Suitable Filter Research Articles

Study of partial discharge characteristics at repetitive square voltages based on UHF method

Due to overvoltage produced by inverter output, inverter-fed motor insulation systems often experience fast electrical aging process, especially when partial discharge (PD) is incepted. Before putting into use, the PD detection should be performed on inverter-fed motors at repetitive square voltages to avoid the PD caused insulation deterioration when the motors are collected to inverters having specific characteristics. However, unlike PD tests at AC/DC voltages proposed in IEC 60270, the PD detection at repetitive square voltages is much more complex because of serious interference generated by impulse generator. To solve the problem, ultra-high frequency (UHF) method seems recommendable for its preferable signal-to-noise ratio (SNR). The chief aim of this study is to investigate PD pulse and statistical characteristics of turn-to-turn insulation for inverter-fed traction motors. A square-shaped Archimedes antenna, specially designed for the PD detection at repetitive square voltages of fast rise times, was used to perform PD tests on turn-to-turn insulation models. Time and frequency analysis results indicate that energy component of generator disturbance and PD pulses are mainly distributed in the 0–0.5 GHz and 0.6–1.5 GHz range, respectively. Based on the results, suitable filter was designed for power disturbance suppression. Additionally, resorting to the sensor unit (i.e. antenna and filter) and the PD test system, the PD statistical features at square voltages of different frequencies were obtained. Experimental results show that higher frequency will give rise, statistically, to PD of lower magnitudes distributing at smaller phases. A reasonable interpretation of this phenomenon was presented. Lastly, according to the PD statistical features, some suggestions for the PD detection system design, generator parameter optimization and the PD pulse extracting were given. The results of this work would be beneficial to the increase of the sensitivity when performing the PD detection on insulation systems for inverter-fed motors at repetitive square voltages and thus, improving the reliability of inverter-fed motors.

Combined Edge Segment Texture Analysis for the Detection of Damaged Buildings in Crisis Areas

This paper describes the results of a new combined method that consists of a cooperative approach of several different algorithms for automated change detection. These methods are based on isotropic frequency filtering, spectral and texture analysis, and segmentation. For the frequency analysis, different band pass filters are applied to identify the relevant frequency information for change detection. After transforming the multitemporal images using a fast Fourier transform and applying the most suitable band pass filter to extract changed structures, we apply an edge detection algorithm in the spatial domain. For the texture analysis, we calculate the parameters energy and homogeneity for the multitemporal datasets. Then a principal component analysis is applied to the new multispectral texture images and subtracted to get the texture change information. This method can be combined with spectral information and prior segmentation of the image data as well as with morphological operations for a final binary change result. A rule-based combination of the change algorithms is applied to calculate the probability of change for a particular location. This Combined Edge Segment Texture (CEST) method was tested with high-resolution remote-sensing images of the crisis area in Darfur (Sudan). Our results were compared with several standard algorithms for automated change detection, such as image difference, image ratio, principal component analysis, multivariate alteration detection (MAD) and post classification change detection. CEST showed superior accuracy compared to standard methods.

CEST ANALYSIS: AUTOMATED CHANGE DETECTION FROM VERY-HIGH-RESOLUTION REMOTE SENSING IMAGES

Abstract. A fast detection, visualization and assessment of change in areas of crisis or catastrophes are important requirements for coordination and planning of help. Through the availability of new satellites and/or airborne sensors with very high spatial resolutions (e.g., WorldView, GeoEye) new remote sensing data are available for a better detection, delineation and visualization of change. For automated change detection, a large number of algorithms has been proposed and developed. From previous studies, however, it is evident that to-date no single algorithm has the potential for being a reliable change detector for all possible scenarios. This paper introduces the Combined Edge Segment Texture (CEST) analysis, a decision-tree based cooperative suite of algorithms for automated change detection that is especially designed for the generation of new satellites with very high spatial resolution. The method incorporates frequency based filtering, texture analysis, and image segmentation techniques. For the frequency analysis, different band pass filters can be applied to identify the relevant frequency information for change detection. After transforming the multitemporal images via a fast Fourier transform (FFT) and applying the most suitable band pass filter, different methods are available to extract changed structures: differencing and correlation in the frequency domain and correlation and edge detection in the spatial domain. Best results are obtained using edge extraction. For the texture analysis, different 'Haralick' parameters can be calculated (e.g., energy, correlation, contrast, inverse distance moment) with 'energy' so far providing the most accurate results. These algorithms are combined with a prior segmentation of the image data as well as with morphological operations for a final binary change result. A rule-based combination (CEST) of the change algorithms is applied to calculate the probability of change for a particular location. CEST was tested with high-resolution satellite images of the crisis areas of Darfur (Sudan). CEST results are compared with a number of standard algorithms for automated change detection such as image difference, image ratioe, principal component analysis, delta cue technique and post classification change detection. The new combined method shows superior results averaging between 45% and 15% improvement in accuracy.

Investigation on the Effect of Properties of the Filler on the Efficiency of the Separation of Water-Petroleum Emulsions

Abstract. The aim of the present paper is to select suitable filtering material which would be effective for the separation of the aqueous petroleum emulsion. Furthermore, the paper discusses the principles and conditions for separation using filtering materials of different natures. During the experiments, the influences of several factors on the degree of separation were studied: 1) filler material 2) period of contact between emulsion and filler (by varying the model emulsion feeding rate and reactor size) 3) emulsion flow direction through the reactor (to study the effect of gravitation during separation). The experiments were performed with a cylindrical reactor. It was found that the effective separation of water and petroleum requires periods of contact between the emulsion and the filler. Besides, filler should have both hydrophilic and hydrophobic properties.

Experimental Schmidt Decomposition and State Independent Entanglement Detection

We introduce an experimental procedure for the detection of quantum entanglement of an unknown quantum state with a small number of measurements. The method requires neither apriori knowledge of the state nor a shared reference frame between the observers and can thus be regarded as a perfectly state-independent entanglement witness. The scheme starts with local measurements, possibly supplemented with suitable filtering, which essentially establishes the Schmidt decomposition for pure states. Alternatively we develop a decision tree that reveals entanglement within few steps. These methods are illustrated and verified experimentally for various entangled states of two and three qubits.

Retention performance of woven geotextiles subjected to cyclic-flow conditions

ABSTRACT: Woven geotextiles are widely used as filters in geotechnical, hydraulic, and environmental applications. Depending on the application, geotextile filters can be subjected to uni-directional, bi-directional, or cyclic-flow conditions, with cyclic flow occurring in two directions repeatedly over time. The selection of a suitable geotextile filter is of critical importance, particularly for cyclic-flow conditions. Cyclic-flow conditions can rapidly lead to an excessive loss of fine soil particles and failure of a soil–geotextile system. Although these conditions are frequently encountered, limited work has been done to evaluate the retention behavior of geotextiles under cyclic-flow conditions. In this study, the retention performance of nine different woven geotextiles with five different soils under cyclic-flow conditions was modeled using a bi-directional hydrodynamic filtration test (BHFT). Based on the results of this research, a retention criterion of AOS/d85 of 1.62 is proposed for woven geotextiles subjected to cyclic-flow conditions, where AOS is the apparent opening size of the geotextile or O95 as determined by dry sieving ( ASTM D4751 ) and d85 is the soil particle diameter corresponding to 85% by weight of finer soil particles. Additionally, an allowable soil-loss limit less than 5000 g/m2 is proposed.

Efficiency of Bark, Activated Charcoal, Foam and Sand Filters in Reducing Pollutants from Greywater

Greywater is a potential resource of water that can be improved to meet the quality needed for irrigation. This study evaluated the performance of bark, activated charcoal, polyurethane foam and sand filters in removing biochemical oxygen demand (BOD5), surfactants, phosphorus, nitrogen and microbial indicators from greywater during start-up and steady state. In column experiments, 0.6 m high filters (diameter 20 cm) were fed for 113 days with artificial greywater at a hydraulic loading rate of 0.032 m3 m−2 day−1 and an organic loading rate of 0.014 kg BOD5 m−2 day−1. Bark and activated charcoal efficiently reduced the concentrations of organics (BOD5), surfactants (methylene blue active substances—MBAS), total phosphorus (Tot-P) and total thermotolerant coliform numbers, while sand and foam were less efficient. Bark, activated charcoal, foam and sand reduced influent BOD5 by 98, 97, 37 and 75 %; MBAS by >99, >99, 73 and 96 %; Tot-P by 97, 91, 36 and 78 %; and total nitrogen by 19, 98, 13 and 5 %, respectively. BOD5 and MBAS were efficiently reduced directly from start-up by bark and activated charcoal, while foam needed 30 days to achieve about 50 % reduction in BOD5. Bark was the most efficient filter in reducing thermotolerant faecal coliforms (2.4 log10), while foam achieved the lowest reduction (0.5 log10). Overall, bark and activated charcoal filters appeared to be the most suitable filters for improving greywater quality to reach irrigation quality in terms of organic matter reduction. Performance of these filters under higher and fluctuating loadings and the long-term sustainability of the filter materials need further investigation.

Optimization of x-ray spectra in digital mammography through Monte Carlo simulations

In this work, a Monte Carlo code was used to investigate the performance of different x-ray spectra in digital mammography, through a figure of merit (FOM), defined as , with CNR being the contrast-to-noise ratio in image and being the average glandular dose. The FOM was studied for breasts with different thicknesses t (2 cm ⩽t ⩽ 8 cm) and glandular contents (25%, 50% and 75% glandularity). The anode/filter combinations evaluated were those traditionally employed in mammography (Mo/Mo, Mo/Rh, Rh/Rh), and a W anode combined with Al or K-edge filters (Zr, Mo, Rh, Pd, Ag, Cd, Sn), for tube potentials between 22 and 34 kVp. Results show that the W anode combined with K-edge filters provides higher values of FOM for all breast thicknesses investigated. Nevertheless, the most suitable filter and tube potential depend on the breast thickness, and for t ⩾ 6 cm, they also depend on breast glandularity. Particularly for thick and dense breasts, a W anode combined with K-edge filters can greatly improve the digital technique, with the values of FOM up to 200% greater than that obtained with the anode/filter combinations and tube potentials traditionally employed in mammography. For breasts with t < 4 cm, a general good performance was obtained with the W anode combined with 60 μm of the Mo filter at 24–25 kVp, while 60 μm of the Pd filter provided a general good performance at 24–26 kVp for t = 4 cm, and at 28–30 and 29–31 kVp for t = 6 and 8 cm, respectively.

Easy lambda-terms are not always simple

A closed λ -term M is easy if, for any other closed term N , the lambda theory generated by M = N is consistent. Recently, it has been introduced a general technique to prove the easiness of λ -terms through the semantical notion of simple easiness. Simple easiness implies easiness and allows to prove consistency results via construction of suitable filter models of λ -calculus living in the category of complete partial orderings: given a simple easy term M and an arbitrary closed term N , it is possible to build (in a canonical way) a non-trivial filter model which equates the interpretation of M and N . The question whether easiness implies simple easiness constitutes Problem 19 in the TLCA list of open problems. In this paper we negatively answer the question providing a non-empty co-r.e. (complement of a recursively enumerable) set of easy, but not simple easy, λ -terms.

Nonlinear refractive index measuring using a double-grating interferometer in pump–probe configuration and Fourier transform analysis

In this paper, we have presented a simple, stable, highly sensitive and timesaving method based on a double-grating interferometer in conjunction with a pump–probe technique for measuring the nonlinear refractive index. A pump laser beam is aligned collinearly with an expanded plane parallel probe beam by a dichroic mirror. These beams pass through the sample, while right behind the sample using a suitable bandpass filter the pump beam is intercepted. The distorted probe beam then passes through a double-grating interferometer. One of the lateral shearing interference patterns is recorded by use of a CCD camera and, after digitization, has been stored in a computer. The interference pattern is analyzed by means of a Fourier transform algorithm. The refractive index changes have been obtained from phase distribution of the recorded fringe patterns. The implementation of the technique is straightforward and the arrangement is very simple and stable yet its sensitivity is comparable with other interferometry methods. It is also not a time consuming method. The method is applied for measuring the thermal nonlinear refractive index n2 of colloidal gold nanoparticles in water solution.

A filtering method to correct time-lapse 3D ERT data and improve imaging of natural aquifer dynamics

Abstract We have developed a processing methodology that allows crosshole ERT (electrical resistivity tomography) monitoring data to be used to derive temporal fluctuations of groundwater electrical resistivity and thereby characterize the dynamics of groundwater in a gravel aquifer as it is infiltrated by river water. Temporal variations of the raw ERT apparent-resistivity data were mainly sensitive to the resistivity (salinity), temperature and height of the groundwater, with the relative contributions of these effects depending on the time and the electrode configuration. To resolve the changes in groundwater resistivity, we first expressed fluctuations of temperature-detrended apparent-resistivity data as linear superpositions of (i) time series of river-water-resistivity variations convolved with suitable filter functions and (ii) linear and quadratic representations of river-water-height variations multiplied by appropriate sensitivity factors; river-water height was determined to be a reliable proxy for groundwater height. Individual filter functions and sensitivity factors were obtained for each electrode configuration via deconvolution using a one month calibration period and then the predicted contributions related to changes in water height were removed prior to inversion of the temperature-detrended apparent-resistivity data. Applications of the filter functions and sensitivity factors accurately predicted the apparent-resistivity variations (the correlation coefficient was 0.98). Furthermore, the filtered ERT monitoring data and resultant time-lapse resistivity models correlated closely with independently measured groundwater electrical resistivity monitoring data and only weakly with the groundwater-height fluctuations. The inversion results based on the filtered ERT data also showed significantly less inversion artefacts than the raw data inversions. We observed resistivity increases of up to 10% and the arrival time peaks in the time-lapse resistivity models matched those in the groundwater resistivity monitoring data.

Use of Astronomy Filters in Fluorescence Microscopy

Monochrome astronomy filters are well suited for use as excitation or suppression filters in fluorescence microscopy. Because of their particular optical design, such filters can be combined with standard halogen light sources for excitation in many fluorescent probes. In this "low energy excitation," photobleaching (fading) or other irritations of native specimens are avoided. Photomicrographs can be taken from living motile fluorescent specimens also with a flash so that fluorescence images can be created free from indistinctness caused by movement. Special filter cubes or dichroic mirrors are not needed for our method. By use of suitable astronomy filters, fluorescence microscopy can be carried out with standard laboratory microscopes equipped with condensers for bright-field (BF) and dark-field (DF) illumination in transmitted light. In BF excitation, the background brightness can be modulated in tiny steps up to dark or black. Moreover, standard industry microscopes fitted with a vertical illuminator for examinations of opaque probes in DF or BF illumination based on incident light (wafer inspections, for instance) can also be used for excitation in epi-illumination when adequate astronomy filters are inserted as excitatory and suppression filters in the illuminating and imaging light path. In all variants, transmission bands can be modulated by transmission shift.

Signal Filtering in PID Control

The major input signals entering the PID controller are; the set point, the process output, and measurable load disturbances. By feeding these signals through suitable filters, the properties of the feedback loop can be improved significantly. This presentation will treat set point handling, feedforward from load disturbances, TITO (two input two output) control, noise filtering, and process dynamics compensation. An industrial case from the steel industry is also discussed.

Particle swarm optimisation for power quality improvement of a 12-pulse rectifier-chopper fed LCI-synchronous motor drive

This paper investigates the optimised passive filter combination for power quality improvement of a 12-pulse rectifier-chopper fed load commutated inverter LCI based synchronous motor SM drive. The search of optimised component values of passive filter combination is carried out by a modified particle swarm optimisation PSO algorithm with an objective of reduction in total harmonic distortion THD and improvement in power factor PF of AC mains current. The proposed PSO algorithm is formulated and implemented in the MATLAB-SIMULINK environment for three varieties of loads on LCI-SM drive, namely constant torque variable speed loads, constant speed variable torque load and variable speed variable torque load to meet the requirements in wide range of applications. The obtained results show considerable improvement in the power quality at the input AC mains of the LCI-SM drives for all varieties of loads and presents a basis for selection of a suitable passive filter combination.

Hand Gesture recognition and classification by Discriminant and Principal Component Analysis using Machine Learning techniques

This paper deals with the recognition of different hand gestures through machine learning approaches and principal component analysis. A Bio-Medical signal amplifier is built after doing a software simulation with the help of NI Multisim. At first a couple of surface electrodes are used to obtain the Electro-Myo-Gram (EMG) signals from the hands. These signals from the surface electrodes have to be amplified with the help of the Bio-Medical Signal amplifier. The Bio-Medical Signal amplifier used is basically an Instrumentation amplifier made with the help of IC AD 620.The output from the Instrumentation amplifier is then filtered with the help of a suitable Band-Pass Filter. The output from the Band Pass filter is then fed to an Analog to Digital Converter (ADC) which in this case is the NI USB 6008.The data from the ADC is then fed into a suitable algorithm which helps in recognition of the different hand gestures. The algorithm analysis is done in MATLAB. The results shown in this paper show a close to One-hundred per cent (100%) classification result for three given hand gestures.

AUTOMATIC SETTING OF REMINDERS IN TELEPHONY USING SPEECH RECOGNITION

Systems and methods for automatically setting reminders. A method for automatically setting reminders includes receiving utterances, determining whether the utterances match a stored phrase, and in response to determining that there is a match, automatically setting a reminder in a mobile communication device. Various filters can be applied to determine whether or not to set a reminder. Examples of suitable filters include location, date/time, callee's phone number, etc.

Application of genetic algorithm for the improved performance of boost converters

DC-DC Boost converters play a major role in DC-DC and DC-AC conversion applications like electric vehicle, integration of photovoltaic (PV) and distributed energy resources into the grid. When these converters operate they might introduce electromagnetic interference (EMI) and harmonics into the system. In order to avoid this, passive filters are prominently used. The methodology proposed here makes use of evolutionary computing algorithm in order to generate an optimized filter design for a boost converter. The proposed generic filter design procedure involves three steps, first selecting a suitable filter, second identifying the transfer functions involved, and finally using evolutionary algorithms to optimize the selected filter design. This methodology was implemented for LC filter design for a DC-DC boost converter using genetic algorithm.

Willow vegetation filters for wastewater treatment and soil remediation combined with biomass production

Vegetation filters of fast-growing trees such as willows and poplars are becoming important as an alternative to conventional treatment of wastewater and landfill leachate. Short-rotation willow coppice is a non-edible crop and has many of the requirements for a suitable vegetation filter. The filtering capacity (e.g., of nitrogen) is very high, and the crop promotes denitrification in the root zone. It has a highly selective uptake of heavy metals, especially cadmium, which enables remediation of contaminated soils. In addition, willows have a high evapotranspiration rate facilitating high loads, e.g., of polluted landfill leachate. Because of the pathogens present in municipal wastewater and sludge, special attention must be paid to storage and distribution of wastewater. In many cases vegetation fdters are more cost-effective than conventional treatment methods and also facilitate recycling of valuable resources in society.

Four Active Filter Topologies to Compensate Different Kinds of Distortion Sources

Along the last years, the practical use of active filters to mitigate harmonics has been extended in electric power systems. Different configurations of series active filters versus shunt active filters have been proposed, among them, hybrid topologies which combine active and passive filters. Nevertheless, there is not any clear accordance about the most suitable configuration for each type of harmonic sources. In this paper, four different topologies of active power filters to eliminate harmonics have been analyzed. It has been implemented an experimental prototype corresponding to each configurations more used and they have been submitted to different performance tests. With this objective, a test bank has been developed, which includes voltage-source nonlinear loads, current-source nonlinear loads, and other whose behavior is between both. The analysis of experimental results obtained allows the most suitable active filter power topology to be determined for each type of load.

Optimal spherical spline filters for the analysis and comparison of regional-scale tomographic models

Advances in seismic tomography lead to increasingly detailed models of the Earth that are often represented on irregular and resolution-adaptive grids. To take full advantage of such models, their assessment must progress beyond a purely visual analysis, and tools must become available for their quantitative comparison. We present a method for the spectral analysis and comparison of multi-scale tomographic models. The method is applicable to irregular grids on the sphere, and is more efficient that filters based on spherical-harmonic expansions or convolution integrals. The combination of a spherical spline representation of tomographic information with Abel-Poisson scaling enables the construction of targetted spatial filters by solving a nonlinear inverse problem for appropriate weighting coefficients. This can be readily achieved with a simulated annealing approach for the limited number of weights. Once suitable filters have been generated they can be employed to address issues such as the patterns of small-scale heterogeneity, transitional structures and comparison of independent models from a region. We illustrate our method in a series of applications where we use different bandpass filters to detect differences in the distribution of small-scale heterogeneity beneath central and eastern Europe, and to compare several recent tomographic models of the Australian region.