Filtering Properties Research Articles

NEW ORGANIZATION PROCESS OF FEATURE SELECTION BY FILTER WITH CORRELATION-BASED FEATURES SELECTION METHOD

The subject of the article is feature selection techniques that are used on data preprocessing step before building machine learning models. In this paper the focus is put on a Filter technique when it uses Correlation-based Feature Selection (further CFS) with symmetrical uncertainty method (further CFS-SU) or CFS with Pearson Correlation (further CFS-PearCorr). The goal of the work is to increase the efficiency of feature selection by Filter with CFS by proposing a new organization process of feature selection. The tasks which are solved in the article: review and analysis of the existing organization process of feature selections by Filter with CFS; identify the routs cause the performance degradation; propose a new approach; evaluate the proposed approach. To implement the specified tasks, the following methods were used: information theory, process theory, algorithm theory, statistics theory, sampling techniques, data modeling theory, science experiments. Results. Based on the received results are proved: 1) the chosen features subset’s evaluation function couldn’t be based only on CFS merit as it causes a learning algorithm’s results degradation; 2) the accuracies of the classification learning algorithms had improved and the values of determination coefficient of the regression leaning algorithms had increased when features are selected according to the proposed new organization process. Conclusions. A new organization process for feature selection which is proposed in current work combines filter and learning algorithm properties in evaluation strategy which helps to choose the optimal feature subset for predefined learning algorithm. The computation complexity of the proposed approach to feature selection doesn’t depend on dataset’s dimensions which makes it robust to different data varieties; it eliminates the time needed for feature subsets’ search as subsets are selected randomly. The conducted experiments proved that the performance of the classification and regression learning algorithms with features selected according to the new flow had outperformed the performance of the same learning algorithms built with without applied new process on data preprocessing step.

Direction Selectivity of TmY Neurites in Drosophila.

The perception of motion is an important function of vision. Neural wiring diagrams for extracting directional information have been obtained by connectome reconstruction. Direction selectivity in Drosophila is thought to originate in T4/T5 neurons through integrating inputs with different temporal filtering properties. Through genetic screening based on synaptic distribution, we isolated a new type of TmY neuron, termed TmY-ds, that form reciprocal synaptic connections with T4/T5 neurons. Its neurites responded to grating motion along the four cardinal directions and showed a variety of direction selectivity. Intriguingly, its direction selectivity originated from temporal filtering neurons rather than T4/T5. Genetic silencing and activation experiments showed that TmY-ds neurons are functionally upstream of T4/T5. Our results suggest that direction selectivity is generated in a tripartite circuit formed among these three neurons-temporal filtering, TmY-ds, and T4/T5 neurons, in which TmY-ds plays a role in the enhancement of direction selectivity in T4/T5 neurons.

The spectra of quasi-Boolean algebras

Abstract In the present paper, we introduce the notions of quasi-Boolean algebras as the generalization of Boolean algebras. First we discuss the related properties of quasi-Boolean algebras. Second we define filters of quasi-Boolean algebras and investigate some properties of filters in quasi-Boolean algebras. We also show that there is a one-to-one correspondence between the set of filters and the set of filter congruences on a quasi-Boolean algebra. Then we investigate the prime filters and maximal filters of quasi-Boolean algebras, showing that the prime filters of a quasi-Boolean algebra are precisely the maximal filters and the prime spectrum of a quasi-Boolean algebra is a compact Hausdorff topological space. Finally, we define and study the reticulation of a quasi-Boolean algebra.

Structure and Analysis of Properties of Basic Comb Filters for Automatic Systems

The paper considers the issues of using comb filters (CF), known in radio engineering, as an alternative to continuous corrective filters, when they are implemented in controllers in automatic control systems. The convenience of their implementation in controllers is associated with the organization of a fixed number of sample passes in the processed signal. In this paper, the properties of two types of comb filters of the first order are highlighted and studied in detail: a high-frequency filter and a proportional (forming) filter. The characteristics of these filters are taken as a basis for the implementation of more complex characteristics of corrective devices in combination with numerical integration algorithms. The analysis of the properties of CF was carried out in the frequency domain. It is shown that the initial sections of the frequency characteristics of the CF at certain filter parameters coincide well with the continuous analogues of such devices. It is these areas of frequency characteristics, limited by the cutoff frequency of the open system, that determine the coincidence of static and dynamic properties of the synthesized system. It is shown that CF reduces on 30 % the level of the standard deviation (RMS) of uniformly distributed white noise at the filter output. The decrease in the level of RMS occurs due to the presence of periodically recurring dips in the amplitude-frequency response (frequency response) of filters forming a so-called comb. Due to the fact that the filters in question "cut out" harmonics in the output signal spectrum that are multiples of the inverse of the total duration of the transmitted reference intervals, then a special choice of this duration can not only reduce the level of the random signal at the CF output, but at the same time significantly reduce the level of regular interference, if it is present. Such filters can be simultaneously used as amplitude modulated signal demodulators.

One-Dimensional Dyadic Wavelets

One-Dimensional Dyadic Wavelets

Fabrication of thermally stable mid-infrared optical filters using tantalum microdisc array

To fabricate a thermally stable optical filter in the mid-infrared (MIR) region, a plasmonic metal disk array (PMDA) using tantalum (Ta) was proposed, and the filter performance was compared with that of conventional silver (Ag)-based PMDAs. A finite-difference time-domain method was utilized to systematically analyze the effects of geometric configuration and constituent materials on the optical properties of PMDA filters with a periodic hexagonal lattice. Unlike the Ag PMDA filters, whose transmission dip at resonance wavelengths gradually decreased with increasing temperature, the Ta PMDA filters revealed almost the same transmission spectra even after annealing at 700 °C for 30 min. The Ta-based MIR PMDA filter exhibited similar optical properties to those of the Ag PMDA. The PMDAs with a duty cycle (d.c.) of 60% exhibited stop band spectra with sufficiently deep dip and wide linewidth. MIR filters fabricated with the Ta disks were demonstrated to quantify different types of alcohols through the monitoring of transmission spectra.

Synthesis of dibenzoylmethane-flavonoid hybrids as potential uv filters. Hybrids of chalcones

Background: It has been reported that chalcones (a family of flavonoids) have activity as UV rays absorbers. Previously we have reported that the compounds2´-hydroxy-4- methoxychalcone and 2´-hydroxy-4-methoxy dibenzoylmethane have the basic properties of UVA filters (both show their maximum absorption in the range 350-370 nm with good photostability) Objective: in this work, we describea new series of chalcone-dibenzoylmethane hybrid candidates as synthetic UV filtersand flavonoids Method: The compounds resultedfrom multi step synthesisstarting from 4-formylbenzoic acid and 2´- hydroxy acetophenone. Purification was done by recrystallization or column chromatography. Results: The compounds were obtained with good yields and characterized by spectroscopy. Conclusion: They are good candidates for UVA filters in cosmetics. Drs. Svarc and Minaberry will performthe corresponding photostability studies.

Adaptive Filtering for the Maternal Respiration Signal Attenuation in the Uterine Electromyogram.

The electrohysterogram (EHG) is the uterine muscle electromyogram recorded at the abdominal surface of pregnant or non-pregnant woman. The maternal respiration electromyographic signal (MR-EMG) is one of the most relevant interferences present in an EHG. Alvarez (Alv) waves are components of the EHG that have been indicated as having the potential for preterm and term birth prediction. The MR-EMG component in the EHG represents an issue, regarding Alv wave application for pregnancy monitoring, for instance, in preterm birth prediction, a subject of great research interest. Therefore, the Alv waves denoising method should be designed to include the interference MR-EMG attenuation, without compromising the original waves. Adaptive filter properties make them suitable for this task. However, selecting the optimal adaptive filter and its parameters is an important task for the success of the filtering operation. In this work, an algorithm is presented for the automatic adaptive filter and parameter selection using synthetic data. The filter selection pool comprised sixteen candidates, from which, the Wiener, recursive least squares (RLS), householder recursive least squares (HRLS), and QR-decomposition recursive least squares (QRD-RLS) were the best performers. The optimized parameters were L = 2 (filter length) for all of them and λ = 1 (forgetting factor) for the last three. The developed optimization algorithm may be of interest to other applications. The optimized filters were applied to real data. The result was the attenuation of the MR-EMG in Alv waves power. For the Wiener filter, power reductions for quartile 1, median, and quartile 3 were found to be −16.74%, −20.32%, and −15.78%, respectively (p-value = 1.31 × 10−12).

Influence of stress-level due to self-weight on the hydraulic conductivity of permeable concrete for geotechnical applications

Permeable concrete is effectively used in many fields of civil and environmental engineering, including some geotechnical applications such as drainage piles, deep drainage trenches, and as a permeable backfill material for retaining walls. The principal requirements that a pervious concrete must have for geotechnical applications are those that simultaneously guarantee enough hydraulic conductivity and good filter properties against internal erosion of the soil in which the drains are realised. These requirements can be effectively achieved through special mix-designs in which a non-negligible amount of sand is added to the aggregates, unlike the permeable concretes used for example in the road construction sector where the aggregates are essentially made only of gravel and the concrete is a “no-fines” concrete. The permeability of the pervious concrete depends on many factors among which the stress level due to the self weight of the column of fresh concrete when the depth of the same column is non negligible, as it is in the geotechnical applications. Results of an experimental study on this aspect are reported in the paper. These results show that the hydraulic conductivity reduced with the vertical stress level due to the self weight of the fresh permeable concrete. This reduction is very significant in the range of vertical stress σv of 1–100 kPa (that correspond to the self-weight of a column of “classical” fresh pervious concrete h* ranging from about 0.1 to 6 m). Subsequently this reduction is less marked up to the maximum stress level reached in the tests (σv=700kPa, h* about 40 m). The minimum hydraulic conductivity (hydraulic conductivity for σv=700kPa) is, however, still sufficient and adequate for draining medium to fine-grained base soils (soil near piles or trench drains) such as clays, silty-clays, sandy-silts, silty-sands, and fine sands.

Mathematical Modelling of Diffusion Flows in Two-Phase Stratified Bodies with Randomly Disposed Layers of Stochastically Set Thickness

The work is dedicated to mathematical modelling of random diffusion flows of admixture particles in a two-phase stratified strip with stochastic disposition of phases and random thickness of inclusion-layers. The study of such models are especially important during the creation of composite layered materials, in the research of the transmission properties of filters, and in the prediction of the spread of pollutants in the environment. Within the model we consider one case of uniform distribution of coordinates of upper boundaries of the layers of which the body is made up and two more cases, i.e., of uniform and triangular distributions of the inclusion thickness. The initial-boundary value problems of diffusion are formulated for flux functions; the boundary conditions at one of the body’s surfaces are set for flux and, at the other boundary, the conditions are given for admixture concentration; the initial condition being concerned with zero and non-zero constant initial concentrations. An equivalent integro-differential equation is constructed. Its solution is found in terms of Neumann series. For the first time it was obtained calculation formulae for diffusion flux averaged over the ensemble of phase configurations and over the inclusion thickness. It allowed to investigate the dependence of averaged diffusion fluxes on the medium’s characteristics on the basis of the developed software. The simulation of averaged fluxes of admixture in multilayered Fe−Cu and αFe−Ni materials is made. Comparative analysis of solutions, depending on the stage of averaging procedure over thickness, is carried out. It is shown that for some values of parameters the stage of averaging procedure over thickness has almost no effect on the diffusion flow value.

Influence of Operational Strategies for the Recovery of Magnesium Hydroxide from Brines at a Pilot Scale.

The continuous depletion of minerals caused by land mining and the increase in their demand have pushed the development of novel sustainable technological processes for mineral recovery from unconventional sources. In this context, magnesium (Mg) has gained considerable attention for its peculiar properties and high relevance of its compounds, such as magnesium hydroxide, Mg(OH)2. In the present work, the influence of several operating conditions on the Mg(OH)2 precipitation process was thoroughly investigated by adopting a novel multiple feed-plug flow reactor. The influence of (i) initial Mg2+ concentrations in the feed stream; (ii) brine and alkaline flow rates; and (iii) the product recycling strategy (seeded crystallization) was considered. The results marked the possibility of improving sedimentation and filterability properties of Mg(OH)2 suspensions by adopting the recycling strategy to overcome industrial issues associated with the production of Mg(OH)2 suspensions using NaOH solutions.

Effects of sintering temperature on the filtration and mechanical properties of ceramic water filters

Effects of sintering temperature on the filtration and mechanical properties of ceramic water filters

Investigations on Complementary Split Ring Resonator (CSRR) array integrated printed conformal band pass filters for modern wireless communication applications

This paper presents the performance analysis of two different conformal band pass filters (BPFs) loaded with an array of circular complementary split ring resonators (CSRRs). Type-1 bandpass filter has been designed by integrating a 9 × 9 array of circular complementary split ring resonator on the bottom layer of the filter. Similarly, Type-2 bandpass filter has been constructed by loading an array of 5 × 5 split ring resonator on the patch layer of the filter. A comparative study between Type-1 and Type-2 bandpass filters are also evaluated that shows dual pass bands for Type-1 filter and triple pass bands for the Type-2 bandpass filter. Furthermore, the conformality of both bandpass filters are judged through bending deformation analysis with various bending positions at 15°, 30°, 45°, 60° and 90°. During the bending performance analysis, the suggested BPFs retains the dual and triple pass band characteristics without any major deviations in its characteristic's parameters. Various performance parameters like return loss, insertion loss, group delay, bandwidth, and quality factor are measured. Detailed analysis of E and H field distributions and surface current distributions are also presented. The Type-2 bandpass filter shows better performance in terms of filter properties compared to Type-1 band pass filter. Hence, the prototype of Type-2 filter with an area of 30 × 30 mm2 is fabricated and measured. The validated results are agreed with the simulated results which confirms the applicability of the proposed filter for several modern wireless communication applications such as Wi-Max and personal communication systems (PCS) applications.

Noise reduction and feature enhancement of hob vibration signal based on parameter adaptive VMD and autocorrelation analysis

The vibration signal of the hobbing machine is susceptible to changes in the frequency domain distribution owing to the influence of the machine’s inherent vibration and random pulses, which affects the condition monitoring and wear prediction of the hobbing machine. Variational mode decomposition (VMD) can compensate for the mode mixing problem of ensemble empirical mode decomposition method owing to its inherent equivalent filtering property. However, the decomposition performance of VMD depends heavily on two hyperparameters that need to be set in advance, i.e. the number of bandwidth-limited intrinsic mode functions (BLIMFs) K and the penalty factor α. Thus, a hybrid signal denoising and feature enhancement method based on parameter adaptive variational mode decomposition (PAVMD) and autocorrelation analysis is proposed in this study. First, a gradient-based optimizer is introduced to optimally select the decomposition parameter of VMD, and then a series of BLIMFs are obtained via VMD. Further, an evaluation criterion called enhanced periodic modulation intensity based on autocorrelation analysis is built to quantify the noise-related degree of each BLIMF. Finally, the denoised signal is obtained based on the proposed reconstruction strategy. The comparison with other methods in both the simulation and the actual signal analysis reveals that the proposed method has a better performance in terms of eliminating the high-frequency noise, reserving higher effective frequencies, and the evaluation indicator.

All-fiber wavelength-tunable mode-locked cylindrical vector beams laser based on multimode interference

Cylindrical vector beams (CVBs) are of increasing concern due to their polarization and axially symmetrical distribution of field intensity. In this paper, we report for the first time an all-fiber single- and dual-wavelength tunable CVBs fiber laser using the nonlinear optical saturation absorption characteristics and filtering properties of nonlinear multimode interference (NL-MMI). In the experiment, the central wavelength of mode-locked CVBs fiber laser can be tuned from 1541 nm to 1564 nm at single-wavelength and from 1542.8 and 1562.925 nm to 1546.52 and 1563.86 nm at dual-wavelength. This NL-MMI-based wavelength-tunable ultrashort pulse CVBs fiber laser has excellent development prospects in optical communication.

Role of harvest depth filtration in controlling product-related impurities for a bispecific antibody.

BackgroundBispecific antibodies (BsAb) belong to a novel antibody category with advantages over traditional mono-specific therapeutic antibodies. However, product variants are also commonly seen during the production of BsAb, which poses significant challenges to downstream processing. In this study, the adsorptive characteristics of a BsAb product and its variants were investigated for a set of depth filters during primary recovery of the cell culture fluid.MethodsThe retention of the BsAb product and its variants on a set of Millistak+® D0HC and X0HC depth filters were first investigated, followed by studying the mechanism of their adsorption on the depth filters. The chemical and structural properties of depth filters along with the molecular properties of the product and its variants were studied subsequently.ResultsThe X0HC filter was found to be able to retain a significant amount of low molecular weight (LMW) variants along with a low amount of main product retained. Different levels of retention, observed for these variants, were correlated to their different hydrophobic and charge characteristics in relation with the adsorptive properties of the depth filters used. Electrostatic, hydrophobic, and hydrogen bonding interactions were found to be the key forces to keep product variants retained on the depth filter where the higher hydrophobicity of the LMW variants may cause them to be preferentially retained.ConclusionHarvest depth filters potentially can be utilized for retaining the BsAb variants, which depends on relative molecular properties of the product and its variants and adsorptive properties of the depth filters used.

From gradient-index to step-index filters: A switch between the two types of photonic crystals induced by the amplitude and period of sinusoidal function applied during high-temperature anodisation of aluminium

Porous anodic alumina (PAA) holds promise for the realisation of high-quality optical filters with first-order photonic stop-bands (PSBλ1) located in the infrared spectral region, thereby expanding the possibility of its application in photonics and light-based industries. High-temperature (30 °C) sinusoidal pulse anodisation (SPA) of aluminium was applied to fabricate PAA with PSBλ1 in the range of 800–2500 nm. The systematic increase in the anodisation period (tp) and amplitude (A) caused a significant change in the optical properties of the PAAs, which were monitored by both transmittance and reflectance measurements. A switch from gradient-index to step-index optical filters was observed when A and tp were increased from the lowest (5 V and 100 s, respectively) to the highest (15 V and 300 s, respectively) values. The switch was ascribed to the transition between different self-ordering regimes. The finest filtering properties (PSBλ1 reflectance close to 100 %) were achieved when the SPA proceeded between diffusion and kinetic regimes, providing a better porosity/refractive index contrast within the periodic structure. The analysis under polarised light confirmed both the excellent filtering properties of the PAAs and the asymmetrical light reflectance produced through the robust and cost-effective SPA process.

Filtering properties of Hodgkin–Huxley neuron on different time-scale signals

Neurons can be excited and inhibited by filtered signals. The filtering properties of neural networks have a huge impact on memory, learning, and disease. In this paper, the frequency selection of Hodgkin–Huxley (HH) neuron in response to band-pass filtered signals is investigated. It is found that the neuronal filtering property depends on the locking relationship between the band-pass filtered signal’s center frequency and the neuronal natural frequency. The natural firing frequency is a combination of the fundamental component and the various level harmonic components. The response of the neuron to the band-pass filtered signal is related to the amplitude of the harmonic components. Neuron responds better to the low-frequency filtered signals than the high-frequency filtered signals because of the reduction in the harmonic component amplitude. The filtering ability of the neuron can be modulated by the excitation level, and is stronger around the excitation threshold. Our results might provide novel insights into the filtering properties of neural networks and guide the construction of artificial neural networks.

Experimental measurement of respiratory particles dispersed by wind instruments and analysis of the associated risk of infection transmission

Activities such as singing or playing a wind instrument release respiratory particles into the air that may contain pathogens and thus pose a risk for infection transmission. Here we report measurements of the size distribution, number, and volume concentration of exhaled particles from 31 healthy musicians playing 20 types of wind instruments using aerosol size spectrometry complemented with in-line holography in a strictly controlled cleanroom environment. We find that playing wind instruments carries a lower risk of airborne disease transmission than speaking or singing. We attribute this to the fact that the resonators of wind instruments act as filters for particles >10µm in diameter, which were found in high abundance right after a brass mouthpiece but very rarely at the instrument bell end. We have also measured the size-dependent filtering properties of different types of filters that can be used as instrument masks. Based on these measurements, we calculated the risk of airborne transmission of SARS-CoV-2 in different near- and far-field scenarios with and without masking and/or distancing. We conclude that in all cases where there is a possibility that the musician is infectious, the only safe measure to prevent airborne transmission of the disease is the use of well-fitting and well-filtering masks for the instrument and the susceptible person.

Enhanced frequency-adaptive self-tuning filter-based continuous terminal sliding mode control of single-phase dynamic voltage restorer

This paper presents a continuous terminal sliding mode controller (CTSMC) for single-phase dynamic voltage restorers (DVRs). The presented controller can substantially eliminate the chattering compared to the first-order sliding mode counterpart while achieving faster convergence speed compared to the super twisting counterpart. Moreover, the continuous control signal enables the voltage source inverter to operate at constant switching frequency. As the reference compensation voltage generator, an enhanced single-phase self-tuning (SP-STF) filter is also proposed. The SP-STF has excellent band-pass filtering property, can completely attenuate DC offset and has fast dynamic response. The SP-STF has been made frequency-adaptive through unknown grid frequency estimation under a delayed-based linear regression framework. Comprehensive stability analysis of the controller and filter are presented. Experimental studies are performed to demonstrate the effectiveness of the proposed comprehensive control solution. Comparative simulation studies are also provided to highlight the advantages of the proposed approach. Results show that the proposed technique can quickly detect and compensate for any grid voltage fluctuations and helps to maintain constant voltage at the load side despite voltage sag/swell and distortions.