Performance Analysis of Three-Wavelength Multi-Channel Photonic Crystal Filters of Different Sizes

Multi-wavelength and multi-channel photonic crystal filters are designed with different sizes considered by using a two-dimensional quadric lattice photonic crystal structure to solve the problems of a multi-channel filter with structure complexity, single-wavelength download, and channel interference. The designed filter consists of a waveguide, reflection wall, multimode microcavity, and output port. Each port can download three different wavelengths. In the communication band from 1.500 to 1.600 μm, the transmittance of each channel is greater than 90%, and the filtering efficiency is high. The size of the non-simplified filter is only 27 μm × 17 μm. On the premise of ensuring low loss transmittance (that is, the transmittance of each port is changed by no more than 10% at the wavelength from 1.5–1.6 μm), the size of the filter can reach 15 μm × 7 μm. This design will greatly reduce the overall structure size of the filter and is suitable for multiplexing and demultiplexing in WDM systems.

Edge Doping Engineering of High-Performance Graphene Nanoribbon Molecular Spintronic Devices

We study the quantum transport properties of graphene nanoribbons (GNRs) with a different edge doping strategy using density functional theory combined with nonequilibrium Green’s function transport simulations. We show that boron and nitrogen edge doping on the electrodes region can substantially modify the electronic band structures and transport properties of the system. Remarkably, such an edge engineering strategy effectively transforms GNR into a molecular spintronic nanodevice with multiple exceptional transport properties, namely: (i) a dual spin filtering effect (SFE) with 100% filtering efficiency; (ii) a spin rectifier with a large rectification ratio (RR) of 1.9 ×106; and (iii) negative differential resistance with a peak-to-valley ratio (PVR) of 7.1 ×105. Our findings reveal a route towards the development of high-performance graphene spintronics technology using an electrodes edge engineering strategy.

TRIBOLOGICAL ASPECT OF ASSESSMENT OF EFFICIENCY OF FILTRATION USING MULTI-LAYER MATERIALS

This study presents the results of testing for the efficiency and effectiveness of filtration using multi-layer filter materials, and briefly presents a new technology for manufacturing filter media using these materials. The first part of the article describes the causes of the formation of impurities in operating fluids and the tribological effects of their impact. The second part is dedicated to testing for filtration efficiency and effectiveness for different filter materials. The third part of the article briefly describes the technology for manufacturing filter media using efficient but difficult-to-form materials. The testing results showed significant differences in filtering efficiency and effectiveness between the cellulose samples and the samples of filter materials based on glass microfibre layers. All of the tested multi-layer materials allow filtration effectiveness of over 90% to be achieved over the entire range of impurity sizes included in the experiment. The results of a comparative test for pressure change during filtration also indicate that glass microfibre materials have a considerably longer operating life than cellulose materials. The time after which a sharp increase in pressure occurs (due to the filter layer being filled with impurities) is nearly four times longer for multi-layer materials than for cellulose materials. The methods for cutting, forming, and joining filter materials have been developed by the author of this article and implemented at the EXMOT company.

Review of materials and testing methods for virus filtering performance of face mask and respirator

Respiratory protection devices such as face masks and respirators minimize the transmission of infectious diseases by providing a physical barrier to respiratory virus particles. The level of protection from a face mask and respirator depends on the nature of filter material, the size of infectious particle, breathing and environmental conditions, facial seal, and user compliance. The ongoing COVID‒19 pandemic has resulted in the global shortage of surgical face mask and respirator. In such a situation, significant global populations have either reused the single‒use face mask and respirator or used a substandard face mask fabricated from locally available materials. At the same time, researchers are actively exploring filter materials having novel functionalities such as antimicrobial, enhanced charge holding, and heat regulating properties to design potentially better face mask. In this work, we reviewed research papers and guidelines published primarily in last decade focusing on, (a) virus filtering efficiency, (b) impact of type of filter material on filtering efficiency, (c) emerging technologies in mask design, and (d) decontamination approaches. Finally, we provide future prospective on the need of novel filter materials and improved design.

Evaluation of firewall performance when ranging a filtration rule set

This article is a continuation of a number of works devoted to evaluation of probabilistic-temporal characteristics of firewalls when ranging a filtration rule set. This work considers a problem of the decrease in the information flow filtering efficiency. The problem emerged due to the use of a sequential scheme for checking the compliance of packets with the rules, as well as due to heterogeneity and variability of network traffic. The order of rules is non-optimal, and this, in the high-dimensional list, significantly influences the firewall performance and also may cause a considerable time delay and variation in values of packet service time, which is essentially important for the stable functioning of multimedia protocols. One of the ways to prevent decrease in the performance is to range a rule set according to the characteristics of the incoming information flows. In this work, the problems to be solved are: determination and analysis of an average filtering time for the traffic of main transmitting networks; and assessing the effectiveness of ranging the rules. A method for ranging a filtration rule set is proposed, and a queuing system with a complex request service discipline is built. A certain order is used to describe how requests are processed in the system. This order includes the execution of operations with incoming packets and the logical structure of filtration rule set. These are the elements of information flow processing in the firewall. Such level of detailing is not complete, but it is sufficient for creating a model. The QS characteristics are obtained with the help of simulation modelling methods in the Simulink environment of the matrix computing system MATLAB. Based on the analysis of the results obtained, we made conclusions about the possibility of increasing the firewall performance by ranging the filtration rules for those traffic scripts that are close to real ones.

Evaluation of filtration effectiveness of various types of facemasks following with different sterilization methods

Due to the ongoing pandemic, various types of facemasks such as certified N-95, non-woven fiber and fabric/textile masks are being used as an essential protective measure to reduce the risk of spread of the SARS-Cov-2 virus. The aerosols size-dependent filtration efficiency and breathing resistance of these masks were tested before and after sterilization by five different methods for two flow rates (20 and 90 L/min) conditions corresponding to regular breathing rate and moderate/strenuous exertion, in the particle size range 0.3–10 µm. Sterilization techniques used here are autoclaving (30 and 60 minutes), dry air oven heating (30 and 60 minutes), ionizing irradiation (15 and 25 kGy), hot water washing with and without detergent and immersing in a 10% concentration of liquid hydrogen peroxide for 30 minutes. Further, the filtration efficiency of each type of masks is also studied with laboratory generated two-order higher aerosol concertation. The certified mask has the most outstanding filtering efficiency among all the other type of facemasks. The ionizing radiation causes a significant reduction in filtration efficacy, so that it is not recommended for sterilization purpose. The best method to sterilize certified N-95 masks without affecting their performance is by using dry air heating with temperature ranging from 70–80 °C. The performance of the cloth and surgical masks is found to be comparable for both flow conditions. As an affordable sterilization method, hot water washing is recommended, which does not deteriorate the fabric masks efficiency and can be used by the common people. The recommended masks for the general people are textile/fabric masks which serves fit for the purpose than non-woven masks because it can help to reduce non-biodegradable waste (facemask) and prevent respiratory droplet transmission. The non-woven mask can be sterilized with dry heat, hot water wash and autoclave.

Comparison of the Filtration Efficiency of Different Face Masks Against Aerosols

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic can spread through virus-containing aerosols ( ≤ 5 μm) and larger airborne droplets. Quantifying filtration efficiency of different kinds of masks and linings for aerosols that fall within the most penetrating particle size (80-400 nm) is critical to limiting viral transmission. The objective of our experiment was to compare the “real-world” filtering efficiency of different face masks for fine aerosols (350 nm) in laboratory simulations.Methods: We performed a simulated bench test that measured the filtering efficiency of N95 vs. N99 masks with elastomeric lining in relation to baseline (“background”) aerosol generation. A mannequin head was placed within a chamber and was attached to an artificial lung simulator. Particles of known size (350 ± 6 nm aerodynamic diameter) were aerosolized into the chamber while simulating breathing at physiological settings of tidal volume, respiratory rate, and airflow. Particle counts were measured between the mannequin head and the lung simulator at the tracheal airway location.Results: Baseline particle counts without a filter (background) were 2,935 ± 555 (SD) cm−3, while the N95 (1348 ± 92 cm−3) and N99 mask with elastomeric lining (279 ± 164 cm−3; p <0.0001) exhibit lower counts due to filtration.Conclusion: The filtration efficiency of the N95 (54.1%) and N99 (90.5%) masks were lower than the filtration efficiency rating. N99 masks with elastomeric lining exhibit greater filtration efficiency than N95 masks without elastomeric lining and may be preferred to contain the spread of SARS-CoV-2 infection.

Concurrent statistical learning of target and distractor spatial probability collide on the same spatial priority map(s)

Statistical learning (SL) of both target and distractor spatial probability distributions adjusts the attentional priority of locations. In the presence of a single manipulation for each location, SL also induces indirect effects (e.g., changes in filtering efficiency due to an uneven distribution of targets), suggesting that SL-induced plastic changes are implemented within common spatial priority maps. Here we tested whether, when target- and distractor-related manipulations are concurrently applied to the very same locations, dedicated mechanisms might support the independent encoding of spatial priority in relation to the attentional operation involved. In three related experiments, human healthy participants discriminated the direction of a target arrow, while ignoring a salient distractor, if present; target and distractor spatial probability distributions were systematically manipulated in relation to each single location. Critically, the selection bias produced by the target-related SL was significantly reduced by an adverse distractor contingency. Conversely, the suppression bias generated by the distractor-related SL was erased, or even reversed, by an adverse target contingency. Our results suggest that independent and concomitant target- and distractor-related SL manipulations concur to the plastic adjustment of the same spatial priority map(s), with the resulting priority corresponding to some kind of weighted average of the SL processes.