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1
Kaufman, Amanda R., Lisa M. Casanova, and Mark D. Sobsey. "Efficacy of a ceramic siphon household water filter for removal of pathogenic microorganisms: lifespan volume test." Journal of Water, Sanitation and Hygiene for Development 1, no. 2 (June 1, 2011): 102–11. http://dx.doi.org/10.2166/washdev.2011.037.
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Treatment of drinking water at the point of use (POU) has demonstrated health benefits for people who have access only to microbially contaminated drinking water. In this work, the ceramic siphon POU water filter was evaluated for its ability to reduce indicator microorganisms in test waters. During batch challenge tests, the filter reduced Escherichia coli in filtered water by 7 log10 (99.999987%) and bacteriophage MS2 by 0.12 log10 (24.0%). Next, a novel continuous flow dosing system allowing sewage-amended feed water to constantly pass through the filters allowed for determination of changes in microbial reductions over time and total volume of water filtered. E. coli B, MS2 and fluorescent microspheres (as a surrogate for Cryptosporidium oocysts) were seeded into test water and dosed to filters at 10, 25 and 50% of the filter's volume lifespan. Microbial removal efficacy decreased as the volume of water filtered increased and test filters did not achieve their volume lifespan before physically failing. The ceramic siphon household water filter is effective in reducing E. coli and surrogates for Cryptosporidium in water, but filter modifications may be needed to achieve acceptable levels of virus removal and to reach the target 7,000 L volume lifespan of the filter.
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Trantham, E. Clark. "Minimum uncertainty filters for pulses." GEOPHYSICS 58, no. 6 (June 1993): 853–62. http://dx.doi.org/10.1190/1.1443469.
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The objective of this paper is to calculate filters with a minimum uncertainty, the product of filter length and bandwidth. The method is applicable to producing minimum uncertainty filters with time or frequency domain constraints on the filter. The calculus of variations is used to derive the conditions that minimize a filter’s uncertainty. The general solution is a linear combination of Hermite functions, where the Hermite functions are summed from low to high order until the filter’s constraints are met. Filters constrained to have zero amplitude at zero hertz have an uncertainty at least three times greater than expected from the uncertainty principle, and the minimum uncertainty filter is a first derivative Gaussian. For the previous filter, the minimum uncertainty high cut filter is a Gaussian function of frequency, but the minimum uncertainty low cut filter is a linear function of frequency.
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Ahmed, Osman, Shermeen Sheikh, Patrick Tran, Brian Funaki, Alexandria M. Shadid, Rakesh Navuluri, and Thuong Van Ha. "Inferior Vena Cava Filter Evaluation and Management for the Diagnostic Radiologist: A Comprehensive Review Including Inferior Vena Cava Filter-Related Complications and PRESERVE Trial Filters." Canadian Association of Radiologists Journal 70, no. 4 (November 2019): 367–82. http://dx.doi.org/10.1016/j.carj.2019.06.003.
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Inferior vena cava filters are commonly encountered devices on diagnostic imaging that were highlighted in a 2010 Food and Drug Administration safety advisory regarding their complications from long-term implantation. The Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE) trial is an ongoing after-market study investigating the safety and utility of commonly utilized filters in practice today. While most of these filters are safe, prompt recognition and management of any filter-associated complication is imperative to prevent or reduce the morbidity and mortality associated with them. This review is aimed at discussing the appropriate utilization and placement of inferior vena cava filters in addition to the recognition of filter-associated complications on cross-sectional imaging. An overview of the PRESRVE trial filters is also provided to understand each filter's propensity for specific complications.
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Li, Luping, Lijuan Dong, Peng Chen, and Kai Yang. "Multi-band rejection filters based on spoof surface plasmon polaritons and folded split-ring resonators." International Journal of Microwave and Wireless Technologies 11, no. 08 (April 17, 2019): 774–81. http://dx.doi.org/10.1017/s1759078719000369.
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AbstractA dualband rejection filter and a triband rejection filter are proposed in this letter, both of which are implemented by cascading spoof surface plasmon polaritons (SSPPs) of the same structure but with diverse rejection bands. Compared with traditional ones, the proposed filters provide more compact structures, wider rejection bands, and better independent tunability. In the proposed filters, the rejection bandwidth, the center frequency of the rejection band and the filter's cutoff frequency can be adjusted independently. And the different rejection bands in the same filter also can be independently controlled. Agreements between the dispersion of SSPP units and the S21 of filters are also presented. Measurement results demonstrate that both filters load multiple rejection bands on the 27.7 GHz wide low-pass band and all the rejection bands locate in Ku and K bands. The average rejection bandwidth and the average rejection depth of the two filters are 1.49 GHz and 42.1 dB, respectively.
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Wang, Wenli, and Philip Winters. "Statistically Significant Efficiency Testing of HEPA Filters." Journal of the IEST 47, no. 1 (September 14, 2004): 101–6. http://dx.doi.org/10.17764/jiet.47.1.bq380t6134311822.
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High Efficiency Particulate Air (HEPA) filter manufacturers must ensure the accuracy of efficiency testing for these filters and, at the same time, keep productivity at a reasonable level. This study describes tests conducted to determine the minimum time required to provide statistically significant efficiencies of HEPA filters using a test system currently in use of HEPA filter production. The test results of over 300 HEPA filters were analyzed in this study. The approaches in IEST RP-CC-007.1: Testing ULPA Filters for statistical analysis of particle counts were followed. A Poisson distribution was used to describe the variations and to calculate the lower and upper limits of measured counts at 95% confidence level. This study shows that 90 seconds is sufficient for this test system to determine whether a HEPA filter has an efficiency of 99.990% or higher at 95% confidence. Longer tests will cause the mean measured efficiency to approach the filter's true efficiency and also narrow the confidence interval. However, challenging HEPA filters made of glass fiber media with oil aerosols for up to one hour does not significantly change the filter's true efficiency performance. The preferred approach for a new test system is to use software that calculates the confidence limits of filter efficiency after each sampling cycle and determines whether to continue testing. For an existing system without this type of program (such as the one evaluated in this study), analysis is necessary to make sure the HEPA filters are challenged with enough aerosol particles.
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Hruschka, Crassen, Udo Barabas, and Lutz Gohler. "Optical narrow band filter without resonance's." Facta universitatis - series: Electronics and Energetics 17, no. 2 (2004): 209–17. http://dx.doi.org/10.2298/fuee0402209h.
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This paper introduces an optical wave filter, which uses gratings at 45? or 135? inclined grating lines that avoid any resonance's. Therefore, many more options to form the filter shape exist. In general, the filter design can be traced to that of transversal filters (finite impulse response filter, FIR filter). Such an integrated optical wave filter is characterized by steep filter slopes and a narrow pass band (less then 01nm) combined with a high stop band attenuation (more than 40dB) and a linear phase response in the pass band. Compared to conventional Bragg grating filters, the inclined grating line filters can have a flatter pass band and steeper filter skirts related to the width of the pass band. In general, the filter's realization is possible using any optical material. In view of the excellent optical properties the semiconductor material system InP/InGaAsP is used for manufacturing the filter.
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Borges, Vinícius S., Erivelton G. Nepomuceno, Carlos A. Duque, and Denis N. Butusov. "Some Remarks about Entropy of Digital Filtered Signals." Entropy 22, no. 3 (March 23, 2020): 365. http://dx.doi.org/10.3390/e22030365.
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The finite numerical resolution of digital number representation has an impact on the properties of filters. Much effort has been done to develop efficient digital filters investigating the effects in the frequency response. However, it seems that there is less attention to the influence in the entropy by digital filtered signals due to the finite precision. To contribute in such a direction, this manuscript presents some remarks about the entropy of filtered signals. Three types of filters are investigated: Butterworth, Chebyshev, and elliptic. Using a boundary technique, the parameters of the filters are evaluated according to the word length of 16 or 32 bits. It has been shown that filtered signals have their entropy increased even if the filters are linear. A significant positive correlation (p < 0.05) was observed between order and Shannon entropy of the filtered signal using the elliptic filter. Comparing to signal-to-noise ratio, entropy seems more efficient at detecting the increasing of noise in a filtered signal. Such knowledge can be used as an additional condition for designing digital filters.
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Havis, Azhar Al, and Liza Fitria. "Filtering Sinyal Menggunakan Band Pass Filter." Jurnal SIFO Mikroskil 19, no. 2 (May 29, 2018): 37–48. http://dx.doi.org/10.55601/jsm.v19i2.594.
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In our daily lives we find many filters, filters from the word itself are filters. Filters vary, there are air filters to filter dirty air to be clean, filters / filters for coffee and tea to filter coffee or tea pulp, and so on. All of them try to filter something to get what we want. The filter here is a frequency filter, from which the filter will filter the frequency. The existing frequency we filter so get the frequency as we want. In this research, signal filtering will be carried out using Band Pass. The band-pass filter will pass signals with frequencies in a certain range and reduce the signal with other frequencies. The sound sample used is the sound of a cat with just one sample. In this sample signal screening is carried out with 5 different frequencies, namely at frequencies of 8000, 16000, 32000, 48000 and 96000. Data retrieval and processing of voice signals are carried out with the help of audacity and Matlab R2010b software. Sound data in the .wav format is filtered to remove noise and filter using a band pass filter. Sounds issued that are received are destructive which eliminate the sound information that is carried. This of course requires that the sound quality received is not good, so it requires sound signal processing to eliminate noise. Then the voice data is processed by voice signal using the FFT (Fast Fourier Transform) method. The results of this study are the output of sound signals that are clean from noise.
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Hromić- Jahjefendić, Altijana, Selma Kozarić, Adna Hrapović, Aiša Trebo, Ajla Tipura, and Muhamed Adilović. "Comparison of Brita and Profissimo water filters." Heritage and Sustainable Development 5, no. 1 (June 30, 2023): 151–58. http://dx.doi.org/10.37868/hsd.v5i1.177.
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This research was focused on testing two water filters - Brita and Profissimo, which were filtering two and five liters of water every day. The lifespan of used filters is four weeks, while they have been actively used for eight weeks in this study to check for their efficiency after exceeded usage. Along with this, the quality of tap water, which was filtered using these two types of filters, was also tested. The experiment of the whole study was divided into three main stages: microbiological analysis, biochemical analysis, and UV-VIS spectrophotometric analysis of filtered water. The measurements were done every five days. The aim was to compare the performances of Brita and Profissimo filters after the completion of the required experiments. Based on the results that are obtained from all the analyses mentioned previously, we can conclude that Brita 2l filter was the most efficient, while Profissimo 5l filter appeared to be the least effective filter. It is important to emphasize that the tap water in Sarajevo is generally clean and drinkable, so there is a possibility that when using more polluted water, greater deviations in the operation of filters can be observed. Overall, both water filters were usable even after two months of active usage and our measurements showed good water quality which lacks impurities and is safe for drinking.
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Kang, Wei, Li Xia Zhang, and Ji Bo Wan. "Matching Characteristic of Constant Voltage Source Excited Filter in Power System." Applied Mechanics and Materials 427-429 (September 2013): 1072–75. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.1072.
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Filters between voltage source converter and the batteries in power system can be categorized into constant voltage source excited filters. The paper discusses the importance of the matched structure and parameters for power filters. The relation between matched structure and filters output characteristic is demonstrated and the design principle is introduced. The work above proved that even if the filters are designed for the same transfer function, so long as filters load resistance is different, their designed parameters are also different. Traditional power system filter seldom consider its both ends load matching characteristic. When the difference between filter's load characteristic and practical system equivalent impedance are large, the actual filtering effect becomes worse, current loss arises and even there may be the possibility of resonance. As the lack of energy resource and energy crisis is gradually becoming a serious problem, energy conservation is important. Constant voltage source excited circuit configuration model is established through the simulation and test. The results show the validity and feasibility of the method that filter should be designed the according to its load characteristic in practical application.
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Bui, Ngoc Ha, Tien Hung Bui, Thuy Duong Tran, Kim Tuan Tran, and Ngoc Toan Tran. "Evaluation of the effect of filters on reconstructed image quality from cone beam CT system." Nuclear Science and Technology 11, no. 1 (March 15, 2021): 35–47. http://dx.doi.org/10.53747/jnst.v11i1.130.
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: 3D Filtered Back Projection (FBP) is a three-dimensional reconstruction algorithm usually used in Cone Beam Computed Tomography (CBCT) system. FBP is one of the most popular algorithms due to its reconstruction is fast while quality of the result is acceptable. It can also handle a more considerable amount of data with same computer performance with other algorithms. However, the quality of a reconstructed image by the FBP algorithm strongly depends on spatial filters and denoising filters applied to projections. In this paper an evaluation of the reconstructed image quality of the CBCT system by using different denoising filters and spatial filters to find out the best filters for the CBCT system is performed. The result shows that, there is a significantly decrease of the noise of projection with the combination of Median and Gaussian filters. The reconstructed image has high resolution with Cosine filter and becomes more sharpen with Hanning filter.
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Fylypchuk, Viktor, Stanislav Induchny, Pete Pearce, Leonid Fylypchuk, and Serhii Martynov. "Application of expanded polystyrene filter for tertiary treatment of domestic waste effluent in the UK." Journal of Water and Land Development 35, no. 1 (December 1, 2017): 41–47. http://dx.doi.org/10.1515/jwld-2017-0066.
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AbstractThe use of expanded polystyrene filters is a promising method for tertiary treatment of domestic waste effluent where biologically treated effluent is filtered through a layer of buoyant polystyrene beads. The advantage of such filters is in the absence of backwashing pumps, containers of clean washing water, while having low energy costs, high resistance of polystyrene to various chemical contaminants that may be in the effluent, easy automation of switching modes.The article describes the features of the design and principles of the expanded polystyrene filter operation with an upward filtration flow which works in automatic mode. The article includes the comparison of operation and the structural technological characteristics of polystyrene filters with disc filters, which are usually used in practice of tertiary-treatment of effluent in the UK.Experimental results were obtained from the operation of expanded polystyrene filters with an upward flow of filtration at two operational wastewater treatment plants. The effectiveness of the tertiary-treatment of waste effluent was evaluated by measures of BOD and COD in non-filtered and filtered samples, as well as total suspended solids during the months of the year and hours of the day. The filter demonstrated an average removal of 40% BOD, 28% of COD and 66% of TSS.
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Prasad, K. D., and R. Ramadevi. "Analysis and Comparison of Image Enhancement Techniques for Improving PSNR of Liver Images by Median Filtering over Mask Filtering." CARDIOMETRY, no. 25 (February 14, 2023): 990–95. http://dx.doi.org/10.18137/cardiometry.2022.25.990-995.
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Aim: The goal of this research is to employ median filters and mask filters to reduce noise in liver images so that they can be improved. In addition, the Peak Signal to Noise Ratio of both filters’ outputs was examined (PSNR). Materials and Methods: The afflicted and normal liver photos were obtained from the Kaggle website for this investigation. Then, using Matlab software, the mask filtering and median filtering algorithms were run. Clinicalc. com was used to compute sample size, and SPSS software was used to conduct the comparative analysis. This study has two groups, each with a sample size of 20 people with an average G power of 80%. The innovative median filter’s performance is assessed, and the PSNR performance metric is compared to that of the mask filter. Results: The PSNR of innovative median filters is 64.0310, while mask filters have a PSNR of 78.0095, according to Matlab simulation data. The significant value of PSNR (Peak Signal to Noise Ratio) (0.409) and p>0.05 was found in the statistical analysis. Conclusion: The innovative median filter delivers greater PSNR than the mask filter for medical image enhancement on ultrasound liver pictures, according to this study.
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Tobiason, J. E., J. K. Edzwald, D. A. Reckhow, and M. S. Switzenbaum. "Effect of Pre-Ozonation on Organics Removal by In-Line Direct Filtration." Water Science and Technology 27, no. 11 (June 1, 1993): 81–90. http://dx.doi.org/10.2166/wst.1993.0267.
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A pilot-scale study of the effects of pre-ozonation on the performance of in-line direct filtration was carried out. Performance measures included filtered water turbidity, unit filter run volumes, and organics in filtered waters: DOC, UV254, AOC and DBPs. Continuous operation of four dual media GAC/sand filters with and without pre-ozonation and chlorinated backwash and a dual media anthracite/sand filter were compared to full-scale performance. Pre-ozonation frequently results in longer filter runs, causes a twofold increase in raw water AOC and has little effect on raw water DOC. GAC/sand filters consistently reduced the AOC in the ozone train to levels below that of the full-scale plant and also provided 25 % lower DOC levels as compared to anthracite/sand filters. The effect of ozone and filtration on chlorinated DBPs followed overall DOC removal while DBPs created by ozonation followed AOC removal trends.
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Dalri, Alexandre B., Gilmar O. Santos, Geffson de F. Dantas, Rogério T. de Faria, José R. Zanini, and Luiz F. Palaretti. "Performance of drippers in two filtering systems using sewage treatment effluent." Revista Brasileira de Engenharia Agrícola e Ambiental 21, no. 6 (June 2017): 363–68. http://dx.doi.org/10.1590/1807-1929/agriambi.v21n6p363-368.
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ABSTRACT The objective of this study was to evaluate the performance of three models of drippers using treated sewage effluent, pure and diluted, and two types of filters, screen and disc. The treated sewage effluent used in the experiment was collected from the city’s treatment plant. The experiment included 12 lateral lines with three types of emitters to apply pure (100%) and diluted (50%) effluent filtered by screen and disc filters. The combination of those factors set the treatments: T1 (50% effluent diluted in fresh water filtered by a screen filter); T2 (50% effluent diluted in fresh water filtered by a disc filter); T3 (pure effluent filtered by a screen filter); T4 (pure effluent filtered by a disc filter). The results showed that the flat type emitter is less sensitive to clogging, the disc filter is the most suitable to prevent clogging and the use of pure or diluted sewage effluent increases the drippers’ flow rate coefficient of variation.
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Pichardo, Eduardo, Ángel Vázquez, Esteban R. Anides, Juan C. Sánchez, Hector Perez, Juan G. Avalos, and Giovanny Sánchez. "A Dual Adaptive Filter Spike-Based Hardware Architecture for Implementation of a New Active Noise Control Structure." Electronics 10, no. 16 (August 12, 2021): 1945. http://dx.doi.org/10.3390/electronics10161945.
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Presently, the technology development trend of active noise control (ANC) systems is focused on implementing advanced adaptive filters in resource-constrained electronic appliances. Recently, several authors have proved that the use of two adaptive filter algorithms significantly improves the overall adaptive filter performance. However, the computational cost of these approaches is significantly increased since they use two filters simultaneously. Consequently, these filters cannot be implemented in these devices. To solve this problem, we propose a new ANC structure with switching selection based on filtered-x normalized least mean square (FxNLMS) and filtered-x sign least mean square (FxSLMS) algorithms to reduce the computational cost of the ANC system. The improvement of this factor has allowed us to introduce for the first time an advanced spike-based architecture, which can perform dual filter operations using dynamic routing, to be used in real ANC applications. The results have demonstrated that the computational cost of the proposed dual D-FxNLMS/SLMS algorithm is lower compared with previously reported solutions.
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Khandelwal, Achala, and Pragya Nema. "Application of PI controller based active filter for harmonic mitigation of grid-connected PV-system." Bulletin of Electrical Engineering and Informatics 10, no. 5 (October 1, 2021): 2377–83. http://dx.doi.org/10.11591/eei.v10i5.2907.
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The recent trends show the interconnection of PV system with electric grid. With this configuration the issue of harmonics comes into existence. The mounting figure of power-electronic instruments has formed considerable impression on the power-quality of electric supply. Harmonics deformations have conventionally been handled amid the application of passive-LC filters. Active Filter has emerged as a good substitute for passive filters to reduce the harmonics to great extent as it has numerous benefits over the former filters. The active filter’s most vital part is the applied control strategies. Several researches are being under process to advance the functioning of the filter. One of the important control requirements of filter is the regulation of DC link up capacitor voltage. Here the voltage supervision of capacitor is being done using PI controller. The paper show current harmonics compensation of PV grid connected system using PI controller based active filter. Simulation outcomes have been shown which displays the harmonics are within the IEEE boundaries.
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Lu, Feng, Yihuan Huang, Jinquan Huang, and Xiaojie Qiu. "Gas turbine performance monitoring based on extended information fusion filter." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 2 (May 15, 2018): 483–97. http://dx.doi.org/10.1177/0954410018776398.
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Performance monitoring is a critical issue for gas turbine engine for improving the operation safety and reducing the maintenance cost. With regard to this, variants of Kalman-filters-based state estimation have been employed to detect gas turbine performance, but the classical centralized Kalman filters are subject to heavy computational effort and poor fault tolerance. A novel nonlinear fusion filter algorithm using information description with distributed architecture is proposed and applied to gas turbine performance monitoring. This methodology is developed from federated Kalman filter, and a bank of local extended information filters and one information mixer are combined with extended information fusion filter. The local state estimates and covariance calculated in parallel by the local extended information filters are integrated in the information mixer to yield a global state estimate. The global state estimate of nonlinear system is fed back to the local filters with weighted factor for next iteration. The aim of the proposed methodology is to reduce the computational efforts of state estimation and improve robustness to sensor faults in cases of gas turbine performance monitoring. The simulation results on a turbofan engine confirm the extended information fusion filter's effective capabilities in comparison to the general central ones.
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Ross, Hunter, Huyen Nguyen, Brian Nguyen, Ashton Foster, James Salud, Mike Patino, Yong X. Gan, and Mingheng Li. "Filter Modified with Hydrophilic and Oleophobic Coating for Efficient and Affordable Oil/Water Separation." Separations 9, no. 10 (September 28, 2022): 269. http://dx.doi.org/10.3390/separations9100269.
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To mitigate the damage of oil spills, a filter modified with a hydrophilic and oleophobic coating is proposed for affordable and efficient oil separation and recovery from water. The sol–gel method was chosen to produce a colloidal suspension of titanium dioxide particles for its ease of production and its versatility in application for many different substrates, including paper and cloth fabric. After immersing the substrates into a titanium-containing solution, three techniques were applied to increase the production of titanium dioxide—microwave-assisted, refrigeration, and ultra-sonication. Contact angle tests were done to investigate the change in the filter’s oleophobicity. The titanium dioxide present on the surface of the filter was amorphous, but all treatment methods showed an improvement in oleophobicity. All treated filters improved oil filtration performance by up to eighty percent. The filters isolated motor oil from a mixture while allowing water to pass through. The coated filters also displayed photocatalytic activity by degrading methylene blue on its surface when exposed to sunlight, demonstrating the filter’s self-cleaning ability. For real-world applications, the filter can be supported by a stainless mesh for enhanced strength and durability. While being dragged through the water, the filter collects the surface oil, allowing water to pass through via gravity.
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Mewada, Hiren K., and Jitendra Chaudhari. "Low computation digital down converter using polyphase IIR filter." Circuit World 45, no. 3 (August 5, 2019): 169–78. http://dx.doi.org/10.1108/cw-02-2019-0015.
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Purpose The digital down converter (DDC) is a principal component in modern communication systems. The DDC process traditionally entails quadrature down conversion, bandwidth reducing filters and commensurate sample rate reduction. To avoid group delay, distortion linear phase FIR filters are used in the DDC. The filter performance specifications related to deep stopband attenuation, small in-band ripple and narrow transition bandwidth lead to filters with a large number of coefficients. To reduce the computational workload of the filtering process, filtering is often performed as a two-stage process, the first stage being a down sampling Hoegenauer (or cascade-integrated comb) filter and a reduced sample rate FIR filter. An alternative option is an M-Path polyphase partition of a band cantered FIR filter. Even though IIR filters offer reduced workload to implement a specific filtering task, the authors avoid using them because of their poor group delay characteristics. This paper aims to propose the design of M-path, approximately linear phase IIR filters as an alternative option to the M-path FIR filter. Design/methodology/approach Two filter designs are presented in the paper. The first approach uses linear phase IIR low pass structure to reduce the filter’s coefficient. Whereas the second approach uses multipath polyphase structure to design approximately linear phase IIR filter in DDC. Findings The authors have compared the performance and workload of the proposed polyphase structured IIR filters with state-of-the-art filter design used in DDC. The proposed design is seen to satisfy tight design specification with a significant reduction in arithmetic operations and required power consumption. Originality/value The proposed design is an alternate solution to the M-path polyphase FIR filter offering very less number of coefficients in the filter design. Proposed DDC using polyphase structured IIR filter satisfies the requirement of linear phase with the least number of computation cost in comparison with other DDC structure.
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Deeds, Kyle, Brian Hentschel, and Stratos Idreos. "Stacked filters." Proceedings of the VLDB Endowment 14, no. 4 (December 2020): 600–612. http://dx.doi.org/10.14778/3436905.3436919.
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We present Stacked Filters, a new probabilistic filter which is fast and robust similar to query-agnostic filters (such as Bloom and Cuckoo filters), and at the same time brings low false positive rates and sizes similar to classifier-based filters (such as Learned Filters). The core idea is that Stacked Filters incorporate workload knowledge about frequently queried non-existing values. Instead of learning, they structurally incorporate that knowledge using hashing and several sequenced filter layers, indexing both data and frequent negatives. Stacked Filters can also gather workload knowledge on-the-fly and adaptively build the filter. We show experimentally that for a given memory budget, Stacked Filters achieve end-to-end query throughput up to 130x better than the best alternative for a workload, either query-agnostic or classifier-based filters, and depending on where data is (SSD or HDD).
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Carf`ı, David. "Filters and limits in filtered spaces." Journal of Mathematical Economics and Finance 3, no. 2(5) (February 6, 2018): 33. http://dx.doi.org/10.14505/jmef.v3.2(5).03.
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In this lecture notes, we study filters and limits in a feasible sufficiently general way for many applications to Physics, Economics and Social Science. In particular we analyze:
Filters;
Filter bases;
Basic example in topological spaces;
Basic examples in preordered spaces;
Filtered spaces;
Induced filter bases;
Examples in topological spaces;
Examples on the real line;
Limits;
Limits with respect to filter bases;
Limits with respect to filter bases on subspaces;
Limits and topology;
Limits of functions on topological spaces;
Limits of functions on a topological subspace;
Some basic theorems for topology;
Unicity of the limit in Hausdor spaces;
Limits and functionals;
Limits for real functional;
Limits and operations;
Local boundness;
Complements;
Limits and convergence of filtered bases;
Limit of composition.
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Zhang, Shuai, Yong Xiang Zhang, and Jie Ping Zhu. "Rolling Bearing Feature Extraction Based on Wavelet Filtering with Optimal Combination Bands." Applied Mechanics and Materials 599-601 (August 2014): 434–40. http://dx.doi.org/10.4028/www.scientific.net/amm.599-601.434.
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In order to select the band-pass filter parameters reasonably, a new method of rolling bearing feature extraction based on wavelet filtering with optimal combination bands is proposed. Filter banks with different number of filter/octave are constructed by Morlet wavelet, which are used to filter the signal. The filters with the optimal frequency-band are selected according to the kurtosis of the filtered signal. Then, the optimal band filters in each filter bank are combined to filter the signals and the feature extraction is available. Through simulation and experimental verification, results show that the proposed method is more effective than the common one.
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Bakhshi, Saeideh, David Shamma, Lyndon Kennedy, and Eric Gilbert. "Why We Filter Our Photos and How It Impacts Engagement." Proceedings of the International AAAI Conference on Web and Social Media 9, no. 1 (August 3, 2021): 12–21. http://dx.doi.org/10.1609/icwsm.v9i1.14622.
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A variety of simple graphical filters are available to camera phone users to enhance their photos on the fly; these filters often stylize, saturate or age a photo. In this paper, we present a combination of large-scale data analysis and small scale in-depth interviews to understand filter-work. We look at producers’ practices of photo filtering and gain insights in the roles filters play in engaging photo consumers’ by driving their social interactions. We first interviewed 15 Flickr mobile app users (photo producers) to understand their use and perception of filters. Next, we analyzed how filters affect a photo’s engagement (consumers’ perspective) using a corpus of 7.6 million Flickr photos. We find two groups of serious and casual photographers among filter users. The serious see filters as correction tools and prefer milder effects. Casual photographers, by contrast, use filters to significantly transform their photos with bolder effects. We also find that filtered photos are 21% more likely to be viewed and 45% more likely to be commented on by consumers of photographs. Specifically, filters that increase warmth, exposure and contrast boost engagement the most. Towards the ongoing research in social engagement and photo-work, these findings suggest several practical implications such as designing filters for both serious and casual photographers or designing methods to prioritize and rank content in order to maximize engagement.
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HAAVISTO, P., M. GABBOUJ, and Y. NEUVO. "MEDIAN BASED IDEMPOTENT FILTERS." Journal of Circuits, Systems and Computers 01, no. 02 (June 1991): 125–48. http://dx.doi.org/10.1142/s0218126691000021.
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Idempotent filters produce a root signal in a single filter pass, i.e. the filter output is invariant to further filterings with the same filter. In this paper median based idempotent filter structures are introduced. Two approaches to generate these filters are studied: weighted median filters and median filter cascades. Two subclasses of n-dimensional idempotent weighted median filters, called Class 1 and Class 2 filters in the paper, are introduced. It is shown that both Class 1 and Class 2 filters suppress impulsive noise from n-dimensional input signals and yet have almost no effect on the non-corrupted parts of the signal. These filters are therefore well-suited for example for preprocessing purposes. An application to speech processing is described. Other likely applications of these filters are in image processing and, also, in image sequence processing, where the filter mask is typically 3-dimensional. Sufficient conditions for a filter cascade to be idempotent are given. Two idempotent median filter cascades and their advantages are discussed.
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Chung, Eric T., and Jeff C. F. Wong. "A TV-Based Iterative Regularization Method for the Solutions of Thermal Convection Problems." Communications in Computational Physics 14, no. 4 (October 2013): 1120–46. http://dx.doi.org/10.4208/cicp.270212.310113a.
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AbstractLinear/nonlinear and Stokes based-stabilizations for the filter equations for damping out primitive variable (PV) solutions corrupted by uniformly distributed random noises are numerically studied through the natural convection (NC) as well as the mixed convection (MC) environment. The most recognizable filter-scheme is based on a combination of the negative Laplace equation multiplied with the selection of the spatial scale and a linear function in order to preserve the uniqueness of the filtered solution. A more complicated filter-scheme, based on a Stokes problem which couples a filtered velocity and a filtered (artificial) pressure (or Lagrange multiplier) in order to enforce the incompressibility constraint, is also studied. Linear and Stokes based-filters via nested iterative (NI) filters and the consistent splitting scheme (CSS) are proposed for the NC/MC problems. Inspired by the total-variation (TV) model of image diffusion, well preserved feature flow patterns from the corrupted NC/MC environment are obtained by TV-Stokes based-filters together with the CSS. Our experimental results show that our proposed algorithms are effective and efficient in eliminating the unwanted spurious oscillations and preserving the accuracy of thermal convective fluid flows.
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Chen, Zhimin, and Lenan Wu. "Design of Special Impacting Filter for Multicarrier ABPSK System." Mathematical Problems in Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/921932.
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A rather intuitive technique known as pole-zero placement is introduced to illustrate the frequency response of the special impacting filters (SIFs) with a pair of conjugate zero-poles and deduce the equation of the pole radii. Based on that, the paper proposes an iterative scheme to derive the parameters of the cascade notch filter. The cost function is determined by the cascading notch filter’s influence on impacting filters, converting the cost function’s least square problem to a filter parameters’ standard quadratic programming problem. Finally, a cascading notch SIF (CNSIF) designed to demodulate the ABPSK signals is realized.
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Costa, Andre Luiz Ferreira, Karolina A. C. Fardim, Jennifer M. Mantoani, Ana Lucia Franco Ricardo, Maria Aparecida N. Jardini, Kaan Orhan, and Sérgio Lúcio Pereira de Castro Lopes. "In Vitro Quantitative Evaluation of Postprocessing Filter for Metal Artifact Reduction in Cone Beam Computed Tomography Images of Titanium and Zirconium Dioxide Implants." BioMed Research International 2022 (February 24, 2022): 1–9. http://dx.doi.org/10.1155/2022/1362473.
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Objective. To evaluate a postprocessing filter of a new imaging-processing software for analysis of metal artifact reduction. Methods. Eight artificial edentulous mandibles (phantoms), where titanium and zirconium dioxide implants had been installed in four different regions (i.e., incisors, canine, premolars, and molars). CBCT volume was acquired, and then, four types of filters were applied to the images: BAR filter and Multi-CDT NR filter (e-Vol DX) and Sharpening Filters 1x and 2x (OnDemand). Artifact was assessed by measuring the standard deviation (SD) of the gray values of filtered and unfiltered images. The comparison between implant material, teeth, and filters was performed by using ANOVA, whereas multiple comparisons were performed by using Bonferroni’s test. The level of significance adopted was 5%. Results. The results showing higher SD values, which suggests a worse image, were obtained with titanium implants compared to zirconium dioxide ones. With regard to the four filters used, it can be seen that the lowest SD values were obtained with BAR and Multi-CDT NR filters and the highest with Sharpening Filters 1x and 2x, with no statistical difference between them, except regarding the molar region in titanium implants. Conclusion. The highest SD values were seen in zirconium dioxide implants, mainly in the region of anterior teeth. The BAR filter was found to be the most effective as its SD value decreased significantly, indicating that the image quality was improved.
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Bader, Milad, Robert G. Clapp, and Biondo Biondi. "Denoising for full-waveform inversion with expanded prediction-error filters." GEOPHYSICS 86, no. 5 (August 31, 2021): V445—V457. http://dx.doi.org/10.1190/geo2020-0573.1.
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Low-frequency data of less than 5 Hz are essential to the convergence of full-waveform inversion (FWI) toward a useful solution. They help to build the velocity model low wavenumbers and reduce the risk of cycle skipping. In marine environments, low-frequency data are characterized by a low signal-to-noise ratio (S/N) and can lead to erroneous models when inverted, especially if the noise contains coherent components. Often, field data are high-pass filtered before any processing step, sacrificing weak but essential signal for FWI. We have denoised the low-frequency data using prediction-error filters that we estimate from a high-frequency component with a high S/N. The constructed filter captures the multidimensional spectrum of the high-frequency signal. We expand the filter’s axes in the time-space domain to compress its spectrum toward the low frequencies and wavenumbers. The expanded filter becomes a predictor of the target low-frequency signal, and we incorporate it in a minimization scheme to attenuate noise. To account for data nonstationarity while retaining the simplicity of stationary filters, we divide the data into nonoverlapping patches and linearly interpolate stationary filters at each data sample. We apply our method to synthetic stationary and nonstationary data, and we find that it improves the FWI results initialized at 2.5 Hz using the Marmousi model. We also demonstrate that the denoising attenuates nonstationary shear energy recorded by the vertical component of ocean-bottom nodes.
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Mazur, Krzysztof, and Marek Pawełczyk. "Active Noise Control with a Single Nonlinear Control Filter for a Vibrating Plate with Multiple Actuators." Archives of Acoustics 38, no. 4 (December 1, 2013): 537–45. http://dx.doi.org/10.2478/aoa-2013-0063.
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Abstract Vibrating plates can be used in Active Noise Control (ANC) applications as active barriers or as secondary sources replacing classical loudspeakers. The system with vibrating plates, especially when nonlinear MFC actuators are used, is nonlinear. The nonlinearity in the system reduces performance of classical feedforward ANC with linear control filters systems, because they cannot cope with harmonics generated by the nonlinearity. The performance of the ANC system can be improved by using nonlinear control filters, such as Artificial Neural Networks or Volterra filters. However, when multiple actuators are mounted on a single plate, which is a common practice to provide effective control of more vibration modes, each actuator should be driven by a dedicated nonlinear control filter. This significantly increases computational complexity of the control algorithm, because adaptation of nonlinear control filters is much more computationally demanding than adaptation of linear FIR filters. This paper presents an ANC system with multiple actuators, which are driven with a single nonlinear filter. To avoid destructive interference of vibrations generated by different actuators the control signal is filtered by appropriate separate linear filters. The control system is experimentally verified and obtained results are reported.
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Koigerov, A. S. "Analytical Approach to Designing a Combined-Mode Resonator Filter on Surface Acoustic Waves Using the Model of Coupling of Modes." Journal of the Russian Universities. Radioelectronics 25, no. 2 (April 27, 2022): 16–28. http://dx.doi.org/10.32603/1993-8985-2022-25-2-16-28.
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Introduction. Bandpass filters are important components that determine the basic characteristics of transmitting and receiving radio electronic equipment. Such filters implemented on surface acoustic waves (SAW) not only demonstrate excellent electrical parameters, but also meet compactness requirements. The relevant research task of reducing the design time and optimizing the filter’s cost can be solved by either using modern computational software or improving existing modeling tools.Aim. To describe the current state and main features of approaches to calculating SAW-based bandpass filters using the model of coupled modes and its formalization based on P-matrices. To describe the main principles and approaches on the example of designing a combined-mode resonator filter on leaky SAW and comparing the calculated and experimental data.Materials and methods. A theoretical study was carried out using the mathematical theory of differential equations presented in a matrix form, as well as the methods of finite element analysis and circuit theory. The results were processed in MatLab and COMSOL.Results. The current state of the analytical approach to designing SAW-based filters using the model of coupled modes and its formalization based on P-matrices was described. An original design for a resonator filter based on leaky SAW at 49° YX-cut of lithium niobate was proposed. The filter has a relative bandwidth of 5.8 %, an insertion loss of –3.7 dB, and a stop-band rejection of –50 dB. A technique for calculating SAW-based filters was proposed.Conclusion. The proposed analytical approach to designing SAW-based bandpass filters allows the filter characteristics (e.g., transmission factor) to be reliably predicted at the modeling stage, thereby reducing the number of experimental iterations and increasing the development efficiency.
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Koigerov, A. S. "Analytical Approach to Designing a Combined-Mode Resonator Filter on Surface Acoustic Waves Using the Model of Coupling of Modes." Journal of the Russian Universities. Radioelectronics 25, no. 2 (April 27, 2022): 16–28. http://dx.doi.org/10.32603/1993-8985-2022-25-2-16-28.
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Introduction. Bandpass filters are important components that determine the basic characteristics of transmitting and receiving radio electronic equipment. Such filters implemented on surface acoustic waves (SAW) not only demonstrate excellent electrical parameters, but also meet compactness requirements. The relevant research task of reducing the design time and optimizing the filter’s cost can be solved by either using modern computational software or improving existing modeling tools.Aim. To describe the current state and main features of approaches to calculating SAW-based bandpass filters using the model of coupled modes and its formalization based on P-matrices. To describe the main principles and approaches on the example of designing a combined-mode resonator filter on leaky SAW and comparing the calculated and experimental data.Materials and methods. A theoretical study was carried out using the mathematical theory of differential equations presented in a matrix form, as well as the methods of finite element analysis and circuit theory. The results were processed in MatLab and COMSOL.Results. The current state of the analytical approach to designing SAW-based filters using the model of coupled modes and its formalization based on P-matrices was described. An original design for a resonator filter based on leaky SAW at 49° YX-cut of lithium niobate was proposed. The filter has a relative bandwidth of 5.8 %, an insertion loss of –3.7 dB, and a stop-band rejection of –50 dB. A technique for calculating SAW-based filters was proposed.Conclusion. The proposed analytical approach to designing SAW-based bandpass filters allows the filter characteristics (e.g., transmission factor) to be reliably predicted at the modeling stage, thereby reducing the number of experimental iterations and increasing the development efficiency.
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Baki, A. K. M. "Comparison of different New Radio (NR) waveforms for wireless communications." PLOS ONE 18, no. 4 (April 3, 2023): e0283886. http://dx.doi.org/10.1371/journal.pone.0283886.
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New Radio (NR) waveforms of existing wireless communication systems need further improvement in order to support future wireless communications. NR is the radio interface technology proposed by the 3rd Generation Partnership Project (3GPP) for 5G. Prototype Filter (PF) of NR plays a vital role in performance improvement of wireless systems. NR waveforms can adapt in a better way to different channel conditions. Some of the NR filtering techniques are Filtered-OFDM (F-OFDM), Filter Bank Multi-Carrier (FBMC), and Universal Filtered Multi-Carrier (UFMC). NR waveforms require performance improvement when high reliability, massive connectivity, lower power consumption, and time-critical applications are required. Areas of improvement are Power Spectral Density (PSD), Bit Error Rate (BER), Signal to Interference Ratio (SIR), Doppler Diversity, and Peak to Average Power Ratio (PAPR). This paper compares different performance parameters of Filtered-OFDM, FBMC, and UFMC using existing proto-type filters and novel proto-type filters. The novel and better PFs, described in the paper, were proposed first time by the authors and his research group. Proposed novel prototype filters for FBMC, Filtered-OFDM, and UFMC are respectively Binomial filter and Fractional Powered Binomial Filter (FPBF). With FPBF based OFDM, PSD improvement was 97.5 dB, and BER improvement was 0.07 at 0 dB SNR. With Binomial filter based FBMC, OOBE improvement was 19.7 dB and BER improvement was 0.03 at 0 dB SNR. PAPR improvement with Binomial filter based FBMC was 1.16 dB at 64-QAM and 1.1 dB at 256-QAM. With FPBF based UFMC, improvement of interference level was 122 dB within 3rd~52th sub-bands due to 1st sub-band. BER improvement was 0.09 at 0 dB SNR. SIR improvement was 5. 27 dB with 15 KHz sub-carrier spacing and 16.55 dB with 30 KHz sub-carrier spacing of UFMC. Novel NR filters, discussed in the paper, are good candidates for future 6G wireless systems.
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Qian, Nijia, Guobin Chang, Pavel Ditmar, Jingxiang Gao, and Zhengqiang Wei. "Sparse DDK: A Data-Driven Decorrelation Filter for GRACE Level-2 Products." Remote Sensing 14, no. 12 (June 11, 2022): 2810. http://dx.doi.org/10.3390/rs14122810.
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High-frequency and correlated noise filtering is one of the important preprocessing steps for GRACE level-2 products before calculating mass anomaly. Decorrelation and denoising kernel (DDK) filters are usually considered as such optimal filters to solve this problem. In this work, a sparse DDK filter is proposed. This is achieved by replacing Tikhonov regularization in traditional DDK filters with weighted L1 norm regularization. The proposed sparse DDK filter adopts a time-varying error covariance matrix, while the equivalent signal covariance matrix is adaptively determined by the Gravity Recovery and Climate Experiment (GRACE) monthly solution. The covariance matrix of the sparse DDK filtered solution is also developed from the Bayesian and error-propagation perspectives, respectively. Furthermore, we also compare and discuss the properties of different filters. The proposed sparse DDK has all the advantages of traditional filters, such as time-varying, location inhomogeneity, and anisotropy, etc. In addition, the filtered solution is sparse; that is, some high-degree and high-order terms are strictly zeros. This sparsity is beneficial in the following sense: high-degree and high-order sparsity mean that the dominating noise in high-degree and high-order terms is completely suppressed, at a slight cost that the tiny signals of these terms are also discarded. The Center for Space Research (CSR) GRACE monthly solutions and their error covariance matrices, from January 2004 to December 2010, are used to test the performance of the proposed sparse DDK filter. The results show that the sparse DDK can effectively decorrelate and denoise these data.
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Gülünay, Necati. "Noncausal spatial prediction filtering for random noise reduction on 3-D poststack data." GEOPHYSICS 65, no. 5 (September 2000): 1641–53. http://dx.doi.org/10.1190/1.1444852.
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A common practice in random noise reduction for 2-D data is to use pseudononcausal (PNC) 1-D prediction filters at each temporal frequency. A 1-D PNC filter is a filter that is forced to be two sided by placing a conjugate‐reversed version of a 1-D causal filter in front of itself with a zero between the two. For 3-D data, a similar practice is to solve for two 2-D (causal) one‐quadrant filters at each frequency slice. A 2-D PNC filter is formed by putting a conjugate flipped version of each quadrant filter in a quadrant opposite itself. The center sample of a 2-D PNC filter is zero. This paper suggests the use of 1-D and 2-D noncausal (NC) prediction filters instead of PNC filters for random noise attenuation, where an NC filter is a two‐sided filter solved from one set of normal equations. The number of negative and positive lags in the NC filter is the same. The center sample of the filter is zero. The NC prediction filters are more center loaded than PNC filters. They are conjugate symmetric as PNC filters. Also, NC filters are less sensitive than PNC filters to the size of the gate used in their derivation. They can handle amplitude variations along dip directions better than PNC filters. While a PNC prediction filter suppresses more random noise, it damages more signal. On the other hand, NC prediction filters preserve more of the signal and reject less noise for the same total filter length. For high S/N ratio data, a 2-D NC prediction filter preserves geologic features that do not vary in one of the spatial dimensions. In‐line and cross‐line vertical faults are also well preserved with such filters. When faults are obliquely oriented, the filter coefficients adapt to the fault. Spectral properties of PNC and NC filters are very similar.
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Shaikh, Saba S., Suneel D. Kamath, Debashis Ghosh, Robert J. Lewandowski, and Brandon J. McMahon. "Safety and Outcomes of Permanent and Retrievable Inferior Vena Cava Filters in the Oncology Population." International Journal of Vascular Medicine 2020 (February 5, 2020): 1–7. http://dx.doi.org/10.1155/2020/6582742.
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Background. The role for inferior vena cava (IVC) filters in the oncology population is poorly defined. Objectives. Our primary endpoint was to determine the rate of filter placement in cancer patients without an absolute contraindication to anticoagulation and the rate of recurrent VTE after filter placement in both retrievable and permanent filter groups. Patients/Methods. A single-institution, retrospective study of patients with active malignancies and acute VTE who received a retrievable or permanent IVC filter between 2009-2013. Demographics and outcomes were confirmed on independent chart review. Cost data were obtained using Current Procedural Terminology (CPT) codes. Results. 179 patients with retrievable filters and 207 patients with permanent filters were included. Contraindication to anticoagulation was the most cited reason for filter placement; however, only 76% of patients with retrievable filters and 69% of patients with permanent filters had an absolute contraindication to anticoagulation. 20% of patients with retrievable filters and 24% of patients with permanent filters had recurrent VTE. The median time from filter placement to death was 8.9 and 3.2 months in the retrievable and permanent filter groups, respectively. The total cost of retrievable filters and permanent filters was $2,883,389 and $3,722,688, respectively. Conclusions. The role for IVC filters in cancer patients remains unclear as recurrent VTE is common and time from filter placement to death is short. Filter placement is costly and has a clinically significant complication rate, especially for retrievable filters. More data from prospective, randomized trials are needed to determine the utility of IVC filters in cancer patients.
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Piciu, Dana, Christina Theresia Dan, and Anca Dina. "Gődel filters in residuated lattices." Analele Universitatii "Ovidius" Constanta - Seria Matematica 29, no. 1 (March 1, 2021): 183–200. http://dx.doi.org/10.2478/auom-2021-0012.
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Abstract In this paper, in the spirit of [4], we study a new type of filters in residuated lattices : Gődel filters. So, we characterize the filters for which the quotient algebra that is constructed via these filters is a Gődel algebra and we establish the connections between these filters and other types of filters. Using Gődel filters we characterize the residuated lattices which are Gődel algebras. Also, we prove that a residuated lattice is a Gődel algebra (divisible residuated lattice, MTL algebra, BL algebra) if and only if every filter is a Gődel filter (divisible filter, MTL filter, BL filter). Finally, we present some results about injective Gődel algebras showing that complete Boolean algebras are injective objects in the category of Gődel algebras.
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Ajao, Isaac Oluwaseyi, Awogbemi Clement Adeyeye, and Urama Kenny Ugochukwu. "Investigating the Robustness of Filters for Integrated Processes in Business Cycles." Scholars Journal of Physics, Mathematics and Statistics 11, no. 05 (June 7, 2023): 105–12. http://dx.doi.org/10.36347/sjpms.2023.v10i05.001.
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Time series are frequently filtered to remove unwanted characteristics, such as trends and seasonal components, or to estimate components driven by stochastic cycles from a specific range of periods in a business cycle. A polynomial function of time is the most common deterministic time trend while an integrated process is the most common stochastic trend. The different filters implemented in this paper allow for different orders of deterministic time trends or integrated processes. The robustness of the filters is evaluated by plotting their gain function against the gain function of a simulated ideal filter. Implementing the filters on Nigerian gross domestic products (GDP), the results show that the gain of the Baxter-King (BK) filter deviates markedly from the square-wave gain of the ideal filter. The gain in Christiano–Fitzgerald (CF) filter is closer to the gain of the ideal filter than the BK filter. The gain in Hodrick–Prescott (HP) filter goes to one for those cycles at frequencies above six periods, whereas the other gain functions go to zero. The Butterworth (BW) filter does a reasonable job of filtering out the high-periodicity stochastic cycles but the low- periodicity stochastic cycles is not been completely removed.
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Zhang, Xiaohong. "On Some Fuzzy Filters in Pseudo-BCIAlgebras." Scientific World Journal 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/718972.
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Some new properties of fuzzy associative filters (also known as fuzzy associative pseudo-filters), fuzzyp-filter (also known as fuzzy pseudo-p-filters), and fuzzya-filter (also known as fuzzy pseudo-a-filters) in pseudo-BCIalgebras are investigated. By these properties, the following important results are proved: (1) a fuzzy filter (also known as fuzzy pseudo-filters) of a pseudo-BCIalgebra is a fuzzy associative filter if and only if it is a fuzzya-filter; (2) a filter (also known as pseudo-filter) of a pseudo-BCIalgebra is associative if and only if it is ana-filter (also call it pseudo-afilter); (3) a fuzzy filter of a pseudo-BCIalgebra is fuzzya-filter if and only if it is both a fuzzyp-filter and a fuzzyq-filter.
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Tuzova, A. A., V. A. Pavlov, and A. A. Belov. "Reduction of Multiplicative Noise in Radar Images." Journal of the Russian Universities. Radioelectronics 24, no. 4 (September 28, 2021): 6–18. http://dx.doi.org/10.32603/1993-8985-2021-24-4-6-18.
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Introduction. A radar image is an image obtained by remote sensing the earth's surface with a radar device. Radar images are characterized by background graininess caused by speckle noise, which should be filtered to improve the quality of radar images. The structure of speckle noise reduction filters often comprise one or more parameters to control the level of noise smoothing. The values of these parameters have to be selected experimentally. In works devoted to speckle noise filtering, the methods used for selecting filter paraments are rarely clarified.Aim. To present a methodology for selecting the parameters of multiplicative speckle noise filters on a radar image that are optimal in terms of the quality of the resulting image.Materials and methods. The article presents a method for determining the optimal parameters of speckle noise reduction filters. This method was applied to the most conventionally used filters. The search for optimal parameters and testing of the filters were carried out using a specially designed image, which contained the objects most frequently found on radar images. The structural similarity index (SSIM) metric was chosen as a metric that assesses the quality of filtration.Results. After determining the optimal (in terms of SSIM) parameters of speckle noise reduction filters, the filters were compared to select the best filters in terms of the quality of radar image processing. In addition, the operation of the filters under study was tested on images containing various types of objects, namely: large objects, small objects and sharp borders. Knowing which filter copes best with smoothing speckle noise in a particular area and what values of the variable parameters this requires, an optimal quality of radar images can be achieved. Filtering not only improves human perception of radar images, but also reduces the influence of speckle noise during their further processing (object detection, segmentation of areas, etc.).Conclusion. The proposed algorithm allowed optimal parameters for several speckle noise filters to be determined. The quality of filtration was assessed using an expert method (visually) by comparing images before and after filtration, differential images and one-dimensional image slices. The Frost filter and the anisotropic diffusion filter with optimal parameters showed the best processing quality according to the SSIM metric.
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Olacsi, Gary S., Joy Kempic, and Robert J. Beaton. "Image Quality of Privacy Filters for Displays." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 42, no. 22 (October 1998): 1565–69. http://dx.doi.org/10.1177/154193129804202207.
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This paper presents an image quality evaluation of privacy filters for CRT display workstations. A photometric procedure was developed to evaluate the optical quality of privacy filters across horizontal display viewing angles. Then, the procedure was applied to two commercially-available privacy filter products. The results of the optical evaluation were compared with subjective image quality judgments of the privacy-filtered CRTs viewed under various ambient illumination, screen contrast polarity, and viewing angle conditions. The findings establish a human factors basis and procedure for objectively characterizing the image quality of privacy filters used on CRT displays.
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Jurisic Bellotti, Maja, and Mladen Vucic. "Sparse FIR Filter Design Based on Signomial Programming." Elektronika ir Elektrotechnika 26, no. 1 (February 16, 2020): 40–45. http://dx.doi.org/10.5755/j01.eie.26.1.23560.
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The goal of sparse FIR filter design is to minimize the number of nonzero filter coefficients, while keeping its frequency response within specified boundaries. Such a design can be formally expressed via minimization of l0-norm of filter’s impulse response. Unfortunately, the corresponding minimization problem has combinatorial complexity. Therefore, many design methods are developed, which solve the problem approximately, or which solve the approximate problem exactly. In this paper, we propose an approach, which is based on the approximation of the l0-norm by an lp-norm with 0 < p < 1. We minimize the lp-norm using recently developed method for signomial programming (SGP). Our design starts with forming a SGP problem that describes filter specifications. The optimum solution of the problem is then found by using iterative procedure, which solves a geometric program in each iteration. The filters whose magnitude responses are constrained in minimax sense are considered. The design examples are provided illustrating that the proposed method, in most cases, results in filters with higher sparsity than those of the filters obtained by recently published methods.
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Avram, Sebastian, and Radu Vasiu. "Passive Power Line Communication Filter Design and Benchmarking Using Scattering Parameters." Applied Sciences 13, no. 11 (June 4, 2023): 6821. http://dx.doi.org/10.3390/app13116821.
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NB-PLC (narrowband power line communication) is a method of data communication that involves superimposing a relatively high-frequency signal (9 kHz to 500 kHz), which contains data, onto the power grid’s low frequency (50 to 60 Hz) signal. While using the existing power grid as a transmission medium is convenient, the power grid was not designed for this purpose, leading to challenges such as conducted emissions and infrastructure limitations. To overcome these technical challenges, passive filters are necessary. This article presents the design, simulation (using scattering parameters), and evaluation of an NB-PLC filter by comparing it to commercially available filters. Our proposed design and benchmarking methods enable the accurate prediction of the filter’s behavior in field conditions. After comparing our filter with commercially available filters, we observed that it exhibits superior characteristics. Specifically, our filter has the best insertion loss versus frequency, achieved three times higher attenuation at 50 kHz (−130 dB) compared to the best commercially available filter (−40 dB), and has a power consumption of 0.6 W, which is comparable to the most power-efficient commercial filter (0.5 W). Additionally, our filter has the second best input and output impedance of 3.6 Ω within the frequency range of 35–95 kHz.
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Shin, Woo-Jin, Hyung-Seon Shin, Ji-Hun Hwang, and Kwang-Sik Lee. "Effects of Filter-Membrane Materials on Concentrations of Trace Elements in Acidic Solutions." Water 12, no. 12 (December 12, 2020): 3497. http://dx.doi.org/10.3390/w12123497.
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Filtration is commonly used to separate liquids from solid materials before the determination of trace element concentrations in aqueous solutions. Therefore, it is important to determine how much elemental content is extracted from the filter itself or lost via absorption into the filter. In this study, we investigated three types of disposable syringe filters (polyvinylidene difluoride, PVDF; polytetrafluoroethylene, PTFE; PTFE with glass microfiber prefiltration media, GD/X) and their acid-cleaned versions using ammonium nitrate (NH4NO3) and acetic acid (HOAc) solutions. The concentrations of most trace elements (Li, Al, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Cs, Ba, Pb, and U) were higher in filtrates that had passed through acid-cleaned filters than those that had passed through uncleaned filters. In filtrates from PVDF and PTFE filters, many trace elements were below the detection limit. However, regardless of the filter type and acid cleaning, Li, Cu, Zn, Mo, and Ba concentrations in filtrates of NH4NO3 solutions, and Al, Cr, Mn, Cu, Zn, and Ba concentrations in filtrates of HOAc solutions were much higher than those of other trace elements. These differences were particularly noticeable in filtrates from GD/X filters containing glass microfiber layers. These data indicate that certain trace elements can be released from membrane materials by reacting with acid in the filtered solution. Furthermore, the amounts of each trace element were associated with the membrane type. These findings suggest that filter type should be carefully selected to obtain the required accuracy, in consideration of the target elements and whether an acid-cleaned filter is needed.
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Ma, Tengfei, Yang Li, Zhenggan Zhou, and Jia Meng. "Wrinkle Detection in Carbon Fiber-Reinforced Polymers Using Linear Phase FIR-Filtered Ultrasonic Array Data." Aerospace 10, no. 2 (February 15, 2023): 181. http://dx.doi.org/10.3390/aerospace10020181.
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Carbon fiber-reinforced polymers (CFRP) are extensively used in aerospace applications. Out-of-plane wrinkles frequently occur in aerospace CFRP parts that are commonly large and complex. Wrinkles acting as failure initiators severely damage the mechanical performance of CFRP parts. Wrinkles have no significant acoustic impedance mismatch, reflecting weak echoes. The total focusing method (TFM) using weak reflection signals is vulnerable to noise, so our primary work is to design discrete-time filters to relieve the noise interference. Wrinkles in CFRP composites are geometric defects, and their direct detection requires high spatial precision. The TFM method is a time-domain delay-and-sum algorithm, and it requires that the time information of filtered signals has no change or can be corrected. A linear phase filter can avoid phase distortion, and its filtered signal can be corrected by shifting a constant time. We first propose a wrinkle detection method using linear phase FIR-filtered ultrasonic array data. Linear phase filters almost do not affect the wrinkle geometry of detection results and can relieve noise-induced dislocation. Four filters with different bandwidths have been designed and applied for wrinkle detection. The 2 MHz bandwidth filter is recommended as an optimum choice.
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Rietjens, Judith AC, Wichor M. Bramer, Eric CT Geijteman, Agnes van der Heide, and Wendy H. Oldenmenger. "Development and validation of search filters to find articles on palliative care in bibliographic databases." Palliative Medicine 33, no. 4 (January 28, 2019): 470–74. http://dx.doi.org/10.1177/0269216318824275.
Full textAbstract:
Background: Healthcare professionals and researchers in the field of palliative care often have difficulties finding relevant articles in online databases. Standardized search filters may help improve the efficiency and quality of such searches, but prior developed filters showed only moderate performance. Aim: To develop and validate a specific search filter and a sensitive search filter for the field of palliative care. Design: We used a novel, objective method for search filter development. First, we created a gold standard set. This set was split into three groups: term identification, filter development, and filter validation set. After creating the filters in PubMed, we translated the filters into search filters for Ovid MEDLINE, Embase, CINAHL, PsychINFO, and Cochrane Library. We calculated specificity, sensitivity and precision of both filters. Results: The specific filter had a specificity of 97.4%, a sensitivity of 93.7%, and a precision of 45%. The sensitive filter had a sensitivity of 99.6%, a specificity of 92.5%, and a precision of 5%. Conclusion: Our search filters can support literature searches in the field of palliative care. Our specific filter retrieves 93.7% of relevant articles, while 45% of the retrieved articles are relevant. This filter can be used to find answers to questions when time is limited. Our sensitive filter finds 99.6% of all relevant articles and may, for instance, help conducting systematic reviews. Both filters perform better than prior developed search filters in the field of palliative care.
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Malleswari, V. S. Naga, G. Luka, Bhagyalakshmi Kothuru, T. Srinivasa Rao, and V. Amarendra Babu. "Application of Neutrosophic implicative filters and Neutrosophic positive implicative filters in Lattice implication algebra." International Journal of Neutrosophic Science 21, no. 1 (2023): 69–79. http://dx.doi.org/10.54216/ijns.210106.
Full textAbstract:
We introduced Neutrosophic implicative filters and Neutrosophic positive implicative filters in Lattice implication algebra. We proved some properties and equivalent conditions of both the filters. Finally we proved that “Every Neutrosophic positive implicative filter is a Neutrosophic implicative filter” and “Every Neutrosophic positive implicative filter is a Neutrosophic filter”.
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Li, Luping, Lijuan Dong, Peng Chen, and Kai Yang. "A low insertion loss low-pass filter based on single comb-shaped spoof surface plasmon polaritons." International Journal of Microwave and Wireless Technologies 11, no. 08 (May 28, 2019): 792–96. http://dx.doi.org/10.1017/s1759078719000564.
Full textAbstract:
AbstractThis paper presents a low insertion loss low-pass filter based on the spoof surface plasmon polariton (SSPP) with single comb-shape. Compared with traditional ones, the proposed filter provides lower insertion loss and return loss by optimizing the structural parameters of the mode conversion and SSPP parts. According to the measurement results, the average insertion loss of the fabricated filter is 0.41 dB and the return loss of which at the near-zero-hertz band is <−25.9 dB. The S parameter comparison result between the unoptimized and optimized filters demonstrates that the optimized filter provides lower insertion loss and return loss, smaller size, and better out-of-band rejection. The dispersion comparison result reveals the reasons behind the improved performances. The better performances of the optimized filter proves that breaking the regularity of traditional SSPP filters is beneficial to the filter's performances.
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Jun, Young Bae, Sun Shin Ahn, and Kyoung Ja Lee. "Classes of Int-Soft Filters in Residuated Lattices." Scientific World Journal 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/595160.
Full textAbstract:
The notions of int-soft filters, int-softG-filters, regular int-soft filters, andMV-int-soft filters in residuated lattices are introduced, and their relations, properties, and characterizations are investigated. Conditions for an int-soft filter to be an int-softG-filter, a regular int-soft filter, or anMV-int-soft filter are provided. The extension property for an int-softG-filter is discussed. Finally, it is shown that the notion of anMV-int-soft filter coincides with the notion of a regular int-soft filter inBL-algebras.
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Khriji, L. "Vector Directional Distance Rational Hybrid Filters for Color Image Restoration." Journal of Engineering Research [TJER] 2, no. 1 (December 1, 2005): 1. http://dx.doi.org/10.24200/tjer.vol2iss1pp1-12.
Full textAbstract:
A new class of nonlinear filters, called vector-directional distance rational hybrid filters (VDDRHF) for multispectral image processing, is introduced and applied to color image-filtering problems. These filters are based on rational functions (RF). The VDDRHF filter is a two-stage filter, which exploits the features of the vector directional distance filter (VDDF), the center weighted vector directional distance filter (CWVDDF) and those of the rational operator. The filter output is a result of vector rational function (VRF) operating on the output of three sub-functions. Two vector directional distance (VDDF) filters and one center weighted vector directional distance filter (CWVDDF) are proposed to be used in the first stage due to their desirable properties, such as, noise attenuation, chromaticity retention, and edges and details preservation. Experimental results show that the new VDDRHF outperforms a number of widely known nonlinear filters for multi-spectral image processing such as the vector median filter (VMF), the generalized vector directional filters (GVDF) and distance directional filters (DDF) with respect to all criteria used.