Separable Filters Research Articles

Delving Deeper into Anti-Aliasing in ConvNets

Aliasing refers to the phenomenon that high frequency signals degenerate into completely different ones after sampling. It arises as a problem in the context of deep learning as downsampling layers are widely adopted in deep architectures to reduce parameters and computation. The standard solution is to apply a low-pass filter (e.g., Gaussian blur) before downsampling (Zhang in: ICML, 2020). However, it can be suboptimal to apply the same filter across the entire content, as the frequency of feature maps can vary across both spatial locations and feature channels. To tackle this, we propose an adaptive content-aware low-pass filtering layer, which predicts separate filter weights for each spatial location and channel group of the input feature maps. We investigate the effectiveness and generalization of the proposed method across multiple tasks, including image classification, semantic segmentation, instance segmentation, video instance segmentation, and image-to-image translation. Both qualitative and quantitative results demonstrate that our approach effectively adapts to the different feature frequencies to avoid aliasing while preserving useful information for recognition. Code is available at https://maureenzou.github.io/ddac/.

A robust metal-organic framework nanofibrous membrane as filter for fast separation of cationic dyes from aqueous solution

• Bio-MOF-1@TPU NFM with robust mechanical properties was successfully fabricated. • Bio-MOF-1@TPU NFM can be used as a filter to separate cationic dye from aqueous solution. • Bio-MOF-1@TPU NFM exhibited fast filtration ability and stable reuse effect. • The separation process was based on the ion-exchange and monolayer adsorption mechanisms. A robust metal-organic framework (MOF) nanofibrous membrane (NFM) was successfully fabricated via electrospinning by employing thermoplastic polyurethane (TPU) as substrate and encapsulating anionic bio-MOF-1 into TPU nanofibers. Characterization with FT-IR, EDS and PXRD confirmed that the crystal structure of bio-MOF-1 maintained well in TPU nanofibers. Based on the ion-exchange mechanism, the as-prepared bio-MOF-1@TPU NFM can be used as a filter for efficient separation of cationic dyes from mixed dyes aqueous solution. Benefiting from the robust mechanical properties of TPU, the bio-MOF-1@TPU NFM can repeatedly withstand the suction filtration pressure without damage, resulting in a very fast dye separation process that completed within 70 s, and a very stable reuse effect that the removal efficiency of MB + was just 9.0 % less than that of the first filtration after five cycles of use. This work will be useful for the design of MOFs NFMs based on electrospinning applied to fast separating organic dyes from practical wastewater.

Delineation of the subsurface boundary between the Central and Southern Eastern Desert, Egypt

The shear zone characterization is a substantial task for understanding the influencing tectonic movements. In this study, an integrated approach of remote sensing and aeromagnetic data is introduced to imagine and trace the subsurface shear zone between the Central (CED) and Southern (SED) domains of the Egyptian Eastern Desert in comparison with the previously proposed approaches mainly using only surface criteria. To produce an enhanced geological map reflecting the different lithological units along both sides of the surficial shear zone, Landsat-8 images are processed and interpreted using False Color Composite (FCC), Color Ratio Composites (CRC). Moreover, the associated lineaments and their trends are extracted from Digital Elevation Model (DEM) data using the lineaments extraction approaches. For delineating the subsurface structures pattern and tracking the probable subsurface CED/SED boundary, aeromagnetic datasets are reduced to magnetic pole (RTP) and, then, interpreted by applying significant techniques comprising upward continuation, Gaussian separation filter, horizontal gradient magnitude (HGM), and tilt derivative angle (TDR). The best path of the shear zone line at depths was imagined; this path agrees with some geologists' opinion regarding the superficial description of the CED/SED separating shear zone. On the other hand, trend analysis was applied on the subsurface and surface data, reflecting a positive matching between the resulting trends from the magnetic and remote sensing data. The NW direction represents both data's major trend and less common NNW NS, NNE, and ENE trends. This relation reflects the extension and effect of the subsurface structures on the surface in the study area.

PWM Inverter with 4-Phase Carrier for Grid Connection Via Combined LCL Filter

A PWM power conversion system connected to a grid through parallel-combined LCL filter is proposed in this paper. The system has four inverters paralleled and operates with PWM using 4-phase carrier for powering up and performance improvement. Four LCL filters have four separate filter inductors connected to individual inverters and one common LC filter which is composed of a filter capacitor and a grid inductor. The differential mode current circulates only through four inverters and four filter inductors. The differential mode current is completely eliminated from the filter capacitor and the connected power grid. Accordingly, performance improvement can be achieved since the current in the filter capacitor is reduced and the harmonic current into a grid is reduced. An 1.3kW single phase prototype system has been constructed and tested, and the proposed system has been verified.

Carbon-based nanocomposites: Distinguishing between deep-bed filtration and external filter cake by coupling core-scale mud-flow tests with computed tomography imaging

Although Multi-Walled Carbon NanoTubes (MWCNTs) are found to influence the rheological behavior of drilling fluids, there are yet some controversies regarding their performance towards reducing formation damage induced by the invasion of water-based drilling fluids (WBFs). To address this important question, we synthesized novel nanocomposite materials via modifying the MWCNT via varying the proportion of carboxylated MWCNTs to PolyVinyl Alcohol (PVA). These nanocomposites were then used to make nano-based drilling-fluids (NDFs). The performance of the NDFs was evaluated by a set of rheological behavior tests, filtration experiments, and core-scale mud flow tests. To distinguish between the internal and external damages made by the drilling fluid, computed tomography (CT) scanning was performed during the mud flow tests. The best yield stress (YP) and plastic viscosity (PV) were achieved at a 1:36 proportion of carboxylated MWCNTs to PVA (named as PVCNT-3). While the bulk rheological measurements (by varying the concentration of the nanocomposites between 0 and 0.6 wt%) showed a sharp increase in both YP and PV, the filtration tests showed contrary results. Independent of the nanocomposite content, the filtrates were also completely clear, demonstrating that PVCNT-3 acts as an efficient water-clay separation filter. NDFs containing a lower amount of PVCNT-3 (0.1–0.3 wt %) showed a noticeably lower degree of formation damage and a thicker external (impermeable) filter cake as confirmed by the CT scan images taken during the mud flow tests. However, high concentration of nanocomposites was found to cause significant internal pore plugging and formation damage. The results highlight the advantage of coupling core-scale tests with in-situ imaging to unravel the types of damages induced by the mud: build-up of an impermeable mud cakes (external damage) or deep-bed filtration (internal damage). This information is very essential for building proper models which capture different types of damages induced by drilling fluids.

Dual-Band Design Techniques for Microwave Passive Circuits: A Review and Applications

The introduction of new technology in the wireless communication industry increases the number of frequency bands in the communication environment. Therefore, a communication system capable of functioning over several frequency bands, known as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband communication system</i> , is required. In addition, multiband communication systems support technology upgrades by smoothly bridging the migration from the existing technology to a newer technology. A multiband communication system can be developed with the help of two approaches. The first approach is a multiband communication system that contains multiple microwave circuits, with each circuit optimized for a single band; for example, a dual-band communication system has two low-pass filters and two power amplifiers. But this approach increases not only the size but also the cost of the system. In the second approach, rather than using a separate power amplifier and filter for each frequency band, a single power amplifier, filter, and other components are used that can support more than one frequency band. These circuits are known as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband microwave circuits</i> . Multiband circuits not only minimize size but also reduce the cost of designing the multiband communication system.

Multifunctional biomass carbon fiber aerogel based on resource utilization of agricultural waste-peanut shells for fast and efficient oil–water/emulsion separation

In this work, the flexible, ultralight, hydrophobic and multi-functional biomass carbon (BC) aerogel was prepared, and the porous network structure provides efficient oil transmission and storage channels (the porosity of 98.39%). With the extraordinary wettability, the BC aerogel maintains stable hydrophobicity (>135°) and the maximum water contact angle is 141°. BC aerogel exhibits the great reusability of elastic material after multiple intensive compressions. Simultaneously, B-C aerogel holds a wonderful absorption capacity for various oils and organic solvents (27–50 g/g), possessing an extraordinary recyclability (94%). Furthermore, BC aerogel can also be taken as the separation filter of oil/water mixture (1561.19 L m−2 h−1, 99.13%) and used to separate emulsion with relatively stable surface activity (1039.49 L m−2 h−1, 91.93%). The research provides a green strategy for preparing hydrophobic oil-absorbing materials from low-cost materials and has the great application potential in oil–water/emulsion treatment and environmental protection.

Synthesis of sustainable poly(S-Abietic-co-Pinene) through inverse vulcanization of Kurdica gum and used to fabricate durable and recyclable super-hydrophobic cotton wool filter: Oil-water separation application

The renewable and sustainable poly(S-Abietic-co-Pinene) with a high sulfur content was synthesized by inverse vulcanization of elemental sulfur and natural kurdica gum (extracted from the Pistacia atlantica tree). This hydrophobic polysulfide (KPS) is dip-coated on cotton wool to obtain a super-hydrophobic filter with a water contact angle of 165°. All polysulfide and coated filters are characterized by the FTIR, 13CNMR, TGA, SEM, X-ray map, EDX, and WCA. The 3-Aminopropyltriethoxysilan (APTES) reagent was used to enhance the adhesive forces between cotton and the KPS coating. The super-hydrophobic cotton-KPS wool filters were conducted for six bi-phasic oil-water separations. The high separation efficiencies and permeate fluxes as well as the 100% rejection of the aqueous phase are advantages of cotton-KPS wool filters. Also, no significant change was observed in the separation efficiency after 20 recycling numbers, implying the high durability and stability of the super-hydrophobic coating on the cotton-KPS filter. The use of renewable natural materials for the synthesis of novel polymers and the fabrication of robust super-hydrophobic filters for oil water separation can be based on green chemistry and sustainable development principles.

MoS2 QDs-nanoparticle-engineered based hydrophobic filter for high performance water-oil separation

• A novel hydrophobic AC/MoS2 QDs/SSM filter for separation oil–water emulsion. • Preparation by economical materials, simple and one step hydrothermal method. • High selectivity, high flux and high recyclability. The demand for the development of inexpensive and effective approaches for the oil–water separation is increasing due to the global concern in oil industries. In this study, we synthesized nano porous activated carbon (AC)/ Molybdenum disulfide (MoS2) quantum dots (QDs) stainless still mesh (SSM) as a hydrophobic and oleophilic nano filter by hydrothermal method in one step in 200 °C for 12 h, which was characterized by various XRD, FTIR, SEM/Map, TEM, BET-BJH, CV, AFM, DLS and PL techniques. The results showed that the solvent type was also effective in the amount of its separation from oil. Further, the effect of water-to-solvent ratio and pH was investigated. Based on the results of petrol with a water-to-solvent ratio of 20/20 at pH = 7 and at a time of 10 s, 99.99% was separated by AC/MoS2 QDs/SSM. The results showed that repeatability cycle of the AC/MoS2 QDs/SSM was 23 times and its duration to 30 s. The results of kinetic studies revealed that the Pseudo second order kinetic model was in good agreement with the experimental data. This novel filter demonstrated an excellent separation with high selectivity, good flux > 6000 L/m 2 h and high repeatability with great durability from low cost materials and simple method that was appropriate for treating stratified water–oil and water in oil emulsion without using demulsifier.

Separation and estimation of periodic/aperiodic state

Periodicity and aperiodicity can exist in a state simultaneously and typically become quasi-periodicity and quasi-aperiodicity in a dynamically changing state. The quasi-periodic and quasi-aperiodic states existing in the periodic/aperiodic state mostly correspond to different phenomena and require different controls. For separation control of these states, this paper defines the periodic/aperiodic, quasi-periodic, and quasi-aperiodic states to construct a periodic/aperiodic separation filter that separates the periodic/aperiodic state into the quasi-periodic and quasi-aperiodic states. Based on these definitions, the linearity of periodic-pass and aperiodic-pass functions and the orthogonality of quasi-periodic and quasi-aperiodic state functions are proved. Subsequently, the periodic/aperiodic separation filter composed of periodic-pass and aperiodic-pass filters that realize the periodic-pass and aperiodic-pass functions is designed and integrated with a Kalman filter for estimation of the quasi-periodic and quasi-aperiodic states.

NIR based wireless sensing approach for fruit monitoring

Monitoring the storage phase of grapes is a key issue as it is closely related to berry quality, so it is essential to investigate a rapid and comprehensive method of non-destructive wireless inspection applied to the berry storage process. In this study, a cost-effective optical measurement system was designed, built, and tested to determine optimal storage results. NIR spectral measurement system covers 6 separate on-device filters from 610 nm to 860 nm. The experiments were performed on Kyoho grapes. In addition, each sample was analyzed for soluble solids content (SSC) by conventional laboratory methods and used as a reference parameter. The results showed that the use of the artificial neural network (ANN) (RMSEP = 0.62 and Rp2 = 0.69) worked best and could be used for preliminary screening of fruit quality.

The effect of layer number on the gas permeation through nanopores within few-layer graphene

Few-layer graphene has been widely regarded as an efficient filter for gas separation, but the effect of the layer number on the gas permeation process is still unclear. To explore the layer number effect, we perform molecular dynamics simulations to investigate the gas permeation through a nanopore within the few-layer graphene. Our numerical simulations show that the permeation constant decreases with increasing layer number, which is analyzed based on the macroscopic Kennard empirical model. The macroscopic model is in good agreement with the numerical result in the limit of large layer number, but there are obvious deviations for the medium layer number. We generalize the macroscopic model by considering the nanoscale effect from the surface morphology of the nanoscale pore, which can well describe the layer number dependence for the gas permeation constant in the full range. These results provide valuable information for the application of few-layer graphene in the gas permeation field.

Systematic Design of a Flow-Through Titanium Electrode-Based Device with Strong Oil Droplet Rejection Property for Superior Oil-in-Water Emulsion Separation Performance.

Oily wastewater treatment has been restricted by the existence of stable oil-in-water (O/W) emulsions containing micrometer-sized oil droplets. However, the strong adhesion and stacking of emulsified oil droplets on the surface of current separation media cause serious fouling of the treatment unit and the rapid decline of treatment efficiency. Herein, a novel flow-through titanium (Ti) electrode-based filtration device with remarkable oil droplet rejection property was well designed for the continuously separating O/W emulsion. In contrast to the pristine Ti foam, the permeance of the TiO2 nanoarray-coated Ti foam (NATF) increased from 2538 to 4364 L m-2 h-1 bar-1 through gravity-driven flow. Further, more than ∼70% permeability can be maintained after 6 h of O/W emulsion filtration using the current device, the value of which was markedly higher than that of conventional oil/water separation filters (less than 5%). According to the results of wettability test, the super-oil-repellent surface endowed by this nanoarray structure primarily avoided the formation of a compact oil fouling layer. When the voltage was applied, accompanied by the electrophoresis effect, redistribution of surfactant molecules on the surface of oil droplets induced by an electric field made them readily captured by the microbubbles continuously generated from the electrode, thereby rapidly migrating these bubble-adhered oil droplets far from the filtration medium.

Metamaterial microbolometers for multi-spectral infrared polarization imaging

Vanadium oxide (VOx) microbolometers enable the construction of high-performance yet low-cost and uncooled imaging detectors in the mid-infrared spectrum. Typical micro-bolometers are broadband sensors with no polarization selectivity. Thus, imaging detectors based on microbolometers have to use separate spectral and polarization filters to select the target spectral bands and polarization states, and the resulting systems are complicated and bulky. Here we demonstrate that by using metamaterial absorbers (MAs), which are arrays of optical resonators with sub-wavelength dimensions and spacing, we simultaneously tailor the VOx microbolometers' spectral and polarization responses, the need for separate spectral filters and polarizers can be mitigated. The MAs selectively absorb the TM polarization component of the incident light in a spectral band with tunable central wavelength and bandwidth while rejecting the TE polarization component. Two MAs with average TM absorption of 0.8322 in the 5.150 µm - 6.422 µm band and 0.7720 in the 5.867 µm - 7.467 µm band are fabricated, and the polarization extinction ratio (PER) are 42.24 and 42.65, respectively. The MAs are applied to VOx micro-bolometers, and the measured detector responses agree well with the absorption spectra of the MAs. The achieved peak responsivities of two fabricated detectors are 1.0 V/W at 6.0 µm and 1.46 V/W at 6.8 µm, respectively. And the two detectors achieve a D* of 6.94×105 cm·Hz1/2W-1 at 11Hz and 9.95×105 cm·Hz1/2W-1 at 36Hz, respectively. Our work paved the way towards large format room temperature multi-spectral infrared polarization imaging detector.

Superwetting patterned PDMS/PMMA materials by facile one-step electro-spraying for signal expression and liquid transportation

• Patterned PDMS/PMMA coating with asymmetrical wettability has been constructed by electro-spraying technique. • Membrane filters with high wetting contrast demonstrate high separation efficiency and good cycling ability. • Patterned surfaces with anisotropic adhesion show promising on-demand droplet manipulation ability. • Real-time liquid signal expression is realized on such wetting-patterned membrane with high efficiency. Superwetting materials with multiple functions have drawn heightened attention due to their delicately adjustable surface wettability. However, realizing the full potential of diversified functions is often hampered by the usually symmetrical wetting state. Herein, we introduce a versatile electro-spraying technique to construct a patterned PDMS/PMMA coating with asymmetrical wettability. The tunable superwetting patterns are able to achieve the required functional diversity. The as-prepared superhydrophobic fabric can act as a separation filter with a high separation efficiency and satisfactory cycling ability. With the wettability difference, such patterned surfaces can also manipulate the successive drops motions, and relation between the surface patterns and the controllable movement is demonstrated. In addition, the patterned surface can serve as a smart signal-expression membrane, thereby enabling real-time variable liquid signal expression with alterable signals. The exciting results have paved the way for expanding the application foreground of smart superwetting materials in microfluidics and signal-detection.

Integrated microfluidic single-cell immunoblotting chip enables high-throughput isolation, enrichment and direct protein analysis of circulating tumor cells

Effective capture and analysis of a single circulating tumor cell (CTC) is instrumental for early diagnosis and personalized therapy of tumors. However, due to their extremely low abundance and susceptibility to interference from other cells, high-throughput isolation, enrichment, and single-cell-level functional protein analysis of CTCs within one integrated system remains a major challenge. Herein, we present an integrated multifunctional microfluidic system for highly efficient and label-free CTC isolation, CTC enrichment, and single-cell immunoblotting (ieSCI). The ieSCI-chip is a multilayer microfluidic system that combines an inertia force-based cell sorter with a membrane filter for label-free CTC separation and enrichment and a thin layer of a photoactive polyacrylamide gel with microwell arrays at the bottom of the chamber for single-cell immunoblotting. The ieSCI-chip successfully identified a subgroup of apoptosis-negative (Bax-negative) cells, which traditional bulk analysis did not detect, from cisplatin-treated cells. Furthermore, we demonstrated the clinical application of the ieSCI-chip with blood samples from breast cancer patients for personalized CTC epithelial-to-mesenchymal transition (EMT) analysis. The expression level of a tumor cell marker (EpCAM) can be directly determined in isolated CTCs at the single-cell level, and the therapeutic response to anticancer drugs can be simultaneously monitored. Therefore, the ieSCI-chip provides a promising clinical translational tool for clinical drug response monitoring and personalized regimen development.

Delineation of Subsurface Structures Using Gravity Data of the Shallow Offshore, Lamu Basin, Kenya

Lamu Basin is located in South Eastern Kenya and covers about 170 000 km2 both onshore and offshore. Kenya’s Lamu Basin is hitherto underexplored even though there have been notable oil and gas discoveries along the margin of East Africa. This study focuses on the shallow section of the Lamu offshore bounded by 39°E to 43°E by 2°S to 6°S, whereby, unfortunately, some of the wildcat wells turned out to be dry although expensive. Gravity interpretation techniques such as spectral analysis and first horizontal derivative were applied to the reduced gravity data to delineate and model structures to minimize the high investment risks. The gravity data used in this study were sourced from the International Gravity Bureau (BGI) and National Oil Corporation of Kenya (NOCK) digital data courtesy of companies like Woodside Energy, Anadarko Kenya Limited, and Total Exploration and Production companies. The obtained reduced gravity data were gridded to produce the gravity anomaly grids (Free air, Bouguer, and Isostacy), which were consequently drawn into maps. From spectral analysis, depths to shallow sources and deep sources were estimated. These depths were used to set regional and residual separation filters using the Gaussian filter. The first horizontal derivative (FHD) applied to the regional Isostatic gravity anomaly map yielded features that were inferred as intrasediment fractures/faults trending in NW-SE and NE-SW directions. The features like the ridges, troughs, and faults mainly trending in the NW-SE direction are discernable from the regional anomaly map. The developed models show the basement highs and lows with a possibility of anticlinal and synclinal structures and thick sedimentary successions likely to represent good hydrocarbon source kitchens.

How separable median filters can get better results than full 2D versions

The well-known method of median filtering is used both in a wide range of application frameworks and as a standalone filter. Small-window median filters can highly reduce the power of salt and pepper or additive Gaussian noise and minimize edge blurring. Large-window filters are also used, for example to estimate the background of images. Currently, the window size should not be an issue as a constant time algorithm and several implementations, including GPU-based codes, have been proposed in recent years. Unfortunately, none of these constant time implementations manage to fully exploit the capabilities of modern GPUs, and thus the throughputs of large-window median filters remain far below the peak throughputs allowed by recent GPU models. This paper aims at showing that a separable approximation of a 2D median filtering is often stronger than its full 2D implementation. Statistical and theoretical analysis are conducted to show and explain this fact which had so far remained unobserved. It is confirmed by experimentations on a dataset composed of 10,000 images, corrupted by different levels of salt and pepper noise. Separable and full 2D median filter algorithms are compared with several metrics, notably PSNR and MSSIM. In addition, a GPU implementation of 2D separable median filters is also proposed. This implementation is able to output up to 125 billion pixels per second on a recent Volta V100, which significantly outperforms existing implementations like Nvidia’s NPP library or Green’s code, resulting in the fastest median filtering solution to date.

Quasi Single-Stage Three-Phase Filterless Converter for EV Charging Applications

This paper presents a novel converter concept of the off-board electric vehicle (EV) charging, which is based on an unfolding rectification approach where the three-phase Vienna rectifier-based unfolder (VRU) is followed by two identical isolated current-source converter (CSC) modules in input-series output-parallel configuration. The VRU operates at low frequency and thus features negligible switching losses, while the CSCs are responsible for the synthesis of the high-quality sinusoidal grid current and output voltage regulation. The proposed configuration features two time-varying soft DC-links, thus no bulky electrolytic capacitors are required. Input inductors of the CSCs limit the input current ripple, eliminating the need for separate grid filter inductors. Another notable advantage lies in the simplicity of the control system. Each CSC operates at a fixed frequency and provides the required current wave-shaping using only a single independent control variable, while no high-frequency synchronization between the two modules is required. The proposed configuration features a modular structure and was verified with a 5 kW experimental prototype based on two identical 2.5 kW dc-dc modules and a common unfolding stage. During the experiments, the system provided power factor above 0.97 and THD below 5%. At rated power, the maximal efficiency of 94.8% was obtained.

Створення багатосекційного фільтру очищення води з автоматизованим контролем забруднення мембран

The article is devoted to the creation of a multi-section water purification filter, which can be made by hand at home. At the same time it is necessary to apply in the filter the automated control of pollution of membranes in sections of the filter. The main purpose of the study is to develop a simple and cheap multi-section filter for drinking water purification. The filter must have different cleaning technologies with the possibility of its own manufacture and with the possibility of automated control of membrane contamination. The task of the research is to develop and manufacture a working model of a multi-section filter for drinking water purification. The design of the filter should be multi-section with membranes containing various fillers for water purification; simple and cheap to make at home. The design of the filter should provide for automated control of the degree of contamination of the membranes in the filter sections. By analyzing the existing common household water filters, the most optimal solution for developing your own design of a household water filter has been determined. As a result of the analysis, a working model of a three-section water filter was created. The first section of the filter contains a membrane with quartz sand, the second section contains a membrane with activated carbon powder, the third section contains a membrane with small pieces of shungite (or with small pieces of silicon). As a result of an experimental study of the filtration of contaminated water using a three-section filter was determined next. The weight of water after passing through the filter decreases due to the retention of substances with a density greater than that of water (solid impurities). Also, the filtered water became clear and stopped foaming when shaken. This confirms the efficiency of the proposed filter. The developed three-section filter can be used as a separate stand-alone water filter or in addition with household polypropylene water filters for quality filtration of impurities up to 1 micrometer.