Multilayer Filters Research Articles

Filtration of aerosols containing graphite nanoparticles or their mixture with water droplets on single and multi-layer fibrous filters

The dynamics of filtration efficiency during graphite nanoparticles aerosol filtration on fibrous filters was investigated. The influence of water droplets in feed gas on filtration efficiency, pressure drop as well as the form and shape of filtration deposits collected on filter was examined. Moreover, the mass distribution of collected deposits in individual layers in the case of multilayer filters was examined. We have observed that during the filtration of graphite aerosol in the presence of water droplets the observed pressure drop is significantly greater than during the filtration of sole graphite aerosol. On the other hand, the filtration efficiency is decreased in the presence of water droplets. During the filtration in multilayer filters we observed that the mass of particles deposited in upstream layer is greater than that in downstream, independently of the structure of both layers. This effect is also more significant in the presence of water droplets in feed gas.

Visual Tracking Via Multi-Layer Factorized Correlation Filter

Pruning the parameters of basis filters can effectively eliminate the negative effect of redundant deep features in discriminative correlation filter based trackers. However, traditional methods often treat feature maps in Convolutional Neural Networks (CNN) as isolate observations, ignore the intrinsic correlation between partially attentional feature maps in multiple convolutional layers, when basis filter pruning is pursued. In this letter, we propose a multi-layer factorized discriminant correlation filter (MLF-DCF) for visual tracking. By integrating the multi-view discriminant learning and the discriminative correlation filter into a unified optimization problem, we can explore the correlation between different target sub-regions from multi-layer viewpoint, thus can effectively prune multi-layer basis filters. To enhance the efficiency of MLF-DCF in terms of speed and accuracy, we not only adopt alternating direction method of multipliers (ADMM) to solve the unified optimization, but also employ a mask estimation strategy to eliminate the background noise in deep features. A large number of experiments on challenging video sequences are given to illustrate the superiority of our tracking method.

Generalized PEEC Model for Conductor–Dielectric Problems With Radiation Effect

In this article, a passive full-wave partial element equivalent circuit (PEEC) model is formulated for modeling electromagnetic (EM) problems with finite dielectrics. The proposed PEEC model is a substantial extension of the generalized PEEC model for problems of multiple conductors in free space. The proposed generalized PEEC model reflects the physical radiation mechanism of an EM problem with finite dielectrics. The radiation effects, both from conductors and dielectrics, are incorporated in real-valued frequency-dependent inductances and resistances, while capacitances remain to be frequency invariant. Consequently, the resultant circuit model of the proposed PEEC model is numerically verified to be more passive than the existing PEEC models. The minor passivity violation can be amended without altering the circuit configuration. To model a dielectric with the irregular-shaped surface, a triangular meshing scheme with Rao–Wilton–Glisson (RWG) basis is used. The generalized PEEC model provides a passive circuit model for both the frequency- and time-domain modeling of an EM problem with finite dielectrics. The passivity and accuracy of the generalized PEEC model are validated by an low temperature co-fired ceramic (LTCC) multilayer filter module, two dielectric resonator antennas, and a patch antenna.

Simulation of the process of water purification in multilayered micro porous media

The mathematical model of the process of adsorption purification of water from impurities in multilayer microporous filters is formulated. An algorithm for numerically-asymptotic approximation of solution of the corresponding nonlinear singularly perturbed boundary value problem is developed. The developed model allows to investigate the distribution of concentration of pollutant inside the filer.

Investigation of the multi-layer open cell foam filter model using numerical simulation and experimental studies

In this work, we studied the influence of the internal features of an open cell foam material structure on the efficiency of particle deposition and the pressure drop value of the medium. Constructing of the open cell foam filter models is based on the Distinct Element Method, which allows creating geometry with a random arrangement of pores in space. Calculations of the flow field and particle trajectories were performed using the ANSYS Fluent software package (v. 19.0). Experimental studies were conducted using samples created on the basis of the inverse matrix of 3D printed computational models. Also, models of various geometries with a fixed porosity of the medium are considered. Conducted numerical and experimental studies show that the filter model with the lowest porosity provides the highest deposition efficiency of particles. For a given fixed porosity of the medium, a filter with a change in the cells in diameter across the layers gives a lower value of the pressure drop, which is a significant advantage. The results can serve as the basis for creating aerosol filters with improved characteristics.

Multilayer triple band bandpass filter with a floating U-shaped SIR and split ring resonator

A multiple band bandpass filter (BPF) is designed using multilayer arrangement. The bandpass filter has three passbands having centre frequencies at 2.45 GHz, 4 GHz and 5 GHz. First a single band BPF is designed which includes a pair of coupled resonator and a split ring resonator in a multilayer arrangement. This geometry of the filter structure is studied and validated by fabrication and measurement. The initial single band filter structure is further improved to provide triple band BPF. All these bands are realized by a stub loaded U-shaped step impedance resonator (SLU-SIR). However, to improve the response of the second and third band a modified split ring resonator and a pair of open stubs are used. Each passband can be controlled individually. A mathematical analysis is done to study the proposed SLU-SIR using transmission line model. The proposed filter provides compactness and low insertion loss. A prototype is measured using vector network analyser (VNA) and shows a good matching with the simulated result.

Synthesis of single phase MgTiO3 and influence of Sn4+ substitution on its structural, dielectric and electrical properties

In this work, synthesis of single-phase MgTiO3 and Mg(Ti0.95Sn0.05)O3 ceramics through conventional solid state mixed oxide route using Mg(OH)2 or MgO as raw material was investigated. The phase purity of prepared specimens was examined using X-ray diffraction; bond characteristics were determined via Raman spectroscopy, dielectric properties at low frequency were measured by Impedance spectroscopy and dielectric properties at microwave frequency were measured by vector network analyzer. The properties of Mg(OH)2 based ceramics were also compared to that of MgO based ceramics in frequency range of 10 kHz-3 MHz and temperature range of 298–468 K. It was observed that Mg(OH)2 based materials exhibited not only low losses (tan δ) and low relative permittivity (ϵr) but also possessed smaller value of temperature coefficient of resonant frequency (τf) in comparison to that of MgO based materials. Dielectric and electrical properties of MgTiO3 were further improved by partial replacement of tetravalent cations Ti4+ with Sn4+. The mechanism of electrical conduction for the synthesized specimens was also studied using Jonscher power law and activation energy was evaluated using Arrhenius equation. Best dielectric properties at room temperature in 10 kHz-3 MHz frequency range were displayed by Mg(OH)2 based Mg(Ti0.95Sn0.05)O3 compound having tan δ of 2.32 × 10−4, ϵr of 14.61 and τf of −39.7 ppm/K at 100 kHz frequency. At 15 GHz Mg(OH)2 based Mg(Ti0.95Sn0.05)O3 exhibited tan δ of 2.73 × 10−2 and ϵr of 14.12. This material could be utilized for fabrication of multilayer capacitors, dielectric resonators, filters, antennas, buffer layers and protective coatings.

Polymer/MOF-derived multilayer fibrous membranes for moisture-wicking and efficient capturing both fine and ultrafine airborne particles

Particulate matter (PM)-induced air pollution has become a serious threat to public health in many regions. There is, therefore, a need for development of advanced respirator materials that can efficiently capture PM and also exhibit both low breathing resistance and good moisture wicking properties to ensure physiological comfort of the wearers. Herein, we report a new type of multilayer membranes that exhibit excellent filtration efficiencies for PM of various sizes, low air resistance and good directional moisture transport properties. We incorporated a type of metal-organic framework, ZIF-8, into polyacrylonitrile (PAN) to prepare microfibers with high surface roughness, and alternatingly stacked layers of rough microfibers with layers of PAN nanofibers via electrospinning, resulting in multi-level structured membranes. Moreover, subsequent acid and base treatments could not only tailor the hydrophilicity of fiber surfaces, but also induce multiscale surface roughness, facilitating both moisture wicking and PM adsorption. This allowed us to construct a unique multilayer membrane composed of a super-hydrophilic outer layer made of PAN fibers with multiscale surface roughness, a hydrophilic composite intermediate layer consisting of porous PAN-ZIF-8 microfibers and PAN nanofibers, and a hydrophobic polystyrene fibrous inner layer, which could offer excellent directional moisture transport performance and a high water vapor transmission rate of 10.56 kg m−2 d−1 due to strong capillary force and push-pull effect. More importantly, benefiting from the large specific surface area, rough fiber surface, and hierarchical pore structure, the membrane exhibits high removal efficiencies of 99.973% for 0.3-μm particles and ≧99.99% for particles of other sizes, including the more harmful ultrafine particles, at a low pressure drop of 80.1 Pa. Moreover, the multilayer composite filter still maintains a high removal efficiency of 99.951% after continuous air purification for 48 h in a high PM2.5 concentration (>300 μg m−3) environment. These make such membranes promising high-performance filtration media for respirator applications.

Комп’ютерне прогнозування адсорбційної доочистки води від домішок у швидких багатошарових фільтрах конусоподібної форми

In the paper а mathematical model for computer predicting of the process of adsorption purification of water from impurities in rapid multilayer filters while maintaining a constant filtration rate, taking into account the reverse influence of process characteristics (the concentrations of impurities respectively in the filtration flow stream and on the surface of the adsorbent load, the temperature of the filtration flow) on characteristics load (coefficients of filtration, active porosity, adsorption, desorption) is formulated. The corresponding model problem contains the equation of motion of the filtration flow according to Darcy's law, the continuity equation, the equation of mass and heat balance, and the equation to study the change in the characteristics of piecewise-homogeneous porous loads (filtration coefficients and active porosity). Provided that the convective components of heat and mass transfer and adsorption predominate over the contribution of diffusion and desorption, an algorithm for numerically-asymptotic approximation of solution of the corresponding nonlinear singularly perturbed boundary value problem for a model region of a conical shape, bounded two equipotential surfaces and a surface flow, separated by some given specified of the equipotential surfaces on several subdomains, is developed. The proposed model allows through computer experiments to investigate changes in the characteristics of piecewise homogeneous porous loads (coefficients of filtration and active porosity of filter materials in each layer), to predict the optimal use of adsorbents and increase the duration of operation of filters by selecting their shape and height influence on the process of adsorption purification of water not only changes in the filtration flow rate along the height of the filter, but also the temperature.

Effect of ethanol plant extracts on Staphylococcus Epidermidis, Staphylococcus Aureus

The emergence of multiresistant strains of Staphylococcus epidermidis, Staphylococcus aureus that are difficult to antibiotics and cause severe lesions of soft tissues, sepsis, and complicated surgical pathology are recognized as the one of problems of current infectious diseases of animals and humans. One of challenges in pharmacognosy is the search for alternative sources of antibacterial substances with an exhaustive resource of antibiotics of fungal origin. The use of raw medicinal plants is quite promising in this regard. The tendency of scientific research of recent decade reveals a promising range of plants of a number of families, which typically contents certain active substances (phytoncides, saponins, alkaloids, glycosides, tannins, essential oils etc.).
 The goal of the work was to establish the antibacterial effect of plant infusions on reference cryogenic strains of Staphylococcus epidermidis, Staphylococcus aureus in vitro.
 Herbal material of 50 species (seeds, grass, shoots, leaves, compound fruit, peel) obtained at different periods of the growing season was used for investigation. The material was classified, dried, and grounded. Samples of 1 g were poured with 5 cm3 of 96 % ethanol and were kept it over three weeks in a dry cold place. The obtained alcohol infusion was filtered with sterile multi-layer gauze disc filters. Before the discs were put on the surface of agar with inoculation of the corresponding culture, they were dried in a sterile laminar box under ultraviolet rays. Antibacterial activity of various tinctures was determined by the disk diffusion method in agar with the measurement of the diameter of the growth suppression zone of the culture using a template ruler.
 Concerning the above mentioned point, herein, we report the results of the use of tinctures Staphylococcus epidermidis, Staphylococcus aureus in vitro. Obtained data has been systematized, summarized and evaluated.
 The paper presents the results of the effectiveness of phytopreparations on Staphylococcus epidermidis, Staphylococcus aureus in vitro. The antibacterial effect of plant tinctures of Cephalotaxus harringtonia, Hedera helix, Geranium sanguineum on cryogenic strains Staphylococcus epidermidis, Staphylococcus aureus. We consider it possible to recommend the investigated extracts of Cephalotaxus harringtonia, Hedera helix, Geranium sanguineum for further research in the fight against polyresistant strains of the above-mentioned microorganisms.
 The obtained results give grounds to recommend herbal tinctures to combat multi-resistant strains of Staphylococcus epidermidis, Staphylococcus aureus.

Development, synthesis and production of multilayer thin-film filters for infrared sensors for monitoring of flammable gases and vapors of flammable liquids

We present the results of development and production of multilayer thin-film filters for infrared sensors for monitoring of flammable gases and vapors of flammable liquids. This paper addresses technological peculiarities of their production. A theoretical simulation of multilayer filter parameters to provide the transparency in wavelength range 3.3 - 3.5 μm was carried out. It is demonstrated that spectral characteristics of produced multilayer filter correspond to the calculated ones.

Zeolite and short-cut fiber-based wet-laid filter media for particles and heavy metal ion removal of wastewater

As development of industrialization grows constantly, the purification of hazardous solid particles and ions is one of the most important topics in environment and ecosystem. In this report, we designed and developed a novel and advanced type of filter media for the removal of both solid particles and hazardous ions, we choose Cs+ and Ca2+ here, by enclosing zeolite in wet-laid nonwoven media. The performance of the prepared filter media was evaluated by continuous sorption experiments, which were followed by solid particles and ion-removal efficiency studies. The prepared filter media showed excellent uniformity. The prepared filter media exhibited a solid removal efficiency rate which ranged from 80 to 82%, and the initial removal efficiency of ions exceeded 99%. These values are in effect as the main layer in the completed liquid filter media and for the next step to prepare the completed multi-layered liquid filter units. The results here suggest that this novel filter media can be used in high-efficiency and multi-functional liquid filter units for residential and industrial engineering.

Tuning filtering properties of SnS films deposited on Glass/ITO substrate using glancing angle deposition technique

In the present work, for the first time, a multilayer filter comprised of Tin sulfide (SnS) and Indium tin oxide (ITO) coated glass has been fabricated using physical vapor deposition (PVD) method. The ITO coated glass slide (as a commercial substrate) is situated at the bottom portion of the filter on which a SnS film is deposited that acts as a window layer. The consecutive use of these films leads to the interference phenomenon. Furthermore, the deposition of SnS film, as the window layer on the Glass/ITO substrate, has been engineered using glancing angle deposition (GLAD) technique that has remarkably resulted in diffraction phenomenon. As a result, to find the optimum deposition angle, SnS films have been prepared at incident flux angles of 0°, 45°, and 65° using GLAD technique. Then the structural and morphological properties of the samples were studied by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Atomic Force Microscopy (AFM) techniques. More importantly, the optical properties including transmittance spectrum and absorption coefficient of the samples were investigated by UV-NIR spectrophotometer in the wavelength range of 500–2500 nm. The obtained results have shown improvement in the filtering properties of as-prepared filter upon increment of the deposition angle. The filtering properties are attributed to the interference and diffraction phenomena because of the multilayer structure having different refractive indices and an oblique layer applied by GLAD technique, respectively. Moreover, the filter produced at normal vapor incidence only transmits the infrared spectrum, while a shift towards lower wavelengths is observed upon applying the deposition angle of 65°. This sample is introduced as an appropriate filter in the visible spectrum because of being transparent only in certain wavelength range (800–1400 nm).

Theoretical Design of an Antireflection Coating for near Infrared Region (800-1500 nm) for glass substrate

The main purpose of this research is to design multilayer filter that can permit the IR wavelength (800-1500 nm), to make the aim of the research comes true, the equations of multilayer system have been derived and developed, and then a program code has been made using FORTRAN language. The films thicknesses of the multilayer could be even quarter wavelength or unlimited The research results illustrated that the best design when the stack number equals to(6).

Wideband balun filtering quasi‐Yagi antenna with high selectivity

AbstractA compact wideband balun filtering quasi‐Yagi antenna with high selectivity is proposed. It consists of a quasi‐Yagi antenna integrated with a multilayer balun filter. The quasi‐Yagi antenna is composed of a bow‐tie driver coupled with a director on the top layer, and a ground reflector on the bottom layer. The fourth‐order balun filter has two stepped impedance resonators (SIRs) on the top layer, and two SIRs on the middle layer, which helps improve the frequency selectivity and bandwidth. Moreover, it has two differential ports to feed the quasi‐Yagi antenna. The filtering antenna centered at 2.5 GHz with a wide bandwidth of 22.8% and a pair of transmission zeros is designed and fabricated, which shows a stable radiation pattern with maximum gain of 5.5 dBi and high selectivity.

Modelling of the technological process of multiple filtering suspensions with multi-layered filter

Although a technological process of filtration with multi-layered filters is well-known in industry (purification of such liquid solutions as spinning solutions, liquid fuels, drinking liquids, pharmaceuticals, etc.), very few studies have systematically quantified its mechanism, and even less have characterized the affect of its parameters on operating costs and the quality of the final product. In this study, there was developed a mathematical model of multiple filtration of suspensions with multi-layered filter, a computational algorithm for solving the problem as well as software for carrying out computational experiments. The developed mathematical software allows to carry out many-sided study and forecast the technological process of filtration in order to make appropriate management decisions.

Compensating porosity gradient to produce flat, micromachined porous silicon structures

Abstract Obtaining flat micromachined porous silicon structures is extremely challenging due to the myriad of factors affecting film stress in such structures. In this work, the relationships between the current control during anodization, average porosity, and residual stress within porous silicon thin films and micro-fabricated structures were investigated. Using a combination of electron microscopy, surface profilometry and reflectance spectroscopy, the optimum conditions to produce near zero residual stress in thin films and micro-fabricated structures were determined. The residual stress was adjusted by a continuous variation of the anodization current in order to achieve flat structures. The flattest released porous silicon microbeams were 2.3 μm thick with a peak to valley height variation of only 72 nm over a length of 150 μm. These were achieved by using an initial current density of 20 mA/cm2 that was reduced down to 8 mA/cm2 during anodization. By using this method of reducing the current during anodization, the inherent high porosity at the porous-silicon/silicon interface was reduced, which also enabled a 36% increase in the film thickness before film delamination compared with using a constant current. These results provide a pathway to fabricate thick, optically flat micromachined multi-layer filters using a single base material (silicon) for the structural and released layers.

Multilayer angular optical filter as a smart window

The ability for controlling the light based on the angle of incidence played an essential role in many technological applications. In the present work, an angular optical filter consists of multilayers designed by Essential Macleod software within the visible and near-infrared regions. By using the transfer matrix method, we have obtained the transmission properties for the p-polarized light depending on the angle of incidence. The proposed filter can be easily used to control the transmission of visible and NIR light depending on the angle of incidence. Transmission of NIR at 1200 nm increases from 21.26 to 78.89% as the incident angle changed from 5° to 55°, respectively. Simultaneously, the transmission of the visible light is higher than 87%. These results may have a potential application in controlling the light and heat within the building, solar greenhouse, optical switch and other future applications. Also, the simplicity of the current structure makes it conducive to the industrial design using low-cost and massive product nanofabrication technique.

Solution Blow Spinning (SBS) Nanofibers for Composite Air Filter Masks

Particulate matter (PM) pollution in the air has become a serious environmental issue that has demanding requirements for the fabrication of new materials. In this study, three different types of nanofiber materials (i.e., cellulose diacetate (CDA), poly(acrylonitrile) (PAN), and poly(vinylidene fluoride) (PVDF)) produced from solution blow spinning were used in composite multilayered filter masks, and their filtration performance for particulate matter of at least 2.5 μm in size (PM2.5) was evaluated. PM2.5 capture efficiency and nanofiber filter pressure drop were tested using the fabricated set-up with simulated burnt cigarette smoke as a source of PM2.5. Filter mask performance using different nanofiber materials was evaluated through their corresponding quality factors (QF). Among the three nanofibers tested, PAN nanofiber has the highest filtration performance with a quality factor of 0.05 Pa–1 and acceptable air permeability. PVDF has the lowest air filter quality among all the nanofibers studied, ...

Fabrication of Al2O3/SiO2 multilayer reflective filters with excellent uniformity for demanding optical interference filters

In this work, we report the fabrication of a high reflective filter with excellent uniformity for demanding optical interference filters. To achieve this, films were deposited in different batches at three different angular positions using electron beam deposition technique. The coatings were carried out using indigenously designed flat jig holder without shapers. Fourteen alternating layers of high and low refractive index films were deposited on BK7 substrates of dimensions 186 × 150 mm by using aluminum dioxide (Al2O3) and silicon dioxide (SiO2) evaporation grade granuals. Individual layers in the stack were deposited at quarter wave optical thickness at a wavelength of 550 nm. To examine the optical properties of multilayer optical films, Gonio-spectrophotometer was used. Roughness and thickness of all the samples were evaluated using Stylus Profilometer and Coherence Correlation interferometer. Surface properties such as wettability, adhesion and hardness were studied. Additionally, to investigate the change in chemical bonding and structural properites of the coating materials used for evaporation before (bulk powdered material) and after deposition of thin films (material left in the crucible after deposition process), FTIR and XRD studies were carried out.