the behavior of benchmarks running in particular cores. Finally, we discuss how the detailed characterization and the prediction results can be effectively used to support design and system software decisions to harness voltage margins for energy efficiency while preserving operation correctness. Our findings show that, on average, 19.4% energy saving can be achieved without compromising the performance, while with 25% performance reduction, the energy saving raises to 38.8%.CCS CONCEPTS• Hardware → Power and energy → Power estimation and optimization; • Hardware → Robustness → Hardware reliability → Process, voltage and temperature variations

Harnessing voltage margins for energy efficiency in multicore CPUs

Residues from the processing of cassava roots (Manihot esculenta Crantz), or cassava peels, are evaluated as chemically modified adsorbents with H2O2, H2SO4, and NaOH, in the removal of metal ions Cd(II), Pb(II), and Cr(III) from contaminated water. Modified adsorbents were chemically characterized for their chemical composition and (point of zero charge), while adsorption tests determined the best conditions of pH, adsorbent mass, and contact time between adsorbent and adsorbate in the process of removal of the metal ions. Isotherms obtained from the preliminary results were linearized by Langmuir’s and Freudlich’s models. The thermodynamic parameters, such as , , and , were also evaluated. The modifying solutions proposed were effective in the modification of adsorbents and resulted in high capacity sorption materials. Equilibrium time between adsorbent and adsorbate for the solutions contaminated with metals is about 40 minutes. The Langmuir model adjusted to most results, indicating monolayers adsorption of Cd(II), Pb(II), and Cr(III). The values obtained for Langmuir show a higher adsorption capacity caused by chemical modifications, with values such as 19.54 mg Cd(II) per g of M. NaOH, 42.46 mg of Pb(II) per g of M. NaOH, and 43.97 mg of Cr(III) per g of M H2O2. Results showed that modified cassava peels are excellent adsorbent, renewable, high availability, and low-cost materials and a feasible alternative in the removal of metals in industries.

/pdf/chemical-modifications-of-cassava-peel-as-adsorbent-material-1oyvtwe2n9.pdf

Chemical Modifications of Cassava Peel as Adsorbent Material for Metals Ions from Wastewater

Silicon-on-insulator (SOI)-based lateral PIN photodiodes using SiGe/Si multilayer quantum wells (MQW) are suitable for applications in the near-infrared range both for sensing and optical fiber communication application. The objective of this paper is to optimize the process parameters for such a device using Taguchi's L27 orthogonal array. Five device process parameters and two device noise factors were identified to make the virtual device design insensitive to variation in the selected fabrication parameters. The results obtained for responsivity after the optimization approach was 0.33 A/W for the optimized device with intrinsic region length of 6 μm, photo-absorption layer thickness of 0.505 μm, incident optical power of 0.5 mW/cm2, bias voltage of 3.5 V and SOI layer thickness of 0.5 μm. The percentage of improvement for the device's responsivity is 27% as compared to the previous work.

Responsivity optimization of a MQW SOI-based lateral PIN photodiode using Taguchi's L 27 orthogonal array

This paper reports the improvement in tensile strength of epoxy by using binary hybrid nanocomposites of nanoclay and multi-wall carbon nanotube using a solution casting method. The effect of clay/MWCNT ratio, types of solvent, clay cation, composition of LENR, cure time and cure temperature on the tensile properties of epoxy nanocomposites were investigated using Taguchi Method. Orthogonal array L27 is chosen for sample preparations. Analysis of Mean (ANOM) and Analysis of Variance (ANOVA) was used to identify the dominant factors and the optimum values of clay/MWCNT ratio and settings of other process parameters. Confirmation of experiment was performed with the optimum parameter settings and the measured mechanical properties were compared with the predicted results. Morphologies of the fracture surface of MWCNT/epoxy nanocomposites was observed by scanning electron microscope (SEM). Transmission electron microscope (TEM) and X-ray diffraction (XRD) test were employed to analyse the dispersion structure in the modified samples.

Application of Taguchi's Approach in the Optimization of Tensile Properties of Epoxy/Nanoclay/MWCNT Nanocomposites

The MEMS accelerometer has a high cross sensitivity due to proof mass being eccentric. This paper gives results for a SU-8 z-axis accelerometer that uses 8-resistor Wheatstone-bridge to reduce the x-axis and y-axis cross sensitivity by 2 orders of magnitude compared to the conventional 4-resistor Wheatstone-bridge arrangement.

A 8-resistor SU-8 accelerometer with reduced cross axis sensitivity

MEMS device structures, particularly those made using Surface-Micromachining, consist of thin layers of insulator, silicon, silicon dioxide, silicon nitride, metal or poly-silicon held at few points onto a thick silicon substrate. These heterogeneous layers resemble closely to laminas of composites used in building structures. For these heterogeneous material systems, involving Metal-Insulator-Semiconductor layers, there is usually an inherent two dimensional thermal contraction of the various layers upon cooling from a growth temperature of 1000 to 1200 C down to room temperature. The thermal stress, so developed, could result in static deformation as well change the dynamic characteristics of the micro-parts. Thin heteroepitaxial layers, with lattice mismatch with the single crystal substrate, can also result in a built in stress. External effects like electrostatic potentials and magnetic fields applied to a layered structure can also result in contractions or extensions of specific layers that respond to applied fields. A generic formulation of governing equations of equilibrium and compatibility has been developed for laminated structures with various in-built stress effects like difference in temperature of formation and use; difference in lattice constants of heteroepitaxial layers; effects that involve dimensional changes like piezoelectric effect and magnetostriction. This paper aims at demonstrating, through simulations of a test structure of a doubly suspended resonator, how these multi-layer structures could exploit the static deformations to result in a robust (temperature-insensitive) dynamic response. The static deformation for temperature changes in a bi-layer of aluminum and silicon dioxide is simulated on ANSYS. The results of ANSYS match very well with a fabricated test device.

2D simulation of multilayered MEMS structures

Many promising applications of MEMS based devices are in critical systems. Hence, their reliability has become an important issue. The techniques used for the fabrication of these devices give rise to large residual stresses. This coupled with their high speeds of operation make them prone to fatigue failure. The focus of this work is the improvement of reliability under fatigue loading using multi-layers. This paper demonstrates that by adjusting the thickness ratios, the stress in a multi-layered resonator can be prevented from alternating. Moreover, the peak stress can be minimized and performance can be improved in harsh environments.

Prakash R. Apte

Papers

Responsivity optimization of a MQW SOI-based lateral PIN photodiode using Taguchi's L 27 orthogonal array

Application of Taguchi's Approach in the Optimization of Tensile Properties of Epoxy/Nanoclay/MWCNT Nanocomposites

A 8-resistor SU-8 accelerometer with reduced cross axis sensitivity

2D simulation of multilayered MEMS structures

Improvement in reliability of MEMS resonator using multi-layers