Flannery, D.; Keller, P.; Cartwright, S.; Loomis, J.
1987-06-01
Attractive correlation system performance potential is possible using magneto-optic spatial light modulators (SLM) to implement binary phase-only reference filters at high rates, provided the correlation performance of such reduced-information-content filters is adequate for the application. In the case studied here, the desired filter impulse response is a rectangular shape, which cannot be achieved with the usual binary phase-only filter formulation. The correlation application problem is described and techniques for synthesizing improved filter impulse response are considered. A compromise solution involves the cascading of a fixed amplitude-only weighting mask with the binary phase-only SLM. Based on simulations presented, this approach provides improved impulse responses and good correlation performance, while retaining the critical feature of real-time variations of the size, shape, and orientation of the rectangle by electronic programming of the phase pattern in the SLM. Simulations indicate that, for at least one very challenging input scene clutter situation, these filters provide higher correlation signal-to-noise than does "ideal" correlation, i.e. using a perfect rectangle filter response.
Ultrafast all-optical clock recovery based on phase-only linear optical filtering
DEFF Research Database (Denmark)
Maram, Reza; Kong, Deming; Galili, Michael
2014-01-01
We report on a novel technique for all-optical clock recovery from RZ OOK data based on phase-only filtering, significantly enhancing the recovered clock quality and energy-efficiency compared to the use of a Fabry-Perot filter....
Computing the Minimum-Phase Filter using the QL-Factorization
DEFF Research Database (Denmark)
Hansen, Morten; Christensen, Lars P.B.; Winther, Ole
2010-01-01
We investigate the QL-factorization of a time-invariant convolutive filtering matrix and show that this factorization not only provides the finite length equivalent to the minimum-phase filter, but also gives the associated all-pass filter. The convergence properties are analyzed and we derive...
Group Lifting Structures For Multirate Filter Banks, II: Linear Phase Filter Banks
Energy Technology Data Exchange (ETDEWEB)
Brislawn, Christopher M [Los Alamos National Laboratory
2008-01-01
The theory of group lifting structures is applied to linear phase lifting factorizations for the two nontrivial classes of two-channel linear phase perfect reconstruction filter banks, the whole-and half-sample symmetric classes. Group lifting structures defined for the reversible and irreversible classes of whole-and half-sample symmetric filter banks are shown to satisfy the hypotheses of the uniqueness theorem for group lifting structures. It follows that linear phase lifting factorizations of whole-and half-sample symmetric filter banks are therefore independent of the factorization methods used to compute them. These results cover the specification of user-defined whole-sample symmetric filter banks in Part 2 of the ISO JPEG 2000 standard.
Investigation on filter method for smoothing spiral phase plate
Zhang, Yuanhang; Wen, Shenglin; Luo, Zijian; Tang, Caixue; Yan, Hao; Yang, Chunlin; Liu, Mincai; Zhang, Qinghua; Wang, Jian
2018-03-01
Spiral phase plate (SPP) for generating vortex hollow beams has high efficiency in various applications. However, it is difficult to obtain an ideal spiral phase plate because of its continuous-varying helical phase and discontinued phase step. This paper describes the demonstration of continuous spiral phase plate using filter methods. The numerical simulations indicate that different filter method including spatial domain filter, frequency domain filter has unique impact on surface topography of SPP and optical vortex characteristics. The experimental results reveal that the spatial Gaussian filter method for smoothing SPP is suitable for Computer Controlled Optical Surfacing (CCOS) technique and obtains good optical properties.
Mukhopadhyay, Somparna; Hazra, Lakshminarayan
2015-11-01
Resolution capability of an optical imaging system can be enhanced by reducing the width of the central lobe of the point spread function. Attempts to achieve the same by pupil plane filtering give rise to a concomitant increase in sidelobe intensity. The mutual exclusivity between these two objectives may be considered as a multiobjective optimization problem that does not have a unique solution; rather, a class of trade-off solutions called Pareto optimal solutions may be generated. Pareto fronts in the synthesis of lossless phase-only pupil plane filters to achieve superresolution with prespecified lower limits for the Strehl ratio are explored by using the particle swarm optimization technique.
Load compensation for single phase system using series active filter
African Journals Online (AJOL)
user
Keywords: Active power filter (APF), current source type of harmonic load ... Single phase active filters could attract less attention than three phase due to its low ..... Generalised single-phase p-q theory for active power filtering: simulation and.
Random set particle filter for bearings-only multitarget tracking
Vihola, Matti
2005-05-01
The random set approach to multitarget tracking is a theoretically sound framework that covers joint estimation of the number of targets and the state of the targets. This paper describes a particle filter implementation of the random set multitarget filter. The contribution of this paper to the random set tracking framework is the formulation of a measurement model where each sensor report is assumed to contain at most one measurement. The implemented filter was tested in synthetic bearings-only tracking scenarios containing up to two targets in the presence of false alarms and missed measurements. The estimated target state consisted of 2D position and velocity components. The filter was capable to track the targets fairly well despite of the missing measurements and the relatively high false alarm rates. In addition, the filter showed robustness against wrong parameter values of false alarm rates. The results that were obtained during the limited tests of the filter show that the random set framework has potential for challenging tracking situations. On the other hand, the computational burden of the described implementation is quite high and increases approximately linearly with respect to the expected number of targets.
Bearings-Only Tracking of Manoeuvring Targets Using Particle Filters
Directory of Open Access Journals (Sweden)
M. Sanjeev Arulampalam
2004-11-01
Full Text Available We investigate the problem of bearings-only tracking of manoeuvring targets using particle filters (PFs. Three different (PFs are proposed for this problem which is formulated as a multiple model tracking problem in a jump Markov system (JMS framework. The proposed filters are (i multiple model PF (MMPF, (ii auxiliary MMPF (AUX-MMPF, and (iii jump Markov system PF (JMS-PF. The performance of these filters is compared with that of standard interacting multiple model (IMM-based trackers such as IMM-EKF and IMM-UKF for three separate cases: (i single-sensor case, (ii multisensor case, and (iii tracking with hard constraints. A conservative CRLB applicable for this problem is also derived and compared with the RMS error performance of the filters. The results confirm the superiority of the PFs for this difficult nonlinear tracking problem.
Advanced Filtering Techniques Applied to Spaceflight, Phase II
National Aeronautics and Space Administration — IST-Rolla developed two nonlinear filters for spacecraft orbit determination during the Phase I contract. The theta-D filter and the cost based filter, CBF, were...
Three phase active power filter with selective harmonics elimination
Directory of Open Access Journals (Sweden)
Sozański Krzysztof
2016-03-01
Full Text Available This paper describes a three phase shunt active power filter with selective harmonics elimination. The control algorithm is based on a digital filter bank. The moving Discrete Fourier Transformation is used as an analysis filter bank. The correctness of the algorithm has been verified by simulation and experimental research. The paper includes exemplary results of current waveforms and their spectra from a three phase active power filter.
Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming.
Bañas, Andrew; Palima, Darwin; Glückstad, Jesper
2012-04-23
We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser illumination. The devices are subsequently placed into the object and Fourier plane of a standard 4f-setup according to the mGPC spatial filtering configuration. Having a reconfigurable spatial phase filter, instead of a fixed and fabricated one, allows the beam shaper to adapt to different input phase patterns suited for different requirements. Despite imperfections in these consumer pico-projectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection. © 2012 Optical Society of America
Data assimilation in the early phase: Kalman filtering RIMPUFF
International Nuclear Information System (INIS)
Astrup, P.; Turcanu, C.; Puch, R.O.; Palma, C.R.; Mikkelsen, T.
2004-09-01
In the framework of the DAONEM project (Data Assimilation for Off-site Nuclear Emergency Management), a data assimilation module, ADUM (Atmospheric Dispersion Updating Module), for the mesoscale atmospheric dispersion program RIMPUFF (Risoe Mesoscale Puff model) part of the early-phase programs of RODOS (Realtime Online DecisiOn Support system for nuclear emergencies) has been developed. It is built on the Kalman filtering algorithm and it assimilates 10-minute averaged gamma dose rates measured at ground level stations. Since the gamma rates are non-linear functions of the state vector variables, the applied Kalman filter is the so-called Extended Kalman filter. In more ways the implementation is non standard: 1) the number of state vector variables varies with time, and 2) the state vector variables are prediction updated with 1-minute time steps but only Kalman filtered every 10 minutes, and this based on time averaged measurements. Given reasonable conditions, i.e. a spatially dense distribution of gamma monitors and a realistic wind field, the developed ADUM module is found to be able to enhance the prediction of the gamma dose field. Based on some of the Kalman filtering parameters, another module, ToDeMM, has been developed for providing the late-phase DeMM (Deposition Monitoring Module) of RODOS with an ensemble of fields of ground level air concentrations and wet deposited material. This accounts for the uncertainty estimation of this kind of quantities as calculated by RIMPUFF for use by DeMM. (au)
DEFF Research Database (Denmark)
Rodriguez, Pedro; Candela, J. I.; Luna, A.
2009-01-01
This paper presents a new solution for filtering current harmonics in three-phase four-wire networks. The original four-branch star (FBS) filter topology presented in this paper is characterized by a particular layout of single-phase inductances and capacitors, without using any transformer......, a specific implementation of a three-phase four-wire hybrid power filter is presented as an illustrative application of the filtering topology. An extensive evaluation using simulation and experimental results from a DSP-based laboratory prototype is conducted in order to verify and validate the good...... only passive components are employed, or as a hybrid filter, when its behavior is improved by integrating a power converter into the filter structure. The paper analyzes the proposed topology, and derives fundamental concepts about the control of the resulting hybrid power filter. From this analysis...
Iterated unscented Kalman filter for phase unwrapping of interferometric fringes.
Xie, Xianming
2016-08-22
A fresh phase unwrapping algorithm based on iterated unscented Kalman filter is proposed to estimate unambiguous unwrapped phase of interferometric fringes. This method is the result of combining an iterated unscented Kalman filter with a robust phase gradient estimator based on amended matrix pencil model, and an efficient quality-guided strategy based on heap sort. The iterated unscented Kalman filter that is one of the most robust methods under the Bayesian theorem frame in non-linear signal processing so far, is applied to perform simultaneously noise suppression and phase unwrapping of interferometric fringes for the first time, which can simplify the complexity and the difficulty of pre-filtering procedure followed by phase unwrapping procedure, and even can remove the pre-filtering procedure. The robust phase gradient estimator is used to efficiently and accurately obtain phase gradient information from interferometric fringes, which is needed for the iterated unscented Kalman filtering phase unwrapping model. The efficient quality-guided strategy is able to ensure that the proposed method fast unwraps wrapped pixels along the path from the high-quality area to the low-quality area of wrapped phase images, which can greatly improve the efficiency of phase unwrapping. Results obtained from synthetic data and real data show that the proposed method can obtain better solutions with an acceptable time consumption, with respect to some of the most used algorithms.
Deep Ultraviolet Macroporous Silicon Filters, Phase I
National Aeronautics and Space Administration — This SBIR Phase I proposal describes a novel method to make deep and far UV optical filters from macroporous silicon. This type of filter consists of an array of...
A phase-equalized digital multirate filter for 50 Hz signal processing
Energy Technology Data Exchange (ETDEWEB)
Vainio, O. [Tampere University of Technology, Signal Processing Laboratory, Tampere (Finland)
1997-12-31
A new multistage digital filter is proposed for 50 Hz line frequency signal processing in zero-crossing detectors and synchronous power systems. The purpose of the filter is to extract the fundamental sinusoidal signal from noise and impulsive disturbances so that the output is accurately in phase with the primary input signal. This is accomplished with a cascade of a median filter, a linear-phase FIR filter, and a phase corrector. A 10 kHz output timing resolution is achieved by up-sampling with a customized interpolation filter. (orig.) 15 refs.
Mercury Oxidation via Catalytic Barrier Filters Phase II
Energy Technology Data Exchange (ETDEWEB)
Wayne Seames; Michael Mann; Darrin Muggli; Jason Hrdlicka; Carol Horabik
2007-09-30
In 2004, the Department of Energy National Energy Technology Laboratory awarded the University of North Dakota a Phase II University Coal Research grant to explore the feasibility of using barrier filters coated with a catalyst to oxidize elemental mercury in coal combustion flue gas streams. Oxidized mercury is substantially easier to remove than elemental mercury. If successful, this technique has the potential to substantially reduce mercury control costs for those installations that already utilize baghouse barrier filters for particulate removal. Completed in 2004, Phase I of this project successfully met its objectives of screening and assessing the possible feasibility of using catalyst coated barrier filters for the oxidation of vapor phase elemental mercury in coal combustion generated flue gas streams. Completed in September 2007, Phase II of this project successfully met its three objectives. First, an effective coating method for a catalytic barrier filter was found. Second, the effects of a simulated flue gas on the catalysts in a bench-scale reactor were determined. Finally, the performance of the best catalyst was assessed using real flue gas generated by a 19 kW research combustor firing each of three separate coal types.
Trusiak, Maciej; Patorski, Krzysztof
2015-02-23
Gram-Schmidt orthonormalization is a very fast and efficient method for the fringe pattern phase demodulation. It requires only two arbitrarily phase-shifted frames. Images are treated as vectors and upon orthogonal projection of one fringe vector onto another the quadrature fringe pattern pair is obtained. Orthonormalization process is very susceptible, however, to noise, uneven background and amplitude modulation fluctuations. The Hilbert-Huang transform based preprocessing is proposed to enhance fringe pattern phase demodulation by filtering out the spurious noise and background illumination and performing fringe normalization. The Gram-Schmidt orthonormalization process error analysis is provided and its filtering-expanded capabilities are corroborated analyzing DSPI fringes and performing amplitude demodulation of Bessel fringes. Synthetic and experimental fringe pattern analyses presented to validate the proposed technique show that it compares favorably with other pre-filtering schemes, i.e., Gaussian filtering and continuous wavelet transform.
Four-branch Star Hybrid Power Filter for Three-phase Four-wire Systems
DEFF Research Database (Denmark)
Blaabjerg, Frede; Teodorescu, Remus; Rodriguez, Pedro
2008-01-01
and derives fundamental concepts about the control of the resulting hybrid power filter. From this analysis, a specifc implementation of a three-phase four-wire hybrid power filter is presented as an illustrative application of the filtering topology. An extensive evaluation using simulation and experimental......This paper presents a new concept for filtering current harmonics in three-phase four-wire networks. The four-branch star (FBS) filtering topology presented in this work is characterized by a particular layout consisting of single-phase inductances and capacitors. Via this layout, a power filter...
Phase unwrapping algorithm using polynomial phase approximation and linear Kalman filter.
Kulkarni, Rishikesh; Rastogi, Pramod
2018-02-01
A noise-robust phase unwrapping algorithm is proposed based on state space analysis and polynomial phase approximation using wrapped phase measurement. The true phase is approximated as a two-dimensional first order polynomial function within a small sized window around each pixel. The estimates of polynomial coefficients provide the measurement of phase and local fringe frequencies. A state space representation of spatial phase evolution and the wrapped phase measurement is considered with the state vector consisting of polynomial coefficients as its elements. Instead of using the traditional nonlinear Kalman filter for the purpose of state estimation, we propose to use the linear Kalman filter operating directly with the wrapped phase measurement. The adaptive window width is selected at each pixel based on the local fringe density to strike a balance between the computation time and the noise robustness. In order to retrieve the unwrapped phase, either a line-scanning approach or a quality guided strategy of pixel selection is used depending on the underlying continuous or discontinuous phase distribution, respectively. Simulation and experimental results are provided to demonstrate the applicability of the proposed method.
Kalman filters for real-time magnetic island phase tracking
International Nuclear Information System (INIS)
Borgers, D.P.; Lauret, M.; Baar, M.R. de
2013-01-01
Highlights: • We propose two Kalman filters for tracking of NTMs on ASDEX Upgrade. • The Kalman filters can track NTMs in a much larger frequency range than PLLs. • The filters are tested on synthetic and experimental data from TEXTOR and TCV. • We conclude that the unscented Kalman filter can be useful for NTM control. -- Abstract: For control of neoclassical tearing modes (NTMs) and the resulting rotating magnetic islands in tokamak plasmas, the frequency and phase of the magnetic islands need to be accurately tracked in real-time. In previous experiments on TEXTOR, this was achieved using a phase-locked loop (PLL). For ASDEX Upgrade however, the desired frequency range in which the islands are to be tracked (100 Hz–10 kHz) is much larger than is possible with a PLL. In this contribution, an extended Kalman filter (EKF) and an unscented Kalman filter (UKF) are proposed for real-time frequency, phase and amplitude tracking of sinusoidal signals, based on noisy measurements. Compared to PLLs, the EKF and UKF are able to track sinusoidal signals in a much larger frequency range. The filters are applied on synthetic data and on experimental data from the TEXTOR and TCV tokamaks, from which we conclude that the UKF can be useful for real-time control of magnetic islands on ASDEX Upgrade
Kalman filters for real-time magnetic island phase tracking
Energy Technology Data Exchange (ETDEWEB)
Borgers, D.P. [Hybrid and Networked Systems, Department of Mechanical Engineering – Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Lauret, M., E-mail: M.Lauret@tue.nl [FOM Institute DIFFER – Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, Nieuwegein (Netherlands); Control Systems Technology, Department of Mechanical Engineering – Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Baar, M.R. de [FOM Institute DIFFER – Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, Nieuwegein (Netherlands); Control Systems Technology, Department of Mechanical Engineering – Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
2013-11-15
Highlights: • We propose two Kalman filters for tracking of NTMs on ASDEX Upgrade. • The Kalman filters can track NTMs in a much larger frequency range than PLLs. • The filters are tested on synthetic and experimental data from TEXTOR and TCV. • We conclude that the unscented Kalman filter can be useful for NTM control. -- Abstract: For control of neoclassical tearing modes (NTMs) and the resulting rotating magnetic islands in tokamak plasmas, the frequency and phase of the magnetic islands need to be accurately tracked in real-time. In previous experiments on TEXTOR, this was achieved using a phase-locked loop (PLL). For ASDEX Upgrade however, the desired frequency range in which the islands are to be tracked (100 Hz–10 kHz) is much larger than is possible with a PLL. In this contribution, an extended Kalman filter (EKF) and an unscented Kalman filter (UKF) are proposed for real-time frequency, phase and amplitude tracking of sinusoidal signals, based on noisy measurements. Compared to PLLs, the EKF and UKF are able to track sinusoidal signals in a much larger frequency range. The filters are applied on synthetic data and on experimental data from the TEXTOR and TCV tokamaks, from which we conclude that the UKF can be useful for real-time control of magnetic islands on ASDEX Upgrade.
THE PHASE REACTOR INDUCTANCE SELECTION TECHNIQUE FOR POWER ACTIVE FILTER
Directory of Open Access Journals (Sweden)
D. V. Tugay
2016-12-01
Full Text Available Purpose. The goal is to develop technique of the phase inductance power reactors selection for parallel active filter based on the account both low-frequency and high-frequency components of the electromagnetic processes in a power circuit. Methodology. We have applied concepts of the electrical circuits theory, vector analysis, mathematical simulation in Matlab package. Results. We have developed a new technique of the phase reactors inductance selection for parallel power active filter. It allows us to obtain the smallest possible value of THD network current. Originality. We have increased accuracy of methods of the phase reactor inductance selection for power active filter. Practical value. The proposed technique can be used in the design and manufacture of the active power filter for real objects of energy supply.
International Nuclear Information System (INIS)
Fu, Jian; Hu, Xinhua; Li, Chen
2015-01-01
We report an alternative reconstruction technique for x-ray differential phase-contrast computed tomography (DPC-CT). This approach is based on a new phase line integral projection retrieval filter, which is rooted in the derivative property of the Fourier transform and counteracts the differential nature of the DPC-CT projections. It first retrieves the phase line integral from the DPC-CT projections. Then the standard filtered back-projection (FBP) algorithms popular in x-ray absorption-contrast CT are directly applied to the retrieved phase line integrals to reconstruct the DPC-CT images. Compared with the conventional DPC-CT reconstruction algorithms, the proposed method removes the Hilbert imaginary filter and allows for the direct use of absorption-contrast FBP algorithms. Consequently, FBP-oriented image processing techniques and reconstruction acceleration softwares that have already been successfully used in absorption-contrast CT can be directly adopted to improve the DPC-CT image quality and speed up the reconstruction
Arbitrary-step randomly delayed robust filter with application to boost phase tracking
Qin, Wutao; Wang, Xiaogang; Bai, Yuliang; Cui, Naigang
2018-04-01
The conventional filters such as extended Kalman filter, unscented Kalman filter and cubature Kalman filter assume that the measurement is available in real-time and the measurement noise is Gaussian white noise. But in practice, both two assumptions are invalid. To solve this problem, a novel algorithm is proposed by taking the following four steps. At first, the measurement model is modified by the Bernoulli random variables to describe the random delay. Then, the expression of predicted measurement and covariance are reformulated, which could get rid of the restriction that the maximum number of delay must be one or two and the assumption that probabilities of Bernoulli random variables taking the value one are equal. Next, the arbitrary-step randomly delayed high-degree cubature Kalman filter is derived based on the 5th-degree spherical-radial rule and the reformulated expressions. Finally, the arbitrary-step randomly delayed high-degree cubature Kalman filter is modified to the arbitrary-step randomly delayed high-degree cubature Huber-based filter based on the Huber technique, which is essentially an M-estimator. Therefore, the proposed filter is not only robust to the randomly delayed measurements, but robust to the glint noise. The application to the boost phase tracking example demonstrate the superiority of the proposed algorithms.
SAR Interferogram Filtering of Shearlet Domain Based on Interferometric Phase Statistics
Directory of Open Access Journals (Sweden)
Yonghong He
2017-02-01
Full Text Available This paper presents a new filtering approach for Synthetic Aperture Radar (SAR interferometric phase noise reduction in the shearlet domain, depending on the coherent statistical characteristics. Shearlets provide a multidirectional and multiscale decomposition that have advantages over wavelet filtering methods when dealing with noisy phase fringes. Phase noise in SAR interferograms is directly related to the interferometric coherence and the look number of the interferogram. Therefore, an optimal interferogram filter should incorporate information from both of them. The proposed method combines the phase noise standard deviation with the shearlet transform. Experimental results show that the proposed method can reduce the interferogram noise while maintaining the spatial resolution, especially in areas with low coherence.
An optical tunable filter array based on LCOS phase grating
Feng, Dong; Wan, Zhujun; Chen, Xu; Yan, Shijia; Luo, Zhixiang
2018-01-01
This paper reports an optical tunable filter array (TFA) based on a LCOS (liquid crystal on silicon) chip. The input broadband optical beam is first dispersed by a bulk grating and then incident on the LCOS chip. The LCOS chip is phase-only modulated and constructed as a dynamic reflective phase grating. The phase modulation is adjusted to meet the Littrow angle for a specified passband wavelength and thus the optical beam corresponding to this wavelength is steered to the output. The input/output optical beams are coupled to optical fibers with a dual-fiber collimator. Four dualfiber collimators are vertically aligned as the inputs/outputs and the pixels of the LCOS chip are vertically allocated as four independent zones. Thus the device can act as a 4-channel TFA, which is assembled and functionally demonstrated.
Lifted linear phase filter banks and the polyphase-with-advance representation
Energy Technology Data Exchange (ETDEWEB)
Brislawn, C. M. (Christopher M.); Wohlberg, B. E. (Brendt E.)
2004-01-01
A matrix theory is developed for the noncausal polyphase-with-advance representation that underlies the theory of lifted perfect reconstruction filter banks and wavelet transforms as developed by Sweldens and Daubechies. This theory provides the fundamental lifting methodology employed in the ISO/IEC JPEG-2000 still image coding standard, which the authors helped to develop. Lifting structures for polyphase-with-advance filter banks are depicted in Figure 1. In the analysis bank of Figure 1(a), the first lifting step updates x{sub 0} with a filtered version of x{sub 1} and the second step updates x{sub 1} with a filtered version of x{sub 0}; gain factors 1/K and K normalize the lowpass- and highpass-filtered output subbands. Each of these steps is inverted by the corresponding operations in the synthesis bank shown in Figure 1(b). Lifting steps correspond to upper- or lower-triangular matrices, S{sub i}(z), in a cascade-form decomposition of the polyphase analysis matrix, H{sub a}(z). Lifting structures can also be implemented reversibly (i.e., losslessly in fixed-precision arithmetic) by rounding the lifting updates to integer values. Our treatment of the polyphase-with-advance representation develops an extensive matrix algebra framework that goes far beyond the results of. Specifically, we focus on analyzing and implementing linear phase two-channel filter banks via linear phase lifting cascade schemes. Whole-sample symmetric (WS) and half-sample symmetric (HS) linear phase filter banks are characterized completely in terms of the polyphase-with-advance representation. The theory benefits significantly from a number of new group-theoretic structures arising in the polyphase-with-advance matrix algebra from the lifting factorization of linear phase filter banks.
Spin Filtering in Epitaxial Spinel Films with Nanoscale Phase Separation
Li, Peng
2017-05-08
The coexistence of ferromagnetic metallic phase and antiferromagnetic insulating phase in nanoscaled inhomogeneous perovskite oxides accounts for the colossal magnetoresistance. Although the model of spin-polarized electron transport across antiphase boundaries has been commonly employed to account for large magnetoresistance (MR) in ferrites, the magnetic anomalies, the two magnetic phases and enhanced molecular moment, are still unresolved. We observed a sizable MR in epitaxial spinel films (NiCo2O4-δ) that is much larger than that commonly observed in spinel ferrites. Detailed analysis reveals that this MR can be attributed to phase separation, in which the perfect ferrimagnetic metallic phase and ferrimagnetic insulating phase coexist. The magnetic insulating phase plays an important role in spin filtering in these phase separated spinel oxides, leading to a sizable MR effect. A spin filtering model based on Zeeman effect and direct tunneling is developed to account for MR of the phase separated films.
An LLCL Power Filter for Single-Phase Grid-Tied Inverter
DEFF Research Database (Denmark)
Wu, Weimin; He, Yuanbin; Blaabjerg, Frede
2012-01-01
This paper presents a new topology of higher order power filter for grid-tied voltage-source inverters, named the LLCL filter, which inserts a small inductor in the branch loop of the capacitor in the traditional LCL filter to compose a series resonant circuit at the switching frequency. Particul......This paper presents a new topology of higher order power filter for grid-tied voltage-source inverters, named the LLCL filter, which inserts a small inductor in the branch loop of the capacitor in the traditional LCL filter to compose a series resonant circuit at the switching frequency...... to the inverter system control. The parameter design criteria of the proposed LLCL filter is also introduced. The comparative analysis and discussions regarding the traditional LCL filter and the proposed LLCL filter have been presented and evaluated through experiment on a 1.8-kW-single-phase grid-tied inverter...
International Nuclear Information System (INIS)
Lee, Jeong Seong; Chung, Soon Il; Ljaz, Umer Zeeshan; Khambampati, Anil Kumar; Kim, Kyung Youn; Kim, Sin Kim
2007-01-01
For the visualization of the phase boundary in annular two-phase flows, the electrical resistance tomography (ERT) technique is introduced. In ERT, a set of predetermined electrical currents is injected trough the electrodes placed on the boundary of the flow passage and the induced electrical potentials are measured on the electrode. With the relationship between the injected currents and the induced voltages, the electrical conductivity distribution across the flow domain is estimated through the image reconstruction algorithm. In this, the conductivity distribution corresponds to the phase distribution. In the application of ERT to two-phase flows where there are only two conductivity values, the conductivity distribution estimation problem can be transformed into the boundary estimation problem. This paper considers a bubble boundary estimation with ERT in annular two-phase flows. As the image reconstruction algorithm, the unscented Kalman filter (UKF) is adopted since from the control theory it is reported that the UKF shows better performance than the extended Kalman filter (EKF) that has been commonly used. We formulated the UKF algorithm to be incorporate into the image reconstruction algorithm for the present problem. Also, phantom experiments have been conducted to evaluate the improvement by UKF
Directory of Open Access Journals (Sweden)
Menxi Xie
2017-06-01
Full Text Available High performance synchronization methord is citical for grid connected power converter. For single-phase system, power based phase-locked loop(pPLL uses a multiplier as phase detector(PD. As single-phase grid voltage is distorted, the phase error information contains ac disturbances oscillating at integer multiples of fundamental frequency which lead to detection error. This paper presents a new scheme based on moving average filter(MAF applied in-loop of pPLL. The signal characteristic of phase error is dissussed in detail. A predictive rule is adopted to compensate the delay induced by MAF, thus achieving fast dynamic response. In the case of frequency deviate from nomimal, estimated frequency is fed back to adjust the filter window length of MAF and buffer size of predictive rule. Simulation and experimental results show that proposed PLL achieves good performance under adverse grid conditions.
640 Gbit/s RZ-to-NRZ format conversion based on optical phase filtering
DEFF Research Database (Denmark)
Maram, Reza; Kong, Deming; Galili, Michael
2014-01-01
We propose a novel approach for all optical RZ-to-NRZ conversion based on optical phase filtering. The proposed concept is experimentally validated through format conversion of a 640 Gbit/s coherent RZ signal to NRZ signal using a simple phase filter implemented by a commercial optical waveshaper....
Research on signal processing of shock absorber test bench based on zero-phase filter
Wu, Yi; Ding, Guoqing
2017-10-01
The quality of force-displacement diagram is significant to help evaluate the performance of shock absorbers. Damping force sampling data is often interfered by Gauss white noise, 50Hz power interference and its harmonic wave during the process of testing; data de-noising has become the core problem of drawing true, accurate and real-time indicator diagram. The noise and interference can be filtered out through generic IIR or FIR low-pass filter, but addition phase lag of useful signal will be caused due to the inherent attribute of IIR and FIR filter. The paper uses FRR method to realize zero-phase digital filtering in a software way based on mutual cancellation of phase lag between the forward and reverse sequences after through the filter. High-frequency interference above 40Hz are filtered out completely and noise attenuation is more than -40dB, with no additional phase lag. The method is able to restore the true signal as far as possible. Theoretical simulation and practical test indicate high-frequency noises have been effectively inhibited in multiple typical speed cases, signal-to-noise ratio being greatly improved; the curve in indicator diagram has better smoothness and fidelity. The FRR algorithm has low computational complexity, fast running time, and can be easily transplanted in multiple platforms.
Two-dimensional unwrapped phase inversion with damping and a Gaussian filter
Choi, Yun Seok; Alkhalifah, Tariq Ali
2014-01-01
Phase wrapping is one of main causes of the local minima problem in waveform inversion. However, the unwrapping process for 2D phase maps that includes singular points (residues) is complicated and does not guarantee unique solutions. We employ an exponential damping to eliminate the residues in the 2D phase maps, which makes the 2D phase unwrapping process easy and produce a unique solution. A recursive inversion process using the damped unwrapped phase provides an opportunity to invert for smooth background updates first, and higher resolution updates later as we reduce the damping. We also apply a Gaussian filter to the gradient to mitigate the edge artifacts resulting from the narrow shape of the sensitivity kernels at high damping. Numerical examples demonstrate that our unwrapped phase inversion with damping and a Gaussian filter produces good convergent results even for a 3Hz single frequency of Marmousi dataset and with a starting model far from the true model.
National Research Council Canada - National Science Library
Erwin, R. S; Bernstein, Dennis S
2005-01-01
.... In this paper we use a sampled-data extended Kalman Filter to estimate the trajectory or a target satellite when only range measurements are available from a constellation or orbiting spacecraft...
Target Centroid Position Estimation of Phase-Path Volume Kalman Filtering
Directory of Open Access Journals (Sweden)
Fengjun Hu
2016-01-01
Full Text Available For the problem of easily losing track target when obstacles appear in intelligent robot target tracking, this paper proposes a target tracking algorithm integrating reduced dimension optimal Kalman filtering algorithm based on phase-path volume integral with Camshift algorithm. After analyzing the defects of Camshift algorithm, compare the performance with the SIFT algorithm and Mean Shift algorithm, and Kalman filtering algorithm is used for fusion optimization aiming at the defects. Then aiming at the increasing amount of calculation in integrated algorithm, reduce dimension with the phase-path volume integral instead of the Gaussian integral in Kalman algorithm and reduce the number of sampling points in the filtering process without influencing the operational precision of the original algorithm. Finally set the target centroid position from the Camshift algorithm iteration as the observation value of the improved Kalman filtering algorithm to fix predictive value; thus to make optimal estimation of target centroid position and keep the target tracking so that the robot can understand the environmental scene and react in time correctly according to the changes. The experiments show that the improved algorithm proposed in this paper shows good performance in target tracking with obstructions and reduces the computational complexity of the algorithm through the dimension reduction.
DEFF Research Database (Denmark)
Chen, Yaohui; Xue, Weiqi; Öhman, Filip
2008-01-01
We present a model to interpret enhanced microwave phase shifts based on filter assisted slow and fast light effects in semiconductor optical amplifiers. The model also demonstrates the spectral phase impact of input optical signals.......We present a model to interpret enhanced microwave phase shifts based on filter assisted slow and fast light effects in semiconductor optical amplifiers. The model also demonstrates the spectral phase impact of input optical signals....
Burger, Karin; Koehler, Thomas; Chabior, Michael; Allner, Sebastian; Marschner, Mathias; Fehringer, Andreas; Willner, Marian; Pfeiffer, Franz; Noël, Peter
2014-12-29
Phase-contrast x-ray computed tomography has a high potential to become clinically implemented because of its complementarity to conventional absorption-contrast.In this study, we investigate noise-reducing but resolution-preserving analytical reconstruction methods to improve differential phase-contrast imaging. We apply the non-linear Perona-Malik filter on phase-contrast data prior or post filtered backprojected reconstruction. Secondly, the Hilbert kernel is replaced by regularized iterative integration followed by ramp filtered backprojection as used for absorption-contrast imaging. Combining the Perona-Malik filter with this integration algorithm allows to successfully reveal relevant sample features, quantitatively confirmed by significantly increased structural similarity indices and contrast-to-noise ratios. With this concept, phase-contrast imaging can be performed at considerably lower dose.
Park, Young W.; Montez, Moises N.
1994-01-01
A candidate onboard space navigation filter demonstrated excellent performance (less than 8 meter level RMS semi-major axis accuracy) in performing orbit determination of a low-Earth orbit Explorer satellite using single-frequency real GPS data. This performance is significantly better than predicted by other simulation studies using dual-frequency GPS data. The study results revealed the significance of two new modeling approaches evaluated in the work. One approach introduces a single-frequency ionospheric correction through pseudo-range and phase range averaging implementation. The other approach demonstrates a precise axis-dependent characterization of dynamic sample space uncertainty to compute a more accurate Kalman filter gain. Additionally, this navigation filter demonstrates a flexibility to accommodate both perturbational dynamic and observational biases required for multi-flight phase and inhomogeneous application environments. This paper reviews the potential application of these methods and the filter structure to terrestrial vehicle and positioning applications. Both the single-frequency ionospheric correction method and the axis-dependent state noise modeling approach offer valuable contributions in cost and accuracy improvements for terrestrial GPS receivers. With a modular design approach to either 'plug-in' or 'unplug' various force models, this multi-flight phase navigation filter design structure also provides a versatile GPS navigation software engine for both atmospheric and exo-atmospheric navigation or positioning use, thereby streamlining the flight phase or application-dependent software requirements. Thus, a standardized GPS navigation software engine that can reduce the development and maintenance cost of commercial GPS receivers is now possible.
Indirect Control of a low power Single-Phase Active Power Filter
Directory of Open Access Journals (Sweden)
SILVIU EPURE
2010-12-01
Full Text Available This paper deals with a low power, single phase active filter used to compensate nonlinear loads. The filter uses the indirect control method and it is based on a particular connection between filter, polluting load and grid to avoid timeconsuming mathematic operations or signal processing computations and assures good rejection of harmonic currents injected by the nonlinear load into the grid. A scale model was first simulated in Simulink and then physically implemented. The paper presents simulation and experimental results, and highlight problems encountered during experiments.
Design and control of an LCL-filter-based three-phase active rectifier
DEFF Research Database (Denmark)
Liserre, Marco; Blaabjerg, Frede; Hansen, Steffan
2005-01-01
This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized...... by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier...... a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes....
Phase-only optical encryption based on the zeroth-order phase-contrast technique
Pizolato, José Carlos; Neto, Luiz Gonçalves
2009-09-01
A phase-only encryption/decryption scheme with the readout based on the zeroth-order phase-contrast technique (ZOPCT), without the use of a phase-changing plate on the Fourier plane of an optical system based on the 4f optical correlator, is proposed. The encryption of a gray-level image is achieved by multiplying the phase distribution obtained directly from the gray-level image by a random phase distribution. The robustness of the encoding is assured by the nonlinearity intrinsic to the proposed phase-contrast method and the random phase distribution used in the encryption process. The experimental system has been implemented with liquid-crystal spatial modulators to generate phase-encrypted masks and a decrypting key. The advantage of this method is the easy scheme to recover the gray-level information from the decrypted phase-only mask applying the ZOPCT. An analysis of this decryption method was performed against brute force attacks.
International Nuclear Information System (INIS)
Samman, F.A.; Pongyupinpanich Surapong; Spies, C.; Glesner, M.
2012-01-01
A hardware implementation of an adaptive phase and magnitude detector and filter of a beam-phase control system in a heavy ion synchrotron application is presented in this paper. The main components of the hardware are adaptive LMS (Least-Mean-Square) filters and phase and magnitude detectors. The phase detectors are implemented by using a CORDIC (Coordinate Rotation Digital Computer) algorithm based on 32-bit binary floating-point arithmetic data formats. The floating-point-based hardware is designed to improve the precision of the past hardware implementation that were based on fixed-point arithmetics. The hardware of the detector and the adaptive LMS filter have been implemented on a programmable logic device (FPGA) for hardware acceleration purpose. The ideal Matlab/Simulink model of the hardware and the VHDL model of the adaptive LMS filter and the phase and magnitude detector are compared. The comparison result shows that the output signal of the floating-point based adaptive FIR filter as well as the phase and magnitude detector agree with the expected output signal of the ideal Matlab/Simulink model. (authors)
Improving the phase measurement by the apodization filter in the digital holography
Chang, Shifeng; Wang, Dayong; Wang, Yunxin; Zhao, Jie; Rong, Lu
2012-11-01
Due to the finite size of the hologram aperture in digital holography, high frequency intensity and phase fluctuations along the edges of the images, which reduce the precision of phase measurement. In this paper, the apodization filters are applied to improve the phase measurement in the digital holography. Firstly, the experimental setup of the lensless Fourier transform digital holography is built, where the sample is a standard phase grating with the grating constant of 300μm and the depth of 150nm. Then, apodization filters are applied to phase measurement of the sample with three kinds of the window functions: Tukey window, Hanning window and Blackman window, respectively. Finally, the results were compared to the detection data given by the commercial white-light interferometer. It is shown that aperture diffraction effects can be reduced by the digital apodization, and the phase measurement with the apodization is more accurate than in the unapodized case. Meanwhile, the Blackman window function produces better effect than the other two window functions in the measurement of the standard phase grating.
Chandramouli, Bharat; Benskin, Jonathan P; Hamilton, M Coreen; Cosgrove, John R
2015-01-01
Per- and polyfluoroalkyl substances (PFASs), including perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are ubiquitous in the environment. Investigations into their fate and potential phase-partitioning behavior require separating solid from aqueous phases via filtration. However, sorption of aqueous-phase PFASs on filtration media may lead to underestimation of PFAS concentrations in the aqueous phase. The authors investigated the sorption of perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids (PFPiAs), polyfluoroalkyl phosphate monoesters, polyfluoroalkyl phosphate diesters (diPAPs), fluorotelomer sulfonates, and perfluorooctane sulfonamide on filtration media. The effects of concentration (3 spiking levels), filter media (4 types), matrix (4 matrices), and compound structure on sorption are reported. Glass fiber filtration resulted in the least sorption, whereas polytetrafluoroethylene filters resulted in the most sorption (up to 98%). Analyte concentration had no significant effect. Sorption was generally consistent across matrix types except for samples affected by aqueous film forming foam deployment, which displayed high sorption of PFOS on nylon filters. Sorption usually increased with an increasing number of carbon or fluorine atoms and was most pronounced for PFPiAs and diPAPs (30–75% sorption). Overall, glass fiber filters are more recommended than nylon filters in environmental samples when phase separation is required. Use of filtration media for PFAS must be preceded by matrix-specific testing to account for unpredictable effects. (C)2014 SETAC
Jian, Wenjuan; Chen, Minyou; McFarland, Dennis J
2017-11-01
Phase-locking value (PLV) is a potentially useful feature in sensorimotor rhythm-based brain-computer interface (BCI). However, volume conduction may cause spurious zero-phase coupling between two EEG signals and it is not clear whether PLV effects are independent of spectral amplitude. Volume conduction might be reduced by spatial filtering, but it is uncertain what impact this might have on PLV. Therefore, the goal of this study was to explore whether zero-phase PLV is meaningful and how it is affected by spatial filtering. Both amplitude and PLV feature were extracted in the frequency band of 10-15 Hz by classical methods using archival EEG data of 18 subjects trained on a two-target BCI task. The results show that with right ear-referenced data, there is meaningful long-range zero-phase synchronization likely involving the primary motor area and the supplementary motor area that cannot be explained by volume conduction. Another novel finding is that the large Laplacian spatial filter enhances the amplitude feature but eliminates most of the phase information seen in ear-referenced data. A bipolar channel using phase-coupled areas also includes both phase and amplitude information and has a significant practical advantage since fewer channels required.
Data assimilation in the early phase: Kalman filtering RIMPUFF
DEFF Research Database (Denmark)
Astrup, P.; Turcanu, C.; Puch, R.O.
2004-01-01
of RODOS (Realtime Online DecisiOn Support system for nuclear emergencies) – has been developed. It is built on the Kalman filtering algorithm and it assimilates 10-minute averaged gamma dose rates measured atground level stations. Since the gamma rates are non-linear functions of the state vector...... variables, the applied Kalman filter is the so-called Extended Kalman filter. In more ways the implementation is non standard: 1) the number of state vectorvariables varies with time, and 2) the state vector variables are prediction updated with 1-minute time steps but only Kalman filtered every 10 minutes......, and this based on time averaged measurements. Given reasonable conditions, i.e. a spatially densedistribution of gamma monitors and a realistic wind field, the developed ADUM module is found to be able to enhance the prediction of the gamma dose field. Based on some of the Kalman filtering parameters, another...
Load compensation for single phase system using series active filter ...
African Journals Online (AJOL)
Load compensation for single phase system using series active filter. ... KK Mishra, R Gupta ... load varies from time to time, the non linear load ranging from voltage source type harmonic load (VSHL) dominant to current source type harmonic ...
Secure optical verification using dual phase-only correlation
International Nuclear Information System (INIS)
Liu, Wei; Liu, Shutian; Zhang, Yan; Xie, Zhenwei; Liu, Zhengjun
2015-01-01
We introduce a security-enhanced optical verification system using dual phase-only correlation based on a novel correlation algorithm. By employing a nonlinear encoding, the inherent locks of the verification system are obtained in real-valued random distributions, and the identity keys assigned to authorized users are designed as pure phases. The verification process is implemented in two-step correlation, so only authorized identity keys can output the discriminate auto-correlation and cross-correlation signals that satisfy the reset threshold values. Compared with the traditional phase-only-correlation-based verification systems, a higher security level against counterfeiting and collisions are obtained, which is demonstrated by cryptanalysis using known attacks, such as the known-plaintext attack and the chosen-plaintext attack. Optical experiments as well as necessary numerical simulations are carried out to support the proposed verification method. (paper)
Bandwidth Controllable Tunable Filter for Hyper-/Multi-Spectral Imager, Phase I
National Aeronautics and Space Administration — This SBIR Phase I proposal introduces a fast speed bandwidth controllable tunable filter for hyper-/multi-spectral (HS/MS) imagers. It dynamically passes a variable...
Directory of Open Access Journals (Sweden)
Hua-Pin Chen
2010-01-01
Full Text Available This paper introduces a novel voltage-mode multifunction biquadratic filter with single input and four outputs using two plus-type differential difference current conveyors (DDCCs and four grounded passive components. The filter can realize inverting highpass, inverting bandpass, noninverting lowpass, and noninverting bandpass filter responses, simultaneously. It still maintains the following advantages: (i using grounded capacitors attractive for integration and absorbing shunt parasitic capacitance, (ii using grounded resistors at all X terminals of DDCCs suitable for the variations of filter parameters and absorbing series parasitic resistances at all X terminals of DDCCs, (iii high-input impedance good for cascadability, (iv no need to change the filter topology, (v no need to component-matching conditions, (vi low active and passive sensitivity performances, and (vii simpler configuration due to the use of plus-type DDCCs only. HSPICE and MATLAB simulations results are provided to demonstrate the theoretical analysis.
Filtered Carrier Phase Estimator for High-Order QAM Optical Systems
DEFF Research Database (Denmark)
Rozental, Valery; Kong, Deming; Corcoran, Bill
2018-01-01
We investigate, using Monte Carlo simulations, the performance characteristics and limits of a low-complexity filtered carrier phase estimator (F-CPE) in terms of cycle slip occurrences and SNR penalties. In this work, the F-CPE algorithm has been extended to include modulation formats whose oute...
Liu, Peilu; Li, Xinghua; Li, Haopeng; Su, Zhikun; Zhang, Hongxu
2017-10-12
In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC) filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter's pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA). In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection.
Simpplified extended Kalman filter phase noise estimation for CO-OFDM transmissions.
Nguyen, Tu T; Le, Son T; Wuilpart, Marc; Yakusheva, Tatiana; Mégret, Patrice
2017-10-30
We propose a flexible simplified extended Kalman filter (S-EKF) scheme that can be applied in both pilot-aided and blind modes for phase noise compensation in 16-QAM CO-OFDM transmission systems employing a small-to-moderate number of subcarriers. The performance of the proposed algorithm is evaluated and compared with conventional pilot-aided (PA) and blind phase search (BPS) methods via extensive an Monte Carlo simulation in a back-to-back configuration and with a dual polarization fiber transmission. For 64 subcarrier 32 Gbaud 16-QAM CO-OFDM systems with 200 kHz combined laser linewidths, an optical signal-to-noise ratio penalty as low as 1 dB can be achieved with the proposed S-EKF scheme using only 2 pilots in the pilot-aided mode and just 4 inputs in the blind mode, resulting in a spectrally efficient enhancement by a factor of 3 and a computational effort reduction by a factor of more than 50 in comparison with the conventional PA and the BPS methods, respectively.
Differential phase microscope and micro-tomography with a Foucault knife-edge scanning filter
Watanabe, N.; Hashizume, J.; Goto, M.; Yamaguchi, M.; Tsujimura, T.; Aoki, S.
2013-10-01
An x-ray differential phase microscope with a Foucault knife-edge scanning filter was set up at the bending magnet source BL3C, Photon Factory. A reconstructed phase profile from the differential phase image of an aluminium wire at 5.36 keV was fairly good agreement with the numerical simulation. Phase tomography of a biological specimen, such as an Artemia cyst, could be successfully demonstrated.
2010-07-01
... 40 Protection of Environment 22 2010-07-01 2010-07-01 false My system only has two or fewer filters-is there any special provision regarding individual filter turbidity monitoring? 141.562 Section 141.562 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS...
Energy Technology Data Exchange (ETDEWEB)
Karimi, S.; Saadate, S. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, GREEN-UHP, CNRS UMR 7037 (France); Poure, P. [Laboratoire d' Instrumentation Electronique de Nancy, LIEN, EA 3440, France Nancy Universite - Universite Henri Poincare de Nancy I, BP 239, 54506 Vandoeuvre les Nancy cedex (France)
2008-11-15
This paper discusses the design, implementation, experimental validation and performances of a fully digital fast power switch fault detection and compensation for three-phase shunt active power filters. The approach introduced in this paper minimizes the time interval between the fault occurrence and its diagnosis. This paper demonstrates the possibility to detect a faulty switch of the active filter in less than 10 {mu}s by using simultaneously a ''time criterion'' and a ''voltage criterion''. In order to attain this fast detection time a FPGA (Field Programmable Gate Array) is used. The other feature introduced in this approach is that the control scheme used to compensate the current load harmonics and fault tolerant scheme are both programmed in only one FPGA. ''FPGA in the loop'' prototyping results and fully experimental results based on a real active power filter verify satisfactory performances of the proposed method. (author)
Modelling of the modified-LLCL-filter-based single-phase grid-tied Aalborg inverter
DEFF Research Database (Denmark)
Liu, Zifa; Wu, Huiyun; Liu, Yuan
2017-01-01
Owing to less conduction and switching power losses, the recently proposed Aalborg inverter has high efficiency within a wide range of input DC voltage for single-phase DC/AC power conversion. In theory, the conduction power losses can be further decreased, if an LLCL-filter is adopted instead...... of an LCL-filter for a voltage source inverter, mainly due to the reduced inductance. The Aalborg inverter shows the characteristic of a current source inverter, when working in the `boost' state. Whether the LLCL-filter can meet the control requirement of this type inverter needs to be further explored....... In this study, the small signal analysis for the modified-LLCL-filter-based Aalborg inverter is addressed. Through the modelling, it can be proven that compared with the LCL-filter, the modified-LLCL-filter causes no extra control challenge for the Aalborg inverter, and therefore more inductance in the power...
Control strategies of active filters in the context of power conditioning
DEFF Research Database (Denmark)
Dan, Stan George; Benjamin, Doniga Daniel; Magureanu, R.
2005-01-01
performance of active filters, and thus constitute a viable improved approach for harmonic compensation. In this paper a parallel hybrid filter is studied for current harmonic compensation. The hybrid filter is formed by a single tuned LC filter per phase and a small-rated power three-phase active filter......Active Power Filters have been intensively explored in the past decade. Various topologies and control schemes have been documented aiming at reducing the cost and improving the performance of the compensation system. Hybrid active filters inherit the efficiency of passive filters and the improved......, which are directly connected in series without any matching transformer. The required rating of the active filter is much smaller than a conventional standalone active filter would be. No additional switching-ripple filter is required for the hybrid filter because the LC filter functions not only...
Directory of Open Access Journals (Sweden)
Peilu Liu
2017-10-01
Full Text Available In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter’s pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA. In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection.
Product Evaluation Task Force Phase Two report for MEB crud/filter aid
International Nuclear Information System (INIS)
Francis, A.J.
1991-01-01
It has been proposed that all Intermediate Level Wastes arising at Sellafield should be encapsulated prior to ultimate disposal. The Product Evaluation Task Force (PETF) was set up to investigate possible encapsulants and to produce an adequate data base to justify the preferred matrices. This report details the work carried out, under Phase 2 of the Product Evaluation Task Force programme, on MEB Crud/Filter Aid. Three possible types of encapsulants for MEB Crud/Filter Aid:- Inorganic cements, Polymer cements, and Polymers are evaluated using the Kepner Tregoe decision and analysis technique. This technique provides a methodology for scoring and ranking alternative options and evaluating any risks associated with an option. The analysis shows that for all four stages of waste management operations, ie Storage, Transport, handling and emplacement, Disposal and, Process, cement matrices are considerably superior to other potential matrices. A matrix, consisting of nine parts Blast Furnace Slag (BFS) to one part Ordinary Portland Cement (OPC) is recommended as the preferred matrix for Phase 3 studies on MEB/Filter Aid. (author)
Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter
Energy Technology Data Exchange (ETDEWEB)
Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao [Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573 (Japan)
2016-01-28
Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke’s tabulated data.
Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter
International Nuclear Information System (INIS)
Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao
2016-01-01
Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke’s tabulated data
Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter
Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao
2016-01-01
Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke's tabulated data.
Computation of the lock-in ranges of phase-locked loops with PI filter
Aleksandrov, Konstantin D.; Kuznetsov, Nikolay; Leonov, Gennady A.; Neittaanmäki, Pekka; Yuldashev, Marat V.; Yuldashev, Renat V.
2016-01-01
In the present work the lock-in range of PLL-based circuits with proportionallyintegrating filter and sinusoidal phase-detector characteristics are studied. Considered circuits have sinusoidal phase detector characteristics. Analytical approach based on the methods of phase plane analysis is applied to estimate the lock-in ranges of the circuits under consideration. Obtained analytical results are compared with simulation results.
Phase-correcting non-local means filtering for diffusion-weighted imaging of the spinal cord.
Kafali, Sevgi Gokce; Çukur, Tolga; Saritas, Emine Ulku
2018-02-09
DWI suffers from low SNR when compared to anatomical MRI. To maintain reasonable SNR at relatively high spatial resolution, multiple acquisitions must be averaged. However, subject motion or involuntary physiological motion during diffusion-sensitizing gradients cause phase offsets among acquisitions. When the motion is localized to a small region, these phase offsets become particularly problematic. Complex averaging of acquisitions lead to cancellations from these phase offsets, whereas magnitude averaging results in noise amplification. Here, we propose an improved reconstruction for multi-acquisition DWI that effectively corrects for phase offsets while reducing noise. Each acquisition is processed with a refocusing reconstruction for global phase correction and a partial k-space reconstruction via projection-onto-convex-sets (POCS). The proposed reconstruction then embodies a new phase-correcting non-local means (PC-NLM) filter. PC-NLM is performed on the complex-valued outputs of the POCS algorithm aggregated across acquisitions. The PC-NLM filter leverages the shared structure among multiple acquisitions to simultaneously alleviate nuisance factors including phase offsets and noise. Extensive simulations and in vivo DWI experiments of the cervical spinal cord are presented. The results demonstrate that the proposed reconstruction improves image quality by mitigating signal loss because of phase offsets and reducing noise. Importantly, these improvements are achieved while preserving the accuracy of apparent diffusion coefficient maps. An improved reconstruction incorporating a PC-NLM filter for multi-acquisition DWI is presented. This reconstruction can be particularly beneficial for high-resolution or high-b-value DWI acquisitions that suffer from low SNR and phase offsets from local motion. © 2018 International Society for Magnetic Resonance in Medicine.
DEFF Research Database (Denmark)
Cimoli, Bruno; Johansen, Tom Keinicke; Olmos, Juan Jose Vegas
2018-01-01
We report a high performance linear phase low pass filter (LPF) designed for partial response (PR) modulations. For the implementation, we adopted microstrip technology and a variant of the standard stepped‐impedance technique. Defected ground structures (DGS) are used for increasing the characte......We report a high performance linear phase low pass filter (LPF) designed for partial response (PR) modulations. For the implementation, we adopted microstrip technology and a variant of the standard stepped‐impedance technique. Defected ground structures (DGS) are used for increasing...... the characteristic impedance of transmission lines. Experimental results prove that the proposed filter can successfully modulate a non‐return‐to‐zero (NRZ) signal into a five levels PR one....
Directory of Open Access Journals (Sweden)
Wanli Liu
2015-07-01
Full Text Available Differential interferometric synthetic aperture radar has been shown to be effective for monitoring subsidence in coal mining areas. Phase unwrapping can have a dramatic influence on the monitoring result. In this paper, a filtering-based phase unwrapping algorithm in combination with path-following is introduced to unwrap differential interferograms with high noise in mining areas. It can perform simultaneous noise filtering and phase unwrapping so that the pre-filtering steps can be omitted, thus usually retaining more details and improving the detectable deformation. For the method, the nonlinear measurement model of phase unwrapping is processed using a simplified Cubature Kalman filtering, which is an effective and efficient tool used in many nonlinear fields. Three case studies are designed to evaluate the performance of the method. In Case 1, two tests are designed to evaluate the performance of the method under different factors including the number of multi-looks and path-guiding indexes. The result demonstrates that the unwrapped results are sensitive to the number of multi-looks and that the Fisher Distance is the most suitable path-guiding index for our study. Two case studies are then designed to evaluate the feasibility of the proposed phase unwrapping method based on Cubature Kalman filtering. The results indicate that, compared with the popular Minimum Cost Flow method, the Cubature Kalman filtering-based phase unwrapping can achieve promising results without pre-filtering and is an appropriate method for coal mining areas with high noise.
Bit-rate-transparent optical RZ-to-NRZ format conversion based on linear spectral phase filtering
DEFF Research Database (Denmark)
Maram, Reza; Da Ros, Francesco; Guan, Pengyu
2017-01-01
We propose a novel and strikingly simple design for all-optical bit-rate-transparent RZ-to-NRZ conversion based on optical phase filtering. The proposed concept is experimentally validated through format conversion of a 640 Gbit/s coherent RZ signal to NRZ signal.......We propose a novel and strikingly simple design for all-optical bit-rate-transparent RZ-to-NRZ conversion based on optical phase filtering. The proposed concept is experimentally validated through format conversion of a 640 Gbit/s coherent RZ signal to NRZ signal....
Generalized Phase contrast and matched filtering for speckle‐free patterned illumination
DEFF Research Database (Denmark)
Palima, Darwin; Bañas, Andrew Rafael; Villangca, Mark Jayson
2013-01-01
Generalized Phase Contrast (GPC) and matched‐filtering GPC use tandem diffractive phase elements on Fourier‐conjugate planes of a 4f optical processor to efficiently reshape incident light into a pattern that resembles the input phase modulation pattern. The synthesized patterns are inherently...... to optically trap and mechanically manipulate microparticles, GPC has also been applied for laser beamshaping, optical phase cryptography, and greyscale image projection. Recent reports from our collaborators highlight that GPC‐based spatial lightshaping, when combined with temporal focusing and multiphoton...... excitation, exhibits some robustness against light scattering and, hence, makes a promising tool for spatially precise targeting of deeper subsurface neurons using minimally speckled patterned illumination for multiphoton excitation....
Generation of complementary sampled phase-only holograms.
Tsang, P W M; Chow, Y T; Poon, T-C
2016-10-03
If an image is uniformly down-sampled into a sparse form and converted into a hologram, the phase component alone will be adequate to reconstruct the image. However, the appearance of the reconstructed image is degraded with numerous empty holes. In this paper, we present a low complexity and non-iterative solution to this problem. Briefly, two phase-only holograms are generated for an image, each based on a different down-sampling lattice. Subsequently, the holograms are displayed alternately at high frame rate. The reconstructed images of the 2 holograms will appear to be a single, densely sampled image with enhance visual quality.
Design of multi-wavelength tunable filter based on Lithium Niobate
Zhang, Ailing; Yao, Yuan; Zhang, Yue; Song, Hongyun
2018-05-01
A multi-wavelength tunable filter is designed. It consists of multiple waveguides among multiple waveguide gratings. A pair of electrodes were placed on both sides of each waveguide. The tunable filter uses the electro-optic effect of Lithium Niobate to tune the phase caused by each waveguide. Consequently, the wavelength and wavelength spacing of the filter are tuned by changing external voltages added on the electrode pairs. The tunable property of the filter is analyzed by phase matching condition and transfer-matrix method. Numerical results show that not only multiple wavelengths with narrow bandwidth are tuned with nearly equal spacing by synchronously changing the voltages added on all electrode pairs, but also the number of wavelengths is determined by the number of phase shifts caused by electrode pairs. Furthermore, due to the electro-optic effect of Lithium Niobate, the tuning speed of the filter can reach the order of ns.
Zhang, Qun; Yang, Yanfu; Xiang, Qian; Zhou, Zhongqing; Yao, Yong
2018-02-01
A joint compensation scheme based on cascaded Kalman filter is proposed, which can implement polarization tracking, channel equalization, frequency offset, and phase noise compensation simultaneously. The experimental results show that the proposed algorithm can not only compensate multiple channel impairments simultaneously but also improve the polarization tracking capacity and accelerate the convergence speed. The scheme has up to eight times faster convergence speed compared with radius-directed equalizer (RDE) + Max-FFT (maximum fast Fourier transform) + BPS (blind phase search) and can track up polarization rotation 60 times and 15 times faster than that of RDE + Max-FFT + BPS and CMMA (cascaded multimodulus algorithm) + Max-FFT + BPS, respectively.
Moving Average Filter-Based Phase-Locked Loops: Performance Analysis and Design Guidelines
DEFF Research Database (Denmark)
Golestan, Saeed; Ramezani, Malek; Guerrero, Josep M.
2014-01-01
this challenge, incorporating moving average filter(s) (MAF) into the PLL structure has been proposed in some recent literature. A MAF is a linear-phase finite impulse response filter which can act as an ideal low-pass filter, if certain conditions hold. The main aim of this paper is to present the control...... design guidelines for a typical MAF-based PLL. The paper starts with the general description of MAFs. The main challenge associated with using the MAFs is then explained, and its possible solutions are discussed. The paper then proceeds with a brief overview of the different MAF-based PLLs. In each case......, the PLL block diagram description is shown, the advantages and limitations are briefly discussed, and the tuning approach (if available) is evaluated. The paper then presents two systematic methods to design the control parameters of a typical MAF-based PLL: one for the case of using a proportional...
Kesler, Benjamin; O'Brien, Thomas; Dallesasse, John M.
2017-02-01
A novel method for controlling the transverse lasing modes in both proton implanted and oxide-confined vertical- cavity surface-emitting lasers (VCSELs) with a multi-layer, patterned, dielectric anti-phase (DAP) filter is pre- sented. Using a simple photolithographic liftoff process, dielectric layers are deposited and patterned on individual VCSELs to modify (increase or decrease) the mirror reflectivity across the emission aperture via anti-phase reflections, creating spatially-dependent threshold material gain. The shape of the dielectric pattern can be tailored to overlap with specific transverse VCSEL modes or subsets of transverse modes to either facilitate or inhibit lasing by decreasing or increasing, respectively, the threshold modal gain. A silicon dioxide (SiO2) and titanium dioxide (TiO2) anti-phase filter is used to achieve a single-fundamental-mode, continuous-wave output power greater than 4.0 mW in an oxide-confined VCSEL at a lasing wavelength of 850 nm. A filter consisting of SiO2 and TiO2 is used to facilitate injection-current-insensitive fundamental mode and lower order mode lasing in proton implanted VCSELs at a lasing wavelength of 850 nm. Higher refractive index dielectric materials such as amorphous silicon (a-Si) can be used to increase the effectiveness of the anti-phase filter on proton implanted devices by reducing the threshold modal gain of any spatially overlapping modes. This additive, non-destructive method allows for mode selection at any lasing wavelength and for any VCSEL layer structure without the need for semiconductor etching or epitaxial regrowth. It also offers the capability of designing a filter based upon available optical coating materials.
DEFF Research Database (Denmark)
Lloret, Juan; Ramos, Francisco; Xue, Weiqi
2011-01-01
Different optical filtering scenarios involving microwave photonic phase shifters based on semiconductor optical amplifiers are investigated numerically as well as experimentally with respect to noise performance. Investigations on the role of the modulation depth and number of elements in cascad...... shifting stages are also carried out. Suppression of the noise level by more than 5 dB has been achieved in schemes based on band-pass optical filtering when three phase shifting stages are cascaded....
Face identification with frequency domain matched filtering in mobile environments
Lee, Dong-Su; Woo, Yong-Hyun; Yeom, Seokwon; Kim, Shin-Hwan
2012-06-01
Face identification at a distance is very challenging since captured images are often degraded by blur and noise. Furthermore, the computational resources and memory are often limited in the mobile environments. Thus, it is very challenging to develop a real-time face identification system on the mobile device. This paper discusses face identification based on frequency domain matched filtering in the mobile environments. Face identification is performed by the linear or phase-only matched filter and sequential verification stages. The candidate window regions are decided by the major peaks of the linear or phase-only matched filtering outputs. The sequential stages comprise a skin-color test and an edge mask filtering test, which verify color and shape information of the candidate regions in order to remove false alarms. All algorithms are built on the mobile device using Android platform. The preliminary results show that face identification of East Asian people can be performed successfully in the mobile environments.
Quasi-phase-matching of only even-order high harmonics.
Diskin, Tzvi; Cohen, Oren
2014-03-24
High harmonic spectrum of a quasi-monochromatic pump that interacts with isotropic media consists of only odd-order harmonics. Addition of a secondary pump, e.g. a static field or the second harmonic of the primary pump, can results with generation of both odd and even harmonics of the primary pump. We propose a method for quasi-phase matching of only the even-order harmonics of the primary pump. We formulate a theory for this process and demonstrate it numerically. We also show that it leads to attosecond pulse trains with constant carrier envelop phase and high repetition rate.
Proposal of a resonant controller for a three phase four wire grid-connected shunt hybrid filter
DEFF Research Database (Denmark)
Candela, J. I.; Rodriguez, P.; Luna, A.
2009-01-01
This paper present a three-phase four wire hybrid filter able to perform a selective cancellation of harmonic currents based on resonant controllers. As it will be shown in this work, this kind of control permits to enhance the bandwidth of the filter controller, without hindering the stability...
Power filtering of n-th order in the fractional Fourier domain
Alieva, T.; Calvo, M.L.; Bastiaans, M.J.
2002-01-01
The main properties of the power filtering operation in the fractional Fourier domain and its relationship to the differentiation operation are considered. The application of linear power filtering for solving the phase retrieval problem from only intensity distributions is proposed. The optical
Shu, Tong; Li, Yan; Yu, Miao; Zhang, Yifan; Zhou, Honghang; Qiu, Jifang; Guo, Hongxiang; Hong, Xiaobin; Wu, Jian
2018-02-01
Performance of Extended Kalman Filter combined with the Viterbi-Viterbi phase estimation (VVPE-EKF) for joint phase noise mitigation and amplitude noise equalization is experimental demonstrated. Experimental results show that, for 11.2 Gbaud SP-16-QAM, the proposed VVPE-EKF achieves 0.9 dB required OSNR reduction at bit error ratio (BER) of 3.8e-3 compared to the VVPE. The result of maximum likelihood combined with VVPE (VVPE-ML) is only 0.3 dB. For 28 GBaud SP-16-QAM signal, VVPE-EKF achieves 3 dB required OSNR reduction at BER=3.8e-3 (7% HD-FEC threshold) compared to VVPE. And VVPE-ML can reduce the required OSNR for 1.7 dB compared to the VVPE. VVPE-EKF outperforms DD-EKF 3.7 dB and 0.7 dB for 11.2 GBaud and 28 GBaud system, respectively.
A filtering technique for solving the advection equation in two-phase flow problems
International Nuclear Information System (INIS)
Devals, C.; Heniche, M.; Bertrand, F.; Tanguy, P.A.; Hayes, R.E.
2004-01-01
The aim of this work is to develop a numerical strategy for the simulation of two-phase flow in the context of chemical engineering applications. The finite element method has been chosen because of its flexibility to deal with complex geometries. One of the key points of two-phase flow simulation is to determine precisely the position of the interface between the two phases, which is an unknown of the problem. In this case, the interface can be tracked by the advection of the so-called color function. It is well known that the solution of the advection equation by most numerical schemes, including the Streamline Upwind Petrov-Galerkin (SUPG) method, may exhibit spurious oscillations. This work proposes an approach to filter out these oscillations by means of a change of variable that is efficient for both steady state and transient cases. First, the filtering technique will be presented in detail. Then, it will be applied to two-dimensional benchmark problems, namely, the advection skew to the mesh and the Zalesak's problems. (author)
Phase-only stereoscopic hologram calculation based on Gerchberg–Saxton iterative algorithm
International Nuclear Information System (INIS)
Xia Xinyi; Xia Jun
2016-01-01
A phase-only computer-generated holography (CGH) calculation method for stereoscopic holography is proposed in this paper. The two-dimensional (2D) perspective projection views of the three-dimensional (3D) object are generated by the computer graphics rendering techniques. Based on these views, a phase-only hologram is calculated by using the Gerchberg–Saxton (GS) iterative algorithm. Comparing with the non-iterative algorithm in the conventional stereoscopic holography, the proposed method improves the holographic image quality, especially for the phase-only hologram encoded from the complex distribution. Both simulation and optical experiment results demonstrate that our proposed method can give higher quality reconstruction comparing with the traditional method. (special topic)
International Nuclear Information System (INIS)
Keresnyei, Róbert; Hejjel, László; Megyeri, Péter; Zidarics, Zoltán
2015-01-01
The availability of microcomputer-based portable devices facilitates the high-volume multichannel biosignal acquisition and the analysis of their instantaneous oscillations and inter-signal temporal correlations. These new, non-invasively obtained parameters can have considerable prognostic or diagnostic roles. The present study investigates the inherent signal delay of the obligatory anti-aliasing filters. One cycle of each of the 8 electrocardiogram (ECG) and 4 photoplethysmogram signals from healthy volunteers or artificially synthesised series were passed through 100–80–60–40–20 Hz 2–4–6–8th order Bessel and Butterworth filters digitally synthesized by bilinear transformation, that resulted in a negligible error in signal delay compared to the mathematical model of the impulse- and step responses of the filters. The investigated filters have as diverse a signal delay as 2–46 ms depending on the filter parameters and the signal slew rate, which is difficult to predict in biological systems and thus difficult to compensate for. Its magnitude can be comparable to the examined phase shifts, deteriorating the accuracy of the measurement. As a conclusion, identical or very similar anti-aliasing filters with lower orders and higher corner frequencies, oversampling, and digital low pass filtering are recommended for biosignal acquisition intended for inter-signal phase shift analysis. (note)
Power filtering of nth order in the fractional Fourier domain
International Nuclear Information System (INIS)
Alieva, Tatiana; Calvo, Maria Luisa; Bastiaans, Martin J.
2002-01-01
The main properties of the power filtering operation in the fractional Fourier domain and its relationship to the differentiation operation are considered. The application of linear power filtering for solving the phase retrieval problem from intensity distributions only is proposed. The optical configuration for the experimental realization of the method is discussed. (author)
Singh, Yashi; Hussain, Ikhlaq; Singh, Bhim; Mishra, Sukumar
2018-03-01
In this paper, power quality features such as harmonics mitigation, power factor correction with active power filtering are addressed in a single-stage, single-phase solar photovoltaic (PV) grid tied system. The Power Balance Theory (PBT) with perturb and observe based maximum power point tracking algorithm is proposed for the mitigation of power quality problems in a solar PV grid tied system. The solar PV array is interfaced to a single phase AC grid through a Voltage Source Converter (VSC), which provides active power flow from a solar PV array to the grid as well as to the load and it performs harmonics mitigation using PBT based control. The solar PV array power varies with sunlight and due to this, the solar PV grid tied VSC works only 8-10 h per day. At night, when PV power is zero, the VSC works as an active power filter for power quality improvement, and the load active power is delivered by the grid to the load connected at the point of common coupling. This increases the effective utilization of a VSC. The system is modelled and simulated using MATLAB and simulated responses of the system at nonlinear loads and varying environmental conditions are also validated experimentally on a prototype developed in the laboratory.
Li, Linqian; Feng, Yiqiao; Zhang, Wenbo; Cui, Nan; Xu, Hengying; Tang, Xianfeng; Xi, Lixia; Zhang, Xiaoguang
2017-07-01
A joint carrier recovery scheme for polarization division multiplexing (PDM) coherent optical transmission system is proposed and demonstrated, in which the extended Kalman filter (EKF) is exploited to estimate and equalize the carrier frequency offset (CFO) and carrier phase noise (CPN) simultaneously. The proposed method is implemented and verified in the PDM-QPSK system and the PDM-16QAM system with the comparisons to conventional improved Mth-power (IMP) algorithm for CFO estimation, blind phase search (BPS) algorithm or Viterbi-Viterbi (V-V) algorithm for CPN recovery. It is demonstrated that the proposed scheme shows high CFO estimation accuracy, with absolute mean estimation error below 1.5 MHz. Meanwhile, the proposed method has the CFO tolerance of [±3 GHz] for PDM-QPSK system and [±0.9 GHz] for PDM-16QAM system. Compare with IMP/BPS and IMP/V-V, the proposed scheme can enhance the linewidth symbol duration product from 3 × 10-4 (IMP/BPS) and 2 × 10-4 (IMP/V-V) to 1 × 10-3 for PDM-QPSK, and from 1 × 10-4 (IMP/BPS) to 3 × 10-4 for PDM-16QAM, respectively, at the 1 dB optical signal-to-noise ratio (OSNR) penalty. The proposed Kalman filter also shows a fast convergence with only 100 symbols and much lower computational complexity.
DEFF Research Database (Denmark)
Zibar, Darko; Carvalho, L.; Piels, Molly
2014-01-01
We show that phase noise estimation based on Bayesian filtering outperforms conventional time-domain approaches in the presence of moderate measurement noise. Additionally, carrier synchronization based on Bayesian filtering, in combination with expectation maximization, is demonstrated for the f...
Lloret, Juan; Morthier, Geert; Ramos, Francisco; Sales, Salvador; Van Thourhout, Dries; Spuesens, Thijs; Olivier, Nicolas; Fédéli, Jean-Marc; Capmany, José
2012-05-07
A broadband microwave photonic phase shifter based on a single III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic silicon-on-insulator waveguide is reported. The phase shift tunability is accomplished by modifying the effective index through carrier injection. A comprehensive semi-analytical model aiming at predicting its behavior is formulated and confirmed by measurements. Quasi-linear and continuously tunable 2π phase shifts at radiofrequencies greater than 18 GHz are experimentally demonstrated. The phase shifter performance is also evaluated when used as a key element in tunable filtering schemes. Distortion-free and wideband filtering responses with a tuning range of ~100% over the free spectral range are obtained.
Filters for stochastic cooling of longitudinal beam emittance
International Nuclear Information System (INIS)
Kramer, S.L.; Konecny, R.; Simpson, J.; Wright, A.J.
1983-03-01
The shorted stub filter (SSF) has been used extensively to provide the electronics gain shaping for stochastic cooling of longitudinal beam emittance. The repetitive notch of this filter results from the cancellation of the incident signal by the reflected signal at frequencies where the cable electrical length equals an integer number of half wavelengths. Variations in notch depth of the SSF have been approximately compensated by a rather complicated system. Dispersion of the notch frequency resulting from variation of the phase velocity can also be approximately corrected using tuned imperfections in the shorted cable. Dispersion due to imperfections in the coaxial cable can be quite significant and can only be compensated for by costly construction techniques. This paper describes another type of notch filter. Although this filter has been mentioned previously, this analysis demonstrates the advantages of this filter in providing small notch dispersion and other properties necessary for stochastic cooling systems. Because this filter uses only forward signals, it is quite insensitive to imperfections in cables and components, and can therefore be constructed from commercially available components
Page, Ralph H.; Doty, Patrick F.
2017-08-01
The various technologies presented herein relate to a tiled filter array that can be used in connection with performance of spatial sampling of optical signals. The filter array comprises filter tiles, wherein a first plurality of filter tiles are formed from a first material, the first material being configured such that only photons having wavelengths in a first wavelength band pass therethrough. A second plurality of filter tiles is formed from a second material, the second material being configured such that only photons having wavelengths in a second wavelength band pass therethrough. The first plurality of filter tiles and the second plurality of filter tiles can be interspersed to form the filter array comprising an alternating arrangement of first filter tiles and second filter tiles.
Robust DOA Estimation of Harmonic Signals Using Constrained Filters on Phase Estimates
DEFF Research Database (Denmark)
Karimian-Azari, Sam; Jensen, Jesper Rindom; Christensen, Mads Græsbøll
2014-01-01
In array signal processing, distances between receivers, e.g., microphones, cause time delays depending on the direction of arrival (DOA) of a signal source. We can then estimate the DOA from the time-difference of arrival (TDOA) estimates. However, many conventional DOA estimators based on TDOA...... estimates are not optimal in colored noise. In this paper, we estimate the DOA of a harmonic signal source from multi-channel phase estimates, which relate to narrowband TDOA estimates. More specifically, we design filters to apply on phase estimates to obtain a DOA estimate with minimum variance. Using...
DEFF Research Database (Denmark)
Zhuo, Fang; Wu, Longhui; Chen, Zhe
2009-01-01
on zero-cross detection can't work effectively in small rating stand-alone power grid. Then a soft phase locked loop with additional filter is proposed. It can lock the phase angle on to the positive sequence of fundamental voltage accurately and rapidly. It ensures the performance of APF applied...... in the small rating stand-alone power grid. Moreover, the soft phase locked loop is easy to be implemented in a Digital Signal Processor (DSP). Simulation and experimental results validate that the soft phase locked loop has satisfactory performance.......Traditional LC filters can't work stably in small rating stand-alone power grid. So active power filter (APF) is becoming an important tool to solve the power quality problem in small rating stand-alone power grid. In most current detection algorithm of APF, it needs a synchronizing signal. Firstly...
Generalized Phase Contrast with matched filtering using LCoS pico-projectors
Bañas, Andrew Rafael; Palima, Darwin; Glückstad, Jesper
2012-01-01
We report a beam shaping system for generating high intensity programmable opticalspots using mGPC: matched filtering combined with Generalized Phase Contrastapplying two consumer handheld pico-projectors. Such a system presents a low costalternative for optical trapping and manipulation, optical lattices and other beamshaping applications usually implemented with high-end spatial light modulators.Portable pico-projectors based on liquid crystal on silicon (LCoS) devices were usedas binary ph...
DEFF Research Database (Denmark)
Ji, Junhao; Wu, Weimin; He, Yuanbin
2015-01-01
The single-phase power converter topologies evolving of photovoltaic applications are still including passive filters, like the LCLor LLCL-filter. Compared with the LCL-filter, the total inductance of the LLCL-filter can be reduced a lot. However, due to the resonant inductor in series...... with the bypass capacitor, the differential mode (DM) electromagnetic interference (EMI) noise attenuation of an LLCL-filter-based grid-tied inverter declines. Conventionally, a capacitor was inserted in parallel with the LC resonant circuit branch of the LLCL-filter to suppress the DM EMI noise. In order...... to achieve a small value of capacitor as well as to minimize the additional reactive power, a novel simple DM EMI suppressor for the LLCL-filter-based system is proposed. The characters of two kinds of DM EMI suppressor are analyzed and compared in detail. Simulations and experiments on a 0.5-kW 110-V/50-Hz...
Design, control, and implementation of LCL-filter-based shunt active power filters
DEFF Research Database (Denmark)
Tang, Yi; Loh, Poh Chiang; Wang, Peng
2011-01-01
This paper concentrates on the design, control and implementation of an LCL-filter-based shunt active power filter (SAPF), which can effectively compensate harmonic currents produced by nonlinear loads in a three-phase three-wire power system. The use of LCL-filter at the output end of SAPF offer......-loop control system, and active damping implemented with fewer current sensors are all addressed here. An analytical design example is finally presented, being supported with experimental results, to verify its effectiveness and practicality.......This paper concentrates on the design, control and implementation of an LCL-filter-based shunt active power filter (SAPF), which can effectively compensate harmonic currents produced by nonlinear loads in a three-phase three-wire power system. The use of LCL-filter at the output end of SAPF offers...
FULL SCALE REGENERABLE HEPA FILTER DESIGN USING SINTERED METAL FILTER ELEMENTS
International Nuclear Information System (INIS)
Gil Ramos; Kenneth Rubow; Ronald Sekellick
2002-01-01
A Department of Energy funded contract involved the development of porous metal as a HEPA filter, and the subsequent design of a full-scale regenerable HEPA filtration system (RHFS). This RHFS could replace the glass fiber HEPA filters currently being used on the high level waste (HLW) tank ventilation system with a system that would be moisture tolerant, durable, and cleanable in place. The origins of the contract are a 1996 investigation at the Savannah River Technology Center (SRTC) regarding the use of porous metal as a HEPA filter material. This contract was divided into Phases I, IIA and IIB. Phase I of the contract evaluated simple filter cylinders in a simulated High Level Waste (HLW) environment and the ability to clean and regenerate the filter media after fouling. Upon the successful completion of Phase I, Phase IIA was conducted, which included lab scale prototype testing and design of a full-scale system. The work completed under Phase IIA included development of a full-scale system design, development of a filter media meeting the HEPA filtration efficiency that would also be regenerable using prescribed cleaning procedures, and the testing of a single element system prototype at Savannah River. All contract objectives were met. The filter media selected was a nickel material already under development at Mott, which met the HEPA filtration efficiency standard. The Mott nickel media met and exceeded the HEPA requirement, providing 99.99% removal against a requirement of 99.97%. Double open-ended elements of this media were provided to the Savannah River Test Center for HLW simulation testing in the single element prototype filter. These elements performed well and further demonstrated the practicality of a metallic media regenerable HEPA filter system. An evaluation of the manufacturing method on many elements demonstrated the reproducibility to meet the HEPA filtration requirement. The full-scale design of the Mott RHFS incorporated several important
Capmany, José; Pastor, Daniel; Martinez, Alfonso; Ortega, Beatriz; Sales, Salvador
2003-08-15
We report on a novel technical approach to the implementation of photonic rf filters that is based on the pi phase inversion that a rf modulating signal suffers in an electro-optic Mach-Zehnder modulator, which depends on whether the positive or the negative linear slope of the signal's modulation transfer function is employed. Experimental evidence is provided of the implementation of filters with negative coefficients that shows excellent agreement with results predicted by the theory.
International Nuclear Information System (INIS)
Boerzsoenyi, A.; Meroe, M.
2010-01-01
Complete text of publication follows. There is an increasing demand for active and precise dispersion control of ultrashort laser pulses. In chirped pulse amplification (CPA) laser systems, the dispersion of the optical elements of the laser has to be compensated at least to the fourth order to obtain high temporal contrast compressed pulses. Nowadays the most convenient device for active and programmable control of spectral phase and amplitude of broadband laser pulses is the acousto-optic programmable dispersive filter (AOPDF), claimed to be able to adjust the spectral phase up to the fourth order. Although it has been widely used, surprisingly enough there has been only a single, low resolution measurement reported on the accuracy of the induced spectral phase shift of the device. In our paper we report on the first systematic experiment aiming at the precise characterization of an AOPDF device. In the experiment the spectral phase shift of the AOPDF device was measured by spectrally and spatially resolved interferometry, which is especially powerful tool to determine small dispersion values with high accuracy. Besides the spectral phase dispersion, we measured both the propagation direction angular dispersion (PDAD) and the phase front angular dispersion (PhFAD). Although the two quantities are equal for plane waves, there may be noticeable difference for Gaussian pulses. PDAD was determined simply by focusing the beam on the slit of an imaging spectrograph, while PhFAD was measured by the use of an inverted Mach-Zehnder interferometer and an imaging spectrograph. In the measurements, the spectral phase shift and both types of angular dispersion have been recorded upon the systematic change of all the accessible functions of the acousto-optic programmable dispersive filter. The measured values of group delay dispersion (GDD) and third order dispersion (TOD) have been found to agree with the preset values within the error of the measurement (1 fs 2 and 10 fs 3
MOSFET-Only Mixer/IIR Filter with Gain using Parametric Amplification
DEFF Research Database (Denmark)
Custódio, José R.; Oliveira, J.; Oliveira, L. B.
2010-01-01
This paper describes the design of a discrete-time passive Mixer/IIR filter. The use of an improved MOS Parametric Amplification leads to a moderate gain in the signal path and improved noise performance, instead of the conversion loss inherent to passive mixers. Simulation results demonstrate th...
Parallel power electronics filters in three-phase four-wire systems principle, control and design
Wong, Man-Chung; Lam, Chi-Seng
2016-01-01
This book describes parallel power electronic filters for 3-phase 4-wire systems, focusing on the control, design and system operation. It presents the basics of power-electronics techniques applied in power systems as well as the advanced techniques in controlling, implementing and designing parallel power electronics converters. The power-quality compensation has been achieved using active filters and hybrid filters, and circuit models, control principles and operational practice problems have been verified by principle study, simulation and experimental results. The state-of-the-art research findings were mainly developed by a team at the University of Macau. Offering background information and related novel techniques, this book is a valuable resource for electrical engineers and researchers wanting to work on energy saving using power-quality compensators or renewable energy power electronics systems. .
Flexible time-varying filter banks
Tuncer, Temel E.; Nguyen, Truong Q.
1993-09-01
Linear phase maximally flat FIR Butterworth filter approximations are discussed and a new filter design method is introduced. This variable cutoff filter design method uses the cosine modulated versions of a prototype filter. The design procedure is simple and different variants of this procedure can be used to obtain close to optimum linear phase filters. Using this method, flexible time-varying filter banks with good reconstruction error are introduced. These types of oversampled filter banks have small magnitude error which can be easily controlled by the appropriate choice of modulation frequency. This error can be further decreased by magnitude equalization without increasing the computational complexity considerably. Two dimensional design examples are also given.
Combining Generalized Phase Contrast with matched filtering into a versatile beam shaping approach
DEFF Research Database (Denmark)
Glückstad, Jesper; Palima, Darwin
2010-01-01
We adapt concepts from matched filtering to propose a method for generating reconfigurable multiple beams. Combined with the Generalized Phase Contrast (GPC) technique, the proposed method coined mGPC can yield dynamically reconfigurable optical beam arrays with high light efficiency for optical...... manipulation, high-speed sorting and other parallel spatial light applications [1]....
Sang, Hongqiang; Yang, Chenghao; Liu, Fen; Yun, Jintian; Jin, Guoguang; Chen, Fa
2016-12-01
Hand physiological tremor of surgeons can cause vibration at the surgical instrument tip, which may make it difficult for the surgeon to perform fine manipulations of tissue, needles, and sutures. A zero phase adaptive fuzzy Kalman filter (ZPAFKF) is proposed to suppress hand tremor and vibration of a robotic surgical system. The involuntary motion can be reduced by adding a compensating signal that has the same magnitude and frequency but opposite phase with the tremor signal. Simulations and experiments using different filters were performed. Results show that the proposed filter can avoid the loss of useful motion information and time delay, and better suppress minor and varying tremor. The ZPAFKF can provide less error, preferred accuracy, better tremor estimation, and more desirable compensation performance, to suppress hand tremor and decrease vibration at the surgical instrument tip. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Hysteresis Control for Shunt Active Power Filter under Unbalanced Three-Phase Load Conditions
Directory of Open Access Journals (Sweden)
Z. Chelli
2015-01-01
Full Text Available This paper focuses on a four-wire shunt active power filter (APF control scheme proposed to improve the performance of the APF. This filter is used to compensate harmonic distortion in three-phase four-wire systems. Several harmonic suppression techniques have been widely proposed and applied to minimize harmonic effects. The proposed control scheme can compensate harmonics and reactive power of the nonlinear loads simultaneously. This approach is compared to the conventional shunt APF reference compensation strategy. The developed algorithm is validated by simulation tests using MATLAB Simulink. The obtained results have demonstrated the effectiveness of the proposed scheme and confirmed the theoretical developments for balanced and unbalanced nonlinear loads.
[Recognition of walking stance phase and swing phase based on moving window].
Geng, Xiaobo; Yang, Peng; Wang, Xinran; Geng, Yanli; Han, Yu
2014-04-01
Wearing transfemoral prosthesis is the only way to complete daily physical activity for amputees. Motion pattern recognition is important for the control of prosthesis, especially in the recognizing swing phase and stance phase. In this paper, it is reported that surface electromyography (sEMG) signal is used in swing and stance phase recognition. sEMG signal of related muscles was sampled by Infiniti of a Canadian company. The sEMG signal was then filtered by weighted filtering window and analyzed by height permitted window. The starting time of stance phase and swing phase is determined through analyzing special muscles. The sEMG signal of rectus femoris was used in stance phase recognition and sEMG signal of tibialis anterior is used in swing phase recognition. In a certain tolerating range, the double windows theory, including weighted filtering window and height permitted window, can reach a high accuracy rate. Through experiments, the real walking consciousness of the people was reflected by sEMG signal of related muscles. Using related muscles to recognize swing and stance phase is reachable. The theory used in this paper is useful for analyzing sEMG signal and actual prosthesis control.
Regenerable Carbon Filter, Phase I
National Aeronautics and Space Administration — A Regenerable Carbon Filter (RCF) is proposed for the removal of carbonaceous particulate matter produced in Environmental Control and Life Support (ECLS) processes....
Effect of masking phase-only holograms on the quality of reconstructed images.
Deng, Yuanbo; Chu, Daping
2016-04-20
A phase-only hologram modulates the phase of the incident light and diffracts it efficiently with low energy loss because of the minimum absorption. Much research attention has been focused on how to generate phase-only holograms, and little work has been done to understand the effect and limitation of their partial implementation, possibly due to physical defects and constraints, in particular as in the practical situations where a phase-only hologram is confined or needs to be sliced or tiled. The present study simulates the effect of masking phase-only holograms on the quality of reconstructed images in three different scenarios with different filling factors, filling positions, and illumination intensity profiles. Quantitative analysis confirms that the width of the image point spread function becomes wider and the image quality decreases, as expected, when the filling factor decreases, and the image quality remains the same for different filling positions as well. The width of the image point spread function as derived from different filling factors shows a consistent behavior to that as measured directly from the reconstructed image, especially as the filling factor becomes small. Finally, mask profiles of different shapes and intensity distributions are shown to have more complicated effects on the image point spread function, which in turn affects the quality and textures of the reconstructed image.
Directory of Open Access Journals (Sweden)
Xingang Fu
2016-04-01
Full Text Available This paper investigates a novel recurrent neural network (NN-based vector control approach for single-phase grid-connected converters (GCCs with L (inductor, LC (inductor-capacitor and LCL (inductor-capacitor-inductor filters and provides their comparison study with the conventional standard vector control method. A single neural network controller replaces two current-loop PI controllers, and the NN training approximates the optimal control for the single-phase GCC system. The Levenberg–Marquardt (LM algorithm was used to train the NN controller based on the complete system equations without any decoupling policies. The proposed NN approach can solve the decoupling problem associated with the conventional vector control methods for L, LC and LCL-filter-based single-phase GCCs. Both simulation study and hardware experiments demonstrate that the neural network vector controller shows much more improved performance than that of conventional vector controllers, including faster response speed and lower overshoot. Especially, NN vector control could achieve very good performance using low switch frequency. More importantly, the neural network vector controller is a damping free controller, which is generally required by a conventional vector controller for an LCL-filter-based single-phase grid-connected converter and, therefore, can overcome the inefficiency problem caused by damping policies.
Rotation speed measurement for turbine governor: torsion filtering by using Kalman filter
International Nuclear Information System (INIS)
Houry, M.P.; Bourles, H.
1996-01-01
The rotation speed of a turbogenerator is disturbed by its shaft torsion. Obtaining a filtered measure of this speed is a problem of a great practical importance for turbine governor. A good filtering of this speed must meet two requirements: it must cut frequencies of the shaft torsion oscillation and it must not reduce or delay the signal in the pass-band, i.e. at lower frequencies. At Electricite de France, the speed measure is used to set in motion the fast valving system as quickly as possible, after a short circuit close to the unit or rather an islanding. It is difficult to satisfy these two requirements by using conventional filtering methods. The standard solution consists in a first order filter: at Electricite de France, its time constant is equal to 80 ms. We have decided to improve this filtering by designing a new filter which cuts the frequencies of the shaft torsion oscillation without reducing the bandwidth to the speed measure. If one uses conventional methods to obtain a band stop filter, it is easy to obtain the desired magnitude but not a phase near zero in the whole pass-band. Therefore, we have chosen to design the filter by using Kalman'a theory. The measurement noise is modeled as a colored one, generated by a very lightly damped system driven by a while noise. The resulting Kalman filter is an effective band stop filter, whose phase nicely remains near zero in the whole pass-band. The digital simulations we made and the tests we carried out with the Electricite de France Micro Network laboratory show the advantages of the rotation speed filter we designed using Kalman's theory. With the proposed filter, the speed measure filtering is better in terms of reduction and phase shift. the result is that there are less untimely solicitations of the fast valving system. Consequently, this device improves the power systems stability by minimizing the risks of deep perturbations due to a temporary lack of generation and the risks of under-speed loss
Microwave monolithic filter and phase shifter using magnetic nanostructures
Aslam, Shehreen; Khanna, Manoj; Veenugopal, Veerakumar; Kuanr, Bijoy K.
2018-05-01
Monolithic Microwave Integrated Circuit (MMIC) have major impact on the development of microwave communication technology. Transition metal based ferromagnetic nano-wired (FMNWs) substrate are of special interest in order to fabricate these MMIC devices. Their saturation magnetization is comparatively higher than ferrites which makes them suitable for high frequency (>10 ˜ 40 GHz) operation at zero or a small applied magnetic field. The CoFeB nanowires in anodic alumina templates were synthesized using three-electrode electro-deposition system. After electro-deposition, 1μm thick Cu layer was sputtered on the top surface of FMNW substrate and lithography was done to design microstrip lines. These microstrip transmission lines were tested for band-stop filters and phase shifters based on ferromagnetic resonance (FMR) over a wide applied magnetic field (H) range. It was observed that attenuation and frequency increase with the increase of magnetic field (upto 5.3 kOe). For phase shifter, the influence of magnetic material was studied for two frequency regions: (i) below FMR and (ii) above FMR. These two frequency regions were suitable for many practical device applications as the insertion loss was very less in these regions in comparison to resonance frequency regions. In the high frequency region (at 35 GHz), the optimal differential phase shift increased significantly to ˜ 250 deg/cm and around low frequency region (at 24 GHz), the optimal differential phase shift is ˜175 deg/cm at the highest field (H) value.
Microwave monolithic filter and phase shifter using magnetic nanostructures
Directory of Open Access Journals (Sweden)
Shehreen Aslam
2018-05-01
Full Text Available Monolithic Microwave Integrated Circuit (MMIC have major impact on the development of microwave communication technology. Transition metal based ferromagnetic nano-wired (FMNWs substrate are of special interest in order to fabricate these MMIC devices. Their saturation magnetization is comparatively higher than ferrites which makes them suitable for high frequency (>10 ∼ 40 GHz operation at zero or a small applied magnetic field. The CoFeB nanowires in anodic alumina templates were synthesized using three-electrode electro-deposition system. After electro-deposition, 1μm thick Cu layer was sputtered on the top surface of FMNW substrate and lithography was done to design microstrip lines. These microstrip transmission lines were tested for band-stop filters and phase shifters based on ferromagnetic resonance (FMR over a wide applied magnetic field (H range. It was observed that attenuation and frequency increase with the increase of magnetic field (upto 5.3 kOe. For phase shifter, the influence of magnetic material was studied for two frequency regions: (i below FMR and (ii above FMR. These two frequency regions were suitable for many practical device applications as the insertion loss was very less in these regions in comparison to resonance frequency regions. In the high frequency region (at 35 GHz, the optimal differential phase shift increased significantly to ∼ 250 deg/cm and around low frequency region (at 24 GHz, the optimal differential phase shift is ∼175 deg/cm at the highest field (H value.
Pupil filter design by using a Bessel functions basis at the image plane.
Canales, Vidal F; Cagigal, Manuel P
2006-10-30
Many applications can benefit from the use of pupil filters for controlling the light intensity distribution near the focus of an optical system. Most of the design methods for such filters are based on a second-order expansion of the Point Spread Function (PSF). Here, we present a new procedure for designing radially-symmetric pupil filters. It is more precise than previous procedures as it considers the exact expression of the PSF, expanded as a function of first-order Bessel functions. Furthermore, this new method presents other advantages: the height of the side lobes can be easily controlled, it allows the design of amplitude-only, phase-only or hybrid filters, and the coefficients of the PSF expansion can be directly related to filter parameters. Finally, our procedure allows the design of filters with very different behaviours and optimal performance.
International Nuclear Information System (INIS)
Švanda, Michal
2013-01-01
The consistency of time-distance inversions for horizontal components of the plasma flow on supergranular scales in the upper solar convection zone is checked by comparing the results derived using two k-ω filtering procedures—ridge filtering and phase-speed filtering—commonly used in time-distance helioseismology. I show that both approaches result in similar flow estimates when finite-frequency sensitivity kernels are used. I further demonstrate that the performance of the inversion improves (in terms of a simultaneously better averaging kernel and a lower noise level) when the two approaches are combined together in one inversion. Using the combined inversion, I invert for horizontal flows in the upper 10 Mm of the solar convection zone. The flows connected with supergranulation seem to be coherent only for the top ∼5 Mm; deeper down there is a hint of change of the convection scales toward structures larger than supergranules
Analytical Design of Passive LCL Filter for Three-phase Two-level Power Factor Correction Rectifiers
DEFF Research Database (Denmark)
Kouchaki, Alireza; Nymand, Morten
2017-01-01
This paper proposes a comprehensive analytical LCL filter design method for three-phase two-level power factor correction rectifiers (PFCs). The high frequency converter current ripple generates the high frequency current harmonics that need to be attenuated with respect to the grid standards...
Super-resolution pupil filtering for visual performance enhancement using adaptive optics
Zhao, Lina; Dai, Yun; Zhao, Junlei; Zhou, Xiaojun
2018-05-01
Ocular aberration correction can significantly improve visual function of the human eye. However, even under ideal aberration correction conditions, pupil diffraction restricts the resolution of retinal images. Pupil filtering is a simple super-resolution (SR) method that can overcome this diffraction barrier. In this study, a 145-element piezoelectric deformable mirror was used as a pupil phase filter because of its programmability and high fitting accuracy. Continuous phase-only filters were designed based on Zernike polynomial series and fitted through closed-loop adaptive optics. SR results were validated using double-pass point spread function images. Contrast sensitivity was further assessed to verify the SR effect on visual function. An F-test was conducted for nested models to statistically compare different CSFs. These results indicated CSFs for the proposed SR filter were significantly higher than the diffraction correction (p vision optical correction of the human eye.
DEFF Research Database (Denmark)
Kouchaki, Alireza; Nymand, Morten
2016-01-01
This paper presents LCL filter design method for three-phase two-level power factor correction (PFC) using line impedance stabilization network (LISN). A straightforward LCL filter design along with variation in grid impedance is not simply achievable and inevitably lead to an iterative solution...... for filter. By introducing of fast power switches for PFC applications such as silicon-carbide, major current harmonics around the switching frequency drops in the region that LISN can actively provide well-defined impedance for measuring the harmonics (i.e. 9 kHz- 30MHz). Therefore, LISN can be replaced...... is derived using the current ripple behavior of converter-side inductor. The grid-side inductor is achieved as a function of LISN impedance to fulfill the grid regulation. To verify the analyses, an LCL filter is designed for a 5 kW SiC-based PFC. The simulation and experimental results support the validity...
Methodology for modeling the microbial contamination of air filters.
Joe, Yun Haeng; Yoon, Ki Young; Hwang, Jungho
2014-01-01
In this paper, we propose a theoretical model to simulate microbial growth on contaminated air filters and entrainment of bioaerosols from the filters to an indoor environment. Air filter filtration and antimicrobial efficiencies, and effects of dust particles on these efficiencies, were evaluated. The number of bioaerosols downstream of the filter could be characterized according to three phases: initial, transitional, and stationary. In the initial phase, the number was determined by filtration efficiency, the concentration of dust particles entering the filter, and the flow rate. During the transitional phase, the number of bioaerosols gradually increased up to the stationary phase, at which point no further increase was observed. The antimicrobial efficiency and flow rate were the dominant parameters affecting the number of bioaerosols downstream of the filter in the transitional and stationary phase, respectively. It was found that the nutrient fraction of dust particles entering the filter caused a significant change in the number of bioaerosols in both the transitional and stationary phases. The proposed model would be a solution for predicting the air filter life cycle in terms of microbiological activity by simulating the microbial contamination of the filter.
Methodology for modeling the microbial contamination of air filters.
Directory of Open Access Journals (Sweden)
Yun Haeng Joe
Full Text Available In this paper, we propose a theoretical model to simulate microbial growth on contaminated air filters and entrainment of bioaerosols from the filters to an indoor environment. Air filter filtration and antimicrobial efficiencies, and effects of dust particles on these efficiencies, were evaluated. The number of bioaerosols downstream of the filter could be characterized according to three phases: initial, transitional, and stationary. In the initial phase, the number was determined by filtration efficiency, the concentration of dust particles entering the filter, and the flow rate. During the transitional phase, the number of bioaerosols gradually increased up to the stationary phase, at which point no further increase was observed. The antimicrobial efficiency and flow rate were the dominant parameters affecting the number of bioaerosols downstream of the filter in the transitional and stationary phase, respectively. It was found that the nutrient fraction of dust particles entering the filter caused a significant change in the number of bioaerosols in both the transitional and stationary phases. The proposed model would be a solution for predicting the air filter life cycle in terms of microbiological activity by simulating the microbial contamination of the filter.
Analog and digital filtering of the brain stem auditory evoked response.
Kavanagh, K T; Franks, R
1989-07-01
This study compared the filtering effects on the auditory evoked potential of zero and standard phase shift digital filters (the former was a mathematical approximation of a standard Butterworth filter). Conventional filters were found to decrease the height of the evoked response in the majority of waveforms compared to zero phase shift filters. A 36-dB/octave zero phase shift high pass filter with a cutoff frequency of 100 Hz produced a 16% reduction in wave amplitude compared to the unfiltered control. A 36-dB/octave, 100-Hz standard phase shift high pass filter produced a 41% reduction, and a 12-dB/octave, 150-Hz standard phase shift high pass filter produced a 38% reduction in wave amplitude compared to the unfiltered control. A decrease in the mean along with an increase in the variability of wave IV/V latency was also noted with conventional compared to zero phase shift filters. The increase in the variability of the latency measurement was due to the difficulty in waveform identification caused by the phase shift distortion of the conventional filter along with the variable decrease in wave latency caused by phase shifting responses with different spectral content. Our results indicated that a zero phase shift high pass filter of 100 Hz was the most desirable filter studied for the mitigation of spontaneous brain activity and random muscle artifact.
Bush, Craig R.
This dissertation presents a novel current source converter topology that is primarily intended for single-phase photovoltaic (PV) applications. In comparison with the existing PV inverter technology, the salient features of the proposed topology are: a) the low frequency (double of line frequency) ripple that is common to single-phase inverters is greatly reduced; b) the absence of low frequency ripple enables significantly reduced size pass components to achieve necessary DC-link stiffness and c) improved maximum power point tracking (MPPT) performance is readily achieved due to the tightened current ripple even with reduced-size passive components. The proposed topology does not utilize any electrolytic capacitors. Instead an inductor is used as the DC-link filter and reliable AC film capacitors are utilized for the filter and auxiliary capacitor. The proposed topology has a life expectancy on par with PV panels. The proposed modulation technique can be used for any current source inverter where an unbalanced three-phase operation is desires such as active filters and power controllers. The proposed topology is ready for the next phase of microgrid and power system controllers in that it accepts reactive power commands. This work presents the proposed topology and its working principle supported by with numerical verifications and hardware results. Conclusions and future work are also presented.
Energy Technology Data Exchange (ETDEWEB)
Poure, P. [Laboratoire d' Instrumentation Electronique de Nancy LIEN, EA 3440, Nancy-Universite, Faculte des Sciences et Techniques, BP 239, 54506 Vandoeuvre Cedex (France); Weber, P.; Theilliol, D. [Centre de Recherche en Automatique de Nancy UMR 7039, Nancy-Universite, CNRS, Faculte des Sciences et Techniques, BP 239, 54506 Vandoeuvre Cedex (France); Saadate, S. [Groupe de Recherches en Electrotechnique et Electronique de Nancy UMR 7037, Nancy-Universite, CNRS, Faculte des Sciences et Techniques, BP 239, 54506 Vandoeuvre Cedex (France)
2009-02-15
This paper deals with fault tolerant shunt three-phase three-wire active filter topologies for which reliability is very important in industry applications. The determination of the optimal reconfiguration structure among various ones with or without redundant components is discussed based on reliability criteria. First, the reconfiguration of the inverter is detailed and a fast fault diagnosis method for power semi-conductor or driver fault detection and compensation is presented. This method avoids false fault detection due to power semi-conductors switching. The control architecture and algorithm are studied and a fault tolerant control strategy is considered. Simulation results in open and short circuit cases validate the theoretical study. Finally, the reliability of the studied three-phase three-wire filter shunt active topologies is analyzed to determine the optimal one. (author)
DEFF Research Database (Denmark)
Luo, Zhaoxu; Su, Mei; Yang, Jian
2016-01-01
these disadvantages, many repetitive controllers with reduced delay time have been proposed, which can selectively compensate the odd harmonics or 6k±1 harmonics with delay time reduced to T0/2 and T0/3,repectively. To further study in this area, this paper proposes an improved repetitive scheme implemented...... in stationary reference frame, which only compensates the 6k+1 harmonics (e.g. -5, +7, -11, +13) in three-phase systems and reduces the time delay to T0/6 . So compared with the earlier reduced delay time repetitive controllers, the robustness and transient performance is further improved, the waste of control...... effort is reduced, and the possibility of amplifying and even injecting any harmonic noises into system is avoided to the greatest extent. Moreover, the proposed repetitive scheme is used in the control of a three-phase hybrid active power filter. The experimental results validate the effectiveness...
Extended Kalman filtering for joint mitigation of phase and amplitude noise in coherent QAM systems.
Pakala, Lalitha; Schmauss, Bernhard
2016-03-21
We numerically investigate our proposed carrier phase and amplitude noise estimation (CPANE) algorithm using extend Kalman filter (EKF) for joint mitigation of linear and non-linear phase noise as well as amplitude noise on 4, 16 and 64 polarization multiplexed (PM) quadrature amplitude modulation (QAM) 224 Gb/s systems. The results are compared to decision directed (DD) carrier phase estimation (CPE), DD phase locked loop (PLL) and universal CPE (U-CPE) algorithms. Besides eliminating the necessity of phase unwrapping function, EKF-CPANE shows improved performance for both back-to-back (BTB) and transmission scenarios compared to the aforementioned algorithms. We further propose a weighted innovation approach (WIA) of the EKF-CPANE which gives an improvement of 0.3 dB in the Q-factor, compared to the original algorithm.
International Nuclear Information System (INIS)
Xue Dahai
2005-01-01
Qinshan phase 3 nuclear power plant is the first CANDU plant that China fetched in from Canada, and both two units operate under well condition up to now. The radioactive wastes produced during the unit operation mainly include technical waste, spent resin, and spent filter cartridge. The spent filter cartridge is one important part both in the volume and radioactivity of the radioactive waste, and it is the important content of radioactive waste management. Different from PWR, part of high radioactive spent filter in CANDU unit comes from heavy water system such as moderator system. It has to be dried through blowing before replaced from the system. But this working procedure result the filtrate dreg become flexible, and it can bring on the risk of internal or external exposure. It is very important to pay high attention to control the contamination spread during spent filter inside transfer. (authors)
Prarokijjak, Worasak; Soodchomshom, Bumned
2018-04-01
Spin-valley transport and magnetoresistance are investigated in silicene-based N/TB/N/TB/N junction where N and TB are normal silicene and topological barriers. The topological phase transitions in TB's are controlled by electric, exchange fields and circularly polarized light. As a result, we find that by applying electric and exchange fields, four groups of spin-valley currents are perfectly filtered, directly induced by topological phase transitions. Control of currents, carried by single, double and triple channels of spin-valley electrons in silicene junction, may be achievable by adjusting magnitudes of electric, exchange fields and circularly polarized light. We may identify that the key factor behind the spin-valley current filtered at the transition points may be due to zero and non-zero Chern numbers. Electrons that are allowed to transport at the transition points must obey zero-Chern number which is equivalent to zero mass and zero-Berry's curvature, while electrons with non-zero Chern number are perfectly suppressed. Very large magnetoresistance dips are found directly induced by topological phase transition points. Our study also discusses the effect of spin-valley dependent Hall conductivity at the transition points on ballistic transport and reveals the potential of silicene as a topological material for spin-valleytronics.
Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming
Bañas, Andrew Rafael; Palima, Darwin; Glückstad, Jesper
2012-01-01
We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as...
Rotation speed measurement for turbine governor: torsion filtering by using Kalman filter
International Nuclear Information System (INIS)
Houry, M.P.; Bourles, H.
1995-11-01
The rotation speed of a turbogenerator is disturbed by its shaft torsion. Obtaining a filtered measure of this sped a problem of a great practical importance for turbine governor. A good filtering of this speed must meet two requirements: it must cut frequencies of the shaft torsion oscillation and it must not reduce or delay the signal in the pass-band. i.e. at lower frequencies. At Electricite de France, the speed measure is used to set in motion the fast valving system as quickly as possible, after a short circuit close to the unit (to contribute to the stability) or after an islanding (to quickly reach a balance with the house load). It is difficult to satisfy these two requirements by using conventional filtering methods. The standard solution consists in a first order filter: at Electricite de France, its time constant is equal to 80 ms; We have decided to improve this filtering by designing a new filter which cuts the frequencies of the shaft torsion oscillation without reducing the bandwidth of the speed measure. If one uses conventional methods to obtain a band-stop filter (for instance a Butterworth, a Chebyshev or an elliptic band-stop filter),it is easy to obtain the desired magnitude but not a phase near zero in the whole pass-band. Therefore, we have chosen to design the filter by using Kalman's theory. The measurement noise is modeled as a colored one, generated by a very lightly damped system driven by a white noise. The resulting Kalman filter is an effective band-stop filter, whose phase nicely remains near zero in the whole pass-band. (authors). 13 refs., 12 figs
Genetic Algorithm-Based Design of the Active Damping for an LCL-Filter Three-Phase Active Rectifier
DEFF Research Database (Denmark)
Liserre, Marco; Aquila, Antonio Dell; Blaabjerg, Frede
2004-01-01
Active rectifiers/inverters are becoming used more and more often in regenerative systems and distributed power systems. Typically, the interface between the grid and rectifier is either an inductor or an LCL-filter. The use of an LCL-filter mitigates the switching ripple injected in the grid...... by a three-phase active rectifier. However, stability problems can arise in the current control loop. In order to overcome them, a damping resistor can be inserted, at the price of a reduction of efficiency. The use of active damping by means of control may seem attractive, but it is often limited by the use...
Duijster, Arno; van Groenestijn, Gert-Jan; van Neer, Paul; Blacquière, Gerrit; Volker, Arno
2018-04-01
The use of phased arrays is growing in the non-destructive testing industry and the trend is towards large 2D arrays, but due to limitations, it is currently not possible to record the signals from all elements, resulting in aliased data. In the past, we have presented a data interpolation scheme `beyond spatial aliasing' to overcome this aliasing. In this paper, we present a different approach: blending and deblending of data. On the hardware side, groups of receivers are blended (grouped) in only a few transmit/recording channels. This allows for transmission and recording with all elements, in a shorter acquisition time and with less channels. On the data processing side, this blended data is deblended (separated) by transforming it to a different domain and applying an iterative filtering and thresholding. Two different filtering methods are compared: f-k filtering and wavefield extrapolation filtering. The deblending and filtering methods are demonstrated on simulated experimental data. The wavefield extrapolation filtering proves to outperform f-k filtering. The wavefield extrapolation method can deal with groups of up to 24 receivers, in a phased array of 48 × 48 elements.
Preliminary feasibility and cost analysis of the in-situ microbial filter concept
International Nuclear Information System (INIS)
Wijensinghe, A.M.; Knapp, R.B.; Taylor, R.T.; Carman, L.M.
1992-01-01
In this report the cost of installing and operating an in-situ microbial filter to remediate a site at which the groundwater is contaminated by TCE is estimated and compared against the cost of remediation by a standard pump and treat method. In this microbial filter method, relatively thin vertical filters are installed in the subsurface to intercept contaminant plumes that are being transported by the flowing groundwater. The filters are created by injecting into the subsurface methanotrophic microbes grown in surface bioreactors and allowing them to become attached to the soil. The microbes produce an enzyme (MMO) that fortuitously catalyzes the degradation of TCE into carbon dioxide, water and chloride ions. Because no external energy or carbon source is provided, the microbes remain metabolically active only for a limited time so that the filter needs to be periodically replenished with fresh microbes. Two methods of establishing and maintaining the microbial filter using either vertical or horizontal wells were studied. In the pump and treat method considered for comparison, the groundwater pumped to the surface is first subjected to air-stripping of the liquid-phase volatile organic compound (i.e., VOC) from the groundwater followed by adsorption of the heated vapor-phase VOC by granular activated carbon (i.e., GAC) within a packed-bed filter
Directory of Open Access Journals (Sweden)
Manish Gupta
2017-01-01
Full Text Available The manuscript presents a circuit that can act as a universal filter as well as a single resistence controlled oscillator by unpretentiously changing the switch positions. The circuit employs only two active devices and all grounded passive elements. The utilization of only grounded passive components makes this circuit a better choice for integrated circuit implementation. The current mode biquadratic filter offers all the five basic responses along with independent tunability of its quality factor. The dual-mode quadrature sinusoidal oscillator offers explicit current outputs along with voltage outputs. The circuit also offers a simple and uncoupled condition of oscillation and frequency of oscillation. The typical analysis such as non-ideal, sensitivity and parasitic analysis along with the regular simulation results as well as experimental results are exposed here, to strengthen the design idea.
Phase-only asymmetric optical cryptosystem based on random modulus decomposition
Xu, Hongfeng; Xu, Wenhui; Wang, Shuaihua; Wu, Shaofan
2018-06-01
We propose a phase-only asymmetric optical cryptosystem based on random modulus decomposition (RMD). The cryptosystem is presented for effectively improving the capacity to resist various attacks, including the attack of iterative algorithms. On the one hand, RMD and phase encoding are combined to remove the constraints that can be used in the attacking process. On the other hand, the security keys (geometrical parameters) introduced by Fresnel transform can increase the key variety and enlarge the key space simultaneously. Numerical simulation results demonstrate the strong feasibility, security and robustness of the proposed cryptosystem. This cryptosystem will open up many new opportunities in the application fields of optical encryption and authentication.
Advanced nonlinear control of three phase series active power filter
Directory of Open Access Journals (Sweden)
Abouelmahjoub Y.
2014-01-01
Full Text Available The problem of controlling three-phase series active power filter (TPSAPF is addressed in this paper in presence of the perturbations in the voltages of the electrical supply network. The control objective of the TPSAPF is twofold: (i compensation of all voltage perturbations (voltage harmonics, voltage unbalance and voltage sags, (ii regulation of the DC bus voltage of the inverter. A controller formed by two nonlinear regulators is designed, using the Backstepping technique, to provide the above compensation. The regulation of the DC bus voltage of the inverter is ensured by the use of a diode bridge rectifier which its output is in parallel with the DC bus capacitor. The Analysis of controller performances is illustrated by numerical simulation in Matlab/Simulink environment.
Nanofiber Filters Eliminate Contaminants
2009-01-01
With support from Phase I and II SBIR funding from Johnson Space Center, Argonide Corporation of Sanford, Florida tested and developed its proprietary nanofiber water filter media. Capable of removing more than 99.99 percent of dangerous particles like bacteria, viruses, and parasites, the media was incorporated into the company's commercial NanoCeram water filter, an inductee into the Space Foundation's Space Technology Hall of Fame. In addition to its drinking water filters, Argonide now produces large-scale nanofiber filters used as part of the reverse osmosis process for industrial water purification.
Control of a three-phase four-wire shunt-active power filter based on DC-bus energy regulation
DEFF Research Database (Denmark)
Blaabjerg, Frede; Teodorescu, Remus; Rodriguez, Pedro
2008-01-01
This paper presents a nonconventional three-phase four-wire shunt active power filter (APF) topology controlled by using an energy approach. A general study of power terms involved in the operation of the four-wire APF is conducted in order to evidence the relationship between instantaneous energy...... stored in the DC bus and active power requirements on the APF. Harmonics and imbalances both on the utility voltage and load current have been considered and the power developed by the active power filter has been evaluated. This study allows designing a controller for the APF based on the regulation...
DEFF Research Database (Denmark)
Bañas, Andrew Rafael; Aabo, Thomas; Palima, Darwin
2013-01-01
as a combination of Generalized Phase Contrast and phase-only correlation. Such an analysis makes it convenient to optimize an mGPC system for different setup conditions. Results showing binary-only phase generation of dynamic spot arrays and line patterns are presented. © 201 Optical Society of America...
DEFF Research Database (Denmark)
Blaabjerg, Frede; Chiarantoni, Ernesto; Aquila, Antonio Dell
2004-01-01
Three-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue......, to the grid side stiffness and to the parameters of the controller has never been detailed considered. In this paper the experimental results of an LCL-filter-based three-phase active rectifier are analysed with the circuit theory approach. A ?virtual circuit? is synthesized in role of the digital controller...
National Aeronautics and Space Administration — In Phase II of this SBIR, Harmonic Devices (HDI) proposes to develop miniaturized MEMS filters at UHF, S-band and Ka-band to address the requirements of NASA's...
International Nuclear Information System (INIS)
Berberova, Natalia; Stoykova, Elena; Sainov, Ventseslav
2012-01-01
A variety of pattern projection methods for the three-dimensional capture of objects is based on the generation of purely sinusoidal fringes. This is not an easy task, especially when a portable non-interferometric system for outdoor usage is required. The use of phase gratings with coherent illumination as a possible solution has the advantage of providing good stability and a large measurement volume. In this work, we analyze the quality of fringes projected with two sinusoidal phase gratings. The first grating is recorded on a silver-halide holographic plate by means of a Michelson interferometer. The spatial resolution of the silver-halide material used is greater than 6000 lines per millimeter, and the recorded grating is practically analogous to a smooth variation of the phase profile. The second grating is formed as a sinusoidal phase variation on a liquid crystal-on-silicon phase-only reflective display with a resolution of 1920×1080 pixels, a pixel pitch of 8 μm and 256 phase levels. The frequency content of the fringes projected with both gratings is analyzed and compared on the basis of the calculated Fresnel diffraction pattern, taking into account that the sinusoidal phase distribution in the case of a spatial light modulator is both sampled and quantized. Experimental fringe patterns projected using both gratings are also provided.
A new greedy search method for the design of digital IIR filter
Directory of Open Access Journals (Sweden)
Ranjit Kaur
2015-07-01
Full Text Available A new greedy search method is applied in this paper to design the optimal digital infinite impulse response (IIR filter. The greedy search method is based on binary successive approximation (BSA and evolutionary search (ES. The suggested greedy search method optimizes the magnitude response and the phase response simultaneously and also finds the lowest order of the filter. The order of the filter is controlled by a control gene whose value is also optimized along with the filter coefficients to obtain optimum order of designed IIR filter. The stability constraints of IIR filter are taken care of during the design procedure. To determine the trade-off relationship between conflicting objectives in the non-inferior domain, the weighting method is exploited. The proposed approach is effectively applied to solve the multiobjective optimization problems of designing the digital low-pass (LP, high-pass (HP, bandpass (BP, and bandstop (BS filters. It has been demonstrated that this technique not only fulfills all types of filter performance requirements, but also the lowest order of the filter can be found. The computational experiments show that the proposed approach gives better digital IIR filters than the existing evolutionary algorithm (EA based methods.
Energy Technology Data Exchange (ETDEWEB)
Kilic, Tomislav; Milun, Stanko; Petrovic, Goran [FESB University of Split, Faculty of Electrical Engineering, Machine Engineering and Naval Architecture, R. Boskovica bb, 21000, Split (Croatia)
2007-02-15
The shunt active power filters are used to attenuate the harmonic currents in power systems by injecting equal but opposite compensating currents. Successful control of the active filters requires an accurate current reference. In this paper the current reference determination based on predictive filtering structure is presented. Current reference was obtained by taking the difference of load current and its fundamental harmonic. For fundamental harmonic determination with no time delay a combination of digital predictive filter and low pass filter is used. The proposed method was implemented on a laboratory prototype of a three-phase active power filter. The algorithm for current reference determination was adapted and implemented on DSP controller. Simulation and experimental results show that the active power filter with implemented predictive filtering structure gives satisfactory performance in power system harmonic attenuation. (author)
Controlling flow conditions of test filters in iodine filters
International Nuclear Information System (INIS)
Holmberg, R.; Laine, J.
1979-03-01
Several different iodine filter and test filter designs and experience gained from their operation are presented. For the flow experiments, an iodine filter system equipped with flow regulating and measuring devices was built. In the experiments the influence of the packing method of the iodine sorption material and the influence of the flow regulating and measuring divices upon the flow conditions in the test filters was studied. On the basis of the experiments it has been shown that the flows through the test filters always can be adjusted to a correct value if there only is a high enough pressure difference available across the test filter ducting. As a result of the research, several different methods are presented with which the flows through the test filters in both operating and future iodine sorption system can easily be measured and adjusted to their correct values. (author)
Phase Coordinate System and p-q Theory Based Methods in Active Filtering Implementation
Directory of Open Access Journals (Sweden)
POPESCU, M.
2013-02-01
Full Text Available This paper is oriented towards implementation of the main theories of powers in the compensating current generation stage of a three-phase three-wire shunt active power system. The system control is achieved through a dSPACE 1103 platform which is programmed under the Matlab/Simulink environment. Four calculation blocks included in a specifically designed Simulink library are successively implemented in the experimental setup. The first two approaches, namely those based on the Fryze-Buchholz-Depenbrock theory and the generalized instantaneous reactive power theory, make use of phase quantities without any transformation of the coordinate system and provide the basis for calculating the compensating current when total compensation is desired. The others are based on the p-q theory concepts and require the direct and reverse transformation to/from the two-phases stationary reference frame. They are used for total compensation and partial compensation of the current harmonic distortion. The experimental results, in terms of active filtering performances, validate the control strategies implementation and provide arguments in choosing the most appropriate method.
DEFF Research Database (Denmark)
Pena-Alzola, Rafael; Liserre, Marco; Blaabjerg, Frede
2014-01-01
LCL-filters are a cost-effective solution to mitigate harmonic current content in grid-tie converters. In order to avoid stability problems, the resonance frequency of LCL-filters can be damped with active techniques that remove dissipative elements but increase control complexity. A notch filter...
Phase-only SLM Generating Variable Patterns Applied in Optical Connection
International Nuclear Information System (INIS)
Liu, B H; Wu, L Y; Zhang, J
2006-01-01
An adaptive optical communication system is proposed. The system sends spatial information by emitting multiple variable laser beams generated from a programmable diffractive optical element (DOE): phase-only liquid crystal Spatial Light Modulator (SLM). Laser beams carrying signals are programmable by an optimal algorithm based on an iterative Fourier transformation algorithm. The system has the advantage in redundancy of signal by the means of broadcast. It can adaptively seek position and transmit information in parallel
High Performance Miniature Bandpass Filters, Phase I
National Aeronautics and Space Administration — This proposal is submitted for developing low impedance, miniature bandpass RF frequency filter via MEMS technique, in applications of SMAP, Aquarius follow-on,...
Directory of Open Access Journals (Sweden)
Wei Xu
2018-05-01
Full Text Available Cosine-modulated filter banks play a major role in digital signal processing. Sparse FIR filter banks have lower implementation complexity than full filter banks, while keeping a good performance level. This paper presents a fast design paradigm for sparse nearly perfect-reconstruction (NPR cosine-modulated filter banks. First, an approximation function is introduced to reduce the non-convex quadratically constrained optimization problem to a linearly constrained optimization problem. Then, the desired sparse linear phase FIR prototype filter is derived through the orthogonal matching pursuit (OMP performed under the weighted l 2 norm. The simulation results demonstrate that the proposed scheme is an effective paradigm to design sparse NPR cosine-modulated filter banks.
LLCL-Filter Based Single-Phase Grid-Tied Aalborg Inverter
DEFF Research Database (Denmark)
Wu, Weimin; Feng, Shuangshuang; Ji, Junhao
2014-01-01
The Aalborg Inverter is a new type of high efficient DC/AC grid-tied inverter, where the input DC voltage can vary in a wide range. Compared with the LCL-filter, the LLCL-filter can save the total inductance for the conventional voltage source inverter. In this paper, an LLCL-filter based Aalborg...... Inverter is proposed and its character is illustrated through the small signal analysis in both “Buck” and “Buck-Boost” mode. From the modeling, it can be seen that the resonant inductor in the capacitor loop has not brought extra control difficulties, whereas more inductance in the power loop can be saved...
Filtering apparatus and method for mixing, extraction and/or separation
DEFF Research Database (Denmark)
2013-01-01
The present invention relates to a filtering apparatus and method for mixing a compound of solid and fluid phases, separating the phases and/or extracting fluid from the compound. One embodiment of the invention discloses a filtering apparatus comprising a first filter section accommodating a fir...... in a beer brewing procedure....
Generalized design of high performance shunt active power filter with output LCL filter
DEFF Research Database (Denmark)
Tang, Yi; Loh, Poh Chiang; Wang, Peng
2012-01-01
parameters, interactions between resonance damping and harmonic compensation, bandwidth design of the closed-loop system, and active damping implementation with fewer current sensors. These described design concerns, together with their generalized design procedure, are applied to an analytical example......This paper concentrates on the design, control, and implementation of an LCL-filter-based shunt active power filter (SAPF), which can effectively compensate for harmonic currents produced by nonlinear loads in a three-phase three-wire power system. With an LCL filter added at its output...
A multi-standard active-RC filter with accurate tuning system
International Nuclear Information System (INIS)
Ma Heping; Yuan Fang; Shi Yin; Dai, F F
2009-01-01
A low-power, highly linear, multi-standard, active-RC filter with an accurate and novel tuning architecture is presented. It exhibits IEEE 802.11 a/b/g (9.5 MHz) and DVB-H (3 MHz, 4 MHz) application. The filter exploits digitally-controlled polysilicon resistor banks and a phase lock loop type automatic tuning system. The novel and complex automatic frequency calibration scheme provides better than 4 corner frequency accuracy, and it can be powered down after calibration to save power and avoid digital signal interference. The filter achieves OIP3 of 26 dBm and the measured group delay variation of the receiver filter is 50 ns (WLAN mode). Its dissipation is 3.4 mA in RX mode and 2.3 mA (only for one path) in TX mode from a 2.85 V supply. The dissipation of calibration consumes 2 mA. The circuit has been fabricated in a 0.35 μm 47 GHz SiGe BiCMOS technology; the receiver and transmitter filter occupy 0.21 mm 2 and 0.11 mm 2 (calibration circuit excluded), respectively.
Gait Phase Recognition for Lower-Limb Exoskeleton with Only Joint Angular Sensors
Directory of Open Access Journals (Sweden)
Du-Xin Liu
2016-09-01
Full Text Available Gait phase is widely used for gait trajectory generation, gait control and gait evaluation on lower-limb exoskeletons. So far, a variety of methods have been developed to identify the gait phase for lower-limb exoskeletons. Angular sensors on lower-limb exoskeletons are essential for joint closed-loop controlling; however, other types of sensors, such as plantar pressure, attitude or inertial measurement unit, are not indispensable.Therefore, to make full use of existing sensors, we propose a novel gait phase recognition method for lower-limb exoskeletons using only joint angular sensors. The method consists of two procedures. Firstly, the gait deviation distances during walking are calculated and classified by Fisher’s linear discriminant method, and one gait cycle is divided into eight gait phases. The validity of the classification results is also verified based on large gait samples. Secondly, we build a gait phase recognition model based on multilayer perceptron and train it with the phase-labeled gait data. The experimental result of cross-validation shows that the model has a 94.45% average correct rate of set (CRS and an 87.22% average correct rate of phase (CRP on the testing set, and it can predict the gait phase accurately. The novel method avoids installing additional sensors on the exoskeleton or human body and simplifies the sensory system of the lower-limb exoskeleton.
Gait Phase Recognition for Lower-Limb Exoskeleton with Only Joint Angular Sensors
Liu, Du-Xin; Wu, Xinyu; Du, Wenbin; Wang, Can; Xu, Tiantian
2016-01-01
Gait phase is widely used for gait trajectory generation, gait control and gait evaluation on lower-limb exoskeletons. So far, a variety of methods have been developed to identify the gait phase for lower-limb exoskeletons. Angular sensors on lower-limb exoskeletons are essential for joint closed-loop controlling; however, other types of sensors, such as plantar pressure, attitude or inertial measurement unit, are not indispensable.Therefore, to make full use of existing sensors, we propose a novel gait phase recognition method for lower-limb exoskeletons using only joint angular sensors. The method consists of two procedures. Firstly, the gait deviation distances during walking are calculated and classified by Fisher’s linear discriminant method, and one gait cycle is divided into eight gait phases. The validity of the classification results is also verified based on large gait samples. Secondly, we build a gait phase recognition model based on multilayer perceptron and train it with the phase-labeled gait data. The experimental result of cross-validation shows that the model has a 94.45% average correct rate of set (CRS) and an 87.22% average correct rate of phase (CRP) on the testing set, and it can predict the gait phase accurately. The novel method avoids installing additional sensors on the exoskeleton or human body and simplifies the sensory system of the lower-limb exoskeleton. PMID:27690023
Maximum likelihood estimation of the parameters of nonminimum phase and noncausal ARMA models
DEFF Research Database (Denmark)
Rasmussen, Klaus Bolding
1994-01-01
The well-known prediction-error-based maximum likelihood (PEML) method can only handle minimum phase ARMA models. This paper presents a new method known as the back-filtering-based maximum likelihood (BFML) method, which can handle nonminimum phase and noncausal ARMA models. The BFML method...... is identical to the PEML method in the case of a minimum phase ARMA model, and it turns out that the BFML method incorporates a noncausal ARMA filter with poles outside the unit circle for estimation of the parameters of a causal, nonminimum phase ARMA model...
Cermet materials, self-cleaning cermet filters, apparatus and systems employing same
Kong, Peter C.
2005-07-19
A self-cleaning porous cermet material, filter and system utilizing the same may be used in filtering particulate and gaseous pollutants from internal combustion engines having intermetallic and ceramic phases. The porous cermet filter may be made from a transition metal aluminide phase and an alumina phase. Filler materials may be added to increase the porosity or tailor the catalytic properties of the cermet material. Additionally, the cermet material may be reinforced with fibers or screens. The porous filter may also be electrically conductive so that a current may be passed therethrough to heat the filter during use. Further, a heating element may be incorporated into the porous cermet filter during manufacture. This heating element can be coated with a ceramic material to electrically insulate the heating element. An external heating element may also be provided to heat the cermet filter during use.
The intractable cigarette 'filter problem'.
Harris, Bradford
2011-05-01
When lung cancer fears emerged in the 1950s, cigarette companies initiated a shift in cigarette design from unfiltered to filtered cigarettes. Both the ineffectiveness of cigarette filters and the tobacco industry's misleading marketing of the benefits of filtered cigarettes have been well documented. However, during the 1950s and 1960s, American cigarette companies spent millions of dollars to solve what the industry identified as the 'filter problem'. These extensive filter research and development efforts suggest a phase of genuine optimism among cigarette designers that cigarette filters could be engineered to mitigate the health hazards of smoking. This paper explores the early history of cigarette filter research and development in order to elucidate why and when seemingly sincere filter engineering efforts devolved into manipulations in cigarette design to sustain cigarette marketing and mitigate consumers' concerns about the health consequences of smoking. Relevant word and phrase searches were conducted in the Legacy Tobacco Documents Library online database, Google Patents, and media and medical databases including ProQuest, JSTOR, Medline and PubMed. 13 tobacco industry documents were identified that track prominent developments involved in what the industry referred to as the 'filter problem'. These reveal a period of intense focus on the 'filter problem' that persisted from the mid-1950s to the mid-1960s, featuring collaborations between cigarette producers and large American chemical and textile companies to develop effective filters. In addition, the documents reveal how cigarette filter researchers' growing scientific knowledge of smoke chemistry led to increasing recognition that filters were unlikely to offer significant health protection. One of the primary concerns of cigarette producers was to design cigarette filters that could be economically incorporated into the massive scale of cigarette production. The synthetic plastic cellulose acetate
Optically secured information retrieval using two authenticated phase-only masks.
Wang, Xiaogang; Chen, Wen; Mei, Shengtao; Chen, Xudong
2015-10-23
We propose an algorithm for jointly designing two phase-only masks (POMs) that allow for the encryption and noise-free retrieval of triple images. The images required for optical retrieval are first stored in quick-response (QR) codes for noise-free retrieval and flexible readout. Two sparse POMs are respectively calculated from two different images used as references for authentication based on modified Gerchberg-Saxton algorithm (GSA) and pixel extraction, and are then used as support constraints in a modified double-phase retrieval algorithm (MPRA), together with the above-mentioned QR codes. No visible information about the target images or the reference images can be obtained from each of these authenticated POMs. This approach allows users to authenticate the two POMs used for image reconstruction without visual observation of the reference images. It also allows user to friendly access and readout with mobile devices.
International Nuclear Information System (INIS)
Lee, Jeong Seong; Malik, Nauman Muhammad; Khambampati, Anil Kumar; Rashid, Ahmar; Kim, Sin; Kim, Kyung Youn
2008-01-01
For the visualization of the phase distribution in two phase flows, the electrical resistance tomography (ERT) technique is introduced. In ERT, the internal resistivity distribution is reconstructed based on the known sets of the injected currents and measured voltages on the surface of the object. The physical relationship between the internal resistivity and the surface voltages is governed by a partial differential equation with appropriate boundary conditions. This paper considers the estimation of the phase distribution with ERT in two phase flow in a horizontal flow using extended Kalman filter. To evaluate the reconstruction performance of the proposed algorithm, the experiments simulated two phase flows in a horizontal flow were carried out. The experiments with two phase flow phantom were done to suggest a practical implication of this research in detecting gas bubble in a feed water pipe of heat transfer systems
Dynamic Phase Boundary Estimation in Two-phase Flows Based on Electrical Impedance Tomography
International Nuclear Information System (INIS)
Lee, Jeong Seong; Muhammada, Nauman Malik; Kim, Kyung Youn; Kim, Sin
2008-01-01
For the dynamic visualization of the phase boundary in two-phase flows, the electrical impedance tomography (EIT) technique is introduced. In EIT, a set of predetermined electrical currents is injected through the electrodes placed on the boundary of the flow passage and the induced electrical potentials are measured on the electrodes. With the relationship between the injected currents and the induced voltages, the electrical conductivity distribution across the flow domain is estimated through the image reconstruction algorithm where the conductivity distribution corresponds to the phase distribution. In the application of EIT to two-phase flows where there are only two conductivity values, the conductivity distribution estimation problem can be transformed into the boundary estimation problem. This paper considers phase boundary estimation with EIT in annular two-phase flows. As the image reconstruction algorithm, the unscented Kalman filter (UKF) is adopted since from the control theory it is reported that the UKF shows better performance than the extended Kalman filter (EKF) that has been commonly used. For the present problem, the formulation of UKF algorithm involved its incorporation in the adopted image reconstruction algorithm. Also, phantom experiments have been conducted to evaluate the improvement reported by UKF
Rodgers, John C.; McFarland, Andrew R.; Ortiz, Carlos A.
1995-01-01
A quick-change filter cartridge. In sampling systems for measurement of airborne materials, a filter element is introduced into the sampled airstream such that the aerosol constituents are removed and deposited on the filter. Fragile sampling media often require support in order to prevent rupture during sampling, and careful mounting and sealing to prevent misalignment, tearing, or creasing which would allow the sampled air to bypass the filter. Additionally, handling of filter elements may introduce cross-contamination or exposure of operators to toxic materials. Moreover, it is desirable to enable the preloading of filter media into quick-change cartridges in clean laboratory environments, thereby simplifying and expediting the filter-changing process in the field. The quick-change filter cartridge of the present invention permits the application of a variety of filter media in many types of instruments and may also be used in automated systems. The cartridge includes a base through which a vacuum can be applied to draw air through the filter medium which is located on a porous filter support and held there by means of a cap which forms an airtight seal with the base. The base is also adapted for receiving absorbing media so that both particulates and gas-phase samples may be trapped for investigation, the latter downstream of the aerosol filter.
Topology optimization of microwave waveguide filters
DEFF Research Database (Denmark)
Aage, Niels; Johansen, Villads Egede
2017-01-01
We present a density based topology optimization approach for the design of metallic microwave insert filters. A two-phase optimization procedure is proposed in which we, starting from a uniform design, first optimize to obtain a set of spectral varying resonators followed by a band gap optimizat......We present a density based topology optimization approach for the design of metallic microwave insert filters. A two-phase optimization procedure is proposed in which we, starting from a uniform design, first optimize to obtain a set of spectral varying resonators followed by a band gap...... little resemblance to standard filter layouts and hence the proposed design method offers a new design tool in microwave engineering....
A New Synchronous Reference Frame-Based Method for Single-Phase Shunt Active Power Filters
DEFF Research Database (Denmark)
Monfared, Mohammad; Golestan, Saeed; Guerrero, Josep M.
2013-01-01
This paper deals with the design of a novel method in the synchronous reference frame (SRF) to extract the reference compensating current for single-phase shunt active power filters (APFs). Unlike previous works in the SRF, the proposed method has an innovative feature that it does not need...... the fictitious current signal. Frequency-independent operation, accurate reference current extraction and relatively fast transient response are other key features of the presented strategy. The effectiveness of the proposed method is investigated by means of detailed mathematical analysis. The results confirm...
Li, Wei; Huang, Zhitong; Li, Haoyue; Ji, Yuefeng
2018-04-01
Visible light communication (VLC) is a promising candidate for short-range broadband access due to its integration of advantages for both optical communication and wireless communication, whereas multi-user access is a key problem because of the intra-cell and inter-cell interferences. In addition, the non-flat channel effect results in higher losses for users in high frequency bands, which leads to unfair qualities. To solve those issues, we propose a power adaptive multi-filter carrierless amplitude and phase access (PA-MF-CAPA) scheme, and in the first step of this scheme, the MF-CAPA scheme utilizing multiple filters as different CAP dimensions is used to realize multi-user access. The character of orthogonality among the filters in different dimensions can mitigate the effect of intra-cell and inter-cell interferences. Moreover, the MF-CAPA scheme provides different channels modulated on the same frequency bands, which further increases the transmission rate. Then, the power adaptive procedure based on MF-CAPA scheme is presented to realize quality fairness. As demonstrated in our experiments, the MF-CAPA scheme yields an improved throughput compared with multi-band CAP access scheme, and the PA-MF-CAPA scheme enhances the quality fairness and further improves the throughput compared with the MF-CAPA scheme.
Ullah Manzoor, Habib; Manzoor, Tareq; Hussain, Masroor; Manzoor, Sanaullah; Nazar, Kashif
2018-04-01
Surface electromagnetic waves are the solution of Maxwell’s frequency domain equations at the interface of two dissimilar materials. In this article, two canonical boundary-value problems have been formulated to analyze the multiplicity of electromagnetic surface waves at the interface between two dissimilar materials in the visible region of light. In the first problem, the interface between two semi-infinite rugate filters having symmetric refractive index profiles is considered and in the second problem, to enhance the multiplicity of surface electromagnetic waves, a homogeneous dielectric slab of 400 nm is included between two semi-infinite symmetric rugate filters. Numerical results show that multiple Bloch surface waves of different phase speeds, different polarization states, different degrees of localization and different field profiles are propagated at the interface between two semi-infinite rugate filters. Having two interfaces when a homogeneous dielectric layer is placed between two semi-infinite rugate filters has increased the multiplicity of electromagnetic surface waves.
International Nuclear Information System (INIS)
Ermolaev, P; Volynsky, M
2014-01-01
Recurrent stochastic data processing algorithms using representation of interferometric signal as output of a dynamic system, which state is described by vector of parameters, in some cases are more effective, compared with conventional algorithms. Interferometric signals depend on phase nonlinearly. Consequently it is expedient to apply algorithms of nonlinear stochastic filtering, such as Kalman type filters. An application of the second order extended Kalman filter and Markov nonlinear filter that allows to minimize estimation error is described. Experimental results of signals processing are illustrated. Comparison of the algorithms is presented and discussed.
A fast Gaussian filtering algorithm for three-dimensional surface roughness measurements
International Nuclear Information System (INIS)
Yuan, Y B; Piao, W Y; Xu, J B
2007-01-01
The two-dimensional (2-D) Gaussian filter can be separated into two one-dimensional (1-D) Gaussian filters. The 1-D Gaussian filter can be implemented approximately by the cascaded Butterworth filters. The approximation accuracy will be improved with the increase of the number of the cascaded filters. A recursive algorithm for Gaussian filtering requires a relatively small number of simple mathematical operations such as addition, subtraction, multiplication, or division, so that it has considerable computational efficiency and it is very useful for three-dimensional (3-D) surface roughness measurements. The zero-phase-filtering technique is used in this algorithm, so there is no phase distortion in the Gaussian filtered mean surface. High-order approximation Gaussian filters are proposed for practical use to assure high accuracy of Gaussian filtering of 3-D surface roughness measurements
A fast Gaussian filtering algorithm for three-dimensional surface roughness measurements
Yuan, Y. B.; Piao, W. Y.; Xu, J. B.
2007-07-01
The two-dimensional (2-D) Gaussian filter can be separated into two one-dimensional (1-D) Gaussian filters. The 1-D Gaussian filter can be implemented approximately by the cascaded Butterworth filters. The approximation accuracy will be improved with the increase of the number of the cascaded filters. A recursive algorithm for Gaussian filtering requires a relatively small number of simple mathematical operations such as addition, subtraction, multiplication, or division, so that it has considerable computational efficiency and it is very useful for three-dimensional (3-D) surface roughness measurements. The zero-phase-filtering technique is used in this algorithm, so there is no phase distortion in the Gaussian filtered mean surface. High-order approximation Gaussian filters are proposed for practical use to assure high accuracy of Gaussian filtering of 3-D surface roughness measurements.
Phase Center Interpolation Algorithm for Airborne GPS through the Kalman Filter
Directory of Open Access Journals (Sweden)
Edson A. Mitishita
2005-12-01
Full Text Available The aerial triangulation is a fundamental step in any photogrammetric project. The surveying of the traditional control points, depending on region to be mapped, still has a high cost. The distribution of control points at the block, and its positional quality, influence directly in the resulting precisions of the aero triangulation processing. The airborne GPS technique has as key objectives cost reduction and quality improvement of the ground control in the modern photogrammetric projects. Nowadays, in Brazil, the greatest photogrammetric companies are acquiring airborne GPS systems, but those systems are usually presenting difficulties in the operation, due to the need of human resources for the operation, because of the high technology involved. Inside the airborne GPS technique, one of the fundamental steps is the interpolation of the position of the phase center of the GPS antenna, in the photo shot instant. Traditionally, low degree polynomials are used, but recent studies show that those polynomials is reduced in turbulent flights, which are quite common, mainly in great scales flights. This paper has as objective to present a solution for that problem, through an algorithm based on the Kalman Filter, which takes into account the dynamic aspect of the problem. At the end of the paper, the results of a comparison between experiments done with the proposed methodology and a common linear interpolator are shown. These results show a significant accuracy gain at the procedure of linear interpolation, when the Kalman filter is used.
Mustamam
2016-01-01
Most of the tools that used as speed control of three phase induction motors rotation is 1 phase Variable Speed Drive (VSD), where VSD is a harmonic generator. Therefore the harmonics that arise in the VSD can be reduced by using passive LC filters fasif namely passive single tuned filter that meet the standards IEC61000-3-2 Class A.The results obtained through passive LC filter could reduce the total distortion of harmonic current (THDi) from 102.9% to 23.78% while passive sin...
Jammed-array wideband sawtooth filter.
Tan, Zhongwei; Wang, Chao; Goda, Keisuke; Malik, Omer; Jalali, Bahram
2011-11-21
We present an all-optical passive low-cost spectral filter that exhibits a high-resolution periodic sawtooth spectral pattern without the need for active optoelectronic components. The principle of the filter is the partial masking of a phased array of virtual light sources with multiply jammed diffraction orders. We utilize the filter's periodic linear map between frequency and intensity to demonstrate fast sensitive interrogation of fiber Bragg grating sensor arrays and ultrahigh-frequency electrical sawtooth waveform generation. © 2011 Optical Society of America
Bowman, D; Harte, T L; Chardonnet, V; De Groot, C; Denny, S J; Le Goc, G; Anderson, M; Ireland, P; Cassettari, D; Bruce, G D
2017-05-15
We demonstrate simultaneous control of both the phase and amplitude of light using a conjugate gradient minimisation-based hologram calculation technique and a single phase-only spatial light modulator (SLM). A cost function, which incorporates the inner product of the light field with a chosen target field within a defined measure region, is efficiently minimised to create high fidelity patterns in the Fourier plane of the SLM. A fidelity of F = 0.999997 is achieved for a pattern resembling an LG10 mode with a calculated light-usage efficiency of 41.5%. Possible applications of our method in optical trapping and ultracold atoms are presented and we show uncorrected experimental realisation of our patterns with F = 0.97 and 7.8% light efficiency.
FIR Filter Sharpening by Frequency Masking and Pipelining-Interleaving Technique
Directory of Open Access Journals (Sweden)
CIRIC, M. P.
2014-11-01
Full Text Available This paper focuses on the improvements of digital filters with a highly sharp transition zone on the Xilinx FPGA chips by combining a sharpening method based on the amplitude change function and frequency masking and PI (Pipelining-Interleaving techniques. A linear phase requires digital filter realizations with Finite Impulse Response (FIR filters. On the other hand, a drawback of FIR filters applications is a low computational efficiency, especially in applications such as filter sharpening techniques, because this technique uses processing the data by repeated passes through the same filter. Computational efficiency of FIR filters can be significantly improved by using some of the multirate techniques, and such a degree of computation savings cannot be achieved in multirate implementations of IIR (Infinite Impulse Response filters. This paper shows the realization of a filter sharpening method with FIR filters combined with frequency masking and PI (Pipelining-Interleaving technique in order to effectively realize the filter with improved characteristic. This realization at the same time keeps the good features of FIR filters such as the linear phase characteristic.
Thermal/chemical degradation of ceramic cross-flow filter materials
Energy Technology Data Exchange (ETDEWEB)
Alvin, M.A.; Lane, J.E.; Lippert, T.E.
1989-11-01
This report summarizes the 14-month, Phase 1 effort conducted by Westinghouse on the Thermal/Chemical Degradation of Ceramic Cross-Flow Filter Materials program. In Phase 1 expected filter process conditions were identified for a fixed-bed, fluid-bed, and entrained-bed gasification, direct coal fired turbine, and pressurized fluidized-bed combustion system. Ceramic cross-flow filter materials were also selected, procured, and subjected to chemical and physical characterization. The stability of each of the ceramic cross-flow materials was assessed in terms of potential reactions or phase change as a result of process temperature, and effluent gas compositions containing alkali and fines. In addition chemical and physical characterization was conducted on cross-flow filters that were exposed to the METC fluid-bed gasifier and the New York University pressurized fluidized-bed combustor. Long-term high temperature degradation mechanisms were proposed for each ceramic cross-flow material at process operating conditions. An experimental bench-scale test program is recommended to be conducted in Phase 2, generating data that support the proposed cross-flow filter material thermal/chemical degradation mechanisms. Papers on the individual subtasks have been processed separately for inclusion on the data base.
DEFF Research Database (Denmark)
Guo, Xiaoqiang; Guerrero, Josep M.
2016-01-01
Current quality is one of the most important issues for operating three-phase grid-connected inverter in distributed generation systems. In practice, the grid current quality is degraded in case of non-ideal utility voltage. A new control strategy is proposed for the three-phase gridconnected...... inverter. Different from the traditional method, our proposal utilizes the unique abc-frame complex-coefficient filter and controller to achieve the balanced, sinusoidal grid current. The main feature of the proposed method is simple and easy to implement without any frame transformation. The theoretical...
Laverick, Kiarn T.; Wiseman, Howard M.; Dinani, Hossein T.; Berry, Dominic W.
2018-04-01
The problem of measuring a time-varying phase, even when the statistics of the variation is known, is considerably harder than that of measuring a constant phase. In particular, the usual bounds on accuracy, such as the 1 /(4 n ¯) standard quantum limit with coherent states, do not apply. Here, by restricting to coherent states, we are able to analytically obtain the achievable accuracy, the equivalent of the standard quantum limit, for a wide class of phase variation. In particular, we consider the case where the phase has Gaussian statistics and a power-law spectrum equal to κp -1/|ω| p for large ω , for some p >1 . For coherent states with mean photon flux N , we give the quantum Cramér-Rao bound on the mean-square phase error as [psin(π /p ) ] -1(4N /κ ) -(p -1 )/p . Next, we consider whether the bound can be achieved by an adaptive homodyne measurement in the limit N /κ ≫1 , which allows the photocurrent to be linearized. Applying the optimal filtering for the resultant linear Gaussian system, we find the same scaling with N , but with a prefactor larger by a factor of p . By contrast, if we employ optimal smoothing we can exactly obtain the quantum Cramér-Rao bound. That is, contrary to previously considered (p =2 ) cases of phase estimation, here the improvement offered by smoothing over filtering is not limited to a factor of 2 but rather can be unbounded by a factor of p . We also study numerically the performance of these estimators for an adaptive measurement in the limit where N /κ is not large and find a more complicated picture.
Topology optimization of microwave waveguide filters
DEFF Research Database (Denmark)
Aage, Niels; Johansen, Villads Egede
2017-01-01
We present a density based topology optimization approach for the design of metallic microwave insert filters. A two-phase optimization procedure is proposed in which we, starting from a uniform design, first optimize to obtain a set of spectral varying resonators followed by a band gap...... optimization for the desired filter characteristics. This is illustrated through numerical experiments and comparison to a standard band pass filter design. It is seen that the carefully optimized topologies can sharpen the filter characteristics and improve performance. Furthermore, the obtained designs share...... little resemblance to standard filter layouts and hence the proposed design method offers a new design tool in microwave engineering....
Intelligent Optimize Design of LCL Filter for Three-Phase Voltage-Source PWM Rectifier
DEFF Research Database (Denmark)
Sun, Wei; Chen, Zhe; Wu, Xiaojie
2009-01-01
Compared to traditional L filter, a LCL filter is more effective on reducing harmonic distortion at switch frequency. So it is important to choose the LCL filter parameters to achieve good filtering effect. This paper introduces some traditional design methods. Design of a LCL filter by genetic a...
A multi-standard active-RC filter with accurate tuning system
Energy Technology Data Exchange (ETDEWEB)
Ma Heping; Yuan Fang; Shi Yin [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Dai, F F, E-mail: hpma@semi.ac.c [Department of Electrical and Computer Engineering, Auburn University, Auburn, AL 36849-5201 (United States)
2009-09-15
A low-power, highly linear, multi-standard, active-RC filter with an accurate and novel tuning architecture is presented. It exhibits IEEE 802.11 a/b/g (9.5 MHz) and DVB-H (3 MHz, 4 MHz) application. The filter exploits digitally-controlled polysilicon resistor banks and a phase lock loop type automatic tuning system. The novel and complex automatic frequency calibration scheme provides better than 4 corner frequency accuracy, and it can be powered down after calibration to save power and avoid digital signal interference. The filter achieves OIP3 of 26 dBm and the measured group delay variation of the receiver filter is 50 ns (WLAN mode). Its dissipation is 3.4 mA in RX mode and 2.3 mA (only for one path) in TX mode from a 2.85 V supply. The dissipation of calibration consumes 2 mA. The circuit has been fabricated in a 0.35 {mu}m 47 GHz SiGe BiCMOS technology; the receiver and transmitter filter occupy 0.21 mm{sup 2} and 0.11 mm{sup 2} (calibration circuit excluded), respectively.
Higher safety and saving of filter material with multi-way sorption filters
International Nuclear Information System (INIS)
Ohlmeyer, M.; Benzel, M.
1978-01-01
The multi-way filter 'Nuclear Karlsruhe' satisfies the requirements of operational safety, high utilisation of the filter material and low pressure drop. An important factor contributing to increased operational safety is due to the fact that the nearly total utilisation of the filter material eliminates the need for optimisation weighing costs against safety. The reduction in filter material consumption reduces not only the direct procurement costs but also the costs of nuclear plants, is radioactive. This contributes in several respects towards a better protection of the environment. The MWS filter can also be used, and presents the same advantages, in non-nuclear plants. (orig.) [de
Directory of Open Access Journals (Sweden)
Mohamed G. Egila
2016-12-01
Full Text Available This paper presents a proposed design for analyzing electrocardiography (ECG signals. This methodology employs highpass least-square linear phase Finite Impulse Response (FIR filtering technique to filter out the baseline wander noise embedded in the input ECG signal to the system. Discrete Wavelet Transform (DWT was utilized as a feature extraction methodology to extract the reduced feature set from the input ECG signal. The design uses back propagation neural network classifier to classify the input ECG signal. The system is implemented on Xilinx 3AN-XC3S700AN Field Programming Gate Array (FPGA board. A system simulation has been done. The design is compared with some other designs achieving total accuracy of 97.8%, and achieving reduction in utilizing resources on FPGA implementation.
Glückstad, Jesper
2009-01-01
Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, ...
The intractable cigarette ‘filter problem’
2011-01-01
Background When lung cancer fears emerged in the 1950s, cigarette companies initiated a shift in cigarette design from unfiltered to filtered cigarettes. Both the ineffectiveness of cigarette filters and the tobacco industry's misleading marketing of the benefits of filtered cigarettes have been well documented. However, during the 1950s and 1960s, American cigarette companies spent millions of dollars to solve what the industry identified as the ‘filter problem’. These extensive filter research and development efforts suggest a phase of genuine optimism among cigarette designers that cigarette filters could be engineered to mitigate the health hazards of smoking. Objective This paper explores the early history of cigarette filter research and development in order to elucidate why and when seemingly sincere filter engineering efforts devolved into manipulations in cigarette design to sustain cigarette marketing and mitigate consumers' concerns about the health consequences of smoking. Methods Relevant word and phrase searches were conducted in the Legacy Tobacco Documents Library online database, Google Patents, and media and medical databases including ProQuest, JSTOR, Medline and PubMed. Results 13 tobacco industry documents were identified that track prominent developments involved in what the industry referred to as the ‘filter problem’. These reveal a period of intense focus on the ‘filter problem’ that persisted from the mid-1950s to the mid-1960s, featuring collaborations between cigarette producers and large American chemical and textile companies to develop effective filters. In addition, the documents reveal how cigarette filter researchers' growing scientific knowledge of smoke chemistry led to increasing recognition that filters were unlikely to offer significant health protection. One of the primary concerns of cigarette producers was to design cigarette filters that could be economically incorporated into the massive scale of cigarette
Sagues, Mikel; García Olcina, Raimundo; Loayssa, Alayn; Sales, Salvador; Capmany, José
2008-01-07
We propose a novel scheme to implement tunable multi-tap complex coefficient filters based on optical single sideband modulation and narrow band optical filtering. A four tap filter is experimentally demonstrated to highlight the enhanced tuning performance provided by complex coefficients. Optical processing is performed by the use of a cascade of four phase-shifted fiber Bragg gratings specifically fabricated for this purpose.
Multi-Configuration Matched Spectral Filter Core, Phase II
National Aeronautics and Space Administration — OPTRA proposes the development of a modular, reconfigurable matched spectral filter (RMSF) spectrometer for the monitoring of greenhouse and volcanic gases. The...
Zhou, Meiling; Singh, Alok Kumar; Pedrini, Giancarlo; Osten, Wolfgang; Min, Junwei; Yao, Baoli
2018-03-01
We present a tunable output-frequency filter (TOF) algorithm to reconstruct the object from noisy experimental data under low-power partially coherent illumination, such as LED, when imaging through scattering media. In the iterative algorithm, we employ Gaussian functions with different filter windows at different stages of iteration process to reduce corruption from experimental noise to search for a global minimum in the reconstruction. In comparison with the conventional iterative phase retrieval algorithm, we demonstrate that the proposed TOF algorithm achieves consistent and reliable reconstruction in the presence of experimental noise. Moreover, the spatial resolution and distinctive features are retained in the reconstruction since the filter is applied only to the region outside the object. The feasibility of the proposed method is proved by experimental results.
Gravimetric Measurements of Filtering Facepiece Respirators Challenged With Diesel Exhaust.
Satish, Swathi; Swanson, Jacob J; Xiao, Kai; Viner, Andrew S; Kittelson, David B; Pui, David Y H
2017-07-01
Elevated concentrations of diesel exhaust have been linked to adverse health effects. Filtering facepiece respirators (FFRs) are widely used as a form of respiratory protection against diesel particulate matter (DPM) in occupational settings. Previous results (Penconek A, Drążyk P, Moskal A. (2013) Penetration of diesel exhaust particles through commercially available dust half masks. Ann Occup Hyg; 57: 360-73.) have suggested that common FFRs are less efficient than would be expected for this purpose based on their certification approvals. The objective of this study was to measure the penetration of DPM through NIOSH-certified R95 and P95 electret respirators to verify this result. Gravimetric-based penetration measurements conducted using polytetrafluoroethylene (PTFE) and polypropylene (PP) filters were compared with penetration measurements made with a Scanning Mobility Particle Sizer (SMPS, TSI Inc.), which measures the particle size distribution. Gravimetric measurements using PP filters were variable compared to SMPS measurements and biased high due to adsorption of gas phase organic material. Relatively inert PTFE filters adsorbed less gas phase organic material resulting in measurements that were more accurate. To attempt to correct for artifacts associated with adsorption of gas phase organic material, primary and secondary filters were used in series upstream and downstream of the FFR. Correcting for adsorption by subtracting the secondary mass from the primary mass improved the result for both PTFE and PP filters but this correction is subject to 'equilibrium' conditions that depend on sampling time and the concentration of particles and gas phase hydrocarbons. Overall, the results demonstrate that the use of filters to determine filtration efficiency of FFRs challenged with diesel exhaust produces erroneous results due to the presence of gas phase hydrocarbons in diesel exhaust and the tendency of filters to adsorb organic material. Published by
Design and Analysis of Robust Active Damping for LCL Filters using Digital Notch Filters
DEFF Research Database (Denmark)
Yao, Wenli; Yang, Yongheng; Zhang, Xiaobin
2017-01-01
Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled Pulse Width Modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp the reso......Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled Pulse Width Modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp...... the resonance, where the notch frequency should be aligned exactly to the resonant frequency of the LCL filter. However, parameter variations of the LCL filter as well as the time delay appearing in digital control systems will induce resonance drifting, and thus break this alignment, possibly deteriorating...... the original damping. In this paper, the effectiveness of the notch filter based active damping is firstly explored, considering the drifts of the resonant frequency. It is revealed that, when the resonant frequency drifts away from its nominal value, the phase lead or lag introduced by the notch filter may...
Enhancement of Iris Recognition System Based on Phase Only Correlation
Directory of Open Access Journals (Sweden)
Nuriza Pramita
2011-08-01
Full Text Available Iris recognition system is one of biometric based recognition/identification systems. Numerous techniques have been implemented to achieve a good recognition rate, including the ones based on Phase Only Correlation (POC. Significant and higher correlation peaks suggest that the system recognizes iris images of the same subject (person, while lower and unsignificant peaks correspond to recognition of those of difference subjects. Current POC methods have not investigated minimum iris point that can be used to achieve higher correlation peaks. This paper proposed a method that used only one-fourth of full normalized iris size to achieve higher (or at least the same recognition rate. Simulation on CASIA version 1.0 iris image database showed that averaged recognition rate of the proposed method achieved 67%, higher than that of using one-half (56% and full (53% iris point. Furthermore, all (100% POC peak values of the proposed method was higher than that of the method with full iris points.
Directory of Open Access Journals (Sweden)
Tounsi Kamel
2018-01-01
Full Text Available This paper presents sliding mode control of sensor-less parallel-connected two five-phase permanent magnet synchronous machines (PMSMs fed by a single five-leg inverter. For both machines, the rotor speeds and rotor positions as well as load torques are estimated by using Extended Kalman Filter (EKF scheme. Fully decoupled control of both machines is possible via an appropriate phase transposition while connecting the stator windings parallel and employing proposed speed sensor-less method. In the resulting parallel-connected two-machine drive, the independent control of each machine in the group is achieved by controlling the stator currents and speed of each machine under vector control consideration. The effectiveness of the proposed Extended Kalman Filter in conjunction with the sliding mode control is confirmed through application of different load torques for wide speed range operation. Comparison between sliding mode control and PI control of the proposed two-motor drive is provided. The speed response shows a short rise time, an overshoot during reverse operation and settling times is 0.075 s when PI control is used. The speed response obtained by SMC is without overshoot and follows its reference and settling time is 0.028 s. Simulation results confirm that, in transient periods, sliding mode controller remarkably outperforms its counterpart PI controller.
Cancellation of neutral current harmonics by using a four-branch star hybrid filter
DEFF Research Database (Denmark)
Blaabjerg, Frede; Rodriguez, Pedro; Candela, I.
2008-01-01
filtering topology to a three-phase four-wire system. An extensive evaluation using simulation and experimental results are conducted in this work to validate the good performance of the proposed solution for canceling current harmonics flowing through the neutral conductor.......This paper presents a new technique for filtering current harmonics in three-phase four-wire networks based on the usage of a four-branch star (FBS) filter topology. Based on single-phase inductors and capacitors, the specific layout of the FBS filter topology allows achieving a power filter...... is improved by integrating a power converter into its structure. This paper analyzes the FBS topology and presents fundamental concepts regarding the control of a generic FBS hybrid power filter. A neutral current hybrid power filter and var compensator is presented as an illustrative example applying the FBS...
MSK and offset QPSK modulation with bandlimiting filters
Prabhu, V. K.
1981-01-01
It is considered by some that minimum shift keying (MSK) is spectrally more efficient than quaternary phase-shift keying/offset quadrature phase-shift keying (QPSK/OQPSK). An analytical method is presented here for determining the detection efficiencies of MSK and QPSK/OQPSK when the constant-envelope signal is passed through a set of filters and when the resulting signal is corrupted by Gaussian noise. The detection efficiency of MSK is compared with that of QPSK/OQPSK when a four-pole Butterworth filter is used as a transmit filter and for two different receive filter functions. When the two-sided 3-dB bandwidth of the transmit filter is between approximately 1.00/T and 1.50/T, it is shown that the detection efficiency of MSK is not substantially different from that of QPSK/OQPSK. For more severe bandlimiting of the signal, the performance of MSK is shown to be inferior to that of QPSK/OQPSK. It is, therefore, concluded that MSK does not have significantly better detection efficiency when the effect of bandlimiting filters is taken into account.
Metal Mesh Filters for Terahertz Receivers, Phase II
National Aeronautics and Space Administration — The technical objective of this SBIR program is to develop and demonstrate metal mesh filters for use in NASA's low noise receivers for terahertz astronomy and...
DEFF Research Database (Denmark)
Liu, Yuan; Wu, Weimin; Li, Yun
2016-01-01
The capacitor-current-feedback active damping method is attractive for high-order-filter-based high power grid-tied inverter when the grid impedance varies within a wide range. In order to improve the system control bandwidth and attenuate the high order grid background harmonics by using the quasi....... In this paper, a low pass filter is proposed to be inserted in the capacitor current feedback loop op LLCL-filter based grid-tied inverter together with a digital proportional and differential compensator. The detailed theoretical analysis is given. For verification, simulations on a 2kW/220V/10kHz LLCL...
z-transform DFT filters and FFT's
DEFF Research Database (Denmark)
Bruun, G.
1978-01-01
The paper shows how discrete Fourier transformation can be implemented as a filter bank in a way which reduces the number of filter coefficients. A particular implementation of such a filter bank is directly related to the normal complex FFT algorithm. The principle developed further leads to types...... of DFT filter banks which utilize a minimum of complex coefficients. These implementations lead to new forms of FFT's, among which is acos/sinFFT for a real signal which only employs real coefficients. The new FFT algorithms use only half as many real multiplications as does the classical FFT....
Control Strategies for Trap Filter Interfaced Three-Phase Grid Connected Converters
DEFF Research Database (Denmark)
Min, Huang
In order to utilize renewable energy systems power electronics are needed to convert the energy to grid. The AC-DC and DC-AC power conversion are dominant in wind power system and photovoltaic system. However, the use of PWM scheme introduces undesirable harmonics. In order to enhance the grid...... damping in order to stabilize the whole system with resonance issue. LC trap filter application for current source converters to reduce the size of the filter and get a higher power factor....... integration of the renewable energy systems, the filter plays an important role. Even though this topic has already been widely studied, there are many optimizations and problems should be solved. How to design a filter for grid-connected converters in distributed generation system to get a lower loss...
Heimbuch, B K; Harnish, D A; Balzli, C; Lumley, A; Kinney, K; Wander, J D
2015-06-01
To avoid interference by water-iodine disinfection chemistry and measure directly the effect of iodine, captured from a triiodide complex bound to a filter medium, on viability of penetrating viral particles. Aerosols of MS2 coli phage were passed through control P100 or iodinated High-Efficiency Particulate Air media, collected in plastic bags, incubated for 0-10 min, collected in an impinger containing thiosulphate to consume all unreacted iodine, plated and enumerated. Comparison of viable counts demonstrated antimicrobial activity with an apparent half-life for devitalization in tens of seconds; rate of kill decreased at low humidity and free iodine was captured by the bags. The results support the mechanism of near-contact capture earlier proposed; however, the disinfection chemistry in the aerosol phase is very slow on the time scale of inhalation. This study shows that disinfection by filter-bound iodine in the aerosol phase is too slow to be clinically significant in individual respiratory protection, but that it might be of benefit to limit airborne transmission of infections in enclosed areas. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
Concrete ensemble Kalman filters with rigorous catastrophic filter divergence.
Kelly, David; Majda, Andrew J; Tong, Xin T
2015-08-25
The ensemble Kalman filter and ensemble square root filters are data assimilation methods used to combine high-dimensional, nonlinear dynamical models with observed data. Ensemble methods are indispensable tools in science and engineering and have enjoyed great success in geophysical sciences, because they allow for computationally cheap low-ensemble-state approximation for extremely high-dimensional turbulent forecast models. From a theoretical perspective, the dynamical properties of these methods are poorly understood. One of the central mysteries is the numerical phenomenon known as catastrophic filter divergence, whereby ensemble-state estimates explode to machine infinity, despite the true state remaining in a bounded region. In this article we provide a breakthrough insight into the phenomenon, by introducing a simple and natural forecast model that transparently exhibits catastrophic filter divergence under all ensemble methods and a large set of initializations. For this model, catastrophic filter divergence is not an artifact of numerical instability, but rather a true dynamical property of the filter. The divergence is not only validated numerically but also proven rigorously. The model cleanly illustrates mechanisms that give rise to catastrophic divergence and confirms intuitive accounts of the phenomena given in past literature.
Moiré phase-shifted fiber Bragg gratings in polymer optical fibers
Min, Rui; Marques, Carlos; Bang, Ole; Ortega, Beatriz
2018-03-01
We demonstrate a simple way to fabricate phase-shifted fiber Bragg grating in polymer optical fibers as a narrowband transmission filter for a variety of applications at telecom wavelengths. The filters have been fabricated by overlapping two uniform fiber Bragg gratings with slightly different periods to create a Moiré grating with only two pulses (one pulse is 15 ns) of UV power. Experimental characterization of the filter is provided under different conditions where the strain and temperature sensitivities were measured.
DEFF Research Database (Denmark)
Golestan, Saeed; Monfared, Mohammad; Guerrero, Josep M.
2013-01-01
The reference current generation (RCG) is a crucial part in the control of a shunt active power filter (APF). A variety of RCG techniques have been proposed in literature. Among these, the instantaneous reactive power theory, called pq theory, is probably the most widely used technique. The pq...... theory offers advantages such as satisfactory steady-state and dynamic performance, and at the same time simple digital implementation, however its application was limited to three-phase systems. To exploit the advantages of pq theory in single-phase systems, the single-phase pq theory has been proposed...... recently. In this paper, a simple and effective implementation of the single phase pq theory for single-phase shunt APFs is proposed. The suggested approach is based on employing second order generalized integrators (SOGI), and a phase locked loop (PLL). To fine tune the control parameters, a systematic...
Auditory filters at low-frequencies
DEFF Research Database (Denmark)
Orellana, Carlos Andrés Jurado; Pedersen, Christian Sejer; Møller, Henrik
2009-01-01
-ear transfer function), the asymmetry of the auditory filter changed from steeper high-frequency slopes at 1000 Hz to steeper low-frequency slopes below 100 Hz. Increasing steepness at low-frequencies of the middle-ear high-pass filter is thought to cause this effect. The dynamic range of the auditory filter...... was found to steadily decrease with decreasing center frequency. Although the observed decrease in filter bandwidth with decreasing center frequency was only approximately monotonic, the preliminary data indicates the filter bandwidth does not stabilize around 100 Hz, e.g. it still decreases below...
Brühl, Elisabeth; Buckup, Tiago; Motzkus, Marcus
2018-06-07
Mechanisms and optimal experimental conditions in coherent control still intensely stimulate debates. In this work, a phase-only control mechanism in an open quantum system is investigated experimentally and numerically. Several parameterizations for femtosecond pulse shaping (combination of chirp and multipulses) are exploited in transient absorption of a prototype organic molecule to control population and vibrational coherence in ground and excited states. Experimental results are further numerically simulated and corroborated with a four-level density-matrix model, which reveals a phase-only control mechanism based on the interaction between the tailored phase of the excitation pulse and the induced transient absorption. In spite of performing experiment and numerical simulations in the linear regime of excitation, the control effect amplitude depends non-linearly on the excitation energy and is explained as a pump-dump control mechanism. No evidence of single-photon control is observed with the model. Moreover, our results also show that the control effect on the population and vibrational coherence is highly dependent on the spectral detuning of the excitation spectrum. Contrary to the popular belief in coherent control experiments, spectrally resonant tailored excitation will lead to the control of the excited state only for very specific conditions.
International Nuclear Information System (INIS)
Park, Seok Joo; Park, Young Ok; Lee, Dong Geun; Ryu, Jeong In
2008-01-01
The membrane filter adhered with nanostructured porous layer was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto a conventional micron-fibrous metal filter as a substrate filter. The Sintered-Nanoparticle-Agglomerates-coated NanoStructured porous layer Membrane Filter (SNA-NSMF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by adhesion of nanoparticle-agglomerates of dendrite structure sintered onto the micron-fibrous metal filter. The size of nanoparticle-agglomerates of dendrite structure decreased with increasing the sintering temperature because nanoparticle-agglomerates shrank. When shrinking nanoparticle-agglomerates were deposited and treated with heat onto the conventional micron-fibrous metal filter, pore size of nanostructured porous layer decreased. Therefore, pressure drops of SNA-NSMFs increased from 0.3 to 0.516 KPa and filtration efficiencies remarkably increased from 95.612 to 99.9993%
Directory of Open Access Journals (Sweden)
Luís BRAVO PEREIRA
2010-09-01
Full Text Available For many years filters like the Kodak Wratten E series, or the equivalent Schneider B+W 415, were used as standard UV cut filters, necessary to obtain good quality on UV Fluorescence photography. The only problem with the use of these filters is that, when they receive the UV radiation that they should remove, they present themselves an internal fluorescence as side effect, that usually reduce contrast and quality on the final image. This article presents the results of our experiences on using some innovative filters, that appeared available on the market in recent years, projected to adsorb UV radiation even more efficiently than with the mentioned above pigment based standard filters: the interference filters for UV rejection (and, usually, for IR rejection too manufactured using interference layers, that present better results than the pigment based filters. The only problem with interference filters type is that they are sensitive to the rays direction and, because of that, they are not adequate to wide-angle lenses. The internal fluorescence for three filters: the B+W 415 UV cut (equivalent to the Kodak Wratten 2E, pigment based, the B+W 486 UV IR cut (an interference type filter, used frequently on digital cameras to remove IR or UV and the Baader UVIR rejection filter (two versions of this interference filter were used had been tested and compared. The final quality of the UV fluorescence images seems to be of a superior quality when compared to the images obtained with classic filters.
Computer processing of the scintigraphic image using digital filtering techniques
International Nuclear Information System (INIS)
Matsuo, Michimasa
1976-01-01
The theory of digital filtering was studied as a method for the computer processing of scintigraphic images. The characteristics and design techniques of finite impulse response (FIR) digital filters with linear phases were examined using the z-transform. The conventional data processing method, smoothing, could be recognized as one kind of linear phase FIR low-pass digital filtering. Ten representatives of FIR low-pass digital filters with various cut-off frequencies were scrutinized from the frequency domain in one-dimension and two-dimensions. These filters were applied to phantom studies with cold targets, using a Scinticamera-Minicomputer on-line System. These studies revealed that the resultant images had a direct connection with the magnitude response of the filter, that is, they could be estimated fairly well from the frequency response of the digital filter used. The filter, which was estimated from phantom studies as optimal for liver scintigrams using 198 Au-colloid, was successfully applied in clinical use for detecting true cold lesions and, at the same time, for eliminating spurious images. (J.P.N.)
Chang, John; Fok, Mable P; Meister, James; Prucnal, Paul R
2013-03-11
In this paper we present a fully tunable and reconfigurable single-laser multi-tap microwave photonic FIR filter that utilizes a special SM-to-MM combiner to sum the taps. The filter requires only a single laser source for all the taps and a passive component, a SM-to-MM combiner, for incoherent summing of signal. The SM-to-MM combiner does not produce optical interference during signal merging and is phase-insensitive. We experimentally demonstrate an eight-tap filter with both positive and negative programmable coefficients with excellent correspondence between predicted and measured values. The magnitude response shows a clean and accurate function across the entire bandwidth, and proves successful operation of the FIR filter using a SM-to-MM combiner.
Compact microstrip bandpass filter with tunable notch
DEFF Research Database (Denmark)
Christensen, Silas; Zhurbenko, Vitaliy; Johansen, Tom Keinicke
2014-01-01
Two different designs combining a bandpass and a notch filter are developed to operate in the receiving band from 350–470 MHz. The bandpass filter is designed from a simple structure, by use of only four short circuited stubs and a half wavelength transmission line connecting the stubs. The tunable...... notch filter ensures an attenuation level of 19.3 dB to 27.3 dB in the frequency range from 360–480 MHz. The measured passband ripple of the combined filter is less than 0.5 dB, while the insertion loss for the simplest design is less than 1.7 dB only 10 MHz from the notch frequency. Even though...... the wavelength on the selected substrate (εr = 3.55) is approximately 45 cm, the outer dimensions of the final filter only measure 10×10 cm2....
Active RC filter based implementation analysis part of two channel hybrid filter bank
Directory of Open Access Journals (Sweden)
Stojanović Vidosav
2014-01-01
Full Text Available In the present paper, a new design method for continuous-time powersymmetric active RC filters for Hybrid Filter Bank (HFB is proposed. Some theoretical properties of continious-time power-symmetric filters bank in a more general perspective are studied. This includes the derivation of a new general analytical form, and a study of poles and zeros locations in s-plane. In the proposed design method the analytic solution of filter coefficients is solved in sdomain using only one nonlinear equation Finally, the proposed approximation is compared to standard approximations. It was shown that attenuation and group delay characteristic of the proposed filter lie between Butterworth and elliptic characteristics. [Projekat Ministarstva nauke Republike Srbije, br. 32009TR
Design of switched-capacitor filter circuits using low gain amplifiers
Serra, Hugo Alexandre de Andrade
2015-01-01
This book describes the design of switched-capacitor filter circuits using low gain amplifiers and demonstrates some techniques that can minimize the effects of parasitic capacitances during the design phase. Focus is given in the design of low-pass and band-pass SC filters, and how higher order filters can be achieved using cascaded biquadratic filter sections. The authors also describe a low voltage implementation of a low-pass SC filter.
ATLAS TDAQ/DCS Event filter : Supervision Requirements
Bee, C P; Meessen, C; Qian, Z; Touchard, F; Green, P; Pinfold, J L; Wheeler, S; Negri, A; Scannicchio, D A; Vercesi, V
2002-01-01
The second iteration of the Software Development Process of the ATLAS Event Filter has been launched. A summary of the design phase of the first iteration is given in the introduction. The document gives constraints, use cases, functional and non-functional requirements for the Supervision sub-system of the Event Filter.
Indirect control of a single-phase active power filter
Directory of Open Access Journals (Sweden)
Mihai CULEA
2006-12-01
Full Text Available The control of shunt active power filters using PWM inverters consists in generating a reference by separating, using different methods, the harmonics to be eliminated. The methods used are time-consuming and need dedicated control and signal processing equipments. To avoid these setbacks a new method is proposed in the paper. The active power filter is a current PWM rectifier with voltage output and with a capacitor on the DC side. The PWM rectifier is controlled so that the sum of its current and the load’s current is a sinusoid. The control block as well as simulation results are presented.
Event filter monitoring with the ATLAS tile calorimeter
Fiorini, L
2008-01-01
The ATLAS Tile Calorimeter detector is presently involved in an intense phase of subsystems integration and commissioning with muons of cosmic origin. Various monitoring programs have been developed at different levels of the data flow to tune the set-up of the detector running conditions and to provide a fast and reliable assessment of the data quality already during data taking. This paper focuses on the monitoring system integrated in the highest level of the ATLAS trigger system, the Event Filter, and its deployment during the Tile Calorimeter commissioning with cosmic ray muons. The key feature of Event Filter monitoring is the capability of performing detector and data quality control on complete physics events at the trigger level, hence before events are stored on disk. In ATLAS' online data flow, this is the only monitoring system capable of giving a comprehensive event quality feedback.
New hybrid genetic particle swarm optimization algorithm to design multi-zone binary filter.
Lin, Jie; Zhao, Hongyang; Ma, Yuan; Tan, Jiubin; Jin, Peng
2016-05-16
The binary phase filters have been used to achieve an optical needle with small lateral size. Designing a binary phase filter is still a scientific challenge in such fields. In this paper, a hybrid genetic particle swarm optimization (HGPSO) algorithm is proposed to design the binary phase filter. The HGPSO algorithm includes self-adaptive parameters, recombination and mutation operations that originated from the genetic algorithm. Based on the benchmark test, the HGPSO algorithm has achieved global optimization and fast convergence. In an easy-to-perform optimizing procedure, the iteration number of HGPSO is decreased to about a quarter of the original particle swarm optimization process. A multi-zone binary phase filter is designed by using the HGPSO. The long depth of focus and high resolution are achieved simultaneously, where the depth of focus and focal spot transverse size are 6.05λ and 0.41λ, respectively. Therefore, the proposed HGPSO can be applied to the optimization of filter with multiple parameters.
Ensemble-based Kalman Filters in Strongly Nonlinear Dynamics
Institute of Scientific and Technical Information of China (English)
Zhaoxia PU; Joshua HACKER
2009-01-01
This study examines the effectiveness of ensemble Kalman filters in data assimilation with the strongly nonlinear dynamics of the Lorenz-63 model, and in particular their use in predicting the regime transition that occurs when the model jumps from one basin of attraction to the other. Four configurations of the ensemble-based Kalman filtering data assimilation techniques, including the ensemble Kalman filter, ensemble adjustment Kalman filter, ensemble square root filter and ensemble transform Kalman filter, are evaluated with their ability in predicting the regime transition (also called phase transition) and also are compared in terms of their sensitivity to both observational and sampling errors. The sensitivity of each ensemble-based filter to the size of the ensemble is also examined.
International Nuclear Information System (INIS)
Mao Ruiguo; Liu Mingde; Li Chunhua
1987-11-01
Expandable polystyrene pellets as filter media are used for controlled filter of uranium ore processing. Results from bench scale tests, pilot plant tests and full scale tests are satisfactory. The filter used in the full scale tests is 4 m in diameter, and the capacity is from 75 to 100 m 3 per hour. The soild content in the pregnant solution which overflowing the first thichener contains about 250 ppm of suspended solid can be reduced to 5 ∼ 10 ppm. The filter bed is backflushed with the feed liquors and the backflush returns to the countercurrent decantation circuit. The entrainment loss of the organic phase in the raffinate from solvnet extraction can be decreased by about 60% with treating the filtrated solution
DEFF Research Database (Denmark)
Alzola, Rafael Pena; Liserre, Marco; Blaabjerg, Frede
2014-01-01
) nor its rationale has been explained. Thus, in this paper a straightforward procedure is developed to tune the lead-lag network with the help of software tools. The rationale of this procedure, based on the capacitor current feedback, is elucidated. Stability is studied by means of the root locus......Three-phase active rectifiers guarantee sinusoidal input currents and unity power factor at the price of a high switching frequency ripple. To adopt an LCL-filter, instead of an L-filter, allows using reduced values for the inductances and so preserving dynamics. However, stability problems can...... without using dissipative elements but, sometimes, needing additional sensors. This solution has been addressed in many publications. The lead-lag network method is one of the first reported procedures and continues being in use. However, neither there is a direct tuning procedure (without trial and error...
MEDOF - MINIMUM EUCLIDEAN DISTANCE OPTIMAL FILTER
Barton, R. S.
1994-01-01
The Minimum Euclidean Distance Optimal Filter program, MEDOF, generates filters for use in optical correlators. The algorithm implemented in MEDOF follows theory put forth by Richard D. Juday of NASA/JSC. This program analytically optimizes filters on arbitrary spatial light modulators such as coupled, binary, full complex, and fractional 2pi phase. MEDOF optimizes these modulators on a number of metrics including: correlation peak intensity at the origin for the centered appearance of the reference image in the input plane, signal to noise ratio including the correlation detector noise as well as the colored additive input noise, peak to correlation energy defined as the fraction of the signal energy passed by the filter that shows up in the correlation spot, and the peak to total energy which is a generalization of PCE that adds the passed colored input noise to the input image's passed energy. The user of MEDOF supplies the functions that describe the following quantities: 1) the reference signal, 2) the realizable complex encodings of both the input and filter SLM, 3) the noise model, possibly colored, as it adds at the reference image and at the correlation detection plane, and 4) the metric to analyze, here taken to be one of the analytical ones like SNR (signal to noise ratio) or PCE (peak to correlation energy) rather than peak to secondary ratio. MEDOF calculates filters for arbitrary modulators and a wide range of metrics as described above. MEDOF examines the statistics of the encoded input image's noise (if SNR or PCE is selected) and the filter SLM's (Spatial Light Modulator) available values. These statistics are used as the basis of a range for searching for the magnitude and phase of k, a pragmatically based complex constant for computing the filter transmittance from the electric field. The filter is produced for the mesh points in those ranges and the value of the metric that results from these points is computed. When the search is concluded, the
Abdul-Ghani, Muhammad A; DeFronzo, Ralph A; Norton, Luke
2013-10-01
Inhibitors of sodium-glucose cotransporter 2 (SGLT2) are a novel class of antidiabetes drugs, and members of this class are under various stages of clinical development for the management of type 2 diabetes mellitus (T2DM). It is widely accepted that SGLT2 is responsible for >80% of the reabsorption of the renal filtered glucose load. However, maximal doses of SGLT2 inhibitors fail to inhibit >50% of the filtered glucose load. Because the clinical efficacy of this group of drugs is entirely dependent on the amount of glucosuria produced, it is important to understand why SGLT2 inhibitors inhibit <50% of the filtered glucose load. In this Perspective, we provide a novel hypothesis that explains this apparent puzzle and discuss some of the clinical implications inherent in this hypothesis.
Psychophysical estimates of cochlear phase response: masking by harmonic complexes.
Lentz, J J; Leek, M R
2001-12-01
Harmonic complexes with identical component frequencies and amplitudes but different phase spectra may be differentially effective as maskers. Such harmonic waveforms, constructed with positive or negative Schroeder phases, have similar envelopes and identical long-term power spectra, but the positive Schroeder-phase waveform is typically a less effective masker than the negative Schroeder-phase waveform. These masking differences have been attributed to an interaction between the masker phase spectrum and the phase characteristic of the basilar membrane. To explore this relationship, the gradient of stimulus phase change across masker bandwidth was varied by systematically altering the Schroeder-phase algorithm. Observers detected a signal tone added in-phase to a single component of a masker whose frequencies ranged from 200 to 5000 Hz, with a fundamental frequency of 100 Hz. For signal frequencies of 1000-4000 Hz, differences in masking across the harmonic complexes could be as large as 5-10 dB for phase gradients changing by only 10%. The phase gradient that resulted in a minimum amount of masking varied with signal frequency, with low frequencies masked least effectively by stimuli with rapidly changing component phases and high frequencies masked by stimuli with more shallow phase gradients. A gammachirp filter was implemented to model these results, predicting the qualitative changes in curvature of the phase-byfrequency function estimated from the empirical data: In some cases, small modifications to the gammachirp filter produced better quantitative predictions of curvature changes across frequency, but this filter, as implemented here, was unable to accurately represent all the data.
DEFF Research Database (Denmark)
Senturk, O.S.; Hava, A.M.
2011-01-01
This paper proposes the waveform reconstruction method (WRM), which is utilized in the single-phase series active filter's (SAF's) control algorithm, in order to extract the load harmonic voltage component of voltage harmonic type single-phase diode rectifier loads. Employing WRM and the line...... current sampling delay reduction method, a single-phase SAF compensated system provides higher harmonic isolation performance and higher stability margins compared to the system using conventional synchronous-reference-frame-based methods. The analytical, simulation, and experimental studies of a 2.5 k...
A high-accuracy image registration algorithm using phase-only correlation for dental radiographs
International Nuclear Information System (INIS)
Ito, Koichi; Nikaido, Akira; Aoki, Takafumi; Kosuge, Eiko; Kawamata, Ryota; Kashima, Isamu
2008-01-01
Dental radiographs have been used for the accurate assessment and treatment of dental diseases. The nonlinear deformation between two dental radiographs may be observed, even if they are taken from the same oral regions of the subject. For an accurate diagnosis, the complete geometric registration between radiographs is required. This paper presents an efficient dental radiograph registration algorithm using Phase-Only Correlation (POC) function. The use of phase components in 2D (two-dimensional) discrete Fourier transforms of dental radiograph images makes possible to achieve highly robust image registration and recognition. Experimental evaluation using a dental radiograph database indicates that the proposed algorithm exhibits efficient recognition performance even for distorted radiographs. (author)
OTRA-Based Multi-Function Inverse Filter Configuration
Directory of Open Access Journals (Sweden)
Abdhesh Kumar Singh
2017-01-01
Full Text Available A new OTRA-based multifunction Inverse filter configuration is presented which is capable of realizing low pass, high pass and band pass filters using only two OTRAs and five to six passive elements. To the best knowledge of the authors, any inverse filter configuration using OTRAs has not been reported in the literature earlier. The effect of the major parasitics of the OTRAs and their effect on the performance filter have been investigated and measured through simulation results and Monte-Carlo analysis. The workability of the proposed circuits has been confirmed by SPICE simulations using CMOS-based-OTRA realizable in 0.18 µm CMOS technology. The proposed circuits are the only ones which provide simultaneously the following features: use of reasonable number of active elements (only 2, realizability of all the three basic filter functions, employment of all virtually grounded resistors and capacitors and tunability of all filter parameters (except gain factor, H_0 for inverse high pass. The centre/cut-off frequency of the various filter circuits lying in the vicinity of 1 MHz have been found to be realizable, which has been verified through SPICE simulation results and have been found to be in good agreement with the theoretical results.
International Nuclear Information System (INIS)
Chakraborty, Subhadeep; Keller, Eric; Talley, Justin; Srivastav, Abhishek; Ray, Asok; Kim, Seungjin
2009-01-01
This communication introduces a non-intrusive method for void fraction measurement and identification of two-phase flow regimes, based on ultrasonic sensing. The underlying algorithm is built upon the recently reported theory of a statistical pattern recognition method called symbolic dynamic filtering (SDF). The results of experimental validation, generated on a laboratory test apparatus, show a one-to-one correspondence between the flow measure derived from SDF and the void fraction measured by a conductivity probe. A sharp change in the slope of flow measure is found to be in agreement with a transition from fully bubbly flow to cap-bubbly flow. (rapid communication)
Cast Steel Filtration Trials Using Ceramic-Carbon Filters
Directory of Open Access Journals (Sweden)
Lipowska B.
2014-12-01
Full Text Available Trials of cast steel filtration using two types of newly-developed foam filters in which carbon was the phase binding ceramic particles have been conducted. In one of the filters the source of carbon was flake graphite and coal-tar pitch, while in the other one graphite was replaced by a cheaper carbon precursor. The newly-developed filters are fired at 1000°C, i.e. at a much lower temperature than the currently applied ZrO2-based filters. During filtration trials the filters were subjected to the attack of a flowing metal stream having a temperature of 1650°C for 30 seconds.
A class of orthogonal nonrecursive binomial filters.
Haddad, R. A.
1971-01-01
The time- and frequency-domain properties of the orthogonal binomial sequences are presented. It is shown that these sequences, or digital filters based on them, can be generated using adders and delay elements only. The frequency-domain behavior of these nonrecursive binomial filters suggests a number of applications as low-pass Gaussian filters or as inexpensive bandpass filters.
HEPA Filter Vulnerability Assessment
International Nuclear Information System (INIS)
GUSTAVSON, R.D.
2000-01-01
This assessment of High Efficiency Particulate Air (HEPA) filter vulnerability was requested by the USDOE Office of River Protection (ORP) to satisfy a DOE-HQ directive to evaluate the effect of filter degradation on the facility authorization basis assumptions. Within the scope of this assessment are ventilation system HEPA filters that are classified as Safety-Class (SC) or Safety-Significant (SS) components that perform an accident mitigation function. The objective of the assessment is to verify whether HEPA filters that perform a safety function during an accident are likely to perform as intended to limit release of hazardous or radioactive materials, considering factors that could degrade the filters. Filter degradation factors considered include aging, wetting of filters, exposure to high temperature, exposure to corrosive or reactive chemicals, and exposure to radiation. Screening and evaluation criteria were developed by a site-wide group of HVAC engineers and HEPA filter experts from published empirical data. For River Protection Project (RPP) filters, the only degradation factor that exceeded the screening threshold was for filter aging. Subsequent evaluation of the effect of filter aging on the filter strength was conducted, and the results were compared with required performance to meet the conditions assumed in the RPP Authorization Basis (AB). It was found that the reduction in filter strength due to aging does not affect the filter performance requirements as specified in the AB. A portion of the HEPA filter vulnerability assessment is being conducted by the ORP and is not part of the scope of this study. The ORP is conducting an assessment of the existing policies and programs relating to maintenance, testing, and change-out of HEPA filters used for SC/SS service. This document presents the results of a HEPA filter vulnerability assessment conducted for the River protection project as requested by the DOE Office of River Protection
Lognormal Kalman filter for assimilating phase space density data in the radiation belts
Kondrashov, D.; Ghil, M.; Shprits, Y.
2011-11-01
Data assimilation combines a physical model with sparse observations and has become an increasingly important tool for scientists and engineers in the design, operation, and use of satellites and other high-technology systems in the near-Earth space environment. Of particular importance is predicting fluxes of high-energy particles in the Van Allen radiation belts, since these fluxes can damage spaceborne platforms and instruments during strong geomagnetic storms. In transiting from a research setting to operational prediction of these fluxes, improved data assimilation is of the essence. The present study is motivated by the fact that phase space densities (PSDs) of high-energy electrons in the outer radiation belt—both simulated and observed—are subject to spatiotemporal variations that span several orders of magnitude. Standard data assimilation methods that are based on least squares minimization of normally distributed errors may not be adequate for handling the range of these variations. We propose herein a modification of Kalman filtering that uses a log-transformed, one-dimensional radial diffusion model for the PSDs and includes parameterized losses. The proposed methodology is first verified on model-simulated, synthetic data and then applied to actual satellite measurements. When the model errors are sufficiently smaller then observational errors, our methodology can significantly improve analysis and prediction skill for the PSDs compared to those of the standard Kalman filter formulation. This improvement is documented by monitoring the variance of the innovation sequence.
International Nuclear Information System (INIS)
Niu, Wenhu; Zhong, Liyun; Sun, Peng; Zhang, Wangping; Lu, Xiaoxu
2015-01-01
Based on the quotient of inner products, a simple and rapid algorithm is proposed to retrieve the measured phase from two-frame phase-shifting interferograms with unknown phase shifts. Firstly, we filtered the background of interferograms by a Gaussian high-pass filter. Secondly, we calculated the inner products of the background-filtered interferograms. Thirdly, we extracted the phase shifts by the quotient of the inner products then calculated the measured phase by an arctangent function. Finally, we tested the performance of the proposed algorithm by the simulation calculation and the experimental research for a vortex phase plate. Both the simulation calculation and the experimental result showed that the phase shifts and the measured phase with high accuracy can be obtained by the proposed algorithm rapidly and conveniently. (paper)
Flat microwave photonic filter based on hybrid of two filters
International Nuclear Information System (INIS)
Qi, Chunhui; Pei, Li; Ning, Tigang; Li, Jing; Gao, Song
2010-01-01
A new microwave photonic filter (MPF) hybrid of two filters that can realize both multiple taps and a flat bandpass or bandstop response is presented. Based on the phase character of a Mach–Zehnder modulator (MZM), a two taps finite impulse response (FIR) filter is obtained as the first part. The second part is obtained by taking full advantage of the wavelength selectivity of the fiber Bragg grating (FBG) and the gain of a erbium-doped fiber (EDF). Combining the two filters, the flat bandpass or bandstop response is realized by changing the coupler's factor k, the reflectivity of FBG1 R 1 or the gain of the EDF g. Optimizing the system parameters, a flat bandpass response with amplitude depth of more than 45 dB is obtained at k = 0.5, R 1 = 0.33, g = 10, and a flat bandstop response is also obtained at k = 0.4, R 1 = 0.5, g = 2. In addition, the free-spectral range (FSR) can be controlled by changing the length of the EDF and the length difference between two MZMs. The method is proved feasible by some experiments. Such a method offers realistic solutions to support future radio-frequency (RF) optical communication systems
Ion exchange nonwoven fabric chemical filter. 2
International Nuclear Information System (INIS)
Sekiguchi, Hideaki
2000-01-01
This report outlined the characteristics of EPIX filter and its complex with activated carbon to eliminate organic compounds from solvent. Elimination performance of this filter was determined using an ion chromatographic analyzer. EPIX filter showed high performance to eliminate trace amount of ionic compounds. The rate of elimination was both 99% or more for NH 3 and SO 2 in an early phase of filtration. Release of dust as well as impurities was significantly reduced by the use of EPIX filter. Gases once adsorbed on the filter were not released even at an elevated temperature of atmosphere. Combined use of non-woven fabrics was possible. For EPIX filter, there are three kinds; strong acid cation exchange filter and strong/weak basic anion filters. The weak basic anion filter has been applied to the conventional apparatus in wafer makers because the filter was very effective for selective boron trapping. When polyethyleneterephthalate was used as the base polymer, radical groups produced on the polymer were co-polymerized with monomer substances. The lifetime of filter was estimated on a base of gas concentration and wind velocity to determine the time to replace with a new one. Furthermore, the loss of pressure became less than a half when EPIX filter was used. (M.N.)
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-05-29
The Phase II project was initiated on September 30, 1996. The goal of this SBIR project is to develop a cost-effective, efficient biological treatment system, a biotrickiing filter, to treat air emissions of significance to the Navy. These emissions include odors from oily bilge holding tanks, and point sources of hazardous air pollutants (HAPs) such as paint spray booths. Biotrickling filters are similar to scrubbers, but rely on microorganisms on the packing surface to remove and degrade the contaminants. Phase I work identified microbial cultures capable of degrading and growing on air pollutants of importance to the Navy. Greater than 98 percent hydrogen sulfide and methyl mercaptan removal efficiencies were demonstrated for odor applications, and 90 percent VOC (toluene, xylene, MEK, and n-butyl acetate) removal efficiencies were demonstrated for paint-spray booth applications. In addition, three different biomass support packing materials were screened. The objectives of Phase II are to: (1) develop a method to control biofilm growth; (2) establish the full-scale system pressure drop characteristics; (3) establish the effective treatment range; (4) perform overall mass balances and confirm transformation to benign products; (5) demonstrate the technology in the field at a Navy site; and (6) prepare a final report detailing the results and conclusions of the Phase II effort, including an economic analysis.
One-Dimensional Tunable Photonic-Crystal IR Filter, Phase I
National Aeronautics and Space Administration — MetroLaser proposes to design and develop an innovative narrowband tunable IR filter based on the properties of a one-dimensional photonic crystal structure with a...
One-Dimensional Tunable Photonic-Crystal IR Filter, Phase II
National Aeronautics and Space Administration — MetroLaser proposes to design and develop an innovative narrowband tunable IR filter based on the properties of a one-dimensional photonic crystal structure with a...
Generalized Phase Contrast with matched filtering using LCoS pico-projectors
DEFF Research Database (Denmark)
Bañas, Andrew Rafael; Palima, Darwin; Glückstad, Jesper
2012-01-01
, optical lattices and other beam shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices were used as binary phase-only spatial light modulators by setting the appropriate polarization of the illumination...
Thermally controlled femtosecond pulse shaping using metasurface based optical filters
Rahimi, Eesa; Şendur, Kürşat
2018-02-01
Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP) band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse's spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360°. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.
Thermally controlled femtosecond pulse shaping using metasurface based optical filters
Directory of Open Access Journals (Sweden)
Rahimi Eesa
2018-02-01
Full Text Available Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse’s spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360°. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.
Single-Chip FPGA Azimuth Pre-Filter for SAR
Gudim, Mimi; Cheng, Tsan-Huei; Madsen, Soren; Johnson, Robert; Le, Charles T-C; Moghaddam, Mahta; Marina, Miguel
2005-01-01
A field-programmable gate array (FPGA) on a single lightweight, low-power integrated-circuit chip has been developed to implement an azimuth pre-filter (AzPF) for a synthetic-aperture radar (SAR) system. The AzPF is needed to enable more efficient use of data-transmission and data-processing resources: In broad terms, the AzPF reduces the volume of SAR data by effectively reducing the azimuth resolution, without loss of range resolution, during times when end users are willing to accept lower azimuth resolution as the price of rapid access to SAR imagery. The data-reduction factor is selectable at a decimation factor, M, of 2, 4, 8, 16, or 32 so that users can trade resolution against processing and transmission delays. In principle, azimuth filtering could be performed in the frequency domain by use of fast-Fourier-transform processors. However, in the AzPF, azimuth filtering is performed in the time domain by use of finite-impulse-response filters. The reason for choosing the time-domain approach over the frequency-domain approach is that the time-domain approach demands less memory and a lower memory-access rate. The AzPF operates on the raw digitized SAR data. The AzPF includes a digital in-phase/quadrature (I/Q) demodulator. In general, an I/Q demodulator effects a complex down-conversion of its input signal followed by low-pass filtering, which eliminates undesired sidebands. In the AzPF case, the I/Q demodulator takes offset video range echo data to the complex baseband domain, ensuring preservation of signal phase through the azimuth pre-filtering process. In general, in an SAR I/Q demodulator, the intermediate frequency (fI) is chosen to be a quarter of the range-sampling frequency and the pulse-repetition frequency (fPR) is chosen to be a multiple of fI. The AzPF also includes a polyphase spatial-domain pre-filter comprising four weighted integrate-and-dump filters with programmable decimation factors and overlapping phases. To prevent aliasing of signals
Performance comparison of various time variant filters
Energy Technology Data Exchange (ETDEWEB)
Kuwata, M [JEOL Engineering Co. Ltd., Akishima, Tokyo (Japan); Husimi, K
1996-07-01
This paper describes the advantage of the trapezoidal filter used in semiconductor detector system comparing with the other time variant filters. The trapezoidal filter is the compose of a rectangular pre-filter and a gated integrator. We indicate that the best performance is obtained by the differential-integral summing type rectangular pre-filter. This filter is not only superior in performance, but also has the useful feature that the rising edge of the output waveform is linear. We introduce an example of this feature used in a high-energy experiment. (author)
Optimum filters for narrow-band frequency modulation.
Shelton, R. D.
1972-01-01
The results of a computer search for the optimum type of bandpass filter for low-index angle-modulated signals are reported. The bandpass filters are discussed in terms of their low-pass prototypes. Only filter functions with constant numerators are considered. The pole locations for the optimum filters of several cases are shown in a table. The results are fairly independent of modulation index and bandwidth.
Non-linear DSGE Models, The Central Difference Kalman Filter, and The Mean Shifted Particle Filter
DEFF Research Database (Denmark)
Andreasen, Martin Møller
This paper shows how non-linear DSGE models with potential non-normal shocks can be estimated by Quasi-Maximum Likelihood based on the Central Difference Kalman Filter (CDKF). The advantage of this estimator is that evaluating the quasi log-likelihood function only takes a fraction of a second....... The second contribution of this paper is to derive a new particle filter which we term the Mean Shifted Particle Filter (MSPFb). We show that the MSPFb outperforms the standard Particle Filter by delivering more precise state estimates, and in general the MSPFb has lower Monte Carlo variation in the reported...
ATLAS TDAQ/DCS Event Filter Event Handler Requirements
Bee, C P; Meessen, C; Qian, Z; Touchard, F; Green, P; Pinfold, J L; Wheeler, S; Negri, A; Scannicchio, D A; Vercesi, V
2002-01-01
The second iteration of the Software Development Process of the ATLAS Event Filter has been launched. A summary of the design phase of the first iteration is given in the introduction. The document gives constraints, use cases, functional and non-functional requirements for the Event Handler sub-system of the Event Filter.
Self-commissioning notch filter for active damping in three phase LCL-filter based grid converters
DEFF Research Database (Denmark)
Alzola, Rafael Pena; Liserre, Marco; Blaabjerg, Frede
2013-01-01
inductance variations it is proposed to estimate the resonance frequency by means of Fourier analysis. The Goertzel algorithm, instead of the FFT, is used to reduce the calculation and memory requirements. Thus, the proposed self-commissioning notch filter results robust and consumes little computational...
An Enhanced Non-Coherent Pre-Filter Design for Tracking Error Estimation in GNSS Receivers.
Luo, Zhibin; Ding, Jicheng; Zhao, Lin; Wu, Mouyan
2017-11-18
Tracking error estimation is of great importance in global navigation satellite system (GNSS) receivers. Any inaccurate estimation for tracking error will decrease the signal tracking ability of signal tracking loops and the accuracies of position fixing, velocity determination, and timing. Tracking error estimation can be done by traditional discriminator, or Kalman filter-based pre-filter. The pre-filter can be divided into two categories: coherent and non-coherent. This paper focuses on the performance improvements of non-coherent pre-filter. Firstly, the signal characteristics of coherent and non-coherent integration-which are the basis of tracking error estimation-are analyzed in detail. After that, the probability distribution of estimation noise of four-quadrant arctangent (ATAN2) discriminator is derived according to the mathematical model of coherent integration. Secondly, the statistical property of observation noise of non-coherent pre-filter is studied through Monte Carlo simulation to set the observation noise variance matrix correctly. Thirdly, a simple fault detection and exclusion (FDE) structure is introduced to the non-coherent pre-filter design, and thus its effective working range for carrier phase error estimation extends from (-0.25 cycle, 0.25 cycle) to (-0.5 cycle, 0.5 cycle). Finally, the estimation accuracies of discriminator, coherent pre-filter, and the enhanced non-coherent pre-filter are evaluated comprehensively through the carefully designed experiment scenario. The pre-filter outperforms traditional discriminator in estimation accuracy. In a highly dynamic scenario, the enhanced non-coherent pre-filter provides accuracy improvements of 41.6%, 46.4%, and 50.36% for carrier phase error, carrier frequency error, and code phase error estimation, respectively, when compared with coherent pre-filter. The enhanced non-coherent pre-filter outperforms the coherent pre-filter in code phase error estimation when carrier-to-noise density ratio
Low temperature properties of spin filter NbN/GdN/NbN Josephson junctions
Energy Technology Data Exchange (ETDEWEB)
Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Caruso, R. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Pal, A. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); Longobardi, L. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); American Physical Society, 1 Research Road, Ridge, New York 11961 (United States); Pepe, G.P. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Blamire, M.G. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Tafuri, F. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy)
2017-02-15
Highlights: • We study the phase dynamics of ferromagnetic NbN/GdN/NbN Josephson junctions. • The ferromagnetic insulator GdN barrier generates spin-filtering properties. • Spin filter junctions fall in the underdamped regime. • MQT occurs with the same phenomenology as in conventional Josephson junctions. • Dissipation is studied in a wide range of critical current density values. - Abstract: A ferromagnetic Josephson junction (JJ) represents a special class of hybrid system where different ordered phases meet and generate novel physics. In this work we report on the transport measurements of underdamped ferromagnetic NbN/GdN/NbN JJs at low temperatures. In these junctions the ferromagnetic insulator gadolinium nitride barrier generates spin-filtering properties and a dominant second harmonic component in the current-phase relation. These features make spin filter junctions quite interesting also in terms of fundamental studies on phase dynamics and dissipation. We discuss the fingerprints of spin filter JJs, through complementary transport measurements, and their implications on the phase dynamics, through standard measurements of switching current distributions. NbN/GdN/NbN JJs, where spin filter properties can be controllably tuned along with the critical current density (J{sub c}), turn to be a very relevant term of reference to understand phase dynamics and dissipation in an enlarged class of JJs, not necessarily falling in the standard tunnel limit characterized by low J{sub c} values.
Voltage Harmonics Mitigation through Hybrid Active Power Filter
Directory of Open Access Journals (Sweden)
Anwer Ali Sahito
2016-01-01
Full Text Available Fast dynamic response, high efficiency, low cost and small size of power electronic converters have exponentially increased their use in modern power system which resulted in harmonically distorted voltage and currents. Voltage harmonics mainly caused by current harmonics are more dangerous as performance and expected operating life of other power system equipment are affected by harmonically distorted supply voltage. Electronic filter circuits are used to improve system power quality by mitigating adverse effects of harmonics. Hybrid filters having advantages of both passive and active filters are preferred to resolve the problem of harmonics efficiently and avoiding any chance of resonance. In this paper, a three phase three wire network is considered to supply an adjustable speed drive represented by a resistive load connected across a three phase bridge rectifier. Simulation of the considered system shows THD (Total Harmonic Distortion of 18.91 and 7.61% in supply current and voltage respectively. A HAPF (Hybrid Active Power Filter is proposed to reduce these THD values below 5% as recommended by IEEE Standard-519. P-Q theorem is used to calculate required parameters for proposed filter, which is implemented through hysteresis control. Simulation results confirm the effectiveness of the designed filter as THD for both current and voltage have reduced below allowable limit of 5%.
Gigantism Precedes Filter Feeding in Baleen Whale Evolution.
Fordyce, R Ewan; Marx, Felix G
2018-05-21
Baleen whales (Mysticeti) are the largest animals on Earth, thanks to their ability to filter huge volumes of small prey from seawater. Mysticetes appeared during the Late Eocene, but evidence of their early evolution remains both sparse and controversial [1, 2], with several models competing to explain the origin of baleen-based bulk feeding [3-6]. Here, we describe a virtually complete skull of Llanocetus denticrenatus, the second-oldest (ca. 34 Ma) mysticete known. The new material represents the same individual as the type and only specimen, a fragmentary mandible. Phylogenetic analysis groups Llanocetus with the oldest mysticete, Mystacodon selenensis [2], into the basal family Llanocetidae. Llanocetus is gigantic (body length ∼8 m) compared to other early mysticetes [7-9]. The broad rostrum has sharp, widely spaced teeth with marked dental abrasion and attrition, suggesting biting and occlusal shearing. As in extant mysticetes, the palate bears many sulci, commonly interpreted as osteological correlates of baleen [3]. Unexpectedly, these sulci converge on the upper alveoli, suggesting a peri-dental blood supply to well-developed gums, rather than to inter-alveolar racks of baleen. We interpret Llanocetus as a raptorial or suction feeder, revealing that whales evolved gigantism well before the emergence of filter feeding. Rather than driving the origin of mysticetes, baleen and filtering most likely only arose after an initial phase of suction-assisted raptorial feeding [2, 4, 5]. This scenario differs strikingly from that proposed for odontocetes, whose defining adaptation-echolocation-was present even in their earliest representatives [10]. Copyright © 2018 Elsevier Ltd. All rights reserved.
Olorunsola, Olufoladare G; Kohi, Maureen P; Fidelman, Nicholas; Westphalen, Antonio C; Kolli, Pallav K; Taylor, Andrew G; Gordon, Roy L; LaBerge, Jeanne M; Kerlan, Robert K
2013-04-01
To compare the frequency of vena caval penetration by the struts of the Option and Günther Tulip cone filters on postplacement computed tomography (CT) imaging. All patients who had an Option or Günther Tulip inferior vena cava (IVC) filter placed between January 2010 and May 2012 were identified retrospectively from medical records. Of the 208 IVC filters placed, the positions of 58 devices (21 Option filters, 37 Günther Tulip filters [GTFs]) were documented on follow-up CT examinations obtained for reasons unrelated to filter placement. In cases when multiple CT studies were obtained after placement, each study was reviewed, for a total of 80 examinations. Images were assessed for evidence of caval wall penetration by filter components, noting the number of penetrating struts and any effect on pericaval tissues. Penetration of at least one strut was observed in 17% of all filters imaged by CT between 1 and 447 days following placement. Although there was no significant difference in the overall prevalence of penetration when comparing the Option filter and GTF (Option, 10%; GTF, 22%), only GTFs showed time-dependent penetration, with penetration becoming more likely after prolonged indwelling times. No patient had damage to pericaval tissues or documented symptoms attributed to penetration. Although the Günther Tulip and Option filters exhibit caval penetration at CT imaging, only the GTF exhibits progressive penetration over time. Copyright © 2013 SIR. Published by Elsevier Inc. All rights reserved.
DEFF Research Database (Denmark)
Criado, A. R.; Acedo, P.; Carpintero, G.
2012-01-01
A Continuous Wave (CW) sub-THz photonic synthesis setup based on a single Passively Mode-Locked Laser Diode (PMLLD) acting as a monolithic Optical Frequency Comb Generator (OFCG) and highly selective optical filtering has been implemented to evaluate the phase noise performance of the generated sub...
UV filters for lighting of plants
Energy Technology Data Exchange (ETDEWEB)
Doehring, T.; Koefferlein, M.; Thiel, S.; Seidlitz, H.K.; Payer, H.D. [GSF-Forschungszentrum fuer Umwelt und Gesundheit GmbH, Oberschleissheim (Germany)
1994-12-31
Different filter glasses are available which provide absorption properties suitable for gradual changes of the spectral UV-B illumination of artificial lighting. Using a distinct set of lamps and filter glasses an acceptable simulation of the UV-B part of natural global radiation can be achieved. The ageing of these and other filter materials under the extreme UV radiation in the lamphouse of a solar simulator is presently unavoidable. This instability can be dealt with only by a precise spectral monitoring and by replacing the filters accordingly. For this reason attempts would be useful to develop real ozone filters which can replace glass filters. In any case chamber experiments require a careful selection of the filter material used and must be accompanied by a continuous UV-B monitoring.
A phase transition in energy-filtered RNA secondary structures
DEFF Research Database (Denmark)
Han, Hillary Siwei; reidys, Christian
2012-01-01
In this paper we study the effect of energy parameters on minimum free energy (mfe) RNA secondary structures. Employing a simplified combinatorial energy model, that is only dependent on the diagram representation and that is not sequence specific, we prove the following dichotomy result. Mfe...... this phase transition from a discrete limit to a central limit distribution and subsequently put our result into the context of quantifying the effect of sparsification of the folding of these respective mfe-structures. We show that the sparsification of realistic mfe-structures leads to a constant time...
Abdul-Ghani, Muhammad A.; DeFronzo, Ralph A.; Norton, Luke
2013-01-01
Inhibitors of sodium-glucose cotransporter 2 (SGLT2) are a novel class of antidiabetes drugs, and members of this class are under various stages of clinical development for the management of type 2 diabetes mellitus (T2DM). It is widely accepted that SGLT2 is responsible for >80% of the reabsorption of the renal filtered glucose load. However, maximal doses of SGLT2 inhibitors fail to inhibit >50% of the filtered glucose load. Because the clinical efficacy of this group of drugs is entirely dependent on the amount of glucosuria produced, it is important to understand why SGLT2 inhibitors inhibit <50% of the filtered glucose load. In this Perspective, we provide a novel hypothesis that explains this apparent puzzle and discuss some of the clinical implications inherent in this hypothesis. PMID:24065789
Negreira, N; Rodríguez, I; Rubí, E; Cela, R
2009-07-31
A simple, inexpensive sample preparation procedure, based on the matrix solid-phase dispersion (MSPD) technique, for the determination of six UV filters: 2-ethylhexyl salicylate (EHS), 3,3,5-trimethylcyclohexyl salicylate (Homosalate, HMS), 3-(4-methylbenzylidene) camphor (4-MBC), isoamyl-p-methoxycinnamate (IAMC), 2-ethylhexyl-p-methoxycinnamate (EHMC) and octocrylene (OCR), in dust from indoor environments is presented and the influence of several operational parameters on the extraction performance discussed. Under the final working conditions, sieved samples (0.5 g) were mixed with the same amount of anhydrous sodium sulphate and dispersed with 2 g of octadecyl bonded silica (C18) in a mortar with a pestle. This blend was transferred to a polypropylene solid-phase extraction cartridge containing 2 g of activated silica, as the clean-up co-sorbent. The cartridge was first rinsed with 5 mL of n-hexane and the analytes were then recovered with 4 mL of acetonitrile. This extract was adjusted to 1 mL, filtered and the compounds were determined by gas chromatography combined with tandem mass spectrometry (GC-MS/MS). Recoveries for samples spiked at two different concentrations ranged between 77% and 99%, and the limits of quantification (LOQs) of the method between 10 and 40 ng g(-1). Analysis of settled dust from different indoor areas, including private flats, public buildings and vehicle cabins, showed that EHMC and OCR were ubiquitous in this matrix, with maximum concentrations of 15 and 41 microg g(-1), respectively. Both UV filters were also quantified in dust reference material SRM 2585 for first time. EHS, 4-MBC and IAMC were detected in some of the analyzed samples, although at lower concentrations than EHMC and OCR.
3D Wavelet-Based Filter and Method
Moss, William C.; Haase, Sebastian; Sedat, John W.
2008-08-12
A 3D wavelet-based filter for visualizing and locating structural features of a user-specified linear size in 2D or 3D image data. The only input parameter is a characteristic linear size of the feature of interest, and the filter output contains only those regions that are correlated with the characteristic size, thus denoising the image.
National Research Council Canada - National Science Library
Greseth, Gregory
1999-01-01
.... The proposed Navy DC Zonal Electrical Distribution System (DC ZEDS) being designed for the new DD-21 utilizes a rectified ac generator output which is filtered and stepped to usable voltages by local dc-dc converters...
Design strategy for the combined system of shunt passive and series active filters
Fujita, Hideki; Akagi, Hirofumi
1991-01-01
A design strategy for the combined power filter for a three-phase twelve-pulse thyristor rectifier is proposed. The shunt passive filter, which can minimize the output voltage of the series active filter, is designed and tested in a prototype model. A specially designed shunt passive filter makes it possible to reduce the required rating of the series active filter to 60% compared with a conventional shunt passive filter
Steady-State Performance of Kalman Filter for DPLL
Institute of Scientific and Technical Information of China (English)
QIAN Yi; CUI Xiaowei; LU Mingquan; FENG Zhenming
2009-01-01
For certain system models, the structure of the Kalman filter is equivalent to a second-order vari-able gain digital phase-locked loop (DPLL). To apply the knowledge of DPLLs to the design of Kalman filters, this paper studies the steady-state performance of Kalman filters for these system models. The results show that the steady-state Kalman gain has the same form as the DPLL gain. An approximate simple form for the steady-state Kalman gain is used to derive an expression for the equivalent loop bandwidth of the Kalman filter as a function of the process and observation noise variances. These results can be used to analyze the steady-state performance of a Kalman filter with DPLL theory or to design a Kalman filter model with the same steady-state performance as a given DPLL.
Common-Ground-Type Transformerless Inverters for Single-Phase Solar Photovoltaic Systems
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede
2018-01-01
This paper proposes a family of novel flying capacitor transformerless inverters for single-phase photovoltaic (PV) systems. Each of the new topologies proposed is based on a flying capacitor principle and requires only four power switches and/or diodes, one capacitor, and a small filter at the o......This paper proposes a family of novel flying capacitor transformerless inverters for single-phase photovoltaic (PV) systems. Each of the new topologies proposed is based on a flying capacitor principle and requires only four power switches and/or diodes, one capacitor, and a small filter...... at the output stage. A simple unipolar sinusoidal pulse width modulation technique is used to modulate the inverter to minimize the switching loss, output current ripple, and the filter requirements. In general, the main advantages of the new inverter topologies are: 1) the negative polarity of the PV...... description of the operating principle with modulation techniques, design guidelines, and comprehensive comparisons is presented to reveal the properties and limitations of each topology in detail. Finally, experimental results of 1-kVA prototypes are presented to prove the concept and theoretical analysis...
Self-limiting filters for band-selective interferer rejection or cognitive receiver protection
Nordquist, Christopher; Scott, Sean Michael; Custer, Joyce Olsen; Leonhardt, Darin; Jordan, Tyler Scott; Rodenbeck, Christopher T.; Clem, Paul G.; Hunker, Jeff; Wolfley, Steven L.
2017-03-07
The present invention related to self-limiting filters, arrays of such filters, and methods thereof. In particular embodiments, the filters include a metal transition film (e.g., a VO.sub.2 film) capable of undergoing a phase transition that modifies the film's resistivity. Arrays of such filters could allow for band-selective interferer rejection, while permitting transmission of non-interferer signals.
Self-limiting filters for band-selective interferer rejection or cognitive receiver protection
Energy Technology Data Exchange (ETDEWEB)
Nordquist, Christopher; Scott, Sean Michael; Custer, Joyce Olsen; Leonhardt, Darin; Jordan, Tyler Scott; Rodenbeck, Christopher T.; Clem, Paul G.; Hunker, Jeff; Wolfley, Steven L.
2017-03-07
The present invention related to self-limiting filters, arrays of such filters, and methods thereof. In particular embodiments, the filters include a metal transition film (e.g., a VO.sub.2 film) capable of undergoing a phase transition that modifies the film's resistivity. Arrays of such filters could allow for band-selective interferer rejection, while permitting transmission of non-interferer signals.
A robust nonlinear filter for image restoration.
Koivunen, V
1995-01-01
A class of nonlinear regression filters based on robust estimation theory is introduced. The goal of the filtering is to recover a high-quality image from degraded observations. Models for desired image structures and contaminating processes are employed, but deviations from strict assumptions are allowed since the assumptions on signal and noise are typically only approximately true. The robustness of filters is usually addressed only in a distributional sense, i.e., the actual error distribution deviates from the nominal one. In this paper, the robustness is considered in a broad sense since the outliers may also be due to inappropriate signal model, or there may be more than one statistical population present in the processing window, causing biased estimates. Two filtering algorithms minimizing a least trimmed squares criterion are provided. The design of the filters is simple since no scale parameters or context-dependent threshold values are required. Experimental results using both real and simulated data are presented. The filters effectively attenuate both impulsive and nonimpulsive noise while recovering the signal structure and preserving interesting details.
In Situ Cleanable Alternative HEPA Filter Media
International Nuclear Information System (INIS)
Adamson, D. J.; Terry, M. T.
2002-01-01
The Westinghouse Savannah River Company, located at the Savannah River Site in Aiken, South Carolina, is currently testing two types of filter media for possible deployment as in situ regenerable/cleanable High Efficiency Particulate Air (HEPA) filters. The filters are being investigated to replace conventional, disposable, glass-fiber, HEPA filters that require frequent removal, replacement, and disposal. This is not only costly and subjects site personnel to radiation exposure, but adds to the ever-growing waste disposal problem. The types of filter media being tested, as part of a National Energy Technology Laboratory procurement, are sintered nickel metal and ceramic monolith membrane. These media were subjected to a hostile environment to simulate conditions that challenge the high-level waste tank ventilation systems. The environment promoted rapid filter plugging to maximize the number of filter loading/cleaning cycles that would occur in a specified period of time. The filters were challenged using nonradioactive simulated high-level waste materials and atmospheric dust; materials that cause filter pluggage in the field. The filters are cleaned in situ using an aqueous solution. The study found that both filter media were insensitive to high humidity or moisture conditions and were easily cleaned in situ. The filters regenerated to approximately clean filter status even after numerous plugging and in situ cleaning cycles. Air Techniques International is conducting particle retention testing on the filter media at the Oak Ridge Filter Test Facility. The filters are challenged using 0.3-mm di-octyl phthalate particles. Both the ceramic and sintered media have a particle retention efficiency > 99.97%. The sintered metal and ceramic filters not only can be cleaned in situ, but also hold great potential as a long life alternative to conventional HEPA filters. The Defense Nuclear Facility Safety Board Technical Report, ''HEPA Filters Used in the Department of
FEATURES OF THE REGENERATION PROCESS OF THE FILTER
Directory of Open Access Journals (Sweden)
S. Yu. Panov
2015-01-01
Full Text Available The regeneration system exercises significant influence on the efficiency and reliability of the filters. During operation of the filter it continuously increases the hydraulic resistance and the gas permeability of the filter material decreases as the deposition of the disperse phase capturable on the filter element, and to maintain the bandwidth of the filter in the filter element within the set must be periodically changed or regenerated. Thus, regeneration of a process of removing part of the dust layer with the purpose of full or partial reduction of the initial filter partitioning properties. On the basis of theoretical synthesis, physico-chemical effects of dust in layers, analysis of energy effects, developed methods of intensification of the process of regeneration of particulate filters. Pneumopulse regeneration of bag filter has been investigated, and based on it a regression equation for regeneration efficiency has been derived. It has been shown that pulse pressure exerts the dominant influence on the regeneration efficiency. The obtained model was used for assessment and prediction of the efficiency of the pneumopulse system of regeneration of bag filters at a number of structural materials producing enterprises in the Voronezh region.
Cost/benefit evaluation of electrofibrous air filters
International Nuclear Information System (INIS)
Bergman, W.; Kuhl, W.; Biermann, A.; Lum, B.
1986-01-01
Experimental electric air filters based on the principle of superimposing an electric field over conventional fibrous air filters have been developed. The different experimental electric filters described in this report include prefilters for use in glove boxes and in ventilation systems, re-circulating air filters, electric HEPA filters, and high efficiency, high temperature air filters. In each case the large improvement in filter efficiency that occurs when a mechanical filter is electrified is demonstrated. Also a significant increase in the particle loading capacity of filters in many of our evaluations is demonstrated. Both laboratory and field test results are presented. This paper also demonstrates that the performance of all of our electric filter designs, except one, can be matched by conventional mechanical air filters and usually at a lower cost. The one exception is the high temperature, high efficiency electric air filter. In that case there is no mechanical filter media that can match the performance of the electric air filter. Our findings show that electric air filters are only cost effective compared to mechanical air filters when the performance of the mechanical air filter cannot be further improved by mechanical means. (author)
A wavelet phase filter for emission tomography
International Nuclear Information System (INIS)
Olsen, E.T.; Lin, B.
1995-01-01
The presence of a high level of noise is a characteristic in some tomographic imaging techniques such as positron emission tomography (PET). Wavelet methods can smooth out noise while preserving significant features of images. Mallat et al. proposed a wavelet based denoising scheme exploiting wavelet modulus maxima, but the scheme is sensitive to noise. In this study, the authors explore the properties of wavelet phase, with a focus on reconstruction of emission tomography images. Specifically, they show that the wavelet phase of regular Poisson noise under a Haar-type wavelet transform converges in distribution to a random variable uniformly distributed on [0, 2π). They then propose three wavelet-phase-based denoising schemes which exploit this property: edge tracking, local phase variance thresholding, and scale phase variation thresholding. Some numerical results are also presented. The numerical experiments indicate that wavelet phase techniques show promise for wavelet based denoising methods
A Review of Passive Power Filters for Three-Phase Grid-Connected Voltage-Source Converters
DEFF Research Database (Denmark)
Beres, Remus Narcis; Wang, Xiongfei; Liserre, Marco
2016-01-01
and source impedances. Furthermore, the stabilizing effect is more difficult to be guaranteed for cost-optimized filters, which are characterized by low inductance and high capacitance passive components. In this paper, several passive filter topologies used to interface voltage source converters......In order to reduce size and cost, high-order passive filters are generally preferred in power converters to cancel out high frequency harmonics caused by pulse width modulation. However, the filter resonance peaks may require the use of passive dampers to stabilize the interactions between the load...
A Nonadaptive Window-Based PLL for Single-Phase Applications
DEFF Research Database (Denmark)
Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez
2018-01-01
The rectangular window filter, typically known as the moving average filter (MAF), is a quasi-ideal low-pass filter that has found wide application in designing advanced single-phase phase-locked loops (PLLs). Most often, the MAF is employed as an in-loop filter within the control loop of the sin......The rectangular window filter, typically known as the moving average filter (MAF), is a quasi-ideal low-pass filter that has found wide application in designing advanced single-phase phase-locked loops (PLLs). Most often, the MAF is employed as an in-loop filter within the control loop...... response is avoided. Nevertheless, the PLL implementation complexity considerably increases as MAFs are frequency-adaptive and, therefore, they require an additional frequency detector for estimating the grid frequency. To reduce the implementation complexity while maintaining a good performance, using...... a nonadaptive MAF-based QSG with some error compensators is suggested in this letter. The effectiveness of the resultant PLL, which is briefly called the nonadaptive MAF-based PLL, is verified using experimental results....
The overview of damping methods for three-phase grid-tied inverter with LLCL-filter
DEFF Research Database (Denmark)
Huang, Min; Blaabjerg, Frede; Loh, Poh Chiang
2014-01-01
Compared with LCL filter, an LLCL-filter is characterized with smaller size and lower cost for grid-connected inverters. But this high order filter may also have resonant problem which will affect the system stability. Many methods can be used to alleviate the resonant problem including active da...... and shows the advantages as well as disadvantages of these methods....
High flow ceramic pot filters.
van Halem, D; van der Laan, H; Soppe, A I A; Heijman, S G J
2017-11-01
Ceramic pot filters are considered safe, robust and appropriate technologies, but there is a general consensus that water revenues are limited due to clogging of the ceramic element. The objective of this study was to investigate the potential of high flow ceramic pot filters to produce more water without sacrificing their microbial removal efficacy. High flow pot filters, produced by increasing the rice husk content, had a higher initial flow rate (6-19 L h -1 ), but initial LRVs for E. coli of high flow filters was slightly lower than for regular ceramic pot filters. This disadvantage was, however, only temporarily as the clogging in high flow filters had a positive effect on the LRV for E. coli (from below 1 to 2-3 after clogging). Therefore, it can be carefully concluded that regular ceramic pot filters perform better initially, but after clogging, the high flow filters have a higher flow rate as well as a higher LRV for E. coli. To improve the initial performance of new high flow filters, it is recommended to further utilize residence time of the water in the receptacle, since additional E. coli inactivation was observed during overnight storage. Although a relationship was observed between flow rate and LRV of MS2 bacteriophages, both regular and high flow filters were unable to reach over 2 LRV. Copyright © 2017 Elsevier Ltd. All rights reserved.
Scargle, Jeffrey D.
1990-01-01
While chaos arises only in nonlinear systems, standard linear time series models are nevertheless useful for analyzing data from chaotic processes. This paper introduces such a model, the chaotic moving average. This time-domain model is based on the theorem that any chaotic process can be represented as the convolution of a linear filter with an uncorrelated process called the chaotic innovation. A technique, minimum phase-volume deconvolution, is introduced to estimate the filter and innovation. The algorithm measures the quality of a model using the volume covered by the phase-portrait of the innovation process. Experiments on synthetic data demonstrate that the algorithm accurately recovers the parameters of simple chaotic processes. Though tailored for chaos, the algorithm can detect both chaos and randomness, distinguish them from each other, and separate them if both are present. It can also recover nonminimum-delay pulse shapes in non-Gaussian processes, both random and chaotic.
DEFF Research Database (Denmark)
Marques, C. A. F.; Pospori, A.; Pereira, L.
2017-01-01
We present the first phase-shifted polymer optical fiber Bragg grating sensor inscribed with only one KrF laser pulse. The phase shift defect was created directly during the grating inscription process by placing a very narrow blocking aperture, in the center of the UV beam. One laser pulse...
Phan, Anh Tuan; Ho, Duc Du; Hermann, Gilles; Wira, Patrice
2015-12-01
For power quality issues like reducing harmonic pollution, reactive power and load unbalance, the estimation of the fundamental frequency of a power lines in a fast and precise way is essential. This paper introduces a new state-space model to be used with an extended Kalman filter (EKF) for estimating the frequency of distorted power system signals in real-time. The proposed model takes into account all the characteristics of a general three-phase power system and mainly the unbalance. Therefore, the symmetrical components of the power system, i.e., their amplitude and phase angle values, can also be deduced at each iteration from the proposed state-space model. The effectiveness of the method has been evaluated. Results and comparisons of online frequency estimation and symmetrical components identification show the efficiency of the proposed method for disturbed and time-varying signals.
Factors Influencing HEPA Filter Performance
International Nuclear Information System (INIS)
Parsons, M.S.; Waggoner, Ch.A.
2009-01-01
Properly functioning HEPA air filtration systems depend on a variety of factors that start with the use of fully characterized challenge conditions for system design and then process control during operation. This paper addresses factors that should be considered during the design phase as well as operating parameters that can be monitored to ensure filter function and lifetime. HEPA filters used in nuclear applications are expected to meet design, fabrication, and performance requirements set forth in the ASME AG-1 standard. The DOE publication Nuclear Air Cleaning Handbook (NACH) is an additional guidance document for design and operation HEPA filter systems in DOE facilities. These two guidelines establish basic maximum operating parameters for temperature, maximum aerosol particle size, maximum particulate matter mass concentration, acceptable differential pressure range, and filter media velocity. Each of these parameters is discussed along with data linking variability of each parameter with filter function and lifetime. Temporal uncertainty associated with gas composition, temperature, and absolute pressure of the air flow can have a direct impact on the volumetric flow rate of the system with a corresponding impact on filter media velocity. Correlations between standard units of flow rate (standard meters per minute or cubic feet per minute) versus actual units of volumetric flow rate are shown for variations in relative humidity for a 70 deg. C to 200 deg. C temperature range as an example of gas composition that, uncorrected, will influence media velocity. The AG-1 standard establishes a 2.5 cm/s (5 feet per minute) ceiling for media velocities of nuclear grade HEPA filters. Data are presented that show the impact of media velocities from 2.0 to 4.0 cm/s media velocities (4 to 8 fpm) on differential pressure, filter efficiency, and filter lifetime. Data will also be presented correlating media velocity effects with two different particle size
Chao, Tien-Hsin; Yu, Jeffrey
1990-01-01
Limitations associated with the binary phase-only filter often used in optical correlators are presently circumvented in the writing of complex-valued data on a gray-scale spatial light modulator through the use of a computer-generated hologram (CGH) algorithm. The CGH encodes complex-valued data into nonnegative real CGH data in such a way that it may be encoded in any of the available gray-scale spatial light modulators. A CdS liquid-crystal light valve is used for the complex-valued CGH encoding; computer simulations and experimental results are compared, and the use of such a CGH filter as the synapse hologram in a holographic optical neural net is discussed.
Gallego, E. E.; Ascorbe, J.; Del Villar, I.; Corres, J. M.; Matias, I. R.
2018-05-01
This work describes the process of nanofabrication of phase-shifted Bragg gratings on the end facet of a multimode optical fiber with a pulsed DC sputtering system based on a single target. Several structures have been explored as a function of parameters such as the number of layers or the phase-shift. The experimental results, corroborated with simulations based on plane-wave propagation in a stack of homogeneous layers, indicate that the phase-shift can be controlled with a high degree of accuracy. The device could be used both in communications, as a filter, or in the sensors domain. As an example of application, a humidity sensor with wavelength shifts of 12 nm in the range of 30 to 90% relative humidity (200 pm/% relative humidity) is presented.
Target Response Adaptation for Correlation Filter Tracking
Bibi, Adel Aamer; Mueller, Matthias; Ghanem, Bernard
2016-01-01
Most correlation filter (CF) based trackers utilize the circulant structure of the training data to learn a linear filter that best regresses this data to a hand-crafted target response. These circularly shifted patches are only approximations
Comparison of three filters in asteroid-based autonomous navigation
International Nuclear Information System (INIS)
Cui Wen; Zhu Kai-Jian
2014-01-01
At present, optical autonomous navigation has become a key technology in deep space exploration programs. Recent studies focus on the problem of orbit determination using autonomous navigation, and the choice of filter is one of the main issues. To prepare for a possible exploration mission to Mars, the primary emphasis of this paper is to evaluate the capability of three filters, the extended Kalman filter (EKF), unscented Kalman filter (UKF) and weighted least-squares (WLS) algorithm, which have different initial states during the cruise phase. One initial state is assumed to have high accuracy with the support of ground tracking when autonomous navigation is operating; for the other state, errors are set to be large without this support. In addition, the method of selecting asteroids that can be used for navigation from known lists of asteroids to form a sequence is also presented in this study. The simulation results show that WLS and UKF should be the first choice for optical autonomous navigation during the cruise phase to Mars
Adaptive Control of Non-Minimum Phase Modal Systems Using Residual Mode Filters2. Parts 1 and 2
Balas, Mark J.; Frost, Susan
2011-01-01
Many dynamic systems containing a large number of modes can benefit from adaptive control techniques, which are well suited to applications that have unknown parameters and poorly known operating conditions. In this paper, we focus on a direct adaptive control approach that has been extended to handle adaptive rejection of persistent disturbances. We extend this adaptive control theory to accommodate problematic modal subsystems of a plant that inhibit the adaptive controller by causing the open-loop plant to be non-minimum phase. We will modify the adaptive controller with a Residual Mode Filter (RMF) to compensate for problematic modal subsystems, thereby allowing the system to satisfy the requirements for the adaptive controller to have guaranteed convergence and bounded gains. This paper will be divided into two parts. Here in Part I we will review the basic adaptive control approach and introduce the primary ideas. In Part II, we will present the RMF methodology and complete the proofs of all our results. Also, we will apply the above theoretical results to a simple flexible structure example to illustrate the behavior with and without the residual mode filter.
Reactions of newly formed fission products in the gas phase
International Nuclear Information System (INIS)
Strickert, R.G.
1976-01-01
A dynamic gas-flow system was constructed which stopped fission products in the gas phase and rapidly separated (in less than 2 sec) volatile compounds from non-volatile ones. The filter assembly designed and used was shown to stop essentially all non-volatile fission products. Between 5 percent and 20 percent of tellurium fission-product isotopes reacted with several hydrocarbon gases to form volatile compounds, which passed through the filter. With carbon monoxide gas, volatile tellurium compound(s) (probably TeCO) were also formed with similar efficiencies. The upper limits for the yields of volatile compounds formed between CO and tin and antimony fission products were shown to be less than 0.3 percent, so tellurium nuclides, not their precursors, reacted with CO. It was found that CO reacted preferentially with independently produced tellurium atoms; the reaction efficiency of beta-produced atoms was only 27 +- 3 percent of that of the independently formed atoms. The selectivity, which was independent of the over-all reaction efficiency, was shown to be due to reaction of independently formed atoms in the gas phase. The gas phase reactions are believed to occur mainly at thermal energies because of the independence of the yield upon argon moderator mole-fraction (up to 80 percent). It was shown in some experiments that about one-half of the TeCO decomposed in passing through a filter and that an appreciable fraction (approximately 20 percent) of the tellurium atoms deposited on the filter reacted agin with CO. Other tellurium atoms on the filter surface (those formed by beta decay and those formed independently but not reacting in the gas phase) also reacted with CO, but probably somewhat less efficiently than atoms formed by TeCO decomposition. No evidence was found for formation of TeCO as a direct result of beta-decay
Analysis and control of a shunt active power filter
Energy Technology Data Exchange (ETDEWEB)
Ottersten, R.; Petersson, Andreas [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Electric Power Engineering
1999-09-01
This report deals with active power filtering of low-frequency current harmonics. The active filter consists of a forced-commutated voltage source inverter with a digital control system. The aim of this master thesis is to investigate the performance of a shunt active power filter, and the parameters influence on the system performance. Three different harmonic identification methods are presented and compared. The shunt active power filter is very well suited for harmonic current reduction, provided that the phase shift due to the digital implementation of the control system is compensated. The performance of the active power filter depends on the switching frequency. When using individual harmonic detection methods the amount of compensation can be fully controlled for each current harmonic.
Directory of Open Access Journals (Sweden)
Nima Tabatabaei
2018-04-01
Full Text Available Conventional infrared thermography techniques, including pulsed and lock-in thermography, have shown great potential for non-destructive evaluation of broad spectrum of materials, spanning from metals to polymers to biological tissues. However, performance of these techniques is often limited due to the diffuse nature of thermal wave fields, resulting in an inherent compromise between inspection depth and depth resolution. Recently, matched-filter thermography has been introduced as a means for overcoming this classic limitation to enable depth-resolved subsurface thermal imaging and improving axial/depth resolution. This paper reviews the basic principles and experimental results of matched-filter thermography: first, mathematical and signal processing concepts related to matched-fileting and pulse compression are discussed. Next, theoretical modeling of thermal-wave responses to matched-filter thermography using two categories of pulse compression techniques (linear frequency modulation and binary phase coding are reviewed. Key experimental results from literature demonstrating the maintenance of axial resolution while inspecting deep into opaque and turbid media are also presented and discussed. Finally, the concept of thermal coherence tomography for deconvolution of thermal responses of axially superposed sources and creation of depth-selective images in a diffusion-wave field is reviewed.
Word-serial Architectures for Filtering and Variable Rate Decimation
Directory of Open Access Journals (Sweden)
Eugene Grayver
2002-01-01
Full Text Available A new flexible architecture is proposed for word-serial filtering and variable rate decimation/interpolation. The architecture is targeted for low power applications requiring medium to low data rate and is ideally suited for implementation on either an ASIC or an FPGA. It combines the small size and low power of an ASIC with the programmability and flexibility of a DSP. An efficient memory addressing scheme eliminates the need for power hungry shift registers and allows full reconfiguration. The decimation ratio, filter length and filter coefficients can all be changed in real time. The architecture takes advantage of coefficient symmetries in linear phase filters and in polyphase components.
Experience with three percutaneous vena cava filters
International Nuclear Information System (INIS)
McCowan, T.C.; Ferris, E.J.; Harshfield, D.L.; Hassell, D.R.; Baker, M.L.
1987-01-01
Twenty-one Kimray-Greenfield, 33 bird's nest, and 19 Amplatz vena cava filters were placed percutaneously. The Kimray-Greenfield filter was the most difficult to insert. The major problem was the insertion site, which required venipuncture with a 24-F catheter. Minor hemorrhage was frequent, and femoral vein thrombosis occurred in four patients. No migration, caval thrombosis, or pulmonary emboli were seen after Kimray-Greenfield filter placement. The bird's nest filter was relatively easy to insert, although in two cases the filter prongs could not be adequately seated in the wall of the inferior vena cava. Three patients with bird's nest filters had thrombosis below the filter, and three filters migrated to the heart. One migrated filter could not be removed. One patient had multiple small pulmonary emboli at autopsy. No other pulmonary emboli after filter placement were noted. The Amplatz filter was the easiest of the three filters to insert. Only one patient with an Amplatz filter had thrombosis of the vena cava below the filter. No filter migrations were documented, and no recurrent pulmonary emboli were found on clinical or radiologic follow-up. The Amplatz vena cava filter is easier to place than percutaneous Kimray-Greenfield or bird's nest filters, has a low complication rate, and has proven to be clinically effective in preventing pulmonary emboli
Advanced Filter Technology For Nuclear Thermal Propulsion
Castillon, Erick
2015-01-01
The Scrubber System focuses on using HEPA filters and carbon filtration to purify the exhaust of a Nuclear Thermal Propulsion engine of its aerosols and radioactive particles; however, new technology may lend itself to alternate filtration options, which may lead to reduction in cost while at the same time have the same filtering, if not greater, filtering capabilities, as its predecessors. Extensive research on various types of filtration methods was conducted with only four showing real promise: ionization, cyclonic separation, classic filtration, and host molecules. With the four methods defined, more research was needed to find the devices suitable for each method. Each filtration option was matched with a device: cyclonic separators for the method of the same name, electrostatic separators for ionization, HEGA filters, and carcerands for the host molecule method. Through many hours of research, the best alternative for aerosol filtration was determined to be the electrostatic precipitator because of its high durability against flow rate and its ability to cleanse up to 99.99% of contaminants as small as 0.001 micron. Carcerands, which are the only alternative to filtering radioactive particles, were found to be non-existent commercially because of their status as a "work in progress" at research institutions. Nevertheless, the conclusions after the research were that HEPA filters is recommended as the best option for filtering aerosols and carbon filtration is best for filtering radioactive particles.
A 65mW,0.4-2.3 GHz bandpass filter for satellite receivers
Tang, van der J.D.; Kasperkovitz, D.; Bretveld, A.
2002-01-01
A monolithic tunable bandpass filter for satellite receiver front-ends is presented. The nter frequency of the bandpass filter can be tuned from 0.4 GHz to 2.3 GHz. The filter is constructed using four transconductor-C poly-phase filter sections and has a 50 dB variable gain range. At 20 dB
Directory of Open Access Journals (Sweden)
Li Bin
2015-01-01
Full Text Available Accurate measurements of cigarette coal temperature are essential to understand the thermophysical and thermo-chemical processes in a burning cigarette. The last system-atic studies of cigarette burning temperature measurements were conducted in the mid-1970s. Contemporary cigarettes have evolved in design features and multiple standard machine-smoking regimes have also become available, hence there is a need to re-examine cigarette combustion. In this work, we performed systematic measurements on gas-phase temperature of burning cigarettes using an improved fine thermocouple technique. The effects of machine-smoking parameters (puff volume and puff duration and filter ventilation levels were studied with high spatial and time resolutions during single puffs. The experimental results were presented in a number of differ-ent ways to highlight the dynamic and complex thermal processes inside a burning coal. A mathematical distribution equation was used to fit the experimental temperature data. Extracting and plotting the distribution parameters against puffing time revealed complex temperature profiles under different coal volume as a function of puffing intensities or filter ventilation levels. By dividing the coal volume prior to puffing into three temperature ranges (low-temperature from 200 to 400 °C, medium-temperature from 400 to 600 °C, and high-temperature volume above 600 °C by following their development at different smoking regimes, useful mechanistic details were obtained. Finally, direct visualisation of the gas-phase temperature through detailed temperature and temperature gradient contour maps provided further insights into the complex thermo-physics of the burning coal. [Beitr. Tabakforsch. Int. 26 (2014 191-203
Technical Note: Kinect V2 surface filtering during gantry motion for radiotherapy applications.
Nazir, Souha; Rihana, Sandy; Visvikis, Dimitris; Fayad, Hadi
2018-04-01
In radiotherapy, the Kinect V2 camera, has recently received a lot of attention concerning many clinical applications including patient positioning, respiratory motion tracking, and collision detection during the radiotherapy delivery phase. However, issues associated with such applications are related to some materials and surfaces reflections generating an offset in depth measurements especially during gantry motion. This phenomenon appears in particular when the collimator surface is observed by the camera; resulting in erroneous depth measurements, not only in Kinect surfaces itself, but also as a large peak when extracting a 1D respiratory signal from these data. In this paper, we proposed filtering techniques to reduce the noise effect in the Kinect-based 1D respiratory signal, using a trend removal filter, and in associated 2D surfaces, using a temporal median filter. Filtering process was validated using a phantom, in order to simulate a patient undergoing radiotherapy treatment while having the ground truth. Our results indicate a better correlation between the reference respiratory signal and its corresponding filtered signal (Correlation coefficient of 0.76) than that of the nonfiltered signal (Correlation coefficient of 0.13). Furthermore, surface filtering results show a decrease in the mean square distance error (85%) between the reference and the measured point clouds. This work shows a significant noise compensation and surface restitution after surface filtering and therefore a potential use of the Kinect V2 camera for different radiotherapy-based applications, such as respiratory tracking and collision detection. © 2018 American Association of Physicists in Medicine.
Exploitation of Digital Filters to Advance the Single-Phase T/4 Delay PLL System
DEFF Research Database (Denmark)
Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede
2016-01-01
will violate this design rule and it can become a major challenge for digital controllers. To deal with the above issue, this paper first exploits a virtual unit delay (z_v^-1) to emulate the viable sampling behavior in practical digital signal processors with a fixed sampling rate. This exploitation......With the development of digital signal processing technologies, control and monitoring of power electronics conversion systems have been evolving to become fully digital. As the basic element in the design and analysis phase of digital controllers or filters, a number of unit delays (z^-1) have...... been employed, e.g., in a cascaded structure. Practically, the number of unit delays is designed as an integer, which is related to the sampling frequency (e.g., 50 Hz). More common, the sampling frequency is fixed during operation for simplicity and design. Hence, any disturbance in the ac signal...
DEFF Research Database (Denmark)
1996-01-01
The invention relates to a method and a system for synthesizing a prescribed intensity pattern based on phase contrast imaging that is not based on the assumption of prior art methods that the pahase shift phi is less than 1 radian. An improved method based on a simple imaging operation...... phasors attain predetermined values for predetermined spatial frequencies, and the phasor value of the specific resolution element of the spatial phase mask corresponds to a distinct intensity level of the image of the resolution element in the intensity pattern, and a spatial phase filter for phase...... shifting of a part of the electromagntic radiation, in combination with an imaging system for generation of the intensity pattern by interference in the image plane of the imaging system between the part of the electromagnetic raidation that has been phase shifted by the phase filter and the remaining part...
Apparatus for Removing Remaining Adhesives of Filter
International Nuclear Information System (INIS)
Kang, Il Sik; Kim, Tae Kuk; Hong, Dae Seok; Ji, Young Yong; Ryu, Woo Seog
2010-01-01
A Large amount of ventilation filter was used at radiation areas not only in nuclear power plants but also in nuclear facilities. These spent ventilation filters are generated as radioactive waste and composed of a steel frame, glass fiber media and aluminum separator. When treated, the spent filter is separated into filter media for air purification and frame. After separation, while the filter media is collected using steel drum for reducing internal exposure, the filter frame is treated further to remove adhesives for recycling the frame as many as possible in order to reduce waste and cost and improve working conditions. Usually, the adhesives are separated from the filter frame manually. As a result, a lot of time and labor is required. So, the objective of this study is to develop a motor-driven apparatus for removing adhesives efficiently
Demodulation of moire fringes in digital holographic interferometry using an extended Kalman filter.
Ramaiah, Jagadesh; Rastogi, Pramod; Rajshekhar, Gannavarpu
2018-03-10
This paper presents a method for extracting multiple phases from a single moire fringe pattern in digital holographic interferometry. The method relies on component separation using singular value decomposition and an extended Kalman filter for demodulating the moire fringes. The Kalman filter is applied by modeling the interference field locally as a multi-component polynomial phase signal and extracting the associated multiple polynomial coefficients using the state space approach. In addition to phase, the corresponding multiple phase derivatives can be simultaneously extracted using the proposed method. The applicability of the proposed method is demonstrated using simulation and experimental results.
Performance improvement of shunt active power filter based on non-linear least-square approach
DEFF Research Database (Denmark)
Terriche, Yacine
2018-01-01
Nowadays, the shunt active power filters (SAPFs) have become a popular solution for power quality issues. A crucial issue in controlling the SAPFs which is highly correlated with their accuracy, flexibility and dynamic behavior, is generating the reference compensating current (RCC). The synchron......Nowadays, the shunt active power filters (SAPFs) have become a popular solution for power quality issues. A crucial issue in controlling the SAPFs which is highly correlated with their accuracy, flexibility and dynamic behavior, is generating the reference compensating current (RCC......). The synchronous reference frame (SRF) approach is widely used for generating the RCC due to its simplicity and computation efficiency. However, the SRF approach needs precise information of the voltage phase which becomes a challenge under adverse grid conditions. A typical solution to answer this need....... This paper proposes an improved open loop strategy which is unconditionally stable and flexible. The proposed method which is based on non-linear least square (NLS) approach can extract the fundamental voltage and estimates its phase within only half cycle, even in the presence of odd harmonics and dc offset...
Metal-Mesh Optical Filter Technology for Mid IR, Far IR, and Submillimeter, Phase II
National Aeronautics and Space Administration — The innovative, high transmission band-pass filter technology proposed here is an improvement in multilayer metal-mesh filter design and manufacture for the far IR...
Multi-frequency Phase Unwrap from Noisy Data: Adaptive Least Squares Approach
Katkovnik, Vladimir; Bioucas-Dias, José
2010-04-01
Multiple frequency interferometry is, basically, a phase acquisition strategy aimed at reducing or eliminating the ambiguity of the wrapped phase observations or, equivalently, reducing or eliminating the fringe ambiguity order. In multiple frequency interferometry, the phase measurements are acquired at different frequencies (or wavelengths) and recorded using the corresponding sensors (measurement channels). Assuming that the absolute phase to be reconstructed is piece-wise smooth, we use a nonparametric regression technique for the phase reconstruction. The nonparametric estimates are derived from a local least squares criterion, which, when applied to the multifrequency data, yields denoised (filtered) phase estimates with extended ambiguity (periodized), compared with the phase ambiguities inherent to each measurement frequency. The filtering algorithm is based on local polynomial (LPA) approximation for design of nonlinear filters (estimators) and adaptation of these filters to unknown smoothness of the spatially varying absolute phase [9]. For phase unwrapping, from filtered periodized data, we apply the recently introduced robust (in the sense of discontinuity preserving) PUMA unwrapping algorithm [1]. Simulations give evidence that the proposed algorithm yields state-of-the-art performance for continuous as well as for discontinues phase surfaces, enabling phase unwrapping in extraordinary difficult situations when all other algorithms fail.
International Nuclear Information System (INIS)
Gudder, Stan
2010-01-01
An anhomomorphic logic A* is the set of all possible realities for a quantum system. Our main goal is to find the 'actual reality' Φ a element of A* for the system. Reality filters are employed to eliminate unwanted potential realities until only φ a remains. In this paper, we consider three reality filters that are constructed by means of quantum integrals. A quantum measure μ can generate or actualize a Φ element of A* if μ(A) is a quantum integral with respect to φ for a density function f over events A. In this sense, μ is an 'average' of the truth values of φ with weights given by f. We mainly discuss relations between these filters and their existence and uniqueness properties. For example, we show that a quadratic reality generated by a quantum measure is unique. In this case we obtain the unique actual quadratic reality.
Vortex-MEMS filters for wavelength-selective orbital-angular-momentum beam generation
DEFF Research Database (Denmark)
Paul, Sujoy; Lyubopytov, Vladimir; Schumann, Martin F.
2017-01-01
In this paper an on-chip device capable of wavelength-selective generation of vortex beams is demonstrated. The device is realized by integrating a spiral phase-plate onto a MEMS tunable Fabry-Perot filter. This vortex-MEMS filter, being capable of functioning simultaneously in wavelength...
Wien filter for a polarized ions source
International Nuclear Information System (INIS)
Perez A, P.I.
1977-01-01
In order to carry out investigation works about nuclear structure, the Nuclear Center of Mexico has an accelerator Tandem Van de Graff of 12 Mv. Now in this center there is a polarized ions source, in a setting phase, totally constructed in the workshop of the accelerator. This source, supplies an ion beam with a polarization whose propagation direction is not the adequate one for the dispersion and reaction processes wanted to be realized. A filter Wien was used to obtain the correct direction of the polarization vector. The purpose of this work is the study of the filter necessary conditions in order to reach the desirable objective. In the first part some generalities are given about: polarization phenomena, polarized ions source and description of the performance of the Wien filter. In the second part, the problem of the passage of a polarized beam through the filter is tried and solved. Finally, the design and construction of the filter is presented together with the results of the experimentation with the object to justify the suppositions which were taken into consideration in the solution of the filter problem. (author)
The influence of the group delay of digital filters on acoustic decay measurements
DEFF Research Database (Denmark)
Sobreira-Seoane, Manuel A.; Cabo, David Pérez; Jacobsen, Finn
2012-01-01
In this paper the error due to the phase response of digital filters on acoustic decay measurements is analyzed. There are two main sources of errors when an acoustic decay is filtered: the error due to the bandwidth of the filters related to their magnitude response, and the error due to their p...
Morikawa, Naoki; Tanaka, Toshihisa; Islam, Md Rabiul
2018-07-01
Mixed frequency and phase coding (FPC) can achieve the significant increase of the number of commands in steady-state visual evoked potential-based brain-computer interface (SSVEP-BCI). However, the inconsistent phases of the SSVEP over channels in a trial and the existence of non-contributing channels due to noise effects can decrease accurate detection of stimulus frequency. We propose a novel command detection method based on a complex sparse spatial filter (CSSF) by solving ℓ 1 - and ℓ 2,1 -regularization problems for a mixed-coded SSVEP-BCI. In particular, ℓ 2,1 -regularization (aka group sparsification) can lead to the rejection of electrodes that are not contributing to the SSVEP detection. A calibration data based canonical correlation analysis (CCA) and CSSF with ℓ 1 - and ℓ 2,1 -regularization cases were demonstrated for a 16-target stimuli with eleven subjects. The results of statistical test suggest that the proposed method with ℓ 1 - and ℓ 2,1 -regularization significantly achieved the highest ITR. The proposed approaches do not need any reference signals, automatically select prominent channels, and reduce the computational cost compared to the other mixed frequency-phase coding (FPC)-based BCIs. The experimental results suggested that the proposed method can be usable implementing BCI effectively with reduce visual fatigue. Copyright © 2018 Elsevier B.V. All rights reserved.
Passive target tracking using marginalized particle filter
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A marginalized particle filtering(MPF)approach is proposed for target tracking under the background of passive measurement.Essentially,the MPF is a combination of particle filtering technique and Kalman filter.By making full use of marginalization,the distributions of the tractable linear part of the total state variables are updated analytically using Kalman filter,and only the lower-dimensional nonlinear state variable needs to be dealt with using particle filter.Simulation studies are performed on an illustrative example,and the results show that the MPF method leads to a significant reduction of the tracking errors when compared with the direct particle implementation.Real data test results also validate the effectiveness of the presented method.
Blended particle filters for large-dimensional chaotic dynamical systems
Majda, Andrew J.; Qi, Di; Sapsis, Themistoklis P.
2014-01-01
A major challenge in contemporary data science is the development of statistically accurate particle filters to capture non-Gaussian features in large-dimensional chaotic dynamical systems. Blended particle filters that capture non-Gaussian features in an adaptively evolving low-dimensional subspace through particles interacting with evolving Gaussian statistics on the remaining portion of phase space are introduced here. These blended particle filters are constructed in this paper through a mathematical formalism involving conditional Gaussian mixtures combined with statistically nonlinear forecast models compatible with this structure developed recently with high skill for uncertainty quantification. Stringent test cases for filtering involving the 40-dimensional Lorenz 96 model with a 5-dimensional adaptive subspace for nonlinear blended filtering in various turbulent regimes with at least nine positive Lyapunov exponents are used here. These cases demonstrate the high skill of the blended particle filter algorithms in capturing both highly non-Gaussian dynamical features as well as crucial nonlinear statistics for accurate filtering in extreme filtering regimes with sparse infrequent high-quality observations. The formalism developed here is also useful for multiscale filtering of turbulent systems and a simple application is sketched below. PMID:24825886
Directory of Open Access Journals (Sweden)
O. W. Roberts
2014-12-01
Full Text Available Recent observations of astrophysical magnetic fields have shown the presence of fluctuations being wave-like (propagating in the plasma frame and those described as being structure-like (advected by the plasma bulk velocity. Typically with single-spacecraft missions it is impossible to differentiate between these two fluctuations, due to the inherent spatio-temporal ambiguity associated with a single point measurement. However missions such as Cluster which contain multiple spacecraft have allowed for temporal and spatial changes to be resolved, using techniques such as k filtering. While this technique does not assume Taylor's hypothesis it requires both weak stationarity of the time series and that the fluctuations can be described by a superposition of plane waves with random phases. In this paper we test whether the method can cope with a synthetic signal which is composed of a combination of non-random-phase coherent structures with a mean radius d and a mean separation λ, as well as plane waves with random phase.
A New Filtering Algorithm Utilizing Radial Velocity Measurement
Institute of Scientific and Technical Information of China (English)
LIU Yan-feng; DU Zi-cheng; PAN Quan
2005-01-01
Pulse Doppler radar measurements consist of range, azimuth, elevation and radial velocity. Most of the radar tracking algorithms in engineering only utilize position measurement. The extended Kalman filter with radial velocity measureneut is presented, then a new filtering algorithm utilizing radial velocity measurement is proposed to improve tracking results and the theoretical analysis is also given. Simulation results of the new algorithm, converted measurement Kalman filter, extended Kalman filter are compared. The effectiveness of the new algorithm is verified by simulation results.
The cosmological constant filter without big bang singularity
International Nuclear Information System (INIS)
Bauer, Florian
2011-01-01
In the recently proposed cosmological constant (CC) filter mechanism based on modified gravity in the Palatini formalism, gravity in the radiation, matter and late-time de Sitter eras is insensitive to energy sources with the equation of state -1. This implies that finite vacuum energy shifts from phase transitions are filtered out too. In this work, we investigate the CC filter model at very early times. We find that the initial big bang singularity is replaced by a cosmic bounce, where the matter energy density and the curvature are finite. In a certain case, this finiteness can be already observed on the algebraic level. (paper)
Unified Digital Periodic Signal Filters for Power Converter Systems
DEFF Research Database (Denmark)
Yang, Yongheng; Xin, Zhen; Zhou, Keliang
2017-01-01
Periodic signal controllers like repetitive and resonant controllers have demonstrated much potential in the control of power electronic converters, where periodic signals (e.g., ac voltages and currents) can be precisely regulated to follow references. Beyond the control of periodic signals, ac...... signal processing (e.g., in synchronization and pre-filtering) is also very important for power converter systems. Hence, this paper serves to unify digital periodic signal filters so as to maximize their roles in power converter systems (e.g., enhance the control of ac signals). The unified digital...... periodic signal filters behave like a comb filter, but it can also be configured to selectively filter out the harmonics of interest (e.g., the odd-order harmonics in single-phase power converter systems). Moreover, a virtual variable-sampling-frequency unit delay that enables frequency adaptive periodic...
Directory of Open Access Journals (Sweden)
Jianke Li
2014-01-01
Full Text Available Compared with L-type filter, LCL-type filter is more suitable for high-power low-switching frequency applications with reducing the inductance, improving dynamic performance. However, the parameter design for the LCL filter is more complex due to the influence of the controller response performance of the converter. If the harmonic current around switching frequency can be fully suppressed, it is possible for inverter to decrease the total inductance as well as the size and the cost. In this paper, the model of the LCL filter is analyzed and numerical algorithms are adopted to analyze the stability of the closed-loop control system and stable regions are deduced with different parameters of LCL filter. Then, the minimum sampling frequencies are deduced with different conditions. Simulation and experimental results are provided to validate the research on the generating mechanism for the unstable region of sampling frequency.
Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming
DEFF Research Database (Denmark)
Bañas, Andrew Rafael; Palima, Darwin; Glückstad, Jesper
2012-01-01
, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser...
An R-peak detection method that uses an SVD filter and a search back system.
Jung, Woo-Hyuk; Lee, Sang-Goog
2012-12-01
In this paper, we present a method for detecting the R-peak of an ECG signal by using an singular value decomposition (SVD) filter and a search back system. The ECG signal was detected in two phases: the pre-processing phase and the decision phase. The pre-processing phase consisted of the stages for the SVD filter, Butterworth High Pass Filter (HPF), moving average (MA), and squaring, whereas the decision phase consisted of a single stage that detected the R-peak. In the pre-processing phase, the SVD filter removed noise while the Butterworth HPF eliminated baseline wander. The MA removed the remaining noise of the signal that had gone through the SVD filter to make the signal smooth, and squaring played a role in strengthening the signal. In the decision phase, the threshold was used to set the interval before detecting the R-peak. When the latest R-R interval (RRI), suggested by Hamilton et al., was greater than 150% of the previous RRI, the method of detecting the R-peak in such an interval was modified to be 150% or greater than the smallest interval of the two most latest RRIs. When the modified search back system was used, the error rate of the peak detection decreased to 0.29%, compared to 1.34% when the modified search back system was not used. Consequently, the sensitivity was 99.47%, the positive predictivity was 99.47%, and the detection error was 1.05%. Furthermore, the quality of the signal in data with a substantial amount of noise was improved, and thus, the R-peak was detected effectively. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.
Zhang, Tao; Gao, Feng; Muhamedsalih, Hussam; Lou, Shan; Martin, Haydn; Jiang, Xiangqian
2018-03-20
The phase slope method which estimates height through fringe pattern frequency and the algorithm which estimates height through the fringe phase are the fringe analysis algorithms widely used in interferometry. Generally they both extract the phase information by filtering the signal in frequency domain after Fourier transform. Among the numerous papers in the literature about these algorithms, it is found that the design of the filter, which plays an important role, has never been discussed in detail. This paper focuses on the filter design in these algorithms for wavelength scanning interferometry (WSI), trying to optimize the parameters to acquire the optimal results. The spectral characteristics of the interference signal are analyzed first. The effective signal is found to be narrow-band (near single frequency), and the central frequency is calculated theoretically. Therefore, the position of the filter pass-band is determined. The width of the filter window is optimized with the simulation to balance the elimination of the noise and the ringing of the filter. Experimental validation of the approach is provided, and the results agree very well with the simulation. The experiment shows that accuracy can be improved by optimizing the filter design, especially when the signal quality, i.e., the signal noise ratio (SNR), is low. The proposed method also shows the potential of improving the immunity to the environmental noise by adapting the signal to acquire the optimal results through designing an adaptive filter once the signal SNR can be estimated accurately.
Herzing, Andrew A; Ro, Hyun Wook; Soles, Christopher L; DeLongchamp, Dean M
2013-09-24
The morphology of the active layer in an organic photovoltaic bulk-heterojunction device is controlled by the extent and nature of phase separation during processing. We have studied the effects of fullerene crystallinity during heat treatment in model structures consisting of a layer of poly(3-hexylthiophene) (P3HT) sandwiched between two layers of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Utilizing a combination of focused ion-beam milling and energy-filtered transmission electron microscopy, we monitored the local changes in phase distribution as a function of annealing time at 140 °C. In both cases, dissolution of PCBM within the surrounding P3HT was directly visualized and quantitatively described. In the absence of crystalline PCBM, the overall phase distribution remained stable after intermediate annealing times up to 60 s, whereas microscale PCBM aggregates were observed after annealing for 300 s. Aggregate growth proceeded vertically from the substrate interface via uptake of PCBM from the surrounding region, resulting in a large PCBM-depleted region in their vicinity. When precrystallized PCBM was present, amorphous PCBM was observed to segregate from the intermediate P3HT layer and ripen the crystalline PCBM underneath, owing to the far lower solubility of crystalline PCBM within P3HT. This process occurred rapidly, with segregation already evident after annealing for 10 s and with uptake of nearly all of the amorphous PCBM by the crystalline layer after 60 s. No microscale aggregates were observed in the precrystallized system, even after annealing for 300 s.
Filtering Redundant Data from RFID Data Streams
Directory of Open Access Journals (Sweden)
Hazalila Kamaludin
2016-01-01
Full Text Available Radio Frequency Identification (RFID enabled systems are evolving in many applications that need to know the physical location of objects such as supply chain management. Naturally, RFID systems create large volumes of duplicate data. As the duplicate data wastes communication, processing, and storage resources as well as delaying decision-making, filtering duplicate data from RFID data stream is an important and challenging problem. Existing Bloom Filter-based approaches for filtering duplicate RFID data streams are complex and slow as they use multiple hash functions. In this paper, we propose an approach for filtering duplicate data from RFID data streams. The proposed approach is based on modified Bloom Filter and uses only a single hash function. We performed extensive empirical study of the proposed approach and compared it against the Bloom Filter, d-Left Time Bloom Filter, and the Count Bloom Filter approaches. The results show that the proposed approach outperforms the baseline approaches in terms of false positive rate, execution time, and true positive rate.
Sensory Pollution from Bag Filters, Carbon Filters and Combinations
DEFF Research Database (Denmark)
Bekö, Gabriel; Clausen, Geo; Weschler, Charles J.
2008-01-01
by an upstream pre-filter (changed monthly), an EU7 filter protected by an upstream activated carbon (AC) filter, and EU7 filters with an AC filter either downstream or both upstream and downstream. In addition, two types of stand-alone combination filters were evaluated: a bag-type fiberglass filter...... that contained AC and a synthetic fiber cartridge filter that contained AC. Air that had passed through used filters was most acceptable for those sets in which an AC filter was used downstream of the particle filter. Comparable air quality was achieved with the stand-alone bag filter that contained AC...
Schweser, Ferdinand; Dwyer, Michael G.; Deistung, Andreas; Reichenbach, Jürgen R.; Zivadinov, Robert
2013-10-01
The assessment of abnormal accumulation of tissue iron in the basal ganglia nuclei and in white matter plaques using the gradient echo magnetic resonance signal phase has become a research focus in many neurodegenerative diseases such as multiple sclerosis or Parkinson’s disease. A common and natural approach is to calculate the mean high-pass-filtered phase of previously delineated brain structures. Unfortunately, the interpretation of such an analysis requires caution: in this paper we demonstrate that regional gray matter atrophy, which is concomitant with many neurodegenerative diseases, may itself directly result in a phase shift seemingly indicative of increased iron concentration even without any real change in the tissue iron concentration. Although this effect is relatively small results of large-scale group comparisons may be driven by anatomical changes rather than by changes of the iron concentration.
No influence of positive emotion on orbitofrontal reality filtering: relevance for confabulation
Directory of Open Access Journals (Sweden)
Maria Chiara eLiverani
2016-05-01
Full Text Available Orbitofrontal reality filtering is a mechanism that allows us to keep thought and behavior in phase with reality. Its failure induces reality confusion with confabulation and disorientation. Confabulations have been claimed to have a positive emotional bias, suggesting that they emanate from a tendency to embellish the situation of a handicap. Here we tested the influence of positive emotion on orbitofrontal reality filtering in healthy subjects using a paradigm validated in reality confusing patients and with a known electrophysiological signature, a frontal positivity at 200-400 ms after memory evocation. Subjects made two continuous recognition tasks (two runs, composed of the same set of neutral and positive pictures, but arranged in different order. In both runs, participants had to indicate pictures repetitions within, and only within, the ongoing run. The first run measures learning and recognition. The second run, where all items are familiar, requires orbitofrontal reality filtering to avoid false positive responses. High-density evoked potentials were recorded from nineteen healthy subjects during completion of the task. Performance was more accurate and faster on neutral than positive pictures in both runs and all conditions. Evoked potential correlates of emotion and reality filtering occurred at 260-350 ms but dissociated in terms of amplitudes and topography. In both runs, positive stimuli evoked a more negative frontal potential than neutral ones. In the second run, the frontal positivity characteristic of reality filtering was separately, and to the same degree, expressed for positive and neutral stimuli. We conclude that orbitofrontal reality filtering, the ability to place oneself correctly in time and space, is not influenced by emotional positivity of the processed material.
Qualification of box HEPA filters for nuclear applications
International Nuclear Information System (INIS)
Bergman, W.; Larsen, G.; Wilson, K.; Rainer, F.
1995-03-01
We have successfully completed qualification tests on high efficiency particulate air (HEPA) filters that are encapsulated within a box and manufactured by American Air Filters. The qualification tests are required by the American Society of Mechanical Engineers Standard ASME N509 and the U.S. Military Standard MIL-F-51068 for HEPA filters to be used in nuclear applications. The qualification tests specify minimum filter efficiencies following exposure to heated air, overpressure, and rough handling. Prior to this study, no box HEPA filters from any manufacturer had been qualified despite their wide-spread use in Department of Energy (DOE) facilities. Box HEPA filters are not addressed in any of the existing HEPA standards and only briefly discussed in the Nuclear Air Cleaning Handbook
Directory of Open Access Journals (Sweden)
Ming-Hung Chen
2015-01-01
Full Text Available This paper proposes a new adaptive filter for wind generators that combines instantaneous reactive power compensation technology and current prediction controller, and therefore this system is characterized by low harmonic distortion, high power factor, and small DC-link voltage variations during load disturbances. The performance of the system was first simulated using MATLAB/Simulink, and the possibility of an adaptive digital low-pass filter eliminating current harmonics was confirmed in steady and transient states. Subsequently, a digital signal processor was used to implement an active power filter. The experimental results indicate, that for the rated operation of 2 kVA, the system has a total harmonic distortion of current less than 5.0% and a power factor of 1.0 on the utility side. Thus, the transient performance of the adaptive filter is superior to the traditional digital low-pass filter and is more economical because of its short computation time compared with other types of adaptive filters.
Chen, Ming-Hung
2015-01-01
This paper proposes a new adaptive filter for wind generators that combines instantaneous reactive power compensation technology and current prediction controller, and therefore this system is characterized by low harmonic distortion, high power factor, and small DC-link voltage variations during load disturbances. The performance of the system was first simulated using MATLAB/Simulink, and the possibility of an adaptive digital low-pass filter eliminating current harmonics was confirmed in steady and transient states. Subsequently, a digital signal processor was used to implement an active power filter. The experimental results indicate, that for the rated operation of 2 kVA, the system has a total harmonic distortion of current less than 5.0% and a power factor of 1.0 on the utility side. Thus, the transient performance of the adaptive filter is superior to the traditional digital low-pass filter and is more economical because of its short computation time compared with other types of adaptive filters.
Integrated programmable photonic filter on the silicon -on- insulator platform
DEFF Research Database (Denmark)
Liao, Shasha; Ding, Yunhong; Peucheret, Christophe
2014-01-01
We propose and demonstrate a silicon - on - insulator (SOI) on - chip programmable filter based on a four - tap finite impulse response structure. The photonic filter is programmable thanks to amplitude and phase modulation of each tap controlled by thermal heater s. We further demonstrate...... the tunability of the filter central wavelength, bandwidth and variable passband shape. The tuning range of the central wavelength is at least 42% of the free spectral range. The bandwidth tuning range is at least half of the free spectral range. Our scheme has distinct advantages of compactness, capability...
Ultrathin metal-semiconductor-metal resonator for angle invariant visible band transmission filters
International Nuclear Information System (INIS)
Lee, Kyu-Tae; Seo, Sungyong; Yong Lee, Jae; Jay Guo, L.
2014-01-01
We present transmission visible wavelength filters based on strong interference behaviors in an ultrathin semiconductor material between two metal layers. The proposed devices were fabricated on 2 cm × 2 cm glass substrate, and the transmission characteristics show good agreement with the design. Due to a significantly reduced light propagation phase change associated with the ultrathin semiconductor layer and the compensation in phase shift of light reflecting from the metal surface, the filters show an angle insensitive performance up to ±70°, thus, addressing one of the key challenges facing the previously reported photonic and plasmonic color filters. This principle, described in this paper, can have potential for diverse applications ranging from color display devices to the image sensors.
Fabrication of porous zirconia using filter paper template
International Nuclear Information System (INIS)
Deng Yuhua; Wei Pan
2005-01-01
In this work, porous zirconia ceramic was synthesized using filter papers as a template. Special attention is paid to whether the structural of the filter paper can be transferred to the zirconia structure. Microstructure of so synthesized porous zirconia was observed with SEM and the phase was determined by XRD. The surface area and the pore were investigated with an automatic volumetric sorption analyzer. It has been found that the morphology of the template transmit to the porous zirconia quite well. (orig.)
Grobler, T. L.; Stewart, A. J.; Wijnholds, S. J.; Kenyon, J. S.; Smirnov, O. M.
2016-09-01
This is the third installment in a series of papers in which we investigate calibration artefacts. Calibration artefacts (also known as ghosts or spurious sources) are created when we calibrate with an incomplete model. In the first two papers of this series, we developed a mathematical framework which enabled us to study the ghosting mechanism itself. An interesting concomitant of the second paper was that ghosts appear in symmetrical pairs. This could possibly account for spurious symmetrization. Spurious symmetrization refers to the appearance of a spurious source (the antighost) symmetrically opposite an unmodelled source around a modelled source. The analysis in the first two papers indicates that the antighost is usually very faint, in particular, when a large number of antennas are used. This suggests that spurious symmetrization will mainly occur at an almost undetectable flux level. In this paper, we show that phase-only calibration produces an antighost that is N-times (where N denotes the number of antennas in the array) as bright as the one produced by phase and amplitude calibration and that this already bright ghost can be further amplified by the primary beam correction.
Stochastic processes and filtering theory
Jazwinski, Andrew H
1970-01-01
This unified treatment of linear and nonlinear filtering theory presents material previously available only in journals, and in terms accessible to engineering students. Its sole prerequisites are advanced calculus, the theory of ordinary differential equations, and matrix analysis. Although theory is emphasized, the text discusses numerous practical applications as well.Taking the state-space approach to filtering, this text models dynamical systems by finite-dimensional Markov processes, outputs of stochastic difference, and differential equations. Starting with background material on probab
Leukoreduction of platelet concentrates using a 'polishing' filter
van der Meer, P. F.; Pietersz, R. N.; Reesink, H. W.
2000-01-01
BACKGROUND AND OBJECTIVES: Filters for removal of leukocytes from platelet concentrates (PCs) usually have a large volume to guarantee sufficient leukoreduction. In this study, a small filter, with a volume of only 8 ml and therefore minimal platelet loss, for leukoreduction of PCs was investigated.
All-optical clock recovery of NRZ-DPSK signals using optical resonator-type filters
DEFF Research Database (Denmark)
Peucheret, Christophe; Seoane, Jorge; Ji, Hua
2009-01-01
It is shown how introducing a limited rise time to the driving signal enables all-optical clock recovery of NRZ-DPSK signals generated using a phase modulator. A Fabry-Perot filter is used to generate the optical clock.......It is shown how introducing a limited rise time to the driving signal enables all-optical clock recovery of NRZ-DPSK signals generated using a phase modulator. A Fabry-Perot filter is used to generate the optical clock....
Removing Pathogens Using Nano-Ceramic-Fiber Filters
Tepper, Frederick; Kaledin, Leonid
2005-01-01
A nano-aluminum-oxide fiber of only 2 nanometers in diameter was used to develop a ceramic-fiber filter. The fibers are electropositive and, when formulated into a filter material (NanoCeram(TradeMark)), would attract electro-negative particles such as bacteria and viruses. The ability to detect and then remove viruses as well as bacteria is of concern in space cabins since they may be carried onboard by space crews. Moreover, an improved filter was desired that would polish the effluent from condensed moisture and wastewater, producing potable drinking water. A laboratory- size filter was developed that was capable of removing greater than 99.9999 percent of bacteria and virus. Such a removal was achieved at flow rates hundreds of times greater than those through ultraporous membranes that remove particles by sieving. Because the pore size of the new filter was rather large as compared to ultraporous membranes, it was found to be more resistant to clogging. Additionally, a full-size cartridge is being developed that is capable of serving a full space crew. During this ongoing effort, research demonstrated that the filter media was a very efficient adsorbent for DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and endotoxins. Since the adsorption is based on the charge of the macromolecules, there is also a potential for separating proteins and other particulates on the basis of their charge differences. The separation of specific proteins is a major new thrust of biotechnology. The principal application of NanoCeram filters is based on their ability to remove viruses from water. The removal of more than 99.9999 percent of viruses was achieved by a NanoCeram polishing filter added to the effluent of an existing filtration device. NanoCeram is commercially available in laboratory-size filter discs and in the form of a syringe filter. The unique characteristic of the filter can be demonstrated by its ability to remove particulate dyes such as Metanyl yellow. Its
Active phase correction of high resolution silicon photonic arrayed waveguide gratings.
Gehl, M; Trotter, D; Starbuck, A; Pomerene, A; Lentine, A L; DeRose, C
2017-03-20
Arrayed waveguide gratings provide flexible spectral filtering functionality for integrated photonic applications. Achieving narrow channel spacing requires long optical path lengths which can greatly increase the footprint of devices. High index contrast waveguides, such as those fabricated in silicon-on-insulator wafers, allow tight waveguide bends which can be used to create much more compact designs. Both the long optical path lengths and the high index contrast contribute to significant optical phase error as light propagates through the device. Therefore, silicon photonic arrayed waveguide gratings require active or passive phase correction following fabrication. Here we present the design and fabrication of compact silicon photonic arrayed waveguide gratings with channel spacings of 50, 10 and 1 GHz. The largest device, with 11 channels of 1 GHz spacing, has a footprint of only 1.1 cm2. Using integrated thermo-optic phase shifters, the phase error is actively corrected. We present two methods of phase error correction and demonstrate state-of-the-art cross-talk performance for high index contrast arrayed waveguide gratings. As a demonstration of possible applications, we perform RF channelization with 1 GHz resolution. Additionally, we generate unique spectral filters by applying non-zero phase offsets calculated by the Gerchberg Saxton algorithm.
HEPA filter concerns - an overview
Energy Technology Data Exchange (ETDEWEB)
Leonard, J.F. [Department of Energy, Washington, DC (United States)
1995-02-01
The U.S. Department of Energy (DOE) recently initiated a complete review of the DOE High Efficiency Particulate Air (HEPA) Filter Program to identify areas for improvement. Although this process is currently ongoing, various issues and problems have already been identified for action that not only impacts the DOE HEPA filter program, but potentially the national and international air cleaning community as well. This paper briefly reviews a few of those concerns that may be of interest, and discusses actions initiated by the DOE to address the associated issues and problems. Issues discussed include: guidance standards, in-place testing, specifications, Test Facilities, portable units, vacuum cleaners, substitute aerosols, filter efficiencies, aging/shelf life/service life, fire suppression, handbook, Quality Products List (QPL), QA testing, and evaluations.
Filtering of a Markov Jump Process with Counting Observations
International Nuclear Information System (INIS)
Ceci, C.; Gerardi, A.
2000-01-01
This paper concerns the filtering of an R d -valued Markov pure jump process when only the total number of jumps are observed. Strong and weak uniqueness for the solutions of the filtering equations are discussed
A Game Theoretic Fault Detection Filter
Chung, Walter H.; Speyer, Jason L.
1995-01-01
The fault detection process is modelled as a disturbance attenuation problem. The solution to this problem is found via differential game theory, leading to an H(sub infinity) filter which bounds the transmission of all exogenous signals save the fault to be detected. For a general class of linear systems which includes some time-varying systems, it is shown that this transmission bound can be taken to zero by simultaneously bringing the sensor noise weighting to zero. Thus, in the limit, a complete transmission block can he achieved, making the game filter into a fault detection filter. When we specialize this result to time-invariant system, it is found that the detection filter attained in the limit is identical to the well known Beard-Jones Fault Detection Filter. That is, all fault inputs other than the one to be detected (the "nuisance faults") are restricted to an invariant subspace which is unobservable to a projection on the output. For time-invariant systems, it is also shown that in the limit, the order of the state-space and the game filter can be reduced by factoring out the invariant subspace. The result is a lower dimensional filter which can observe only the fault to be detected. A reduced-order filter can also he generated for time-varying systems, though the computational overhead may be intensive. An example given at the end of the paper demonstrates the effectiveness of the filter as a tool for fault detection and identification.
Guenther tulip retrievable filter: why, when and how?
International Nuclear Information System (INIS)
Millward, S.F.
2001-01-01
Nonpermanent inferior vena cava (IVC) filters can be subdivided into temporary and retrievable filters. Temporary filters are attached to a catheter or guide wire. They have been extensively used in Europe, mainly for the prevention of pulmonary embolism (PE) during thrombolytic treatment for lower extremity deep vein thrombosis (DVT). However, the reported rate of recurrent PE in patients protected with a temporary filter appears to be similar, or even higher, than that seen in North American studies of thrombolytic treatment of DVT when no filter was used. Results obtained with temporary filters in other clinical situations have also been somewhat discouraging. Consequently, research efforts in North America with nonpermanent filters appear to have shifted predominantly to the study of retrievable filters. Retrievable filters, such as the Guenther Tulip filter (William Cook Europe, Bjaeverskov, Denmark) (Fig. 1), are permanent filters with a design feature (usually a hook that can be snared) to permit retrieval. They have an advantage over temporary filters in that they can be either left in place permanently or retrieved, whichever is most appropriate for a given patient. The Guenther Tulip filter is currently the only approved device from this versatile new class of retrievable filters. ln this article, I hope to offer some practical points on why, when and how the device should be used. (author)
Human attention filters for single colors
Sun, Peng; Chubb, Charles; Wright, Charles E.; Sperling, George
2016-01-01
The visual images in the eyes contain much more information than the brain can process. An important selection mechanism is feature-based attention (FBA). FBA is best described by attention filters that specify precisely the extent to which items containing attended features are selectively processed and the extent to which items that do not contain the attended features are attenuated. The centroid-judgment paradigm enables quick, precise measurements of such human perceptual attention filters, analogous to transmission measurements of photographic color filters. Subjects use a mouse to locate the centroid—the center of gravity—of a briefly displayed cloud of dots and receive precise feedback. A subset of dots is distinguished by some characteristic, such as a different color, and subjects judge the centroid of only the distinguished subset (e.g., dots of a particular color). The analysis efficiently determines the precise weight in the judged centroid of dots of every color in the display (i.e., the attention filter for the particular attended color in that context). We report 32 attention filters for single colors. Attention filters that discriminate one saturated hue from among seven other equiluminant distractor hues are extraordinarily selective, achieving attended/unattended weight ratios >20:1. Attention filters for selecting a color that differs in saturation or lightness from distractors are much less selective than attention filters for hue (given equal discriminability of the colors), and their filter selectivities are proportional to the discriminability distance of neighboring colors, whereas in the same range hue attention-filter selectivity is virtually independent of discriminabilty. PMID:27791040
Phase ambiguity resolution for offset QPSK modulation systems
Nguyen, Tien M. (Inventor)
1991-01-01
A demodulator for Offset Quaternary Phase Shift Keyed (OQPSK) signals modulated with two words resolves eight possible combinations of phase ambiguity which may produce data error by first processing received I(sub R) and Q(sub R) data in an integrated carrier loop/symbol synchronizer using a digital Costas loop with matched filters for correcting four of eight possible phase lock errors, and then the remaining four using a phase ambiguity resolver which detects the words to not only reverse the received I(sub R) and Q(sub R) data channels, but to also invert (complement) the I(sub R) and/or Q(sub R) data, or to at least complement the I(sub R) and Q(sub R) data for systems using nontransparent codes that do not have rotation direction ambiguity.
Analysis of moiré fringes by Wiener filtering: An extension to the Fourier method
International Nuclear Information System (INIS)
Harasse, Sébastien; Yashiro, Wataru; Momose, Atsushi
2012-01-01
In X-ray Talbot interferometry, tilting the phase grating with respect to the absorption grating results in the formation of spatial fringes. The analysis of this moiré pattern, classically performed by the Fourier method, allows the extraction of the sample phase shift information from a single image. In this context, an extension to the Fourier method is proposed. The filter used to extract the fringe information is chosen optimally in the least-squares sense, given models for the zeroth and first order modes, noise and the modulation transfer function. The latter is obtained by measuring the detector response to moiré fringes with increasing frequencies. The obtained Wiener filter allows a better reconstruction of the phase information at all fringe frequencies, compared to the usual box or gaussian filters. This is demonstrated quantitatively by experiments using synchrotron radiation.
Lemieux, Chantal L; Collin, Charles A; Nelson, Elizabeth A
2015-02-01
In two experiments, we examined the effects of varying the spatial frequency (SF) content of face images on eye movements during the learning and testing phases of an old/new recognition task. At both learning and testing, participants were presented with face stimuli band-pass filtered to 11 different SF bands, as well as an unfiltered baseline condition. We found that eye movements varied significantly as a function of SF. Specifically, the frequency of transitions between facial features showed a band-pass pattern, with more transitions for middle-band faces (≈5-20 cycles/face) than for low-band (≈20 cpf) ones. These findings were similar for the learning and testing phases. The distributions of transitions across facial features were similar for the middle-band, high-band, and unfiltered faces, showing a concentration on the eyes and mouth; conversely, low-band faces elicited mostly transitions involving the nose and nasion. The eye movement patterns elicited by low, middle, and high bands are similar to those previous researchers have suggested reflect holistic, configural, and featural processing, respectively. More generally, our results are compatible with the hypotheses that eye movements are functional, and that the visual system makes flexible use of visuospatial information in face processing. Finally, our finding that only middle spatial frequencies yielded the same number and distribution of fixations as unfiltered faces adds more evidence to the idea that these frequencies are especially important for face recognition, and reveals a possible mediator for the superior performance that they elicit.
Filters in topology optimization based on Helmholtz‐type differential equations
DEFF Research Database (Denmark)
Lazarov, Boyan Stefanov; Sigmund, Ole
2011-01-01
The aim of this paper is to apply a Helmholtz‐type partial differential equation as an alternative to standard density filtering in topology optimization problems. Previously, this approach has been successfully applied as a sensitivity filter. The usual filtering techniques in topology...... from the neighbor subdomains is an expensive operation. The proposed filter technique requires only mesh information necessary for the finite element discretization of the problem. The main idea is to define the filtered variable implicitly as a solution of a Helmholtz‐type differential equation...
International Nuclear Information System (INIS)
Sandoval, Miguel A.; Fuentes, Rosalba; Walsh, Frank C.; Nava, José L.; Ponce de León, Carlos
2016-01-01
Highlights: • Computational fluid dynamic simulations in a filter-press stack of three cells. • The fluid velocity was different in each cell due to local turbulence. • The upper cell link pipe of the filter press cell acts as a fluid mixer. • The fluid behaviour tends towards a continuous mixing flow pattern. • Close agreement between simulations and experimental data was achieved. - Abstract: Computational fluid dynamics (CFD) simulations were carried out for single-phase flow in a pre-pilot filter press flow reactor with a stack of three cells. Velocity profiles and streamlines were obtained by solving the Reynolds-Averaged Navier-Stokes (RANS) equations with a standard k − ε turbulence model. The flow behaviour shows the appearance of jet flow at the entrance to each cell. At lengths from 12 to 15 cm along the cells channels, a plug flow pattern is developed at all mean linear flow rates studied here, 1.2 ≤ u ≤ 2.1 cm s −1 . The magnitude of the velocity profiles in each cell was different, due to the turbulence generated by the change of flow direction in the last fluid manifold. Residence time distribution (RTD) simulations indicated that the fluid behaviour tends towards a continuous mixing flow pattern, owing to flow at the output of each cell across the upper cell link pipe, which acts as a mixer. Close agreement between simulations and experimental RTD was obtained.
Binocular contrast-gain control for natural scenes: Image structure and phase alignment.
Huang, Pi-Chun; Dai, Yu-Ming
2018-05-01
In the context of natural scenes, we applied the pattern-masking paradigm to investigate how image structure and phase alignment affect contrast-gain control in binocular vision. We measured the discrimination thresholds of bandpass-filtered natural-scene images (targets) under various types of pedestals. Our first experiment had four pedestal types: bandpass-filtered pedestals, unfiltered pedestals, notch-filtered pedestals (which enabled removal of the spatial frequency), and misaligned pedestals (which involved rotation of unfiltered pedestals). Our second experiment featured six types of pedestals: bandpass-filtered, unfiltered, and notch-filtered pedestals, and the corresponding phase-scrambled pedestals. The thresholds were compared for monocular, binocular, and dichoptic viewing configurations. The bandpass-filtered pedestal and unfiltered pedestals showed classic dipper shapes; the dipper shapes of the notch-filtered, misaligned, and phase-scrambled pedestals were weak. We adopted a two-stage binocular contrast-gain control model to describe our results. We deduced that the phase-alignment information influenced the contrast-gain control mechanism before the binocular summation stage and that the phase-alignment information and structural misalignment information caused relatively strong divisive inhibition in the monocular and interocular suppression stages. When the pedestals were phase-scrambled, the elimination of the interocular suppression processing was the most convincing explanation of the results. Thus, our results indicated that both phase-alignment information and similar image structures cause strong interocular suppression. Copyright © 2018 Elsevier Ltd. All rights reserved.
Law, Kody
2016-01-06
This talk will pertain to the filtering of partially observed diffusions, with discrete-time observations. It is assumed that only biased approximations of the diffusion can be obtained, for choice of an accuracy parameter indexed by l. A multilevel estimator is proposed, consisting of a telescopic sum of increment estimators associated to the successive levels. The work associated to O( 2) mean-square error between the multilevel estimator and average with respect to the filtering distribution is shown to scale optimally, for example as O( 2) for optimal rates of convergence of the underlying diffusion approximation. The method is illustrated on some toy examples as well as estimation of interest rate based on real S&P 500 stock price data.
Half-metal phases in a quantum wire with modulated spin-orbit interaction
Cabra, D. C.; Rossini, G. L.; Ferraz, A.; Japaridze, G. I.; Johannesson, H.
2017-11-01
We propose a spin filter device based on the interplay of a modulated spin-orbit interaction and a uniform external magnetic field acting on a quantum wire. Half-metal phases, where electrons with only a selected spin polarization exhibit ballistic conductance, can be tuned by varying the magnetic field. These half-metal phases are proven to be robust against electron-electron repulsive interactions. Our results arise from a combination of explicit band diagonalization, bosonization techniques, and extensive density matrix renormalization group computations.
Correlation of Spatially Filtered Dynamic Speckles in Distance Measurement Application
International Nuclear Information System (INIS)
Semenov, Dmitry V.; Nippolainen, Ervin; Kamshilin, Alexei A.; Miridonov, Serguei V.
2008-01-01
In this paper statistical properties of spatially filtered dynamic speckles are considered. This phenomenon was not sufficiently studied yet while spatial filtering is an important instrument for speckles velocity measurements. In case of spatial filtering speckle velocity information is derived from the modulation frequency of filtered light power which is measured by photodetector. Typical photodetector output is represented by a narrow-band random noise signal which includes non-informative intervals. Therefore more or less precious frequency measurement requires averaging. In its turn averaging implies uncorrelated samples. However, conducting research we found that correlation is typical property not only of dynamic speckle patterns but also of spatially filtered speckles. Using spatial filtering the correlation is observed as a response of measurements provided to the same part of the object surface or in case of simultaneously using several adjacent photodetectors. Found correlations can not be explained using just properties of unfiltered dynamic speckles. As we demonstrate the subject of this paper is important not only from pure theoretical point but also from the point of applied speckle metrology. E.g. using single spatial filter and an array of photodetector can greatly improve accuracy of speckle velocity measurements
A Low Cost Structurally Optimized Design for Diverse Filter Types
Kazmi, Majida; Aziz, Arshad; Akhtar, Pervez; Ikram, Nassar
2016-01-01
A wide range of image processing applications deploys two dimensional (2D)-filters for performing diversified tasks such as image enhancement, edge detection, noise suppression, multi scale decomposition and compression etc. All of these tasks require multiple type of 2D-filters simultaneously to acquire the desired results. The resource hungry conventional approach is not a viable option for implementing these computationally intensive 2D-filters especially in a resource constraint environment. Thus it calls for optimized solutions. Mostly the optimization of these filters are based on exploiting structural properties. A common shortcoming of all previously reported optimized approaches is their restricted applicability only for a specific filter type. These narrow scoped solutions completely disregard the versatility attribute of advanced image processing applications and in turn offset their effectiveness while implementing a complete application. This paper presents an efficient framework which exploits the structural properties of 2D-filters for effectually reducing its computational cost along with an added advantage of versatility for supporting diverse filter types. A composite symmetric filter structure is introduced which exploits the identities of quadrant and circular T-symmetries in two distinct filter regions simultaneously. These T-symmetries effectually reduce the number of filter coefficients and consequently its multipliers count. The proposed framework at the same time empowers this composite filter structure with additional capabilities of realizing all of its Ψ-symmetry based subtypes and also its special asymmetric filters case. The two-fold optimized framework thus reduces filter computational cost up to 75% as compared to the conventional approach as well as its versatility attribute not only supports diverse filter types but also offers further cost reduction via resource sharing for sequential implementation of diversified image
Effects of SiC and MgO on aluminabased ceramic foams filters
Directory of Open Access Journals (Sweden)
CAO Da-li
2007-11-01
Full Text Available Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phases after 1 hour sintering at 1 500 consist of alumina, silicon carbide, spinel and mullite.
Viewing the proton through ''color'' filters
International Nuclear Information System (INIS)
Ji, Xiangdong
2004-01-01
While the form factors and parton distributions provide separately the shape of the proton in coordinate and momentum spaces, a more powerful imaging of the proton structure can be obtained through quantum phase-space distributions. Here we introduce the Wigner-type quark and gluon distributions which depict a full-3D proton at every fixed Feynman momentum, like what is seen through momentum(''color'')-filters. After appropriate reductions, the phase-space distributions are related to the generalized parton distributions (GPDs) and transverse-momentum dependent parton distributions measurable in high-energy experiments. (orig.)
Paramedic literature search filters: optimised for clinicians and academics.
Olaussen, Alexander; Semple, William; Oteir, Alaa; Todd, Paula; Williams, Brett
2017-10-11
Search filters aid clinicians and academics to accurately locate literature. Despite this, there is no search filter or Medical Subject Headings (MeSH) term pertaining to paramedics. Therefore, the aim of this study was to create two filters to meet to different needs of paramedic clinicians and academics. We created a gold standard from a reference set, which we measured against single terms and search filters. The words and phrases used stemmed from selective exclusion of terms from the previously published Prehospital Search Filter 2.0 as well as a Delphi session with an expert panel of paramedic researchers. Independent authors deemed articles paramedic-relevant or not following an agreed definition. We measured sensitivity, specificity, accuracy and number needed to read (NNR). We located 2102 articles of which 431 (20.5%) related to paramedics. The performance of single terms was on average of high specificity (97.1% (Standard Deviation 7.4%), but of poor sensitivity (12.0%, SD 18.7%). The NNR ranged from 1 to 8.6. The sensitivity-maximising search filter yielded 98.4% sensitivity, with a specificity of 74.3% and a NNR of 2. The specificity-maximising filter achieved 88.3% in specificity, which only lowered the sensitivity to 94.7%, and thus a NNR of 1.48. We have created the first two paramedic specific search filters, one optimised for sensitivity and one optimised for specificity. The sensitivity-maximising search filter yielded 98.4% sensitivity, and a NNR of 2. The specificity-maximising filter achieved 88.3% in specificity, which only lowered the sensitivity to 94.7%, and a NNR of 1.48. A paramedic MeSH term is needed.
Sitaram, Mahesh I; Padiyar, KR; Ramanarayanan, V
1998-01-01
Active filters have long been in use for the filtering of power system load harmonics. In this paper, the digital simulation results of a hybrid active power filter system for a rectifier load are presented. The active filter is used for filtering higher order harmonics as the dominant harmonics are filtered by the passive filter. This reduces the rating of the active filter significantly. The DC capacitor voltage of the active filter is controlled using a PI controller.
Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José
2009-03-30
We propose theoretically and demonstrate experimentally an optical architecture for flexible Ultra-Wideband pulse generation. It is based on an N-tap reconfigurable microwave photonic filter fed by a laser array by using phase inversion in a Mach-Zehnder modulator. Since a large number of positive and negative coefficients can be easily implemented, UWB pulses fitted to the FCC mask requirements can be generated. As an example, a four tap pulse generator is experimentally demonstrated which complies with the FCC regulation. The proposed pulse generator allows different pulse modulation formats since the amplitude, polarity and time delay of generated pulse is controlled.
Modelling of air flows in pleated filters and of their clogging by solid particles
International Nuclear Information System (INIS)
Del Fabbro, L.
2002-01-01
The devices of air cleaning against particles are widely spread in various branches of industry: nuclear, motor, food, electronic,...; among these devices, numerous are constituted by pleated porous media to increase the surface of filtration and thus to reduce the pressure drop, for given air flow. The objective of our work is to compensate a lack evident of knowledge on the evolution of the pressure drop of pleated filter during the clogging and to deduct a modelling from it, on the basis of experiments concerning industrial filters of nuclear and car types. The obtained model is a function of characteristics of the filtering medium and pleats, of the characteristics of solid particles deposited on the filter, of the mass of particles and of the aeraulic conditions of air flow. It also depends on data on the clogging of flat filters of equivalent medium. To elaborate this model of pressure drop, an initial stage was carried out in order to characterize, experimentally and numerically, the pressure drop and the distribution of air flow in clean pleated filters of nuclear (high efficiency particulate air filter, in fiberglasses) and car (mean efficiency filter, in fibers of cellulose) types. The numerical model allowed to understand the fundamental role played by the aeraulic resistance of the filtering medium. From an non-dimensional approach, we established a semi-empirical model of pressure drop for a clean pleated filter valid for both studied types of medium; this model is used of first base for the development of the final model of clogging. The study of the clogging of the filters showed the complexity of the phenomenon dependent mainly on a reduction of the surface of filtration. This observation brings us to propose a clogging of pleated filters in three phases. Both first phases are similar in those observed for flat filters, while last phase corresponds to a reduction of the surface of filtration and leads a strong increase of the filter pressure drop
Efficient scattering angle filtering for Full waveform inversion
Alkhalifah, Tariq Ali
2015-01-01
Controlling the scattering angles between the state and the adjoint variables for the energy admitted into an inversion gradient or an image can help improve these functions for objectives in full waveform inversion (FWI) or seismic imaging. However, the access of the scattering angle information usually requires an axis extension that could be costly, especially in 3D. For the purpose of a scattering angle filter, I develop techniques that utilize the mapping nature (no domain extension) of the filter for constant-velocity background models to interpolate between such filtered gradients using the actual velocity. The concept has well known roots in the application of phase-shift-plus-interpolation utilized commonly in the downward continuation process. If the difference between the minimum and maximum velocity of the background medium is large, we obtain filtered gradients corresponding to more constant velocity backgrounds and use linear interpolation between such velocities. The accuracy of this approximation for the Marmousi model gradient demonstrates the e ectiveness of the approach.
Efficient scattering angle filtering for Full waveform inversion
Alkhalifah, Tariq Ali
2015-08-19
Controlling the scattering angles between the state and the adjoint variables for the energy admitted into an inversion gradient or an image can help improve these functions for objectives in full waveform inversion (FWI) or seismic imaging. However, the access of the scattering angle information usually requires an axis extension that could be costly, especially in 3D. For the purpose of a scattering angle filter, I develop techniques that utilize the mapping nature (no domain extension) of the filter for constant-velocity background models to interpolate between such filtered gradients using the actual velocity. The concept has well known roots in the application of phase-shift-plus-interpolation utilized commonly in the downward continuation process. If the difference between the minimum and maximum velocity of the background medium is large, we obtain filtered gradients corresponding to more constant velocity backgrounds and use linear interpolation between such velocities. The accuracy of this approximation for the Marmousi model gradient demonstrates the e ectiveness of the approach.
New series active power filter for computers loads and small non-linear loads
Energy Technology Data Exchange (ETDEWEB)
Tarnini, M.Y. [Hariri Canadian Univ., Meshref (Lebanon)
2009-07-01
This paper proposed the use of a single-phase series active power filter to reduce voltage total harmonic distortion and provide improved power quality. Control schemes were developed using simple control algorithms and a reduced number of current transducers. The circuit was comprised of a power supply and zero crossing detector; a hall-effect current sensor and signal conditioning circuit; a microcontroller circuit; a driving circuit; and an inverter bridge. The filter corrected fundamental and sinusoidal voltage amplitudes. The amplitude of the fundamental current in the series filter was controlled using a microcontroller placed between the load voltage and a pre-established reference point. Experiments were conducted to test the source voltage and source current after compensation using a prototype of the filter. The control system provided effective correction of the power factor and harmonic distortion, and reached steady state in approximately 2 cycles. It was concluded that the compensator can also be adapted for use in 3-phase systems. 13 refs., 1 tab., 14 figs.
Ultrathin diamond-like carbon films deposited by filtered carbon vacuum arcs
International Nuclear Information System (INIS)
Anders, Andre; Fong, Walton; Kulkarni, Ashok; Ryan, Francis W.; Bhatia, C. Singh
2001-01-01
Ultrathin ( and lt; 5 nm) hard carbon films are of great interest to the magnetic storage industry as the areal density approaches 100 Gbit/in(sup 2). These films are used as overcoats to protect the magnetic layers on disk media and the active elements of the read-write slider. Tetrahedral amorphous carbon films can be produced by filtered cathodic arc deposition, but the films will only be accepted by the storage industry only if the ''macroparticle'' issue has been solved. Better plasma filters have been developed over recent years. Emphasis is put on the promising twist filter system - a compact, open structure that operates with pulsed arcs and high magnetic field. Based on corrosion tests it is shown that the macroparticle reduction by the twist filter is satisfactory for this demanding application, while plasma throughput is very high. Ultrathin hard carbon films have been synthesized using S-filter and twist filter systems. Film properties such as hardness, elastic modulus, wear, and corrosion resistance have been tested
Walsh-synthesized noise filters for quantum logic
International Nuclear Information System (INIS)
Ball, Harrison; Biercuk, Michael J.
2015-01-01
We study a novel class of open-loop control protocols constructed to perform arbitrary nontrivial single-qubit logic operations robust against time-dependent non-Markovian noise. Amplitude and phase modulation protocols are crafted leveraging insights from functional synthesis and the basis set of Walsh functions. We employ the experimentally validated generalized filter-transfer function formalism in order to find optimized control protocols for target operations in SU(2) by defining a cost function for the filter-transfer function to be minimized through the applied modulation. Our work details the various techniques by which we define and then optimize the filter-synthesis process in the Walsh basis, including the definition of specific analytic design rules which serve to efficiently constrain the available synthesis space. This approach yields modulated-gate constructions consisting of chains of discrete pulse-segments of arbitrary form, whose modulation envelopes possess intrinsic compatibility with digital logic and clocking. We derive novel families of Walsh-modulated noise filters designed to suppress dephasing and coherent amplitude-damping noise, and describe how well-known sequences derived in NMR also fall within the Walsh-synthesis framework. Finally, our work considers the effects of realistic experimental constraints such as limited modulation bandwidth on achievable filter performance. (orig.)
Walsh-synthesized noise filters for quantum logic
Energy Technology Data Exchange (ETDEWEB)
Ball, Harrison; Biercuk, Michael J. [The University of Sydney, ARC Centre for Engineered Quantum Systems, School of Physics, Sydney, NSW (Australia); National Measurement Institute, Sydney, NSW (Australia)
2015-05-14
We study a novel class of open-loop control protocols constructed to perform arbitrary nontrivial single-qubit logic operations robust against time-dependent non-Markovian noise. Amplitude and phase modulation protocols are crafted leveraging insights from functional synthesis and the basis set of Walsh functions. We employ the experimentally validated generalized filter-transfer function formalism in order to find optimized control protocols for target operations in SU(2) by defining a cost function for the filter-transfer function to be minimized through the applied modulation. Our work details the various techniques by which we define and then optimize the filter-synthesis process in the Walsh basis, including the definition of specific analytic design rules which serve to efficiently constrain the available synthesis space. This approach yields modulated-gate constructions consisting of chains of discrete pulse-segments of arbitrary form, whose modulation envelopes possess intrinsic compatibility with digital logic and clocking. We derive novel families of Walsh-modulated noise filters designed to suppress dephasing and coherent amplitude-damping noise, and describe how well-known sequences derived in NMR also fall within the Walsh-synthesis framework. Finally, our work considers the effects of realistic experimental constraints such as limited modulation bandwidth on achievable filter performance. (orig.)
Chen, Liang-Chia; Ho, Hsuan-Wei; Nguyen, Xuan-Loc
2010-02-01
This article presents a novel band-pass filter for Fourier transform profilometry (FTP) for accurate 3-D surface reconstruction. FTP can be employed to obtain 3-D surface profiles by one-shot images to achieve high-speed measurement. However, its measurement accuracy has been significantly influenced by the spectrum filtering process required to extract the phase information representing various surface heights. Using the commonly applied 2-D Hanning filter, the measurement errors could be up to 5-10% of the overall measuring height and it is unacceptable to various industrial application. To resolve this issue, the article proposes an elliptical band-pass filter for extracting the spectral region possessing essential phase information for reconstructing accurate 3-D surface profiles. The elliptical band-pass filter was developed and optimized to reconstruct 3-D surface models with improved measurement accuracy. Some experimental results verify that the accuracy can be effectively enhanced by using the elliptical filter. The accuracy improvement of 44.1% and 30.4% can be achieved in 3-D and sphericity measurement, respectively, when the elliptical filter replaces the traditional filter as the band-pass filtering method. Employing the developed method, the maximum measured error can be kept within 3.3% of the overall measuring range.
Reduksi Harmonisa Pada Uninterruptible Power Supply (UPS) Dengan Single Tuned Passive Filter
Nasution, Agus Almi
2017-01-01
Using non-linier load in Uninterruptible Power Supply (UPS) can cause harmonic distortion which will eventually have the effect on power quality. The research was designed as a single-turned passive filter to cope will harmonic distortion in UPS. In this phase, THDv, THDi, and IHDi were measured in UPS. MATLAB/Simulink was used for simulation of filter testing. After single-turned passive filter was installed, the third order of harmonic current decreased from 47,69% to 7,08% or reduced 40.61...
DEFF Research Database (Denmark)
Golestan, Saeed; Monfared, Mohammad; Frejeido, Francisco
2014-01-01
Control Parameters design of a three-phase synchronous reference frame phase locked loop (SRF-PLL) with a pre-filtering stage (acting as the sequence separator) is not a trivial task. The conventional way to deal with this problem is to neglect the interaction between the SRF-PLL and pre-filterin......Control Parameters design of a three-phase synchronous reference frame phase locked loop (SRF-PLL) with a pre-filtering stage (acting as the sequence separator) is not a trivial task. The conventional way to deal with this problem is to neglect the interaction between the SRF-PLL and pre......-integral-derivative controller as the loop filter (instead of the commonly adopted proportionalintegral controller) and arranging a pole-zero cancellation. The suggested method is simple and efficient, and is applicable to the joint operation of different sequence separation techniques and the SRF-PLL. The effectiveness...
Characterization of magnesium phosphate ceramics incorporating off-gas filters
International Nuclear Information System (INIS)
Yang, Jae Hwan; Lee, Chang Hwa; Heo, Chul Min; Jeon, Min Ku; Kang, Kweon Ho
2011-01-01
Radioactive cesium (Cs-137) and technetium (Tc-99) are discharged from the spent fuel as gaseous forms during the head-end process in pyroprocess. These off-gases are safely trapped via porous ceramic filters made of fly ash and calcium based material. Spent filters have to be treated, converted into proper waste forms in order to be disposed safely at a repository. Conventional technology used to make waste forms such as vitrification requires high temperature and complex process. In this study, we report a promising method to stabilize spent filters containing cesium and technetium using magnesium phosphate ceramics. Simulated spent filters were fabricated by vaporizing nonradioactive cesium and rhenium (a surrogate of Tc) through the voloxidizer. The crushed filters were mixed with raw materials of magnesium phosphate ceramics, to be stabilized in the phosphate ceramic matrix. Characterization of the waste forms was made by the compressive strength test, apparent porosity, XRD analysis, and SEM analysis. The sample containing filters showed the excellent mechanical property, with the highest compressive strength of 38.1 MPa in the sample with 30 wt% of Cs-filter. Microstructural analysis suggests that wastes are embedded in the crystalline phase formed by an acid-base reaction. (author)
International Nuclear Information System (INIS)
Hwang, Yong Hwa; Lee, Hyung Kwon; Chun, Young Bum; Park, Dae Gyu; Ahn, Sang Bok; Chu, Yong Sun; Kim, Eun Ka.
1997-12-01
The development of high efficiency filter was started to protect human beings from the contamination of radioactive particles, toxic gases and bacillus, and its gradual performance increment led to the fabrication of Ultra Low Penetration Air Filter (ULPA) today. The application field of ULPA has been spread not only to the air conditioning of nuclear power facilities, semiconductor industries, life science, optics, medical care and general facilities but also to the core of ultra-precision facilities. Periodic performance test on the filters is essential to extend its life-time through effective maintenance. Especially, the bank test on HEPA filter of nuclear facilities handling radioactive materials is required for environmental safety. Nowadays, the bank test technology has been reached to the utilization of a minimized portable detecting instruments and the evaluation techniques can provide high confidence in the area of particle distribution and leakage test efficiency. (author). 16 refs., 13 tabs., 14 figs
A Temperature-to-Digital Converter Based on an Optimized Electrothermal Filter
Kashmiri, S.M.; Xia, S.; Makinwa, K.A.A.
2009-01-01
This paper describes the design of a CMOS temperature-to-digital converter (TDC). It operates by measuring the temperature-dependent phase shift of an electrothermal filter (ETF). Compared to previous work, this TDC employs an ETF whose layout has been optimized to minimize the thermal phase spread
Wiener's Loop Filter for PLL-Based Carrier Recovery of OQPSK and MSK-Type Modulations
Directory of Open Access Journals (Sweden)
Arnaldo Spalvieri
2008-01-01
Full Text Available This letter considers carrier recovery for offset quadrature phase shift keying (OQPSK and minimum shift keying-type (MSK-type modulations based on phase-lock loop (PLL. The concern of the letter is the optimization of the loop filter of the PLL. The optimization is worked out in the light of Wiener's theory taking into account the phase noise affecting the incoming carrier, the additive white Gaussian noise that is present on the channel, and the self-noise produced by the phase detector. Delay in the loop, which may affect the numerical implementation of the PLL, is also considered. Closed-form expressions for the loop filter and for the mean-square error are given for the case where the phase noise is characterized as a first-order process.
Phase-step retrieval for tunable phase-shifting algorithms
Ayubi, Gastón A.; Duarte, Ignacio; Perciante, César D.; Flores, Jorge L.; Ferrari, José A.
2017-12-01
Phase-shifting (PS) is a well-known technique for phase retrieval in interferometry, with applications in deflectometry and 3D-profiling, which requires a series of intensity measurements with certain phase-steps. Usually the phase-steps are evenly spaced, and its knowledge is crucial for the phase retrieval. In this work we present a method to extract the phase-step between consecutive interferograms. We test the proposed technique with images corrupted by additive noise. The results were compared with other known methods. We also present experimental results showing the performance of the method when spatial filters are applied to the interferograms and the effect that they have on their relative phase-steps.
Filter assembly for metallic and intermetallic tube filters
Alvin, Mary Anne; Lippert, Thomas E.; Bruck, Gerald J.; Smeltzer, Eugene E.
2001-01-01
A filter assembly (60) for holding a filter element (28) within a hot gas cleanup system pressure vessel is provided, containing: a filter housing (62), said filter housing having a certain axial length and having a peripheral sidewall, said sidewall defining an interior chamber (66); a one piece, all metal, fail-safe/regenerator device (68) within the interior chamber (66) of the filter housing (62) and/or extending beyond the axial length of the filter housing, said device containing an outward extending radial flange (71) within the filter housing for seating an essential seal (70), the device also having heat transfer media (72) disposed inside and screens (80) for particulate removal; one compliant gasket (70) positioned next to and above the outward extending radial flange of the fail-safe/regenerator device; and a porous metallic corrosion resistant superalloy type filter element body welded at the bottom of the metal fail-safe/regenerator device.
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels E.
2012-01-01
We implement phase-only shaped laser pulses within quantum optimal control theory for laser-molecule interaction. This approach is applied to the indirect photofragmentation dynamics of NaI in the weak-field limit. It is shown that optimized phase-modulated pulses with a fixed frequency distribut...... distribution can substantially modify transient dissociation probabilities as well as the momentum distribution associated with the relative motion of Na and I. © 2012 American Institute of Physics....
Statistically-Efficient Filtering in Impulsive Environments: Weighted Myriad Filters
Directory of Open Access Journals (Sweden)
Juan G. Gonzalez
2002-01-01
Full Text Available Linear filtering theory has been largely motivated by the characteristics of Gaussian signals. In the same manner, the proposed Myriad Filtering methods are motivated by the need for a flexible filter class with high statistical efficiency in non-Gaussian impulsive environments that can appear in practice. Myriad filters have a solid theoretical basis, are inherently more powerful than median filters, and are very general, subsuming traditional linear FIR filters. The foundation of the proposed filtering algorithms lies in the definition of the myriad as a tunable estimator of location derived from the theory of robust statistics. We prove several fundamental properties of this estimator and show its optimality in practical impulsive models such as the ÃŽÂ±-stable and generalized-t. We then extend the myriad estimation framework to allow the use of weights. In the same way as linear FIR filters become a powerful generalization of the mean filter, filters based on running myriads reach all of their potential when a weighting scheme is utilized. We derive the Ã¢Â€ÂœnormalÃ¢Â€Â equations for the optimal myriad filter, and introduce a suboptimal methodology for filter tuning and design. The strong potential of myriad filtering and estimation in impulsive environments is illustrated with several examples.
Filter material charging apparatus for filter assembly for radioactive contaminants
International Nuclear Information System (INIS)
Goldsmith, J.M.; O'Nan, A. Jr.
1977-01-01
A filter charging apparatus for a filter assembly is described. The filter assembly includes a housing with at least one filter bed therein and the filter charging apparatus for adding filter material to the filter assembly includes a tank with an opening therein, the tank opening being disposed in flow communication with opposed first and second conduit means, the first conduit means being in flow communication with the filter assembly housing and the second conduit means being in flow communication with a blower means. Upon activation of the blower means, the blower means pneumatically conveys the filter material from the tank to the filter housing
Influence of modulation method on using LC-traps with single-phase voltage source converters
DEFF Research Database (Denmark)
Wang, Xiongfei; Min, Huang; Bai, Haofeng
2015-01-01
The switching-frequency LC-trap filter has recently been employed with high-order passive filters for Voltage Source Inverters (VSIs). This paper investigates the influence of modulation method on using the LC-traps with single-phase VSIs. Two-level (bipolar) and three-level (unipolar) modulations...... that include phase distortion and alternative phase opposition distortion methods are analyzed. Harmonic filtering performances of four LC-trap-based filters with different locations of LC-traps are compared. It is shown that the use of parallel-LC-traps in series with filter inductors, either grid...... or converter side, has a worse harmonic filtering performance than using series-LC-trap in the shunt branch. Simulations and experimental results are presented for verifications....
Artifact Reduction of Susceptibility-Weighted Imaging Using a Short-Echo Phase Mask
International Nuclear Information System (INIS)
Ishimori, Y.; Monma, M.; Kohno, Y.
2009-01-01
Background: Susceptibility-weighted imaging (SWI) is utilized in magnetic resonance (MR) venography and other applications, but can include artifacts caused by the phase-masking process. Purpose: To demonstrate risks of filter processes used in making phase masks for SWI, and to propose a simple method for reducing artifacts. Material and Methods: Phase linearity related to echo time (TE) was evaluated for the original phase and high-pass-filtered phase using a CuSO 4 -doped water phantom. Effect of filter size of the Hanning window and background homogeneity were also evaluated in a phantom study. Use of a phase mask generated by data with differing magnitudes of TE was attempted in a human study. Shorter TE was used for making the phase mask, and the number of multiplications was increased. As short and long TEs were necessary simultaneously for phase mask and T2* contrast, a dual-echo technique was used. Results: Linearity of TE and phase value collapsed, and an unexpected negative phase appeared in the high-pass-filtered phase. Using a short-TE phase mask, phase-aliasing artifacts were reduced and visibility of deep veins was equivalent to that under conventional methods with an increased number of multiplications. Conclusion: Use of a short-echo phase mask in SWI is useful for reducing artifacts
Soft sensing for two-phase flow using an ensemble Kalman filter
Gryzlov, A.; Leskens, M.; Mudde, R.F.
2009-01-01
A new approach for real-time monitoring of horizontal wells, which is based on data assimilation concepts, is presented. Such methodology can be used when the direct measurement of multiphase flow rates is unfeasible or even unavailable. The real-time estimator proposed is an ensemble Kalman filter
International Nuclear Information System (INIS)
Qi Zhihua; Chen Guanghong
2007-01-01
Recently, x-ray differential phase contrast computed tomography (DPC-CT) has been experimentally implemented using a conventional source combined with several gratings. Images were reconstructed using a parallel-beam reconstruction formula. However, parallel-beam reconstruction formulae are not directly applicable for a large image object where the parallel-beam approximation fails. In this note, we present a new image reconstruction formula for fan-beam DPC-CT. There are two major features in this algorithm: (1) it enables the reconstruction of a local region of interest (ROI) using data acquired from an angular interval shorter than 180 0 + fan angle and (2) it still preserves the filtered backprojection structure. Numerical simulations have been conducted to validate the image reconstruction algorithm. (note)
Bayesian Parameter Estimation via Filtering and Functional Approximations
Matthies, Hermann G.
2016-11-25
The inverse problem of determining parameters in a model by comparing some output of the model with observations is addressed. This is a description for what hat to be done to use the Gauss-Markov-Kalman filter for the Bayesian estimation and updating of parameters in a computational model. This is a filter acting on random variables, and while its Monte Carlo variant --- the Ensemble Kalman Filter (EnKF) --- is fairly straightforward, we subsequently only sketch its implementation with the help of functional representations.
Bayesian Parameter Estimation via Filtering and Functional Approximations
Matthies, Hermann G.; Litvinenko, Alexander; Rosic, Bojana V.; Zander, Elmar
2016-01-01
The inverse problem of determining parameters in a model by comparing some output of the model with observations is addressed. This is a description for what hat to be done to use the Gauss-Markov-Kalman filter for the Bayesian estimation and updating of parameters in a computational model. This is a filter acting on random variables, and while its Monte Carlo variant --- the Ensemble Kalman Filter (EnKF) --- is fairly straightforward, we subsequently only sketch its implementation with the help of functional representations.
High-Q Bandpass Comb Filter for Mains Interference Extraction
Directory of Open Access Journals (Sweden)
Neycheva T.
2009-12-01
Full Text Available This paper presents a simple digital high-Q bandpass comb filter for power-line (PL or other periodical interference extraction. The filter concept relies on a correlated signal average resulting in alternating constructive and destructive spectrum interference i.e. the so-called comb frequency response. The presented filter is evaluated by Matlab simulations with real ECG signal contaminated with low amplitude PL interference. The made simulations show that this filter accurately extract the PL interference. It has high-Q notches only at PL odd harmonics and is appropriate for extraction of any kind of odd harmonic interference including rectangular shape. The filter is suitable for real-time operation with popular low-cost microcontrollers.
Design and Realization of FIR Filter for Inter Satellite Link at 50-90 MHZ Frequency using FPGA
Directory of Open Access Journals (Sweden)
Yuyu Wahyu
2016-12-01
Full Text Available In this paper, design and realization of FIR filter with a bandwidth of 40 MHz at 50-90 MHz frequency has been proposed. The design was destined to be implemented on the Inter Satellite Links (ISL. This kind of filter had been selected due to a need in linear phase responseon the ISL data communication. Equiripple method was used to design the filter becauseof its reliability in minimizing the magnitude errors. The design of this FIR filter was conducted with theoretical calculation and simulation using the R2012b Matlab. For the implementation, FPGA was used with a VHDL as the programming language with a help of Xilinx ISE Design Suite 14.5. Simulation results in Matlab and Simulink indicated that the filter design could be well implemented on ISL at frequency of 50 MHz - 90 MHz with stopband of 60 db. The phase responseresult of the realized design is quite linear so that the filter is suitable for data communication on the ISL.
Optimal filter bandwidth for pulse oximetry
Stuban, Norbert; Niwayama, Masatsugu
2012-10-01
Pulse oximeters contain one or more signal filtering stages between the photodiode and microcontroller. These filters are responsible for removing the noise while retaining the useful frequency components of the signal, thus improving the signal-to-noise ratio. The corner frequencies of these filters affect not only the noise level, but also the shape of the pulse signal. Narrow filter bandwidth effectively suppresses the noise; however, at the same time, it distorts the useful signal components by decreasing the harmonic content. In this paper, we investigated the influence of the filter bandwidth on the accuracy of pulse oximeters. We used a pulse oximeter tester device to produce stable, repetitive pulse waves with digitally adjustable R ratio and heart rate. We built a pulse oximeter and attached it to the tester device. The pulse oximeter digitized the current of its photodiode directly, without any analog signal conditioning. We varied the corner frequency of the low-pass filter in the pulse oximeter in the range of 0.66-15 Hz by software. For the tester device, the R ratio was set to R = 1.00, and the R ratio deviation measured by the pulse oximeter was monitored as a function of the corner frequency of the low-pass filter. The results revealed that lowering the corner frequency of the low-pass filter did not decrease the accuracy of the oxygen level measurements. The lowest possible value of the corner frequency of the low-pass filter is the fundamental frequency of the pulse signal. We concluded that the harmonics of the pulse signal do not contribute to the accuracy of pulse oximetry. The results achieved by the pulse oximeter tester were verified by human experiments, performed on five healthy subjects. The results of the human measurements confirmed that filtering out the harmonics of the pulse signal does not degrade the accuracy of pulse oximetry.
Development and evaluation of a cleanable high efficiency steel filter
International Nuclear Information System (INIS)
Bergman, W.; Larsen, G.; Weber, F.; Wilson, P.; Lopez, R.; Valha, G.; Conner, J.; Garr, J.; Williams, K.; Biermann, A.; Wilson, K.; Moore, P.; Gellner, C.; Rapchun, D.; Simon, K.; Turley, J.; Frye, L.; Monroe, D.
1993-01-01
We have developed a high efficiency steel filter that can be cleaned in-situ by reverse air pulses. The filter consists of 64 pleated cylindrical filter elements packaged into a 6l0 x 6l0 x 292 mm aluminum frame and has 13.5 m 2 of filter area. The filter media consists of a sintered steel fiber mat using 2 μm diameter fibers. We conducted an optimization study for filter efficiency and pressure drop to determine the filter design parameters of pleat width, pleat depth, outside diameter of the cylinder, and the total number of cylinders. Several prototype cylinders were then built and evaluated in terms of filter cleaning by reverse air pulses. The results of these studies were used to build the high efficiency steel filter. We evaluated the prototype filter for efficiency and cleanability. The DOP filter certification test showed the filter has a passing efficiency of 99.99% but a failing pressure drop of 0.80 kPa at 1,700 m 3 /hr. Since we were not able to achieve a pressure drop less than 0.25 kPa, the steel filter does not meet all the criteria for a HEPA filter. Filter loading and cleaning tests using AC Fine dust showed the filter could be repeatedly cleaned by reverse air pulses. The next phase of the prototype evaluation consisted of installing the unit and support housing in the exhaust duct work of a uranium grit blaster for a field evaluation at the Y-12 Plant in Oak Ridge, TN. The grit blaster is used to clean the surface of uranium parts and generates a cloud of UO 2 aerosols. We used a 1,700 m 3 /hr slip stream from the 10,200 m 3 /hr exhaust system
Suggestions for removing operational faults in air filter plants
Energy Technology Data Exchange (ETDEWEB)
Ochs, H J
1980-11-01
Air filters are expected to achieve certain performances within their duty, viz. to precipitate air-alien matter in the air stream, the results of which will have to be checked. As a number of external influences affect the function of the air filter and, therefore, may alter the pre-defined data, checking should not only cover the air filter but also the other parts of the ventilating plant, to assure a faultless continuous operation.
Directory of Open Access Journals (Sweden)
Yan Liu
2014-01-01
Full Text Available Synthesis of phase-only reconfigurable array aims at finding a common amplitude distribution and different phase distributions for the array to form different patterns. In this paper, the synthesis problem is formulated as a multiobjective optimization problem and solved by a new proposed algorithm MOEA/D-IWO. First, novel strategies are introduced in invasive weed optimization (IWO to make original IWO fit for solving multiobjective optimization problems; then, the modified IWO is integrated into the framework of the recently well proved competitive multiobjective optimization algorithm MOEA/D to form a new competitive MOEA/D-IWO algorithm. At last, two sets of experiments are carried out to illustrate the effectiveness of MOEA/D-IWO. In addition, MOEA/D-IWO is compared with MOEA/D-DE, a new version of MOEA/D. The comparing results show the superiority of MOEA/D-IWO and indicate its potential for solving the antenna array synthesis problems.
Assessment of a membrane drinking water filter in an emergency setting.
Ensink, Jeroen H J; Bastable, Andy; Cairncross, Sandy
2015-06-01
The performance and acceptability of the Nerox(TM) membrane drinking water filter were evaluated among an internally displaced population in Pakistan. The membrane filter and a control ceramic candle filter were distributed to over 3,000 households. Following a 6-month period, 230 households were visited and filter performance and use were assessed. Only 6% of the visited households still had a functioning filter, and the removal performance ranged from 80 to 93%. High turbidity in source water (irrigation canals), together with high temperatures and large family size were likely to have contributed to poor performance and uptake of the filters.
Phase contrast image synthesis
DEFF Research Database (Denmark)
Glückstad, J.
1996-01-01
A new method is presented for synthesizing arbitrary intensity patterns based on phase contrast imaging. The concept is grounded on an extension of the Zernike phase contrast method into the domain of full range [0; 2 pi] phase modulation. By controlling the average value of the input phase funct...... function and by choosing appropriate phase retardation at the phase contrast filter, a pure phase to intensity imaging is accomplished. The method presented is also directly applicable in dark field image synthesis....
Mei, Meng; Huang, Xiaojia
2017-11-24
Due to the endocrine disrupting properties, organic UV filters have been a great risk for humans and other organisms. Therefore, development of accurate and effective analytical methods is needed for the determination of UV filters in environmental waters. In this work, a fast, sensitive and environmentally friendly method combining magnetism-enhanced monolith-based in-tube solid phase microextraction with high-performance liquid chromatography with diode array detection (DAD) (ME-MB-IT/SPME-HPLC-DAD) for the online analysis of five organic UV filters in environmental water samples was developed. To extract UV filters effectively, an ionic liquid-based monolithic capillary column doped with magnetic nanoparticles was prepared by in-situ polymerization and used as extraction medium of online ME-MB-IT/SPME-HPLC-DAD system. Several extraction conditions including the intensity of magnetic field, sampling and desorption flow rate, volume of sample and desorption solvent, pH value and ionic strength of sample matrix were optimized thoroughly. Under the optimized conditions, the extraction efficiencies for five organic UV filters were in the range of 44.0-100%. The limits of detection (S/N=3) and limits of quantification (S/N=10) were 0.04-0.26μg/L and 0.12-0.87μg/L, respectively. The precisions indicated by relative standard deviations (RSDs) were less than 10% for both intra- and inter-day variabilities. Finally, the developed method was successfully applied to the determination of UV filters in three environmental water samples and satisfactory results were obtained. Copyright © 2017 Elsevier B.V. All rights reserved.
Numerical Analysis of a Passive Containment Filtered Venting System
International Nuclear Information System (INIS)
Kim, Taejoon; Ha, Huiun; Heo, Sun
2014-01-01
The passive Containment Filtered Venting system (CFVS) does not have principally any kind of isolation valves or filtering devices which need periodic maintenance. In this study, the hydro-thermal analysis is presented to investigate the existence of flow instability in the passive CFVS and its performance under the pressure change of APR+ containment building with LB-LOCA M/E data. The Passive Containment Filtered Venting System was suggested as a part in i-Power development project and the operation mechanism was investigated by numerical modeling and simulation using GOTHIC8.0 system code. There are four Phases for consideration to investigate the pressurization of the containment building, loss of hydrostatic head in the pipe line of CFVS, opening of pipe line and gas ejection to the coolant tank, and the head recovery inside the pipe as the containment gas exhausted. The simulation results show that gas generation rate determine the timing of head recovery in the CFVS pipe line and that the equipment of various devices inducing pressure loss at the pipe can give the capacity of Phase control of the passive CFVS operation
A Re-examination of the Effect of Masker Phase Curvature on Non-simultaneous Masking.
Carlyon, Robert P; Flanagan, Sheila; Deeks, John M
2017-12-01
Forward masking of a sinusoidal signal is determined not only by the masker's power spectrum but also by its phase spectrum. Specifically, when the phase spectrum is such that the output of an auditory filter centred on the signal has a highly modulated ("peaked") envelope, there is less masking than when that envelope is flat. This finding has been attributed to non-linearities, such as compression, reducing the average neural response to maskers that produce more peaked auditory filter outputs (Carlyon and Datta, J Acoust Soc Am 101:3636-3647, 1997). Here we evaluate an alternative explanation proposed by Wotcjzak and Oxenham (Wojtczak and Oxenham, J Assoc Res Otolaryngol 10:595-607, 2009). They reported a masker phase effect for 6-kHz signals when the masker components were at least an octave below the signal frequency. Wotcjzak and Oxenham argued that this effect was inconsistent with cochlear compression, and, because it did not occur at lower signal frequencies, was also inconsistent with more central compression. It was instead attributed to activation of the efferent system reducing the response to the subsequent probe. Here, experiment 1 replicated their main findings. Experiment 2 showed that the phase effect on off-frequency forward masking is similar at signal frequencies of 2 and 6 kHz, provided that one equates the number of components likely to interact within an auditory filter centred on the signal, thereby roughly equating the effect of masker phase on the peakiness of that filter output. Experiment 3 showed that for some subjects, masker phase also had a strong influence on off-frequency backward masking of the signal, and that the size of this effect correlated across subjects with that observed in forward masking. We conclude that the masker phase effect is mediated mainly by cochlear non-linearities, with a possible additional effect of more central compression. The data are not consistent with a role for the efferent system.
Energy Technology Data Exchange (ETDEWEB)
Mino Aguilar, Gerardo
1999-05-01
In here it is presented a brief review of the state of art of power active filters used in the common coupling points between AC sources and nonlinear loads formed by static converters of AC/DC, for the suppression of harmonic currents and instantaneous compensation of the reactive power. Starting off from the active filters that affect only the three balanced currents of the three-phase systems of 3 wires, it is arrived at the subject of this thesis, whose objective is to solve the problem of the reactive compensation and suppression of harmonic currents in the three phases as well as in the neuter of the three-phase systems of 4 wires. The main contribution of this thesis is the design, analysis and simulation of an active filter that besides of suppressing the harmonic currents and compensating the power factor in the three phases of an unbalanced three-phase system, also has the capacity of removing the current that circulates in the neuter due to the unbalance of the phase currents. This design is based on the extension of the theory of the instantaneous reactive power that includes the existence of the zero sequence components of in the phase currents. It is set out in the thesis a novel filter based on an three-phase inverter of 4 branches, 3 branches of phase and one branch of neuter, that to the best knowledge of the author it has not been reported in the literature. Use is made of an extensive number of simulation results to prove the validity of this filter, whose behavior is superior to the filters for suppression of currents in the neuter existing in the literature, of which also a comparative study is presented. The thesis also includes a mathematical and graphical analysis of the symmetrical components in balanced and unbalanced systems in order to know the nature of the harmonic currents of zero sequence. It is included a section on causes and effects of the harmonic contamination problem. [Spanish] Se presenta un breve revision del estado del
DEFF Research Database (Denmark)
Han, Yang; Shen, Pan; Guerrero, Josep M.
2016-01-01
Grid-connected inverters (GCIs) with LCL output filter have the ability of attenuating high-frequency (HF) switching ripples. However, by using only grid-current control, the system is prone to resonances if it is not properly damped, and the current distortion would be amplified significantly...... method is adopted. Furthermore, the grid voltage feed-forward and multiple PR controllers are integrated in the current loop to mitigate the current distortion introduced by the grid background distortion. Besides, the parameters design guidelines are presented to show the feasibility and effectiveness...
Experimental investigation of in situ cleanable HEPA filter
International Nuclear Information System (INIS)
Adamson, D.J.
1999-01-01
The Westinghouse Savannah River Company located at the Savannah River Site (SRS) in Aiken, South Carolina is currently testing the feasibility of developing an in situ cleanable high efficiency particulate air (HEPA) filter system. Sintered metal filters are being tested for regenerability or cleanability in simulated conditions found in a high level waste (HLW) tank ventilation system. The filters are being challenged using materials found in HLW tanks. HLW simulated salt, HLW simulated sludge and South Carolina road dust. Various cleaning solutions have been used to clean the filters in situ. The tanks are equipped with a ventilation system to maintain the tank contents at negative pressure to prevent the release of radioactive material to the environment. This system is equipped with conventional disposable glass-fiber HEPA filter cartridges. Removal and disposal of these filters is not only costly, but subjects site personnel to radiation exposure and possible contamination. A test apparatus was designed to simulate the ventilation system of a HLW tank with an in situ cleaning system. Test results indicate that the Mott sintered metal HEPA filter is suitable as an in situ cleanable or regenerable HEPA filter. Data indicates that high humidity or water did not effect the filter performance and the sintered metal HEPA filter was easily cleaned numerous times back to new filter performance by an in situ spray system. The test apparatus allows the cleaning of the soiled HEPA filters to be accomplished without removing the filters from process. This innovative system would eliminate personnel radiation exposure associated with removal of contaminated filters and the high costs of filter replacement and disposal. The results of these investigations indicate that an in situ cleanable HEPA filter system for radioactive and commercial use could be developed and manufactured
Application of Machine Learning Techniques for Amplitude and Phase Noise Characterization
DEFF Research Database (Denmark)
Zibar, Darko; de Carvalho, Luis Henrique Hecker; Piels, Molly
2015-01-01
In this paper, tools from machine learning community, such as Bayesian filtering and expectation maximization parameter estimation, are presented and employed for laser amplitude and phase noise characterization. We show that phase noise estimation based on Bayesian filtering outperforms...
Star-sensor-based predictive Kalman filter for satelliteattitude estimation
Institute of Scientific and Technical Information of China (English)
林玉荣; 邓正隆
2002-01-01
A real-time attitude estimation algorithm, namely the predictive Kalman filter, is presented. This algorithm can accurately estimate the three-axis attitude of a satellite using only star sensor measurements. The implementation of the filter includes two steps: first, predicting the torque modeling error, and then estimating the attitude. Simulation results indicate that the predictive Kalman filter provides robust performance in the presence of both significant errors in the assumed model and in the initial conditions.
International Nuclear Information System (INIS)
Guan, J.J.; Wang, H.Q.; Qin, L.Z.; Liao, B.; Liang, H.; Li, B.
2017-01-01
The CrCN coatings were fabricated onto Si (1 1 1) wafers and SUS304 stainless steel plates using filtered cathodic vacuum arc deposition (FCVAD) technique under different flow ratios of N_2/C_2H_2 gas mixture. The morphology, crystalline structure and chemical composition of the coatings were characterized. It was found that the grain size reduce with increasing carbon content, which makes the CrCN coatings refined and smooth. The quasi-one-dimensional carbolite phase was also found in CrN host lattice with C_2H_2 content ranging from 5% to 20%, and it will be evolved into amorphous carbon and amorphous CN_x phases as C_2H_2 content exceeds 20%. Moreover, we examined the mechanical and tribological properties of the CrCN coatings, and the experimental results confirmed that the friction coefficient of the coatings descend to the lowest value as 0.39 with 30% C_2H_2 content, due to the graphite (sp"2 C−C) phase embed in CrN host lattice; while the chromium carbon (Cr_3C_2) and diamond (sp"3 C−C) phases may give rise to the increase of the coating hardness with the highest value at 23.97 GPa under 20% C_2H_2 content.
Guan, J. J.; Wang, H. Q.; Qin, L. Z.; Liao, B.; Liang, H.; Li, B.
2017-04-01
The CrCN coatings were fabricated onto Si (1 1 1) wafers and SUS304 stainless steel plates using filtered cathodic vacuum arc deposition (FCVAD) technique under different flow ratios of N2/C2H2 gas mixture. The morphology, crystalline structure and chemical composition of the coatings were characterized. It was found that the grain size reduce with increasing carbon content, which makes the CrCN coatings refined and smooth. The quasi-one-dimensional carbolite phase was also found in CrN host lattice with C2H2 content ranging from 5% to 20%, and it will be evolved into amorphous carbon and amorphous CNx phases as C2H2 content exceeds 20%. Moreover, we examined the mechanical and tribological properties of the CrCN coatings, and the experimental results confirmed that the friction coefficient of the coatings descend to the lowest value as 0.39 with 30% C2H2 content, due to the graphite (sp2 Csbnd C) phase embed in CrN host lattice; while the chromium carbon (Cr3C2) and diamond (sp3 Csbnd C) phases may give rise to the increase of the coating hardness with the highest value at 23.97 GPa under 20% C2H2 content.
Depletion of liver glutathione levels in rats: a potential confound of nose-only inhalation.
Fechter, Laurence D; Nelson-Miller, Alisa; Gearhart, Caroline
2008-07-01
Nose-only inhalation exposure chambers offer key advantages to whole-body systems, particularly when aerosol or mixed aerosol-vapor exposures are used. Specifically, nose-only chambers provide enhanced control over the route of exposure and dose by minimizing the deposition of particles either on the subjects skin/fur or on surfaces of a whole-body exposure system. In the current series of experiments, liver, brain, and lung total glutathione (GSH) levels were assessed following either nose-only or whole-body exposures to either jet fuel or to clean, filtered air. The data were compared to untreated control subjects. Acute nose-only inhalation exposures of rats resulted in a significant depletion of liver GSH levels both in subjects that were exposed to clean, filtered air as well as those exposed to JP-8 jet fuel and to a synthetic jet fuel. Glutathione levels were not altered in lung or brain tissue. Whole-body inhalation exposure had no effect on GSH levels in any tissue for any of the treatment groups. A second experiment demonstrated that the loss of GSH did not occur if rats were anaesthetized prior to and during nose-only exposure to clean, filtered air or to mixed hydrocarbons. These data appear to be consistent with studies demonstrating depletion in liver GSH levels among rats subjected to restraint stress. Finally, the depletion of GSH that was observed in liver following a single acute exposure was reduced following five daily exposures to clean, filtered air, suggesting the possibility of habituation to restraint in the nose-only exposure chamber. The finding that placement in a nose-only exposure chamber per se yields liver GSH depletion raises the possibility of an interaction between this mode of toxicant exposure and the toxicological effects of certain inhaled test substances.
The efficacy of K-edge filters in diagnostic radiology
International Nuclear Information System (INIS)
Williamson, B.D.P.; van Doorn, T.
1994-01-01
The application of K-edge filters in diagnostic has been investigated by many workers for over twenty years. These investigations have analysed the effects of such filters on image quality and radiation dose as well as the practicalities of their application. This paper presents a synopsis of the published works and concludes that K-edge filters do not perceptibly improve image quality and make only limited reductions in patient dose. K-edge filters are also costly to purchase and potentially result in a reduction in the cost effectiveness of x-ray examinations by increasing the x-ray tube loading. Equivalent contrast enhancement and dose reductions can be achieved by the assiduous choice of non-selective filters. 51 refs., 2 tab., 6 figs
Artifact Reduction of Susceptibility-Weighted Imaging Using a Short-Echo Phase Mask
Energy Technology Data Exchange (ETDEWEB)
Ishimori, Y.; Monma, M. (Dept. of Radiological Sciences, Ibaraki Prefectural Univ. of Health Sciences, Inashiki-gun, Ibaraki (Japan)); Kohno, Y. (Dept. of Neurology, Ibaraki Prefectural Univ. of Health Sciences, Inashiki-gun, Ibaraki (Japan))
2009-11-15
Background: Susceptibility-weighted imaging (SWI) is utilized in magnetic resonance (MR) venography and other applications, but can include artifacts caused by the phase-masking process. Purpose: To demonstrate risks of filter processes used in making phase masks for SWI, and to propose a simple method for reducing artifacts. Material and Methods: Phase linearity related to echo time (TE) was evaluated for the original phase and high-pass-filtered phase using a CuSO{sub 4}-doped water phantom. Effect of filter size of the Hanning window and background homogeneity were also evaluated in a phantom study. Use of a phase mask generated by data with differing magnitudes of TE was attempted in a human study. Shorter TE was used for making the phase mask, and the number of multiplications was increased. As short and long TEs were necessary simultaneously for phase mask and T2 contrast, a dual-echo technique was used. Results: Linearity of TE and phase value collapsed, and an unexpected negative phase appeared in the high-pass-filtered phase. Using a short-TE phase mask, phase-aliasing artifacts were reduced and visibility of deep veins was equivalent to that under conventional methods with an increased number of multiplications. Conclusion: Use of a short-echo phase mask in SWI is useful for reducing artifacts
I6-FPS: Automating the ICMPv6 Filtering Rules
Directory of Open Access Journals (Sweden)
Wan Ali Wan Nor Ashiqin
2018-01-01
Full Text Available Enterprises are required to utilize Internet Control Message Protocol version 6 (ICMPv6 when IPv6 is deployed. In IPv4, Internet Control Message Protocol (ICMP is aggressively filtered by a network administrator while in IPv6, ICMPv6 messages cannot be aggressively filtered due to the function of ICMPv6 message. ICMPv6 security risks increase when ICMPv6 threats and vulnerabilities are exploited. Thus, it is very crucial for enterprises to address the issues. In practice, network researchers must review several resources to identify ICMPv6 related attacks occurring due to the exploitation of ICMPv6 vulnerabilities. Overlooking any of these issues will jeopardize the security of ICMPv6. While conducting the attack scenarios testing, IPv6-Filtering Prototype System (I6-FPS was developed to overcome the deficiency and limited filtering tools that supported IPv6 filtering rules (ip6table. I6-FPS is used to automate and simplify the writing of ip6table and it was developed using PHP5 and Shell script languages. This research revealed that I6-FPS is significant in the initial phase of securing IPv6 deployment as well as focusing on the ICMPv6 filtering rules. The I6-FPS has the potential to be enhanced and developed over time by including more functions to that system in generating specific filtering ip6table rules.
Experimental study of filter cake formation on different filter media
International Nuclear Information System (INIS)
Saleem, M.
2009-01-01
Removal of particulate matter from gases generated in the process industry is important for product recovery as well as emission control. Dynamics of filtration plant depend on operating conditions. The models, that predict filter plant behaviour, involve empirical resistance parameters which are usually derived from limited experimental data and are characteristics of the filter media and filter cake (dust deposited on filter medium). Filter cake characteristics are affected by the nature of filter media, process parameters and mode of filter regeneration. Removal of dust particles from air is studied in a pilot scale jet pulsed bag filter facility resembling closely to the industrial filters. Limestone dust and ambient air are used in this study with two widely different filter media. All important parameters like pressure drop, gas flow rate, dust settling, are recorded continuously at 1s interval. The data is processed for estimation of the resistance parameters. The pressure drop rise on test filter media is compared. Results reveal that the surface of filter media has an influence on pressure drop rise (concave pressure drop rise). Similar effect is produced by partially jet pulsed filter surface. Filter behaviour is also simulated using estimated parameters and a simplified model and compared with the experimental results. Distribution of cake area load is therefore an important aspect of jet pulse cleaned bag filter modeling. Mean specific cake resistance remains nearly constant on thoroughly jet pulse cleaned membrane coated filter bags. However, the trend can not be confirmed without independent cake height and density measurements. Thus the results reveal the importance of independent measurements of cake resistance. (author)
3D Microstructure Modeling of Porous Metal Filters
Directory of Open Access Journals (Sweden)
Vladimír Hejtmánek
2012-09-01
Full Text Available The contribution presents a modified method of stochastic reconstruction of two porous stainless-steel filters. The description of their microstructures was based on a combination of the two-point probability function for the void phase and the lineal-path functions for the void and solid phases. The method of stochastic reconstruction based on simulated annealing was capable of reproducing good connectivity of both phases, which was confirmed by calculating descriptors of the local porosity theory. Theoretical values of permeability were compared with their experimental counterparts measured by means of quasi-stationary permeation of four inert gases.
Energy Technology Data Exchange (ETDEWEB)
Poirier, M. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Burket, P. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Duignan, M. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2015-03-12
The Savannah River Site (SRS) is currently treating radioactive liquid waste with the Actinide Removal Process (ARP) and the Modular Caustic Side Solvent Extraction Unit (MCU). The low filter flux through the ARP has limited the rate at which radioactive liquid waste can be treated. Recent filter flux has averaged approximately 5 gallons per minute (gpm). Salt Batch 6 has had a lower processing rate and required frequent filter cleaning. Savannah River Remediation (SRR) has a desire to understand the causes of the low filter flux and to increase ARP/MCU throughput. In addition, at the time the testing started, SRR was assessing the impact of replacing the 0.1 micron filter with a 0.5 micron filter. This report describes testing of MST filterability to investigate the impact of filter pore size and MST particle size on filter flux and testing of filter enhancers to attempt to increase filter flux. The authors constructed a laboratory-scale crossflow filter apparatus with two crossflow filters operating in parallel. One filter was a 0.1 micron Mott sintered SS filter and the other was a 0.5 micron Mott sintered SS filter. The authors also constructed a dead-end filtration apparatus to conduct screening tests with potential filter aids and body feeds, referred to as filter enhancers. The original baseline for ARP was 5.6 M sodium salt solution with a free hydroxide concentration of approximately 1.7 M.3 ARP has been operating with a sodium concentration of approximately 6.4 M and a free hydroxide concentration of approximately 2.5 M. SRNL conducted tests varying the concentration of sodium and free hydroxide to determine whether those changes had a significant effect on filter flux. The feed slurries for the MST filterability tests were composed of simple salts (NaOH, NaNO_{2}, and NaNO_{3}) and MST (0.2 – 4.8 g/L). The feed slurry for the filter enhancer tests contained simulated salt batch 6 supernate, MST, and filter enhancers.
The ''Nuclear-Karlsruhe'' air-filter system
International Nuclear Information System (INIS)
Berliner, P.; Ohlmeyer, M.; Stotz, W.
1976-01-01
Increasing requirements for exhaust-air filter systems used in nuclear facilities induced the Gesellschaft fuer Kernforschung to develop the ''Nuclear-Karlsruhe'' HEPA filter system. This novel development has profited by experience gained in previous incidents as well as by maitenance and decontamination work performed with different HEPA filter systems. The proved ''Nuclear-Karlsruhe'' system takes equally into account the demands for optimum safety, maximum efficiency and economy, and is distinguished by the following features: (1) The air current is defected by 180 0 in the casing. Deflection causes quite a number of improvements, results in substantial reduction of space requirements, and avoids the dispersion of pollutants to the clean-air side. Besides, the HEPA filter is protected from damage by condensed particles or foreign materials entrained; (2) The ''Nuclear-Karlsruhe'' system allows gas-tight filter replacement. Special replacement collars have been provided at the casing, which allow the tight fastening of replacement bags which are self-locking. (3) In-place testing in the operating condition can be carried out very conveniently because the air is deflected. Minimum leaks in the filter medium or in the filter gasket can be detected by the high-sensitivity visual oil-thread test, which makes leaks distinctly visible as oil mist threads through a transparent front window provided on the clean-air side. The test takes only some minutes and its sensitivity is hardly matched by any other technique. (4) The clamping mechanism is installed outside the casing, i.e. outside the polluted or aggressive media. The contact force is spring-loaded absolutely uniformly to the circular filter gasket. (5) For practical and econmic reasons the filter casings can be locked individually so as to be gas-tight. (6) The entire system is made of stainless or coated steel and metal parts which are corrosion and fire-resistant. (author)
Michelson interferometer based spatial phase shift shearography.
Xie, Xin; Yang, Lianxiang; Xu, Nan; Chen, Xu
2013-06-10
This paper presents a simple spatial phase shift shearography based on the Michelson interferometer. The Michelson interferometer based shearographic system has been widely utilized in industry as a practical nondestructive test tool. In the system, the Michelson interferometer is used as a shearing device to generate a shearing distance by tilting a small angle in one of the two mirrors. In fact, tilting the mirror in the Michelson interferometer also generates spatial frequency shift. Based on this feature, we introduce a simple Michelson interferometer based spatial phase shift shearography. The Fourier transform (FT) method is applied to separate the spectrum on the spatial frequency domain. The phase change due to the loading can be evaluated using a properly selected windowed inverse-FT. This system can generate a phase map of shearography by using only a single image. The effects of shearing angle, spatial resolution of couple charge device camera, and filter methods are discussed in detail. The theory and the experimental results are presented.
An Improved Filtering Method for Quantum Color Image in Frequency Domain
Li, Panchi; Xiao, Hong
2018-01-01
In this paper we investigate the use of quantum Fourier transform (QFT) in the field of image processing. We consider QFT-based color image filtering operations and their applications in image smoothing, sharpening, and selective filtering using quantum frequency domain filters. The underlying principle used for constructing the proposed quantum filters is to use the principle of the quantum Oracle to implement the filter function. Compared with the existing methods, our method is not only suitable for color images, but also can flexibly design the notch filters. We provide the quantum circuit that implements the filtering task and present the results of several simulation experiments on color images. The major advantages of the quantum frequency filtering lies in the exploitation of the efficient implementation of the quantum Fourier transform.
Zhang, B.; Kumar, S.; Yan, L.-S.; Willner, A. E.
2007-12-01
We demonstrate experimentally >3 dB extinction ratio improvement at the output of SOA-based delayed-interference signal converter (DISC) using optical off-centered filtering. Through careful modeling of the carrier and the phase dynamics, we explain in detail the origin of sub-pulses in the wavelength converted output, with an emphasis on the time-resolved frequency chirping of the output signal. Through our simulations we conclude that the sub-pulses and the main-pulses are oppositely chirped, which is also verified experimentally by analyzing the output with a chirp form analyzer. We propose and demonstrate an optical off-center filtering technique which effectively suppresses these sub-pulses. The effects of filter detuning and phase bias adjustment in the delayed-interferometer are experimentally characterized and optimized, leading to a >3 dB extinction ratio enhancement of the output signal.
Survey of life-cycle costs of glass-paper HEPA filters
International Nuclear Information System (INIS)
Moore, P.; Bergman, W.; Gilbert, H.
1992-08-01
We have conducted a survey of the major users of glass-paper HEPA filters in the DOE complex to ascertain the life cycle costs of these filters. Purchase price of the filters is only a minor portion of the costs; the major expenditures are incurred during the removal and disposal of contaminated filters. Through personal interviews, site visits and completion of questionnaires, we have determined the costs associated with the use of HEPA filters in the DOE complex. The total approximate life-cycle cost for a standard (2 in. x 2 in. x 1 in.) glass-paper HEPA filter is $3,000 for one considered low-level waste (LLW), $11,780 for transuranic (TRU) and $15,000 for high-level waste (HLW). The weighted-average cost for a standard HEPA filter in the complex is $4,753
Filtered atmospheric venting of light water reactor containments
International Nuclear Information System (INIS)
Hedgran, A.; Ahlstroem, P.E.; Nilsson, L.; Persson, Aa.
1982-11-01
The aim of filtered venting is to improve the function of the reactor containment in connection with very severe accidents. By equipping the containment with a safety valve for pressure relief and allowing the released gases to pass through an effective filter, it should be possible to achieve a considerable protective effect. The work has involved detailed studies of the core meltdown sequence, how the molten core material runs out of the reactor vessel, what effect it has on concrete and other structures and how final cooling of the molten core material takes place. On the basis of previous Swedish studies, the project has chosen to study a filter concept that consists of a gravel bed of large volume. This filter plant shall not only retain the radioactive particles that escape from the containment through the vent line, but shall also condense the accompanying steam. After the government decided in 1981 that Barsebaeck was to be equipped with filtered venting and issued specifications regarding its performance, the project aimed at obtaining results that could be used to design and verify a plant for filtered venting at the Barsebaeck nuclear power station. As far as the other Swedish nuclear power plants at Oskarshamn, Ringhals and Forsmark are concerned, the results are only applicable to a limited extent. Additional studies are required for these nuclear power plants before the value of filtered venting can be assessed. Based on the results of experiments and analyses, the project has made a safety analysis with Barsebaeck as a reference plant in order to study how the introduction of filtered venting affects the safety level at a station. In summary, the venting function appears to entail a not insignificant reduction of risks for boiling water reactors of the Barsebaeck type. For a number of types of such very severe core accident cases, the filter design studied ensures a substantial reduction of the releases. However it has not been possible within the
Hydraulic modeling of clay ceramic water filters for point-of-use water treatment.
Schweitzer, Ryan W; Cunningham, Jeffrey A; Mihelcic, James R
2013-01-02
The acceptability of ceramic filters for point-of-use water treatment depends not only on the quality of the filtered water, but also on the quantity of water the filters can produce. This paper presents two mathematical models for the hydraulic performance of ceramic water filters under typical usage. A model is developed for two common filter geometries: paraboloid- and frustum-shaped. Both models are calibrated and evaluated by comparison to experimental data. The hydraulic models are able to predict the following parameters as functions of time: water level in the filter (h), instantaneous volumetric flow rate of filtrate (Q), and cumulative volume of water produced (V). The models' utility is demonstrated by applying them to estimate how the volume of water produced depends on factors such as the filter shape and the frequency of filling. Both models predict that the volume of water produced can be increased by about 45% if users refill the filter three times per day versus only once per day. Also, the models predict that filter geometry affects the volume of water produced: for two filters with equal volume, equal wall thickness, and equal hydraulic conductivity, a filter that is tall and thin will produce as much as 25% more water than one which is shallow and wide. We suggest that the models can be used as tools to help optimize filter performance.
Killingsworth, Christopher D; Taylor, Steven M; Patterson, Mark A; Weinberg, Jordan A; McGwin, Gerald; Melton, Sherry M; Reiff, Donald A; Kerby, Jeffrey D; Rue, Loring W; Jordan, William D; Passman, Marc A
2010-05-01
Although contrast venography is the standard imaging method for inferior vena cava (IVC) filter insertion, intravascular ultrasound (IVUS) imaging is a safe and effective option that allows for bedside filter placement and is especially advantageous for immobilized critically ill patients by limiting resource use, risk of transportation, and cost. This study reviewed the effectiveness of a prospectively implemented algorithm for IVUS-guided IVC filter placement in this high-risk population. Current evidence-based guidelines were used to create a clinical decision algorithm for IVUS-guided IVC filter placement in critically ill patients. After a defined lead-in phase to allow dissemination of techniques, the algorithm was prospectively implemented on January 1, 2008. Data were collected for 1 year using accepted reporting standards and a quality assurance review performed based on intent-to-treat at 6, 12, and 18 months. As defined in the prospectively implemented algorithm, 109 patients met criteria for IVUS-directed bedside IVC filter placement. Technical feasibility was 98.1%. Only 2 patients had inadequate IVUS visualization for bedside filter placement and required subsequent placement in the endovascular suite. Technical success, defined as proper deployment in an infrarenal position, was achieved in 104 of the remaining 107 patients (97.2%). The filter was permanent in 21 (19.6%) and retrievable in 86 (80.3%). The single-puncture technique was used in 101 (94.4%), with additional dual access required in 6 (5.6%). Periprocedural complications were rare but included malpositioning requiring retrieval and repositioning in three patients, filter tilt >/=15 degrees in two, and arteriovenous fistula in one. The 30-day mortality rate for the bedside group was 5.5%, with no filter-related deaths. Successful placement of IVC filters using IVUS-guided imaging at the bedside in critically ill patients can be established through an evidence-based prospectively
Cleanable sintered metal filters in hot off-gas systems
International Nuclear Information System (INIS)
Schurr, G.A.
1981-01-01
Filters with sintered metal elements, arranged as tube bundles with backflush air cleaning, are the equivalent of bag filters for high-temperature, harsh environments. They are virtually the only alternative for high-temperature off-gas systems where a renewable, highly efficient particle trap is required. Tests were conducted which show that the sintered metal elements installed in a filter system provide effective powder collection in high-temperature atmospheres over thousands of cleaning cycles. Such a sintered metal filter system is now installed on the experimental defense waste calciner at the Savannah River Laboratory. The experimental results included in this paper were used as the basis for its design
Numerical study of canister filters with alternatives filter cap configurations
Mohammed, A. N.; Daud, A. R.; Abdullah, K.; Seri, S. M.; Razali, M. A.; Hushim, M. F.; Khalid, A.
2017-09-01
Air filtration system and filter play an important role in getting a good quality air into turbo machinery such as gas turbine. The filtration system and filter has improved the quality of air and protect the gas turbine part from contaminants which could bring damage. During separation of contaminants from the air, pressure drop cannot be avoided but it can be minimized thus helps to reduce the intake losses of the engine [1]. This study is focused on the configuration of the filter in order to obtain the minimal pressure drop along the filter. The configuration used is the basic filter geometry provided by Salutary Avenue Manufacturing Sdn Bhd. and two modified canister filter cap which is designed based on the basic filter model. The geometries of the filter are generated by using SOLIDWORKS software and Computational Fluid Dynamics (CFD) software is used to analyse and simulates the flow through the filter. In this study, the parameters of the inlet velocity are 0.032 m/s, 0.063 m/s, 0.094 m/s and 0.126 m/s. The total pressure drop produce by basic, modified filter 1 and 2 is 292.3 Pa, 251.11 Pa and 274.7 Pa. The pressure drop reduction for the modified filter 1 is 41.19 Pa and 14.1% lower compared to basic filter and the pressure drop reduction for modified filter 2 is 17.6 Pa and 6.02% lower compared to the basic filter. The pressure drops for the basic filter are slightly different with the Salutary Avenue filter due to limited data and experiment details. CFD software are very reliable in running a simulation rather than produces the prototypes and conduct the experiment thus reducing overall time and cost in this study.
Design considerations for a suboptimal Kalman filter
Difilippo, D. J.
1995-06-01
In designing a suboptimal Kalman filter, the designer must decide how to simplify the system error model without causing the filter estimation errors to increase to unacceptable levels. Deletion of certain error states and decoupling of error state dynamics are the two principal model simplifications that are commonly used in suboptimal filter design. For the most part, the decisions as to which error states can be deleted or decoupled are based on the designer's understanding of the physics of the particular system. Consequently, the details of a suboptimal design are usually unique to the specific application. In this paper, the process of designing a suboptimal Kalman filter is illustrated for the case of an airborne transfer-of-alignment (TOA) system used for synthetic aperture radar (SAR) motion compensation. In this application, the filter must continuously transfer the alignment of an onboard Doppler-damped master inertial navigation system (INS) to a strapdown navigator that processes information from a less accurate inertial measurement unit (IMU) mounted on the radar antenna. The IMU is used to measure spurious antenna motion during the SAR imaging interval, so that compensating phase corrections can be computed and applied to the radar returns, thereby presenting image degradation that would otherwise result from such motions. The principles of SAR are described in many references, for instance. The primary function of the TOA Kalman filter in a SAR motion compensation system is to control strapdown navigator attitude errors, and to a less degree, velocity and heading errors. Unlike a classical navigation application, absolute positional accuracy is not important. The motion compensation requirements for SAR imaging are discussed in some detail. This TOA application is particularly appropriate as a vehicle for discussing suboptimal filter design, because the system contains features that can be exploited to allow both deletion and decoupling of error
The difficult challenge of a two-phase CFD modelling for all flow regimes
International Nuclear Information System (INIS)
Bestion, D.
2014-01-01
Highlights: • The theoretical difficulties for modelling all flow regimes at CFD scale are identified. • The choice of the number of fields and of the time and space averaging or filtering are discussed and clarified. • Closure issues related to an all flow regime CFD model are listed and the main difficulties are identified. - Abstract: System thermalhydraulic codes model all two-phase flow regimes but they are limited to a macroscopic description. Two-phase CFD tools predict two-phase flow with a much finer space resolution but the current modelling capabilities are limited to dispersed bubbly or droplet flow and separate-phase flow. Much less experience exists on more complex flow regimes which combine the existence of dispersed fields with the presence of large interfaces such as a free surface or a film surface. A list of possible reactor issues which might benefit from an “all flow regime CFD model” is given. The first difficulty is to identify the various types of local flow configuration. It is shown that a 4-field model has much better capabilities than a two-fluid approach to identify most complex regimes. Then the choice between time averaging, space averaging, or even ensemble averaging is discussed. It is shown that only the RANS-2-fluid and a space-filtered 4-field model may be reasonably envisaged. The latter has the capabilities to identify all types of interfaces and should be privileged if a good accuracy is expected or if time fluctuations in intermittent flow have to be predicted while the former may be used when a high accuracy is not necessary and if time fluctuations in intermittent flow are not of interest. Finally the closure issue is presented including wall transfers, interfacial transfers, mass transfers between dispersed and continuous fields, and turbulent transfers. An important effort is required to model all interactions between sub-filter phenomena and the transfers from the sub-filter domain to the simulated domain. The
A New Design Method for the Passive Damped LCL and LLCL Filter-Based Single-Phase Grid-Tied Inverter
DEFF Research Database (Denmark)
Wu, Weimin; He, Yuanbin; Tang, Tianhao
2013-01-01
A higher order passive power filter (LLCL filter) for the grid-tied inverter is becoming attractive for industrial applications due to the possibility to reduce the cost of the copper and the magnetic material. However, similar to the conventional LCL filter, the grid-tied inverter is facing...
Preliminary Analytical Reviews on the Performance of Fibrous Filter
International Nuclear Information System (INIS)
Choi, Yu Jung; Hong, Tae Hyub; Kim, Hyeong-Taek
2015-01-01
The wet type Containment Filtered Vent System (CFVS) is composed of a tank including nozzles in a liquid pool, moisture separators, and a few dry filters such as a metal fiber filter and a molecular sieve. After injecting gases from the containment into the CFVS under severe accident conditions, the CFVS will release decontaminated radioactive materials to the environment. To protect against the release of uncontrolled fission products to the environment, we need to confirm the performance of the CFVS in terms of not only the integral capability but also the capabilities of the individual components. It is crucial to confirm the performance of the metal fiber filter in both analytical and experimental ways. Pressure drop across a filter and collection efficiency are ways to explain the performance of a fibrous filter. Based on data from the literature survey, pressure drop and collection efficiency for a single filter were calculated. The trends of pressure drop and collection efficiencies due to various deposition mechanisms of particles onto the fiber of the filters were roughly confirmed. Therefore, to obtain better quantitative predictions of the performance of the metal fiber filter, a new model able to evaluate the performance of fibrous filters under severe conditions should be developed
Shanmugavadivu, P.; Eliahim Jeevaraj, P. S.
2014-06-01
The Adaptive Iterated Functions Systems (AIFS) Filter presented in this paper has an outstanding potential to attenuate the fixed-value impulse noise in images. This filter has two distinct phases namely noise detection and noise correction which uses Measure of Statistics and Iterated Function Systems (IFS) respectively. The performance of AIFS filter is assessed by three metrics namely, Peak Signal-to-Noise Ratio (PSNR), Mean Structural Similarity Index Matrix (MSSIM) and Human Visual Perception (HVP). The quantitative measures PSNR and MSSIM endorse the merit of this filter in terms of degree of noise suppression and details/edge preservation respectively, in comparison with the high performing filters reported in the recent literature. The qualitative measure HVP confirms the noise suppression ability of the devised filter. This computationally simple noise filter broadly finds application wherein the images are highly degraded by fixed-value impulse noise.
Dark GPC: extended nodal beam areas from binary-only phase
DEFF Research Database (Denmark)
Villangca, Mark Jayson; Bañas, Andrew Rafael; Palima, Darwin
2016-01-01
We show a simplified method of generating extended regions of destructive interference with near arbitrary shapes using the generalized phase contrast (GPC) method. For Gaussian input beams, GPC typically results in a 3×3× intensified user-defined input mask shape against a dark background....... In this work, we investigate conditions wherein GPC’s synthetic reference wave destructively interferes with what is typically the foreground pattern. Using alternate conditions for the input phase mask, the locations of light and darkness are interchanged with respect to typical GPC output mappings. We show...... and flexibility in the output shapes make dark GPC attractive for applications such as optical trapping of low-index particles or superresolution microscopy like stimulated emission depletion...
Decreasing the amplitude deviation of Guassian filter in surface roughness measurements
Liu, Bo; Wang, Yu
2008-12-01
A new approach for decreasing the amplitude characteristic deviation of Guassian filter in surface roughness measurements is presented in this paper. According to Central Limit Theorem, many different Guassian approximation filters could be constructed. By using first-order Butterworth filter and moving average filter to approximate Guassian filter, their directions of amplitude deviation are opposite, and their locations of extreme value are close. So the linear combination of them could reduce the amplitude deviation greatly. The maximum amplitude deviation is only about 0.11% through paralleling them. The algorithm of this new method is simple and its efficiency is high.
Meyer, Mathias; Haubenreisser, Holger; Raupach, Rainer; Schmidt, Bernhard; Lietzmann, Florian; Leidecker, Christianne; Allmendinger, Thomas; Flohr, Thomas; Schad, Lothar R; Schoenberg, Stefan O; Henzler, Thomas
2015-01-01
To prospectively evaluate radiation dose and image quality of a third generation dual-source CT (DSCT) without z-axis filter behind the patient for temporal bone CT. Forty-five patients were either examined on a first, second, or third generation DSCT in an ultra-high-resolution (UHR) temporal bone-imaging mode. On the third generation DSCT system, the tighter focal spot of 0.2 mm(2) removes the necessity for an additional z-axis-filter, leading to an improved z-axis radiation dose efficiency. Images of 0.4 mm were reconstructed using standard filtered-back-projection or iterative reconstruction (IR) technique for previous generations of DSCT and a novel IR algorithm for the third generation DSCT. Radiation dose and image quality were compared between the three DSCT systems. The statistically significantly highest subjective and objective image quality was evaluated for the third generation DSCT when compared to the first or second generation DSCT systems (all p generation examination as compared to the first and second generation DSCT. Temporal bone imaging without z-axis-UHR-filter and a novel third generation IR algorithm allows for significantly higher image quality while lowering effective dose when compared to the first two generations of DSCTs. • Omitting the z-axis-filter allows a reduction in radiation dose of 50% • A smaller focal spot of 0.2 mm (2) significantly improves spatial resolution • Ultra-high-resolution temporal-bone-CT helps to gain diagnostic information of the middle/inner ear.
СURRENT FILTERING IN A THREE-PHASE THREE-WIRE POWER SYSTEM AT ASYMMETRIC SINUSOIDAL VOLTAGES
Directory of Open Access Journals (Sweden)
M. Yu. Artemenko
2018-04-01
Full Text Available Purpose. Investigation of the optimal current distribution between source, shunt active filter and reactive compensator of a three-phase three-wire system that provides consumption of a sinusoidal symmetric current under asymmetric source voltages with minimal power losses was provided. Methodology. The tasks were solved by conducting theoretical and experimental studies. The main provisions of the theory of electrical circuits, the apparatus of mathematical analysis, methods for solving linear differential and algebraic equations, elements of matrix and complex calculus and vector algebra are used. During the development, modern methods and software of computer simulation of electrical engineering complexes and dynamic systems were applied: Matlab-Simulink, MATHCAD. Originality. The principle of compensating current distribution between PAF and reactive compensator of a three-phase three-wire power system with asymmetric sinusoidal voltage was proposed at which the input current is equal to the positive-sequence active current and rms value of PAF current is minimal. The feasibility to compensate the inactive sinusoidal Fryze current by reactive elements under arbitrary combination of load and source parameters was proved and expression for direct calculation of the reactive compensator parameters for generation of inactive Fryze current in the source unbalanced mode was obtained. Practical value. The simulative example for transmission line load showed that combined application of PAF and reactive compensator with the specified distribution of compensating currents ensured a reduction of power losses in 3.273 times and rms value of the SAF current is 12.9 % of rms value total compensation current.
Processes of microbial pesticide degradation in rapid sand filters for treatment of drinking water
DEFF Research Database (Denmark)
Hedegaard, Mathilde Jørgensen; Albrechtsen, Hans-Jørgen
Aerobic rapid sand filters for treatment of groundwater at waterworks were investigated for the ability to remove pesticides. The potential, kinetics and mechanisms of microbial pesticide removal was investigated in microcosms consisting of filter sand, treated water and pesticides in initial...... concentrations of 0.04-2.4 μg/L. The pesticides were removed from the water in microcosms with filter sand from all three investigated sand filters. Within the experimental periode of six to 13 days, 65-85% of the bentazone, 86-93% of the glyphosate, 97-99% of the p-nitrophenol was removed from the water phase...
Nonlinear Filtering with IMM Algorithm for Ultra-Tight GPS/INS Integration
Directory of Open Access Journals (Sweden)
Dah-Jing Jwo
2013-05-01
Full Text Available Abstract This paper conducts a performance evaluation for the ultra-tight integration of a Global positioning system (GPS and an inertial navigation system (INS, using nonlinear filtering approaches with an interacting multiple model (IMM algorithm. An ultra-tight GPS/INS architecture involves the integration of in-phase and quadrature components from the correlator of a GPS receiver with INS data. An unscented Kalman filter (UKF, which employs a set of sigma points by deterministic sampling, avoids the error caused by linearization as in an extended Kalman filter (EKF. Based on the filter structural adaptation for describing various dynamic behaviours, the IMM nonlinear filtering provides an alternative for designing the adaptive filter in the ultra-tight GPS/INS integration. The use of IMM enables tuning of an appropriate value for the process of noise covariance so as to maintain good estimation accuracy and tracking capability. Two examples are provided to illustrate the effectiveness of the design and demonstrate the effective improvement in navigation estimation accuracy. A performance comparison among various filtering methods for ultra-tight integration of GPS and INS is also presented. The IMM based nonlinear filtering approach demonstrates the effectiveness of the algorithm for improved positioning performance.
Active Comb Filter Using Operational Transconductance Amplifier
Directory of Open Access Journals (Sweden)
Rajeev Kumar Ranjan
2014-01-01
Full Text Available A new approach for the design of an active comb filter is proposed to remove the selected frequencies of various signals. The proposed filter is based on only OTAs and capacitors, hence suitable for monolithic integrated circuit implementation. The workability of the circuit is tested using PSPICE for test signals of 60, 180, 300, and 420 Hz as in ECG signal. The results are given in the paper and found to agree well with theory.
Fibre Optic Notch Filter For The Antiproton Decelerator Stochastic Cooling System
Simmonds, Max Vincent John
2016-01-01
The project scope included reverse engineering, upgrading, and recovering the operational conditions of an existing fibre optic notch filter. Once operational, tests were to be preformed to confirm the performance of the temperature stabilisation. The end goal is to use said notch filter in the Antiproton Decelerator (AD) facility at CERN to help aid antimatter research. The notch filter was successfully reverse engineered and then documented. Changes were made in order to increase performance and reliability, and also allow easy integration into the AD. An additional phase was added whereby the notch filter was to be controller via a touchscreen computer, situated next to the filter, allowing engineers to set-up each of the electronic devices used. While one of the devices (Motorised Delay Line) can be controlled by the touchscreen computer, the other two cannot.Due to time constraints and difficulties with the Beckhoff TwincatII programming language, the USB devices were not able to be controlled via the To...
High Degree Cubature Federated Filter for Multisensor Information Fusion with Correlated Noises
Directory of Open Access Journals (Sweden)
Lijun Wang
2016-01-01
Full Text Available This paper proposes an improved high degree cubature federated filter for the nonlinear fusion system with cross-correlation between process and measurement noises at the same time using the fifth-degree cubature rule and the decorrelated principle in its local filters. The master filter of the federated filter adopts the no-reset mode to fuse local estimates of local filters to generate a global estimate according to the scalar weighted rule. The air-traffic maneuvering target tracking simulations are performed between the proposed filter and the fifth-degree cubature federated filter. Simulations results demonstrate that the proposed filter not only can achieve almost the same accuracy as the fifth-degree cubature federated filter with independent white noises, but also has superior performance to the fifth-degree cubature federated filter while the noises are cross-correlated at the same time.
Stabilization of Cs/Re trapping filters using magnesium phosphate ceramics
International Nuclear Information System (INIS)
Jae Hwan Yang; Jin Myeong Shin; Chang Hwa Lee; Chul Min Heo; Min Ku Jeon; Kweon Ho Kang
2013-01-01
The present study a promising method for stabilizing spent filters trapping cesium and technetium by using magnesium phosphate ceramics. Simulated spent filters were fabricated by vaporizing nonradioactive cesium and rhenium (a surrogate of Tc) through the voloxidizer. In order to reveal the characteristics of spent filters, phase structures and thermal stability were analyzed by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and thermogravimetric analysis techniques. Waste forms were fabricated by crushing spent filters and mixing them with magnesium oxide and potassium phosphate. Characterizations of the waste forms were performed by the analyses of compressive strength, apparent porosity, XRD, and scanning electron microscopy. The waste forms showed the excellent mechanical property compared with that of ordinary Portland cement, with the highest compressive strength of 38.1 MPa in the sample with 30 wt% of Cs-filter. Microstructural analysis suggests that waste materials are encapsulated by the binding matrix composed of magnesium potassium phosphate. The results of characterization suggest that fabricating a sound and durable waste form is possible with magnesium phosphate ceramics. (author)
Equalization of Loudspeaker and Room Responses Using Kautz Filters: Direct Least Squares Design
Directory of Open Access Journals (Sweden)
Karjalainen Matti
2007-01-01
Full Text Available DSP-based correction of loudspeaker and room responses is becoming an important part of improving sound reproduction. Such response equalization (EQ is based on using a digital filter in cascade with the reproduction channel to counteract the response errors introduced by loudspeakers and room acoustics. Several FIR and IIR filter design techniques have been proposed for equalization purposes. In this paper we investigate Kautz filters, an interesting class of IIR filters, from the point of view of direct least squares EQ design. Kautz filters can be seen as generalizations of FIR filters and their frequency-warped counterparts. They provide a flexible means to obtain desired frequency resolution behavior, which allows low filter orders even for complex corrections. Kautz filters have also the desirable property to avoid inverting dips in transfer function to sharp and long-ringing resonances in the equalizer. Furthermore, the direct least squares design is applicable to nonminimum-phase EQ design and allows using a desired target response. The proposed method is demonstrated by case examples with measured and synthetic loudspeaker and room responses.
Optimization of phononic filters via genetic algorithms
Energy Technology Data Exchange (ETDEWEB)
Hussein, M I [University of Colorado, Department of Aerospace Engineering Sciences, Boulder, Colorado 80309-0429 (United States); El-Beltagy, M A [Cairo University, Faculty of Computers and Information, 5 Dr. Ahmed Zewail Street, 12613 Giza (Egypt)
2007-12-15
A phononic crystal is commonly characterized by its dispersive frequency spectrum. With appropriate spatial distribution of the constituent material phases, spectral stop bands could be generated. Moreover, it is possible to control the number, the width, and the location of these bands within a frequency range of interest. This study aims at exploring the relationship between unit cell configuration and frequency spectrum characteristics. Focusing on 1D layered phononic crystals, and longitudinal wave propagation in the direction normal to the layering, the unit cell features of interest are the number of layers and the material phase and relative thickness of each layer. An evolutionary search for binary- and ternary-phase cell designs exhibiting a series of stop bands at predetermined frequencies is conducted. A specially formulated representation and set of genetic operators that break the symmetries in the problem are developed for this purpose. An array of optimal designs for a range of ratios in Young's modulus and density are obtained and the corresponding objective values (the degrees to which the resulting bands match the predetermined targets) are examined as a function of these ratios. It is shown that a rather complex filtering objective could be met with a high degree of success. Structures composed of the designed phononic crystals are excellent candidates for use in a wide range of applications including sound and vibration filtering.
Optimization of phononic filters via genetic algorithms
International Nuclear Information System (INIS)
Hussein, M I; El-Beltagy, M A
2007-01-01
A phononic crystal is commonly characterized by its dispersive frequency spectrum. With appropriate spatial distribution of the constituent material phases, spectral stop bands could be generated. Moreover, it is possible to control the number, the width, and the location of these bands within a frequency range of interest. This study aims at exploring the relationship between unit cell configuration and frequency spectrum characteristics. Focusing on 1D layered phononic crystals, and longitudinal wave propagation in the direction normal to the layering, the unit cell features of interest are the number of layers and the material phase and relative thickness of each layer. An evolutionary search for binary- and ternary-phase cell designs exhibiting a series of stop bands at predetermined frequencies is conducted. A specially formulated representation and set of genetic operators that break the symmetries in the problem are developed for this purpose. An array of optimal designs for a range of ratios in Young's modulus and density are obtained and the corresponding objective values (the degrees to which the resulting bands match the predetermined targets) are examined as a function of these ratios. It is shown that a rather complex filtering objective could be met with a high degree of success. Structures composed of the designed phononic crystals are excellent candidates for use in a wide range of applications including sound and vibration filtering
Effect of exposure dose reduction using a compensating filter
International Nuclear Information System (INIS)
Katsuda, Toshizo; Nakajima, Tadashi; Kuwano, Tadao; Ueda, Kouki; Sasaki, Yasuhiro; Yoshida, Jiro
1993-01-01
It is empirically said that the application of the compensating filter leads to a decrease in the exposure dose of the filter-inserted area and an increase in that of the otherwise area. Using the area-dosimeter, comparison was made of exposure doses by the application of the above filter and the otherwise filter in head simple X-P, abdominal angiography and lower extremity X-P. Using the filter for head simple X-P and Mix-Dp phantom, measurement was made of the absorbed dose at the 5 cm-depth to compare the rate of decrease in absorbed dose between the above both areas. Head simple X-P gained a decrease in area dose of 29%. The absorbed dose at the 5 cm-depth in the phantom experiment showed a decrease of over 26% at the filter-inserted area, but little increase at the otherwise area. The above results indicated the interposition of the filter between the X-ray tube and the object to lead to decreases not only in the area dose but also in the patient's exposure dose. (author)
The Rao-Blackwellized Particle Filter: A Filter Bank Implementation
Directory of Open Access Journals (Sweden)
Karlsson Rickard
2010-01-01
Full Text Available For computational efficiency, it is important to utilize model structure in particle filtering. One of the most important cases occurs when there exists a linear Gaussian substructure, which can be efficiently handled by Kalman filters. This is the standard formulation of the Rao-Blackwellized particle filter (RBPF. This contribution suggests an alternative formulation of this well-known result that facilitates reuse of standard filtering components and which is also suitable for object-oriented programming. Our RBPF formulation can be seen as a Kalman filter bank with stochastic branching and pruning.
Directory of Open Access Journals (Sweden)
Coghetto Roland
2015-09-01
Full Text Available We are inspired by the work of Henri Cartan [16], Bourbaki [10] (TG. I Filtres and Claude Wagschal [34]. We define the base of filter, image filter, convergent filter bases, limit filter and the filter base of tails (fr: filtre des sections.
Modelling and simulation of lamp-pumped thallium atomic line filters
International Nuclear Information System (INIS)
Molisch, A.F.
1994-06-01
Atomic Line Filters (ALFs) are ultra-narrow-band, wide-field-of-view optical filters for the detection of weak optical signals embedded in broadband background noise. The central component is a quartz cell filled with atomic vapor where signal photons are absorbed and subsequently re-emitted at a different wavelength. At the 'Institut fuer Nachrichtentechnik und Hochfrequenztechnik', an ALF based on Thallium (Tl) vapor, which is pumped by a Tl spectral lamp, has been under development. The aim of this thesis is to model the physical processes in this filter (especially in the vapor cell) and to make simulations in order to find the optimum design. For this purpose, a theoretical 'toolbox' is to be created, which should be capable of describing quantitatively the various physical effects. The accuracy of the simulation should be about ±10 %, i.e. about the accuracy of the available atomic data. In part I, the physics that form the basis of ALFs are briefly explained. In chapter 1, the principle of an ALF is explained, and the parameters that describe such filters are defined. In the next two chapters, atomic energy levels and atomic line shapes are described. We then summarize the data of the UV and green resonance lines of Thallium. After giving an overview over the methods of description for trapping problems, (Holstein equation, equation-of-radiative-transfer plus rate-equation, Monte Carlo simulation), we describe the (generalized) Milne theory, an approximate method which allows a description of trapping by a differential equation. In part II, we then make use of these formalisms to describe the Tl ALF mathematically. After giving a description of the whole filter system, we show the various influences on the lifetime of the metastable Tl atoms. Then the pump phase of the filter is described. In that phase, we have non-linear trapping in a 3-level system. This problem is solved by a combination of finite-difference solution of the equation of radiative
Are consistent equal-weight particle filters possible?
van Leeuwen, P. J.
2017-12-01
Particle filters are fully nonlinear data-assimilation methods that could potentially change the way we do data-assimilation in highly nonlinear high-dimensional geophysical systems. However, the standard particle filter in which the observations come in by changing the relative weights of the particles is degenerate. This means that one particle obtains weight one, and all other particles obtain a very small weight, effectively meaning that the ensemble of particles reduces to that one particle. For over 10 years now scientists have searched for solutions to this problem. One obvious solution seems to be localisation, in which each part of the state only sees a limited number of observations. However, for a realistic localisation radius based on physical arguments, the number of observations is typically too large, and the filter is still degenerate. Another route taken is trying to find proposal densities that lead to more similar particle weights. There is a simple proof, however, that shows that there is an optimum, the so-called optimal proposal density, and that optimum will lead to a degenerate filter. On the other hand, it is easy to come up with a counter example of a particle filter that is not degenerate in high-dimensional systems. Furthermore, several particle filters have been developed recently that claim to have equal or equivalent weights. In this presentation I will show how to construct a particle filter that is never degenerate in high-dimensional systems, and how that is still consistent with the proof that one cannot do better than the optimal proposal density. Furthermore, it will be shown how equal- and equivalent-weights particle filters fit within this framework. This insight will then lead to new ways to generate particle filters that are non-degenerate, opening up the field of nonlinear filtering in high-dimensional systems.
Synthesis of Cascadable DDCC-Based Universal Filter Using NAM
Directory of Open Access Journals (Sweden)
Huu-Duy Tran
2015-08-01
Full Text Available A novel systematic approach for synthesizing DDCC-based voltage-mode biquadratic universal filters is proposed. The DDCCs are described by infinity-variables’ models of nullor-mirror elements which can be used in the nodal admittance matrix expansion process. Applying the proposed method, the obtained 12 equivalent filters offer the following features: multi-input and two outputs, realization of all five standard filter functions, namely lowpass, bandpass, highpass, notch and allpass, high-input impedance, employing only grounded capacitors and resistors, orthogonal controllability between pole frequency and quality factor, and cascadable, low active and passive sensitivities. The workability of some synthesized filters is verified by HSPICE simulations to demonstrate the feasibility of the proposed method.
Stochastic global optimization as a filtering problem
International Nuclear Information System (INIS)
Stinis, Panos
2012-01-01
We present a reformulation of stochastic global optimization as a filtering problem. The motivation behind this reformulation comes from the fact that for many optimization problems we cannot evaluate exactly the objective function to be optimized. Similarly, we may not be able to evaluate exactly the functions involved in iterative optimization algorithms. For example, we may only have access to noisy measurements of the functions or statistical estimates provided through Monte Carlo sampling. This makes iterative optimization algorithms behave like stochastic maps. Naive global optimization amounts to evolving a collection of realizations of this stochastic map and picking the realization with the best properties. This motivates the use of filtering techniques to allow focusing on realizations that are more promising than others. In particular, we present a filtering reformulation of global optimization in terms of a special case of sequential importance sampling methods called particle filters. The increasing popularity of particle filters is based on the simplicity of their implementation and their flexibility. We utilize the flexibility of particle filters to construct a stochastic global optimization algorithm which can converge to the optimal solution appreciably faster than naive global optimization. Several examples of parametric exponential density estimation are provided to demonstrate the efficiency of the approach.
Efficient design of FIR filter based low-pass differentiators for biomedical signal processing
Directory of Open Access Journals (Sweden)
Wulf Michael
2016-09-01
Full Text Available This paper describes an alternative design of linear phase low-pass differentiators with a finite impulse response (type III FIR filter. To reduce the number of necessary filter coefficients, the differentiator’s transfer function is approximated by a Fourier series of a triangle function. Thereby the filter’s transition steepness towards the stopband is intentionally reduced. It can be shown that the proposed design of low-pass differentiators yields to similar results as other published design recommendations, while the filter order can be significantly reduced.
Characterization of filters and filtration process using X-ray computerized tomography
International Nuclear Information System (INIS)
Maschio, Celio; Arruda, Antonio Celso Fonseca de
1999-01-01
The objective of this work is to present the potential of X-Ray computerized tomography as a tool for internal characterization of filters used in the solid-liquid separation, mainly the water filters. Cartridge filters (for industrial and domestic applications) contaminated with glass beads were used. The scanning process was carried out both with and without contaminant in the filter to compare the attenuation coefficient of the clean filter and the contaminated filter. The images showed that is possible the mapping the internal structure of the filters and the distribution of the contaminant, permitting a local analysis, that is not possible through the standard tests used by the manufactures. These standard tests reveal only global characteristics of the filter media. The possibility of application for manufacturing process control was also shown, because the non invasive nature is a important advantage of the technique, which also permitted damage detection in filters submitted to severe operational conditions. (author)
Hildebrand, Ainslie M; Iansavichus, Arthur V; Haynes, R Brian; Wilczynski, Nancy L; Mehta, Ravindra L; Parikh, Chirag R; Garg, Amit X
2014-04-01
We frequently fail to identify articles relevant to the subject of acute kidney injury (AKI) when searching the large bibliographic databases such as PubMed, Ovid Medline or Embase. To address this issue, we used computer automation to create information search filters to better identify articles relevant to AKI in these databases. We first manually reviewed a sample of 22 992 full-text articles and used prespecified criteria to determine whether each article contained AKI content or not. In the development phase (two-thirds of the sample), we developed and tested the performance of >1.3-million unique filters. Filters with high sensitivity and high specificity for the identification of AKI articles were then retested in the validation phase (remaining third of the sample). We succeeded in developing and validating high-performance AKI search filters for each bibliographic database with sensitivities and specificities in excess of 90%. Filters optimized for sensitivity reached at least 97.2% sensitivity, and filters optimized for specificity reached at least 99.5% specificity. The filters were complex; for example one PubMed filter included >140 terms used in combination, including 'acute kidney injury', 'tubular necrosis', 'azotemia' and 'ischemic injury'. In proof-of-concept searches, physicians found more articles relevant to topics in AKI with the use of the filters. PubMed, Ovid Medline and Embase can be filtered for articles relevant to AKI in a reliable manner. These high-performance information filters are now available online and can be used to better identify AKI content in large bibliographic databases.
Air filters for use at nuclear facilities
Energy Technology Data Exchange (ETDEWEB)
Linder, P [Aktiebolaget Atomenergi, Studsvik, Nykoeping (Sweden)
1970-12-01
The ventilation system of a nuclear facility plays a vital role in ensuring that the air in working areas and the environment remains free from radioactive contamination. An earlier IAEA publication, Techniques for Controlling Air Pollution from the Operation of Nuclear Facilities, Safety Series No. 17, deals with the design and operation of ventilation systems at nuclear facilities. These systems are usually provided with air-cleaning devices which remove the contaminants from the air. This publication is intended as a guide to those who are concerned with the design of air-filtering systems and with the testing, operation and maintenance of air-filter installations at nuclear facilities. Emphasis is mainly placed on so-called high-efficiency particulate air filters (HEPA filters) and on providing general information on them. Besides describing the usual filter types, their dimensions and construction materials, the guidebook attempts to explain their properties and behaviour under different operating conditions. It also gives advice on testing and handling the filters so that effective and safe performance is ensured. The guidebook should serve as an introduction to the use of high efficiency particulate air filters in countries where work with radioactive materials has only recently commenced. The list of references at the end of the book indicates sources of more advanced information for those who already have comprehensive experience in this field. It is assumed here that the filters are obtained from a manufacturer, and the guidebook thus contains no information on the design and development of the filter itself, nor does it deal with the cleaning of the intake air to a plant, with gas sorption or protective respiratory equipment.
Air filters for use at nuclear facilities
International Nuclear Information System (INIS)
Linder, P.
1970-01-01
The ventilation system of a nuclear facility plays a vital role in ensuring that the air in working areas and the environment remains free from radioactive contamination. An earlier IAEA publication, Techniques for Controlling Air Pollution from the Operation of Nuclear Facilities, Safety Series No. 17, deals with the design and operation of ventilation systems at nuclear facilities. These systems are usually provided with air-cleaning devices which remove the contaminants from the air. This publication is intended as a guide to those who are concerned with the design of air-filtering systems and with the testing, operation and maintenance of air-filter installations at nuclear facilities. Emphasis is mainly placed on so-called high-efficiency particulate air filters (HEPA filters) and on providing general information on them. Besides describing the usual filter types, their dimensions and construction materials, the guidebook attempts to explain their properties and behaviour under different operating conditions. It also gives advice on testing and handling the filters so that effective and safe performance is ensured. The guidebook should serve as an introduction to the use of high efficiency particulate air filters in countries where work with radioactive materials has only recently commenced. The list of references at the end of the book indicates sources of more advanced information for those who already have comprehensive experience in this field. It is assumed here that the filters are obtained from a manufacturer, and the guidebook thus contains no information on the design and development of the filter itself, nor does it deal with the cleaning of the intake air to a plant, with gas sorption or protective respiratory equipment
A New LCL -Filter With In-Series Parallel Resonant Circuit for Single-Phase Grid-Tied Inverter
DEFF Research Database (Denmark)
Wu, Weimin; Sun, Yunjie; Lin, Zhe
2014-01-01
are investigated for the conventional LCL-filter-based system. Based on this, a modified LCL-filter topology using an extra parallel LrCr resonant circuit is proposed to reduce the total inductance value, without increasing the capacitive reactive power. The validity is verified through the experiments on a 500-W...
Bombick, D W; Bombick, B R; Ayres, P H; Putnam, K; Avalos, J; Borgerding, M F; Doolittle, D J
1997-09-01
A novel carbon filter has been developed which primarily reduces the amount of certain vapor phase constituents of tobacco smoke with greater efficiency than the charcoal filters of cigarettes currently in the market. In vitro indicators of genotoxic and cytotoxic potential were used to compare the cigarette smoke condensate (particulate phase) or whole cigarette smoke (vapor phase and particulate phase) from cigarettes containing the novel carbon filter with smoke condensate or whole smoke from commercial or prototype cigarettes not containing the novel carbon filter. Ames bacterial mutagenicity, sister chromatid exchange (SCE) in Chinese hamster ovary (CHO) cells, and neutral red cytotoxicity assays in CHO cells were utilized to assess the genotoxic and cytotoxic potential of the cigarette smoke condensates. SCE and neutral red cytotoxicity assays were utilized to assess the genotoxic and cytotoxic potential of the whole smoke. As expected, the novel carbon filter did not significantly affect the genotoxic or cytotoxic activity of the smoke condensate, although we did observe that the use of low-nitrogen tobacco reduced the mutagenicity of the condensate in Salmonella typhimurium strain TA98. However, the whole smoke from cigarettes containing the novel carbon filter demonstrated significant reductions in genotoxic and cytotoxic potential compared to cigarettes without the novel carbon filter. The toxicity of the smoke was correlated (r = 0.7662 for cytotoxicity and r = 0.7562 for SCE induction) to the aggregate mass of several vapor phase components (acetone, acetaldehyde, acrolein, acrylonitrile, 1,3-butadiene, ammonia, NOx, HCN, benzene, isoprene, and formaldehyde) in the smoke of the cigarettes utilized in this study. In conclusion, this novel carbon filter, which significantly reduced the amount of carbonyls and other volatiles in mainstream cigarette smoke, resulted in significant reductions in the genotoxic and cytotoxic activity of the smoke as measured
High-performance information search filters for CKD content in PubMed, Ovid MEDLINE, and EMBASE.
Iansavichus, Arthur V; Hildebrand, Ainslie M; Haynes, R Brian; Wilczynski, Nancy L; Levin, Adeera; Hemmelgarn, Brenda R; Tu, Karen; Nesrallah, Gihad E; Nash, Danielle M; Garg, Amit X
2015-01-01
Finding relevant articles in large bibliographic databases such as PubMed, Ovid MEDLINE, and EMBASE to inform care and future research is challenging. Articles relevant to chronic kidney disease (CKD) are particularly difficult to find because they are often published under different terminology and are found across a wide range of journal types. We used computer automation within a diagnostic test assessment framework to develop and validate information search filters to identify CKD articles in large bibliographic databases. 22,992 full-text articles in PubMed, Ovid MEDLINE, or EMBASE. 1,374,148 unique search filters. We established the reference standard of article relevance to CKD by manual review of all full-text articles using prespecified criteria to determine whether each article contained CKD content or not. We then assessed filter performance by calculating sensitivity, specificity, and positive predictive value for the retrieval of CKD articles. Filters with high sensitivity and specificity for the identification of CKD articles in the development phase (two-thirds of the sample) were then retested in the validation phase (remaining one-third of the sample). We developed and validated high-performance CKD search filters for each bibliographic database. Filters optimized for sensitivity reached at least 99% sensitivity, and filters optimized for specificity reached at least 97% specificity. The filters were complex; for example, one PubMed filter included more than 89 terms used in combination, including "chronic kidney disease," "renal insufficiency," and "renal fibrosis." In proof-of-concept searches, physicians found more articles relevant to the topic of CKD with the use of these filters. As knowledge of the pathogenesis of CKD grows and definitions change, these filters will need to be updated to incorporate new terminology used to index relevant articles. PubMed, Ovid MEDLINE, and EMBASE can be filtered reliably for articles relevant to CKD. These
Application of DFT Filter Banks and Cosine Modulated Filter Banks in Filtering
Lin, Yuan-Pei; Vaidyanathan, P. P.
1994-01-01
None given. This is a proposal for a paper to be presented at APCCAS '94 in Taipei, Taiwan. (From outline): This work is organized as follows: Sec. II is devoted to the construction of the new 2m channel under-decimated DFT filter bank. Implementation and complexity of this DFT filter bank are discussed therein. IN a similar manner, the new 2m channel cosine modulated filter bank is discussed in Sec. III. Design examples are given in Sec. IV.
Alternating minimisation for glottal inverse filtering
International Nuclear Information System (INIS)
Bleyer, Ismael Rodrigo; Lybeck, Lasse; Auvinen, Harri; Siltanen, Samuli; Airaksinen, Manu; Alku, Paavo
2017-01-01
A new method is proposed for solving the glottal inverse filtering (GIF) problem. The goal of GIF is to separate an acoustical speech signal into two parts: the glottal airflow excitation and the vocal tract filter. To recover such information one has to deal with a blind deconvolution problem. This ill-posed inverse problem is solved under a deterministic setting, considering unknowns on both sides of the underlying operator equation. A stable reconstruction is obtained using a double regularization strategy, alternating between fixing either the glottal source signal or the vocal tract filter. This enables not only splitting the nonlinear and nonconvex problem into two linear and convex problems, but also allows the use of the best parameters and constraints to recover each variable at a time. This new technique, called alternating minimization glottal inverse filtering (AM-GIF), is compared with two other approaches: Markov chain Monte Carlo glottal inverse filtering (MCMC-GIF), and iterative adaptive inverse filtering (IAIF), using synthetic speech signals. The recent MCMC-GIF has good reconstruction quality but high computational cost. The state-of-the-art IAIF method is computationally fast but its accuracy deteriorates, particularly for speech signals of high fundamental frequency ( F 0). The results show the competitive performance of the new method: With high F 0, the reconstruction quality is better than that of IAIF and close to MCMC-GIF while reducing the computational complexity by two orders of magnitude. (paper)
Directory of Open Access Journals (Sweden)
GAN Yu
2015-09-01
Full Text Available Attitude determination directly by carrier phase observation makes optimal use of observation and attitude constraints. The phase models based on misalignment angle and multiplicative quaternion error are derived. The state models for attitude estimation with and without external angular rate sensors are both erected. The attitude errors are estimated by adaptively robust filtering, in which the adaptive factors of ambiguity and attitude error are decided respectively following the idea of multi adaptive factor filtering. The factor of attitude is determined by a three-section function containing Ratio. Adaptively robust filtering makes the best use of constraint and historical information, fusing them in the calculation of float solution. As the accuracy of float solution and the structure of covariance matrix are improved greatly, the fix solution can be searched efficiently using LAMBDA (least-squares ambiguity decorrelation adjustment method merely, perfectly fulfilling the real-time requirement. Field test of a ship-based three-antenna attitude system is used to validate the proposed method. It is showed that direct attitude determination based on adaptively robust filtering has obvious advantages in efficiency and reliability.
Energy Technology Data Exchange (ETDEWEB)
Guan, J.J. [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Wang, H.Q. [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Qin, L.Z., E-mail: qin8394@163.com [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Liao, B.; Liang, H. [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Li, B. [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China)
2017-04-15
The CrCN coatings were fabricated onto Si (1 1 1) wafers and SUS304 stainless steel plates using filtered cathodic vacuum arc deposition (FCVAD) technique under different flow ratios of N{sub 2}/C{sub 2}H{sub 2} gas mixture. The morphology, crystalline structure and chemical composition of the coatings were characterized. It was found that the grain size reduce with increasing carbon content, which makes the CrCN coatings refined and smooth. The quasi-one-dimensional carbolite phase was also found in CrN host lattice with C{sub 2}H{sub 2} content ranging from 5% to 20%, and it will be evolved into amorphous carbon and amorphous CN{sub x} phases as C{sub 2}H{sub 2} content exceeds 20%. Moreover, we examined the mechanical and tribological properties of the CrCN coatings, and the experimental results confirmed that the friction coefficient of the coatings descend to the lowest value as 0.39 with 30% C{sub 2}H{sub 2} content, due to the graphite (sp{sup 2} C−C) phase embed in CrN host lattice; while the chromium carbon (Cr{sub 3}C{sub 2}) and diamond (sp{sup 3} C−C) phases may give rise to the increase of the coating hardness with the highest value at 23.97 GPa under 20% C{sub 2}H{sub 2} content.
The fluence research of filter material for fast neutron fluence measurement
International Nuclear Information System (INIS)
Tang Xiding
2010-01-01
When the fast neutron fluence is measured by radioactivation techniques in the nuclear reactor the fast neutron is also filtered a little by the thermal neutron filter material, and if the filter material thickness increase the filtered fast neutron increases therewith. For fast neutron fluenc measurement, there are only cadmium, boron and gadolinium three elements filtering fluence can be calculated ordinarily. In order to calculate the filtered fast neutron fluence of the all elements in the filter material, the many total cross sections of nuclides had checked out from nuclear cross section data library, converted them into the same energy group structure, then element's total cross section, compound's total cross section and multilayer filters' total cross section had calculated from these total cross sections with same energy group structure, a new cross section data library can be obtained lastly through merging these cross sections into the old cross section data library used for neutron fluence measurement. The calculation analysis indicates that the results of the unit 2 surveillance capsule U of DAYA Bay NPP and the unit 1 surveillance capsule A of the Second Nuclear Power Plant of Qinshan by considering the all elements subtracting iron are smaller about 1.5% and 2.6% respectively than the ones only to consider cadmium, boron. The old measured results accord with the new values under the measurement uncertainty, are reliable. The new results are more accuracy. (authors)
Hybrid viscous damper with filtered integral force feedback control
DEFF Research Database (Denmark)
Høgsberg, Jan; Brodersen, Mark L.
2016-01-01
In hybrid damper systems active control devices are usually introduced to enhance the performance of otherwise passive dampers. In the present paper a hybrid damper concept is comprised of a passive viscous damper placed in series with an active actuator and a force sensor. The actuator motion...... is controlled by a filtered integral force feedback strategy, where the main feature is the filter, which is designed to render a damper force that in a phase-plane representation operates in front of the corresponding damper velocity. It is demonstrated that in the specific parameter regime where the damper...
A Study of Parallel Operation of an active Filter and passive Filters
DEFF Research Database (Denmark)
Chen, Zhe; Blaabjerg, Frede; Pedersen, John Kim
2002-01-01
This paper reports investigations of the parallel operations of a current controlled active filter and passive filters in a system with current harmonic sources. The task of reactive power and harmonic compensation is shared by the active filter and passive filters. The passive filters are used...... arrangements of the active and passive filters can operate relatively independently, also the compensation flexibility of the active filter can be fully exploited, such as one active filter for several harmonic sources.The simulation studies on various systems have been performed to evaluate the effectiveness...... of the systems. The results show that the power factor is corrected by the passive filters, harmonics are minimized by both active and passive filters and overloading of the filter system can be avoided....
Künzi, R.
2015-06-15
Power converters require passive low-pass filters which are capable of reducing voltage ripples effectively. In contrast to signal filters, the components of power filters must carry large currents or withstand large voltages, respectively. In this paper, three different suitable filter struc tures for d.c./d.c. power converters with inductive load are introduced. The formulas needed to calculate the filter components are derived step by step and practical examples are given. The behaviour of the three discussed filters is compared by means of the examples. P ractical aspects for the realization of power filters are also discussed.
Filtering algorithm for dotted interferences
Energy Technology Data Exchange (ETDEWEB)
Osterloh, K., E-mail: kurt.osterloh@bam.de [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Buecherl, T.; Lierse von Gostomski, Ch. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany); Zscherpel, U.; Ewert, U. [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Bock, S. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany)
2011-09-21
An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible.
Filtering algorithm for dotted interferences
International Nuclear Information System (INIS)
Osterloh, K.; Buecherl, T.; Lierse von Gostomski, Ch.; Zscherpel, U.; Ewert, U.; Bock, S.
2011-01-01
An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible.
Wang, Hongyu; He, Jiajie; Yang, Kai
2010-01-01
This study evaluated the partial nitrification performances of two biofilm filters over a synthetic non-ammonium-rich wastewater at a 20°C room temperature under both limited DO (∼2.0 mg/L) and unlimited DO (∼4.0 mg/L) conditions. The two filters were each of 80 cm long and used different biofilm carriers: activated carbon and ceramic granule. Results showed that partial nitrification was accomplished for both filters under the limited DO condition. However, the effluent NO(2)-N was higher in the ceramic granule filter than in the activated carbon filter, and was less susceptible to the influent COD/N changes. Further investigation into the water phase COD and NH(4)-N depth profiles and bacteria population within the two filters showed that by putting upper filter layer (upstream) to confront relatively higher influent COD/N ratios, the filtration process naturally put lower filter layers (downstream) relatively more favorable for nitrifying bacteria (ammonia oxidizing bacteria in this study) to prosper, making the filter depth left for nitrification a crucial factor for the effectiveness of nitrification with a filter. The potentially different porous flow velocities of the two filters might be the reason to cause their different partial nitrification performances, with a lower porous flow velocity (the ceramic granule filter) favoring partial nitrification more. In summation, DO, filter depth, and filtration speed should be played together to successfully operate a biofilm filter for partial nitrification.
Acoustic wave filter based on periodically poled lithium niobate.
Courjon, Emilie; Bassignot, Florent; Ulliac, Gwenn; Benchabane, Sarah; Ballandras, Sylvain
2012-09-01
Solutions for the development of compact RF passive transducers as an alternative to standard surface or bulk acoustic wave devices are receiving increasing interest. This article presents results on the development of an acoustic band-pass filter based on periodically poled ferroelectric domains in lithium niobate. The fabrication of periodically poled transducers (PPTs) operating in the range of 20 to 650 MHz has been achieved on 3-in (76.2-mm) 500-μm-thick wafers. This kind of transducer is able to excite elliptical as well as longitudinal modes, yielding phase velocities of about 3800 and 6500 ms(-1), respectively. A new type of acoustic band-pass filter is proposed, based on the use of PPTs instead of the SAWs excited by classical interdigital transducers. The design and the fabrication of such a filter are presented, as well as experimental measurements of its electrical response and transfer function. The feasibility of such a PPT-based filter is thereby demonstrated and the limitations of this method are discussed.
Decoupled deblurring filter and its application to elastic migration and inversion
Feng, Zongcai
2017-08-17
We present a decoupled deblurring filter that approximates the multiparameter Hessian inverse by using local filters to approximate its submatrices for the same and different parameter classes. Numerical tests show that the filter not only reduces the footprint noise, balances the amplitudes and increases the resolution of the elastic migration images, but also mitigates the crosstalk artifacts. When used as a preconditioner, it accelerates the convergence rate for elastic inversion.
Non-specific filtering of beta-distributed data.
Wang, Xinhui; Laird, Peter W; Hinoue, Toshinori; Groshen, Susan; Siegmund, Kimberly D
2014-06-19
Non-specific feature selection is a dimension reduction procedure performed prior to cluster analysis of high dimensional molecular data. Not all measured features are expected to show biological variation, so only the most varying are selected for analysis. In DNA methylation studies, DNA methylation is measured as a proportion, bounded between 0 and 1, with variance a function of the mean. Filtering on standard deviation biases the selection of probes to those with mean values near 0.5. We explore the effect this has on clustering, and develop alternate filter methods that utilize a variance stabilizing transformation for Beta distributed data and do not share this bias. We compared results for 11 different non-specific filters on eight Infinium HumanMethylation data sets, selected to span a variety of biological conditions. We found that for data sets having a small fraction of samples showing abnormal methylation of a subset of normally unmethylated CpGs, a characteristic of the CpG island methylator phenotype in cancer, a novel filter statistic that utilized a variance-stabilizing transformation for Beta distributed data outperformed the common filter of using standard deviation of the DNA methylation proportion, or its log-transformed M-value, in its ability to detect the cancer subtype in a cluster analysis. However, the standard deviation filter always performed among the best for distinguishing subgroups of normal tissue. The novel filter and standard deviation filter tended to favour features in different genome contexts; for the same data set, the novel filter always selected more features from CpG island promoters and the standard deviation filter always selected more features from non-CpG island intergenic regions. Interestingly, despite selecting largely non-overlapping sets of features, the two filters did find sample subsets that overlapped for some real data sets. We found two different filter statistics that tended to prioritize features with
Kalman and particle filtering methods for full vehicle and tyre identification
Bogdanski, Karol; Best, Matthew C.
2018-05-01
This paper considers identification of all significant vehicle handling dynamics of a test vehicle, including identification of a combined-slip tyre model, using only those sensors currently available on most vehicle controller area network buses. Using an appropriately simple but efficient model structure, all of the independent parameters are found from test vehicle data, with the resulting model accuracy demonstrated on independent validation data. The paper extends previous work on augmented Kalman Filter state estimators to concentrate wholly on parameter identification. It also serves as a review of three alternative filtering methods; identifying forms of the unscented Kalman filter, extended Kalman filter and particle filter are proposed and compared for effectiveness, complexity and computational efficiency. All three filters are suited to applications of system identification and the Kalman Filters can also operate in real-time in on-line model predictive controllers or estimators.
On a multiscale approach for filter efficiency simulations
Iliev, Oleg
2014-07-01
Filtration in general, and the dead end depth filtration of solid particles out of fluid in particular, is intrinsic multiscale problem. The deposition (capturing of particles) essentially depends on local velocity, on microgeometry (pore scale geometry) of the filtering medium and on the diameter distribution of the particles. The deposited (captured) particles change the microstructure of the porous media what leads to change of permeability. The changed permeability directly influences the velocity field and pressure distribution inside the filter element. To close the loop, we mention that the velocity influences the transport and deposition of particles. In certain cases one can evaluate the filtration efficiency considering only microscale or only macroscale models, but in general an accurate prediction of the filtration efficiency requires multiscale models and algorithms. This paper discusses the single scale and the multiscale models, and presents a fractional time step discretization algorithm for the multiscale problem. The velocity within the filter element is computed at macroscale, and is used as input for the solution of microscale problems at selected locations of the porous medium. The microscale problem is solved with respect to transport and capturing of individual particles, and its solution is postprocessed to provide permeability values for macroscale computations. Results from computational experiments with an oil filter are presented and discussed.
Nonlinear image filtering within IDP++
Energy Technology Data Exchange (ETDEWEB)
Lehman, S.K.; Wieting, M.G.; Brase, J.M.
1995-02-09
IDP++, image and data processing in C++, is a set of a signal processing libraries written in C++. It is a multi-dimension (up to four dimensions), multi-data type (implemented through templates) signal processing extension to C++. IDP++ takes advantage of the object-oriented compiler technology to provide ``information hiding.`` Users need only know C, not C++. Signals or data sets are treated like any other variable with a defined set of operators and functions. We here some examples of the nonlinear filter library within IDP++. Specifically, the results of MIN, MAX median, {alpha}-trimmed mean, and edge-trimmed mean filters as applied to a real aperture radar (RR) and synthetic aperture radar (SAR) data set.
Digital filter algorithm study and simulation of SSRF feedback system
International Nuclear Information System (INIS)
Han Lifeng; Yuan Renxian; Ye Kairong
2008-01-01
Least Square Fitting was used to design a FIR filter of the transverse feedback system for the Shanghai Synchrotron Radiation Facility (SSRF). The algorithm helped us to set appropriate gain and phase at special frequency points. This reduced the power needed for damping the beam oscillations, which was proved by System View signal simulation. And with AT (Accelerator Tool) simulation, the Gain calculation and settings to the output signals from the FIR filter were deduced. The relationship between the Kicker power and the system damping time was also given. (authors)
Kimura, T; Iizuka, A; Taniguchi, Y; Ishikuro, A; Hongo, T; Inoue, H; Ogura, A
2003-01-01
The influence on the quality of images by measurement of a sensitivity distribution and the use of a sensitivity compensation filter was considered using an opposite-type phased array coil and volume-type phased array coil. With the opposite-type phased array coil, the relation between coil interval and filter was investigated for the image intensity correction (IIC) filter, surface coil intensity correction (SCIC) filter (GE), and the Normalize filter (SIEMENS). The SCIC filter and Normalize filter showed distance dependability over the coil interval of signal-to-noise ratio (SNR) and uniformity was observed, and the existence of an optimal coil interval was suggested. Moreover, with the IIC filter, distance dependability over a coil interval was small, and the decrease in contrast with use was remarkable. On the other hand, with the volume-type phased array coil, the overlap of an array element was investigated to determine the influence it had on sensitivity distribution. Although the value stabilized in t...
Fujita, Hideaki; Akagi, Hirofumi
1991-01-01
The authors present a combined system with a passive filter and a small-rated active filter, both connected in series with each other. The passive filter removes load produced harmonics just as a conventional filter does. The active filter plays a role in improving the filtering characteristics of the passive filter. This results in a great reduction of the required rating of the active filter and in eliminating all the limitations faced by using only the passive filter, leading to a practica...
Precise and versatile formula for birefringent filters
Shao, Zhongxing
1996-07-01
In an investigation of extraordinary-(E-) ray behavior and the index of refraction for E waves in a uniaxial crystal, a precise and versatile formula for birefringent filters, based on the exact construction of the optical path difference, is set up with neither the approximation Delta n = no - ne less than or equals no (or n e), nor the ambiguity sin( theta )/sin(rw) = ne. The exact construction gives the correct variation of the position and the dimension in each path, yielding the path difference while the filter is tuning. The formula is applicable not only to a filter with its optical axis parallel to the entrance surface (FAPS) but also to a filter with its axis inclined to the surface (FAIS). Also, the formula indicates that a FAIS allows laser wavelengths to be tuned over a wider range than does a FAPS. The origin of the wider range is interpreted to be the greater variation in the index for the FAIS while the filter is tuning. With the help of the formula we design a FAIS for tuning a cw 42.25.Lc.
Directory of Open Access Journals (Sweden)
B. K. Shayakhmetov
2014-01-01
Full Text Available In the work there are presented the results of studying the filtering elements weight changes when heated. For all the variants of filtering elements at the primary stages of heating there is characteristic increasing their linear dimensions due to their thermal expansion. It was established that using hydrolyzed ethyl silicate as a binder, as well as water solution of liquid glass with addition of aluminum powder in the refractory material permits to obtain filtering elements without high-temperature solid-phase sintering.
Distributed SLAM Using Improved Particle Filter for Mobile Robot Localization
Directory of Open Access Journals (Sweden)
Fujun Pei
2014-01-01
Full Text Available The distributed SLAM system has a similar estimation performance and requires only one-fifth of the computation time compared with centralized particle filter. However, particle impoverishment is inevitably because of the random particles prediction and resampling applied in generic particle filter, especially in SLAM problem that involves a large number of dimensions. In this paper, particle filter use in distributed SLAM was improved in two aspects. First, we improved the important function of the local filters in particle filter. The adaptive values were used to replace a set of constants in the computational process of importance function, which improved the robustness of the particle filter. Second, an information fusion method was proposed by mixing the innovation method and the number of effective particles method, which combined the advantages of these two methods. And this paper extends the previously known convergence results for particle filter to prove that improved particle filter converges to the optimal filter in mean square as the number of particles goes to infinity. The experiment results show that the proposed algorithm improved the virtue of the DPF-SLAM system in isolate faults and enabled the system to have a better tolerance and robustness.
Energy Technology Data Exchange (ETDEWEB)
Pettersson, S.
2009-07-01
During the past two decades, active power filters have increasingly grown their popularity as a viable method for improving electric power quality. The main reasons for this have been the advent of fast self-commutating solid-state devices, the progression of digital technology and the improved sensor technology. Four-wire active power filters provide an efficient solution for improving the quality of supply in grounded three-phase systems or three-phase systems with neutral conductors, which are commonly used for powering residential, office and public buildings. Four-wire active power filters are applicable in compensating current harmonics, reactive power, neutral current and load phase imbalance.This thesis presents a comparative study of microcontroller controlled four-wire voltage and current source shunt active power filters. The study includes two voltage source topologies and a current source topology with two different dc-link energy storage structures, which are compared on the basis of their filtering properties, filtering performance and efficiency. The obtained results are used for determining the suitability of current source technology for four-wire active power filtering and finding the most viable four-wire shunt active power filter topology. One commonly recognized disadvantage of the current source active power filter has always been the bulky dc-link inductor. To reduce the size of the dc-link inductor, an alternative dc-link structure for current source active power filters was introduced in the late 80's. The hybrid energy storage consists of both inductive and capacitive energy storage elements, two diodes and two controllable semiconductor switching devices. Since the capacitive element is used as a main storage unit, the inductance of the dc-link inductor can be considerably reduced. However, the original dc current control method proposed is not able to utilize the full potential of the hybrid energy storage and the inductance
Assessing the anti-fungal efficiency of filters coated with zinc oxide nanoparticles
Decelis, Stephen; Sardella, Davide; Triganza, Thomas; Brincat, Jean-Pierre; Gatt, Ruben; Valdramidis, Vasilis P.
2017-05-01
Air filters support fungal growth, leading to generation of conidia and volatile organic compounds, causing allergies, infections and food spoilage. Filters that inhibit fungi are therefore necessary. Zinc oxide (ZnO) nanoparticles have anti-fungal properties and therefore are good candidates for inhibiting growth. Two concentrations (0.012 M and 0.12 M) were used to coat two types of filters (melt-blown and needle-punched) for three different periods (0.5, 5 and 50 min). Rhizopus stolonifer and Penicillium expansum isolated from spoiled pears were used as test organisms. Conidial suspensions of 105 to 103 spores ml-1 were prepared in Sabouraud dextrose agar at 50°C, and a modified slide-culture technique was used to test the anti-fungal properties of the filters. Penicillium expansum was the more sensitive organism, with inhibition at 0.012 M at only 0.5 min coating time on the needle-punched filter. The longer the coating time, the more effective inhibition was for both organisms. Furthermore, it was also determined that the coating process had only a slight effect on the Young's Moduli of the needle-punched filters, while the Young's Moduli of the melt-blown filters is more susceptible to the coating method. This work contributes to the assessment of the efficacy of filter coating with ZnO nanopaticles aimed at inhibiting fungal growth.
Vapour HF release of airgap-based UV-visible optical filters
Ghaderi, M.; Ayerden, N.P.; De Graaf, G.; Wolffenbuttel, R.F.
2015-01-01
The design and CMOS-compatible fabrication of airgap-based optical filters in a surface micromachining process with sacrificial release using thevapour phase is presented. An airgap-dielectric layer combination offers a higher refractive index contrast, as compared to the conventional
International Nuclear Information System (INIS)
Meyer, Mathias; Haubenreisser, Holger; Schoenberg, Stefan O.; Henzler, Thomas; Raupach, Rainer; Schmidt, Bernhard; Leidecker, Christianne; Allmendinger, Thomas; Flohr, Thomas; Lietzmann, Florian; Schad, Lothar R.
2015-01-01
To prospectively evaluate radiation dose and image quality of a third generation dual-source CT (DSCT) without z-axis filter behind the patient for temporal bone CT. Forty-five patients were either examined on a first, second, or third generation DSCT in an ultra-high-resolution (UHR) temporal bone-imaging mode. On the third generation DSCT system, the tighter focal spot of 0.2 mm 2 removesthe necessity for an additional z-axis-filter, leading to an improved z-axis radiation dose efficiency. Images of 0.4 mm were reconstructed using standard filtered-back-projection or iterative reconstruction (IR) technique for previous generations of DSCT and a novel IR algorithm for the third generation DSCT. Radiation dose and image quality were compared between the three DSCT systems. The statistically significantly highest subjective and objective image quality was evaluated for the third generation DSCT when compared to the first or second generation DSCT systems (all p < 0.05). Total effective dose was 63 %/39 % lower for the third generation examination as compared to the first and second generation DSCT. Temporal bone imaging without z-axis-UHR-filter and a novel third generation IR algorithm allows for significantly higher image quality while lowering effective dose when compared to the first two generations of DSCTs. (orig.)
Particle Kalman Filtering: A Nonlinear Bayesian Framework for Ensemble Kalman Filters*
Hoteit, Ibrahim
2012-02-01
This paper investigates an approximation scheme of the optimal nonlinear Bayesian filter based on the Gaussian mixture representation of the state probability distribution function. The resulting filter is similar to the particle filter, but is different from it in that the standard weight-type correction in the particle filter is complemented by the Kalman-type correction with the associated covariance matrices in the Gaussian mixture. The authors show that this filter is an algorithm in between the Kalman filter and the particle filter, and therefore is referred to as the particle Kalman filter (PKF). In the PKF, the solution of a nonlinear filtering problem is expressed as the weighted average of an “ensemble of Kalman filters” operating in parallel. Running an ensemble of Kalman filters is, however, computationally prohibitive for realistic atmospheric and oceanic data assimilation problems. For this reason, the authors consider the construction of the PKF through an “ensemble” of ensemble Kalman filters (EnKFs) instead, and call the implementation the particle EnKF (PEnKF). It is shown that different types of the EnKFs can be considered as special cases of the PEnKF. Similar to the situation in the particle filter, the authors also introduce a resampling step to the PEnKF in order to reduce the risk of weights collapse and improve the performance of the filter. Numerical experiments with the strongly nonlinear Lorenz-96 model are presented and discussed.
Energy Technology Data Exchange (ETDEWEB)
Sagutdinov, R.Sh.; Batoyev, D.
1982-01-01
The device for USSR certificate of authorship 792439 is improved in order to raise reliability of isolating the damage zone by including into operation an antenna filter for voltage of zero sequence (AFNIP) only during the operating time of the electrical unit in incomplete phase mode. The newly introduced circuit breaker contract of the inlet relay of the voltage filter for reverse sequence is connected between the outlet of the AFNIP and the ground. The device additionally has a time relay which is connected to the outlet of the voltage filter of reverse sequence. The circuit breaker contact of the inlet relay AFNIP is connected in series to the closure contact of the time relay and the winding of the second outlet relay of the actuating mechanism.
Directory of Open Access Journals (Sweden)
Y. A. Bladyko
2010-01-01
Full Text Available The paper contains definition of a smoothing factor which is suitable for any rectifier filter. The formulae of complex smoothing factors have been developed for simple and complex passive filters. The paper shows conditions for application of calculation formulae and filters.
Zhang, Baocheng; Liu, Teng; Yuan, Yunbin
2018-06-01
The integer ambiguity resolution enabled precise point positioning (PPP-RTK) has been proven advantageous in a wide range of applications. The realization of PPP-RTK concerns the isolation of satellite phase biases (SPBs) and other corrections from a network of Global Positioning System (GPS) reference receivers. This is generally based on Kalman filter in order to achieve real-time capability, in which proper modeling of the dynamics of various types of unknowns remains crucial. This paper seeks to gain insight into how to reasonably deal with the dynamic behavior of the estimable receiver phase biases (RPBs). Using dual-frequency GPS data collected at six colocated receivers over days 50-120 of 2015, we analyze the 30-s epoch-by-epoch estimates of L1 and wide-lane (WL) RPBs for each receiver pair. The dynamics observed in these estimates are a combined effect of three factors, namely the random measurement noise, the multipath and the ambient temperature. The first factor can be overcome by turning to a real-time filter and the second by considering the use of a sidereal filtering. The third factor has an effect only on the WL, and this effect appears to be linear. After accounting for these three factors, the low-pass-filtered, sidereal-filtered, epoch-by-epoch estimates of L1 RPBs follow a random walk process, whereas those of WL RPBs are constant over time. Properly modeling the dynamics of RPBs is vital, as it ensures the best convergence of the Kalman-filtered, between-satellite single-differenced SPB estimates to their correct values and, in turn, shortens the time-to-first-fix at user side.
Zhang, Baocheng; Liu, Teng; Yuan, Yunbin
2017-11-01
The integer ambiguity resolution enabled precise point positioning (PPP-RTK) has been proven advantageous in a wide range of applications. The realization of PPP-RTK concerns the isolation of satellite phase biases (SPBs) and other corrections from a network of Global Positioning System (GPS) reference receivers. This is generally based on Kalman filter in order to achieve real-time capability, in which proper modeling of the dynamics of various types of unknowns remains crucial. This paper seeks to gain insight into how to reasonably deal with the dynamic behavior of the estimable receiver phase biases (RPBs). Using dual-frequency GPS data collected at six colocated receivers over days 50-120 of 2015, we analyze the 30-s epoch-by-epoch estimates of L1 and wide-lane (WL) RPBs for each receiver pair. The dynamics observed in these estimates are a combined effect of three factors, namely the random measurement noise, the multipath and the ambient temperature. The first factor can be overcome by turning to a real-time filter and the second by considering the use of a sidereal filtering. The third factor has an effect only on the WL, and this effect appears to be linear. After accounting for these three factors, the low-pass-filtered, sidereal-filtered, epoch-by-epoch estimates of L1 RPBs follow a random walk process, whereas those of WL RPBs are constant over time. Properly modeling the dynamics of RPBs is vital, as it ensures the best convergence of the Kalman-filtered, between-satellite single-differenced SPB estimates to their correct values and, in turn, shortens the time-to-first-fix at user side.
Energy Technology Data Exchange (ETDEWEB)
Elzibak, A; Fatemi-Ardekani, A; Soliman, A; Mashouf, S; Safigholi, H; Ravi, A; Morton, G; Song, WY [Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Han, D [Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); University of California, San Diego, La Jolla, CA (United States)
2015-06-15
Purpose: To identify and analyze the appearance of calcifications and brachytherapy seeds on magnitude and phase MRI images and to investigate whether they can be distinguished from each other on corrected phase images for application to prostate and breast low dose rate (LDR) implant dosimetry. Methods: An agar-based gel phantom containing two LDR brachytherapy seeds (Advantage Pd-103, IsoAid, 0.8mm diameter, 4.5mm length) and two spherical calcifications (large: 7mm diameter and small: 4mm diameter) was constructed and imaged on a 3T Philips MR scanner using a 16-channel head coil and a susceptibility weighted imaging (SWI) sequence (2mm slices, 320mm FOV, TR/ TE= 26.5/5.3ms, 15 degree flip angle). The phase images were unwrapped and corrected using a 32×32, 2D Hanning high pass filter to remove background phase noise. Appearance of the seeds and calcifications was assessed visually and quantitatively using Osirix (http://www.osirix-viewer.com/). Results: As expected, calcifications and brachytherapy seeds appeared dark (hypointense) relative to the surrounding gel on the magnitude MRI images. The diameter of each seed without the surrounding artifact was measured to be 0.1 cm on the magnitude image, while diameters of 0.79 and 0.37 cm were measured for the larger and smaller calcifications, respectively. On the corrected phase images, the brachytherapy seeds and the calcifications appeared bright (hyperintense). The diameter of the seeds was larger on the phase images (0.17 cm) likely due to the dipole effect. Conclusion: MRI has the best soft tissue contrast for accurate organ delineation leading to most accurate implant dosimetry. This work demonstrated that phase images can potentially be useful in identifying brachytherapy seeds and calcifications in the prostate and breast due to their bright appearance, which helps in their visualization and quantification for accurate dosimetry using MR-only. Future work includes optimizing phase filters to best identify
International Nuclear Information System (INIS)
Gorthi, Sai Siva; Rastogi, Pramod
2009-01-01
A noisy wrapped phase map is the end-output of commonly employed phase estimation methods in digital holographic interferometry. Hence filtering and unwrapping are necessary to obtain continuous phase distributions. This paper introduces a new approach for phase estimation in digital holographic interferometry using the polynomial phase transform. The proposed approach directly provides an accurate estimation of the unwrapped phase distribution from a noisy reconstructed interference field, thereby bypassing cumbersome and error-prone filtering and 2D phase unwrapping procedures
The Influence of Grain Refiners on the Efficiency of Ceramic Foam Filters
Towsey, Nicholas; Schneider, Wolfgang; Krug, Hans-Peter; Hardman, Angela; Keegan, Neil J.
An extensive program of work has been carried out to evaluate the efficiency of ceramic foam filters under carefully controlled conditions. Work reported at previous TMS meetings showed that in the absence of grain refiners, ceramic foam filters have the capacity for high filtration efficiency and consistent, reliable performance. The current phase of the investigation focuses on the impact grain refiner additions have on filter performance. The high filtration efficiencies obtained using 50 or 80ppi CFF's in the absence of grain refiners diminish when Al-3%Ti-1%B grain refiners are added. This, together with the impact of incoming inclusion loading on filter performance and the level of grain refiner addition are considered in detail. The new generation Al-3%Ti-0.15%C grain refiner has also been included. At typical addition levels (1kg/tonne) the effect on filter efficiency is similar to that for TiB2based grain refiners. The work was again conducted on a production scale using AA1050 alloy. Metal quality was determined using LiMCA and PoDFA. Spent filters were also analysed.
Probabilistic relevance ranking for collaborative filtering
Wang, J.; Robertson, S.; De Vries, A.P.; Reinders, M.J.T.
2008-01-01
Collaborative filtering is concerned with making recommendations about items to users. Most formulations of the problem are specifically designed for predicting user ratings, assuming past data of explicit user ratings is available. However, in practice we may only have implicit evidence of user
Optimum FIR filter for sampled signals in presence of jitter
Cattaneo, Paolo Walter
1996-02-01
The requirements of the integrated readout electronics for calorimetry at high luminosity hadron colliders pose new challenges both to hardware design and to the performance of signal processing algorithms. Both aspects have been treated in detail by the FERMI(RD16) collaboration [C. Alippi et al., Nucl. Instr. and Meth. A 344 (1994) 180], from which this work has been motivated. The estimation of the amplitude of sampled signals is usually performed with a digital FIR filter, or with a more sophisticated non linear digital filter using FIR filters as building blocks [S.J. Inkinen and J. Niittylahti, Trainable FIR-order statistic hybrid filters, to be published in IEEE Trans. Circuits and Systems; H. Alexanian et al., FERMI Collaboration, Optimized digital feature extraction in the FERMI microsystem Nucl. Instr. and Meth. A 357 (1995)]. In presence of significant signal phase jitter with respect to the clock, the phase dependence of the filter output can be a major source of error. This is especially true for measurements of large amplitudes for which the effect of electronic noise becomes negligible. This paper reports on the determination of digital FIR filters that optimize the signal over noise ratio due to known jitter distributions for different filter lengths. As the presence of electronic noise is neglected, the results are mainly relevant for measurements of large signals. FERMI is a collaboration with the aim of designing integrated electronics for the read out of calorimeter detectors in particle physics experiments at hadron colliders. It includes: CERN, Geneva, Switzerland; Department of Physics and Measurement Technology, University of Linköping, Sweden; Center for Industrial Microelectronics and Materials Technology, University of Linköping, Sweden; LPNHE Universities Paris VI-VII, Paris, France; Dipartimento di Elettronica, Politecnico di Milano, Italy, Sezine INFN, Pavia, Italy; Dipartimento di Fisica Nucleare e Teorica dell'Universitá e Sezione
Convex blind image deconvolution with inverse filtering
Lv, Xiao-Guang; Li, Fang; Zeng, Tieyong
2018-03-01
Blind image deconvolution is the process of estimating both the original image and the blur kernel from the degraded image with only partial or no information about degradation and the imaging system. It is a bilinear ill-posed inverse problem corresponding to the direct problem of convolution. Regularization methods are used to handle the ill-posedness of blind deconvolution and get meaningful solutions. In this paper, we investigate a convex regularized inverse filtering method for blind deconvolution of images. We assume that the support region of the blur object is known, as has been done in a few existing works. By studying the inverse filters of signal and image restoration problems, we observe the oscillation structure of the inverse filters. Inspired by the oscillation structure of the inverse filters, we propose to use the star norm to regularize the inverse filter. Meanwhile, we use the total variation to regularize the resulting image obtained by convolving the inverse filter with the degraded image. The proposed minimization model is shown to be convex. We employ the first-order primal-dual method for the solution of the proposed minimization model. Numerical examples for blind image restoration are given to show that the proposed method outperforms some existing methods in terms of peak signal-to-noise ratio (PSNR), structural similarity (SSIM), visual quality and time consumption.
Doutsi, Effrosyni; Fillatre, Lionel; Antonini, Marc; Gaulmin, Julien
2018-07-01
This paper introduces a novel filter, which is inspired by the human retina. The human retina consists of three different layers: the Outer Plexiform Layer (OPL), the inner plexiform layer, and the ganglionic layer. Our inspiration is the linear transform which takes place in the OPL and has been mathematically described by the neuroscientific model "virtual retina." This model is the cornerstone to derive the non-separable spatio-temporal OPL retina-inspired filter, briefly renamed retina-inspired filter, studied in this paper. This filter is connected to the dynamic behavior of the retina, which enables the retina to increase the sharpness of the visual stimulus during filtering before its transmission to the brain. We establish that this retina-inspired transform forms a group of spatio-temporal Weighted Difference of Gaussian (WDoG) filters when it is applied to a still image visible for a given time. We analyze the spatial frequency bandwidth of the retina-inspired filter with respect to time. It is shown that the WDoG spectrum varies from a lowpass filter to a bandpass filter. Therefore, while time increases, the retina-inspired filter enables to extract different kinds of information from the input image. Finally, we discuss the benefits of using the retina-inspired filter in image processing applications such as edge detection and compression.
Performance Analysis of Local Ensemble Kalman Filter
Tong, Xin T.
2018-03-01
Ensemble Kalman filter (EnKF) is an important data assimilation method for high-dimensional geophysical systems. Efficient implementation of EnKF in practice often involves the localization technique, which updates each component using only information within a local radius. This paper rigorously analyzes the local EnKF (LEnKF) for linear systems and shows that the filter error can be dominated by the ensemble covariance, as long as (1) the sample size exceeds the logarithmic of state dimension and a constant that depends only on the local radius; (2) the forecast covariance matrix admits a stable localized structure. In particular, this indicates that with small system and observation noises, the filter error will be accurate in long time even if the initialization is not. The analysis also reveals an intrinsic inconsistency caused by the localization technique, and a stable localized structure is necessary to control this inconsistency. While this structure is usually taken for granted for the operation of LEnKF, it can also be rigorously proved for linear systems with sparse local observations and weak local interactions. These theoretical results are also validated by numerical implementation of LEnKF on a simple stochastic turbulence in two dynamical regimes.
Replacement of fine particle purification filter of the PHT purification system - 15083
International Nuclear Information System (INIS)
Lee, D.S.
2015-01-01
The increase of chalk river unidentified deposit (CRUD), a particulate corrosion product in PHT (primary heat transport) system with increased operating years of a nuclear power plant causes: -) the problems of increased heavy water decomposition and deuterium formation reaction due to catalytic reaction with CRUD, -) damage to PHT pump seal due to a corrosion product, -) damage to fuel channel closure seal, and increased radiation exposure of workers due to elevated dose rate in steam generator water chamber. Wolsung unit 3 and 4 have replaced fine filter media in PHT purification system in phases reducing the pore size of the filter media (5 μm → 2 μm → 1 μm → 0.45 μm) to solve this problem. The phased replacement of fine filter media by the one with a smaller pore size reduced CRUD in PHT system significantly and also radiation dose rate in steam generator water chamber. Accordingly, many problems related to the aging of a plant (including increased radiation exposure of workers during outage, damage to mechanical seal of PHT pump) have been solved. (author)
Kalman filters for real-time magnetic island phase tracking
Borgers, D. P.; Lauret, M.; M.R. de Baar,
2013-01-01
For control of neoclassical tearing modes (NTMs) and the resulting rotating magnetic islands in tokamak plasmas, the frequency and phase of the magnetic islands need to be accurately tracked in real-time. In previous experiments on TEXTOR, this was achieved using a phase-locked loop (PLL). For ASDEX
Case of a Misplaced IVC Filter: A Lesson to Learn
International Nuclear Information System (INIS)
Sharma, Sanjay; Mukund, Amar; Agarwal, Sandeep; Srivastava, Deep N.
2010-01-01
The inferior vena cava (IVC) filter insertion is a well established procedure to prevent significant pulmonary embolism in selected situations. It is generally considered straight forward without significant complications. We report an interesting case of a young postpartum woman in whom an IVC filter was misplaced in the right gonadal vein. This complication is only rarely reported. Presence of prominent right gonadal vein must always be kept in mind during trans-jugular placement of infra renal filter in the IVC in post partum women.
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang
2015-01-01
Active damping and harmonic compensation are two common challenges faced by LCL-filtered voltage source converters. To manage them holistically, this paper begins by proposing a virtual RC damper in parallel with the passive filter capacitor. The virtual damper is actively inserted by feeding back...... the passive capacitor current through a high-pass filter, which indirectly, furnishes two superior features. They are the mitigation of phase lag experienced by a conventional damper and the avoidance of instability caused by the negative resistance inserted unintentionally. Moreover, with the virtual RC...
Braile vena cava filter and greenfield filter in terms of centralization.
de Godoy, José Maria Pereira; Menezes da Silva, Adinaldo A; Reis, Luis Fernando; Miquelin, Daniel; Torati, José Luis Simon
2013-01-01
The aim of this study was to evaluate complications experienced during implantation of the Braile Vena Cava filter (VCF) and the efficacy of the centralization mechanism of the filter. This retrospective cohort study evaluated all Braile Biomédica VCFs implanted from 2004 to 2009 in Hospital de Base Medicine School in São José do Rio Preto, Brazil. Of particular concern was the filter's symmetry during implantation and complications experienced during the procedure. All the angiographic examinations performed during the implantation of the filters were analyzed in respect to the following parameters: migration of the filter, non-opening or difficulties in the implantation and centralization of the filter. A total of 112 Braile CVFs were implanted and there were no reports of filter opening difficulties or in respect to migration. Asymmetry was observed in 1/112 (0.9%) cases. A statistically significant difference was seen on comparing historical data on decentralization of the Greenfield filter with the data of this study. The Braile Biomédico filter is an evolution of the Greenfield filter providing improved embolus capture and better implantation symmetry.
Percutaneous retrieval of a vena cava filter from the right atrium: case report
International Nuclear Information System (INIS)
Rasuli, P.; Mehran, R.; French, G.; Turek, M.; Lalonde, K.A.; Cardinal, P.
2000-01-01
Migration of vena cava filters can occur spontaneously, but it can also occur as a result of entanglement of the filter with a guidewire, particularly during 'blind' (unguided) insertion of a central venous line. When a filter migrates to the heart, traditional practice has been either to leave the filter in place or to remove it surgically by means of open heart surgery and cardiopulmonary bypass. We found only 6 reports of successful percutaneous retrieval or repositioning of a vena cava filter (Table 1). We describe a new interventional technique for retrieving a filter from the right atrium and a novel endosurgical method for removing a filter from the innominate vein. (author)
Percutaneous retrieval of a vena cava filter from the right atrium: case report
Energy Technology Data Exchange (ETDEWEB)
Rasuli, P. [The Ottawa Hospital and University of Ottawa, Dept. of Radiology, Ottawa, Ontario (Canada); Mehran, R. [The Ottawa Hospital and University of Ottawa, Dept. of Thoracic Surgery, Ottawa, Ontario (Canada); French, G. [The Ottawa Hospital and University of Ottawa, Dept. of Radiology, Ottawa, Ontario (Canada); Turek, M. [The Ottawa Hospital and University of Ottawa, Dept. of Internal Medicine, Ottawa, Ontario (Canada); Lalonde, K.A. [The Ottawa Hospital and University of Ottawa, Dept. of Thoracic Surgery, Ottawa, Ontario (Canada); Cardinal, P. [The Ottawa Hospital and University of Ottawa, Dept. of Internal Medicine, Ottawa, Ontario (Canada)
2000-07-01
Migration of vena cava filters can occur spontaneously, but it can also occur as a result of entanglement of the filter with a guidewire, particularly during 'blind' (unguided) insertion of a central venous line. When a filter migrates to the heart, traditional practice has been either to leave the filter in place or to remove it surgically by means of open heart surgery and cardiopulmonary bypass. We found only 6 reports of successful percutaneous retrieval or repositioning of a vena cava filter (Table 1). We describe a new interventional technique for retrieving a filter from the right atrium and a novel endosurgical method for removing a filter from the innominate vein. (author)
van der Laan, H; van Halem, D; Smeets, P W M H; Soppe, A I A; Kroesbergen, J; Wubbels, G; Nederstigt, J; Gensburger, I; Heijman, S G J
2014-03-15
In 2012 more than 4 million people used a ceramic pot filter (CPF) as household water treatment system for their daily drinking water needs. In the normal production protocol most low cost filters are impregnated with a silver solution to enhance the microbial removal efficiency. The aim of this study was to determine the role of silver during the filtration and subsequent storage. Twenty-two CPFs with three different silver applications (non, only outside and both sides) were compared in a long-term loading experiment with Escherichia coli (K12 and WR1) and MS2 bacteriophages in natural challenge water under highly controlled laboratory circumstances. No significant difference in Log Removal Values were found between the filters with different silver applications. The results show that the storage time in the receptacle is the dominant parameter to reach E. coli inactivation by silver, and not the contact time during the filtration phase. The hypothesis that the absence of silver would enhance the virus removal, due to biofilm formation on the ceramic filter element, could not be confirmed. The removal effectiveness for viruses is still of major concern for the CPF. This study suggests that the ceramic pot filter characteristics, such as burnt material content, do not determine E. coli removal efficacies, but rather the contact time with silver during storage is the dominant parameter to reach E. coli inactivation. Copyright © 2013 Elsevier Ltd. All rights reserved.
A novel square-root domain realization of first order all-pass filter
ÖLMEZ, Sinem; ÇAM, Uğur
2010-01-01
In this paper, a new square-root domain, first order, all-pass filter based on the MOSFET square law is presented. The proposed filter is designed by using nonlinear mapping on the state variables of a state space description of the transfer function. To the best knowledge of the authors, the filter is the first square-root domain first order all-pass structure designed by using state space synthesis method in the literature. The center frequency of the all-pass filter is not only a...
Hydrodynamics of heavy liquid metal coolant processes and filtering apparatus
International Nuclear Information System (INIS)
Albert K Papovyants; Yuri I Orlov; Pyotr N Martynov; Yuri D Boltoev
2005-01-01
Full text of publication follows: To optimize the design of filters for cleaning heavy liquid metal coolant (HLMC) from suspended impurities and choose appropriate filter material, the contribution is considered of different mechanisms of delivery and retention of these impurities from the coolant flow, which is governed by its specificity as a thermodynamically instable disperse system to a large extent. It is shown that the buildup of deposits in the filter is favored by the hydrodynamic regime with minimum filtration rates being due to the predominance in the suspension of the fine-dispersed solid phase (oxides Fe 3 O 4 , Cr 2 O 3 and so on). With concentrating the last mentioned phase in filter material pores or stagnant zones, coagulation structuration is possible, which is accompanied by sharp local increase in the viscosity and strength of the solid phase medium being built from liquid metal, i.e. slag sedimentary deposits. In rather extended pores, disintegration of such structures is possible, which is accompanied by sedimentation of large particles produced due to sticking together at coagulation. The analytical solution of the problem of particle sedimentation due to diffusion indicated that in the case under consideration, this mechanism takes place for particles less than ∼ 0,05 μm in size, which is specified by the fact that the time of their delivery to the filter material surface is longer than that of the coolant being in the filter. The London-Van-der-Waals molecular forces play a crucial role in the stage of retention of a separate particle. The constant of the molecular interaction between a spherical particle and the flat surface has been estimated for the chosen value of the gap between the contacting bodies, being dependent on the wetting angle. The sufficient condition for d p -diameter particle capture by the adhesion force field (with a gap of H ≅ 30 nm) is that it be brought by the appropriate forces at a distance from the wall equal
Implementational Aspects of the Contourlet Filter Bank and Application in Image Coding
Directory of Open Access Journals (Sweden)
Truong T. Nguyen
2009-02-01
Full Text Available This paper analyzed the implementational aspects of the contourlet filter bank (or the pyramidal directional filter bank (PDFB, and considered its application in image coding. First, details of the binary tree-structured directional filter bank (DFB are presented, including a modification to minimize the phase delay factor and necessary steps for handling rectangular images. The PDFB is viewed as an overcomplete filter bank, and the directional filters are expressed in terms of polyphase components of the pyramidal filter bank and the conventional DFB. The aliasing effect of the conventional DFB and the Laplacian pyramid to the directional filters is then considered, and the conditions for reducing this effect are presented. The new filters obtained by redesigning the PDFBs satisfying these requirements have much better frequency responses. A hybrid multiscale filter bank consisting of the PDFB at higher scales and the traditional maximally decimated wavelet filter bank at lower scales is constructed to provide a sparse image representation. A novel embedded image coding system based on the image decomposition and a morphological dilation algorithm is then presented. The coding algorithm efficiently clusters the significant coefficients using progressive morphological operations. Context models for arithmetic coding are designed to exploit the intraband dependency and the correlation existing among the neighboring directional subbands. Experimental results show that the proposed coding algorithm outperforms the current state-of-the-art wavelet-based coders, such as JPEG2000, for images with directional features.
Determination of ultraviolet filter activity on coconut oil cosmetic cream
Widiyati, Eni
2017-08-01
A research on determination of ultraviolet (UV) filter activity of cosmetic cream with coconut oil as raw material has been done. The cream was made by mixing the oil phase (coconut oil, stearic acid, lanolin and cetyl alcohol) at 70°C and the water phase (glycerin, aquadest and triethanolamine) at 70°C, while stirring until reached a temperature of 35°C. It was made also a cream with inorganic sunscreen TiO2 and organic sunscreen benzophenone-3 as a comparison. To study the UV filter activity, each cream was determined the UV absorption using UV spectrophotometer. The results show that cosmetic cream with coconut oil as raw material absorbs UV rays in the region of UV-C, whereas the cream with TiO2 absorbs the UV rays from UV-C to UV-A and cream with benzophenone-3 absorbs the UV rays from UV-B to UV-A region. This means that, the cosmetic cream with coconut oil as raw material has an activity as UV-C filter. If this cream is expected to have an activity as a sunscreen, it must be added an inorganic or organic sunscreen or a mixture of both as an active materials.
BPSK Receiver Based on Recursive Adaptive Filter with Remodulation
Directory of Open Access Journals (Sweden)
N. Milosevic
2011-12-01
Full Text Available This paper proposes a new binary phase shift keying (BPSK signal receiver intended for reception under conditions of significant carrier frequency offsets. The recursive adaptive filter with least mean squares (LMS adaptation is used. The proposed receiver has a constant, defining the balance between the recursive and the nonrecursive part of the filter, whose proper choice allows a simple construction of the receiver. The correct choice of this parameter could result in unitary length of the filter. The proposed receiver has performance very close to the performance of the BPSK receiver with perfect frequency synchronization, in a wide range of frequency offsets (plus/minus quarter of the signal bandwidth. The results obtained by the software simulation are confirmed by the experimental results measured on the receiver realized with the universal software radio peripheral (USRP, with the baseband signal processing at personal computer (PC.
All-Pass Filter Based Linear Voltage Controlled Quadrature Oscillator
Directory of Open Access Journals (Sweden)
Koushick Mathur
2017-01-01
Full Text Available A linear voltage controlled quadrature oscillator implemented from a first-order electronically tunable all-pass filter (ETAF is presented. The active element is commercially available current feedback amplifier (AD844 in conjunction with the relatively new Multiplication Mode Current Conveyor (MMCC device. Electronic tunability is obtained by the control node voltage (V of the MMCC. Effects of the device nonidealities, namely, the parasitic capacitors and the roll-off poles of the port-transfer ratios of the device, are shown to be negligible, even though the usable high-frequency ranges are constrained by these imperfections. Subsequently the filter is looped with an electronically tunable integrator (ETI to implement the quadrature oscillator (QO. Experimental responses on the voltage tunable phase of the filter and the linear-tuning law of the quadrature oscillator up to 9.9 MHz at low THD are verified by simulation and hardware tests.
Multi-dimensional medical images compressed and filtered with wavelets
International Nuclear Information System (INIS)
Boyen, H.; Reeth, F. van; Flerackers, E.
2002-01-01
Full text: Using the standard wavelet decomposition methods, multi-dimensional medical images can be compressed and filtered by repeating the wavelet-algorithm on 1D-signals in an extra loop per extra dimension. In the non-standard decomposition for multi-dimensional images the areas that must be zero-filled in case of band- or notch-filters are more complex than geometric areas such as rectangles or cubes. Adding an additional dimension in this algorithm until 4D (e.g. a 3D beating heart) increases the geometric complexity of those areas even more. The aim of our study was to calculate the boundaries of the formed complex geometric areas, so we can use the faster non-standard decomposition to compress and filter multi-dimensional medical images. Because a lot of 3D medical images taken by PET- or SPECT-cameras have only a few layers in the Z-dimension and compressing images in a dimension with a few voxels is usually not worthwhile, we provided a solution in which one can choose which dimensions will be compressed or filtered. With the proposal of non-standard decomposition on Daubechies' wavelets D2 to D20 by Steven Gollmer in 1992, 1D data can be compressed and filtered. Each additional level works only on the smoothed data, so the transformation-time halves per extra level. Zero-filling a well-defined area alter the wavelet-transform and then performing the inverse transform will do the filtering. To be capable to compress and filter up to 4D-Images with the faster non-standard wavelet decomposition method, we have investigated a new method for calculating the boundaries of the areas which must be zero-filled in case of filtering. This is especially true for band- and notch filtering. Contrary to the standard decomposition method, the areas are no longer rectangles in 2D or cubes in 3D or a row of cubes in 4D: they are rectangles expanded with a half-sized rectangle in the other direction for 2D, cubes expanded with half cubes in one and quarter cubes in the
Developing particulate thin filter using coconut fiber for motor vehicle emission
Wardoyo, A. Y. P.; Juswono, U. P.; Riyanto, S.
2016-03-01
Amounts of motor vehicles in Indonesia have been recognized a sharply increase from year to year with the increment reaching to 22 % per annum. Meanwhile motor vehicles produce particulate emissions in different sizes with high concentrations depending on type of vehicles, fuels, and engine capacity. Motor Particle emissions are not only to significantly contribute the atmosphric particles but also adverse to human health. In order to reduce the particle emission, it is needed a filter. This study was aimed to develop a thin filter using coconut fiber to reduce particulate emissions for motor vehicles. The filter was made of coconut fibers that were grinded into power and mixed with glues. The filter was tested by the measurements of particle concentrations coming out from the vehicle exhaust directly and the particle concentrations after passing through the filter. The efficiency of the filter was calculated by ratio of the particle concentrations before comming in the filter to the particle conentrations after passing through the filter. The results showed that the efficiency of the filter obtained more than 30 %. The efficiency increases sharply when a number of the filters are arranged paralelly.
Simmons, R B; Crow, S A
1995-01-01
New and used cellulosic air filters for HVAC systems including those treated with antimicrobials were suspended in vessels with a range of relative humidities (55-99%) and containing non-sterile potting soil which stimulates fungal growth. Most filters yielded fungi prior to suspension in the chambers but only two of 14 nontreated filters demonstrated fungal colonization following use in HVAC systems. Filters treated with antimicrobials, particularly a phosphated amine complex, demonstrated markedly less fungal colonization than nontreated filters. In comparison with nontreated cellulosic filters, fungal colonization of antimicrobial-treated cellulosic filters was selective and delayed.
Realisation of low-voltage square-root-domain all-pass filters
Directory of Open Access Journals (Sweden)
Farooq A. Khanday
2013-10-01
Full Text Available Novel l ow-voltage first-order and second-order square-root-domain all-pass filters derived systematically by means of transfer function decomposition and state -space synthesis techniques are proposed. The employment of only a few geometric-mean cells and grounded capacitors permits the circuits to absorb shunt parasitic capacitances, which is desirable for production in monolithic form . The circuits enjoy the features of electronic adjustment of frequency characteristics, wider dynamic range and low-voltage environment operation. The filters are employed to design high-order all-pass filters using cascade approach. First-order low-pass and second-order band-pass filters, being the inherited building blocks of the proposed low-order all-pass filters are also discussed. The behaviour of the filters is evaluated through simulations using Taiwan semiconductor manufacturing company 0.25 μm level-3 complementary metal oxide semiconductor process parameters, where the most important performance factors are considered.
Spatial Frequency Requirements and Gaze Strategy in Visual-Only and Audiovisual Speech Perception
Wilson, Amanda H.; Alsius, Agnès; Parè, Martin; Munhall, Kevin G.
2016-01-01
Purpose: The aim of this article is to examine the effects of visual image degradation on performance and gaze behavior in audiovisual and visual-only speech perception tasks. Method: We presented vowel-consonant-vowel utterances visually filtered at a range of frequencies in visual-only, audiovisual congruent, and audiovisual incongruent…
Hong, Jiasheng; Medina, Francisco; Martiacuten, Ferran
2018-01-01
This book presents and discusses strategies for the design and implementation of common-mode suppressed balanced microwave filters, including, narrowband, wideband, and ultra-wideband filters This book examines differential-mode, or balanced, microwave filters by discussing several implementations of practical realizations of these passive components. Topics covered include selective mode suppression, designs based on distributed and semi-lumped approaches, multilayer technologies, defect ground structures, coupled resonators, metamaterials, interference techniques, and substrate integrated waveguides, among others. Divided into five parts, Balanced Microwave Filters begins with an introduction that presents the fundamentals of balanced lines, circuits, and networks. Part 2 covers balanced transmission lines with common-mode noise suppression, including several types of common-mode filters and the application of such filters to enhance common-mode suppression in balanced bandpass filters. Next, Part 3 exa...