Quality Factor Of Filter Research Articles

A coalescing filter with hybrid structure of oleophilic/oleophobic media by centrifugal spinning

To address the issue of significant pressure drop in coalescing filters caused by liquid film phenomena, we employed centrifugal spinning to fabricate a novel hybrid fibrous filter with an interlaced structure of oleophilic/oleophobic fibers. The unique hybrid structure of the filter greatly enhances its ability to suppress the formation of liquid films and improves coalescence performance. Compared to both commercial filters and Janus filters, the hybrid filter exhibits a lower pressure drop increase ratio of 3.32 at the saturation stage, as opposed to Janus filter’s 13.95. Additionally, the quality factor of the hybrid filter reaches 9.8 kPa−1, which is significantly higher than Janus filter’s 2.54 kPa−1. This paper presents a new approach for enhancing coalescence performance.

Experimental design for determining the factors influencing the filtration efficiency of solution-blown spun polylactic acid filters

Millions of people are wearing face masks because of the COVID-19 epidemic, and these masks are indiscriminately releasing pollutants into the atmosphere. One of the most appealing and promising bio-based polymers for face masks is polylactic acid (PLA). Solution-blown spinning (SBS) is a rapid and easy way to produce micro and nanofibers that may be quickly deposited on any substrate. This study aims to produce and evaluate solution-blown spun PLA fibers used as filter media. PLA nanowebs were observed for their morphology, weight, thickness, air permeability, water contact angle, and filtration properties. The average diameter of the fibers ranged between ∼163 and ∼282 nm. NaCI aerosol filtration test results showed that the filtration efficiency of these nanowebs was ≥ 94% and the pressure drop was ≤ 240 Pa, meeting requirements was assigned to the class EN 149: FFP2 particle-filtering half-maks. Filtration performance was significantly influenced by the flow rate and polymer concentration. The resulting equations for the design of experiments (DoE) regression model were examined and found to be appropriate for predicting the parameter combinations required for the desired quality factor of PLA filters. The fast and economical features of the SBS process, as well as the biodegradable nature of the PLA polymer, may considerably contribute to the development of environmentally friendly filters.

Theoretical and experimental study for enhancement of filtration performance of nonwoven fibrous media by nonuniform compression

In this study, the effect of uniform and nonuniform compression on the quality factor of filtration of nonwoven fibrous media has been investigated theoretically and experimentally. Given that the effect of nonuniform compression on filtration has not been reported, it is a new way for enhancement the performance of filters. The “quality factor”, which includes filtration efficiency and pressure drop, has been used to compare different types of filter media compression. Theoretical calculations have been performed using the classical single fiber efficiency theory. The results showed that with compression, the filtration efficiency increases only for a range of particle sizes. Experiments were carried out on 10 polypropylene fibrous filters with different compression ratios and types. For each sample, the efficiency and pressure drop were measured. It was found that the trend of changes in filtration efficiency due to compression is the same for the theoretical and experimental results. The experimental of uniform and nonuniform compression results showed that the filtration efficiency increases only for particles smaller than 3 μm. For particles smaller than 3 μm, the effect of compression on increasing efficiency increases. The increase is lower in nonuniform compression because some particles can escape from uncompressed spaces. Due to the lower pressure drop in nonuniform compression an increase in the quality factor is achieved in comparison to the uniform compression. The increase in the quality factor of the PP1 filter is up to 25.83%, and for the PP2 filter is up to 25.93%. It was also observed that with the increase of the compression ratio, the quality factor of the filter decreases.

A reconfigurable floating-gate-transistor-capacitor filter for analog signal processing

This paper introduces a fully reconfigurable floating-gate-transistor-capacitor (FGT-C) filter that exhibits compactness and power efficiency. The proposed filter incorporates a biquadratic section, enabling the generation of lowpass (LP) and bandpass (BP) outputs with adjustable filter parameters, including gains, natural frequency, quality factor, and DC levels for input and output signals. Moreover, the FGT-C filter topology demonstrates a modular structure, facilitating easy cascading and scalability of the biquadratic sections to implement high-order frequency responses. A prototype chip has been fabricated in the 0.35 μm CMOS process, where each biquadratic section occupies an area of 0.0313 mm2. The chip measurements were conducted with a supply voltage of 1.8 V and both output voltage levels programmed at 0.9 V. The biquadratic FGT-C filter exhibits a power consumption of 118.4 nW and achieves a spurious free dynamic range of 43 dB in a 10 kHz bandwidth setting. It is suitable for low-power analog signal processing in large-scale field programmable analog arrays.

Single-Layer and Double-Layer Filtration Materials Based on Polyvinylidene Fluoride-Co-hexafluoropropylene Nanofibers Coated on Melamine Microfibers.

In this work, we demonstrate selected optimization changes in the simple design of filtration masks to increase particle removal efficiency (PRE) and filter quality factor by combining experiments and numerical modeling. In particular, we focus on single-layer filters fabricated from uniform thickness fibers and double-layer filters consisting of a layer of highly permeable thick fibers as a support and a thin layer of filtering electrospun nanofibers. For single-layer filters, we demonstrate performance improvement in terms of the quality factor by optimizing the geometry of the composition. We show significantly better PRE performance for filters composed of micrometer-sized fibers covered by a thin layer of electrospun nanofibers. This work is motivated and carried out in collaboration with a targeted industrial development of selected melamine-based filter nano- and micromaterials.

Performance of finite-size metal-dielectric nanoslits metasurface optical filters.

In this work, we analyze the performance of finite-size metal-dielectric nanoslits guided mode resonance metasurface optical filters by using finite-difference time-domain simulations and spatial Fourier transform analysis. It is shown that in the direction of the nanoslits period, the critical size required to maintain the performance of the corresponding infinite size filter is the product of the nanoslits period and the quality factor of the infinite size filter. Size reduction in this dimension below the critical dimension reduces the peak transmittance and broadens the spectral linewidth of the filter. In the dimension orthogonal to the nanoslits period direction, the critical dimension size required is not related to the quality factor of the corresponding infinite size filter. Our analysis shows that the critical size is 12 times the filter peak wavelength in the orthogonal dimension for maintaining the filter performance. The 12 times filter wavelength requirement corresponds to the second zero of the Fourier transform of the aperture function.

Enhanced filtration characteristics of a PTFE foam-coated filter using PTFE nanofibers

Polytetrafluoroethylene (PTFE) is a bag filter material with limited options for fiber production methods because of its high melt viscosity. In this study, a new method for fabricating a PTFE composite filter with high filtration performance was proposed. PTFE nanofibers produced by electrospinning, were coated on the surface of the PTFE foam-coated filter, and heat-treated, resulting in the fabrication of PTFE composite filter. The optimal conditions for preparing PTFE nanofibers with a uniform fiber distribution were determined using a systematic approach. A uniform fiber morphology of the electrospun fibers was prepared by controlling the PTFE-Polyvinyl alcohol (PVA) mixing ratio and the electric field strength, and pure PTFE fibers were obtained by heat-treatment at an optimal temperature based on TGA, DSC, and FT-IR analyses. The filter quality factor of the resultant PTFE composite filter, which represents the filtration performance, was approximately twice that of the PTFE foam-coated filter for all particle sizes. Furthermore, the cleaning cycle and cleaning efficiency of the PTFE composite filter improved by 9% and 3.9–5.4%, respectively, compared to those of the PTFE foam-coated filter, which was closely related to high contact angles of water and oil.

0.5 V Multiple-Input Multiple-Output Differential Difference Transconductance Amplifier and Its Applications to Shadow Filter and Oscillator

This paper presents new applications of low-voltage and low-power multiple-input multiple-output differential difference transconductance amplifier (DDTA). The multiple-input bulk-driven MOS transistor (MIBD MOST) technique provides multiple-input of the active device that simplifies the application’s topology and reduces its power consumption. The proposed DDTA has been used to realize multiple-input single-output shadow filter. Both voltage- and transimpedance-mode filtering functions can be obtained. The natural frequency and the quality factor of the shadow filter can be independently and electronically controlled using DDTA-based amplifiers. The proposed shadow filter has been modified to work as a shadow oscillator. The condition and frequency of oscillation can be controlled independently and electronically. The DDTA is capable to work with 0.5V supply voltage and consumes 218.2 nW. The applications have been designed and simulated in Cadence using 0.18μm TSMC CMOS technology.

Modeling of surface roughness in deeply etched photonic MEMS mirrors and filters

We study the impact of the surface roughness on the response of deeply etched silicon Bragg mirrors and resonators. The transfer matrix method is extended to account for the roughness in multilayered systems. The model is first verified numerically using the finite difference time domain (FDTD) method for surface roughness values up to 80 nm at a wavelength of 1550 nm. The response of the mirrors and filters having an RMS roughness of 30 nm is calculated by the developed model and compared with the numerical results of the FDTD results, and it shows a good agreement. Then the model results are compared with the experimental data of a Bragg mirror and filter, fabricated by the deep reactive ion etching Bosch process of silicon on an insulator wafer; they show a very good agreement in the insertion loss and 3-dB bandwidth due to the roughness model. Finally, the transmission, 3-dB bandwidth and quality factor of the optical filters based on single, double, and triple silicon layer mirrors are examined using the model and accounting for Gaussian beam excitation. The presented model can be used to guide the requirements on the fabrication quality of optical surfaces and the choice of the optimum number of layers.

Optimized pleat geometry at specific pleat height in pleated filters for air purification.

The performance of an air purifier is determined by its clean air delivery rate (CADR), expressed as the product of the air flowrate and filter collection efficiency. A high CADR in a commercial air purifier is achieved using a pleated air filter with high filtration performance at a given air flowrate. However, obtaining this high filtration performance depends on the knowledge of the manufacturer, including the optimal pleating design, which remains uncertain to date. In this study, test pleated filters were prepared by folding a flat electrostatically-charged E12 filter medium to obtain different pleating geometries. The proper pleat geometry of the pleated filter, which has a minimum pressure drop at a fixed air flowrate, was dependent on the pleat length (PL ) and pleating ratio (α=pleat height/pleat width), wherein as the PL increases, the α range required to achieve a minimum pressure drop similarly increases. Based on the filter quality factor (qF ), the optimal pleat geometry of a pleated filter was between α values of 6-8, irrespective of the PL . Although both PL and α have certain influences on the qF , α has a greater influence on the pleated filter with no dead zone.

MTMS-based aerogel structure deposition on polypropylene fibrous filter – Surface layer effect and distribution control for improvement of oil aerosol separation properties

Polypropylene non-woven material with fibres surface modified with methyltrimetoxysilane(MTMS)-based aerogel structure exhibits increased affinity to oil and highly developed collector area, which translates to enhanced oil mist filtration performance, crucial in automotive, commercial and home appliances. This article indicates the filtration improvement ability's dependence on the aerogel structure's deposition and morphology, as previous work raised some critical questions related to surface vs volume deposition's contribution to filtration properties. Modified and native materials were studied on a filtration test bench and via a systematic wettability investigation. The amount of aerogel structure deposit is correlated to the MTMS concentration, and its distribution relay on condensation kinetics, controlled by the catalyst addition rate during the sol-gel process. Though beneficial for separation efficiency improvement, the aerogel structure deposition in filter volume is accompanied by a surface foil layer formation that needs to be removed as it causes up to 200 Pa airflow resistance. The controlled aerogel structure deposition method gave satisfactory results, increasing separation efficiency for most penetrating droplets four times and increasing filter Quality Factor. Modified material is competitive in terms of separation efficiency and airflow resistance with those obtained in the other related works on the subject, giving a post-production method for oil aerosol filter enhancement.

The Simulation and Design of an On-Chip Superconducting Millimetre Filter-Bank Spectrometer

Superconducting on-chip filter banks provide a scalable, space saving solution to create imaging spectrometers at millimetre and submillimetre wavelengths. We present an easy to realise, lithographed superconducting filter design with a high tolerance to fabrication error. Using a capacitively coupled lambda /2 microstrip resonator to define a narrow (lambda /Delta lambda = 300) spectral pass band, the filtered output of a given spectrometer channel directly connects to a lumped-element kinetic inductance detector. We show the tolerance analysis of our design, demonstrating <11% change in filter quality factor to any one realistic fabrication error and a full filter-bank efficiency forecast to be 50% after accounting for fabrication errors and dielectric loss tangent.

Boosting the Quality Factor of the Shadow Bandpass Filter

This paper proposes a new method to increase the quality factor of the shadow bandpass filter. The proposed circuit topology is simple, with the use of conventional biquad cell along with external amplifiers. The major advantageous feature is that the quality factor of the filter is boosted up whereas the gain of the external amplifier is significantly reduced. Moreover, the presented idea can be applied to the shadow filter in both current and voltage modes. The proposed scheme is justified via circuit performance. The performance is compared with the previous research works in the same arena. The results show that a feedback signal and a properly chosen gain incredibly boost up the quality factor of the shadow bandpass filter. Simulations by PSpice using 0.18-[Formula: see text]m CMOS-level parameters confirm the validity of the proposed work.

Coupling Matrix-Based Co-Design of Filter-Oscillators

This letter presents a methodology of designing integrated filter-oscillators using the coupling matrix technique. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N + 4$ </tex-math></inline-formula> coupling matrix is developed for the first time to describe the filter-oscillator topology. Accordingly, the corresponding group delay, loop gain, loop phase, and complex quality factor of the feedback filter can be calculated using the matrix. This helps rapidly predict oscillating frequencies at group delay or complex quality factor peak frequencies to achieve lower phase noise. Moreover, since the transistor and the transmission line (TL) entries are incorporated in the coupling matrix, the physical geometries can be directly determined, resulting in improved design efficiency. Two third-order filter-oscillators are implemented at 2.91 GHz (group delay peak) and 3.15 GHz (complex quality factor peak) frequencies, respectively. The developed filter-oscillators are measured with −121 and −145 dBc/Hz phase noise at 1-MHz offset frequency, validating this coupling matrix-based co-design approach.

Auditory filter shapes derived from forward and simultaneous masking at low frequencies: Implications for human cochlear tuning

Behavioral forward-masking thresholds with a spectrally notched-noise masker and a fixed low-level probe tone have been shown to provide accurate estimates of cochlear tuning. Estimates using simultaneous masking are similar but generally broader, presumably due to nonlinear cochlear suppression effects. So far, estimates with forward masking have been limited to frequencies of 1 kHz and above. This study used spectrally notched noise under forward and simultaneous masking to estimate frequency selectivity between 200 and 1000 Hz for young adult listeners with normal hearing. Estimates of filter tuning at 1000 Hz were in agreement with previous studies. Estimated tuning broadened below 1000 Hz, with the filter quality factor based on the equivalent rectangular bandwidth (QERB) decreasing more rapidly with decreasing frequency than predicted by previous equations, in line with earlier predictions based on otoacoustic-emission latencies. Estimates from simultaneous masking remained broader than those from forward masking by approximately the same ratio. The new data provide a way to compare human cochlear tuning estimates with auditory-nerve tuning curves from other species across most of the auditory frequency range.

Additively manufactured multiplexed inertial coalescence filters

Multiphase flows often pose a significant challenge to the efficient and reliable design of thermofluidic systems. This paper describes multiplexed inertial coalescence filters composed of parallel helical pathways, designed to capture fine droplets (<40 µm) through inertial separation while maintaining a low pressure drop (<400 Pa). Filtration efficiencies for 7 µm and 30 µm droplets were characterized for varying flow conditions, with complete capture observed above a threshold flow rate. Models for filtration efficiency and pressure drop were developed and validated against experimental results to allow system design and optimization, enabled by the tunable additive manufacturing approach used to fabricate the filters. Filter quality factor was computed for varying droplet sizes, showcasing exceptional quality factor when compared to state-of-the-art filters documented in the literature. This multiplexed inertial coalescence filtration approach could find use in dehumidification systems, fog harvesting, chemical reactors, and microgravity droplet capture.

Analysis and Design of a CMOS LNA With Transformer-Based Integrated Notch Filter for Ku-Band Satellite Communications

A transformer-based notch filter is proposed in this article. The notch filter is integrated into a three-coil transformer in the matching network. While the primary coil and the secondary coil build a magnetically coupled resonator (MCR) and transfer the in-band signal to the next stage, the tertiary coil is coupled with the primary coil to absorb the interferers. Resonating with the switched capacitors, the notch frequency can be tuned digitally. A cross-coupled pair can further enhance the quality factor of the tank and, therefore, the rejection level. A low-noise amplifier (LNA) for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band satellite communication with the proposed notch filter is implemented in 65-nm CMOS to verify the theory. The LNA achieves a measured power gain of 19.5 dB at 12.2 GHz with a −3-dB bandwidth of 9.2–12.7 GHz. The LNA can achieve 13.5-dB gain suppression at 13.9 GHz. The suppression level can be enhanced by tuning the quality factor of the active notch filter, which consumes up to 0.6 mW. The noise figure (NF) is 2.3 dB at 10.6 GHz and the NF is below 2.7 dB from 9.2 to 12.7 GHz. The input return loss is better than −15 dB from 8.8 to 18.5 GHz. The LNA consumes 5.9 mW from a 1-V supply. The whole chip occupies an area of 1000 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 800\,\,\mu \text{m}^{2}$ </tex-math></inline-formula> .

Harmonic Mitigation by Optimal Allocation of Tuned Passive Filter in Distribution System

The purpose of this work is to determine the appropriate allocation of a single tuned passive filter “STPF” in a real distribution network at Tala city to prevent harmonic distortion caused by nonlinear loads. This design will cover the ideal filter parameter as well as the best filter position. The filter design is based on single and multi-objective functions that optimize the cost of the proposed filters, real power losses, total harmonic distortion “THD,” and individual harmonic distortion “IHD”. Upper and lower limitations for filter parameters, quality factor, voltage and harmonic distortion limits are determined using inequality constraints. This will be done under the equality constraint of power balance. The challenge of optimization is solved using two modern algorithms, jellyfish optimization technique “JFOT” and arithmetic optimization algorithm “AOA”, in which the placements of the filters and their parameters are selected. IEEE 33-bus radial system and an actual system as a part of the Egyptian network at Tala city are used for demonstrating the results obtained by the proposed techniques. The results reveal that the system’s harmonic distortion of current and voltage is reduced less than the limitations of the IEEE 519 standards.

Particulate matters filtration by a filter medium with pin holes: modeling and experimental verification

Air filtration systems have difficulty avoiding problems of leakage and breakage of the filter medium, which aggravates the emission of dust particles. In this study, a numerical calculation model is established to study the dust-laden air filtration performance of a filter medium with pin holes. The calculation model is verified using experiments and by comparing the values of the filtration resistance and efficiency. The results demonstrated that, with the existence of leakage, the filtration efficiency decreased with time, decreased with an increase in the leakage ratio, and increased first and then decreased with an improvement in the filter medium accuracy. An extremely high filter medium accuracy was not conducive to improve the filtration efficiency, but it obviously increased the filtration resistance. The larger the leakage ratio, Lr, the smaller the optimal filter accuracy, eF,opt, and the maximum filtration efficiency, eT,max. The functional relationships between eF,opt, eT,max and Lr, as well as QT, were obtained. With an increase in the leakage ratio, the filtration resistance and its rising rate decreased. The system quality factor decreased with the increase of the leakage ratio and increased with the increase of the filter quality factor.

Assessment of Chemical Fiber Air Filter for General Ventilation

Air filters for general ventilation have mainly been used to control the concentration of indoor particulate matter. In this study, the pressure differential, test dust capacity, quality factor and operating life of class F8 pleat–plate and multi-bag type chemical fiber filters were evaluated using an air filter performance test system. The results showed that the resistance increase rate of multi-bag filter (0.49 Pa/g·(cm/s)) was lower than that of pleat–plate filter (1.94 Pa/g·(cm/s)), the quality factor of the multi-bag filter was lower than that of pleat–plate filter, and the dust capacity of the multi-bag filter was much higher than that of the pleat–plate filter. The operating life of the multi-bag filter was 8 times as that of the pleat–plate filter with the measured PM2.5 of outdoor. The energy consumption of the pleat–plate filter was 2.2 times that of the multi-bag filter. Analyzing the electron microscope photos after dust loading, the dust depth of pleat–plate filter into filter material was thinner than that of multi-bag filter. The research results could provide data support for the design optimization and selection of ventilation filters and the treatment of the particulate matter in indoor environments.