Ideal Filter Research Articles

A combined Moving Horizon and Direct Virtual Sensor approach for constrained nonlinear estimation

This paper presents a novel approach to design estimators for nonlinear systems. The approach is based on a combination of linear Moving Horizon Estimation (MHE) and Direct Virtual Sensor (DVS) techniques, and allows the design of estimators with guaranteed stability, which can account for convex constraints on the variables to be estimated. It is also shown that the designed estimators are optimal, in the sense that they give minimal worst-case estimation error, on the basis of the available finite number of noise-corrupted data, with respect to an ideal MHE filter (obtained by assuming exact knowledge of the system dynamics and of the global solution of the related nonlinear program). The approach is tested on a nonlinear mass–spring–damper system.

The potential of onset enhancement for increased speech intelligibility in auditory prostheses

Recent studies have shown that transient parts of a speech signal contribute most to speech intelligibility in normal-hearing listeners. In this study, the influence of enhancing the onsets of the envelope of the speech signal on speech intelligibility in noisy conditions using an eight channel cochlear implant vocoder simulation was investigated. The enhanced envelope (EE) strategy emphasizes the onsets of the speech envelope by deriving an additional peak signal at the onsets in each frequency band. A sentence recognition task in stationary speech shaped noise showed a significant speech reception threshold (SRT) improvement of 2.5 dB for the EE in comparison to the reference continuous interleaved sampling strategy and of 1.7 dB when an ideal Wiener filter was used for the onset extraction on the noisy signal. In a competitive talker condition, a significant SRT improvement of 2.6 dB was measured. A benefit was obtained in all experiments with the peak signal derived from the clean speech. Although the EE strategy is not effective in many real-life situations, the results suggest that there is potential for speech intelligibility improvement when an enhancement of the onsets of the speech envelope is included in the signal processing of auditory prostheses.

The construction of generalized B-spline low-pass filters related to possibility density

Starting from piecewise constant functions, a novel family of generalized symmetric B-splines, with realizable ideal low-pass filters, are constructed. The first order generalized B-spline low-pass filter is closely related to functions analytic in a neighborhood of the unit disc and the generalized sinc functions. The properties of this kind of low-pass filters are investigated. The behavior of the generalized B-spline low-pass filter related to normalized Gaussian distribution is considered.

Is Education a Signal on the Russian Labour Market?

This research focuses on estimating the signalling role of education on the Russian labour market. Two well-known screening hypotheses are initially considered. According to first of these, education is an ideal filter of persons with low productivity: education does not increase the productivity of a person, but it does give him the possibility to signal about his innate productivity via an educational certicate. The second of these hypotheses admits that productivity actually does increase during the period of study, but nevertheless the main objective of getting an education is to acquire a signal about one's productivity. Information theory suggests that employees use education signals during the hiring processes whereby employers screen potential employees. Employers and other categories of self-employed workers are usually not screened by the labour market via their educational attainments. Comparison of the returns to education of employees vs. self-employed workers could show the difference between the returns to signals and the returns to human capital. Yet another way to understand the signals is to consider the time dynamics of the returns to education for employees staying in the same firm. This helps us to answer the question about whether the signals are valuable only during the hiring process, or whether they remain valuable during the whole experience with the firm. This research is based on the Mincerian-type earnings functions, estimated on RLMS-HSE and NOBUS data. On the basis of the available information, we cannot say that the returns to signals and human capital differ significantly in Russia. Nevertheless we can say that, for the majority of men, the return to educational signals decreases with time spent in the same firm, while we observe the opposite for women.

Characterizing rings in terms of the extent of the injectivity and projectivity of their modules

Given a ring R, we define its right i-profile (resp. right p-profile) to be the collection of injectivity domains (resp. projectivity domains) of its right R-modules. We study the lattice theoretic properties of these profiles and consider ways in which properties of the profiles may determine the structure of rings and vice versa. We show that the i-profile is isomorphic to an interval of the lattice of linear filters of right ideals of R, and is therefore modular and coatomic. In particular, we give a practical characterization of the profile of a right artinian ring and offer an example of a ring without injective left middle class for with the same is not true on the right-hand side. We characterize the p-profile of a right perfect ring and show through an example that the right p-profile of a ring is not necessarily a set. In addition, we use our results to provide a characterization of a special class of QF-rings in which the injectivity and projectivity domains of all modules coincide. The study of rings in terms of their (i- or p-)profile was inspired by the study of rings with no right (i- or p-)middle class, initiated in recent papers by Er, López-Permouth and Sökmez, and by Holston, López-Permouth and Orhan-Ertaş.

On predictors for band-limited and high-frequency time series

Pathwise predictability and predictors for discrete time processes are studied in deterministic setting. It is suggested to approximate convolution sums over future times by convolution sums over past time. It is shown that all band-limited processes are predictable in this sense, as well as high-frequency processes with zero energy at low frequencies. In addition, a process of mixed type still can be predicted if an ideal low-pass filter exists for this process.

2D space–time wave-digital multi-fan filter banks for signals consisting of multiple plane waves

Two dimensional space---time fan filters may be used for the highly-selective enhancement of spatio-temporal plane-waves on the basis of their directions of arrival. Unlike uniform bandwidth beam filters, ideal fan filters transmit passband signals over a range of directions of arrival that is independent of their 1D temporal spectrum. In this work, closed-form 2D wave-digital filter design equations and corresponding hardware architectures are proposed for realizing M independent fan-shaped passbands having independently steerable directionality and selectivity. A design method based on LCR ladder networks is proposed and implemented using a 2D time-multiplexed raster-scanned architecture that is suitable for low frequency applications such as audio, multimedia, seismic and ultrasonic beamforming. The architectures are designed, simulated, physically realized and tested on FPGA-based prototypes. Examples of 2D IIR M-fan filterbanks with FPGA implementations, together with measured results from on-chip hardware verifications, show the successful design and hardware realization. The filterbanks and hardware architectures are shown to be suitable for real-time sensor-array beamforming applications using custom VLSI circuits.

Roughness in Orthomodular Lattices

In this paper, we define the rough approximation operators in an algebra using its congruence relations and study some of their properties. Further, we consider the rough approximation operators in orthomodular lattices. We introduce the notion of rough ideal (filter) with respect to a p-ideal in an orthomodular lattice. We show that the upper approximation of an ideal J with respect to a pideal I of an orthomodular lattice is the smallest ideal containing I and J. Further we study the homomorphic images of the rough approximation operators.

Specific features of the hydrodynamic filter of the liquid of type «the cylinder in the cone»

The specific design and technological features of hydrodynamic filter of type "cylinder in a cone" in comparison with other fluid hydrodynamic not ideal filters from solid contaminants are expressed

Approximating Ideal Filters by Systems of Fractional Order

The contributions in this paper are in two folds. On the one hand, we propose a general approach for approximating ideal filters based on fractional calculus from the point of view of systems of fractional order. On the other hand, we suggest that the Paley and Wiener criterion might not be a necessary condition for designing physically realizable ideal filters. As an application of the present approach, we show a case in designing ideal filters for suppressing 50-Hz interference in electrocardiogram (ECG) signals.

CREATING DIGITAL SIGNAL PROCESSING (DSP) FILTERS TO IMPROVE LOUDSPEAKER TRANSIENT RESPONSE

A method is provided for creating a series of digital signal processing (DSP) filters to improve the transient response of a loudspeaker, wherein the loudspeaker is formed of multiple components. The method includes generally six steps. The first step involves identifying a substantially linear, time-invariant, and spatially-consistent loudspeaker mechanism causing transient response distortion. The second step involves characterizing the identified mechanism. The third step involves determining the characterized mechanism's two-port response. The fourth step involves establishing a target response for the characterized mechanism. The fifth step involves calculating an ideal filter to achieve the target response. The sixth step involves designing a cost-reduced filter based on the ideal filter.

리플저감을 위한 Chebyshev 필터 조합에 관한 연구

This paper is focusing on the comparison of different kinds of BPFs(Band Pass Filters) passing signals with a particular frequency band. According to the different classifications, features and target application systems, BPF has many types. Chebyshev filter which has a steep slope and a few ripples, and Butterworth filter which has no ripple but gentle slope are the most typical BPFs. The ideal filter is flat in the passband and the slope in the transition band is perpendicular. In this paper, we suggest the cascading Chebyshev BPF with the advantages of the Chebyshev filter and the Butterworth filter simultaneously to make a closest filter to an ideal filter. The proposing BPF is the tenth Chebyshev BPF cascading the fourth and the sixth, and it is designed as the tenth cascading Chebyshev BPF. To measure the performance of the designing filter, we have compared and analyzed the tenth Chebyshev filter with the tenth Butterworth filter. As a result, the tenth cascading Chebyshev BPF has decreased the ripple more than 1/4 [dB] in the passband. Finally, the output of the simulation showed the validity of the proposing cascading Chebyshev filter.

基于背景先验点的虚焦抠图方法

本文针对图像抠图问题中背景虚焦时的情况，将一些模糊的背景预划分成先验点，使之成为绝对背景，进而避免了与前景颜色相近背景的干扰，使得抠图结果更为理想。首先，采用边缘检测器进行边缘检测，进而对每个边缘点进行分析，根据其对二阶算子的响应值与理想响应值之间的拟合误差，以及它与已知前景之间的颜色差异，判断其是否为被模糊的背景边缘点；然后再计算它沿梯度正负方向两侧的像素与理想化边缘之间的拟合误差，根据阈值可以将两侧的若干点扩展成背景先验点集，即将它们划分为绝对背景点。最后利用与trimap扩展相结合的抠图方式，得到最终的透明度图像。实验结果表明，本文提出的背景先验点与抠图算法，可以得到相对于以往的抠图算法更好的结果。 In this paper, we present a matting method based on focused foreground and blurred background. We classify some pixels as priors to prevent the similarities between foreground and background colors. Firstly, we design a three-channel edge detector to roughly predict some edge pixels. Secondly, for each edge pixel, we estimate its blur degree by fitting an ideal second derivative filter response on the actual one along the gradient direction, and comparing its color and known foreground one. Thirdly, if this pixel is classified into a blurred background edge, we extend it along the gradient direction as blur priors according to the fitting errors to an ideal blurred edge. Finally, with the back-ground blur priors, we run a general matting algorithm along with a trimap expansion method. The experimental results show that our background blur priors could generate much more precise alpha results than the state-of-art algorithms.

Biogenic Silica Nanopore Membranes on Micromachined Silicon Substrates

Nanopore membranes are extremely valuable for applications such as molecular filtration, nanoparticle counting, and sizing studies. However, the fabrication of nanopore membranes using top-down silicon microfabrication technology requires using slow serial patterning processes, making it unsuitable for large-scale manufacturing. Marine diatoms on the other hand feature biomineralized silica shells with the smallest pore diameters on the order of 40 nm. Their hierarchical pore architecture makes these nanomembranes exceptionally mechanically stable, while maintaining a short pore length and a high porosity.In our study, we immobilized the biogenic silica nanomembranes on micromachined silicon substrates. These substrates feature micron-sized, through-wafer channels, enabling free fluidic access to the nanopore membrane. The diatom shells were mounted on top of the silicon microstructure using either poly-L-lysine or UV-polymerizable low-stress epoxy. The resulting microsystem allowed easy handling and mounting in a fluidic platform for nanoparticle transport studies.Using fluorescent nanoparticles we were able to verify that particles with a diameter larger than that of the nanopores were completely retained, while smaller particles, such as polystyrene beads or gold nanoparticles did permeate through the membrane. No evidence for leakage around the diatom was observed, indicating a successful seal around the perimeter of the membrane. When the particles passed through the membrane, the temporary blockage resulted in a reduction in ionic current corresponding to the ratio between the bead and pore size. The characteristic electrophoretic mobility of the beads allowed a characterization of nanoparticles of different origin. The large number of nanopores available for particle translocation (>200) makes them ideal size-selective filters with a low probability of clogging. The combination of biomineralized and microfabricated structures shows a pathway for integrating low-cost nanostructures with BioMEMS devices.

Biomedical Signal Processing and Modeling Complexity of Living Systems

Biomedical Signal Processing and Modeling Complexity of Living Systems

Comparative Study on the Mn<sup>2+</sup> Removing Performance of Several Filters

The Mn2+ removing effect from groundwater by four kinds of filters——Zeolites ,Activated Carbon ,Manganese Sand and a new filter ANJ.SiC, were comparatively studied and analyzed respectively .The results show that, the Mn2+ removing effect of ANJ.SiC is significantly better than the other three .It is an ideal filter in Mn2+ removing ,which can be reused for a long time .These filters’ surface characteristics before and after saturation were compared through their SEM figures ,and the Mn2+ removing mechanism were further studied.

On an asymptotic analysis of polynomial approximation to halfband filters

In this paper we provide information about the asymptotic properties of polynomial filters which approximate the ideal filter. In particular, we study this problem in the special case of polynomial halfband filters. Specifically we estimate the error between a polynomial filter and an ideal filter and show that the error decays exponentially fast. For the special case of polynomial halfband filters, our n-th root asymptotic error estimates are sharp.

Fidelity Performance of Three Filters for High Quality NDVI Time-series Analysis

Some noises still exist in standard MODIS NDVI product and need to be screened before further applications.An ideal filter should only remove noisy data,and keep the good data as much as possible.Most previous studies only concerned about the filter's performance in terms of handling noisy data,and neglected filter's capacity to retain the original high-quality data(fidelity).The present study analyzed three filters included in Timesat 2.3 tools,examined the effect of data quality on the performance of three filter algorithms,both qualitatively and quantitatively.Through comparative analysis,we concluded that Asymmetric Gaussians has the highest fidelity performance of all,followed by Double Logistic algorithm,and Savizky-Glolay algorithm performance worst.

Efficient Fusion of ASTER and SRTM Based on Fast Fourier Transform

In order to overcome the deficiency of sampling methods for SRTM and ASTER,the authors constructed a flow chart for SRTM and ASTER efficient fusion,with the DEMs of Dongzhi tableland as an example.Firstly,ASTER and SRTM were respectively transformed from spatial domain to frequency domain in terms of Fast Fourier Transform(FFT).Secondly,the ideal high and low pass filters were respectively employed to remove their low and high frequency errors.Thirdly,the filtered frequency domains were added up.At last,the summed frequency domain was transformed to spatial domain in terms of inverse FFT.The results indicate that,compared with errors of ASTER and SRTM,both the minimum and maximum errors of the fused DEM show an obvious decrease,the RMSE has a weak decrease and the number of the errors bigger than 30 m is much less than that of SRTM and ASTER.

The Development and Property Studies of Nonwoven Filtering Materials for Car Air-Conditioner

With the development of automotive industry, automotive air-conditioning filter became the essential equipment in people’s daily life. On today’s market, there is half of the filtration equipment made from non-woven materials because of its small resistance, good filtration efficiency, high yield and low cost advantages. In this paper, based on the comparison and analyses of the web structure, fiber distribution and finesse, permeability, thickness and filtration efficiency of the newly developed nonwoven composites and other imported materials, the results were got that the finer fibers, more porosity, thinner thickness and smaller holes together would make an ideal filtering product for using in the cleaner car.